Quantification of P450 aromatase gene expression in cultured and in vivo grown ovarian follicles in sheep

Abstract

A consistent observation during in vitro culture of preantral follicles (PFs) of mammals, was that the rates of in vitro maturation and embryogenesis of the oocytes obtained from the cultured PFs was low relative to the oocytes obtained from antral follicles. It was hypothesized that the suboptimal development potential of the oocytes from cultured PFs may be related to the altered expression patterns of developmentally important genes. Expression of P450 aromatase gene is needed for the synthesis of steroid hormones in the ovarian follicles as they develop from preantral to Graafian follicle stage. The present study was undertaken to compare the quantitative expression of P450 aromatase gene in the sheep oocytes and granulose cells obtained from in vivo grown and cultured ovarian follicles from preantral to Graafian follicle stages.P450 aromatase expression was found in granulose cells obtained from all the stages of in vivo grown follicles. In the in vitro cultured follicles aromatase expression was found in the granulose cells from 2 day cultured follicles only. Similarly the P450 aromatase expression was observed in the oocytes from all the in vivo grown stages of follicles but from none of the in vitro grown stages.It is concluded that the culture system for sheep PFs decreased P450 aromatase expression leading to compromised development potential of the oocytes. Present results provide support to the hypothesis that the compromised development potential of the oocytes from cultured ovarian follicles is related to aberrant expression of developmentally important genes.