Morphological Changes in Vagina and Ovary Throughout Estrous Cycle in Galea spixii (Rodentia: Caviidae Wagler, 1831)

The rodents Spix's yellow-toothed (SYT) cavies (Galea spixii, Wagler, 1831) belong to the family Caviidae and are found in Brazilian northeast where they are used as source of protein for inhabitants of that region. For this reason, the species is bred in captivity for the preservation and to use as experimental model for research on reproductive biology. During the estrous cycle, the vaginal epithelium is influenced by different demands of sexual steroid hormones produced by ovarian follicles at different stages of development and this fact is related to the different cell types found in samples of vaginal exfoliative cytology. Present study aimed to determine if the characterization of the estrous cycle in females of SYT cavies by vaginal exfoliative cytology were corresponding with microstructural variations in vaginal epithelium revealed by proliferating cell nuclear antigen (PCNA) and to the follicular development in the ovaries at different phases of the estrous cycle. After determination of the estrous cycle phases by vaginal exfoliative cytology, females were euthanized at metestrus, diestrus, proestrus and estrus phases (n=3 for each estrous cycle phase). Histological study of the vaginal epithelium and ovary were performed and besides, immunohistochemistry for proliferating cell nuclear antigen (PCNA) was performed using samples of vaginal tissue at each estrous cycle phase. Present data shows that the vaginal exfoliative cytology may be associated with the follicular development in the ovaries and the proliferation and desquamation of the vaginal epithelium in SYT cavies. At estrus, superficial cornified cells in vaginal exfoliative cytology and vaginal epithelium besides early post-ovulatory follicles in ovaries were found. At metestrus, the vaginal epithelium undergone desquamation and lost the superficial cornified cells; basal and intermediate cells appeared in the vaginal exfoliative cytology and post ovulatory follicle formed early corpus luteum. At diestrus, corpus luteum was developed and the vaginal epithelium showed basal and intermediate cells by vaginal exfoliative cytology. At proestrus, due to the growth and maturation of ovarian follicles, the vaginal epithelium suffered intense proliferation. Vaginal exfoliative cytology showed large intermediate cells and nucleated and enucleated superficial cornified cells. In the ovary, mature follicles were present. PCNA was present in vaginal tissue at diestrus, proestrus and estrus but not at metestrus. In summary, present data shows association between the findings by vaginal exfoliative cytology, changes in microstructure of vaginal epithelium; proliferating cell nuclear antigen (PCNA) expression; and, follicular development in the ovaries.