Expression of DNA methyltransferase genes in four-cell bovine embryos cultured in the presence of oviductal fluid.

The possible epigenomic effect of oviductal fluid on expression of DNA methyltransferase (DNMT) genes was examined in early bovine embryos (4-cell stage). Real-time quantitative PCR was performed to determine the relative expression of DNMT1, DNMT3a and DNMT3b transcripts in embryos cultured in vitro in the presence or absence of oviductal fluid. Expression of DNMT1 significantly increased when cultured with oviductal fluid, whereas DNMT3a and DNMT3b transcripts were unaffected by the addition of oviductal fluid. These results may help reveal the role of oviductal factors in the regulation of DNMT expression.

In vivo and in vitro sperm interaction with oviductal epithelial cells of llama.

Sperm reservoirs in South American Camelids would be crucial for successful fertilization. Since ovulation occurs approximately 36 h after mating, the maintenance of the sperm viability in the oviduct waiting for the ovum is a critical reproductive event. Our study aimed at determining whether the isthmus or the utero tubal junction (UTJ) could function as a sperm reservoir in llama by means of in vivo and in vitro experiments. For the in vivo experiments, the oviducts of adult females with a dominant follicle bigger than 7 mm were examined for the presence of sperm at 6, 18, 24, 28 and 35 h after mating. The results using scanning and transmission electron microscopy showed ultrastructural differences between isthmus and UTJ with respect to (1) predominance of secretory cells in the UTJ and ciliated cells in the isthmus epithelium and (2) cytoplasmic bulbous projection of the secretory cells in the UTJ. Sperm adhered by a mucus-like substance were seen only in the UTJ at 6, 18, 24 and 28 h postmating. Lack of sperm adhered to oviductal mucosa was observed around ovulation (35 h). In vitro experiments demonstrated higher ability of UTJ epithelial cell explants with respect to isthmus explants to bind sperm in a co-cultured system. The anatomical features and the presence of a sperm bonding agent in the UTJ together with the in vitro differential binding of sperm to UTJ explants strongly suggest that both may be feasible mechanisms that facilitate sperm storage in this oviductal region in llama.