Semiquantitative evaluation of hepatic fibrosis by measuring tissue hydroxyproline

It is important to evaluate the degree of hepatic fibrosis when diagnosing and treating hepatic cirrhosis. We focused on hydroxyproline, which is detected specifically in collagen, which plays a major role in hepatic fibrosis. The correlations between liver tissue hydroxyproline residue levels and the degree of hepatic fibrosis were examined in dogs with dimethylnitrosamine-induced fibrotic livers.

Dimethylnitrosamine was administered to dogs to establish experimental hepatic fibrosis. Paraffinized sections of liver specimens, stained with hematoxylin-eosin and azan, were examined and the degree of hepatic fibrosis was graded. About three-milligram samples of liver tissue were loaded onto a fully automated liquid chromatograph and the levels of hydroxyproline residues were measured.

The liver tissue hydroxyproline appeared to reflect the degree of hepatic fibrosis. The liver tissue hydroxyproline levels and pathological hepatic fibrosis grades correlated significantly (p<0.05).

Tissue hydroxyproline appears to be a more useful fibrosis marker, because hydroxyproline is influenced less by other factors. Furthermore, our results demonstrate that a very small amount of liver tissue (wet weight 3 mg) was enough to enable the levels of hydroxyproline residues to be measured by an automated amino acid analyzer (JLC-3000) and hepatic fibrosis is expressed as the numerical value by this analysis.