Camargo L S A, Paludo F, Pereira M M, Wohlres-Viana S, Gioso M M, Carvalho B C, Quintao C C R, Viana J H M
Brazilian Agricultural Research Corporation - Embrapa, Juiz de Fora, MG, Brazil.
UNIFENAS, Alfenas, MG, Brazil.
Reprod Domest Anim. 2016 Feb;51(1):3-9. doi: 10.1111/rda.12637. Epub 2015 Oct 30.
Oocyte has been considered the major contributor for embryo thermo-tolerance. However, it was shown that sperm factors can be transferred to the oocyte during fertilization, raising the question of whether the absence of such factors could interfere on embryo thermo-tolerance. In this study, we used parthenogenesis to generate bovine embryos without spermatozoa in order to test whether the absence of sperm factors could influence their thermo-sensitiveness at early stages. In vitro fertilized (IVF) and parthenogenetic (PA) embryos at 44 h post-insemination/chemical activation were exposed to 38.5°C (control) or 41°C (heat shock) for 12 h and then developed for 48 h and up to blastocyst stage. Apoptosis index and expression of PRDX1, GLUT1, GLUT5 and IGF1r genes in blastocysts derived from heat-shocked embryos were also evaluated. The heat shock decreased the blastocyst rate at day seven (p < 0.05) for IVF embryos and at day eight (p < 0.01) for both IVF and PA embryos. Total cell number was not affected by heat shock in IVF and PA blastocysts, but there was an increased proportion (p < 0.05) of apoptotic cells in heat-shocked embryos when compared to controls. There was no interaction (p > 0.05) between method of activation (IVF and PA) and temperature (38.5°C or 41.5°C) for all developmental parameters evaluated. Expression of GLUT1 gene was downregulated (p < 0.05) by heat shock in both IVF and PA blastocyst whereas expression of GLUT5 and IGF1r genes was downregulated (p < 0.05) by heat shock in PA blastocysts. Those data show that the heat shock affects negatively the embryo development towards blastocysts stage, increases the apoptotic index and disturbed the expression of some genes in both IVF and PA embryos, indicating that the presence or absence of sperm factors does not influence the sensitivity of the bovine embryo to heat shock.
卵母细胞一直被认为是胚胎耐热性的主要贡献者。然而，有研究表明，精子因子在受精过程中可转移至卵母细胞，这就引发了一个问题，即此类因子的缺失是否会干扰胚胎的耐热性。在本研究中，我们利用孤雌生殖来生成不含精子的牛胚胎，以测试精子因子的缺失是否会影响其早期阶段的热敏性。将授精/化学激活后44小时的体外受精（IVF）胚胎和孤雌生殖（PA）胚胎分别置于38.5°C（对照）或41°C（热休克）环境中12小时，然后继续发育48小时直至囊胚阶段。我们还评估了热休克胚胎来源的囊胚中的凋亡指数以及PRDX1、GLUT1、GLUT5和IGF1r基因的表达。热休克使IVF胚胎在第7天的囊胚率降低（p < 0.05），使IVF和PA胚胎在第8天的囊胚率降低（p < 0.01）。IVF和PA囊胚的总细胞数不受热休克影响，但与对照相比，热休克胚胎中的凋亡细胞比例增加（p < 0.05）。对于所有评估的发育参数，激活方法（IVF和PA）与温度（38.5°C或41.5°C）之间均无相互作用（p > 0.05）。热休克使IVF和PA囊胚中的GLUT1基因表达下调（p < 0.05），而热休克使PA囊胚中的GLUT5和IGF1r基因表达下调（p < 0.05）。这些数据表明，热休克对胚胎向囊胚阶段的发育产生负面影响，增加了凋亡指数，并扰乱了IVF和PA胚胎中某些基因的表达，这表明精子因子的存在与否并不影响牛胚胎对热休克的敏感性。
