Cytology and Histology of the Vaginal Epithelium at Different Stages of the Wistar Rat’s Oestrous Cycle

Abstract

Background: The vagina plays a vital role in the female reproductive system and undergoes several histological changes influenced by hormonal variations throughout different life stages and reproductive cycles. There are a few studies that provide detailed accounts of both cytological and histological changes in the vaginal epithelium across the oestrous cycle. Objective: This study aimed to examine the microanatomy of the vaginal epithelium of Wistar rats at different stages of the oestrous cycle. Methodology: A total of 20 female Wistar rats were randomly assigned to 4 groups, each representing a phase of the oestrous cycle. The rats were maintained under standard laboratory conditions with access to feed and clean water only. The vaginal epithelial cells were collected by gentle saline wash, a smear was made on clean glass slides, the slides were air-dried and fixed in methanol. The slides were stained with Field stains A and B to identify the predominant cell types and determine the phase of the oestrous cycle. The rats were euthanised, and vaginal tissues were harvested and processed for haematoxylin and eosin staining. Results: Pro-oestrus phase cytology showed a predominance of basal and intermediate cells. Histology showed a double layer of basal cells and multiple layers of intermediate cells, no cornified cells. Oestrus phase cytology showed abundant cornified epithelial cells. Basal cells and intermediate cells were rarely seen. Histology showed stratified epithelium with a predominance of cells with pyknotic nuclei. Metoestrus/dioestrus cytology showed a predominance of leukocytes, mainly neutrophils, and few intermediate cells. Histology showed a single layer of basal cells, intermediate cells, scant superficial cells, and intraepithelial inflammatory cells. Conclusion/ Recommendations: These findings highlight a well-defined pattern of cyclical epithelial growth, differentiation, regression, and immune activity under hormonal control. Further research, such as immunohistochemistry, gene expression profiles as well as comparisons with aged or diseased animal models, is warranted to expand its scope.