A preliminary investigation of gene expression and levels of FSH, IL-10, and TNF-α and histological staining in natural aging mice

Objective: This study aimed to compare estrous cycle patterns, serum hormone and cytokine levels, gene expression, and ovarian morphology between healthy and aging mice, to evaluate their potential as models of reproductive aging. Materials and Methods: Female BALB/c mice older than 9 months were used as the aged group and were compared with healthy controls (6-8 weeks old). Estrous phases were monitored for six days using vaginal cytology. Ovarian morphology was analyzed using hematoxylin and eosin staining and immunohistochemistry. Serum levels of follicle-stimulating hormone (FSH), interleukin (IL)-10, and tumor necrosis factor-alpha (TNF-α) were measured by enzyme-linked immunosorbent assay. Gene expression of IL-10 and TNF-α was assessed by reverse transcription polymerase chain reaction. Results: Healthy mice cycled through all estrous phases, whereas aging mice were predominantly arrested in diestrus and exhibited increased immune-cell infiltration and inflammatory changes. Ovarian histology showed enlargement, fibrosis, and the presence of non-functional structures. Follicle counts were reduced in aging mice, though the reduction was not statistically significant. Serum FSH (1.37±0.20 vs. 1.10±0.03 pg/mL) and TNF-α (37.05±17.31 vs. 21.57±4.62 pg/mL) were significantly elevated, whereas IL-10 was significantly decreased (4.53±0.32 vs. 6.23±0.99 pg/mL) (p