Concentration, biosynthesis and degradation of collagen in idiopathic pulmonary fibrosis.

Despite several studies both in vitro and in vivo, the pathogenesis of pulmonary fibrosis is unclear and some findings related to the biochemistry of collagen are controversial. Collagen metabolism was studied in 11 patients with idiopathic pulmonary fibrosis and in six control subjects. There was an increase in collagen concentration (mean 327 (SD 76) compared with control values of 185 (18) micrograms/mg dry weight, p less than 0.001), normal values for biosynthesis (mean 2.2% (0.8%) v 2.08% (0.5%), and a noteworthy decrease in collagenolytic activity (mean 0.07 (0.04) v 0.23 (0.04) micrograms of collagen degraded per mg of collagen incubated, p less than 0.001). These results suggest that an alteration in enzymatic breakdown of collagen plays an important role in the maintenance and progression of interstitial fibrosis in this disease.