Two Assays for Measuring Fibrosis: Reverse Transcriptase–Polymerase Chain Reaction of Collagen α1 (III) mRNA Is an Early Predictor of Subsequent Collagen Deposition While a Novel Serum N-Terminal Procollagen (III) Propeptide Assay Reflects Manifest Fibrosis in Carbon Tetrachloride-Treated Rats

Abstract Using a novel quantitative reverse transcriptase–polymerase chain reaction assay, we have determined the amount of specific mRNA for procollagen α 1 (III) (PIIIP) in the carbon tetrachloride (CCl 4 ) model of liver fibrosis in rats. After a single week of CCl 4 application, the amount of PIIIP mRNA was increased approximately 10 times over the untreated control group and continued to increase to approximately 30 times after 7 weeks of intoxication. In this model substantial fibrosis was demonstrated by computer-aided morphometry after 5 to 7 weeks of treatment. Using recombinant murine N-terminal procollagen α 1 (III) propeptide (PIIINP), a novel sensitive immunoassay for the measurement of circulating PIIINP in rodent sera was established. An increase in PIIINP serum levels was observed after 5 to 7 weeks of CCl 4 intoxication. Our results suggest PIIIP gene expression is an early marker of tissue fibrosis. Early PIIIP gene expression is correlated with the extent of the subsequent fibrosis. PIIIP mRNA levels increase much earlier than conventional histological examination or PIIINP levels. PIIINP measurements with our new serum assay, on the other hand, are a good noninvasive marker of manifest fibrosis but are a poor marker of fibrogenesis.