In vitro maturation of human oocytes maintaining good development potential for rescue intracytoplasmic sperm injection with fresh sperm

BACKGROUND The outcomes of the use of commercial in vitro maturation(IVM)medium to culture immature oocytes obtained from conventional ovulation induction,followed by rescue intracytoplasmic sperm injection(RICSI),are not ideal.It is thus difficult to widely adopt this approach in clinical practice.Therefore,it is necessary to explore methods for improving the clinical outcome of IVM.AIM To study the effect of sperm on the developmental potential of in vitro-matured oocytes in conventional culture.METHODS This was a retrospective study of patients whose immature oocytes were harvested from conventional oocyte stimulation cycles and underwent ICSI at our hospital between June 2018 and August 2020.RICSI was performed using sperm collected on the day of oocyte harvest(old)and sperm collected on the day of RICSI(fresh)and oocytes matured in vitro after 24 h of culture in conventional medium.The rates of in vitro oocyte maturation,normal fertilization,normal cleavage,day-3 top-quality embryos,and useful blastocyst formation were compared between the two groups.RESULTS In total,102 germinal vesicle(GV)-stage immature oocytes were cultured in the old sperm group.In the fresh sperm group,122 GV-stage immature oocytes were collected and cultured in vitro for 24 h.There were no significant differences in the general conditions of males and females between the two groups(P>0.05).The oocyte maturation,normal fertilization,and normal cleavage rates of the old and fresh groups were 51.0%vs 55.7%,61.5%vs 64.7%,and 93.8%vs 93.2%,respectively.None of the rates differed significantly(P>0.05)between the two groups.However,the day-3 top-quality embryo and useful blastocyst rates of the old and fresh sperm groups were 16.6%vs 63.4%;6.67%vs 34.6%,respectively.The day-3 top-quality embryos and useful blastocyst rates of the old sperm group were significantly lower than those of the fresh group(P<0.05).CONCLUSION In vitro maturation with conventional culture medium combined with the use of fresh sperm collected on the day of RICSI is an easy-to-implement strategy for patients whose oocytes are completely or mostly immature.

Current perspectives on in vitro maturation and its effects on oocyte genetic and epigenetic profiles

In vitro maturation(IVM), the maturation in culture of immature oocytes, has been used in clinic for more than 20 years.Although IVM has the specific advantages of low cost and minor side effects over controlled ovarian stimulation, the prevalence of IVM is less than 1% of routine in vitro fertilization and embryo transfer techniques in many reproductive centers. In this review, we searched the MEDLINE database for all full texts and/or abstract articles published in English with content related to oocyte IVM mainly between 2000 and 2016. Many different aspects of the IVM method may influence oocyte potential,including priming, gonadotrophin, growth factors, and culture times. The culture conditions of IVM result in alterations in the oocyte or cumulus cell transcriptome that are not observed under in vivo culture conditions. Additionally, epigenetic modifications, such as DNA methylation or acetylation, are also different between in vitro and in vivo cultured oocytes. In sum,current IVM technique is still not popular and requires more systematic and intensive research to improve its effects and applications. This review will help point our problems, supply evidence or clues for future improving IVM technique, thus assist patients for fertility treatment or preservation as an additional option.