Objective: Due to previously low success rates, in vitro maturation is under utilized in the rescue of immature oocytes retrieved following standard ovarian hyperstimulation. In many fertility clinics, any immature oocytes are deemed unusable and are discarded at the time of intracellular sperm injection (ICSI). The objective of this study is to examine the utilization of human induced pluripotent stem cell (hiPSCs) derived ovarian support cells (OSCs) in a novel co-culture system for the improvement of rescue human oocyte in vitro maturation.
Materials & Methods: 141 immature oocytes were donated from 47 patients aged 25 to 45 with no other exclusion criteria in this study. Patients underwent typical ovarian hyperstimulation (gonadotropin releasing hormone analogs, recombinant FSH, or human menopausal gonadotropins) followed by an ovulatory trigger (human Chorionic Gonadotropin (hCG)or GnRH agonist) 34-36 hours prior to retrieval. Oocytes were retrieved using the clinic’s standard procedure, denuded, and assessed for maturity. Any immature oocytes, including germinal vesicles (GV) and Metaphase I (MI) were transported from the clinic to the lab, pooled in batches, and placed in pre-maturation media (LAG) for 2 hours prior to co-culture. After the pre-maturation step, immature oocytes were then randomly and evenly distributed between two conditions: Media-IVM (commercially available IVM media supplemented according to manufacturer’s instructions with the addition of Androstenedione and doxycycline; n=59) and OSC-IVM (the same media composition with the addition of 100,000 OSCs per 100ul; n=82). After 24 hours oocytes were stripped of any attached cells, then assessed for maturity and quality. Each oocyte was individually imaged, and matured oocytes were graded using the Total Oocyte Scoring (TOS) system, which scores oocytes on a morphology, size, cytoplasm, zona pellucida, perivitelline space, and polar body. Results were analyzed using unpaired t-test.
Results: The maturation rate of the oocytes cultured in the Media-IVM condition was 37%,8.96% SEM. In comparison, the OSC-IVM co-culture condition yielded a strikingly improved oocyte maturation rate of 62% 5.57% SEM (p=0.0138, unpaired t-test). No significant difference in oocyte quality according to the TOS system was observed between the OSC-IVM and the Media-IVM conditions.
Conclusions: Comparison of supplemented Media-IVM and OSC-IVM oocyte co-culture conditions revealed that OSC-IVM supports a statistically significant improvement in oocyte MII formation. No difference was observed in the morphological quality of oocytes from either condition, indicating no adverse impact of OSC-IVM treatment on oocyte quality.
Impact Statement: The use of human induced pluripotent stem cell (hiPSCs) derived ovarian support cells (OSCs) in a co-culture system is a novel and beneficial approach to in vitro maturation of rescued immature human oocytes.