Regression Of Atherosclerotic Lesions Research Articles

Administration of an LXR agonist promotes atherosclerotic lesion remodelling in murine inflammatory arthritis.

The leading cause of mortality in patients with rheumatoid arthritis is atherosclerotic cardiovascular disease (CVD). We have shown that murine arthritis impairs atherosclerotic lesion regression, because of cellular cholesterol efflux defects in haematopoietic stem and progenitor cells (HSPCs), causing monocytosis and impaired atherosclerotic regression. Therefore, we hypothesised that improving cholesterol efflux using a Liver X Receptor (LXR) agonist would improve cholesterol efflux and improve atherosclerotic lesion regression in arthritis. Ldlr -/- mice were fed a western-type diet for 14 weeks to initiate atherogenesis, then switched to a chow diet to induce lesion regression and divided into three groups; (1) control, (2) K/BxN serum transfer inflammatory arthritis (K/BxN) or (3) K/BxN arthritis and LXR agonist T0901317 daily for 2 weeks. LXR activation during murine inflammatory arthritis completely restored atherosclerotic lesion regression in arthritic mice, evidenced by reduced lesion size, macrophage abundance and lipid content. Mechanistically, serum from arthritic mice promoted foam cell formation, demonstrated by increased cellular lipid accumulation in macrophages and paralleled by a reduction in mRNA of the cholesterol efflux transporters Abca1, Abcg1 and Apoe. T0901317 reduced lipid loading and increased Abca1 and Abcg1 expression in macrophages exposed to arthritic serum and increased ABCA1 levels in atherosclerotic lesions of arthritic mice. Moreover, arthritic clinical score was also attenuated with T0901317. Taken together, we show that the LXR agonist T0901317 rescues impaired atherosclerotic lesion regression in murine arthritis because of enhanced cholesterol efflux transporter expression and reduced foam cell development in atherosclerotic lesions.

Extracellular Vesicles as Drivers of Immunoinflammation in Atherothrombosis.

Atherosclerotic cardiovascular disease is the leading cause of morbidity and mortality all over the world. Extracellular vesicles (EVs), small lipid-bilayer membrane vesicles released by most cellular types, exert pivotal and multifaceted roles in physiology and disease. Emerging evidence emphasizes the importance of EVs in intercellular communication processes with key effects on cell survival, endothelial homeostasis, inflammation, neoangiogenesis, and thrombosis. This review focuses on EVs as effective signaling molecules able to both derail vascular homeostasis and induce vascular dysfunction, inflammation, plaque progression, and thrombus formation as well as drive anti-inflammation, vascular repair, and atheroprotection. We provide a comprehensive and updated summary of the role of EVs in the development or regression of atherosclerotic lesions, highlighting the link between thrombosis and inflammation. Importantly, we also critically describe their potential clinical use as disease biomarkers or therapeutic agents in atherothrombosis.

Roles of Macrophages in Atherogenesis.

Atherosclerosis is a chronic inflammatory disease that may ultimately lead to local proteolysis, plaque rupture, and thrombotic vascular disease, resulting in myocardial infarction, stroke, and sudden cardiac death. Circulating monocytes are recruited to the arterial wall in response to inflammatory insults and differentiate into macrophages which make a critical contribution to tissue damage, wound healing, and also regression of atherosclerotic lesions. Within plaques, macrophages take up aggregated lipoproteins which have entered the vessel wall to give rise to cholesterol-engorged foam cells. Also, the macrophage phenotype is influenced by various stimuli which affect their polarization, efferocytosis, proliferation, and apoptosis. The heterogeneity of macrophages in lesions has recently been addressed by single-cell sequencing techniques. This article reviews recent advances regarding the roles of macrophages in different stages of disease pathogenesis from initiation to advanced atherosclerosis. Macrophage-based therapies for atherosclerosis management are also described.

Key Chemokine Pathways in Atherosclerosis and Their Therapeutic Potential.

The search to improve therapies to prevent or treat cardiovascular diseases (CVDs) rages on, as CVDs remain a leading cause of death worldwide. Here, the main cause of CVDs, atherosclerosis, and its prevention, take center stage. Chemokines and their receptors have long been known to play an important role in the pathophysiological development of atherosclerosis. Their role extends from the initiation to the progression, and even the potential regression of atherosclerotic lesions. These important regulators in atherosclerosis are therefore an obvious target in the development of therapeutic strategies. A plethora of preclinical studies have assessed various possibilities for targeting chemokine signaling via various approaches, including competitive ligands and microRNAs, which have shown promising results in ameliorating atherosclerosis. Developments in the field also include detailed imaging with tracers that target specific chemokine receptors. Lastly, clinical trials revealed the potential of various therapies but still require further investigation before commencing clinical use. Although there is still a lot to be learned and investigated, it is clear that chemokines and their receptors present attractive yet extremely complex therapeutic targets. Therefore, this review will serve to provide a general overview of the connection between various chemokines and their receptors with atherosclerosis. The different developments, including mouse models and clinical trials that tackle this complex interplay will also be explored.

Inhibition of interleukin-1β signalling promotes atherosclerotic lesion remodelling in mice with inflammatory arthritis.

ObjectivesRheumatoid arthritis (RA), an inflammatory joint disorder, independently increases the risk of cardiovascular disease (CVD). IL‐1β contributes to both RA and CVD. We hypothesised that inhibiting IL‐1 signalling with the IL‐1R antagonist, anakinra, would dampen inflammation and promote resolution of atherosclerosis in arthritic mice.MethodsLow‐density lipoprotein receptor (Ldlr)‐deficient mice were fed a Western‐type diet for 14 weeks to develop atherosclerotic plaques. Mice were then switched to a chow diet, promoting lesion regression, and randomised to a control group or into groups where arthritis was induced by passive transfer of K/BxN arthritogenic serum. The arthritic mice were further randomised to vehicle or anakinra.ResultsArthritis impaired atherosclerotic lesion regression when cholesterol was lowered. This was associated with a higher burden of plaque macrophages, likely due to monocytosis, driven by myelopoiesis in the bone marrow and spleen. Interestingly, delayed intervention with anakinra had no effect on arthritis in these mice. However, a significant improvement in atherosclerotic plaque remodelling to a more stable phenotype was observed. This was associated with fewer circulating monocytes, caused by a reduction in splenic extramedullary myelopoiesis.ConclusionWe show that inhibiting IL‐1 signalling in arthritic mice with pre‐existing atherosclerosis promotes lesion remodelling to a more stable phenotype, that is less likely to rupture and cause ischemic events such as myocardial infarction. This suggests that IL‐1R antagonism may suppress CVD complications in patients with RA. Furthermore, inhibiting IL‐1β signalling in other patients with inflammatory diseases that also predispose to CVD may also benefit from anti‐IL‐1 therapy.

Endurance exercise training does not limit coronary atherosclerosis in familial hypercholesterolemic swine

Prospective, cohort studies in humans demonstrate that moderate to high levels of physical activity reduce both morbidity and mortality of coronary heart disease (CHD) including a decreased progression and/or regression of CHD with life‐style modification which includes exercise. However, a thorough review of both human and animal literature reveals equivocal evidence to support an intrinsic, direct exercise effect in attenuating the development of CHD. Exercise reduces development and/or causes regression of atherosclerotic lesions in mice and rabbits, however in larger mammals including primates, the evidence is more equivocal. A major limitation has been the lack of large animal models with clinically evident CHD disease. Thus, we sought to determine the effect of endurance exercise in CHD development and compensatory remodeling in a swine model of familial hypercholesterolemia (FH) that exhibits robust, complex atherosclerosis. Castrated male Rapacz familial hypercholesterolemic (FH) swine were obtained from the University of Wisconsin Swine Research and Teaching Center. Pigs were randomly assigned to either sedentary (Sed; n=9) or exercise trained (Ex; n=8) groups. At 10 months of age, Ex pigs began a 10 month treadmill‐training intervention consisting of moderate‐intensity (70% of maximal heart rate) once per day, for 5 days each week. At 14 months, all pigs were switched to a high‐fat, high‐cholesterol diet (HF; by weight 13% protein, 21.3% fat, 41.4% carbohydrate, 2% cholesterol and 1% sodium cholate). CHD was assessed by intravascular ultrasound (IVUS) both prior to (14 months of age) and after completion of 6 months on the HF diet (20 months of age). Angiograms and IVUS were obtained using standard coronary catheterization techniques. IVUS pullbacks (0.5 mm/sec; Galaxy II, Boston Scientific, 40MHz) were obtained for the proximal anterior descending (LAD) and left circumflex (LCX) arteries. For analysis, the total segment was subdivided into 3 sections and total vessel volume, lumen volume, total plaque burden volume and percent plaque burden were determined in the proximal, mid, and distal segments from 3D reconstruction (QIVUS software; Medis). Prior to HF diet, Ex resulted in a greater coronary artery size (vessel and lumen volume) in the proximal and mid sections of the LCX compared to SED, with no effect in the LAD. Relative plaque volume was minimal (~15–20% vessel area) in both Sed and Ex groups. After 6 months on HF diet, there was a 5–6 fold increase in absolute plaque volume in all segments of the LCX and LAD in both groups. Ex had no effect on absolute plaque volume at 20 months in any segment of either LCX or LAD. In both Sed and Ex groups, vessel volume was greater at 20 months compared to 14 months such that lumen volume was maintained despite the increase in plaque volume, i.e. compensatory outward remodeling was similar in both groups. Overall at 20 months, there was no significant difference in vessel volume, lumen volume, absolute or relative plaque volume in either the LCX or LAD between Sed and Ex animals. These findings fail to support an independent, direct effect of exercise in limiting CHD progression in familial hypercholesterolemia.Support or Funding InformationNIH HL52490This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Involvement of caveolin-1 and CD36 in native LDL endocytosis by endothelial cells

Atherosclerosis is a lipid disease characterized by accumulation of low density lipoprotein (LDL) in the artery wall. The transport of LDL across the endothelium of coronary artery is an initiating event of atherosclerosis, whose mechanism remains poorly understood. In the last decade, it has been shown that in caveolin-1 (Cav-1) deficient mice, LDL infiltration in aorta wall is decreased and CD36 expression in aortas is down-regulated, leading to regression of atherosclerotic lesions. In the present study, we show that native LDL endocytosis is decreased in endothelial cells deficient in Cav-1 or CD36. We demonstrate that Cav-1 and CD36 interact in caveolae-rich domains by different biochemical approaches. In addition, confocal microscopy reveals some colocalization of Cav-1 with CD36. These findings indicate that caveolae and CD36 are involved in native LDL endocytosis and suggest that CD36 might be a good candidate for the transport of native LDL across the endothelium, an early event in atherosclerosis.

HDL is essential for atherosclerotic lesion regression in Apoe knockout mice by bone marrow Apoe reconstitution

Background and aimsAlthough studies in mice have suggested that lesion regression is feasible, the underlying mechanisms remain largely unknown. Here we determined the impact of high-density lipoprotein (HDL) on atherosclerosis regression outcome. MethodsAtherosclerotic lesion dynamics were studied upon bone marrow transplantation-mediated re-introduction of apolipoprotein E (Apoe) in Apoe knockout mice. Probucol was used to pharmacologically deplete HDL. ResultsRestoration of Apoe function was associated with an initial growth of atherosclerotic lesions and parallel decrease in lesional macrophage foam cell content (47 ± 4% at 4 weeks versus 72 ± 2% at baseline: p < 0.001), despite the fact that cholesterol levels were markedly reduced. Notably, significant lesion regression was detected from 4 weeks onwards, when plasma cholesterol levels had returned to the normolipidemic range. As a result, lesions were 41% smaller (p < 0.05) at 8 weeks than at 4 weeks after bone marrow transplantation. Regressed lesions contained an even lower level of macrophage foam cells (33 ± 5%: p < 0.001) and were rich in collagen. Probucol co-treatment was associated with a 3.2-fold lower (p < 0.05) plasma HDL-cholesterol level and a more pro-inflammatory (CCR2+) monocyte phenotype. Importantly, probucol-treated mice exhibited atherosclerotic lesions that were larger than those of regular chow diet-fed bone marrow transplanted mice at 8 weeks (186 ± 15*103 μm2 for probucol-treated versus 120 ± 19*103 μm2 for controls: p < 0.05). ConclusionsWe have shown that probucol-induced HDL deficiency impairs the ability of established lesions to regress in response to reversal of the genetic hypercholesterolemia in Apoe knockout mice. Our studies thus highlight a crucial role for HDL in the process of atherosclerosis regression.

Arresting Progression and Promoting Regression of Atherosclerotic Lesions: a Dose-dependent Effect of Active Immunization with an Anti-glycosaminoglycan mAb

Arresting Progression and Promoting Regression of Atherosclerotic Lesions: a Dose-dependent Effect of Active Immunization with an Anti-glycosaminoglycan mAb

Defective cholesterol metabolism in haematopoietic stem cells promotes monocyte-driven atherosclerosis in rheumatoid arthritis.

Rheumatoid arthritis (RA) is associated with an approximately two-fold elevated risk of cardiovascular (CV)-related mortality. Patients with RA present with systemic inflammation including raised circulating myeloid cells, but fail to display traditional CV risk-factors, particularly dyslipidaemia. We aimed to explore if increased circulating myeloid cells is associated with impaired atherosclerotic lesion regression or altered progression in RA. Using flow cytometry, we noted prominent monocytosis, neutrophilia, and thrombocytosis in two mouse models of RA. This was due to enhanced proliferation of the haematopoietic stem and progenitor cells (HSPCs) in the bone marrow and the spleen. HSPCs expansion was associated with an increase in the cholesterol content, due to a down-regulation of cholesterol efflux genes, Apoe, Abca1, and Abcg1. The HSPCs also had enhanced expression of key myeloid promoting growth factor receptors. Systemic inflammation was found to cause defective cellular cholesterol metabolism. Increased myeloid cells in mice with RA were associated with a significant impairment in lesion regression, even though cholesterol levels were equivalent to non-arthritic mice. Lesions from arthritic mice exhibited a less stable phenotype as demonstrated by increased immune cell infiltration, lipid accumulation, and decreased collagen formation. In a progression model, we noted monocytosis, enhanced monocytes recruitment to lesions, and increased plaque macrophages. This was reversed with administration of reconstituted high-density lipoprotein (rHDL). Furthermore, RA patients have expanded CD16+ monocyte subsets and a down-regulation of ABCA1 and ABCG1. Rheumatoid arthritis impairs atherosclerotic regression and alters progression, which is associated with an expansion of myeloid cells and disturbed cellular cholesterol handling, independent of plasma cholesterol levels. Infusion of rHDL prevented enhanced myelopoiesis and monocyte entry into lesions. Targeting cellular cholesterol defects in people with RA, even if plasma cholesterol is within the normal range, may limit vascular disease.

Lipid core nanoparticles resembling low-density lipoprotein and regression of atherosclerotic lesions: effects of particle size.

Particles are usually polydispersed and size is an important feature for lipid-based drug delivery systems in order to optimize cell-particle interactions as to pharmacologic action and toxicity. Lipid nanoparticles (LDE) with composition similar to that of low-density lipoprotein carrying paclitaxel were shown to markedly reduce atherosclerosis lesions induced in rabbits by cholesterol feeding. The aim of this study was to test whether two LDE fractions, one with small (20–60 nm) and the other with large (60–100 nm) particles, had different actions on the atherosclerotic lesions. The two LDE-paclitaxel fractions, prepared by microfluidization, were separated by density gradient ultracentrifugation and injected (4 mg/body weight, intravenously once a week) into two groups of rabbits previously fed cholesterol for 4 weeks. A group of cholesterol-fed animals injected with saline solution was used as control to assess lesion reduction with treatment. After the treatment period, the animals were euthanized for analysis. After treatment, both the small and large nanoparticle preparations of LDE-paclitaxel had equally strong anti-atherosclerosis action. Both reduced lesion extension in the aorta by roughly 50%, decreased the intima width by 75% and the macrophage presence in the intima by 50%. The two preparations also showed similar toxicity profile. In conclusion, within the 20–100 nm range, size is apparently not an important feature regarding the LDE nanoparticle system and perhaps other solid lipid-based systems.

Abstract 4: Deletion of Macrophage Low-density Lipoprotein Receptor-related Protein 1 (LRP1) Accelerates Atherosclerosis Regression by Increasing CCR7-dependent Egress of Plaque Macrophages

We previously showed that mice lacking macrophage LDL receptor-related protein 1 (LRP1) undergo accelerated lesion formation due to increased apoptosis, decreased efferocytosis, and enhanced macrophage transformation into the inflammatory M1 phenotype. In vitro, LRP1-deficient macrophages (MΦLRP1 -/- ) show enhanced plasticity with exaggerated polarization towards either the inflammatory M1- or the anti-inflammatory M2-phenotype depending on the stimulant (LPS or IL-4, respectively). During atherosclerosis regression, the M2:M1 macrophage ratio increases as lesion M1 macrophages egress and inflammation resolves. Thus, we hypothesize that atherosclerosis regression is accelerated in MΦLRP1 -/- mice via enhanced macrophage M2 polarization and CCR7-dependent M1 macrophage egress. ApoE-/- mice on high fat diet for 12 weeks were reconstituted with bone marrow from wildtype (WT) or MΦLRP1 -/- mice and then placed on chow diet for 8 weeks. In this model, apoE is reintroduced into circulation to correct the hyperlipidemia and induce regression of atherosclerotic lesions. A cohort of apoE -/- mice reconstituted with apoE -/- bone marrow served as baseline controls. Lesions in both WT and MΦLRP1 -/- mice regressed relative to controls (11% and 22%, respectively; p&lt;0.05), but MΦLRP1 -/- lesions were 13% smaller than those of WT mice (p&lt;0.05). LRP1 deletion increased M2 transformation of macrophages and a higher M2:M1 macrophage ratio (p&lt;0.01) in the plaque. MΦLRP1 -/- lesions contained 36% fewer M1 macrophages compared to WT (p&lt;0.01). In vivo studies of reverse cholesterol transport (RCT) revealed that MΦLRP1 -/- have a 1.4-fold higher RCT compared to WT mice (p&lt;0.01). MΦLRP1 -/- lesions contained 2.5-fold more CCR7 + macrophages relative to WT lesions (p&lt;0.01), and in our in vivo egress assay 4.6-fold more CCR7 + macrophages were found in mediastinal lymph nodes. In vitro , M1-differentiated MΦLRP1 -/- macrophages expressed 1.6-fold higher Ccr7 mRNA compared to WT controls (p&lt;0.01). Thus, the absence of macrophage LRP1 accelerates atherosclerosis regression due to enhanced transformation of macrophages into an anti-inflammatory M2 phenotype, increased cholesterol efflux, and increased CCR7-driven egress of M1 macrophages from lesions.

Regression of atherosclecrotic lesions: medicinal and alimentary factors

The article reports results of clinical studies aimed to elucidate the influence of medicines on the size and density of atherosclerotic plaques in the walls of coronary and cerebral arteries. The phenomenon of regression of atherosclerotic lesions in the survivors of Leningrad siege during a long period of starvation is analyzed. The influence of inhibitors of angiotensin-converting enzyme on apoptosis of smooth muscle and foam cells of atherosclerotic plaques in the sanological mechanisms of atherosclerosis is discussed. The concept of natural regression of atherosclerosis is formulated and the necessity of development of the methods for is pharmacological activation are formulated.

Abstract 49: Elevating Apolipoprotein A-I Levels Promotes Atherosclerosis Regression in Diabetic Mice by Inhibiting Proliferation of Bone Marrow Monocyte Precursors

Diabetes is a primary risk factor for cardiovascular diseases (CVD) and in clinical imaging studies is shown to impair the resolution of CVD, a process termed regression. We have also reported this failure of lesion regression in mouse models of diabetes, despite effective lipid lowering. This, in part, can be attributed to diabetes-driven monocytosis promoting continued monocyte infiltration into plaques. In non-diabetic settings apolipoprotein (apo) A-I and high-density lipoprotein (HDL) suppress leukocytosis and promote lesion regression. As low apoA-I/HDL is a typical feature of diabetic dyslipidemia this study aimed to establish whether raising apoA-I/HDL levels in vivo is an effective approach to reduce diabetes-driven leukocytosis and promote lesion regression. Aortic arches from hyperlipidemic Ldlr -/- mice were transplanted into WT, diabetic WT, and diabetic human apoA-I-overexpressing transgenic mice (transgenic mice have a 3-fold increase in HDL-cholesterol), and lesion composition assessed 2 weeks post-surgery. Following aortic transplantation into WT mice (i.e. normal lipid levels) we found regression, as assessed by change in plaque macrophage (mΦ) content relative to baseline control mice was achieved (68% mΦ reduction, P&lt;0.001). Regression was impaired when aortas were transplanted into diabetic WT recipients (50% mΦ reduction, P&lt;0.01). However, raising apoA-I/HDL levels in the setting of diabetes restored regression in diabetic mice (62% mΦ reduction, P&lt;0.001). In vivo monocyte/mΦ trafficking analyses revealed that elevating apoA-I/HDL levels in diabetes improves atherosclerosis regression by reducing monocyte entry by 60% (P&lt;0.01), and promoting mΦ egress from lesions (30% increase). We also found that greater apoA-I/HDL reduced blood monocytes by decreasing the proliferation of monocyte progenitors in the bone marrow (15-20% reduction, P&lt;0.05), explaining, in part, how apoA-I/HDL promotes regression. Raising apoA-I/HDL levels promotes atherosclerotic lesion regression in diabetic mice. This may serve as a therapeutic strategy for patients with diabetes, who unlike WT mice, have reduced HDL levels and remain at an elevated risk for CVD despite effective plasma cholesterol lowering.

Macrophage Phenotype and Function in Different Stages of Atherosclerosis.

The remarkable plasticity and plethora of biological functions performed by macrophages have enticed scientists to study these cells in relation to atherosclerosis for >50 years, and major discoveries continue to be made today. It is now understood that macrophages play important roles in all stages of atherosclerosis, from initiation of lesions and lesion expansion, to necrosis leading to rupture and the clinical manifestations of atherosclerosis, to resolution and regression of atherosclerotic lesions. Lesional macrophages are derived primarily from blood monocytes, although recent research has shown that lesional macrophage-like cells can also be derived from smooth muscle cells. Lesional macrophages take on different phenotypes depending on their environment and which intracellular signaling pathways are activated. Rather than a few distinct populations of macrophages, the phenotype of the lesional macrophage is more complex and likely changes during the different phases of atherosclerosis and with the extent of lipid and cholesterol loading, activation by a plethora of receptors, and metabolic state of the cells. These different phenotypes allow the macrophage to engulf lipids, dead cells, and other substances perceived as danger signals; efflux cholesterol to high-density lipoprotein; proliferate and migrate; undergo apoptosis and death; and secrete a large number of inflammatory and proresolving molecules. This review article, part of the Compendium on Atherosclerosis, discusses recent advances in our understanding of lesional macrophage phenotype and function in different stages of atherosclerosis. With the increasing understanding of the roles of lesional macrophages, new research areas and treatment strategies are beginning to emerge.

RAGE Against the ABCs.

Diabetes is an insidious disease that significantly contributes to the development of atherosclerotic cardiovascular disease (CVD). One of the major factors contributing to atherosclerosis is the accumulation of lipid-laden macrophages in the vascular wall (1). Removal of cholesterol from macrophages is essential for the regression of atherosclerotic lesions. This can be achieved by cholesterol-lowering drugs (i.e., statins) or by enhancing the reverse cholesterol transport pathway (i.e., raising HDL). Unfortunately, in the setting of diabetes, cholesterol-lowering drugs such as statins can be less effective (2), and preclinical models have revealed a major defect in lesion regression even when cholesterol levels are normalized (3–5). This suggests that a major defect in cholesterol metabolism occurs in the setting of diabetes. The Hedrick and Oram laboratories originally discovered that diabetes causes a downregulation of the ATP binding cassette transporters ABCG1 (6) and ABCA1 (7) in macrophages, promoting foam cell formation. ABCA1 and ABCG1 provide the dominant pathway of cholesterol removal from a number of cells in the body. Yvan-Charvet et al. (8) made the seminal discovery that codeletion of ABCA1/G1 results in a dramatic increase in atherosclerosis. Extensive research on the antiatherogenic role of these transporters has revealed their importance in removing cholesterol from plaque macrophages (9). However, recent discoveries have shown that ABCA1 and ABCG1 regulate the proliferation of hematopoietic stem and progenitor cells to control the abundance of blood monocytes (10). Along with promoting cholesterol efflux from macrophages, suppressing monocyte levels can directly inhibit the progression of atherosclerotic lesions, promote lesion regression, and provide beneficial outcomes after …

The effects of endothelial progenitor cells on rat atherosclerosis.

Atherosclerosis (AS) is a progressive disease characterized by endothelial injury and lipid aggregation in the arterial walls. Studies have reported that endothelial progenitor cells (EPCs) derived from the bone marrow (BM) might provide an endogenous repair mechanism by differentiating into endothelial cells to replace the dysfunctional endothelium. Our study aims to investigate the effect of EPCs derived from rat BM on AS. EPCs transduced by recombinant adeno-associated virus-green fluorescent protein (GFP) were transplanted into a rat AS model. After 2 months of transplantation, the localization of GFP-labeled cells, morphology, and lipid content in the aorta were examined. GFP-labeled EPCs were found in the endothelial monolayer of the artery vessel in the GFP/EPC group. Hematoxylin and eosin staining suggested that the lipid deposits in the aortic endothelium in the EPC/GFP group were less compared with those in the untreated group. Oil Red O staining of liver slices showed that lipid droplets were obviously decreased in the GFP/EPC group. The endothelial nitric oxide synthase and apolipoprotein E mRNA levels in the GFP/EPC group were significantly higher, but the intercellular cell adhesion molecule-1 mRNA level was significantly lower compared with the control group. The results suggest that EPCs derived from the BM can repair the injured endothelium and promote an atherosclerotic lesion regression. Therefore, EPCs may provide a useful tool for the treatment of AS.

Oral administration of baicalin and geniposide induces regression of atherosclerosis via inhibiting dendritic cells in ApoE-knockout mice

Atherosclerosis is a systemic inflammatory disease characterized by the accumulation of dendritic cells (DCs) and other types of immune cells in atherosclerotic plaque. In this study, baicalin and geniposide were isolated from Scutellaria baicalensis Georgi and Gardenia jasminoids Ellis, which are the plants used in traditional Chinese medicine to treat a variety of inflammatory diseases. We then investigated whether baicalin and geniposide could induce regression of atherosclerotic lesions in ApoE-/- mice fed a high cholesterol diet and used as a model of atherosclerosis. Following model induction, these mice were treated with baicalin (100mg/kg), geniposide (100mg/kg), and then a mixture containing baicalin (100mg/kg) and geniposide (100mg/kg) administered daily by gavage for a period of 12weeks. The combined administration of baicalin and geniposide significantly reduced atherosclerotic lesions, and modulated the phenotype of dendritic cells in bone marrow and atherosclerotic plaque. Geniposide lowered both plasma lipid levels and DC numbers, while baicalin administered either alone or in combination with geniposide did not decrease plasma lipids. Our results suggest that baicalin and geniposide may have immune-regulatory effects and prevent the formation of atherosclerotic lesions by decreasing the DC numbers, and inhibit DC maturation in bone marrow and infiltration into lesions.

Biodistribution of AAV8 Vectors Expressing Human Low-Density Lipoprotein Receptor in a Mouse Model of Homozygous Familial Hypercholesterolemia

Recombinant adeno-associated viral vectors based on serotype 8 (AAV8) transduce liver with superior tropism following intravenous (IV) administration. Previous studies conducted by our lab demonstrated that AAV8-mediated transfer of the human low-density lipoprotein receptor (LDLR) gene driven by a strong liver-specific promoter (thyroxin-binding globulin [TBG]) leads to high level and persistent gene expression in the liver. The approach proved efficacious in reducing plasma cholesterol levels and resulted in the regression of atherosclerotic lesions in a murine model of homozygous familial hypercholesterolemia (hoFH). Prior to advancing this vector, called AAV8.TBG.hLDLR, to the clinic, we set out to investigate vector biodistribution in an hoFH mouse model following IV vector administration to assess the safety profile of this investigational agent. Although AAV genomes were present in all organs at all time points tested (up to 180 days), vector genomes were sequestered mainly in the liver, which contained levels of vector 3 logs higher than that found in other organs. In both sexes, the level of AAV genomes gradually declined and appeared to stabilize 90 days post vector administration in most organs although vector genomes remained high in liver. Vector loads in the circulating blood were high and close to those in liver at the early time point (day 3) but rapidly decreased to a level close to the limit of quantification of the assay. The results of this vector biodistribution study further support a proposed clinical trial to evaluate AAV8 gene therapy for hoFH patients.

Intermittent Claudication: New Targets for Drug Development

Peripheral artery disease (PAD) is the result of extensive atherosclerosis in the arterial supply to the lower extremities. PAD is associated with increased systemic cardiovascular morbidity and mortality as well as substantial disability due to walking impairment. Claudication is the classic symptom of leg pain with walking that is relieved by rest, but patients with PAD without typical claudication also have a walking limitation. Treatment of the patient with PAD is directed towards reducing cardiovascular risk and improving exercise capacity. The pathophysiology of the physical impairment is complex as changes in the muscle distal to the arterial stenoses contribute to the limitations. Current treatment options to improve exercise performance have limitations emphasizing the need for new pharmacotherapies for this highly prevalent condition. The multifactorial contributors to the exercise impairment in PAD suggest potential targets for novel drug therapies. Advances in understanding angiogenesis make pharmacologic revascularization possible. However, ensuring that new blood vessels develop in a distribution relevant to the clinical impairment remains a challenge. Skeletal muscle metabolism and its regulation are altered in patients with PAD and strategies to improve the efficient oxidation of fuel substrates may improve muscle function. PAD is associated with increased oxidative stress which may result in injury to the muscle microvasculature and myocyte. Minimizing this oxidative stress by enhancing cellular defense mechanisms, administration of anti-inflammatory agents or by providing antioxidants, could prevent oxidative injury. Given the central role of atherosclerosis in the flow limitation, therapies to induce regression of atherosclerotic lesions could result in improved blood flow and oxygen delivery. Drugs targeting the distribution of blood flow in the microcirculatory environment of the muscle have the potential to better match oxygen delivery with working myocytes. The physical disability and flow limitations contribute to a loss of leg muscle mass in patients with PAD. Drugs to increase muscle mass and strength could enhance walking ability in these patients. Pharmacotherapies that recapitulate the muscle adaptations induced by preconditioning may result in improved physical performance in patients with PAD. Adjunctive therapies combined with exercise training or revascularization may be important given the complexity of integrative muscle function and the multiple pathologic changes induced by PAD. New research into the pathophysiology of the physical impairment associated with PAD has identified potential new targets for drug therapy, and will likely continue to do so in the years to come. Translation of these opportunities into effective therapeutics will be important as the already high prevalence of PAD is expected to increase as the population ages.