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The lung parenchyma--a dynamic matrix. J. Burns Amberson lecture.

The matrix of the lung parenchyma is composed predominantly of collagen, elastin, glycosaminoglycans, and fibronectin. This presentation focuses on the newer insights into injury and repair of lung elastin and glycosaminoglycans. Elastin and glycosaminoglycans respond in characteristic patterns to destructive and proliferative forms of lung injury. Elastin degradation induced by elastases induces a prompt and marked response by elastin resynthesis in situ. The signal for the stimulus remains unknown and deserves to be understood. The measurement of elastin peptides in plasma, urine, or bronchoalveolar lavage fluid can provide an objective index of elastin degradation in disease. Elastin depletion may be augmented by factors that interfere with elastin resynthesis such as exposure to tobacco smoke. Glycosaminoglycans participate in similar fashion in many different forms of lung injury as an early response to injury, which may then determine the subsequent cellular processes of repair. Studies of injury and repair in organ systems, other than the lung, suggest a general role for glycosaminoglycans in interstitial tissue and repair. The mediators that alter matrix chemical structure and function could provide powerful instruments for controlling the process of tissue injury and repair in the lung.