EFFECT OF MECHANICAL FORCES ON GROWTH AND MATRIX PROTEIN-SYNTHESIS INTHE IN-VITRO PULMONARY-ARTERY - ANALYSIS OF THE ROLE OF INDIVIDUAL CELL-TYPES

The effect of mechanical stimuli on pulmonary artery growth and matrix tissue synthesis (and how individual cell types in the vessel wall re spond to such stimuli) is incompletely characterized. Rabbit pulmonary arteries were placed in tissue culture medium and subjected to varyin g magnitudes of stretch or hydrostatic pressure (separately) for 4 day s. The rate of protein synthesis in smooth muscle cells (by quantitati ve autoradiography) was positively related to the magnitude of stretch , as were the percentage of procollagen type I-positive cells and the rate of cell replication. In adventitial fibroblasts, stretch increase d the rate of replication but not of protein synthesis. Hydrostatic pr essure had little or no effect on the variables measured in either smo oth muscle cells or fibroblasts. Stretch also increased the rate of el astin and collagen synthesis in the whole pulmonary artery segment, an d after 4 days of stretch, the contents of actin and elastin were incr eased. Removal of the endothelium did not affect stretch-induced prote in, collagen, or elastin synthesis but augmented stretch-induced smoot h muscle replication. These data suggest that in the intact pulmonary artery, stretch, but not pressure, can stimulate hypertrophy and hyper plasia in smooth muscle cells and hyperplasia in fibroblasts. Matrix p rotein synthesis and accumulation are also increased by stretch. Neith er stretch-mediated growth nor matrix protein synthesis required endot helium in this model.