TUMOR-NECROSIS-FACTOR-ALPHA AND EMBRYONIC MOUSE LUNG MORPHOGENESIS

The ontogeny of the embryonic and fetal lung involves complex interact ions between epithelial and mesenchymal primordia which require a spec ific program of gene regulation and signal transduction. Past studies in our laboratory using congenic mouse strains indicate that one or mo re genes which map to the H-2 region of chromosome 17 regulate the rat e of lung morphogenesis, defined in this context as differentiative he terochrony among strains. Since hormones and growth factors are the me ssengers of morphogenesis, it was logical to propose that tumor necros is factor-alpha (TNF-alpha), a well-characterized cytokine whose gene maps to the D-region of the H-2 complex, is a putative mediator of lun g morphogenesis. We investigated this proposition using immunochemical methods and a serumless, chemically defined in vitro model system. Ou r results demonstrate that: (1) TNF-alpha has a specific spatiotempora l localization, in vivo and in vitro; (2) TNF-alpha receptor, in vivo and in vitro, is localized throughout the embryonic lung; (3) TNF-alph a supplementation in vitro of embryonic lung primordia has a marked do se-dependent, stimulatory effect on branching morphogenesis and surfac tant-associated protein (SP-A) expression; (4) multiple immunoreactive proteins, including 17, 26, and 68 kDa species, are expressed during development in vivo, and a subset of these are expressed in vitro; and (5) both time- and glucocorticoid-dependent changes occur in the in v ivo expression pattern of TNF-alpha immunoreactive proteins after 4 an d 7 days in vitro, including the up-regulation of a novel 40 kDa prote in. Given that glucocorticoids (CORT) regulate TNF-alpha expression an d TNF-alpha's ability to stimulate pulmonary morphodifferentiation and histodifferentiation, we conclude that TNF-alpha is an autocrine/para crine pulmonary cytokine, probably a component of the lung morphogenes is pathway regulated by CORT. (C) 1994 Wiley-Liss, Inc.