Addition of endothelin-1 to culture medium promotes human oocyte maturation

Abstract

To investigate whether the supplementation of culture medium with endothelin-1 may enhance human oocyte maturation and to explore the underlying mechanisms. Experimental study. A total of 140 human germinal vesicle (GV) oocytes obtained in IVF procedure were cultured in medium either with or without supplemented endothlin-1 (100 ng/ml). Changes in transcriptome of cultured cumulus cells treated or untreated by ET-1 were identified by microarray assay. Significantly more oocytes reached metaphase II stage after being cultured in medium supplemented with endothelin-1 (68.2% vs 51.5%, p=0.039). Microarray results revealed 25 significant differentially regulated genes in cumulus treated or untreated with endothelin-1, of which Cx26 gene was the most significantly down-regulated gene. Real-time PCR confirmed microarray analysis results: expression of Cx26 was down-regulated in cumulus cells after endothelin-1 treatment (P=0.032). Immunofluorescence assay showed Cx26 was located in cellular membrane and cytoplasm in both cumulus cells and oocyte. The suppressive effect of endothelin-1 on cumulus Cx26 expression was blocked by cotreament with antagonist for endothelin receptor type B (ETRB), not for type A (ETRA). Supplementation of medium with endothelin-1 promotes human GV stage oocyte maturation via Cx26.