Evidence of endometrial binucleate cells in cattle: A product of mono-culture or a new endometrial epithelial phenotype?

Katheryn D. Peterson¹, Jaydeep Kolape², and Daniel J. Mathew¹

¹University of Tennessee Institute of Agriculture, Department of Animal Science, University of Tennessee, Knoxville, TN, USA

²Advanced Microscopy and Imaging Center, University of Tennessee, Knoxville, TN, USA


Abstract Text:

Trophoblast binucleate cells (BNC) are integral to establishing the distinctive synepitheliochorial placenta observed in cattle. Comprising roughly 15-20% of the trophoblast, BNC fuse with and in some areas of the endometrial caruncle, replace endometrial epithelial cells forming a hybrid feto-maternal syncytium. The BNC also migrate through epithelial tight junctions to release secretory granules containing pregnancy associated glyco-proteins, placental lactogen and other fetal-derived molecules into the maternal vasculature. While fetal derived BNC are well characterized, the presence of BNC in other reproductive tissues of cattle has not been reported. During a recent study, binucleated cells were observed in mono-cultures of primary bovine endometrial epithelial cells collected from intercaruncular endometrial tissue of heifers, raising the possibility of maternal derived BNC within the endometrium. To confirm their presence and monitor cell division, the endometrial epithelial cells were isolated and cultured (mono-culture) in the Incucyte time lapse imaging system. Time lapse imaging revealed that the cells were highly migratory but remained binucleated for more than 24 h. A recent study reported BNC within the rodent mammary gland, raising the possibility that the endometrial epithelial BNCs may reside within bovine endometrial glands localized within intercaruncular endometrium. Endometrial glands are essential for histotroph production and support embryonic development in cattle. For these reasons, primary bovine endometrial epithelial cells and intact endometrial glands were isolated from heifer intercaruncular endometrium and evaluated for BNC using 4’, 6-diamidino-2-phenylindole (DAPI) and immunofluorescence for alpha-tubulin. Using a Leica SP8 confocal microscope, images were captured of several mono-cultured cells and a small number of cells within the intact endometrial glandular epithelium that appeared to be binucleated. Follow up studies involving transmission electron microcopy and flow cytometry are underway to confirm the presence of endometrial BNC in cattle, a novel finding. A greater understanding of bovine endometrial cell physiology, particularly related to the endometrial epithelium and BNC formation, will increase our understanding of early pregnancy in cattle, an important agricultural species.