131. INDUCED OOCYTE IN VITRO MATURATION (IVM) SUBSTANTIALLY IMPROVES EMBRYO YIELD AND PREGNANCY OUTCOMES
F. K. Albuz A , M. Sasseville A , D. T. Armstrong A , M. Lane A , J. G. Thompson A and R. B. Gilchrist AThe Robinson Institute, Research Center for Reproductive Health, Discipline of O, The University of Adelaide, Adelaide, SA, Australia
Reproduction, Fertility and Development 21(9) 50-50 https://doi.org/10.1071/SRB09Abs131
Published: 26 August 2009
Abstract
Oocyte maturation in vivo is a highly orchestrated, induced process, whereby 3'-5'-cyclic adenosine monophosphate (cAMP)-mediated meiotic arrest is overridden by the gonadotrophin surge prior to ovulation. However, in vitro matured (IVM) oocytes resume maturation spontaneously hence compromising developmental competence. Hence we hypothesized that establishing an induced system in vitro would synchronise oocyte-somatic cell communication leading to improved oocyte quality. Bovine or mouse oocytes were treated for the first 1-2 h in vitro with the adenylate cyclase activator forskolin and a non-specific phosphodiesterase (PDE) inhibitor, IBMX, which substantially increased cumulus-oocyte complex (COC) cAMP (180 vs. 2 fmol/ COC , treated vs. control, P<0.001) to in vivo physiological levels. To maintain oocyte cAMP levels and prevent precocious oocyte maturation, oocytes were then cultured with an oocyte-specific (type 3) PDE inhibitor, cilostamide. The net effect of this system (“Induced IVM”) was to increase oocyte-somatic cell gap-junctional communication (bovine: 1000±148 vs. 340±73 units; treated vs. control, p<0.05) and to slow meiotic progression through prophase I to metaphase II, extending the normal IVM interval (bovine: 30 vs. 24h, mouse: 22 vs. 18 h; treated vs. control). These effects on oocyte and somatic cell functions had profound consequences for oocyte developmental potential. In bovine, Induced IVM more than doubled embryo yield (69% vs. 27%; treated vs. control, p<0.05). In mouse, Induced IVM increased blastocyst rate (86% vs. 55%; treated vs. control, p<0.05), implantation rate (51 vs. 25%), fetal survival rate (29% vs. 5%) and fetal weight (0.9g vs. 0.5g, p<0.01). All these developmental outcomes in mice were restored, by using Induced IVM, to levels obtained from in vivo matured control oocytes (conventional IVF). In conclusion, Induced IVM mimics some of the characteristics of oocyte maturation in vivo and substantially improves oocyte developmental outcomes. This should lead to an increase in the use of this technique in reproductive biotechnologies.
