Using culture models of ovine and bovine ovarian cells (granulosa, theca and endothelial), we are investigating the role of FGFs in follicle development. Our research has shown that one particular FGF (FGF18) is secreted from capillary endothelial cells in response to TGFB and BMP4, and increases the rate of granulosa cell death. Further, high fecundity Booroola sheep have lower levels of FGF18, showing a unique regulation of fertility by the vasculature.
Mycotoxins are prevalent in animal feed worldwide and impact livestock growth and fertility, particularly pigs. We have demonstrated that a common mycotoxin, DON, negatively affects granulosa cell function in cattle. In cattle, DON is converted to a metabolite (called DOM-1) that is generally considered to be non-toxic, however, our research has shown that DOM-1 seriously reduces theca cell growth and function, and causes follicle regression in vivo. These results show that mycotoxin metabolites may not be as inert as previously believed.
Dairy cattle undergo a period of infertility post-partum owing to the energy drain of lactation, and they mobilize significant stores of fat from adipose tissue. We are looking at the role of hormones secreted by adipose tissue (adipokines) and muscle (myokines) in ovarian function. Irisin is a recently discovered ‘exercise hormone’ secreted by muscle in humans and rodents, and we have found significant mRNA and protein abundance in subcutaneous adipose tissue in cattle. Plasma concentrations of irisin are elevated in cattle post-partum, and irisin increases granulosa cell metabolism but decreases function (estradiol secretion). Theca cells respond differently, as irisin decreases cell metabolism and has no effect on function (androgen secretion). These data suggest that post-partum anestrus in cattle may be exacerbated by irisin secreted from adipose tissue.