The mRNA expression of MT-encoded genes of OXPHS in ovarian GCS of infertile women and the effect of NMN on expression of MT-encoded genes in SVOG cells

Abstract

To detect the mRNA expression of mitochondria(mt)-encoded genes in oxidative phosphorylation system(OXPHS) in ovarian granulosa cells(GCs) of infertile women with advanced age or poor ovarian response(POR), and to explore the relationship between mRNA expression with in vitro fertilization(IVF) outcomes. In addition, effect of nicotinamide mononucleotide(NMN)-a NAD+ precursor on mRNA expression of mt-encoded genes in OXPHS is to be detected. Retrospective and experimental study. 45 infertile women were divided into the old group(>= 37 years old), the young group(< 37 years old) with POR and the young group with normal ovarian response(NOR). On the day of oocyte retrieval, GCs were purified from follicular fluid in all the patients for use. In separate experiments, immortalized human granulosa(SVOG) cells were treated with nicotinamide mononucleotide(NMN) or NMN adenylyltransferase-1(NMNAT-1) small interfering RNA(siRNA) to see effect of NMN on expression of mt-encoded genes in OXPHS. Real-time quantitative PCR was conducted to detect the mRNA expression of mt-encoded genes CYB, ND1, ATP6, CO1 and nuclear(nu)-encoded genes ATP5A1, SDHB, UQCRC1, NDUFS8 in GCs or SVOG cells. mRNA expression in different groups and the relationship with IVF outcomes, such as number of retrieved oocytes, achievement of good quality embryos, clinical pregnancy or live birth were evaluated by Kruskal-Wallis H test, Mann-Whitney or one-way ANOVA as appropriate. The mRNA expression of the mt-encoded genes in young POR group and old group were significantly lower than young NOR group, besides patients who retrieved more than 3 oocytes or had high quality embryos showed higher mt-encoded genes expression in GCs. In SVOG cells, the expression of mt-encoded genes was significantly decreased in the NMNAT-1 gene knockdown group compared with control and control+NMN group. Additionally, there were no significant differences in the mRNA expression of nu-encoded genes among these groups in GCs or SVOG cells. Young POR and old infertile patients may have impaired mitochondrial function in GCs. Higher expression of mt-encoded genes in GCs implies good ovarian response and high quality embryos. Besides, supplementation of NAD+ precursors such as NMN may restore mitochondrial function and prevent ovarian cell aging.