RESUMO
The goal of this study was to examine the effect of insulin-like growth factor I (IGF-I; added during post-thaw culture (48 h)) on the preimplantation viability and quality of cryopreserved bovine in vivo recovered embryos. The morula stage embryos, non-surgically recovered from superovulated dairy cows of Czech Fleckvieh cattle breed, had previously been cryopreserved by a slow freezing technique and stored in liquid nitrogen since 1989-1990. Following thawing, the embryos were cultured for 48 h either alone (no IGF-I) or in the presence of IGF-I (10 or 100 ng/ml); non-cultured embryos served as a control. Thereafter, the embryos were analyzed for cleavage to the blastocyst stage, apoptosis (TUNEL), embryo cell number and quality of actin cytoskeleton. Following post-thaw culture 41% of embryos developed to advanced blastocysts. IGF-I increased this per cent and, at a higher dose, essentially reduced the per cent of degenerated embryos. In cultured embryos, IGF-I at both doses elevated the cell number compared with non-cultured embryos. However, in comparison with embryos cultured without IGF-I, only the higher IGF-I dose resulted in elevating the embryo cell number. The TUNEL index was significantly lowered by IGF-I treatment. Thawed embryos were mostly of the grade III actin type and fewer (12%) had grade II actin, whilst no grade I actin embryos were noted. The addition of IGF-I resulted in the appearance of grade I actin embryos (8.33 and 6.9% for 10 and 100 ng/ml, respectively). These observations indicate that the addition of IGF-I during post-thaw culture can improve the quality of bovine cryopreserved embryos.