Effect of ovarian growth factors on ultra-structural maturation in frozen human immature oocytes after in vitro maturation: a comparative study

Background: In artificial reproductive technique (ART), nearly 20% of human oocytes are immature in the germinal vesicle (GV) phase. Consequently, the best method for reserving them is cryopreserving GV oocytes, and in vitro maturation (IVM) is recommended. The aim of this study was to determine the ultrastructure characteristics of fresh and vitrified immature human oocytes after in vitro maturation in conditioned mediums. Methods: This study was a comparative laboratory study carried out in 2018 at Afzalipur Infertility Center in Kerman. 170 fresh and 198 vitrified GV oocytes were cultured within three IVM mediums; alpha-mem as control medium, alpha-mem supplemented with human bone marrow mesenchymal stem cells (BM-MSCs) and alpha-mem supplemented with ovarian growth factors (O.F). After 48 h, the maturation rate and morphological feature of IVM oocytes [132 fresh IVM (fIVM) and 134 vitrified IVM (vIVM)] were evaluated. For the ultrastructure study, 10 IVM oocytes from each medium were compared with 10 fresh in vivo oocytes cancelled from ART. Results: The survival rate of vitrified GV oocyte after thawing was 88.88%. The oocyte maturation rate was reduced in vIVM compared to the fIVM group (76.33% vs. 77.95%); the highest oocyte maturation rate in the O.F fIVM and lowest in alpha-mem vIVM (82.35% vs. 71.42%). The lowest number of cortical granules was observed in alpha-mem vIVM, but the greatest presence of M-SER aggregates was in O.F fIVM. In vIVM oocytes, the oolemma contained irregular little microvillus organization. Conclusions: The O.F mediums have shown the highest maturation which defends the oocyte ultra-structural conservation.

Automated summary

The study compared the ultrastructure characteristics of fresh and vitrified immature human oocytes and found that O.F medium had the highest maturation rate, preserving the ultrastructure of oocytes.