Influence of oocyte collection technique on initial chromatin configuration, meiotic competence, and male pronucleus formation after intracytoplasmic sperm injection (ICSI) of equine oocytes.

The research study investigates the impact of oocyte collection techniques on the chromatin configuration, meiotic competency, and male pronucleus formation in horse oocytes after undergoing intracytoplasmic sperm injection (ICSI). The results demonstrated statistical differences in certain aspects based on the collection method used, with the scraping method producing a higher prevalence of diffuse chromatin within the germinal vesicle, and the aspiration technique leading to a higher rate of abnormal fertilization.

Research Goals and Methods

• The primary aim of the research was to evaluate if the method of oocyte collection influences the meiotic and developmental capability of horse oocytes and could hence account for the varying success rates in laboratories across the globe.
• The horse oocytes were retrieved from abattoir ovaries either through scraping or aspiration techniques.
• The attributes of oocytes, such as cumuli constitution—compact (Cp), expanded (Ex), or partial (P)—were also taken into consideration.
• The study was split into three experiments. The first sought to determine if the collection method affected the chromatin configuration via immediate fixing post collection. The second experiment compared the maturation rates of the oocytes recovered by aspiration and scraping. While in the final experiment, in vitro matured oocytes underwent ICSI.

Research Findings

• The initial chromatin configuration differed depending on the collection technique. Oocytes collected using the scraping method had a significantly higher occurrence of diffuse chromatin within the germinal vesicle compared to those collected through aspiration.
• The maturation rate to metaphase II showed no significant difference between oocytes retrieved through the two different methods.
• OTR reports on pronucleus formation rates following ICSI demonstrated no significant difference based on the collection method. However, there was a notable higher rate of abnormal fertilization in oocytes collected through aspiration versus those collected through scraping.

Conclusions

• The findings from the research suggest that the oocyte collection method influences the population of the recovered oocytes and might contribute to the disparity in outcomes among laboratories specializing in equine oocyte research.
• The scraping method led to a higher presence of diffuse chromatin within the germinal vesicle, while the aspiration technique resulted in higher abnormal fertilization rates, possibly offering insights into areas of improvement in laboratory practices.