Interactions among pulmonary surfactant, vernix caseosa, and intestinal enterocytes: intra-amniotic administration of fluorescently liposomes to pregnant rabbits

Although vernix caseosa is known to be a natural biofilm at birth, human pulmonary surfactant commences to remove the vernix from fetal skin into the amniotic fluid at gestational week 34, i.e., well before delivery. To explain this paradox, we first produced two types of fluorescently labeled liposomes displaying morphology similar to that of pulmonary surfactant and vernix caseosa complexes. We then continuously administered these liposomes into the amniotic fluid space of pregnant rabbits. In addition, we produced pulmonary surfactant and vernix caseosa complexes and administered them into the amniotic fluid space of pregnant rabbits. The intra-amniotic infused fluorescently labeled liposomes were absorbed into the fetal intestinal epithelium. However, the liposomes were not transported to the livers of fetal rabbits. We also revealed that continuous administration of micelles derived from pulmonary surfactants and vernix caseosa protected the small intestine of the rabbit fetus from damage due to surgical intervention. Our results indicate that pulmonary surfactant and vernix caseosa complexes in swallowed amniotic fluid might locally influence fetal intestinal enterocytes. Although the present studies are primarily observational and further studies are needed, our findings elucidate the physiological interactions among pulmonary, dermal-epidermal, and gastrointestinal developmental processes.