Expression of platelet derived growth factor (PDGF) ligands and receptors in the ovine ovary and effects of PDGFBB on granulosa cell function

Context: While platelet derived growth factors (PDGF) are expressed in the ovary of some species, relatively little is known regarding the potential role that PDGF play in regulating ovarian follicular development.

Aims: To determine the effects of PDGF on granulosa cell function from ovine antral follicles and characterise the expression of PDGF ligands and receptors in developing follicles.

Methods: The effects of the PDGF ligand PDGFBB on thymidine incorporation and progesterone production of granulosa cells were determined with established bioassays. Expression patterns of PDGF ligands, PDGFA, B, C, D, and receptors, PDGFRA and B, were determined using in situ hybridisation. The more sensitive technique of RT-PCR was used to confirm expression of PDGFRA and B in granulosa cells of antral follicles.

Key results: Thymidine incorporation was increased, and progesterone production decreased, from granulosa cells in response to PDGFBB. Oocytes, granulosa cells, thecal layers and corpora lutea expressed at least one PDGF family member. Granulosa cells had faint expression of PDGF receptors, with thecal and luteal tissue also expressing PDGF receptors. Expression of both ligands and receptors was observed in stroma around the follicle.

Conclusions: In sheep, ovarian follicles express both PDGF ligands and receptors, and PDGFBB regulated both thymidine incorporation and progesterone production.

Implications: In sheep, PDGF was identified as an additional locally produced growth factor that regulates follicular function, stimulating granulosa cell proliferation and inhibiting progesterone production. Future work to better understand the role of the different ligands and receptors at different stages of ovarian follicular development seems warranted.