The use of superovulation for human in vitro fertilization-embryo transfer-(IVF-ET) produces a cohort of oocytes that can be of varing levels of maturity. Mature oocytes are incubated for 5 to 6 hours before sperm insemination, whereas immature
oocytes
are cultured for 20 to 36 hours before they are inseminated, but the fertilization rate for immature oocytes matured in vitro remains below than those achieved with mature oocytes.
There have been reported that successful in vitro maturation of animal oocytes were achieved by culture alone, by adding gonadotropins or specific growth factors to that medium, or by coculture on the top of granulosal cells.
To increase the fertilization and early embryo development, immature oocyte of mouse(ICR) were cocultured with human uterine epithelial cells isolated from uterine stromal cells by highly purified method.
The coculture system improved in vitro maturation of immature mouse oocyte by full expansion of cumulus cells(86% vs 41.5%) and extrusion of first polar body(58% vs 45.4%) in comparison with medium alone. The fertilization rates(58% vs 32.8%) and
embryo
cleavage rate(20.2% vs 9.2%) of in vitro maturated immature oocyte were improved in coculture system. When mouse 1-cell embryo were cocultured on the top of monolayer of human uterine epithelial cells, embryo development rates(>4 cell embryo )
were
significantly higher than control group (45.4% vs 16.6%). The in vitro fertilization rates of mature oocytes(87.2% vs 79.9%) were increased in coculture system that showed good quality of embryo in subsequent embryo development, reducing in
fragmentation(3.1% vs 26%). In conclusion, when cocultured with mouse immature oocytes, mature oocyte, and early embryos, human uterine epithelial cells improved the rate of in vitro maturation of oocyte, fertilization and early embryo
development,
respectively. This suggests that the application of a permanent established stable endometrial cell line to assisted reproductive techniques may allow better results in selection of embryo for transfer therefore improve the following pregnancy.
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