Expression Of VEGF And FLT-1 In Bovine Preimplantation Embryos And Effects Of Vegf On Early Development Of Bovine Embryos Derived From In Vitro Fertilization

VEGF ( vascular epidermal growth factor) is an important growth factor on the development of preimplantation embryos. Maturation of oocytes and development of preimplantion embryos are regulated by VEGF in direct or indirect manner. The aim of this study was to illuminate the expression of proteins and mRNAs of VEGF and Flt-1 in bovine preimplantation embryos derived from IVF by using indirect immunofluorescence, laser scanning confocal microscopy and RT-PCR. Furthermore, bovine IVF embryos were cultured in vitro in development media without or with VEGF (1,5,10 ng/ml), and the effects of VEGF on early development of bovine IVF embryos were observed. The results from this research are as follows.1. Expression of proteins and mRNAs of Flt-1 were detected in COC, immature oocytes, embryos in 2-cell, 8-cell, blastocyst, and hatched blastocyst stage. Immunofluorescence results demonstrated that Flt-1 could be detected in cell membrance and the regions under it. In oocytes, Flt-1 could be observed in cell plasma. It is suggested that expression of Flt-1 was in persisting consistency.2. Expression of VEGF proteins and mRNAs in COC, immature oocytes and blastocysts were detected. But they were not observed in embryos from 2-cell tomorula stage. Immunofluorescence results demonstrated VEGF was concentratedly located in cell membrance and the regions under it. It is suggested that expression of VEGF is differential in space-time.3. VEGF concentrated in lng/ml, 5ng/ml, 10ng/ml were supplemented in development media of IVF embryos. Then in all groups with or without VEGF, the rates of cleavage were 61.99%, 75.69%, 76. 81%, 68.92%, the development rates of 8-cell were 51.82%, 61.21%, 65.41%, 63.40%, the development rates of blastocysts were 27.74%, 24.85%, 23.90%, 22.88% and the development rates to hatched blastocysts were 5.11%, 4.85%, 5.66%, 3.27%, respectively. Though there were no significant difference among the rates of cleavage, 8-cell, blastocysts and hatched blastocysts in all groups with or without VEGF, the rates of cleavage and the development rates to 8-cell supplemented with VEGF were all higher than the rates of contrast, and the development rates to blastocysts and hatched blastocysts were lower, compared with that of constrast. These results indicated that VEGF has initial beneficial effects for IVF embryos on the cleavage and development to 8-cell stage. It need be further studied whether VEGF added to development media brought on the decrease of development rates to hatched blastocysts.