Evaluation of Plasma Cell Counts and CD138 Expression in the Rat Uterus Following Capsaicin Treatment at Different Developmental Stages

Capsaicin, the bioactive component of chili peppers, has been reported to exert analgesic, anti-inflammatory, antimicrobial, and chemopreventive effects. The immunomodulatory properties of capsaicin are suggested to vary depending on the tissue microenvironment and developmental stage. The study aimed to evaluate the effects of capsaicin administered at different developmental periods on plasma cell counts and CD138 expression levels in the rat uterus. Sixty female Sprague–Dawley rats (21 days) were randomly assigned to pubertal and adult groups and exposed to the respective experimental conditions until reaching 42 or 70 days of age. Each group was further subdivided into control, vehicle, and capsaicin treated groups. At the end of the experimental period, uterine histological architecture was assessed. Plasma cells were identified by Methyl Green–Pyronin staining, and CD138 expression was analysed immunohistochemically. Histochemical evaluation revealed a significantly lower number of plasma cells in the vehicle group compared with the control group during puberty, whereas no significant differences were observed among groups in adulthood. Notably, plasma cell counts increased with age in the vehicle and capsaicin groups, while no age-related change was detected in the control group. Immunohistochemical analysis revealed no significant differences among treatment groups within each developmental stage; however, a significant increase in CD138-positive cells was observed in the adult capsaicin group compared with the pubertal capsaicin group. In conclusion, the effects of capsaicin on uterine plasma cell dynamics appear to be influenced by developmental stage, and the method used for evaluation may affect the interpretation of immune-related changes.