Histocytological Changes in the Wistar Rat Ovary at Different Pubertal Stages and Pregnancy

The ovary is a vital organ in the female reproductive system, responsible for housing follicles, which contain oocytes essential for procreation. Although many studies have examined specific aspects of ovarian development in Wistar rats, there is a need to compare microanatomical features of the Wistar rat ovary across developmental stages. This study provides comparative microscopic details of the ovary across three key developmental stages: pre-puberty, puberty, and pregnancy. A total of twenty Wistar rats were procured. Three of the female rats gave birth; their pups were nurtured and then assigned to the pre-pubertal and pubertal groups. Ovarian tissues were collected at day 21, post-vaginal opening, and designated gestational days. Pre-pubertal ovaries were predominantly composed of primordial, primary, secondary, and tertiary follicles, with the absence of corpora luteum or pre-ovulatory follicles; the stroma was dense, cellular, showing spindle to plump cells with oval nuclei. In contrast, pubertal ovaries exhibited a full spectrum of follicular development, presence of pre-ovulatory follicles and corpora lutea indicative of ovulation; the stroma was loose and showed predominance of plump cells. During pregnancy, the ovarian structure was characterized by large corpora lutea occupying most of the ovarian space, accompanied by reduced folliculogenesis and pronounced vascular expansion. The corpora lutea cells were large, polygonal; their cytoplasm was abundant, eosinophilic to clear, and varied from granular to vacuolated as the pregnancy progressed. This study highlights changes in the histoarchitecture and cytoarchitecture of the ovary across the three main developmental stages of female reproductive life.

Key Words: microanatomy, Wistar rat, ovary, pre-puberty, puberty, pregnancy