Normal Arterial Intima Research Articles

A novel protein encoded by circLARP1B promotes the proliferation and migration of vascular smooth muscle cells by suppressing cAMP signaling

Background and aimsCircular RNA (circRNA) is closely related to atherosclerosis (AS) incidence and progression, but its regulatory mechanism in AS needs further elucidation. AS development is significantly influenced by abnormal vascular smooth muscle cells (VSMCs) growth and migration. This study explored the potential protein role of circLARP1B in VSMC proliferation and migration. MethodsWe performed whole-transcriptome sequencing in human normal arterial intima and advanced atherosclerotic plaques to screen for differentially expressed circRNAs. The sequencing results were combined with database analysis to screen for circRNAs with coding ability. Real-time quantitative polymerase chain reaction was utilized to assess circLARP1B expression levels in atherosclerotic plaque tissues and cells. circLARP1B-243aa function and pathway in VSMCs growth and migration were studied by scratch, transwell, 5-ethynyl-2′-deoxyuridine, cell counting kit-8, and Western blot experiments. ResultsWe found that circLARP1B was downregulated in atherosclerotic plaque tissue and promoted the proliferation and migration of VSMCs. circLARP1B encodes a novel protein with a length of 243 amino acids. Through functional experiments, we confirmed the role of circLARP1B-243aa in enhancing VSMCs migration and proliferation. Mechanistically, circLARP1B-243aa promotes VSMCs migration and growth by upregulating phosphodiesterase 4C to inhibit the cyclic adenosine monophosphate signaling pathway. ConclusionsOur results suggested that circLARP1B could promote VSMCs growth and migration through the encoded protein circLARP1B-243aa. Therefore, it could be a treatment target and biomarker for AS.

LncRNA MIR4697HG Alleviates Endothelial Cell Injury and Atherosclerosis Progression in Mice via the FUS/ANXA5 Axis.

Atherosclerosis (AS) manifests with arterial intimal injury, lipid deposition and chronic inflammation, which is a key pathogenic cause of cardio-cerebrovascular disorders. LncRNA MIR4697HG was downregulated in human advanced atherosclerotic plaques. This study probed the precise biological functions and downstream regulatory mechanisms of MIR4697HG during AS progression. MIR4697HG levels in atherosclerotic plaque tissues and normal arterial intima were measured by RT-qPCR. An injury model of human umbilical vein endothelial cells (HUVECs) was induced through treating with oxidative low-density lipoprotein (ox-LDL). MIR4697HG overexpression plasmids (pcDNA-MIR4697HG) was transfected into ox-LDL-treated HUVECs, and then cell viability, apoptosis, reactive oxygen species (ROS) level, oxidative stress marker protein malondialdehyde (MDA) level and superoxide dismutase (SOD) activity, and adhesion molecule intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) levels in HUVECs were determined. Moreover, the binding between MIR4697HG and fused in sarcoma (FUS) was checked with RNA pull-down assay. The interaction between FUS and annexin A5 (ANXA5) was gauged with Co-immunoprecipitation. Then MIR4697HG/FUS/ANXA5 axis mediated HUVEC functions were accessed with rescue experiments. Additionally, an AS model was established via feeding a high-fat diet for ApoE-/- mice, and lentivirus MIR4697HG overexpression vector (Lv-MIR4697HG) was injected into AS mice followed by detection of atherosclerotic plaque area in mice. MIR4697HG was downregulated in atherosclerotic plaque tissues and HUVECs stimulated by ox-LDL. MIR4697HG overexpression attenuated ox-LDL-induced HUVEC viability inhibition, apoptosis, oxidative stress and adhesion molecule release. Moreover, MIR4697HG bound with FUS and facilitated FUS expression in HUVECs. FUS knockdown abrogated the functions of lncRNA MIR4697HG overexpression in ox-LDL induced HUVEC injury. Besides, FUS could bind with ANXA5. FUS overexpression inhibited ox-LDL induced HUVEC injury, while ANXA5 knockdown reversed these effects. Additionally, Lv-MIR4697HG reduced atherosclerotic plaque area in ApoE-/- mice. LncRNA MIR4697HG mitigated ox-LDL-induced apoptosis, oxidative stress and adhesion molecule release in HUVECs and alleviated AS progression in mice through the FUS/ANXA5 axis.

PM2.5 induces the abnormal lipid metabolism and leads to atherosclerosis via Notch signaling pathway in rats

PM2.5 can affect the lipid metabolism and cause atherosclerosis. Abnormal lipid metabolism is a sever risk factor of atherosclerosis and the underlying molecular mechanism still remains unclear. In this study, GPL16956 Agilent-045997 Arraystar human lncRNA microarray V3 (Probe Name Version) platform was used to detect the different genes of lipid metabolism between the normal arterial intima and advanced atherosclerotic plaque, which were downloaded from GEO database. A high-fat diet and vitamin D3 were administered to Wistar rats to establish the atherosclerotic model and another normal healthy 56 rats were used as the non-atherosclerotic exposure groups. The atherosclerotic rats and non-atherosclerotic rats were randomly divided into 4 PM2.5 groups (0, 1.5, 7.5, 37.5 mg/kg), respectively. The results of bioinformatics showed changes in the Notch1, Dll1, Hes1, LDLR and ABCG1 levels. PM2.5 exposure could produce damage to the physiological structure of the aorta, and aggravate atherosclerosis in rats from both non-atherosclerotic and atherosclerotic groups. With the increase of the exposure dose, the levels of TC and TG significantly increased. PM2.5 exposure significantly affected the expression levels of PPARγ, ABCA1, LDLR, CD36, SR-BI and SREBP2. PM2.5 exposure could also affect the expression levels of the Notch signaling pathways which was significantly correlated with the levels of TC and TG. The results proved that PM2.5 exposure could induce and aggravate the atherosclerosis in rats by disrupting lipid metabolism in which Notch signaling pathway may play a significant role.

CCL19-CCR7-dependent reverse transendothelial migration of myeloid cells clears Chlamydia muridarum from the arterial intima.

Regions of the normal arterial intima predisposed to atherosclerosis are sites of ongoing monocyte trafficking and also contain resident myeloid cells with features of dendritic cells. However, the pathophysiological roles of these cells are poorly understood. Here we found that intimal myeloid cells underwent reverse transendothelial migration (RTM) into the arterial circulation after systemic stimulation of pattern-recognition receptors (PRRs). This process was dependent on expression of the chemokine receptor CCR7 and its ligand CCL19 by intimal myeloid cells. In mice infected with the intracellular pathogen Chlamydia muridarum, blood monocytes disseminated infection to the intima. Subsequent CCL19-CCR7-dependent RTM was critical for the clearance of intimal C. muridarum. This process was inhibited by hypercholesterolemia. Thus, RTM protects the normal arterial intima, and compromised RTM during atherogenesis might contribute to the intracellular retention of pathogens in atherosclerotic lesions.

Long Noncoding RNA HOXC-AS1 Suppresses Ox-LDL-Induced Cholesterol Accumulation Through Promoting HOXC6 Expression in THP-1 Macrophages.

Atherosclerosis is a common pathological basis of cardiovascular disease, which remains the leading cause of mortality. Long noncoding RNAs (lncRNAs) are newly studied non-protein-coding RNAs involved in gene regulation, but how lncRNAs exert regulatory effect on atherosclerosis remains unclear. In this study, we found that lncRNA HOXC cluster antisense RNA 1 (HOXC-AS1) and homeobox C6 (HOXC6) were downregulated in carotid atherosclerosis by performing microarray analysis. The results were verified in atherosclerotic plaques and normal arterial intima tissues by quantitative reverse transcription PCR and western blot analysis. Lentivirus-mediated overexpression of HOXC-AS1 induced HOXC6 expression at mRNA and protein levels in THP-1 macrophages. Besides, oxidized low-density lipoprotein (Ox-LDL) decreased expression of HOXC-AS1 and HOXC6 in a time-dependent manner. Induction of cholesterol accumulation by Ox-LDL could be partly suppressed by overexpression of HOXC-AS1.

Expression change of proteasome core subunits in human atherosclerotic plaques

Objective To explore the relationship of atherosclerotic plaques with the component and function of proteasome complex by systematically investigating the protein levels of proteasome core subunits in human atherosclerotic plaques. Methods Clinical data of the observation group (patients with carotid artery stenosis undergoing carotid artery endarterectomy) and control group (patients with aortic dissection who underwent aortic replacement) were collected. The carotid endarterectomy specimens including the carotid atherosclerosis plaques and endometrial tissues adjacent to plaques were removed from 5 patients in observation group, and the relatively normal arterial intima(subclavian artery and innominate artery)were taken from 5 patients in control group. The protein levels of the proteasome subunits were measured by Western blotting. Results There was no significant difference in the occurrences of diabetes, hyperlipidemia and smoking between the two groups (χ2=0.61, 1.67 and 1.67, all P>0.05). Compared with the control group, the observation group showed that the levels of two non-catalytic β subunits β3 and β4 (F=56.576 and 27.846, both P<0.05), and the catalytic subunits β1 and β5 (F=8.221 and 82.716, both P<0.05) were significantly down-regulated in the plaques, whereas the expressions of β1i and β5i in the plaques (F=50.167、229.743, P<0.05) were robustly elevated. Conclusions The levels of the catalytic subunits of immune proteasome β1i and β5i are up-regulated in the atherosclerotic plaques, which indicates that the transformation from the constitutive proteasomes (β1 and β5) to the immune-proteasomes (β1i and β5i) is highly involved in the atherosclerosis. Key words: Atherosclerosis; Proteasome endopeptidase comples

Abstract 550: Hypercholesterolemia Inhibits LPS-Induced CCR7-Dependent Reverse Transmigration of Arterial Intimal Dendritic Cells.

Dendritic cells (DCs) play a key role in chronic inflammatory diseases such as atherosclerosis. Myeloid cells with features of DCs are abundant in the normal arterial intima of mice, in regions that are predisposed to atherosclerosis. Upon induction of hypercholesterolemia, these intimal DCs rapidly engulf lipids and transform into the initial foam cells of nascent atherosclerotic lesions. The function of intimal DCs in normal mice remains unknown. We observed that systemic stimulation of toll-like receptors (TLRs), specifically TLR4 by LPS and TLR3 by Poly(I:C), induced a rapid reduction in the number of DCs in the normal aortic intima. Absence of TUNNEL staining and use of CD11c-hBcl2 transgenic mice suggested that apoptosis did not account for the loss of intimal DCs. Immuno-gold staining for CD11c coupled with scanning electron microscopy of the aortic surface and ex vivo experiments determined that reverse transmigration (RTM) through the intact endothelial monolayer accounts for LPS-induced reduction of intimal DCs. Intimal DC loss was blocked by pretreatment of wild type mice with pertussis toxin or function-blocking anti-CCL19 antibody, and did not occur in CCR7-/- and Plt (CCL19-/- and CCL21-/-) mice. Assessment of CCR7, CCL19, and CCL21 mRNA expression and reciprocal bone marrow transplantation between CCR7-/- or Plt and wild type mice confirmed that RTM is dependent on CCR7 and CCL19 expression by intimal DCs. Feeding LDLR-/- mice a cholesterol rich diet (CRD) for just one week induced foam cell formation and inhibited LPS-induced RTM; however, CCR7 and CCL19 mRNA induction by LPS was not inhibited. These findings suggest that in the normal mouse aorta, in response to inflammatory stimuli, RTM of RIDCs is dependent on CCR7 signaling; whereas in the setting of hypercholesterolemia, CCR7 signaling is altered in lipid-loaded intimal DCs, which inhibits their RTM. Future experiments will investigate the possibility to overcome this inhibition, so that lipid can be removed from the artery wall by exiting lipid-loaded RIDCs.

THE EXPRESSION OF THE PROTEASOME EACH SUBUNIT IN HUMAN ATHEROSCLEROTIC PLAQUE

ObjectivesTo evaluate the expression of the proteasome each subunit in human atherosclerotic plaque.MethodsIn carotid endarterectomy specimens from 16 carotid stenosis patients as the case group, that divided into the plaque...

Expression of proteasome β5 subunit in human atherosclerotic plaque

To evaluate the expression of proteasome β5 subunit in human atherosclerotic plaque. The specimens of carotid endarterectomy were collected from 16 carotid stenosis patients. For the case group, they were divided into 2 groups: plaque (group A) and areas adjacent to plaque (group B). And carotid endarterium was obtained from 6 patients undergoing aortic replacement surgery. Relatively normal arterial intima (subclavian artery & innominate artery) was selected as the control group (group C). Content of proteasome β5 subunit was evaluated by hematoxylin & eosin (HE) staining, immunohistochemistry and Western blot. (1) In patients with diabetes, hyperlipidemia and probable smoking, proteasome β5 subunit was enhanced in all groups; (2) Proteasome β5 subunit was demonstrated in both cytoplasm and nucleus of vascular smooth muscle cells, but mainly confined to cytoplasm; (3)The positive expression rate of β5 was 9/16 in group A, 11/16 in group B and 6/6 in group C. There was significant divergence in the expression of β5 in different sample sub-groups: group A (atherosclerotic plaque) < group B (areas adjacent to plaque) < group C (control group). The expression of β5 decrease markedly in human atherosclerotic plaques.

The expression of the proteasome β5 subunit in human atherosclerotic plaque

ObjectiveProteasome is a mutiple-unit protease working on non-lysosomal protein degradation in cells. Recent studies have illustrated its potential roles in the whole process of atherosclerosis including endothelial dysfunction, formation of...

Atherosclerosis and complement: anaphylatoxin C5a as a new risk marker and therapeutic target

The complement cascade is activated within atherosclerotic plaques Activation of the complement system is a major aspect of many chronic inflammatory diseases. Thus, it is not surprising that several lines of evidence suggest that the complement system may also be involved in the pathogenesis of athero sclerosis. The complement system consists of several inactive zymogens that, upon activation, assemble with other components and are converted into active proteases or effector compounds. The complement cascade can be divided into the following three sequential steps: initiation of complement activation by the classical, alternative or the lectin pathway; complement amplification by activation of C3 and C5 convertases; and the effector functions of the terminal pathway, consisting of the terminal complement complex (TCC) C5b-9 and the proinflammatory anaphylatoxins C3a and C5a. A major activator of the classical complement pathway within atherosclerotic plaques is C-reactive protein (CRP) whose effects are pronounced after binding to enzymatically modified LDL, oxidized LDL or apoptotic cells. The classical pathway may also be activated by autoantibodies against oxidized LDL and against heat shock proteins. The alternative pathway is activated by enzymatically modified LDL, apoptotic cells and cellular debris, as well as free cholesterol crystals that can be found within the necrotic core of an atherosclerotic lesion. In addition, Chlamydia pneumoniae may contribute to complement activation by the lectin pathway and coagulation factors could directly activate C3 and C5. Normal arterial intima is free from activated complement; however, when fatty streaks are formed in cholesterol-fed rabbits, complement

Resident intimal dendritic cells and the initiation of atherosclerosis

To highlight the fact that regional differences in the normal arterial intima are critical to atherosclerotic lesion formation driven by systemic risk factors. At arterial curvatures, bifurcations and branches unique hemodynamics influence endothelial cell signaling and gene expression patterns, which create a proinflammatory environment, with low-grade recruitment of monocytes and accumulation of cells with dendritic features in the intima. Upon induction of hypercholesterolemia, these resident intimal dendritic cells initiate atherosclerosis by rapidly engulfing lipid and becoming the first foam cells in nascent lesions. This step precedes endothelial cell activation and increased monocyte recruitment. The unique features of the arterial intima at atherosclerosis-susceptible sites do not lead to disease under normal physiological conditions, but this intimal environment promotes the initiation of atherogenesis upon induction of systemic risk factors such as hypercholesterolemia.

Analysis of arterial intimal hyperplasia: review and hypothesis

BackgroundDespite a prodigious investment of funds, we cannot treat or prevent arteriosclerosis and restenosis, particularly its major pathology, arterial intimal hyperplasia. A cornerstone question lies behind all approaches to the disease: what causes the pathology?HypothesisI argue that the question itself is misplaced because it implies that intimal hyperplasia is a novel pathological phenomenon caused by new mechanisms. A simple inquiry into arterial morphology shows the opposite is true. The normal multi-layer cellular organization of the tunica intima is identical to that of diseased hyperplasia; it is the standard arterial system design in all placentals at least as large as rabbits, including humans. Formed initially as one-layer endothelium lining, this phenotype can either be maintained or differentiate into a normal multi-layer cellular lining, so striking in its resemblance to diseased hyperplasia that we have to name it "benign intimal hyperplasia". However, normal or "benign" intimal hyperplasia, although microscopically identical to pathology, is a controllable phenotype that rarely compromises blood supply. It is remarkable that each human heart has coronary arteries in which a single-layer endothelium differentiates early in life to form a multi-layer intimal hyperplasia and then continues to self-renew in a controlled manner throughout life, relatively rarely compromising the blood supply to the heart, causing complications requiring intervention only in a small fraction of the population, while all humans are carriers of benign hyperplasia. Unfortunately, this fundamental fact has not been widely appreciated in arteriosclerosis research and medical education, which continue to operate on the assumption that the normal arterial intima is always an "ideal" single-layer endothelium. As a result, the disease is perceived and studied as a new pathological event caused by new mechanisms. The discovery that normal coronary arteries are morphologically indistinguishable from deadly coronary arteriosclerosis continues to elicit surprise.ConclusionTwo questions should inform the priorities of our research: (1) what controls switch the single cell-layer intimal phenotype into normal hyperplasia? (2) how is normal (benign) hyperplasia maintained? We would be hard-pressed to gain practical insights without scrutinizing our premises.

The involvement of matrix glycoproteins in vascular calcification and fibrosis: an immunohistochemical study.

Calcification and fibrointimal proliferation are associated with advanced complicated atherosclerosis in large arteries but may also occur in smaller vessels, resulting in ischaemic tissue necrosis. This study investigates whether the mechanisms of calcification and intimal fibrosis are similar in vessels of different sizes. The localization of osteopontin (OPN), matrix Gla protein (MGP), thrombospondin-1 (TSP-1), and cartilage oligomeric matrix protein (COMP) was investigated in three types of human vascular lesions: atherosclerosis, chronic vascular rejection (CVR) in renal allografts, and calcific uraemic arteriolopathy (calciphylaxis). These lesions were chosen as they affect different sized blood vessels and they exhibit a fibroproliferative intimal reaction, with or without calcification, resulting in luminal obliteration and ischaemic complications. OPN, MGP, TSP-1, and COMP were not detected in normal blood vessels. However, OPN and MGP were expressed at sites of calcification within atherosclerotic lesions and in microvessels in calciphylaxis, suggesting that calcification in different sized vessels may occur by a common mechanism. These proteins were not detected in areas of fibrointimal proliferation. In contrast, TSP-1 was localized primarily within the fibrous tissue of atherosclerotic lesions and was also expressed in the expanded fibrous intima of arteries showing CVR. COMP was localized primarily within the fibrous tissue under the lipid core of the majority of advanced atherosclerotic lesions. TSP-1 and COMP were also detected in areas of microcalcification in atherosclerotic lesions and TSP-1 was detected adjacent to areas of calcification in calciphylaxis. However, neither TSP-1 nor COMP was localized to calcific foci within these lesions. The localization of OPN, MGP, TSP-1, and COMP to pathological, but not normal arterial intima supports a pathogenetic role for these proteins in the development of vascular fibrosis and calcification. Modulation of their production and activity may offer a novel approach to the therapy of a number of vascular diseases.

Pseudoaneurysm of the descending aorta caused by Candida albicans

Infection of normal arterial intima is very uncommon [1]. Staphylococcus aureus and Salmonella species are the two most common organisms associated with microbial arteritis and pseudoaneurysm formation; Candida arteritis is extremely rare, occurring in less than 1% of all reported cases [2]. Infection with candida is the result of hematogeneous dissemination in patients with impaired cellular immunity [3]. A pseudoaneurysm results from initial hematogeneous seeding of an injured or diseased intima, often by atherosclerosis with endothelial colonization followed by an invasive arterial infection; the arterial wall subsequently weakens with pseudoaneurysm formation [3]. The clinical presentation of patients with pseudoaneurysm or mycotic aneurysm of major arteries is pain in the aneurysm location and clinical bacteriemia signs. An elevated sedimentation rate and leukocytosis are common, but blood cultures are frequently negative [4]. Diagnosis, once suspected, should be pursued vigorously because rupture of such an aneurysm is often fatal [5]. Lifelong antifungal therapy following surgical repair may be necessary to treat these life-threatening infections [6]. A 35-year-old man with a history of intravenous drug abuse was admitted to the hospital with persistent fever and a mucocutaneous candida infection episode three months before the episode described here: the infection cleared without treatment. The patient had suffered from fever with chills and sweats, asthenia, productive cough and chest pain for about 15 days. His physical examination was remarkable for a fever of 39°C, respiratory rate of 25 breaths per minute, blood pressure of 135/80 mmHg and signs of peripheral venous puncture. No mucocutaneous candida infection was found. There were no murmurs on cardiac auscultation. The white blood cell count was 20×109 with neutrophilia, while haemoglobin and platelet counts were normal. The erythrocyte sedimentation rate was 66 mm/h. Chest X-ray showed a left para-hiliar pneumonia and antibiotic treatment with amoxicillin—clavulanic acid was started. Blood, urine and sputum cultures showed no growth for any organims. Human immunodeficiency virus-1 antibody test was negative. Computer tomography revealed a pseudoaneurysm arising from the thoracic descending aorta near the left pulmonar artery and contiguous parenchymatous consolidation consistent with asociated pneumonia in the lower lobe left lung. The patient suffered a massive hemoptysis. He was intubated and kept under mechanical ventilation and subseqently referred to our hospital. Transesophageal echocardiography showed no valvular vegetations, but an aortic pseudoaneurysm arising from the thoracic descending aorta and located 10 cms distal to the subclavian artery. This false aneurysm had an initial echolucent cavity 3×3 cms, connected to the aortic lumen and surrounded by 9×9 cms cavitated tissue mass, consistent with subacute thrombus formation (Fig 1). Color doppler showed flow within the echocardiographic cavities (Fig 2). The patient underwent urgent surgery. A perforated psudoaneurysm was found at the descending aorta, with invasion of lung tissue. The visualized aorta was free of atherosclerotic debris. False aneurysm resection, necrotic tissue debridement and patch repair of the descending aorta was performed. Cultures of the surgical specimen of aorta grew Candida albicans. Postoperatively he was treated with intravenous vancomicin A and amfotericin B (liposomal). The patient recovered and 6 months later is well.

Fibrinogen, fibrin and the arterial wall.

Virtually all plasma proteins, including fibrinogen, low density lipoprotein and lipoprotein(a), are present in normal arterial intima and in atherosclerotic lesions, and their concentrations are related to plasma concentrations. Fibrin is also a significant component of many lesions, particularly early proliferative (gelatinous) lesions, where it may be muscle cells migrate and proliferate, bind thrombin, and are a source of fibrin degradation products (FDPs), which are mitogenic. Very recent studies suggest that free a-thrombin may be present in lesions despite an apparent excess of antithrombin III, so this may promote fibrin formation within the lesion. Furthermore, fibrinolysis and FDP generation may be mediated by catheptic enzymes in addition to plasmin.

Ultrastructural recognition of cells with dendritic cell morphology in human aortic intima. Contacting interactions of Vascular Dendritic Cells in athero-resistant and athero-prone areas of the normal aorta.

Analysis of serial ultrathin sections of the human aortic intima detected a new cell yet to be described in the literature. These cells, which we have designated Vascular Dendritic Cells, appeared in contact with each other and with other intimal cells. Vascular dendiritic cells are characterised by ultrastructural features similar to those of dendritic cells, including a well developed smooth endoplasmic reticulum and the presence of several processes which were 3-5 or more times in excess of the size of the cell body. In areas of the normal aorta resistant to atherosclerosis, vascular dendritic cells were mainly localised in the subendothelial layer where they contacted both endothelial cells and smooth muscle cells. In areas of the normal aorta predisposed to atherosclerosis, vascular dendritic cells were distributed throughout the intima and the cellular interactions were altered with the vascular dendritic cells, developing multiple contacts with monocyte/macrophages and lymphocyte-like cells. Aortic areas predisposed to atherosclerosis showed the destruction of some vascular dendritic cell processes where they apposed endothelial cells. We speculate that vascular dendritic cells (VDCs) are a variety of dendritic cell and are involved in the maintenance of homeostasis in normal arterial intima. Vascular dendritic cells may be important in the development of atherosclerotic lesions, possibly through an immune mechanism.

Relative distribution of fibronectin and type I, III, IV, V collagens in normal and atherosclerotic intima of human arteries

Spatial distribution of fibronectin and type 1, III, IV and V collagen has been investigated in normal arterial intima, fatty streaks, and atherosclerotic plaques by indirect immunofluorescence on transverse sections. Two distinct types of extracellular matrix were revealed in atherosclerotic lesions. The fibrous plaques consisted mostly of interstitial collagen types I and III, contained moderate amounts of type V and none of type IV collagen or fibronectin. In the extracellular matrix of the fatty streaks and in some areas of the fibrous plaques containing large amounts of subendothelial cells, some interstitial collagen was revealed, an increased amount of type IV, some type V collagen and a lot of fibronectin. Similarities of the extracellular matrix in atherosclerotic lesions and granulation tissue are discussed.