Biomaterials Promote the Regression of Atherosclerotic Plaque by Regulating Cell Behavior

Introduction

The arterial wall comprises intima, media, and adventitia.¹ The intima includes the endothelial layer, where ECs not only shape vascular architecture but also serve as a dynamic interface, regulating the surrounding microenvironment. The media, situated between the intima and adventitia, predominantly comprises smooth muscle cells. The adventitia, composed predominantly of loose connective tissue, houses fibroblasts.² Adverse factors such as hypertension, hyperlipidemia, hyperglycemia, and high shear stress subjects blood vessels to constant strain and injury, fostering an environment conducive to atherosclerosis and accelerating its progression.³

Arteriosclerotic plaques primarily comprise extracellular lipid deposits, foam cells, and their remnants, which amass in the intimal layer to form a lipid- laden necrotic core. This core is encapsulated by a fibrous cap, predominantly composed of smooth muscle cells (SMCs) and a collagen-rich matrix.⁴ Plaque development is a gradual, multi-decade process.^5–7 It begins with endothelial dysfunction, triggering an inflammatory cascade that progresses to macrophage lipid metabolism imbalance and impaired autophagy. Insufficient clearance of apoptotic cells further expands the necrotic core and thins the fibrous cap as SMCs undergo phenotypic switching. These changes ultimately culminate in plaque rupture and thrombosis.⁸

ECs are especially vulnerable to risk factors including hypertension, dyslipidemia, diabetes mellitus, and tobacco use.⁹ Damage or abnormal apoptosis of ECs significantly increases vascular wall permeability, promoting the infiltration and retention of low-density lipoprotein (LDL). In the initial phases, chemokines recruit neutrophils to predisposed regions.¹⁰ Neutrophils amplify vascular inflammation by releasing vesicles and are further stimulated by cholesterol crystals to generate neutrophil extracellular traps (NETs), which activate macrophages to secrete pro-inflammatory cytokines.¹¹

Macrophages, responding to the local microenvironment, undergo activation to meet functional demands for proliferation, cytokine production, and phagocytosis. Inflammatory macrophages exhibit a strong capacity for ox-LDL phagocytosis, transforming into foam cells—a critical component of atherosclerotic plaques.¹² However, excessive cholesterol accumulation disrupts lipid uptake and efflux, triggering a cascade of inflammatory signaling, culminating in apoptosis.¹³ Intracellular lipid overload marks a turning point, upregulating autophagic pathways to restore homeostasis through enhanced lipid catabolism.¹⁴ Yet, significant lipid accumulation impairs macrophage autophagy within atherosclerotic regions, worsening dysfunction.¹⁵ In advanced plaque stages, macrophage phagocytic dysfunction prevents the efficient clearance of dying foam cells, which contribute to plaque complexity and instability.¹⁶

Foam cells also stimulate vascular smooth muscle cells (VSMCs) to migrate from the media to the intima and proliferate by secreting growth factors and cytokines. VSMCs, in turn, produce large amounts of collagen, forming a fibrous cap around the lipid core. However, in advanced atherosclerosis, VSMC phenotypic changes reduce extracellular matrix synthesis while increasing degradation, notably of collagen, leading to a thinner fibrous cap and heightened plaque instability.^17,18

Plaque rupture often serves as the primary event triggering thrombus formation.¹⁹ When rupture occurs, the plaque’s thrombotic substrates, such as tissue factors and fibrous collagen, become exposed. These substrates activate coagulation cascades and platelets, respectively, resulting in mixed thrombus formation.^7,20 Thereby, preventing plaque progression and promoting the regression of atherosclerotic plaques are pivotal strategies for reducing cardiovascular and cerebrovascular adverse events.

Traditional approaches, such as HMG-CoA reductase inhibitors (statins) and PCSK9 inhibitors, primarily focus on lowering LDL cholesterol levels in plasma.^21,22 For instance, statins exhibit limited lipid-lowering potency and may even demonstrate insensitivity or intolerance in certain patients.^23–25 The administration of high doses may induce severe adverse reactions, thereby rendering it challenging to fulfill the lipid-lowering demands pertinent to cardiovascular and cerebrovascular diseases.^26,27 One of the primary causes of these adverse effects lies in their limited selectivity of action. Free drugs typically exhibit feeble affinity for target tissues, leading to inadequate concentration at the site of the lesion and dissemination to other normal tissues, consequently compromising efficacy and inducing side effects.²⁸ Researches have demonstrated that targeted delivery via biomaterials markedly impedes the progression of atherosclerotic plaque in comparison to free statins drug therapy.^29–31 Although PCSK9 inhibitors possess superior lipid-lowering intensity compared to statins, their anti-inflammatory and plaque-stabilizing properties are relatively modest, serving solely as adjunctive therapy to statins.³² For the long-term management of cardiovascular and cerebrovascular diseases, these medications demonstrate no therapeutic efficacy against pre-established atherosclerotic plaques, thereby failing to satisfy the clinical imperative for reversing or mitigating such lesions.

Building upon current lipid-lowering therapies, biomaterials are capable of reversing or slowing the progression of atherosclerosis through several mechanisms. First, surface modification or functionalization of biomaterials enables targeted delivery to plaques or macrophages, thereby enhancing local drug concentrations and reducing systemic side effects.^33,34 Second, When combined with zinc ions, epigallocatechin gallate, and CpG, biomaterials can inhibit the progression of atherosclerosis through a synergistic mechanism that enhances cell efferocytosis, promotes lipid degradation, and facilitates cholesterol efflux.³⁵ Furthermore, by modulating the plaque microenvironment and regulating the oxidative stress of ECs and macrophage polarization, biomaterials hold the potential to induce regression of atherosclerotic plaques.

Existing reviews predominantly concentrate on the rational design of nanomaterials for the purpose of achieving precise diagnostic and therapeutic outcomes. For example, Yang et al comprehensively explored the advancements of dual-targeting nanoparticle strategies in atherosclerosis therapy and underscored the potential of these strategies to overcome the limitations associated with single-targeting methods by categorizing the dual-targeting strategies into four types: purely ligand-based systems, combinations of targeting ligands with cell-penetrating peptides, stimulus-responsive moieties, or nanobiomimetic technology.³⁶ In addition, Cheng et al summarized the advancements in nanomedicine for atherosclerosis diagnosis and therapy, focusing on the design of nanomaterials—including inorganic, organic, and biomimetic types—for targeted imaging, drug delivery, and combined theranostic strategies. It highlighted applications in multimodal imaging (eg, magnetic resonance imaging, computed tomography imaging, fluorescence) and innovative therapies such as phototherapy, sonodynamic therapy, immunotherapy, and gas therapy.³⁷ However, the aforementioned studies have overlooked the pathophysiological mechanisms of atherosclerotic plaques, thereby failing to achieve optimal integration with biomaterials and consequently impeding the foundation for subsequent clinical translation of these materials.

This review explores the cellular and molecular mechanisms that underpin the formation and progression of atherosclerotic plaques, shedding light on the complexities inherent in these processes. It highlights the role of biomaterials in restoring EC function, inhibiting neutrophil activation, modulating macrophage behavior, and preventing the pathological transformation of smooth muscle cells. These advancements highlight the revolutionary potential of biomaterials in combating atherosclerosis. Scheme 1 visually illustrates these interconnected mechanisms, providing a comprehensive overview. Furthermore, we explore emerging opportunities for biomaterials in promoting plaque regression while addressing current challenges and bottlenecks, offering a roadmap for future advancements in this field.

Scheme 1 Targeted therapeutic approaches for atherosclerotic plaque employing biomaterials.

Biomaterials Promote the Regression of Atherosclerotic Plaque by Promoting the Functional Recovery of Endothelial Cells

The vascular endothelium assumes a pivotal role in preserving vascular homeostasis. Beyond serving as a selective barrier, ECs facilitate the efficient exchange of gases and nutrients with underlying tissues.³⁸ ECs are highly responsive to chemical and biomechanical cues, secreting regulatory factors that finely modulate vascular tension, SMCs proliferation and migration, immune cell adherence, thrombosis resistance, and inflammatory responses.³⁹ However, oxidative stress, ferroptosis, and endothelial-to-mesenchymal transition (EndoMT) are key contributors to endothelial dysfunction. Such dysfunction disrupts normal vasodilation and nitric oxide (NO) secretion, exacerbates oxidative stress and inflammation, ultimately driving disease progression.⁴⁰ Therefore, effective strategies to restore endothelial integrity and barrier function—by attenuating oxidative stress, inhibiting ferroptosis, and reversing EndoMT—are crucial for delaying or potentially reversing atherosclerotic progression.

Modulation of Endothelial Cell Oxidative Stress

Oxidative stress reflects an imbalance between free radical generation and antioxidant defenses, occurring when tissues or cells are exposed to harmful stimuli. When the rate of oxidation exceeds the capacity for oxidant clearance, reactive oxygen species (ROS) accumulate, causing cytotoxicity and tissue damage.⁴¹ Extensive studies have demonstrated the pivotal role of oxidative stress in initiating and progressing atherosclerosis and their related complications.

External stimuli activate ECs, triggering a molecular cascade that includes upregulating chemokines, cytokines, and adhesion molecules. This process facilitates immune cell migration and infiltration from the bloodstream. A key transition in EC activation occurs when the signaling mechanisms shift from maintaining NO homeostasis to producing excessive ROS. This ROS surge triggers the nuclear factor kappa B (NF-κB) signaling pathway, fostering EC activation, increasing vascular permeability, and enhancing the accumulation of macrophages and lipids within the arterial intima. These events culminate in the formation of foam cells and fatty streaks, marking the initial phases of atherosclerosis.^42,43 Within the vascular microenvironment of atherosclerosis, ROS are generated through multiple mechanisms, encompassing mitochondrial electron transport chain leakage, xanthine oxidase activation, and endothelial NO synthase uncoupling.⁴⁴ These mechanisms collectively create a complex network that accelerates cardiovascular and cerebrovascular disease progression, driving significant deviations from physiological homeostasis.

Given this context, reducing excess ROS and alleviating oxidative stress in ECs have emerged as promising strategies for mitigating early atherosclerosis. Luo et al designed LLC nanoparticles with a cascade inhibition mechanism targeting ROS in plaques to treat atherosclerosis. Low molecular weight heparin (LMWH) and lipoic acid (LA), both clinically validated, were selected to minimize potential toxicity from unknown carrier materials. LMWH formed the micelle shell, targeting P-selectin overexpressed on plaque ECs and blocking monocyte adhesion to vascular ECs. LA formed the micelle core, effectively scavenging excess ROS, facilitating curcumin release, mitigating oxidative stress, and suppressing inflammation.⁴⁵

Similarly, Li et al developed a ROS-responsive biomimetic nanocomposite for targeted atherosclerotic treatment (Figure 1). The nanocomposite extends blood circulation time and enhances targeting precision by fusing with macrophage membranes. Through its unique thioketal system, this platform achieves selective targeting of ROS-enriched atherosclerotic plaques, enabling intelligently controlled release of Geniposide and Emodin. Research demonstrates that the nanocomposite restores normal EC function and suppresses the aberrant expression of adhesion molecules on endothelial surfaces by localizing and reducing ROS concentrations. These findings not only deepen understanding of ROS’s role in atherosclerosis but also provide a foundation for devising effective therapeutic strategies.⁴⁶

Figure 1 TK-MLP@(GP+EM) NPs facilitate plaque regression by restoring endothelial cell functionality. (A) Schematic representation of the synthesis of TK-MLP@(GP+EM) NPs. (B) Evaluation of infusion efficiency for Liposome NPs and [LP+Mø] m. DiI (565 nm) fluorescence resurgence indicated the amalgamation of Liposome NPs and [LP+Mø] m. (C) Ultrastructural analysis of mitochondria in HUVECs using transmission electron microscopy, with red arrows denoting distinct mitochondrial states (The black dashed rectangle outlines the mitochondrial ultrastructure within HUVECs). (D) Assessment of mitochondrial membrane potential via JC-1 staining. (E) Aortic root cross-sections stained with dihydroethidium to determine the redox status, followed by quantitative assessment of DHE mean fluorescence intensity (n = 3; ###P < 0.001 vs. the Control. ***P < 0.001 vs. the Model). Reproduced under terms of the CC-BY license.46 Copyright 2024, Springer Nature. Abbreviations: EM, Emodin; GP, Geniposide; HUVECs, human umbilical vein endothelial cells; Møm, macrophage cell membranes; ROS, reactive oxygen species. TK, thioketal.

Furthermore, Chen et al engineered a biomimetic platelet membrane-encapsulated polyphenol-cerium dioxide nanozyme complex (SS-CeO₂@PLTM) for atherosclerosis therapy. The study demonstrated that SS-CeO₂@PLTM enhanced lipid metabolism and reduced plaque area in ApoE^−/− mice by alleviating oxidative stress and NF-κB-mediated inflammatory responses. This research marks the first demonstration of the exceptional efficacy of the nanoenzyme complex in targeted atherosclerotic treatment, heralding a paradigm shift in the management of multifactorial cardiovascular and cerebrovascular diseases.⁴⁷

Inhibition of Endothelial Cell Ferroptosis

Oxidative stress and elevated ROS levels accelerate lipid peroxidation and may also induce ferroptosis in ECs, a unique modality of cellular demise that presents a substantial peril to vascular integrity.^48,49 Ferroptosis, an iron-reliant cellular demise pathway caused by aberrant accumulation of peroxidized lipids in cell membranes, has been recognized as a pivotal constituent of the programmed cell death family since its identification by Dixon et al in 2012.⁵⁰ This mechanism is propelled by the peroxidation of phospholipids derived from polyunsaturated fatty acids (PUFAs) and the subsequent formation of lipid hydroperoxides. Lipid peroxidation initiates with the abstraction of a hydrogen atom from PUFA-derived phospholipids within the bilayer, generating a carbon-centered free radical. This radical interacts with molecular oxygen to form a peroxide free radical. Without conversion into lipid peroxides and reduction to alcohols, these radicals initiate secondary reactions, compromising membrane integrity and ultimately culminating in the rupture of organelles and cellular membranes.⁵¹

Ferroptosis is tightly controlled by an enzymatic metabolic system that prevents excessive accumulation of membrane lipid peroxides.⁵² Within this regulatory network, glutathione peroxidase 4 (GPX4) and acyl-CoA synthase long-chain family member 4 (ACSL4) play critical roles as negative and positive regulators, respectively. GPX4, a constituent of the glutathione peroxidase family, suppresses ferroptosis by using reduced glutathione to convert harmful lipid peroxides into benign lipid alcohols.^53,54 ACSL4 catalyzes the conversion of PUFAs into acyl-CoA esters, indirectly promoting lipid peroxide accumulation and accelerating ferroptosis.^55–57 Notably, atherosclerosis progression shows a significant correlation with the ferroptosis pathway, which exacerbates this pathological process by inducing endothelial dysfunction. Consequently, targeting EC ferroptosis has emerged as a critical strategy for mitigating atherosclerosis progression.⁵⁸

Inhibiting ACSL4 activity is a pivotal mechanism for resisting ferroptosis and protecting cells from its harmful effects.^57,59 Berberine (BBR), a natural alkaloid derived from traditional Chinese medicinal herbs, has been identified as a potent ACSL4 inhibitor.⁶⁰ A study by Hong et al demonstrated that BBR not only suppresses ferroptosis but also slows atherosclerosis progression by destabilizing the ACSL4 protein.⁶¹ However, owing to the limited oral bioavailability (below 1%), high aqueous solubility, and swift excretion of BBR, the circulating concentrations of BBR in the bloodstream generally remain low. Consequently, targeted drug delivery systems need to be developed to increase the accumulation of BBR in atherosclerotic plaque and minimize side effects. Wu et al engineered an M2 macrophage- mimicking BBR- encapsulated PLGA nanoparticle drug delivery system (BBR NPs@Man/M2) (Figure 2). Research results indicate that, BBR NPs@Man /M2 reduce inflammation of ECs, facilitate ECs repair and collagen secretion, and uphold vascular stability.⁶² In conclusion, BBR NPs@Man /M2 offers an efficient and secure strategy to inhibit atherosclerosis progression.

Figure 2 Precision-targeted administration of berberine via bionic nanomaterials for the treatment of atherosclerosis. (A) The synthesis of BBR NPs@Man/M2 nanoparticles. (B) Schematic representation illustrating the therapeutic management of atherosclerosis through tail intravenous administration of BBR NPs@Man/M2 nanoparticles. (C) Schematic representation of the anti-atherosclerotic therapeutic mechanism targeting BBR NPs@Man/M2 nanoparticles (The arrow represents the process by which berberine acts on HUVEC cell). (D) Release profiles of berberine from BBR NPs, BBR NPs@M2, and BBR NPs@Man/M2 in 20% PBS at room temperature over 60 hours, measured by spectrophotometry at a wavelength of 345 nm. (E) Serum concentrations of LDL-C and HDL-C in mice following treatment with BBR NPs@Man/M2 (n = 6; **P < 0.01). Reproduced under terms of the CC-BY license.62 Copyright 2024, Elsevier. Abbreviations: ApoE−/−, apolipoprotein E knockout; BBR NPs, berberine polylactic-hydroxylase-polylactide (PLGA) nanoparticles (NPs); HDL-C, high-density lipoprotein Cholesterol; HUVEC, Human Umbilical Vein Endothelial Cells; IL-4, interleukin-4; LDL-C, low-density lipoprotein cholesterol; Man, mannose; VEGF, Vascular endothelial growth factor.

Ferrostatin-1, a ferroptosis inhibitor, was demonstrated to prevent iron accumulation, lipid peroxidation, and restore GPX4 expression in HFD-fed ApoE^−/− mice.⁵⁸ Thus, Feng et al developed an M2 exosome (E)/liposome (L) nanohybrid targeting biomimetic plaques, co-encapsulated with atorvastatin (A) and ferritin-1 (F) (designated EL@AF). This nanocomposite demonstrated potent anti-atherosclerotic effects both in vitro and in vivo, combining plaque targeting, anti-inflammatory activity, cholesterol efflux, and ferroptosis inhibition.⁶³

Promotion of Reverse Endothelial-Mesenchymal Transition in Endothelial Cells

EndoMT refers to the process whereby ECs relinquish endothelial-specific markers and adopt mesenchymal cell properties in reaction to diverse stimuli, encompassing cytokines, growth factors, oxidative stress, and inflammatory signals. This transition results in marked changes in EC polarity, morphology, and functionality.⁶⁴ Mechanistically, the EndoMT process is governed by several key transcription factors, encompassing Snail, Slug, and Twist-related protein 1. In the SMAD-dependent pathway, transforming growth factor-β (TGF-β) assumes the role of a key signaling mediator. Upon engagement with and activating the TGF-β type I/II receptor complex, it initiates a cascade that recruits SMAD2/3 proteins. These proteins form heteromeric complexes with SMAD4, translocate into the nuclear compartment, and promote the transcription of EndoMT-related genes.

Beyond the canonical SMAD pathway, TGF-β signaling activates non-canonical routes, such as the RhoA pathway, which drives myocardin- associated transcription factors to modulate Snail and Slug expression, further influencing EndoMT. TGF-β signaling also reinforces its own activity via the TAK1-mediated pathway, creating a positive feedback loop that enhances the EndoMT process.⁶⁵ Notch signaling, Wnt signaling, and oxidative stress synergistically promote EndoMT by inducing TGF-β expression or augmenting the nuclear accumulation of transcription factors critical to this process.^66,67 This complex regulatory network ensures precise control and timely activation of EndoMT during physiological and pathological conditions, encompassing embryonic development, disease progression, and tissue repair.

During EndoMT, endothelial markers like VE-cadherin and CD31 are downregulated, whereas mesenchymal markers, including alpha-smooth muscle actin (α-SMA), N-cadherin, and calmodulin, are upregulated.⁶⁸ These molecular changes redefine the cellular identity of ECs, profoundly altering their physiological functions. VSMCs between ECs weaken, while the expression of leukocyte adhesion molecules increases, compromising the vascular barrier’s selective permeability. This disruption facilitates inflammatory cell infiltration, thereby exacerbating endothelial dysfunction. Research has further established EndoMT’s pivotal role in promoting neointimal hyperplasia and transforming ECs into pro-inflammatory and pro-coagulant phenotypes.⁶⁹ Notably, EndoMT is more prevalent in complex atherosclerotic plaque lesions than in fibrocalcified plaques and correlates inversely with fibrous cap thickness.⁷⁰ These discoveries underscore the significant contribution of EndoMT in atherosclerosis progression.

Given its pathological implications, reversing or inhibiting EndoMT has become a promising therapeutic approach for atherosclerosis management. Liu et al have proposed an innovative melanin nanoparticle system targeting N-cadherin, which facilitates the reversion of mesenchymal-like ECs to their original endothelial phenotype through a “reverse EndoMT” strategy (Figure 3). This approach not only restores endothelial barrier integrity but also reduces leukocyte adhesion and migration, offering a potential early intervention for atherosclerotic plaques. Mechanistically, the nanoparticles modulate the N-cadherin-dependent RhoA signaling pathway, suppressing key transcription factors like Snail and Slug, which are essential for maintaining the mesenchymal-like phenotype. This reverse transformation highlights the promise of nanotechnology in biomedical applications and provides novel avenues for managing unstable plaques.⁷¹

Figure 3 N-Cadherin-conjugated melanin nanoparticles inhibit EndoMT, attenuating atherogenesis. (A) Schematic representation of “Reversed EndoMT” in endothelial cells mediated by nanoparticles (The combination of a dashed line and a red “X” symbolically denotes “Under physiological quiescent conditions, endothelial cells maintain intercellular tight junctions that functionally impede leukocyte and cancer cell cellular adhesion, recruitment, and trans-endothelial migration”). (B) Schematic depiction of the extraction of natural MNPs from cuttlefish ink and surface functionalization of MNPs with N-cadherin antibody. (C) zeta potential measurements of bare MNPs, MNPs@BSA, MNPs@PA/BSA, and MNPs@PA/BSA@NcadAb in H2O. (D) Statistical analysis of stress fiber count from dSTORM imaging (n = 5; ***P < 0.001, ns, no significant difference) (HUVEC: G1: Untreated, G2: IL-1β, G3: IL-1β+MNPs@N-cadAb; HDMVEC: G1: Untreated, G2: TGF-β, G3: TGF-β+MNPs@N-cadAb). (E) Statistical analysis of actin orientation of individual cells based on dSTORM images. Reproduced with permission.71 Copyright 2024, American Chemical Society. Abbreviations: EndoMT, Endothelial−mesenchymal transition; HDMVEC, human dermal microvascular endothelial cells; MNPs, melanin nanoparticles; R-EndoMT, Reversed endothelial−mesenchymal transition.

Additionally, Chen et al devised a novel therapeutic approach utilizing engineered extracellular vesicles (EVs) sourced from bone marrow mesenchymal stem cells (BMSCs) to target and reverse EndoMT in vascular ECs implicated in atherosclerosis.⁷² The engineered EVs are modified through two modules: functionality and targeting. In the functional protein module, silent information regulator 2-related enzyme 1 (SIRT1) protein overexpression in BMSCs is achieved by infecting with a recombinant SIRT1 adenovirus. In the targeting module, cholesterol-modified aptamers of vascular endothelial growth factor, a protein uniquely expressed in vascular ECs, are conjugated to the engineered EVs to ensure selective targeting of vascular ECs. Upon targeted accumulation adjacent to ECs, the engineered EVs undergo internalization, releasing the loaded SIRT1 into the cells. Subsequently, SIRT1 effectively reverses EndoMT in vascular ECs through the activation of nuclear factor-erythroid 2-related factor 2 and modulating the oxidative stress response.

Biomaterials Promote the Regression of Atherosclerotic Plaque by Inhibiting the Activation of Neutrophils

In the early stages of atherosclerosis, platelet-derived chemokine ligand 5 acts as a signaling molecule to activate neutrophils, which function as immune sentinels. Activated neutrophils rapidly adhere to arterial ECs, initiating the inflammatory response. Concurrently, microvesicles secreted by white blood cells trigger widespread EC activation, leading to the upregulation of proteases and adhesion molecules. This cascade not only impairs normal EC functionality but also promotes the aggregation of white blood cells within the vascular wall, intensifying local inflammatory responses.

NETs, released upon neutrophil activation, have emerged as pivotal drivers in the complex pathology of atherosclerosis. By attracting and activating immune cells such as monocytes and dendritic cells, NETs trigger a cascade of inflammatory reactions. This process includes the liberation of matrix metalloproteinases, neutrophil elastase (NE), tissue protease G, and other proteases, which exacerbate lesion expansion and compromise plaque stability.^11,73 In advanced stages of atherosclerosis, NETs interacts with VSMCs, inducing their lysis and promoting the formation of vulnerable plaques.⁷⁴ Therefore, targeted therapeutic strategies aimed at inhibiting neutrophil-derived microbubbles and NETs are poised to play a critical role in stabilizing high-risk plaques, addressing a key driver of cardiovascular disease at its origin.

Neutrophils play a pivotal role in the development of atherosclerosis, amplifying vascular inflammation and disease progression through the release of miR-155-enriched microbubbles into vulnerable regions.⁷⁵ miR-155, a key regulatory molecule, suppresses the expression of BCL6, a negative regulator within the NF-κB pathway, thereby accelerating disease progression. Notably, the absence of miR-155 mitigates the development of advanced atherosclerotic plaques by relieving BCL6 inhibition, underscoring the therapeutic potential of miR-155 suppression.⁷⁶

To navigate this complex molecular network, researchers have explored antisense oligonucleotides (ASOs) as innovative gene-silencing tools for treating human diseases. Liu et al designed a zeolite imidazolate framework-8 (ZIF-8) nanocarrier encapsulated in neutrophil membranes (AM@ZIF@NM) to deliver ASOs targeting miR-155 (anti-miR-155) to ECs in atherosclerotic plaques (Figure 4). This system exploits the specific interaction between CD18 on neutrophil membranes and intercellular adhesion molecule-1 on ECs, ensuring precise nanoparticle targeting. ZIF-8 serves as the “core” of the nanocarrier, providing both high drug-loading capacity and efficient ASO release within cells, while circumventing lysosomal degradation. This innovative delivery mechanism successfully downregulated miR-155 expression, restored BCL6 levels, and impeded the aberrant activation of the NF-κB pathway. The resulting suppression of inflammatory reactions in atherosclerotic lesions highlights the potential of this novel therapeutic strategy.⁷⁷

Figure 4 Neutrophil-membrane-coated biomineralized metal-organic framework nanoparticles attenuate atherosclerosis via targeted gene silencing. (A) Schematic representation of antiatherosclerosis targeted therapy by using neutrophil-membrane-coated anti-miR-155- loaded ZIF-8 nanoparticles (AM@ZIF@NM NPs) (The upward arrow represents an increase in content; The downward arrow represents a decrease in content). (B) UV–vis absorbance spectra of AM@ZIF NPs and pure ZIF-8 (ZIF) NPs. (C) Release profiles of anti-miR-155 from AM@ZIF@NM NPs at pH 7.4 and 5.5 over time. (D) Quantitative analysis of collagen content (n = 3–5; *P < 0.05, ****P < 0.0001). (E) Exemplary images of aorta root segments stained with H&E. (F) Quantitative assessment of necrotic areas (n = 3–5; **P < 0.01, ****P < 0.0001). Reproduced with permission.77 Copyright 2023, American Chemical Society. Abbreviations: ICAM-1, intercellular adhesion molecule-1; ZIF-8, zeolitic imidazolate framework-8.

NETs, complex structures rich in genetic material released by activated neutrophils, are critical in the advancement of atherosclerosis and the formation of vulnerable plaques.^78,79 Recent research has identified NETs as major contributors to both venous and arterial thrombosis.⁸⁰ Among their components, NE plays a pivotal role, serving as a key mediator of NET biological activity and function.^81,82 These findings highlight the therapeutic potential of precisely targeting neutrophils and NE to impede atherosclerotic progression. Sivelestat (SVT), a second-generation, highly specific competitive antagonist of NE, has shown promise in this context due to its targeted efficacy. Shi et al developed a liposomal platform (cRGD SVT Lipo) with dual capabilities: plaque targeting and a neutrophil “free-riding” function (Figure 5). This innovative system not only navigates to atherosclerotic plaques but also delivers SVT to the site of action. By effectively inhibiting NE activity within plaques, it significantly reduces plaque area, stabilizes plaque structure, and halts atherosclerotic progression.⁸³

Figure 5 A liposome targeting atherosclerotic plaques, inhibiting elastase, and leveraging neutrophil hitchhiking for therapeutic intervention. (A) Schematic representation of cRGD-SVT-Lipo, utilizing cRGD-integrin αvβ3 interaction to inhibit neutrophil elastase in atherosclerotic plaques. (B) Particle size variation of cRGD-SVT-Lipo upon incubation with PBS or 10% FBS. (C) E.V.G staining of the aortic root segments following various therapeutic interventions (From left to right are Saline, SVT Solution, SVT-Lipo, and cRGD-SVT-Lipo, respectively) (Scale bar = 200 μm). (D) Quantitative assessment of the percentage of plaque area throughout the entire aorta (left) (n = 5–6; *P < 0.05, **P < 0.01, ***P < 0.001). (Scale bar = 200 μm). Quantitative evaluation of neutrophil elastin area within plaque(right) (n = 5–6; *P < 0.05, **P < 0.01, ****P < 0.0001). (E) Oil Red O staining of plaque regions throughout the entire aorta (Scale bar = 200 μm). Reproduced with permission.83 Copyright 2024, Elsevier Ltd. Abbreviations: FBS, Fetal bovine serum; NETs, Neutrophil extracellular traps; PBS, phosphate buffered saline; SVT, Sivelestat.

Biomaterials Promote Atherosclerosis Plaque Regression by Regulating Macrophage Cell Behavior

Macrophages assume a pivotal position throughout the entire lifecycle of atherosclerosis plaque.⁸⁴ Their profound heterogeneity and plasticity within plaques critically influence the dynamic microenvironment, driving inflammatory cascades, foam cell formation, and necrotic cell clearance. Biomaterials are gaining growing acknowledgment for their pivotal function in modulating macrophage activation and polarization, foam cell development, autophagy and endocytosis. A comprehensive comprehension of these mechanisms is imperative for advancing therapeutic strategies against atherosclerosis plaque.

Regulation of Macrophage Activation and Polarization

Atherosclerosis is fundamentally a chronic inflammatory condition. The mobilization and activation of macrophages within the arterial wall initiate a persistent inflammatory response. These cells differentiate into pro-inflammatory M1 or anti-inflammatory M2 phenotypes, with their functional behavior determined by microenvironmental signals.⁸⁵ Maintaining an equilibrium between M1 and M2 macrophages is vital for arterial wall homeostasis. Disturbance of this equilibrium instigates unrestrained inflammation, which expedites the progression of atherosclerosis.

The quantity and polarization state of macrophages strongly influence the rate and stability of atherosclerotic plaque progression. At lesion sites, macrophages not only proliferate but also exacerbate inflammation through cytokine secretion, perpetuating a harmful feedback loop.⁸⁶ Targeting macrophage hyperproliferation has emerged as a promising therapeutic approach. Boada et al described a biomimetic drug delivery system that precisely targets macrophages in aortic tissue and efficiently delivers the potent inhibitor rapamycin (Figure 6). This approach successfully curtailed macrophage proliferation and slowed atherosclerosis progression, offering a novel avenue for the treatment of arteriosclerosis plaque.⁸⁷

Figure 6 Biomimetic nanoparticles laden with rapamycin mitigate vascular inflammation. (A) Schematic representation of vascular inflammation reduction through a biomimetic drug delivery mechanism (The upward arrow represents an increase in content; The downward arrow represents a decrease in content). (B) Flow cytometric assessment of leukocyte and macrophage subpopulations. (C) ApoE−/− mice subjected to treatment with rapamycin leukosomes exhibit reduction in proliferating macrophage cohort (*P = 0.0180). (D) Vessel cross-section schematic illustrating vessel morphology and atherosclerotic characteristics in ApoE−/− mice model. (E) Quantification analysis of plaque area percentage using an automated algorithm (*P = 0.035). Reproduced under terms of the CC-BY license.87 Copyright 2019, Wolters Kluwer Health. Abbreviations: I-CAM1, intercellular adhesion molecule 1; L/D, leukocyte/debris; MCP-1, monocyte chemoattractant protein 1; mTOR, mammalian target of rapamycin; TNF, tumor necrosis factor; V-CAM1, vascular cell adhesion molecular 1.

Atherosclerotic plaque progression is characterized by an imbalance between two macrophage phenotypes, wherein M1 macrophages assume a crucial influence on disease advancement.⁸⁸ Recent research highlights that TRIM24, an E3 ligase associated with the acetyltransferase CREB-binding protein (CBP), facilitates the acetylation of signal transducer and activator of transcription 6 (Stat6) by catalyzing CBP ubiquitination at Lys119, thereby enhancing CBP’s binding to Stat6.⁸⁸ CBP subsequently acetylates STAT6, suppressing its transcriptional activity and inhibiting M2 macrophage polarization.⁸⁹ Consequently, targeting TRIM24 offers a potential strategy for promoting M2 polarization. Proteolysis-targeting chimera (PROTAC) technology has surfaced as an innovative approach for selectively breaking down target proteins. Yet, the constrained bioavailability of PROTAC reagents impede their utilization in addressing atherosclerotic plaques. Huang et al introduced a biomimetic PROTAC therapy that targets TRIM24 degradation by encapsulating M2 macrophage membranes onto PLGA nanoparticles loaded with a TRIM24-degrading PROTAC agent (dTRIM24) (Membranes derived from M2 macrophages/PLGA/dTRIM4, MELT). The innovative approach facilitated M2 polarization by enabling MELT-specific interactions with M1 macrophages, significantly reducing atherosclerotic plaque accumulation and plaque formation.⁹⁰

Docosahexaenoic acid (DHA, 22:6n-3), an omega-3 PUFA with anti-inflammatory and antioxidant properties, is gaining recognition as a promising therapeutic agent for atherosclerosis. Chong et al developed an injectable DHA liposome nanoformulation for targeted plaque therapy. These liposomes preferentially accumulate in macrophages within atherosclerotic lesions after intravenous administration, further promoting the polarization of macrophages toward the anti-inflammatory M2 phenotype. Plaque composition analysis revealed that DHA liposomes reduced macrophage infiltration and lipid accumulation while increasing collagen content, thereby enhancing plaque stability. DHA liposomes represent a promising therapeutic strategy for stabilizing atherosclerotic plaques and slowing disease progression.⁹¹

In both atherosclerosis patients and corresponding animal models, elevated circulating lipopolysaccharide (LPS) levels strongly correlate with disease severity. LPS is a critical driver of macrophage polarization toward the pro-inflammatory M1 phenotype, amplifying inflammation and accelerating atherosclerosis progression.⁹² As such, targeting circulating LPS presents a compelling therapeutic opportunity for atherosclerosis treatment. Small molecular compounds, exemplified by polymyxin B (PMB), have been proposed as the most suitable candidates for the adsorption of LPS. Nevertheless, PMB readily binds to muscle tissue, consequently resulting in a swift decline in its serum concentration. Furthermore, the pronounced nephrotoxicity and nerve block adverse effects of PMB significantly constrain its clinical utilization.⁹³ In this context, Liu et al devised an innovative adsorption strategy by covalently coupling PMB to PEGylated liposomes (PLPs), leveraging PMB’s specific interaction with LPS (Figure 7). In vitro investigations reveal that the PLP complex effectively adsorbs LPS, inhibiting macrophage polarization toward the pro-inflammatory M1 phenotype and reducing foam cell formation. Complementary in vivo studies further highlight the therapeutic efficacy of PLP therapy: it lowers serum concentrations of LPS and pro-inflammatory cytokines, decreases M1 macrophage prevalence in atherosclerotic plaques, enhances plaque stability, and reduces arterial plaque burden, thereby significantly suppressing atherosclerosis progression. This study not only reaffirms the pivotal role of circulating LPS as a therapeutic target for atherosclerosis but also introduces a promising avenue for clinical treatment.⁹⁴

Figure 7 LPS adsorption and inflammation mitigation via polymyxin B- functionalized liposomes for atherosclerosis therapy. (A) Schematic depiction of PLPs preparation. (B) The mechanism driving the therapeutic effects of PLPs in atherosclerosis (The upward arrow represents an increase in content; The downward arrow represents a decrease in content). (C) Stability of LPs and PLPs demonstrated by particle size following storage in deionized water at 4°C for one week. (D) Quantitative assessment of plaque areas within the entire aortic intima (n = 5 or 6; ***P < 0.001, ns, no significant difference). (E) Semiquantitative evaluation of aorta root sections stained with Masson’s trichrome (n = 5 or 6; **P < 0.01, ***P < 0.001). Reproduced under terms of the CC-BY license.94 Copyright 2023, Elsevier. Abbreviations: LPS, lipopolysaccharide; Ox-LDL, Oxidized low density lipoprotein; PLPs, PEGylated liposomes; TLR-4, toll-like receptor-4.

Modulation of Macrophage Lipid Metabolism

Lipid homeostasis is critical to foam cell formation,^95,96 governed by complex regulatory mechanisms controlling cholesterol uptake and efflux.⁹⁷ Macrophages internalize ox-LDL through scavenger receptors, degrading it through lysosomal acidic lipase (LAL) into free cholesterol (FC) and fatty acids. Excessive FC accumulation in the ER triggers acyl-CoA acyltransferase-mediated re-esterification into cholesterol esters (CE), leading to cytoplasmic lipid droplet formation. To counterbalance cholesterol overload, macrophages activate neutral cholesterol ester hydrolase, hydrolyzing CE back into FC to enhance efflux.⁹⁸ This process activates the liver X receptor (LXR)/retinoid X receptor heterodimer, upregulating ABCA1 and ABCG1. ABCA1 mediates the transfer of FC and phospholipids to extracellular apolipoprotein A1, initiating high-density lipoprotein (HDL) formation,^99,100 while ABCG1 facilitates FC transfer to mature HDL particles. However, excessive FC accumulation induce cholesterol crystal formation in lysosomes, activate NLRP3 inflammasomes, and cause ER stress, culminating in macrophage apoptosis or death.^101,102 Thus, strategies targeting lipid uptake inhibition and enhancing cholesterol efflux are crucial for curtailing foam cell formation and mitigating atherosclerosis progression.

Inhibition of Lipid Uptake

Scavenger receptor-A (SR-A), a 77 kDa glycoprotein belonging to the Class A scavenger receptor family, plays a central role in lipid metabolism and atherosclerosis progression via its interaction with various ligands.¹⁰³ SR-A-mediated ox-LDL internalization by macrophages constitutes a critical mechanism in foam cell formation, an early hallmark of atherosclerosis.¹⁰⁴

Studies in Ldlr^−/− mice reveal that P2Y6 expression is upregulated during atherosclerosis, and its absence reduces both plaque formation and inflammation.¹⁰⁵ Consequently, the P2Y6 receptor (P2Y6R) is identified as a target in atherosclerotic plaque treatment.¹⁰⁶ The deficiency of P2Y6R in macrophages disrupts the activation of the phospholipase C β (PLCβ)/store-operated calcium entry (SOCE) signaling pathway, resulting in diminished SR-A expression and impaired ox-LDL internalization. Simultaneously, the absence of P2Y6R also diminishes the binding of SR-A to calreticulin (CALR), resulting in a decreased expression of SR-A and a reduction in cholesterol deposition within macrophages. These findings underscore the pivotal role of macrophage P2Y6R deficiency in mitigating ox-LDL internalization, inhibiting foam cell formation, and alleviating atherosclerosis progression.

Importantly, thiamine pyrophosphate (TPP), a potent P2Y6R antagonist, demonstrated therapeutic efficacy against atherosclerosis in experimental models by exhibiting high binding affinity and robust antagonistic activity.¹⁰⁷ By means of, Zeng et al developed a nanoparticle zeolitic imidazolate framework-8 (ZIF-8) @TPP for atherosclerosis therapy through controlled release of TPP (Figure 8). Their findings demonstrated a marked enhancement in the anti-atherosclerotic efficacy of TPP upon incorporation with the prototypical metal-organic framework, ZIF-8.¹⁰⁸ Further mechanistic investigations unveiled that ZIF-8@TPP potentially diminishes lipid phagocytosis and lipid metabolism in macrophages through the PI3K/AKT/macrophage scavenger receptor 1 pathway. This study highlights the therapeutic promise of targeting P2Y6R and sets the stage for innovative atherosclerosis treatments.

Figure 8 Nanoplatforms predicated on metal-organic frameworks for synergistic therapeutic intervention against atherosclerosis. (A) Illustrative schematic delineating the fabrication procedure of ZIF-8@TPP and its mechanisms in treating atherosclerosis (The downward arrow represents a decrease in content). (B) Correlation heatmap depicting Pearson’s correlations between control and RAW264.7 cells subjected to ZIF-8@TPP treatment. (C) Semi-quantitative analysis of Dil-Ox-LDL engulfed by RAW264.7 cells pre-incubated with ZIF-8@TPP for 24 h (n = 4; ***P < 0.001). (D) Semi-quantitative evaluation of proteins within the PI3K/AKT signaling pathway in RAW264.7 cells subjected to ZIF-8@TPP treatment (n = 4; *P < 0.05, **P < 0.01, ***P < 0.001). Reproduced with permission.108 Copyright 2025, The Royal Society of Chemistry. Abbreviations: LDL, low-density lipoprotein; MSR1, macrophage scavenger receptor 1; PI3K/AKT, phosphoinositide 3-kinase/ protein kinase B; TPP, thiamine pyrophosphate; ZIF-8, zeolitic imidazolate framework-8.

Additionally, Chunta et al synthesized a hybrid aptamer molecularly imprinted polymer nanoparticle, termed AP-MIP NP. AP-MIP NP binds to the surface of ox-LDL, thereby restricting its interaction with lectin-like ox-LDL receptor-1 and cluster of differentiation 36 scavenger receptors, reducing ox-LDL uptake by macrophages, mitigating foam cell formation, and exhibiting promise as a prospective therapeutic agent for preventing atherosclerosis progression.¹⁰⁹

Promotion of Cholesterol Efflux

Cholesterol efflux serves as a critical determinant in macrophage lipid metabolism.¹¹⁰ However, as lipids accumulate, macrophages transform into foam cells, severely impairing cholesterol efflux and accelerating intracellular cholesterol deposition—a critical factor in atherosclerosis development. ABCA1 and ABCG1 function as key regulators of cholesterol homeostasis, mediating the transfer of surplus lipids from macrophages to HDL and apolipoprotein A-I. This process facilitates reverse cholesterol transport, where cholesterol is mobilized from peripheral tissues to the liver for metabolism and bile excretion.¹¹¹ Reverse cholesterol transport is a fundamental defense mechanism, and its initiation and acceleration are pivotal for maintaining cholesterol balance.^112,113 ABCA1 and ABCG1 constitute direct target genes of LXR, and their expression is modulated by LXR agonists, further emphasizing their therapeutic relevance.

The upregulated expression of ABCA1 and ABCG1 is pivotal in suppressing macrophage-derived foam cell formation, thereby mitigating the incidence and progression of atherosclerosis.¹¹⁴ Wang et al developed a novel therapeutic strategy utilizing a sequentially targeted nanoplatform (HT rHDL) designed to deliver LXR agonists directly into macrophages. After three months of HT rHDL treatment, remarkable therapeutic outcomes were observed, including a 31.47% reduction in plaque area, a 56.0% decrease in lipid accumulation, significant alleviation of inflammatory responses, and notable improvements in plaque stability.¹¹⁵ Similarly, Chen et al introduced an advanced targeted nanoplatform termed LPLCH (Figure 9), which exhibits active plaque-targeting capabilities and pH-sensitive charge conversion properties. Upon reaching the target site, LPLCH releases its LXR agonist cargo, which replaces cholesterol crystals deposited in lysosomes, thereby inducing LXR-mediated upregulation of ABCA1 and ABCG1. This innovative strategy not only clears cholesterol crystals but also inhibits plaque progression through complementary mechanisms. The dual-pathway cholesterol reverse transport mechanism implemented by LPLCH represents a groundbreaking approach to the effective inhibition and resolution of atherosclerosis.¹¹⁶

Figure 9 Cholesterol-targeting nanoplatforms ameliorate atherosclerosis through dual-mode reverse cholesterol transport approach. (A) Schematic representation of the formulation of LPLCH, featuring pH-responsive and cholesterol-encapsulating properties. (B) In vitro release profile of LXR agonists at pH of 7.4, 6.5, and 5.5, both in the presence and absence of cholesterol. (C) Confocal images of free cholesterol and cholesterol crystals within foam cells following various therapeutic interventions. The scale bars were 50 μm. (D) Quantitative analysis of ABCA1 and ABCG1 proteins expression in foam cells following therapeutic intervention (n = 3; *P < 0.05, **P < 0.01; ns, no significant difference). (E) Ex vivo florescent imaging of (Rho) LPLCP and (Rho) LPLCH in aortic tissue was quantified (n = 3; *P < 0.05, **P < 0.01). (F) The quantification of the ratio between the ORO positive area and the total area of the vessel lumen was conducted (n = 6; *P < 0.05, **P < 0.01, ****P < 0.0001; ns, no significant difference). Reproduced with permission.116 Copyright 2023, Wiley-VCH GmbH. Abbreviations: ABCA1, ATP-binding cassette transporters A1; HFD, high-fat diet; LXR, liver X receptor; NCD, normal chow diet.

Methotrexate (MTX) has emerged as a potent modulator of lipid metabolism, augmenting cholesterol efflux by upregulating ABCA1 and cholesterol 27-hydroxylase, consequently mitigating foam cell formation.¹¹⁷ Zhu et al engineered macrophage membrane-cloaked MTX NPs (MM@MTX NPs) that integrate the “homing” targeting capabilities of macrophage membranes with MTX’s therapeutic effects. Additionally, the incorporation of functionalized β-cyclodextrin components significantly enhances cholesterol solubility, while the encapsulated MTX fully exerts its pharmacological effects, effectively inhibiting foam cell formation. This nanoparticle-based approach introduces a promising novel approach for the management of atherosclerosis.¹¹⁸

CD36 promotes macrophages to transform into foam cells by mediating macrophages to phagocytize ox-LDL, which has become a key regulatory hub for the pathogenesis and progress of atherosclerosis.^119,120 Epsins, which bind to CD36, exacerbate this process by accelerating CD36 internalization and recycling, thereby increasing lipid uptake efficiency. Concurrently, Epsins negatively influence cholesterol efflux by promoting the lysosomal degradation of ABCG1, which impairs ABCG1-mediated reverse cholesterol transport pathways and exacerbates intracellular lipid deposition. Notably, targeted knockout of Epsins has been demonstrated to reduce foam cell formation and slow atherosclerosis progression.¹²¹ Cui et al developed a lesion-specific lipid nanoparticle system encapsulating small interfering RNA (siRNA) to target macrophages and inhibit Epsin activity, providing a promising therapeutic approach for advanced atherosclerosis treatment.¹²²

To further enhance therapeutic efficacy, anti-CD36 antibodies were introduced to selectively bind CD36, blocking CD36-mediated phagocytosis of ox-LDL and preventing foam cell formation at its source. Additionally, SRT1720, a specific activator of sirtuin-1, demonstrated multifaceted benefits, including suppression of pro-inflammatory cytokines, promotion of cholesterol reverse transport in macrophages, and stabilization of atherosclerotic plaques, collectively providing robust support for comprehensive atherosclerosis management.^123,124 Wang et al designed a mesoporous silicon-based nano-drug platform with dual diagnostic and therapeutic functions for targeting atherosclerotic lesions. Anti-CD36 was employed as a molecular “key” for macrophage targeting, while SRT1720 was incorporated into the mesoporous structure as an anti-atherosclerotic agent. This innovative approach enabled precise lesion tracking and significantly enhanced SRT1720’s therapeutic efficacy.¹²⁵

Similarly, Zhou et al leveraged the synergistic interaction between artemisinin and proanthocyanidins to develop biomimetic membrane-coated Prussian blue nanoparticles aimed at regulating lipid metabolism in macrophages. This nanocomposite exhibited robust ROS and NO scavenging abilities while inhibiting the NF-κB/NLRP3 inflammatory signaling pathway, thus mitigating abnormal lipid influx into macrophages. Concurrently, it activated the AMP-activated protein kinase (AMPK)/mechanistic target of rapamycin (mTOR)/autophagy signaling pathway, promoting cholesterol efflux and reducing ox-LDL uptake and internalization. Notably, the system enabled inflammation-responsive, controlled drug release within macrophages, enhancing therapeutic outcomes and slowing atherosclerosis progression.¹²⁶

Lipid droplets (LDs), the primary cholesterol reservoir in foam cells, are transported to macrophage lysosomes via autophagy under lipid overload conditions for subsequent metabolic processing.¹²⁷ Research underscored the critical role of lysosomal dysfunction in atherosclerosis pathogenesis and highlighted the potential of inducing lysosomal biogenesis in macrophages as an anti-atherosclerotic strategy.^128–130

Regulation of Macrophage Autophagy

Autophagy, a highly conserved catabolic mechanism, utilizes lysosomal pathways for the degradation and recycling of cytoplasmic components, providing essential substrates for metabolic processes.^131,132 It plays a pivotal role in foam cell formation and lipid metabolism. By promoting cholesterol efflux and LDL degradation, autophagy exhibits anti-atherosclerotic properties.¹³³ However, excessive lipid accumulation overwhelms this defense mechanism, leading to a marked reduction in autophagic activity.¹³⁴ Collectively, macrophage autophagy dysfunction is recognized as a key contributor to atherosclerosis progression, underscoring its therapeutic relevance.¹³⁵

As a principal regulator of the autophagy-lysosome biogenesis pathway, TFEB undergoes nuclear translocation and activation, promoting lysosomal generation and functional restoration.^136,137 Trehalose can promote the dephosphorylation and nuclear translocation of TFEB by inhibiting the mechanistic target of rapamycin complex 1 signaling pathway. Consequently, trehalose exhibits potential for atherosclerosis treatment. However, its hydrophilic nature limits bioavailability and membrane permeability. To surmount these obstacles, Zhong et al developed a trehalose-releasing nanogel (TNG). In vitro studies revealed that macrophage-derived foam cells exhibited reduced LC3 levels and elevated p62 expression compared to controls. Treatment with trehalose and TNG significantly increased the LC3-II/LC3-I ratio while concomitantly reducing the p62/GAPDH ratio and markedly decreasing lipid droplet content. In vivo investigations further revealed that TNG demonstrates superior efficacy in attenuating atherosclerotic plaque formation and upregulating the expression of the autophagy marker LC3. Thus, TNG emerges as an effective trehalose delivery system with potential to reinstate compromised autophagic function, promote lipid efflux, and mitigate plaque formation in atherosclerosis.¹³⁸

Inducing and restoring autophagic activity has surfaced as a promising therapeutic strategy for combating atherosclerosis. Wang et al developed a metal-free nanoenzyme composed of hollow carbon spheres (HCN@DS) (Figure 10).¹³⁹ This nanoenzyme integrates photothermal and photoacoustic imaging with photothermal therapy and a moderate ROS generation strategy, specifically targeting atherosclerotic lesions. Under mild photothermal conditions (temperature <45°C), HCN@DS reactivates autophagy in macrophages and foam cells, mitigating apoptosis, necrosis, and inflammatory responses. Simultaneously, it activates intracellular signaling pathways that enhance cholesterol efflux, thereby promoting plaque stabilization and slowing the progression of atherosclerosis. The ROS generated during this process further enhance autophagic activity in macrophages, amplifying the therapeutic effect. Collectively, the innovative approach, combining targeted delivery, multimodal imaging, and comprehensive treatment, offers significant potential to stabilize plaques and inhibit atherosclerosis progression.

Figure 10 Metal-free nanozyme prevents atherosclerotic plaque destabilization through macrophage autophagy activation. (A) Schematic representation of the synthesis of HCN@DS and the mechanisms underlying atherosclerosis-specific recognition and multimodal imaging-guided therapy (The upward arrow represents an increase in content; The downward arrow represents a decrease in content). (B) High-resolution XPS survey spectra of HCN@DS. (C) CAT-like activities of HCNS and HCN@DS. (D) Apoptosis of Ox-LDL-induced RAW264.7 cells following various therapeutic interventions. (E) Quantitative assessment of ABCA1 proteins (ns, no significant difference). (F) Infrared thermographic depictions of mice injected with PBS or HCN@DS under 1064 nm-laser irradiation. (G) Comparison of aortic arch plaques in mice pre- and post-treatment with HCN@DS+Laser intervention. Reproduced under terms of the CC-BY license.139 Copyright 2024, American Chemical Society. Abbreviations: Ox-LDL, oxidized low-density lipoproteins; XPS, X-ray photoelectron spectroscopy.

Furthermore, Dong et al developed a plaque/macrophage dual-targeting approach for managing atherosclerosis, aiming to concurrently regulate lipid metabolism and macrophage autophagy.³⁰ By co-loading rosuvastatin and hydroxysafflor yellow A into hyaluronic acid (HA)-modified hybrid macrophage membrane liposome NPs, they created biomimetic NPs (designated HA-ML@(H+R) NPs). This work demonstrated that HA-ML@(H+R) NPs facilitate the phenotypic transition of macrophages from M1 to M2, while concurrently promoting autophagy and reducing lipid droplet accumulation through modulation of the PPAR-γ/CD36 signaling pathway, thereby effectively regulating lipid metabolism. Overall, HA-ML@(H+R) NPs not only offer a promising nanotherapy for atherosclerosis but also open new possibilities for the design of combination therapies utilizing different drugs.

Wei et al integrated two driving mechanisms, H₂O₂ and NIR, to design a dual-mode nanomotor powered by both chemical and external stimuli, encompassing functions such as CD36 targeting, ROS clearance, anti-inflammatory effects, and macrophage autophagy induction.¹⁴⁰ Liang et al proposed a polypyridine with intrinsic autophagy-inducing properties for the therapeutic management of atherosclerosis, co-delivering antioxidant enzymes (NeuM@P5c/S/C).¹⁴¹ NeuM@P5c/S/C nanoparticles promote atherosclerotic plaque stabilization through a multi-step mechanism. By utilizing a neutrophil membrane coating, they first achieve inflammation-targeted delivery. Upon reaching the site, the payload P5c facilitates the intracellular delivery of superoxide dismutase and catalase to macrophages, lowering ROS and driving M2 polarization. Additionally, P5c potently induces autophagy (increased LC3-II/I ratio, decreased p62) to alleviate lipid burden. Similar biomaterials that promote macrophage autophagy include Rapa@UiO-66-NH-FAM-IL-1Ra¹⁴² and TN-PdH.¹⁴³

Enhancement of Macrophage Efferocytosis

Efferocytosis, a specialized phagocytic mechanism, is pivotal for sustaining tissue homeostasis and resolving inflammatory processes through the efficient clearance of apoptotic and necrotic cell debris by phagocytes.¹⁴⁴ However, in atherosclerosis, the endocytic capacity of phagocytes is impaired, leading to the aggregation of apoptotic cells and necrotic tissue within plaques. This aggregation expands the necrotic core, intensifies intraplaque inflammation, and significantly heightens the risk of plaque rupture.^145,146 The regulation of efferocytosis involves precise coordination of multiple signaling molecules, including the “Find Me” signal (lysophosphatidylcholine), which attracts phagocytes to apoptotic cells, the “Eat Me” signal (phosphatidylserine, Mer tyrosine kinase, and milk fat globule EGF factor 8), which facilitates recognition and engulfment, and the “Don’t Eat Me” signal (CD47).^147,148

In the atherosclerotic environment, an imbalance between the “Eat Me” and “Don’t Eat Me” signaling systems severely impairs the clearance of apoptotic cells, rendering them “inedible.” This dysfunction results in the aggregation of foam cells and secondary necrosis of apoptotic tissue, exacerbating vascular inflammation and destabilizing plaques.^149,150 Restoring this signaling balance is crucial for enhancing plaque stability and mitigating disease progression, presenting a promising therapeutic avenue for atherosclerosis treatment.

The MER oncogene tyrosine kinase (MerTK) is a critical receptor involved in apoptotic cell clearance.¹⁵¹ In mouse models of advanced atherosclerosis, mutations in the MerTK receptor on phagocytes worsen apoptotic cell accumulation and promote necrotic plaque formation.^152–154 In human carotid plaques, MerTK cleavage demonstrates a strong correlation with necrosis and ischemic symptoms.¹⁵¹ Qiu et al introduced hybrid membrane nanovesicles capable of fusing with receptor cell membranes to enhance MerTK expression in diabetic macrophages. This innovation restored macrophage phagocytic function, enabling efficient apoptotic cell clearance and reducing inflammation caused by their accumulation.¹⁵⁴

Ca²⁺/calmodulin-dependent protein kinase II (CaMKII), a critical serine/threonine kinase, plays a central role in the Ca²⁺ signaling pathway across various cell types. It exists in four subtypes: α, β, δ, and γ, with the γ subtype encoded by the Camk2g gene.¹⁵⁵ Research has revealed that aberrant activation of CaMKII in pathological macrophages substantially promotes the formation of vulnerable plaques in advanced human and murine atherosclerotic lesions.¹⁵⁶ Huang et al developed a siRNA nanoparticle platform targeting the Camk2g gene to silence CaMKII γ activity in macrophages. This approach not only inhibited CaMKII γ activation but also unexpectedly stimulated the MerTK signaling pathway, enhancing macrophage phagocytic efficacy and facilitating the clearance of apoptotic cells.¹⁵⁷

CD47 is a key anti-phagocytic signaling molecule whose overexpression on foam cells in atherosclerotic plaques impairs classical immune surveillance mechanisms. This disruption hinders macrophage-mediated phagocytosis and aggravates plaque instability.¹⁵⁸ Researches evaluated the therapeutic efficacy of CD47-blocking antibodies across murine model of atherosclerosis.^147,159 The results showed that CD47 inhibition corrected endocytosis deficiencies, restored the self-clearing capacity of vascular tissue, and slowed atherosclerosis progression.¹⁶⁰ Building on this foundation, Chen et al engineered platelet membrane- encapsulated mesoporous silicon nanoparticles as an innovative drug delivery platform. This design facilitates the precise delivery of anti-CD47 antibodies to atherosclerotic plaque regions, enabling precise therapeutic interventions at lesion sites. Experimental results demonstrate that this approach enhances necrotic cell clearance, reduces plaque area, and mitigates the risk of plaque rupture and thrombosis, offering a promising therapeutic strategy for atherosclerosis management.¹⁵⁸

Similarly, Chuang et al developed an innovative nano-immunoengineering platform (CAR-M/β-CD LNP), consisting of anti-CD47 chimeric antigen receptor (CAR) - engineered monocytes and macrophages, along with surface-anchored Hydroxypropyl β-cyclodextrin (HPβ-CD) lipid NPs (β-CD LNPs), to target apoptotic cells with heightened CD47 expression (CD47^Hi ACs), which are challenging to clear (Figure 11). The underlying mechanisms are as follows: CAR-M/β-CD LNPs specifically target inflamed lesions, navigate through them, and enable the targeted elimination of CD47^Hi ACs. Cholesterol-rich materials are cleared by β-CD released from the cell surface LNPs via ROS-driven degradation. Cholesterol-derived oxysterols, facilitated by β-CD, activate the LXR signaling pathway, upregulating critical downstream effectors including ABCA1, ABCG1, and Mertk, thereby enhancing cholesterol efflux and mitigating inflammatory responses. Our findings demonstrate that the synergistic interplay between HPβ-CD and anti-CD47 CAR significantly enhances phagocytosis, outperforming the outcomes achieved by CD47 blockade monotherapy. This study provides valuable insights for future strategies targeting resistant cell populations, advancing therapeutic possibilities.¹⁶¹

Figure 11 Augmentation of CAR macrophage efferocytosis through surface-modified lipid nanoparticles directed at LXR signaling. (A) Schematic representation of β-CD lipid nanoparticles incorporation into THP-1 cells through CD45 engagement. (B) Detection of surface β-CD lipid nanoparticles incorporating DSPE-PEG-biotin through the utilization of a secondary reporter (AlexaFluor 647-streptavidin) via flow cytometry. (C) Exemplary flow cytometry dot plot illustrating surface β-CD lipid nanoparticles on THP-1 cells over a 2-day period. (D) Experimental conditions designed to assess macrophage phagocytosis of CD47Hi AC. (E) Quantitative analysis using CellTagging of total engulfment following 1 h incubation of macrophage with CD47Hi AC at 37 °C (n = 3; *P < 0.05, **P < 0.01, ****P < 0.0001; ns, no significant difference). (F) Activation of LXR signaling targets ABCA1 and ABCG1, along with efferocytosis targets Il-10 and Mertk in control macrophages with β-CD lipid nanoparticles or CAR-Ms with β-CD lipid nanoparticles following co-culture with CD47Hi AC for 2 h at 37 °C (n = 3; *P < 0.05, **P < 0.01, ***P < 0.001). Reproduced under terms of the CC-BY license.161 Copyright 2024, Wiley-VCH GmbH. Abbreviations: CAR, chimeric antigen receptor; LXR, liver X receptor; MerTK, Mer tyrosine kinase.

Moreover, Sha et al introduced MM@Lips-SHP1i, a biomimetic nanoparticle integrating macrophage membranes with liposome nanoparticles encapsulating an SHP1 inhibitor (SHP1i). Within plaque cores, MM@Lips-SHP1i effectively outcompetes macrophages for ox-LDL and LPS binding sites, inhibiting foam cell formation and reducing pro-inflammatory cytokine release. The SHP1i further disrupts CD47 signal regulatory protein-α signaling, enhancing apoptotic cell clearance by macrophages and mitigating plaque progression. This multifaceted therapeutic approach offers a groundbreaking strategy for atherosclerosis treatment and provides novel insights for addressing related diseases.¹⁴⁹ Similarly, SWNT-SHP1i.¹⁶²

Biomaterials Promote the Regression of Atherosclerotic Plaque by Inhibiting the Phenotype Conversion of Smooth Muscle Cells

In the adult vascular system, VSMCs typically demonstrate minimal synthetic activity and proliferation, while maintaining a specialized network of signaling molecules, ion channels, and regulatory proteins that govern vascular contractility.^163,164 However, VSMCs display remarkable plasticity, undergoing phenotypic transitions in response to vascular injury. They shift from a quiescent state to a dedifferentiated, synthetic phenotype with increased migratory and proliferative potential, essential for vascular repair.¹⁷ This plasticity, though beneficial for injury response, also predisposes VSMCs to environmental triggers that promote disease-related phenotypic shifts.

The phenotypic transformation of SMCs is a pathological process involving dedifferentiation, migration, and transdifferentiation into alternative cell lineages, playing a pivotal role in atherosclerosis pathogenesis.¹⁶⁵ Among these, intermediate cells derived from SMCs, termed “SEM” cells (formed via fusion with stem cells, ECs, and monocytes), exhibit pluripotency, allowing differentiation into macrophage-like or fibrochondrocyte-like cells, along with reversion to the SMC phenotype.^166,167

PCSK9, a serine protease and key member of the proprotein convertase family, is primarily synthesized and secreted by the liver.¹⁶⁸ PCSK9 modulates the phenotypic transformation of VSMCs by regulating critical molecules such as α-SMA, osteopontin, and vimentin. Evolocumab, a specific PCSK9 inhibitor, has shown significant potential in influencing VSMC behavior. Pan et al developed a biomimetic nanoliposome system encapsulating evolocumab (Figure 12). Nanoliposomes undergo modification with Polyethylene glycol and are camouflaged utilizing Møm to yield (Lipo + M)@ E nanoparticles. The experiment demonstrates that the nanosystem can specifically deliver evolocumab to VSMCs of atherosclerotic plaques, augment the expression of α-SMA and vimentin, while suppressing osteopontin expression, consequently inhibiting VSMC phenotypic transformation, aberrant proliferation, and migration.¹⁶⁹

Figure 12 Evolocumab-loaded bio-liposomes for enhanced atherosclerosis treatment. (A) Synthesis of (Lipo + M) @E NPs. (B) Illustrative images depicting blood samples from C57BL/6 mice post- administration of various nanomaterials at distinct temporal intervals. (C) Analysis of (Lipo + M) @E NPs fluorescence intensity (stained for anti-PEG) along the white arrowed lines. (D) Pharmacokinetic profiles of various nanomaterials. (E) Proliferation of VSMCs assessed by EdU incorporation assay. Blue signifies nuclei and green indicates the EdU-positive VSMCs. Scale bars=60 µm. (F) Quantification of migrated VSMCs (1 Control, 2 Model, 3 Evol, 4 Lipo@E, 5 (Lipo+M) @E) (n = 3; ###P < 0.001 vs. the Control, **P < 0.01, ***P < 0.001 vs. the Model). Reproduced under terms of the CC-BY license.169 Copyright 2023, Springer Nature. Abbreviation: VSMCs, vascular smooth muscle cells.

Research elucidated the crucial role of microRNA-145 (miR-145) in regulating VSMC phenotypic transitions.^170–172 Chin et al engineered miR-145-loaded micelles targeting the C-C chemokine receptor-2, which exhibits elevated expression on synthetic VSMCs. Their findings indicate that miR-145 micelles not only facilitate the phenotypic conversion of VSMCs toward a contractile state under experimental conditions but also reduce the formation of unstable atherosclerotic plaques in vivo, presenting a novel therapeutic avenue for atherosclerosis.¹⁷⁰ Patel et al extended this research by analyzing VSMCs derived from patient samples, revealing that as disease severity increased, contractile markers (eg, miR-145, ACTA2, and MYH11) declined while synthetic markers (eg, KLF4, KLF5, and ELK1) rose. Notably, miR-145 micellar therapy restored contractile markers expression to near-normal levels, underscoring its potential to reverse pathological VSMC phenotypic conversion. These findings strongly support the clinical application of miR-145 micelles across diverse atherosclerotic stages.¹⁷³

Conclusion and Prospects

Currently, the global prevalence of atherosclerosis continues to rise, with cardiovascular and cerebrovascular complications now among the principal causes of mortality. However, the clinical management of atherosclerosis primarily relies on lipid-lowering medications. Traditional lipid-lowering therapy frequently necessitates high-dose or even combination treatment, which may cause serious adverse reactions. These medications possess a singular mechanism of action, which is inadequate to address the intricate milieu of atherosclerosis and cannot reverse or diminish its progression. Therefore, precision therapies are essential to mitigate or prevent cardiovascular and cerebrovascular diseases. Biomaterials, with their unique physical, chemical, and biological properties, hold promise for atherosclerotic plaque management. This review provides a detailed examination of innovative technologies and pharmacological interventions for atherosclerosis treatment, highlighting their mechanisms of action, as depicted in Table 1.

Table 1 Treatment Strategies for Atherosclerotic Plaque

In the context of atherosclerotic plaque treatment, four primary strategies are identified: restoring normal EC function, inhibiting abnormal neutrophil activation, regulating macrophage behavior, and preventing the phenotypic transformation of VSMCs. These strategies aim to reduce plaque burden, enhance plaque stabilization, and lower the incidence of cardiovascular and cerebrovascular diseases.

ECs serve as the paramount initiators of the atherosclerotic process, making their functional restoration critical. Biomaterials selectively mitigate detrimental processes such as oxidative stress, ferroptosis, and EndoMT, thereby promoting endothelial recovery and reinforcing vascular barrier integrity. Neutrophils, key inflammatory mediators within plaques, exacerbate inflammation and plaque instability when excessively activated. Biomaterials suppress inflammatory cascades by inhibiting neutrophil activation, thus arresting plaque progression. In parallel, biomaterials regulate macrophage activation and polarization states, optimizing lipid metabolism, restoring autophagy, and enhancing efferocytosis. These mechanisms not only stabilize plaques but also accelerate their natural regression, highlighting the therapeutic promise of this approach. Furthermore, biomaterials strengthen the fibrous cap by preventing inappropriate VSMC phenotypic transformation, thereby enhancing plaque stability and offering long-term health benefits for patients. Collectively, these biomaterial-based strategies provide a robust framework for managing atherosclerotic plaques, offering renewed hope for improving patient outcomes and quality of life.

Notwithstanding these advancements, the clinical implementation of biomaterial-based therapies encounters substantial obstacles. Presently, only a limited number of such technologies have been approved for treating atherosclerotic plaques. Compared to traditional pharmaceuticals, biomaterials present greater obstacles in clinical adoption due to their complex structures, which often involve intricate surface modifications and multi-component payloads. These factors lead to higher production costs, challenges in manufacturing and quality control, variability between batches, and unstable storage conditions, all of which hinder large-scale production.

Moreover, atherosclerosis plaque is a chronic condition that requires long-term management and necessitates rigorous evaluation of short-and long-term toxicity of biomaterial-based treatments. For instance, risks such as off-target toxicity, immune reactions, or the potential for long-term accumulation within the body.^36,174,175 The issue of off-target toxicity arises primarily from the relative, rather than absolute, overexpression of target molecules in diseased versus healthy tissues, resulting in unintended nanocarrier accumulation in non-target organs. Strategies to enhance specificity include the development of “intelligent” stimuli-responsive (eg, to pH, enzymes, or ROS) or dual/sequential targeting systems. Furthermore, concerns regarding immunogenicity can be mitigated by employing natural cell membrane coatings—such as those derived from erythrocytes, leukocytes, or platelets—to significantly improve biocompatibility and confer immune-evasive properties. Moreover, addressing the risk of long-term bioaccumulation necessitates the design of fully biodegradable carrier materials, which constitutes a critical consideration for the translational development of future biomaterials. Such considerations are essential for establishing a reliable foundation for clinical application.

Finally, the scope of animal models suitable for studying atherosclerosis must be broadened. The majority of models employed in nanomedicine-related atherosclerosis research involve mice and rabbits. While these models have enhanced comprehension of atherosclerotic pathophysiology and partially validating novel therapeutic approaches, their pathologies diverge from those observed in humans. Furthermore, large animals, including swine and non-human primates, are cost-prohibitive. Consequently, the development of mature, human-like atherosclerosis models is an urgent issue requiring resolution. The contraindications of nanomedicine for atherosclerosis remain ambiguous. Generally, patients with atherosclerosis often exhibit comorbidities such as coronary artery disease, cerebrovascular accident, diabetes, adiposity, and hepatic or renal dysfunction. Investigating the viability and potential contraindications of nanoparticles in such intricate disease cohorts proves challenging. Consequently, identifying nanomedicine contraindications may be facilitated through the development of animal models simulating multiple concurrent diseases.

These challenges, to some degree, hinder the advancement of nanomedicine. A deeper understanding of atherosclerosis pathogenesis could unveil novel biomarkers and therapeutic targets, opening avenues for pioneering biomaterial-based therapies and advancing the field.