Effect of different cryo-devices on in vitro maturation and development of vitrified-warmed immature buffalo oocytes.

The aim of the study was to identify a cryo-device that would be best suited for the vitrification of buffalo immature cumulus-oocyte complexes (COCs) as judged by viability and meiotic competence of the vitrified-warmed oocytes and their development ability following in vitro fertilization (IVF). The expression of oocyte secreting factors and their receptors (GDF9, BMP15, BMPR2, TGFBR1) and apoptosis related genes (BCL2, BAX, P53, C-MYC) were compared in vitrified-warmed oocytes after in vitro maturation. COCs from the ovaries of slaughtered buffaloes were vitrified in a combination of dimethyl sulfoxide, ethylene glycol, and sucrose using either a conventional straw (CS), open pulled straw (OPS), cryoloop (CL), hemistraw (HS) or cryotop (CT). The fresh COCs were exposed to vitrification and warming solutions as in other vitrification methods without plunging in to liquid nitrogen (EC). The viability of vitrified-warmed COCs, 2 h post warming in HS and CT was similar to fresh and EC groups but significantly higher than CS and OPS methods. The proportions of oocytes with first polar body after 24 h in vitro maturation were significantly higher in HS and CT methods than in CS, OPS and CL methods. The development ability of these vitrified-warmed oocytes to blastocyst stage following IVF in all vitrified groups was significantly lower than control and EC groups. Among the vitrified groups, the blastocyst rate in HS, CT and CL groups was significantly higher than in OPS and CS groups. It was also observed that the expression levels of GDF9, BMP15, BMPR2, TGFBR1, BCL2, BAX, P53 and C-MYC genes in vitrified-warmed COCs in CT, HS and CL groups were similar to control. The results indicated that HS, CT and CL are more suitable cryo-devices for vitrification of buffalo immature oocytes.

Meiotic maturation of vitrified immature chousingha (Tetracerus quadricornis) oocytes recovered postmortem.

The ability to recover and cryopreserve oocytes from postmortem ovaries of endangered or wildlife species holds tremendous potential for conservation using assisted reproductive technologies. The objective of this study was to assess the in vitro meiotic maturation of chousingha (four-horned antelope) oocytes following vitrification using open pulled straw (OPS) method. The average number of oocytes recovered per ovary was 65.6. The proportion of oocytes that matured was significantly lower in vitrified oocytes (29.4%) when compared with fresh oocytes (69.3%). The study provides evidence that it is possible to cryopreserve immature oocytes by vitrification collected from the ovaries of chousingha at postmortem and also demonstrates that these cryopreserved oocytes retain their potential to undergo in vitro meiotic maturation.