118. CHARACTERISATION OF HEPARAN SULPHATE PROTEOGLYCANS IN THE MATURING CUMULUS OOCYTE COMPLEX

Abstract

Many growth factors including members of the transforming growth factor beta (TGFβ) superfamily and epidermal growth factor (Egf)-like ligands signal via interactions with heparan sulphate proteoglycans (HSPGs). Cell surface HSPGs can act by sequestering ligands at their site of action, by presenting a ligand to its signalling receptor, or by preventing ligand-receptor interaction. The oocyte secreted factors (OSF) growth differentiation factor 9 and bone morphogenetic protein 15 are members of the TGFβ superfamily that act selectively on cumulus cells. Conversely Egf-like ligands are secreted by mural granulosa cells and transmit LH-induced signals to cumulus cells. We investigated the possibility that HSPGs contribute to the spatially restricted responses these signals exert on cumulus cells. Syndecan-1 and Glypican-1 are cell surface HSPGs that are involved in numerous biological processes, including growth factor regulation, cell proliferation and differentiation. Microarray analysis showed Syndecan-1 and Glypican-1 mRNA expression induced 6-fold (P=10^-9) and 3-fold (P=10^-7) respectively in Egf+FSH stimulated cumulus oocyte complexes (COCs). Furthermore, Syndecan-1 and Glypican-1 mRNA were induced 27- and 16-fold respectively in COCs after hCG treatment of mice. Syndecan-1 and Glypican-1 protein was localised specifically to the COC through immunohistochemical analysis. In Vitro Maturation (IVM) of oocytes is a valuable alternative to gonadotropin mediated superovulation, but IVM COCs are less competent than those matured in vivo. Several components of the COC have been shown to be altered in IVM, including the chondroitin sulphate proteoglycan Versican. COCs from mice that underwent IVM in the presence of Egf+FSH and cilostamide for 16 hours had >16 fold reduced mRNA for Syndecan-1 when compared with In Vivo matured COCs. The lack of Syndecan-1 in IVM COCs could reduce signalling capacity of growth factors including OSFs. This may contribute to the reduced capacity of IVM oocytes to fertilise and produce a healthy embryo, and ultimately, a healthy offspring.