Thrombin-mediated cellular events in pulmonary fibrosis associated with systemic sclerosis (scleroderma).

The vascular hypothesis for the pathogenesis of systemic sclerosis was perhaps Professor LeRoy's most important scientific contribution. One early and important consequence of vascular injury is the release of activated thrombin. In this manuscript we present our data and review the current understanding of the role played by thrombin in the process of fibrosis, particularly as it relates to scleroderma lung disease. Thrombin's cellular effects are intimately involved in promoting myofibroblast differentiation, endothelial cell activation, extracellular matrix protein deposition, and the induction of important profibrotic factors. Such studies confirm that thrombin is one of the major mediators in the development and progression of pulmonary fibrosis. Therefore, targeting the major receptor of thrombin, PAR-I, and its downstream signaling molecules may lead to novel therapeutic approaches for the management of scleroderma lung fibrosis. We are indebted to Dr LeRoy for his many contributions to the field of scleroderma, and for all that he did to stimulate our interest in these studies.