INFLUENCE OF EPIDERMAL GROWTH-FACTOR AND TRANSFORMING-GROWTH-FACTOR BETA-1 ON PATTERNS OF FETAL MOUSE LUNG BRANCHING MORPHOGENESIS IN ORGAN-CULTURE

Transforming growth factor-beta (TGF-beta), a potent inhibitor of epit helial cell proliferation, and epidermal growth factor (EGF), a mitoge nic polypeptide that binds to cell surface receptors, are important re gulators of cell differentiation; however, their distinct role(s) in l ung development and their mechanisms of action are not well understood . We evaluated the effects of these factors on lung morphogenesis in m urine fetal lungs at gestational day 14 (time:zero) and again after 7 days in culture. Baseline controls were cultured after tracheal transe ction in supplemented BGJb medium, and other tracheally transected lun gs were cultured following addition of EGF (10 ng/ml BGJb), TGF-beta(1 ) (2 ng/ml BFJb), or with both in combination added to the medium. The control lungs in culture had poorly developed airways and an absence of defined acinar structures. The addition of EGF resulted in hyperpla sia of primary airways with stunted outgrowths, monopodial branching, and absence of distinct acinar structures. Addition of TGF-beta(1) alo ne, led to significant elongation of primary airways, without normal a irway branching; however, terminal dipodial branching was seen and the prospective pulmonary acini were well defined. Combination of these g rowth factors (GF) resulted in a more normal branching pattern and dif ferentiation, suggesting their epigenetic role in lung morphogenesis a nd mutual interactive mechanisms that regulate lung development. These lungs had more abundant and larger lamellar bodies than those after o ther treatments. Control lungs remained immature with prominent glycog en aggregates with occasional dense lamellar bodies. The total protein and DNA contents were highest with EGF treatment, followed by combina tion treatment; these observations were supported by immunohistochemic al localization of proliferating cell nuclear antigen, an indication o f the proliferative state of tissues. All the surfactant proteins were relatively unaltered and their messages were up-regulated for SP-A, b ut down-regulated for SP-B and SP-C in the lungs treated with growth f actors. In conclusion, we have demonstrated enhanced biochemical and s tructural development of lungs treated in vitro with GF, and propose t hat further research in this area may lead to therapeutic uses of GF a lone or in combination with other agents for the treatment of newborn respiratory distress due to lung immaturity or hypoplastic lung develo pment. (C) 1998 Wiley-Liss, Inc.