Ranking and selection of MII oocytes in human ICSI cycles using gene expression levels from associated cumulus cells

Abstract

Can the ranked expression levels of a cohort of cumulus cell (CC) genes be used to select MII oocytes with a potential for blastocyst development and live birth? A ranking method containing four (HAS2, FSHR, VCAN, PR) of the eight genes evaluated in this study for identifying good quality MII oocytes provides a significantly better outcome compared with random selection and is equally as good as using all oocytes for ICSI. Recent evidence has identified a number of candidate genes in CC that have the potential to serve as markers of oocyte quality; however, a reliable method for selecting MII oocytes with blastocyst and live birth potential remains a challenge. A group of 25 patients (<38 years old) underwent rFSH-stimulated ICSI treatment with single embryo replacement (SET). A total of 270 cumulus cell-oocyte complexes (COCs) were recovered and assessed. Expression levels of eight candidate genes (HAS2, FSHR, SLC2A4, ALCAM, SFRP2, VCAN, NRP1 and PR), corrected for RPL19, were measured in individual CC masses using multiplex QPCR. Expression levels of individual CC masses were assessed and ranked in relation to oocyte developmental indicators (blastocyst formation and live birth). From the 25 women, 19 (76%) had achieved a successful live birth delivery following SET. In this population, the selection of MII oocytes according to relative ranking levels of a subset of CC-expressed genes provided a significantly higher chance of identifying a good quality oocyte compared with selecting MII oocytes randomly (blastocyst: 1× MII oocyte: 52 versus 23%, P = 0.008; 3× MII oocytes: 80 versus 52%, P = 0.002; live birth: 1× MII oocyte: 31 versus 15%, P<0.05, 3× MII oocytes: 60 versus 38%, P < 0.05) and a similar chance to that of using all oocytes available after recovery (blastocyst: 80% versus 96%, P = 0.085, live birth: 60% versus 76%, P = 0.206). The present method was validated only for young (<38 years) women, with male infertility, who had no signs of androgenicity, PCOS or endometriosis and were free of any chronic disease. This is a retrospective study that requires further validation in an unselected population. Results presented in this study could be used to assist the selection of oocytes with high blastocyst developmental potential in frozen oocyte cycles and for the selection of embryos with high developmental potential as early as 18 h after ICSI (2PN stage) in fresh human IVF cycles. Funding was provided by Fertility Associates Ltd and the New Zealand Government. The authors declare there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.