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

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.