Unusual patterns of intermediate filament protein expression by the trophoblast and decidual cells of the short-tailed fruit bat, Carollia perspicillata

In the short-tailed fruit bat (Carollia perspicillata) pregnancy can be pro longed by the occurrence of lengthy delays after implantation. This is asso ciated with the development of highly invasive trophoblast that can penetra te the myometrium, mesenteries of the reproductive tract and the oviducts v ia perivascular (interstitial) routes. In order to confirm the identity and distribution of this trophoblast, intermediate filament protein immunocyto chemistry was utilized. In some respects the expression of these proteins d iffered from what has been reported for more commonly-studied species. Cyto trophoblast in the placenta, its cytohophoblastic shell and the highly inva sive trophoblast strongly expressed cytokeratins. As pregnancy progressed, however, cytokeratin expression by syncytiotrophoblast lining much of the p lacental labyrinth became very weak. The cytotrophoblastic shell and highly invasive trophoblast also expressed vimentin. The highly invasive trophobl ast was unusual in that it developed dendritic processes that sometimes ext ended out into adjacent tissues in great profusion. Decidual cells generall y expressed desmin and vimentin; however, some also coexpressed cytokeratin s. These observations indicate that some of the trophoblast in Carollia und ergoes a significant epithelial-mesenchymal transformation. They also sugge st that caution should be exercised in relying upon intermediate filament p roteins as markers for cell identification purposes in exotic species, or w hen the patterns of protein expression by fetal and maternal cells might be altered in pathological or experimental situations. (C) 2000 Harcourt Publ ishers Ltd.