In vitro developmental competence of horse embryos derived from oocytes with a different corona radiata cumulus-oocyte morphology.

The study investigates the development potential of horse embryos conceived in a laboratory, considering different egg cell structures. The authors found that embryos from eggs with different structures developed similarly, suggesting all such eggs may be equally valuable for horse embryo production.

Objective of the Study

• The objective of this study revolves around addressing the demand for in vitro produced horse embryos, which is currently a growing trend in commercial laboratories. Despite this demand, the production rate of blastocysts is comparatively low in these settings.
• The research aimed to compare the in vitro embryo development capacity of cumulus-oocyte-complexes (COCs) collected from horses, including those with only a corona radiata, a structure often found after aspiration procedures.

Methods

• Horse oocytes were collected by aspirating follicles from ovaries obtained from an abattoir. These oocytes were then grouped based on their morphology into expanded, compact or corona radiata COCs.
• After the classification, these COC oocytes were matured and fertilized in vitro through intracytoplasmic sperm injection (ICSI) and further cultured for 7.5 days.
• The researchers then recorded three parameters: the maturation rate, the cleavage rate, and the morula or blastocyst rates, to analyze the development potential of these embryos.

Findings

• The study did not find significant differences (P > 0.05) among the three groups in terms of their maturation rate. However, the cleavage rate was less (P < 0.05) for embryos derived from oocytes with corona radiata, compared to those derived from compact COCs.
• Despite a difference in cleavage rates, the embryo development after 7.5 days of culture remained similar among all groups (P > 0.05).

Conclusion

• The study concluded that despite the lower cleavage rate in embryos resulting from oocytes with a corona radiata structure, their developmental capacity was similar to those derived from oocytes with a compact and expanded cumulus morphology.
• This result implies that oocytes with a corona radiata can be equally useful in the production of horse embryos, potentially expanding the sources of eggs that can be used in the in vitro production of horse embryos.