Mechanical forces modulate alveolar epithelial phenotypic expression

physical forces play an important role in modulating lung development. grow th, compliance, differentiation and metabolism. Both tonic distension and p hasic changes in volume occur during development and after birth. Morphomet ric studies have shown that alveolar epithelial cells are distended during lung expansion from functional residual capacity. In both in vivo and in vi tro model systems, mechanical distension stimulates surfactant secretion. D rawing on the results of developmental anomalies and experiments in vivo, w e and others have generated the underlying hypothesis that mechanical diste nsion promotes expression of the type cell phenotype and inhibits expressio n that of the type II; contraction has the opposite effects. The results of recent experiments, using both cultured type II cells from adult rodents a nd fetal lung explant tissue to test this hypothesis, provide support. The molecular and biochemical mechanisms by which physical forces affect lung f unctions are currently under investigation. (C) 2001 Elsevier Science Inc. All rights reserved.