Effects of cysteamine during in vitro maturation on viability and meiotic competence of vitrified buffalo oocytes

The aims of the present study were to assess the effects of cysteamine as an anti-oxidant on the rate of in vitro maturation (IVM) of buffalo oocytes (experiment 1), and their viability and nuclear status following vitrification (experiment 2). Immature oocytes with compact cumulus cells obtained from the ovaries of slaughtered animals were harvested and then cultured in the maturation medium with no cysteamine (control) or 50 μM cysteamine (treated). Oocytes were vitrified in vitrification solution 1 (VS1): 1.5 M ethylene glycol (EG) + 1.5 M dimethyl sulfoxide (DMSO) for 45 s (step one). After this initial exposure, oocytes were transferred to VS2: 3 M EG + 3 M DMSO in a holding medium for 25 s (step two). After warming, oocytes were evaluated morphologically and then cultured for a further 2 h in the cysteamine-supplemented or control maturation media. The oocytes were evaluated morphologically, stained with trypan blue for viability evaluation. The maturation rate of oocytes was higher (P<0.05) for IVM media with cysteamine compared with controls. There was no significant difference in morphology, survivability and maturation rate between the two vitrification groups (cysteamine-treated and untreated groups) but the morphology, survivability and percentages of metaphase-II oocytes in both groups of vitrified oocytes were lower compared with their respective controls. In conclusion, the addition of cysteamine to the maturation medium improved nuclear maturation of buffalo oocytes but had no positive effect on their cryoresistance during vitrification.