Thorax 1986;41:355-359 Concentration, biosynthesis and degradation of collagen in idiopathic pulmonary fibrosis

ABSTRACT 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) Mg/mg dry weight, p < 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) pg of collagen degraded per mg of collagen incubated, p < 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. There has been renewed interest in the pathogenesis of diffuse interstitial pulmonary fibrosis in the last few years, with the publication of several studies in human subjects,I-5 and the development of many experimental models in various species using different agents.6-10 Idiopathic pulmonary fibrosis (fibrosing alveolitis), a prototype of interstitial lung diseases, is character-ised by interstitial and alveolar inflammation with considerable abnormalities in the pulmonary paren-chyma. Although several morphological, biochem-ical, and immunological studies have been carried out with different techniques, the mechanisms responsible for the derangement of interstitial connective tissue, mainly collagen, and for the ultimate distortion of the normal lung architecture remain unknown. To understand this complex problem better, we have studied simultaneously the concentration, bio-synthesis, and degradation of collagen in lung tissue of patients with IPF and compared the results with those obtained from normal lung