The Expression Of VEGF Family And Its Receptors In Parthenogenetic Porcine Embryos

Recently, the pigs have been applied as a extensive model by scientists forhuman disease treatments and stem cell therapy. And the parthenogenetic (PA)porcine embryos, since its advantages of unfertilized process and not violating theethics, have gainedextensive attention. However, many studies demonstrated thattheporcine embryo cannot develop to term according to the defects of the placenta.Presently, the abnormal development of porcine PA fetus was considered to becaused by the lacking of maternal imprinting genes which was suggested to berelated with the methylation level of its promoter. Furthermore, the PA placenta wasreported to have defects on vascular development. According to this, we speculatedthat the decreasing angiogenesis of porcine PA placenta was also one of theimportant influencing factors which led to the failure of porcine PA fetaldevelopment.In this study, three groups of PA embryos(the number of embryos is217,238and190separately) was produced by the PA activation technique, then by theembryo transfer method, they were implanted to three10month old sows (P-1, P-2and P-3)which were at the estrous stage; meanwhile, another three estrous sows (N-1,N-2and N-3) were fertilized by artificial insemination. The sows were identified tobe pregnant by the ultrasound detecting devices on D28. Then the sows wereanaesthetized on the same day, and the uteruses were derived. At last, the fetuses andplacentas inside the uteruses were separated successfully. The litter size of sows P-1,P-2and P-3were6,8and11separately; and the fetal number of N-1, N-2and N-3were15,13and16separately. By comparison of the data, the number of PA fetuseswas smaller than the control fetuses, which was suggested that the PA fetus mighthave a lower birth rate. Furthermore, the morphologies of fetus and placenta were compared, and the size of PA embryo was smaller than that of control. Interestingly,the color PA placenta was found to be more slight, this result confirmed the previousstudy regarding to the defective development of PA angiogenesis.Due to the lacking angiogenesis, the angiogenic-related factors in vascularendothelial growth factor (VEGF) family were assumed to be related with thedefects of porcine PA placenta. Q-PCR was used for analyzing the expressing patternof four VEGF family and its receptors (VEGFA, KDR, FLT-1and PLGF) inparthenogenetic porcine fetuses and placentas. The result showed that the expressionof this four factors had no significant differences (p>0.05) in PA fetuses; however,the expression of KDR, FLT-1and PLGF showed significant decreased expression(p<0.05) in PA placenta except for the unapparent expressing changes of VEGFA(p>0.05). This result demonstrated that the VEGF family might play an importantrole in the development of PA placentas to impact the later growth of PA fetuses.According to the previous study, VEGF isoforms could activate the VEGFsignaling pathway by the combination with the receptors, then complete the functionof angiogenesis. On the basis of this background, we designed the primer of threeVEGF isoforms. First, the expression of VEGF isoforms in PA fetuses and placentaswere detected by Q-PCR, the result showed that the expression of the isoforms hadno significant changes in PA fetuses (p>0.05); however, the VEGF164andVEGF188were showed to have decreased expressions, and the expression ofVEGF120went up dramatically (p<0.05). At last, RT-PCR was used to identify theexpressing pattern of VEGF isoforms in PA fetuses and placentas, which matchedwith the data of Q-PCR completely.Thus, we suggested that the lower expression of VEGF family, especially thedisordered expression of VEGF isoforms, which could play a critical role in theangiogenetic process of porcine PA placentas, might result in the defects of PAplacentas, and then led to the miscarry of PA embryos.