Influence of co-culture during maturation on the developmental potential of equine oocytes fertilized by intracytoplasmic sperm injection (ICSI).

The research article investigates the impact of co-culture with two different types of cells—oviduct epithelial cells and fetal fibroblast cells—on the successful maturation and fertilization of equine oocytes. The study found that when maturing in co-culture, the oocytes developed into a higher proportion of blastocysts than when they matured in isolation.

Research Methodology

• The oocytes (egg cells) used in this study were procured from horse ovaries collected at abattoirs. These cells were matured in a lab setup for approximately 28 to 30 hours.
• Three different environments were set up for the oocytes to mature in. These were plain TCM-199 (a type of cell culture medium), TCM-199 supplemented with oviduct epithelial cells, and TCM-199 mixed with fetal fibroblast cells. Oviduct epithelial cells are the cells lining the fallopian tubes, while fetal fibroblast cells are cells obtained from an unborn animal that produces collagen and other types of connective tissue.

Process of Intracytoplasmic Sperm Injection (ICSI)

• The protocoled ICSI started by injecting a sperm, previously treated with a chemical called ionomycin, inside the oocyte.
• The successfully injected oocytes were then cultured for a further 7 to 9 days in an environment that contained Dulbecco’s modified Eagle’s medium—an optimal solution widely used for biological and medical research.
• Morphologically normal early-stage blastocysts derived from these cell clusters were then carefully transferred into the uterus of recipient mares.

Results and Significance

• The rates of cell divisions up to the two-cell stage were statistically consistent across all the groups—TCM-199 at 49%, co-culture with oviduct epithelial cells at 53%, and co-culture with fetal fibroblasts at 51%.
• Oocytes that were co-cultured with either oviduct epithelial cells or fetal fibroblasts showed a significantly higher rate of development into blastocysts than those matured in TCM-199 only (30% and 17%, respectively compared to the latter’s <5%).
• Of the blastocysts developed from oocytes co-cultured with oviduct epithelial cells, six were transferred to recipient mares with four resulting in successful pregnancies.
• These results suggest that co-culturing equine oocytes with either oviduct epithelial cells or fetal fibroblasts significantly improves their developmental potential during in vitro maturation, thus proving beneficial in equine fertility research and application.