The balance between collagen synthesis and degradation in diffuse lung disease

Diffuse interstitial lung disease (DLD) is characterised by varying degrees of inflammation and fibrosis that result in derangement of the gas-exchang ing units of the lung. A hallmark of these diseases is the abnormal deposit ion of collagen, which is a prime determinant of clinical course. This revi ew considers the current information concerning collagen turnover in diffus e fibrotic lung disease. Considerable experimental evidence implicates both increased collagen production and reduced degradation in these diseases. R educed degradation may result from both reduced production of collagenases and increased inhibition by tissue inhibitors. The known effects upon colla gen turnover of novel therapeutic agents for pulmonary fibrosis (pirfenidon e and interferon gamma) are discussed.