Morphometric and ultrastructural features of the mare oviduct epithelium during oestrus.

The research investigates the structure and features of the epithelium, the lining of the oviduct, in mares during their oestrus, or heat cycle. Different techniques are used to display regional differences in this epithelium, ultimately suggesting that each region of the oviduct produces a unique microenvironment necessary for its specific function.

Overview of Methodology and Techniques

• The study employed morphometric analysis, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) to observe the oviductal epithelium’s structural characteristics.
• The epithelium was found to be comprised of two main cell types: ciliated and non-ciliated cells.
• These investigative techniques allowed for detailed observation of the morphological features of the oviduct regions, including the fimbriae, ampulla, and isthmus.

Findings on the Epithelium’s Composition and Structure

• The study found that the oviduct’s entire mucosa was covered with pseudostratified epithelium, a complex layer of cells with an irregular shape.
• Ciliated cells, which carry out functions with the aid of their hair-like structures called cilia, were dominant through all segments of the oviduct.
• The research observed variations in the presence of these cells based on the oviduct’s region, with an increased percentage from the fimbriae to the ampulla, and a significant decrease in the isthmus.

Spatial Differences in the Oviduct Regions

• In the infundibulum region, SEM revealed finger-like mucosal folds, some of which were connected.
• The ampulla, in contrast, had numerous and intricately branched folds of the mucosa.
• The isthmus, the narrowest part of the oviduct, presented a narrow lumen with short, non-branched mucosal folds.

Cellular and Molecular Features

• Both ciliated and non-ciliated cells presented varied ultrastructural features along the oviduct.
• Non-ciliated cells of the infundibulum did not contain secretory granules but showed apical endocytic vesicles coated with a well-developed glycocalyx—a protective and functional layer of the cell membrane.
• On the other hand, non-ciliated cells in the ampulla and isthmus contained secretory granules, further pointing out regional differences within the oviduct.
• Three types of granules were observed in the isthmus non ciliated cells, and the cells in this area exhibited either electron-lucent or electron-dense cytoplasm.

Conclusion and Implications

• The observed regional differences along the epithelium lining the mare oviduct suggest that each segment’s epithelium is involved in generating a unique microenvironment.
• This unique biochemical milieu could be linked to each segment’s functional role, possibly tailoring to the specific physiological requirements during the oestrus period.