The fetomaternal interface shows vascular hypoglycosylation in the tammar wallaby Macropus eugenii: Comparison with a range of non-mammalian and eutherian placentae

Abstract Introduction Blood vessel glycosylation at the fetomaternal interface of four near-term specimens of tammar wallaby, Macropus eugenii , has been examined at days 23–26 of the 26.5 day pregnancy and compared with that of other species. Methods A panel of 23 lectins was used to compare vasculature in tammar with non-mammalian (shark, skink) and eutherian species at early and late gestation (camel, horse and alpaca), and term/near-term (cat, lion, dog, mink and elephant). Results Strikingly low levels of all the glycans tested, apart from sialic acids, were found in capillary endothelium of both the trilaminar omphalopleure and underlying surface endometrium of the tammar, though deeper endometrial vessels showed normally high levels of glycosylation. Only maternal vasculature of the mink placenta showed a comparable lack of expression. Discussion One reason for a reduced endothelial glycocalyx may be to facilitate diffusion of gases and nutrients as the tammar trophoblast lacks the indentation by overlying vessels that is seen in the other near-term placentae. Early epitheliochorial placentae of other species with equal diffusion distances to the tammar, showed normal vascular glycosylation. However, their pregnancies are much longer. Conclusion The hypoglycosylation of tammar vessels at the fetomaternal interface may allow continued transfer of nutrients and gaseous exchange during the extremely rapid period of organogenesis which occurs during the short 26.5 day pregnancy of this marsupial. Given the short gestation period of the tammar, we suggest that a thinner endothelial glycocalyx has evolved to facilitate diffusion of gases and nutrients between the maternal and fetal compartments.