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 I, 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 tissues are discussed.     

Cell types involved in collagen and fibronectin production in normal and fibrotic human liver

Three collagen types (I, III and IV) and fibronectin were localized in normal and alcoholic human liver by light and electron microscopy using the indirect immunoperoxidase technique. In normal liver, most of the bundles of collagen fibers stained for type pro-III collagen while only a few reacted for type I. Basement membranes stained for type IV collagen which formed discontinuous discrete deposits in sinusoids. Only fibronectin appeared as an almost continuous layer in the space of Disse. At the intracellular level, hepatocytes were found to contain little type I collagen and large amounts of fibronectin. Fat-storing cells strongly stained for type IV collagen and expressed low amounts of types I and III collagen and fibronectin. Endothelial cells contained low amounts of all the components. Alcoholic livers were studied at three stages: steatosis, fibrosis and cirrhosis. Qualitative and quantitative differences were observed in extracellular and intracellular distributions of matrix proteins. Increased amounts of all components were usually found in fibrotic and cirrhotic livers compared to normal liver. In two fibrotic livers which contained numerous bundles of collagen in the sinusoids, fat-storing cells stained more intensely for type III collagen. In a cryptogenic fibrotic liver, abundant type IV collagen was observed in hepatocytes. These results suggest that hepatocytes, fat-storing cells and endothelial cells are engaged in production of extracellular matrix components in normal human liver. In fibrosis, hepatocytes which normally did not synthesize types III and IV collagen may produce these collagens.     

Participance of fibronectin and various collagen types in the formation of fibrous extracellular matrix in cardiosclerosis

Investigation of the extracellular matrix composition of the left heart ventricle was carried out on autopsy material of subjects, aged from 60 to 70 years, in a number of cases, including: (1) tissue without cardiosclerosis; (2) granulation tissue formed 2 weeks after infarction; (3) post-infarctial fibrous scars; (4) diffuse cardiosclerosis in consequence of stenotic coronary atherosclerosis. Cryostat sections treated with highly specific antibodies to fibronectin and types I, III, IV and V collagens were examined by the indirect immunofluorescence technique. Fibronectin and the mentioned collagenous proteins were detected in the extracellular matrix of granulation tissue. In contrast, fibronectin and collagen type IV were not revealed in post-infarctial fibrous scars. Collagen types III and V were diffusely distributed in fibrous tissue, whereas collagen type I was demonstrated to accumulate preferentially in the deeper regions of post-infarctial scars. Fibronectin and collagen types I, III, V, but never type IV, were also found in the connective tissue in diffuse cardiosclerosis. The significance of type V collagen in the extracellular matrix is discussed.     

Distribution of Extracellular Matrix Proteins in Indomethacin-Induced Lesions in the Rat Stomach

Introduction: We investigated the distribution of extracellular matrix (ECM) proteins in indomethacin-induced lesions of the rat stomach.

Method: Twenty rats received indomethacin orally at a dose of 8 mg/kg/body weight. The animals were killed at 3, 6, 12, 24, and 48 h after administration of the drug. The stomachs were removed and frozen in liquid nitrogen. Cryostat serial sections of the lesions were immunostained with antibodies to collagen 111, IV, and VI, laminin, and fibronectin.

Results: Fibronectin was the dominant extracellular protein of the provisional ECM in deep gastric lesions and gastric ulcers. Collagen III was strongly positive in stromal cells under the necrotic material in gastric erosions. Basal membrane proteins (collagen IV and laminin) were found to originate from the muscularis mucosae at the ulcer edge.

Conclusion: There is a typical distribution of ECM proteins in erosions and ulcers of the rat stomach. Fibronectin was most prominent in the provisional matrix of gastric erosions and ulcers.     

The Extracellular Matrix is an Integrated Unit: Ultrastructural Localization of Collagen Types I,III, IV,V, VI,Fibronectin, and Laminin in Human Term Placenta

The human term placenta is used extensively as a source of extracellular matrix components. To elucidate the tissue distribution and interrelationships of seven of these components, monospecific antibodies directed against collagen types I, III, IV, V, VI, fibronectin, and laminin were reacted with human term placenta and studied by light and electron immunohistochemistry.Type I collagen was the basic structural unit of human term placenta, present as 30\2-35 nm, cross-banded fibers, often in the form of large fiber bundles. Type III collagen was present as thin 10\2-15 nm, beaded fibers often forming a meshwork which encased type I collagen fibers. Types V and VI collagen were present as 6\2-10 nm filaments, often closely associated with types I and III collagen. Type VI collagen also coated collagen fibers of all diameters, enhancing their periodicity, providing a staining pattern often similar to that observed with anti-fibronectin antibodies. Fibronectin was present in both maternal and fetal plasma and throughout the stroma of the chorionic villus, as both free filaments and coating collagen fibers. Basement membranes contained laminin and type IV collagen, but no fibronectin. In summary, the non-basement membrane proteins studied often codistributed with type I collagen, between and apparently attached to fibers, suggesting that they may act as binding proteins, linking type I fibers and bundles, to themselves and to other structures.     

Changes in Gastric Mucosal Blood Flow during Healing of EMR-Induced Ulcer

Abstract: We used the laser Doppler method to study the difference in gastric mucosal blood flow changes between peptic ulcer (65 cases) and artificial ulcer caused by endoscopic mucosal resection (35 cases) during their respective healing processes. At each endoscopic ulcer stage, blood flow at the ulcer margin and that in the surrounding mucosa were measured. In the artificial ulcer, which heals easily, blood flow at the ulcer margin was still high at the scarring stage as compared with that in the corresponding area of a peptic ulcer, which is prone to relapse. Moreover, the blood flow ratio (blood flow at the ulcer margin/blood flow in the surrounding mucosa) at the S1 stage in artificial ulcers was significantly higher than that in peptic ulcers (p<0.05). These results suggest that blood flow in the SI stage is an important aspect of ulcer healing and relapse.     

Immunohistochemical study of extracellular matrix in acute galactosamine hepatitis in rats.

A single injection of D-galactosamine hydrochloride induces acute self-limiting liver disease in rats that morphologically resembles drug-induced hepatitis in human beings. In this immunohistochemical study we examined the localization and expression of the hepatic extracellular matrix components fibronectin, laminin, collagen type I, collagen type III and collagen type IV and of the cell surface receptors (integrins) for fibronectin and laminin. Sections of liver tissue obtained at intervals of 6, 12, 18, 24, 30, 36, 48 and 72 hr and 7 and 21 days after galactosamine administration were immunostained with a panel of polyclonal monospecific antibodies and studied independently by two of us. Fibronectin was the first extracellular matrix component found to be increased, 12 hr after galactosamine injection, followed by collagen type III, and, in a later phase, collagen type IV, type I and laminin. Increased deposition of extracellular matrix was found in areas with liver cell necrosis and along sinusoids. Extracellular matrix immunoreactivity reached a maximum at 36 to 48 hr and decreased thereafter to preinjury levels 3 wk after galactosamine. Immunostaining for the fibronectin and laminin receptors revealed tissue localization identical to that of their ligands. However, the intensity of staining was opposite of that for the extracellular matrix, with a decrease of immunoreactivity after 24 to 48 hr. The observed sequence of changes in hepatic extracellular matrix proteins after galactosamine injection resembles the repair reaction in other tissues and may reflect the particular function that each carries out during the process of liver healing after toxic injury.     

Nonsteroidal anti-inflammatory drugs and peptic ulcer disease

Evidence has accumulated that nonsteroidal anti-inflammatory drugs (NSAIDs) cause clinically important gastroduodenal ulcers. The pathogenesis, which involves the impairment of mucosal resistance to injury in an acid-peptic environment, is multifactorial and controversial. Ulcers caused by NSAIDs can occur either in mucosa inflamed because of infection with Helicobacter pylori or in histologically normal mucosa. The use of these drugs has been linked to an unexpectedly high incidence of ulcer complications, and a history of peptic ulcer disease is common in such cases. Nonsteroidal anti-inflammatory drugs thus appear both to exacerbate an underlying peptic diathesis and to cause de novo ulcers. The association between the use of these drugs and ulcer complications is supported by ulcer prevalence data from cross-sectional studies, and by data from case-controlled and cohort studies, and from randomized, experimental trials. Drug-induced gastric ulcers have been prevented by misoprostol, but not by H2 blocker therapy. Several therapies have been reported to promote ulcer healing despite continued use of NSAIDs, but adequate controlled trials have not been done. Small gastric and duodenal ulcers readily heal, whereas larger gastric ulcers require vigorous and prolonged therapy. The relative efficacies of various therapies in preventing ulcers, healing ulcers, or preventing complications remain to be established.     

Extracellular matrix in normal and fibrotic human lungs

Polyclonal affinity-purified antibodies to human collagen types I, III, and IV, and laminin were used to compare the extracellular matrix (ECM) in 10 normal and 32 abnormal lungs by indirect immunofluorescence. In normal lungs, type IV collagen and laminin codistributed in a uniform linear pattern along the epithelial and endothelial basement membranes. Type III collagen was found within the alveolar septa and interstitium in an interrupted ribbonlike pattern and was aggregated at the entrance rings of the alveoli. Type I collagen was distributed irregularly within the alveolar wall and was less prominent than type III collagen. In patients with pulmonary disease not characterized by interstitial fibrosis (n = 15), the distribution of ECM components studied was essentially normal. In pulmonary disease in which interstitial fibrosis was the characteristic feature, such as idiopathic pulmonary fibrosis (IPF) and adult respiratory distress syndrome (ARDS) (n = 17), collagen types I and III accumulated in the expanded interstitium. Type III collagen was initially predominant in the thickened alveolar septa and interstitium, whereas type I collagen appeared to be the principal collagen at later stages in the disease course. The basement membrane was disrupted early in the disease course with invasion of the alveolar spaces by interstitial collagens similar in type to those present in the adjacent interstitium.     

Isolation, characterization, and localization of cardiac collagen type VI. Associations with other extracellular matrix components.

We have isolated and characterized collagen type VI from murine, canine, and nonhuman primate hearts. In the three species studied, collagen type I was the major collagenous component of the cardiac interstitium (80% of total collagen), whereas collagen type VI represented approximately 5% of total collagen. To define the exact distribution of collagen type VI and its possible interactions with other components of the cardiac extracellular matrix, collagen types I, III, IV, and VI, laminin, and fibronectin were localized in the rat myocardium by immunohistochemistry, using monospecific antibodies. In the rat myocardium, collagen type VI was prevalent in the media and adventitia of muscular arteries, in fine connective tissue septa, in the area surrounding capillaries, and in the delicate endomysium in proximity to myocardial cells. When compared with the immunohistochemical localization of collagen types I, III, and IV, laminin, and fibronectin, the continuity and hierarchical organization of the cardiac extracellular matrix became apparent. The matrix forms a continuous network extending from the pericardium to the endocardium. Furthermore, there is an arborescent hierarchy in the system such that collagen type I is more prevalent in the wider septa, collagen type III being more obvious in medium-sized branches, and fibronectin and collagen type VI prevailing in the terminal (pericellular) aspects of the network. In this pericellular location, fibronectin and collagen type VI, by means of specific interactions, may act as anchor components linking the myocardial cell basement membranes not only to the extracellular matrix but also to the cardiac interstitial cells. This continuity, organization, and coupling of the cardiac extracellular matrix appears well suited to integrate and distribute the physical stress generated by the continuous contraction and relaxation of the myocardium.     

Flow cytometric analysis of cell proliferation kinetics during duodenal ulcer healing

Cell proliferation in the gastroduodenal mucosa of patients with duodenal ulcers was evaluated using flow cytometry. Forty patients with duodenal ulcers and 12 normal subjects were investigated. Biopsy samples were obtained during endoscopic examination and subjected to DNA analysis by flow cytometry. Thirty patients with duodenal ulcers were healed within 3 months with H₂ blockers (tractable or responsive ulcers), whereas 10 patients did not respond to treatment (intractable ulcers). The percentage of cells at the DNA-synthetic phase, an index of cell proliferation, was constant in the adjacent duodenal mucosa 2cm from ulcer margin and antral mucosa during duodenal ulcer healing. The index at the margin of tractable ulcers was elevated during the active stage (12.9 ± 1.3), peaked during the healing stage (15.4 ± 2.8) and returned to the same level at the scarring stage (10.9 ± 2.0) as normal controls (10.3 ± 1.7). However, the index was not elevated in intractable ulcers (10.3 ± 1.7 in the healing stage) and was smaller than in tractable ulcers. These data indicate that augmented mucosal cell proliferation at the ulcer margin plays an important role in duodenal ulcer healing and intractable ulcers are characterized by an abnormal failure to accelerate DNA synthesis to achieve ulcer repair.     

Literature Review on the Clinical Relationship between Ulcerative Jejunoileitis,Coeliac Disease,and Enteropathy-associated T-Cell Lymphoma

Background: The small interstitial proteoglycans decorin and biglycan have been shown to interact with various extracellular matrix molecules and with transforming growth factor-β. These interactions are proposed to be important for tissue repair, as the former interactions may affect the diameter and spacing of collagen fibrils, and the latter interaction the proliferation and differentiation of cells embedded in the matrix. The aim of this study is to localize these proteoglycans in the stomach and to investigate their suitability as potential markers of extracellular matrix activity in gastric lesions. Methods: Immunohis-tochemical techniques and in situ hybridization were used to study the phenotypic expression of these two proteoglycans in routinely processed specimens of human stomach tissue from 8 patients with gastric ulcer and 10 healthy control persons. Results: In normal gastric tissue, immunostaining for both proteoglycans was found in the interstitium, with a more pronounced staining in the pylorus region than in the corpus area. In addition, biglycan showed a strong staining of parietal cells. In specimens of healing gastric ulcers a larger deposition of decorin throughout scar tissue could be shown, and a higher expression of decorin was also found by in situ hybridization. Biglycan was only found at the edges of the lesions. Conclusion: This study shows for the first time the presence of decorin and biglycan in human gastric mucosa. We also showed that these proteoglycans may be involved in the gastric ulcer healing processes.     

Size of the peptic ulcer in Helicobacter pylori-positive patients: association with the clinical and histological characteristics

OBJECTIVE: Based on a large trial of Helicobacter pylori-positive peptic ulcer patients, we studied whether the size of the ulcer, along with other clinical and histological characteristics, has any effect on healing. We also studied the clinical and endoscopic characteristics associated with size of the peptic ulcer. MATERIAL AND METHODS: A total of 333 consecutive patients with H. pylori infection and peptic ulcer were enrolled (mean age 54.8+/-12.7 years). Location of the ulcer was recorded by gastroscopy and the presence of H. pylori was assured by rapid urease test, histology and by serum H. pylori IgG and IgA antibody measurement. The diameter of the ulcer was measured by placing the opened biopsy forceps (7 mm) beside it. Biopsy specimens were examined in accordance with the Sydney system. RESULTS: Mean size of the peptic ulcer was 13.2+/-8.3 in corpus, 11.3+/-5.3 in antrum, 13.8+/-7.8 in angulus, 9.5+/-5.3 in prepylorus and 9.2+/-4.7 mm in duodenum (duodenal versus gastric type; p<0.05). Average size of the ulcers was 9.4+/-5.3 mm in patients with Forrest III type and 11.5+/-6.8 in other types (p<0.05). Patients who were >or=50 years of age, currently smoking, or who had corpus-predominant chronic gastritis or atrophic gastritis, had larger ulcers than others. Size of index ulcers, successful eradication of H. pylori and the presence of atrophic gastritis were independent factors for healing. The odds ratio was 11.5 (95% CI 3.3-40.5; p<0.01) for eradication of H. pylori, 3.5 (95% CI 1.1-11.2; p<0.05) for size of the index ulcer (10 mm) and 3.4 (95% CI 1.2-9.8; p<0.05) for atrophic gastritis versus no atrophy. CONCLUSIONS: Size of the peptic ulcer, successful H. pylori eradication and atrophic gastritis were independent factors for the healing of peptic ulcers. A number of clinical and endoscopic variables (age, current smoking, corpus-predominant gastritis, Forrest classification) were associated with size of the peptic ulcer in H. pylori-positive patients.     

Current diagnosis and selection of patients for treatment of peptic ulcer disease

The introduction of fiberoptic endoscopy has altered the relative importance of ulcer symptoms in the diagnosis of peptic ulcer disease. Interestingly, we now realize that 50% of ulcer patients do not have the classical ulcer symptoms and that 25% of peptic ulcers are asymptomatic. Modern forward-viewing endoscopes of small diameter enable precise diagnosis with little discomfort in 95% of all duodenal ulcer patients. A biopsy is only recommended in rare cases (giant ulcers) because the malignancy rate is only 0.024% in duodenal ulcers. The diagnostic accuracy of endoscopy in detecting gastric ulcer is as high as that for duodenal ulcer, but for this ulcer type it is absolutely necessary to exclude malignancy by obtaining a minimum of six biopsies (four from the ulcer margin and two from the ulcer base), since approximately 10% of all gastric ulcers are actually carcinomas. Whereas in duodenal ulcer repeat endoscopy is seldom necessary, it is mandatory in gastric ulcer since ulcer healing is not proof of a benign ulcer. In experienced hands endoscopy is superior to radiography in duodenal and in gastric ulcer, although there is still a place for radiography as a supplementary investigation or if the patient rejects endoscopy. When selecting patients for treatment of peptic ulcer the following aspects must be considered: natural history of the disease, effectiveness of treatment, and risks and costs of treatment. Treatment goals (relief of symptoms, ulcer healing) can be achieved as far as the acute ulcer is concerned but as yet we have no evidence that we can cure chronic ulcer disease.     

Immunolocalization of collagen types, laminin and fibronectin in the normal human pancreas

In order to define the connective matrix organization of the normal human pancreas collagen types I, III, pro-III and IV, laminin and fibronectin were labeled using specific, antihuman antibodies. Visualization was by indirect immunofluorescence. Collagen types I, III and pro-III were present within lobules: around acini, ducts and small vessels. Their immunofluorescence reaction was particularly obvious in septa and it also outlined interlobular vessels and ducts. The type III and pro-III fractions possessed a characteristic, branched appearance in many situations, when compared to the more linear type I reaction. Collagen type IV, laminin and fibronectin were closely applied to acini, ducts and vessels, but in contrast to the other collagen types were absent from septa.     

Platelet adhesion to collagen and endothelial cell matrix under flow conditions is not dependent on platelet glycoprotein IV

Platelet membrane glycoprotein IV (GPIV) is a cell-surface glycoprotein that has been proposed as a receptor for collagen. Recently, it has been shown that platelets with the Naka-negative phenotype lack GPIV on their surface, whereas donors with this phenotype are healthy and do not suffer from hematologic disorders. In this study, we compared Naka- negative platelets with normal platelets in adhesion to collagen types I, III, IV, and V and the extracellular matrix of endothelial cells (ECM) under static and flow conditions. No differences in platelet adhesion and subsequent aggregate formation on the collagens types I, III, and IV were observed under static and flow conditions. Adhesion of both homozygous and heterozygous Naka-negative platelets to collagen type V was strongly reduced under static conditions. Collagen type V was not adhesive under flow conditions. No difference in platelet adhesion to ECM was observed, which suggests that GPIV is not important in adhesion to subendothelium, for which ECM may serve as a model. These results indicate that GPIV is not a functional receptor for collagen under flow conditions.     

Serum pepsinogen I concentrations in peptic ulcer patients in relation to ulcer location and stage.

To investigate the relation of the serum group I pepsinogen (PG I) concentration to the location of gastric ulcers and chronicity of peptic ulcers, ulcer patients (n = 322) were compared with endoscopically normal subjects (n = 174). The mean PG I concentration was significantly higher in male control subjects (n = 90) than in female control subjects (n = 84). In male patients with ulcers in the duodenum (n = 69), antrum (n = 34), or angulus portion (the lower third of the body; n = 83), the mean serum PG I concentration was significantly higher than in the control subjects but in patients with an ulcer in the upper body (n = 49) it was similar to control values. Men with active or healing ulcers (n = 149) showed a significantly higher serum PG I concentration than those with scarred lesions (n = 86) when the abnormality was located in either the upper body or in the angulus portion. For female patients (n = 87), the results were similar. These results suggest that serum PG I concentrations reflect the stages of activity of peptic ulcer.     

Omentum and basic fibroblast growth factor in healing of chronic gastric ulcerations in rats

Omentum was shown to exhibit angiogenic activity, but its role in healing of chronic gastric ulcers is unknown. This study was designed to compare the effects of omentum and basic fibroblast growth factor (bFGF), a potent angiogenic factor, on healing of chronic gastric ulcers in rats. Several series of rats with gastric ulcers were used: series A with intact omentum (control), series B with omentum resected, and series C with omentum placed on the serosal side of the ulcer. Series A–C were divided into four groups treated with vehicle (I); indomethacin (II), an inhibitor of prostaglandin formation, difluoromethylornithine (DFMO) (III); an inhibitor of polyamine biosynthesis or bFGF (IV). Seven days after ulcer induction, the animals were anesthetized, the gastric blood flow (GBF) was determined by laser Doppler flowmetry (LDF), and the ulcer area was measured by planimetry. Biopsy samples of the ulcer margin were taken for determination of the number of capillaries and myofibroblasts in the granulation tissue. Attachment of omentum significantly accelerated ulcer healing, whereas omentectomy delayed this process. LDF revealed the decrease in the GBF at the ulcer margin to 45% and at the ulcer bed to 18% of the value recorded in the intact adjacent mucosa. Attachment of the omentum significantly increased the blood flow at the ulcer margin and increased the number of capillaries and myofibroblasts in the granulation tissue. Indomethacin (1 mg/kg/day) that inhibited mucosal PGE₂ by about 85% delayed significantly ulcer healing without affecting the blood flow in the ulcer area. DFMO (200 mg/kg intraperitoneally) suppressed ODC activity in the mucosa but did not influence the ulcer healing. bFGF given subcutaneously accelerated dose-dependently ulcer healing and stimulated angiogenesis to a similar extent as the attached omentum. We conclude that omentum enhances the ulcer healing in similar way as bFGF and that this effect is accompanied by the increased angiogenesis and blood flow in the ulcer area.     

Immunohistochemical expression of extracellular matrix proteins and adhesion molecules in pancreatic carcinoma.

BACKGROUND/AIMS: Carcinoma invasion and metastasis in general involve multiple steps including dynamic changes in the composition and structure of extracellular matrix proteins and cell surface receptors. In the present study, the usually highly invasive carcinoma of the pancreas was investigated regarding the expression of various extracellular matrix proteins and their corresponding integrin receptors, as well as E-cadherin. METHODOLOGY: Phenotypic expression of various markers was investigated immunohistochemically in frozen sections of 16 pancreatic carcinomas and normal pancreatic tissue. RESULTS: An irregular and discontinuous deposition of type IV collagen and laminin in the basement membrane was found in cancer tissue and a pronounced desmoplastic reaction with deposition of type I, type III, and type IV collagen in the tumor stroma. In contrast, the noninvolved pancreas showed an intact basement membrane and a sparse stroma. The collagen type IV and laminin receptors alpha 2, alpha 3, and beta 1 integrin subunits were expressed on pancreatic cancer cells but not the alpha 6 integrin subunit normally present on epithelial cells, suggesting anchorage independence of the carcinoma cells. An increased capacity for cancer cell motility was suggested by the abundant expression of the "antiadhesive" extracellular matrix proteins, tenascin and vitronectin close to the cancer cells, and the expression of cell surface receptors such as alpha v (vitronectin-binding). Expression of the alpha 4 integrin subunit was also increased on cancer cells. CONCLUSIONS: The distribution of extracellular matrix proteins and the cell surface immune phenotype differed in pancreatic carcinoma as compared to normal pancreatic tissue. The present findings substantiate the notion that disseminated growth of highly malignant carcinomas of the pancreas reflects an invasive interaction of the tumor cells with extracellular matrix proteins of a well-established stroma. Similar findings were observed regardless of tumor histology and patient survival time.     

Immunohistochemistry of the hepatic extracellular matrix in acute viral hepatitis

The distribution of several extracellular matrix components in the liver of patients with acute viral hepatitis was studied by light and electron microscopy using indirect immunoperoxidase methods. Light microscopy revealed type III and type V collagen and fibronectin in the portal tracts and the area of focal necrosis, showing cell infiltration. Type III and type V collagen were more strongly stained in the periphery of focal necrosis. Type IV collagen was seen around the vessels and hepatocytes near the focal necrosis. Electron microscopy showed many transitional Ito cells in the area of focal necrosis and fibroblasts were observed in the portal tracts, showing collagen fiber deposition. Numerous collagen fibrils were observed around fibroblasts, Ito cells and hepatocytes. Using immunoelectron microscopy, type III and type IV collagen and fibronectin were observed in the rough endoplasmic reticulum of Ito cells and hepatocytes localized near the area of focal necrosis or fiber deposition. In addition, type IV collagen was seen in the rough endoplasmic reticulum of endothelial cells forming capillary vessels. These results suggest that several extracellular matrix components such as types III, IV and V collagen and fibronectin, produced by Ito cells, hepatocytes or endothelial cells, play important roles in the healing of liver damage in acute viral hepatitis.