The mitochondrial targeted antioxidant Mitoquinol increases survival of isolated human preantral follicles in vitro

Abstract Study question Does Mitoquinol have a protective effect on survival and mitochondrial oxidative stress in cultured human preantral follicles? Summary answer Mitoquinol significantly increased survival of human preantral follicles cultured for 8 days and significantly decreased expression of genes related to the mitochondrial oxidative stress response. What is known already Culturing human ovarian follicles is a promising new source of mature oocytes for fertility preservation, as well as a key model system to investigate fundamental biology. Nevertheless, only a handful of studies have yielded mature human oocytes from preantral stage follicles and optimizing culture systems is challenging due to the scarcity of human material. Mitoquinol is an antioxidant that contains a form of Coenzyme Q10 called ubiquinone that has been modified to selectively target and protect mitochondria from oxidative damage. In human oocytes, the presence of Mitoquinol in the IVM media increased nuclear maturation and protected against chromosomal misalignment. Study design, size, duration Human preantral follicles (n = 213; mean diameter: 71 µm; range: 26-189 µm) were isolated from ovarian medulla tissue. Preantral follicles were mechanically and enzymatically isolated, encapsulated in 0.5% alginate and cultured for 8 days in three experimental groups: Control (n = 68); 50nM Mitoquinol (n = 71), 250nM Mitoquinol (n = 74). The primary endpoints were follicular growth and survival. Secondary endpoints included follicular gene expression and hormone analysis of the spent culture media. Participants/materials, setting, methods Ovarian medulla tissue was donated by 5 patients (aged 30-37 years) undergoing unilateral oophorectomy for ovarian tissue cryopreservation. Follicular growth and survival were assessed every second day during culture by microscopy. For follicles bigger than 95 µm, AMH and Estradiol concentrations were measured by ELISA in the spent media on day 8. Finally surviving follicles were snap-frozen and gene expression was analysed by qPCR; mitochondrial oxidative stress genes: HSP-60, TFAM and apoptosis genes: BAX/BCL-2. Main results and the role of chance After 8 days in culture, the follicular survival rate in the 50nM Mitoquinol group (68%; n = 51/74) was significantly higher than the control group (49%; n = 32/68; p = 0.0344) and the 250nM Mitoquinol (54%; n = 39/71; p = 0.0443). The protective effect of 50nM Mitoquinol was more pronounced in the subset of small follicles (Day0 < 70 µm, n = 135) in which survival rate of the 50nM Mitoquinol group (65%; n = 31/47) was significantly higher than the control (41%; n = 18/43; p = 0.005) and the 250nM group (44%; n = 20/4; p = 0.019). The average growth of surviving follicles was similar in the three experimental groups (Control: 40.7 ± 17.4 µm; Mitoquinol 50nM: 36.9 ± 19 μm; Mitoquinol 250nM: 36.4 ±16.5 μm). A significant positive association between the diameter of the follicle and the concentration of AMH and Estradiol was observed (AMH: p = 0.0215, R = 0.43 and Estradiol: p = 0.0413, R = 0.38) but no differences were found between the experimental groups. The relative expression of genes involved in mitochondrial oxidative stress response were significantly lower in the 50nM Mitoquinol group compared to the 250mM Mitoquinol group (HSP-60 p = 0.018; TFAM p = 0.013) and similar to the control group (HSP-60 p = 0.056; TFAM p = 0.071). Moreover, the gene expression of the ratio BAX/BCL2 was similar in the three groups. Limitations, reasons for caution A larger sample size is required to confirm the statistical analysis and to extrapolate the results to primordial, primary, and secondary stage follicles. Furthermore, long-term culture studies are required to determine the impact of Mitoquinol on antral follicle development and oocyte maturation Wider implications of the findings Our findings show that Mitoquinol can be used as an antioxidant in the culture of human preantral follicles since it increased follicle survival and reduced gene expression of genes related to mitochondrial oxidative stress response. Trial registration number Not appliclable