Ethanol, Carnoy, and paraformaldehyde as fixative solutions for histological evaluation of preantral follicles in equine ovarian tissue.

This study investigated the effectiveness of three fixative solutions (ethanol, Carnoy’s solution and paraformaldehyde) for preserving the cellular structure of equine ovarian tissue for fertility studies. Among the three, Carnoy’s solution yielded the best results, although using 70% ethanol for a short time is also feasible when faster evaluations are required.

Research Purpose and Methodology

• The goal of this research was to determine the most suitable fixative solution for preserving equine ovarian tissue. This is of significant importance for reproduction studies and fertility preservation in horses.
• Three fixative solutions were tested in the study: a short-time exposure to a 70% ethanol solution, Carnoy’s solution, and a 4% paraformaldehyde solution. The latter two are traditional fixatives.
• The solutions were tested at varying exposure times (6 or 12 hours).
• The extracted ovarian tissue was structured into fragments (3 × 3 × 1 mm in size), then fixed into the different solutions.
• The effects of the fixatives were evaluated by examining the morphology and classes of preantral follicles, follicular and stromal cell densities, and follicular and oocyte nuclear diameters.

Research Findings

• The researchers looked at 11,661 preantral follicles through 1,444 histological slides to get their results.
• Between the three solutions, Carnoy’s solution produced the highest percentage of normal preantral follicles and had the highest stromal cell density.
• The short-term ethanol treatment, however, matched the results produced by paraformaldehyde, regardless of the exposure time.

Conclusions and Future Research

• Based on the results, the researchers concluded that Carnoy’s solution should be favored over both short-term ethanol and paraformaldehyde for studies concerning the cellular structure of equine ovarian tissue.
• However, for a rapid evaluation, short-term ethanol could be an efficient alternative to more time-consuming and costly methods.
• The study stressed the need for more research to assess how the different fixative solutions impact the ultrastructure of cellular populations and their compatibility with immunohistochemistry (IHC) and molecular techniques applied in equine ovarian tissue.