Elsevier

Human Pathology

Volume 45, Issue 1, January 2014, Pages 160-165
Human Pathology

Original contribution
Different collagen types show distinct rates of increase from early to late stages of hepatitis C–related liver fibrosis

https://doi.org/10.1016/j.humpath.2013.08.015Get rights and content

Summary

During progression from normal liver to cirrhosis, total collagen increases nearly 10-fold with an abnormal increase in fibril-forming collagen and other extracellular matrix molecules. However, little is known regarding the changes each collagen type undergoes during fibrogenesis. We assessed the different collagen types by immunohistochemistry at various stages of hepatitis C–related liver fibrosis in core biopsies and compared changes in each with trichrome stain to better understand fibrogenesis. The possible utility in staging fibrosis was investigated. We found collagens III, IV, V, VI, vitronectin, and trichrome all showed statistically significant increases from early to late stages of fibrosis, but with temporal and quantitative differences. During the transition from early to late fibrosis, trichrome (stains primarily collagen I) and collagen IV showed the steepest increase and appear to be the most useful discriminators between early and late stages of fibrosis. Collagens V and VI have strong reactivity even in stage 1, which may be helpful in identifying early fibrosis when trichrome is weak or negative. Collagen III and vitronectin showed the most gradual increase. Interestingly, collagen V also showed increased staining in areas around inflammation/edema, which may overestimate established fibrosis as compared with trichrome.

Introduction

It is well known that during progression from normal liver to cirrhosis, significant changes occur in extracellular matrix. Total collagen increases nearly 10-fold with an abnormal increase in fibril-forming collagen and other extracellular matrix molecules [1], [2]. However, little is known regarding the changes each collagen type undergoes during fibrogenesis. To recognize quantitative and qualitative changes of extracellular matrix during fibrogenesis, it is important to understand the normal constituents in liver extracellular matrix.

Previous studies [3], [4], [5], [6] of normal rat and human liver have shown that collagen types I and III are the most abundant collagens present in the liver capsule, portal stroma, Disse space, and fibrous septa. Type IV collagen codistributes with laminin in all basement membranes of vessels and bile ducts, and there is also “free” type IV collagen that is not associated with laminin and distributed in the sinusoids as small, discrete, discontinuous deposits. Type V collagen is fine collagen fibrils that constitute the core of larger fibrils of collagens I and III. Type VI collagen is a nonfibril, network-forming collagen that dominates the subendothelial space. It functions as an important bridging molecule that anchors structures such as nerves, blood vessels, and other cells to the basement membrane collagen IV.

Numerous noncollagen glycoproteins are also present in the liver. Vitronectin is a glycoprotein found in normal serum and pathologic extracellular matrix, promoting cell adhesion, spreading, and migration [7]. Laminin is present in the basement membrane and endoplasmic reticulum of mesothelial cells. Fibronectin, a structural glycoprotein, is found in the liver capsule, portal stroma, and Disse space, but not in basement membranes. It mediates adhesion of collagen, fibrin, and heparin to cells. Elastin is present in the wall of blood vessels, in the capsule, and in long-standing fibrosis.

As the liver becomes fibrotic, all collagen types increase [1]. Of note, there is abnormal increase in fibril-forming collagens as well as other extracellular matrix molecules in the subendothelial space, leading to the pathologic transformation of the normal low-density base membrane–like matrix to the interstitial type [8]. We studied hepatic fibrosis using liver core biopsies to assess different collagen types and vitronectin by immunohistochemistry at various stages of hepatitis C–related liver fibrosis. Our goal is to gain a better understanding of hepatic fibrogenesis by comparing the changes of each collagen type and vitronectin at different stages of liver fibrosis.

Section snippets

Materials and methods

The research was approved by Ohio State University Institutional Review Board. Seventy-three liver core biopsies from hepatitis C patients during a 5-year period (2007-2012) were identified. Only liver cores with a total length of equal to or more than 2 cm were selected because previous studies showed optimal liver biopsy is > 2 to 2.5 cm long for accurate grading of the degree of fibrosis [9]. Staging was performed using the hematoxylin and eosin– and trichrome-stained slides and the Batts

Results

The 73 viral hepatitis C patients ranged from 48 to 55 years old, with male predominance in all stages (total 56 men and 17 women). As expected, immunohistochemical stains for collagens and vitronectin highlighted the periportal and intralobular fibrotic areas in the liver cores (Fig. 1, Fig. 2). Trichrome stain as well as collagens III, IV, V, VI, and vitronectin all showed increased interstitial staining from early to late stages of fibrosis. Interestingly, collagens IV and VI also showed a

Discussion

Despite the rapid development in hepatitis C treatment, our understanding regarding the change of each collagen type during fibrogenesis is still limited. We analyzed the expression profile of different extracellular matrix at various stages of liver fibrosis to assess their differential staining and utility in distinguishing early versus late liver fibrosis. We limited our study to hepatitis C–related liver fibrosis so that the changes in collagen expression were not compounded by various

Conclusions

Collagens III, IV, V, VI, vitronectin, and trichrome all showed statistically significant increases from early to late stages of fibrosis, but with temporal and quantitative differences. Collagen IV and trichrome appear to be the most useful discriminators between early and late stages of fibrosis, whereas collagens V and VI show the strongest expression in early fibrosis and, therefore, may help with its identification. Additional studies are warranted to evaluate the clinical utility of these

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Conflict of interest and funding disclosures. All authors: None.

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