Role of myo -inositol in the in vitro maturation of mammalian oocytes.

摘要

Myo-inositol (MI) is an isomer of a C6 sugar alcohol that belongs to the vitamin B complex group. Various studies have suggested that MI plays an important role in cell morphogenesis and cytogenesis, lipid synthesis, structure of cell membranes and cell growth. We have previously shown that MI may be a serum trophic factor responsible for promoting in-vitro development of preimplantation mouse embryos. Other studies have subsequently shown that MI is incorporated into phosphoinositides and inositol phosphates in rabbit embryos and promotes blastocyst formation in bovine embryos. Taken together, the results of these studies support the notion that MI serves as a precursor for the synthesis of phosphoinositides. These constitute the phosphatidyl-inositol (PtdIns) signal transduction system that regulates the release of intracellular Ca2+ and this, in turn, controls diverse cellular functions like cell proliferation.;In this dissertation, we hypothesized that exposure of fully-grown, germinal vesicle (GV) stage oocytes to MI could enhance their meiotic maturation and subsequent developmental competence following fertilization. In order to verify our hypothesis, we initially investigated the presence of MI in human follicular fluids obtained from patients undergoing our in-vitro fertilization (IVF) program, and correlated the MI concentrations with the quality of the oocyte that came from the respective follicle and the outcome of IVF. In the second part of our study, we examined the effects of MI on the kinetics of GV breakdown (GVBD) and progression to full maturation of GV-intact mouse oocytes, their fertilizability, and subsequent embryonic development and implantation potential of embryos derived from these in-vitro matured (IVM) oocytes. The last section of our study comprised of the investigation of intracellular Ca2+ events of the GV-intact mouse oocytes after exposure to MI during the early stage of oocyte maturation.;We conclude that MI is present within the follicles and may provide a novel marker of good quality oocytes. The addition of MI into an oocyte maturation medium can enhance the in-vitro maturation of GV-intact oocytes and their subsequent development potential possibly related to its effect on mobilization of intracellular Ca2+. This study provides an important contribution to a better understanding of follicular environment during oocyte maturation and, in turn, may improve the overall efficacy of in-vitro maturation of human oocytes.