Effect of vitrification on the chromatin status in <i>Sus Scrofa Domesticus</i> cumulus - oocyte complexes
Successful solution of the problem of preserving the viability of devitrified donor porcine oocytes will significantly intensify innovative cellular reproductive and DNA technologies by creating cryobanks of female gametes with positive qualitative characteristics. Creation an effective model of vitrification and media for the cultivation of frozen-thawed oocyte-cumulus complexes is an important task of cryo-and embryo-technologists. Highly dispersed silica nanoparticles (nHDS) possess, due to their structural features, a number of important properties (high sorption capacity of proteins, absence of allergenic and toxic effects on cells, activation of reparative processes, antioxidant effects), can be proposed as potential components of cryoprotectants and media for culturing devitrified cells. The effects of 0.001% nHDS on the chromatin status of native and devitrified Sus Scrofa Domesticus cumulus -oocyte complexes during in vitro culture have identified. 0.001% nHDS had not cyto- and genotoxic effects on both native and devitrified oocyte-cumulus complexes during cultivation, moreover, they reduced the level of destructive processes (apoptosis, pycnosis) provoked by ultralow temperatures (vitrification). A cryoprotective effect of 0.001% nHDS on devitrified somatic (cumulus) cells and gametes of Sus Scrofa Domesticus ovarian follicles after the freezing / thawing and cultivation during 44 hours was detected.The addition of 0.001% nHDS into cryoprotective and culture media had a positive effect on the morphofunctional state of cumulus cells after the vitrification and cultivation procedure. The proportion of cells with compact cumulus treated with 0.001% nHDS after devitrification increases from 33 % to 48 %, P<0,01. The level of oocytes with cumulus in a high degree of expansion after 44 hours of cultivation with 0.001% nHDS was 61 % vs 39 %, P<0,05, in control. The use of nHDS in the steps of the cumulus- oocyte- complexes vitrification procedure caused a decrease in the proportion of apoptotic cells (TUNEL-test) in the cumulus from 54 % to 35 %, P<0,05. The level of matured devitrified oocytes treated with 0.001% nHDS before culture increased from 33 % control to 59 %, P<0,001. The obtained results allow us to recommend the use of 0.001% nHDS in the steps of porcine oocytes vitrification technology.