Hypoxia-inducible factor (HIF1alpha) inhibition modulates cumulus cell function and affects bovine oocyte maturation in vitro†.

Various metabolic and hormonal factors expressed in cumulus cells are positively correlated with the in vitro maturation (IVM) of oocytes. However, the role of hypoxia sensing both during maturation of cumulus-oocyte complexes (COCs) as well as during the resumption of meiosis remains uncertain. HIF1alpha plays major roles in cellular responses to hypoxia, and here we investigated its role during bovine COC maturation by assessing the expression of related genes in cumulus cells. COCs were divided into the following groups: immature (control), in vitro matured (IVM/control), or matured in the presence of a blocker of HIF1alpha activity (echinomycin, IVM/E). We found an inhibition of cumulus cell expansion in IVM/E, compared with the IVM/control. Transcript levels of several factors (n = 13) were assessed in cumulus cells. Decreased expression of HAS2, TNFAIP6, TMSB4, TMSB10, GATM, GLUT1, CX43, COX2, PTGES, and STAR was found in IVM/E (P < 0.05). Additionally, decreased protein levels were detected for STAR, HAS2, and PCNA (P < 0.05), while activated-Caspase 3 remained unaffected in IVM/E. Progesterone output decreased in IVM/E. The application of PX-478, another blocker of HIF1alpha expression, yielded identical results. Negative effects of HIF1alpha suppression were further observed in the significantly decreased oocyte maturation and blastocyst rates from COCs matured with echinomycin (P < 0.05) or PX-478 (P < 0.05). These results support the importance of HIF1alpha for COC maturation and subsequent embryo development. HIF1alpha is a multidirectional factor controlling intercellular communication within COCs, steroidogenic activity, and oocyte development rates, and exerting effects on blastocyst rates.

Progesterone receptor blockers: historical perspective, mode of function and insights into clinical and scientific applications.

Antigestagens (antiprogestins) are functional competitors of progesterone (P4) that prevent P4 from mediating its biological functions either by suppressing its production or blocking its function. Among the latter are progesterone antagonists, competitors of P4 binding to its nuclear receptor PGR, which have found application in both human and veterinary medicine, in particular in small animal practice for the prevention of nidation and the interruption of pregnancy. Depending on their mode of action, progesterone receptor antagonists can be divided into 2 classes. Class I antagonists bind to the PGR but fail to induce its binding to promoters of target genes (competitive inhibitors). Class II antigestagens, including aglepristone used in veterinary medicine, bind to the PGR, activate its association with a promoter, but interfere with the downstream signalling cascades, e. g., by recruiting transcriptional repressors. They act thereby as transdominant repressors exerting negative effects on target gene expression. Importantly for experimental sciences, as active antagonists, class II antagonists do not require the presence of the natural ligand for their action. Besides their clinical application, antigestagens are used in research for investigating P4-dependent physiological and pathological processes. Here an overview of the history and the current usage of progesterone receptor antagonists in veterinary medicine and research is presented.