Disorders of follicle development and steroidogenesis in ovaries of androgenised foetal sheep

The prenatally androgenised (PA) sheep is a well-recognised model for the study of developmental programming of adult polycystic ovary syndrome (PCOS). Most of the studies to date have involved examination of the reproductive and metabolic effects in the offspring after puberty, but more recently, it has been reported that there is disruption of follicle formation and steroid gene expression in ovaries of foetal sheep after exposure of the mother to excess androgen. Our study examines evidence for precocious primordial follicle formation at day 90 of gestation in ovaries of foetal Poll Dorset sheep. Using a specific marker of germ cells (VASA homologue protein) in ovarian sections, we found that androgenised sheep had nearly double the proportion of germ cells enclosed in follicles compared with control animals. When analysed by follicle stage, there was no significant difference between groups in the proportion of primordial follicles and growing (transitional and primary) follicles. Differences between PA and control foetal sheep were found in both mRNA and in protein expression of steroidogenic enzymes and androgen receptor. Our results in Dorset ewes are complementary to previous reports, but suggest that the timing of follicle formation and steroidogenic activity may vary between different breeds as well as in response to androgen. These data show that granulosa cells constitute a specific target for programming by androgen in utero and raise key questions about the role of exposure to androgen in utero in developmental origins of PCOS.