Study On In Vitro Maturation And In Vitro Fertilizition Of Mouse Oocytes

Objective: To determine the effect of FSH and cumulus cells in vitro on mouse oocyte nuclear and cytoplasmic maturation and to examine the capacity of in vitro-matured oocytes undergoing fertilization in vitro.Methods: Immature oocytes were retrieved from murine ovarian stimulated by HMG GV stage oocytes were classified as denuded oocyte (DO) group and cumulus-oocyte complex (COC)group and matured for 36h in HTF supplemented with 0.1 > 0.5 or 1U/mL FSH and HTF without FSH(control group). Germinal vesical breakdown and extrusion of the first polar body were observed with invert microscope during maturation. When the first polar body was found in the perivitelline space, the oocytes were classified as MII (nuclear maturation) . Oocytes extruted the first polar body were stained with fluorescein-Lens culinaris agglutinin to evaluate Cortical granule with laser confocal microscopy for assesscytoplasmic maturation and fertilized in vitro to examine the capacity of undergoing fertilization.Results: DO groups had similar percentage of undergoing GVBD and similar percentage of the first polar body extrusion (P>0.05) ;COC groups treated with FSH had higher percentage of undergoing GVBD and the first polar body extrusion ( P<0.05 ) compared with control group, but percentage of undergoing GVBD and extrusion of the first polar body were similar in groups treated with different FSH concentration ( P>0.05 ) ( P>0.05 ) . Percentage of undergoing GVBD and the first polar body extrusion in COC groups was higher than that in DO groups ( P<0.05, P<0.01) . Cortical granule were distributed in cytoplasm of MII stage DO matured in vitro, and the percentage of formation of a continuous Cortical granule monolayer beneath the oolemma observed with laser confocal microscopy in MII stage oocytes in control COC group was lower than those in COC groups treated with FSH ( P<0.05 ) , but the percentage in every treated-FSH group was similar (P>0.05) . No fertilization was observed in Mil stage denuded oocytes matured in vitro, and the fertilizition rate in 0.1U/mL FSH COC group was higher than that in control COC group (P<0.05) .Conclusion:1, cumulus cell had important role on nuclear and cytoplasmic maturation of oocytes. 2. FSH improved nuclear andcytoplasmic maturation of COC and the effects was Mediated by cumulus cells. 3. Oocytes matured in vitro show lower cytoplasmic maturation, maybe this is main cause of low fertilizition for these oocytes.