CORTICAL GRANULES ANALYSIS IN POSTOVULATORY AGED OOCYTES

WETTEN, PAULA A.; KLINSKY LAHOZ, OMAR G.; MICHAUT, MARCELA A.

Salta

Congreso; Joint LV Annual SAIB Meeting and XIV PABMB Congress; 2019

Once oocytes are ovulated,there is a time window in which they are normally fertilized. After this periodof time, those non fertilized oocytes will decrease their quality leading topostovulatory aging. Postovulatory oocyte aging can occur at any age of a fertilefemale´s life and during oocyte manipulation in assisted fertilizationtreatments. Cortical granule exocytosis (CGE), also referred as corticalreaction, is a secretory process triggered by sperm-oocyte fusion duringfertilization and is involved in blocking polyspermy. Although it is known thataging produces a decrease in fertilization rate and increase the polyspermy,there is no evidence about cortical granule density in postovulatory agedoocytes. Therefore, the aim of this research was to analyse cortical granules densityin postovulatory aged oocytes. Two models of postovulatory aging were tested -in vitro and in vivo aged oocytes- and compared with control condition. Toobtain in vitro aged oocytes, matureoocytes were collected from hormonally stimulated female mice 16 h post hCGinjection (control) and were in vitroincubated for 4 and 8 hs. To obtain invivo aged oocytes, mature oocytes were collected from hormonally stimulatedfemale mice 20 and 24 h post hCG. Results showed that cortical granules densitywas decreased in both postovulatory aged oocytes when compared to controlcells. Secretion of cortical granules was confirmed by staining andquantification of exudate dots. Next, because secretion of cortical granules isa calcium-dependent process, we determined calcium cytoplasmic level usingFura2-AM. We found that in both conditions of aging, the basal calcium level diminishedcompared to the control oocytes. Previous findings have reported that corticalgranules are immersed in an actin network in the cortical region, so weexplored actin localization in aged and control oocytes. Control oocytespresented a cortical actin localization whereas aged oocytes, in bothconditions, showed cortical and cytoplasmic actin localization. Altogether, ourresults suggest that postovulatory aging affects the physiology of corticalgranules in mouse oocytes.