Altered gene expression in embryos and endometrium collected on day 8 of induced aluteal cycles in mares

Aluteal cycles were induced in the mare to evaluate the effects of progesterone deprivation on the gene expression of embryos and endometrium collected eight days after ovulation. We hypothesized that the transcript expression would be altered during induced aluteal (AL) cycles (low progesterone 4 ng/mL) for 1) the embryonic expression of progesterone-mediated transcripts and those related to normal embryo growth and development and 2) the endometrial expression of progesterone-mediated transcripts and those related to prostaglandin synthesis and normal pregnancy establishment. Seven cyclic mares with a median age of 6.5 years (range 3–16) were utilized in a crossover design. Mares in estrus were artificially inseminated to a fertile stallion and randomly assigned to control or AL groups. Mares received either saline solution (control mares) or PGF2α (AL mares), twice daily on days 0, 1, and 2 and once daily on days 3 and 4. Serial blood samples were collected daily from day 0 (ovulation) until the day of embryo collection and endometrial biopsy on day 8. Mares were monitored until they returned to estrus, and artificially inseminated. Mares were switched to the opposite treatment group only after a successful embryo collection occurred during the previous cycle and only cycles that produced embryos were used for analyses. The study design resulted in paired samples from each mare for analyses. No significant rise in progesterone was observed in the AL group with mean concentrations of plasma progesterone remaining