Low oxygen concentration improves yak oocyte maturation and inhibits apoptosis through HIF‐1 and VEGF

Abstract

The gas-phase environment of in vitro culture system plays an important role in the development of oocytes, and oxygen concentration is one of the important factors. In the present study, we aimed to explore the effect of different oxygen concentrations (20%, 10%, 5% or 1% O 2 ) in yak oocyte maturation and to detect the expression of hypoxia-inducible factor 1α (HIF-1α), vascular endothelial growth factor (VEGF) and cell apoptosis in yak COCs. First, the maturation rate of oocytes, cleavage rate and blastocysts rate following parthenogenetic activation in the group with 5% oxygen concentration were significantly higher (p < .05) than the other groups. Then, TUNEL analysis showed that the 5% oxygen concentration group significantly inhibited apoptosis of cumulus-oocyte complexes (COCs) compared to the other group, and the transcription and protein levels of pro-apoptotic factor Bax, HIF-1α and VEGF in yak COCs significantly reduced, while anti-apoptotic factor Bcl-2 significantly increased.Furthermore, immunohistochemical staining results indicated that HIF-1α protein was mainly located in theca follicle interna, mural follicular stratum granulosum, corona radiata and ovarian stroma in the follicular ovarian tissue, while VEGF protein was mainly located in the granulosa and theca cell layers. In summary, our findings demonstrate that 5% oxygen concentration may promote maturation and inhibit apoptosis of oocytes through HIF-1α-mediated VEGF expression.

"Vascular Endothelial Growth Factor A Improves Quality of Matured Porcine Oocytes and their Subsequent Embryos Development"

“…The GSH content of oocytes is associated with the male pronuclear formation and blastocyst development, as well as the total cell number of each blastocyst [27,34,35]. An increase in GSH storage is observed when antioxidants, such as ascorbic acid [27,34,36] and cysteamine [36], are supplemented in the oocyte maturation medium.…”

Factors Influencing the Maturation and Developmental Competence of Yak (Bos grunniens) Oocytes In Vitro

“…The proper mechanism might be that 5% oxygen up-regulated HIF-1α expression. HIF-1α subsequently increased the BCL-2 mRNA expression and decreased the BAX mRNA expression in yak COCs and blastocysts, whereas CDX2, POU5F1, SOX2, and NANOG mRNA expressions in blastocysts were significantly increased [158][159][160].…”

Expression and correlation of the Pi3k/Akt pathway and VEGF in oral submucous fibrosis

“…VEGF regulates the function of the extracellular matrix through endothelial cell proliferation and migration blood vessel formation, and matrix metalloproteinase expression 4,5 . In addition, the expression of VEGF could be significantly increased through the up‐regulation of Pi3k/AKT signalling, a significant pathway in numerous cellular functions, like cell proliferation, survival and apoptosis 6,7 . According to previous researches, Pi3k/AKT pathway can promote VEGF expression and secretion, and play a role in angiogenesis 8 .…”

“…4,5 In addition, the expression of VEGF could be significantly increased through the upregulation of Pi3k/AKT signalling, a significant pathway in numerous cellular functions, like cell proliferation, survival and apoptosis. 6,7 According to previous researches, Pi3k/AKT pathway can promote VEGF expression and secretion, and play a role in angiogenesis. 8 It effects the expression level of angiogenic factors including nitric oxide and angiopoietins.…”