Interspecies pregnancy between Ovis canadensis mexicana and Ovis aries with reduced placental P450scc expression and intrauterine growth restriction

The present study aimed to assess the steroidogenic process in the placenta of hybrids Ovis canadensis mexicana x Ovis aries, particularly, to determine the plasma lipid profile and the relative abundance of proteins related to the steroidogenesis, to elucidate in part the mechanism of progesterone deficiency in hybrids. Plasma lipoproteins and placental cholesterol were determined by dry chemical colorimetric assays. Steroidogenic acute regulatory protein (STARD1), StAR-related lipid transfer domain protein 3 (STARD3), cholesterol side-chain cleavage enzyme (P450ssc), and 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) were evaluated by Western blot. In addition, STARD3 was also investigated by immunohistochemical experiments in sheep placenta. Results indicated that cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and very low-density lipoprotein (VLDL) plasma levels were similar between hybrid and control pregnancy groups. Conversely, intracellular cholesterol was increased (P < 0.05) in the placenta tissue of hybrids. No significant differences in the relative abundance of both STARD3, STARD1, and 3 beta-HSD enzyme were observed in the placenta of hybrids compared to control animals, while the relative abundance of cytochrome P450scc was lower in hybrids than in control animals (P = 0.0279). The presence of STARD3 was observed in the cytoplasmic and perinuclear regions of mononucleate and binucleate cells of the trophoblast in the sheep placenta. The significant decrease in the abundance of P450scc in hybrids' placenta may explain the decrease in progesterone biosynthesis, which has been related to intrauterine growth restriction (IUGR) in these animals previously.