Haitao ZENG (China)
Dr. Haitao Zeng is the A/Professor and the deputy director of Center of Reproductive Medicine, 6th affiliated hospital, Sun Yat-sen University, China. He has been working on obstetrical & gynecological, reproductive medicine as well as relevant research and education projects since 2001. He was recruited to work in OOCYTE Lab of Robinson Reproductive Research Institute, University of Adelaide in Australia as visiting scholar from 2011 to 2013, then working in Reproductive Medicine Center of the Sixth Affiliated Hospital of Sun Yat-sen University after returning home. He mainly focuses on studies of oocyte in vitro maturation. More than ten research foundations, such as the Chinese Natural Science Research Foundations, have sponsored him. He has published more than 20 research articles in international academic journals.
Advances in Clinical Practice of Human IVM
Since the first live birth from oocyte in vitro maturation (IVM) three decades ago. IVM has been suggested as an alternative to conventional IVF for avoiding the risk of ovarian hyperstimulation syndrome (OHSS), less cost and simplified treatments for patients. Advances in biology and methods of improving oocyte maturation have been evolved, leading to higher success rates and the new potential introduction of IVM into IVF clinics widely in the coming years. It is now clear that the gonadotrophin surge finely leads to a transient spike in cAMP in the somatic compartment of the follicle to induce oocyte maturation in vivo through epidermal growth factor (EGF) pathway net. In the present, IVM systems practiced in most IVF centers still had lower efficiency of IVM, at least partly due to not fully activating this cAMP surge and epidermal growth factor (EGF) pathway in vitro. By the way of the standpoint of cAMP/cGMP regulation, physiological maturation in vitro evokes what occurs in vivo through EGF network, at least in part, with a proper meiotic progression and significantly increased maturation rate, oocyte and embryo quality, implantation and pregnant rate, when compared with clinical IVF. It has recently been demonstrated that oocyte developmental potential was improved by changes in the components of basic culture medium, and supplementing IVM media with lower dose of FSH and exogenous OSFs, like bone morphogenetic protein 15 (BMP-15) and growth-differentiation factor 9 (GDF-9). When the follicles reach 5-8mm in human and bovine, oocytes take on the surrounded nucleolus (SN) or corresponding configurations and stop gene transcription, which demonstrate oocytes of this phase acquire the full meiotic competence for early embryonic development. The implications of these findings are particularly providing the strong evidence and theory supports for human IVM practice. The best time for oocyte collection is when a dominant follicle reaches a diameter of 14 mm in hCG-primed IVM cycles, but there is conflict whether or not the dominant follicle is affecting clinical outcome in no HCG-primed IVM cycles. Implantation and pregnancy rates were higher in thawed embryo transfer comparison to fresh embryo transfer. Relatively lower clinical efficiency that characterizes IVM might derive also from insufficient endometrial receptivity. Innovative strategy primed with FSH or exogenous hormonal administration might be necessary to achieve a correct endometrial growth. Combined FSH and hCG priming may represent the best option for patients, success rates benefit from the possibility to utilize oocytes already mature at recovery. The retrieve rate of GV oocytes is rarely exceeding 50-55%, and maturation rate is exceeding 60%, which are considerably lower than the proportion of oocytes found at the MII stage in a standard ovarian stimulation cycle (approximately 80%). Further improvements in IVM efficiency may help broaden the use of IVM for various infertility cause patients and fertility preservation.