Investigation of type I and type III collagens of the lung in progressive systemic sclerosis

The interstitial collagens, type I and type III, were investigated in lung tissue from patients with progressive systemic sclerosis (PSS) with pulmonary involvement. By use of CNBr digestion of whole tissue, the relative content of type I versus type III collagen was unchanged. This contrasts with idiopathic pulmonary fibrosis. Limited pepsin digestion released greater amounts of collagen (55%) than normal (16%), but the individual collagen chains were chemically indistinguishable. A reduced amount of the more stable collagen crosslink, hydroxylysinonorleucine, was observed which was consistent with the relatively greater degree of solubilization.