Heparin and in-vitro experimental lung hypoplasia.
Pulmonary hypoplasia (PH) is a leading contributor to the lethality of congenital diaphragmatic hernia (CDH). Studies now suggest that PH arises prior to visceral herniation. Growth factors (GF) are pivotal to this embryonic lung growth. With striking in-vitro effects on lung morphogenesis, GF are under investigation as therapies for PH. Heparin modulates the kinetics of heparan-sulphate binding ligands that drive lung development. We hypothesised that heparin may rescue PH by favourable alteration of endogenous pulmonary GF activity. Normal and hypoplastic lung primordia were microdissected on day 13.5 of gestation and cultured for up to 78 h in plain media with and without heparin. In-vitro morphological development was studied by serial measurements of terminal bud count, lung area, and lung perimeter. Nitrofen-exposed lungs cultured with heparin showed no significant improvements in terminal bud count, lung area, and lung perimeter at 30, 54, and 78 h compared to untreated hypoplastic lungs maintained in vitro. In normal lungs heparin demonstrated no sustained significant morphological effects compared to untreated control lungs. In this study, heparin did not stimulate branching morphogenesis of normal or hypoplastic lungs in our organ culture system. Known at higher concentrations to inhibit smooth-muscle proliferation, heparin may ameliorate pulmonary vascular hypermuscularisation with the prospect of benefiting CDH infants on extracorporeal membrane oxygenation. Future studies will address the impact of exogenous GF on hypoplastic lung development in organ culture.