GROWTH-FACTORS ALTER NEONATAL TYPE-II ALVEOLAR EPITHELIAL-CELL PROLIFERATION

The type II alveolar epithelial cell plays a critical role in the repa ir of lung injury by repopulating the entire damaged alveolar epitheli um. We report our studies of the effects of known growth factors on th e in vitro proliferation of isolated neonatal rabbit type II cells. Tr ansforming growth factor-alpha (TGF-alpha) and epidermal growth factor (EGF)increased [H-3]thymidine incorporation, cell number, and labelin g index above control. Transforming growth factor-beta (TGF-beta) decr eased [H-3]thymidine incorporation, cell number, and labeling index co mpared with control. When added simultaneously, TGF-beta blocked the s timulatory effect of TGF-alpha or EGF. If TGF-alpha is added before TG F-beta, the ability of TGF-beta to block the mitogenic effect of TGF-a lpha was diminished the later in time TGF-beta was added. If TGF-beta was added first, later addition of TGF-alpha had no effect. The curren t work demonstrates that specific growth factors, including some known to be produced by other lung cells, alter the proliferation in vitro of isolated neonatal rabbit type II alveolar epithelial cells.