Vitrification of equine oocytes with a polyvinyl alcohol after in vitro maturation with equine growth hormone and insulin-like growth factor-i

BACKGROUND: In vitro fertilization (IVF) procedures are limited by the inability to mature equine oocytes on in vitro methods. OBJECTIVE: The aim of this study was to evaluate structural integrity of equine oocytes subjected to vitrification with a synthetic polymer (PVA). METHODS: The effect of eGH and its relationship with IGF-I on in vitro maturation (IVM) were evaluated. Compact cumulus oocytes complexes (n=122) were cultured in TCM-199 with eGH, IGF-I or eGH+IGF-I for 30h at 38.5C in air with 5% CO2. Oocytes were fixed after IVM or subjected to the vitrification protocol. Cryopreserved oocytes were exposed to 1.4M DMSO+1.8M EG+1% PVA for 3min, and then transfer to 2.8M DMSO+3.6M EG+0,6M sucrose+1% PVA for 1min. After rewarming, oocytes were evaluated by confocal microscopy. RESULTS: Maturation rates of oocytes were not significant different among groups (P>0.05), however eGH+IGF-I group can develop the assessment of resumption of meiosis (MI+MII = 86.7%). CONCLUSION: The oocyte did not show morphological alterations. The use of PVA-copolymer may represent a potential alternative for vitrification of equine oocytes after IVM.