Biomarker Insights

Background and aim: The current study utilized a carbon tetrachloride (CCl4)-induced liver fibrosis model to measure levels of the MMP9-mediated collagen type III degradation fragment CO3-610 (site of cleavage: KNGETGPQGP), during disease progression and regression, and to investigate a potential prognostic role of the biomarker.

Materials and methods: 72 female Sprague-Dawley rats aged 6 months old were injected with CCl4 twice a week over different periods of time to induce varying degrees of liver fibrosis. After 4, 6 and 8 weeks of treatment, administration of CCl4 was stopped. The 6- and 8-week treatment groups were left to regress for a further 6 or 12 weeks at which point they were sacrificed and livers removed and sectioned. Liver fibrosis was quantified using Visiopharm software to analyse Sirius red-stained sections. Serum levels of CO3-610 were measured in all animals using an ELISA assay as described by Barascuk et al.1

Results: Quantitative histology revealed total collagen deposition in the liver increased as fibrosis progressed. In animals treated with CCl4 for 4 weeks, collagen comprised on average 4.94% of the total tissue in liver sections, while after 6 weeks the mean was 8.25%, and after 8 weeks, 9.11%. During the regression phase, the total collagen deposition gradually decreased to a mean of 6.9% and 5.09% for animals regressing 6 and 12 weeks respectively after 6 weeks treatment, and 6.27% for animals regressed 12 weeks after 8 weeks treatment. CO3-610 values increased progressively in rats treated for 4 weeks (by a mean of 55.0 ng/ml), 6 weeks (mean 61.1 ng/ml) and 8 weeks (mean 70.2 ng/ml). During the regression phase, CO3-610 values rapidly decreased by a mean of 28.9 ng/ml at 6 weeks and 21.6 ng/ml at 12 weeks in animals previously treated for 6 weeks, and by a mean of 19.52 ng/ml in animals treated for 8 weeks and regressed for 12 weeks. CO3-610 levels were statistically significantly correlated with total collagen during disease progression (r = 0.5701, P < 0.0001). No statistically significant correlation was observed during regression (r = 0.2081, P = 0.1138).

Conclusion: Levels of the MMP-9 generated fragment of collagen type III, CO3-610, correlated with the degree of liver fibrosis in rats during the progression phase, but were not correlated with total collagen levels during regression. CO3-610 seems to be produced only under the CCL4 stimulus, and signifies CO3-610 as a potential marker of progression rather than regression. The corresponding steep elevations in levels of CO3-610 total collagen and collagen type III during liver fibrosis progression underline a potential prognostic capacity of the biomarker.