[Synopsis] Fibroblast growth factor 9 (FGF9) plays a key role in the regulation of cell differentiation, cell proliferation and embryonic development. It is also a survival factor for various cell types and interacts with two FGF receptors, FGFR2 and FGFR3. Furthermore, the absence of specific thecal-and oocyte-derived products during in vitro maturation (IVM) is suggested to be one reason for the reductions in the competency of oocytes used in assisted reproductive techniques. FGF9, as with some FGFs shown to promote oocyte competence and embryo development in several species is localize largely in theca cells, somewhat in the oocyte and its receptors in oocytes and cumulus cells. Therefore, to investigate the possible reproductiverelated implications of FGF9 supplementation, its effects on IVM oocytes after parthenogenetic activation (PA) using the pig model were examined. Five approaches were taken to explore the function of FGF9 during in vitro embryo production (IVP). First, the maturation medium was supplemented with exogenous FGF9 to investigate its effects on maturation of GV oocytes measured by the extrusion of the first polar body hence MII oocytes. The results showed that FGF9 significantly accelerated MII rates in 50 ng/ml treated group (p<0.05) but had no visible change on embryo development after PA. However, the addition of FGF9 in both maturation and embryo culture media improved MII rates at 50 ng/ml (p<0.05), cleavage at 100 ng/ml (p<0.05) and blastocysts rate significantly (p<0.05) across treated groups after PA. Third, the addition of FGF9 in embryo culture alone revealed no visible effect. Fourth, RNA sequence analysis showed that FGF9 significantly up-regulated Thyroid hormone (TRH) providing insight into its possible mechanisms of action during IVM. With regards to oocyte quality, mitochondria membrane potential, mitochondria number and ROS levels were significantly increased at 100 ng/ml (p<0.05), reduced at 50 ng/ml (p<0.05) and increased across all FGF9-treated groups (p<0.01 and <0.05) respectively. Taken together, the present study determined that at least another thecal- and oocyte-derived product, FGF9, improves oocyte maturation and subsequent embryo development when provided during IVM and IVC. These findings, therefore, may be useful for porcine IVP system.

Departmental Bulletin Paper

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