Regulation of extracellular matrix proteins by transforming growth factor β1 in cultured pulmonary endothelial cells

Transforming growth factor beta-1 (TGF-beta(1)), which is present in lung tissue, has been suggested to play a role in modulating vascular cell function in vivo. The action of TGF-beta(1) in vivo, especially at the local site of application to connective tissue, is anabolic and leads to pulmonary fibrosis and angiogenesis, strongly indicating that TGF-beta may have practical applications in repair of tissue injury caused by burns, trauma, or surgery. In the present study, we have used cultured bovine pulmonary artery endothelial (BPAE) cells as a model system. Expression of various proteins, including SPARC (secreted protein acidic and rich in cysteines), type IV procollagen and fibronectin (FN) was examined by radiolabeling the cells with [H-3]proline, immunoprecipitation with specific antibodies, and Northern blot analyses by using specific cDNA probes. Cultured cells were labeled with [H-3]proline for 24 h in either the absence or in the presence of TGF-beta(1) (0-20 ng/ml). Incorporation of radioactivity was observed in a concentration-dependent manner, maximal at 5 ng/ml. Northern blot hybridization demonstrated that TGF-beta(1) (5 ng/ml) treatment of BPAE cells caused an increase in steady-state levels of mRNA for SPARC (75%) and FN, thus, indicating a positive modulation. To determine whether TGF-beta(1) has an effect on cell proliferation in the cultures, the incorporation of [H-3]thymidine into cellular nuclei was used to measure DNA replication; 5 ng/ml had an inhibitory effect (42%) on cell proliferation. Protein production by TGF-beta(1), surprisingly, showed decrease in SPARC levels (42%) and in contrast increased levels of FN (86%) and type IV procollagen (334%). Our results indicate that on exposure to TGF-beta(1), cultured BPAE cells differentially change expression of extracellular matrix proteins which may be important in remodeling of tissue and healing at sites of injury. (C) 1999 Academic Press.