200 Effect of Exogenous Progesterone During in Vitro Culture on Early Embryo Development in Cattle

Abstract

Preimplatation embryos grown in vitro are sensitive to their environment, and the conditions of culture can affect developmental potential. Progesterone (P4) is the key hormone responsible for maintenance of pregnancy in mammals, and circulating levels in the early postconception period have been associated with pregnancy success. It is not clear whether P4 acts directly or indirectly on the embryo to alter gene expression and development. The aim of this study was to assess the effect of varying levels of exogenous P4 on the development of bovine zygotes to the blastocyst stage in vitro. A preliminary study was conducted to analyze the media used for culture (stock of P4, SOF, SOF + 1 × 10–7 M P4) on Days 1 (day of culture), 4, and 7 for P4 concentration in 25-μL droplets overlain with mineral oil or 500 μL in wells with or without mineral oil. P4 was measured using an ELISA kit, prepared for human serum or plasma (DE1561 Dimeditec Diagnostics GmbH, Kiel, Germany). Inter- and intra-assay coefficients of variation were 6.63 and 6.42%, respectively, and recovery was 95%. P4 concentration on Day 1 in all media was the expected (40 ng mL–1). However, on Days 4 and 7 in media under mineral oil, the level of P4 was nearly zero (0.1 to 1.6 ng mL–1) compared with the media without mineral oil, which remained unchanged (39 to 40 ng mL–1) through the 7 days of culture. Zygotes (n = 1467) were produced in 8 replicates by in vitro oocyte maturation and fertilization, and were cultured in groups of 40 to 50 in wells of 500 μL without mineral oil in (1) SOF supplemented with 5% fetal calf serum (control–), (2) SOF with ethanol (control+), (3) SOF with P4 0.1 × 10–7 M, (4) SOF with P4 1 × 10–7 M, and (5) SOF with P4 10 × 10–7 M at 39°C, 5% CO2 and 5% O2, with maximum humidity. No significant difference was found between groups in cleavage rate or blastocyst yield on Days 6, 7, and 8 (Table 1). These results indicate that the addition of P4 to the in vitro culture medium (SOF) did not enhance the development of bovine embryos to the blastocyst stage. However, further studies on the quality of these embryos in terms of gene expression are in preparation. Table 1. Effect of P4 on bovine in vitro early embryo development

Effect of increasing progesterone concentration from Day 3 of pregnancy on subsequent embryo survival and development in beef heifers

“…In an attempt to answer this question, some authors have added progesterone to embryo culture medium in vitro and examined development to the blastocyst stage. Results have been varied and contradictory with some authors reporting positive effects of progesterone (Ferguson et al 2005;Merlo et al 2007), while others have reported no effect (Reggio et al 1997;Goff and Smith 1998;Clemente et al 2008). Consistent with the majority of these studies, Rings et al (2008) reported no difference in blastocyst development on Day 7 following transfer of in vitroproduced bovine zygotes to the oviducts of heifers with normal or artificially-elevated progesterone (using the same protocol as in the present study).…”