Cellular Bioenergetics Effects of Sirolimus on the Gonads of BALB/c Mice

Background Sirolimus, an immunosuppressive drug widely used in organ transplantation, inhibits the mechanistic target of rapamycin (mTOR), decreases cellular respiration, stops cell cycle progression and causes apoptosis. It has been linked to cytotoxicity in the gonads, but the cause is unknown. Aims To understand the effects of sirolimus on the gonads by measuring cellular respiration and ATP as indicators of cellular damage, and examining histological changes. Material and Methods We used 6-8 week old male and female BALB/c mice. They received 5 µg/g sirolimus via intraperitoneal injections for 5 consecutive days per week for up to 3 weeks (treated group) or DMSO (control group). Upon euthanasia, the gonads were promptly removed while the heart was still beating, weighed, and processed for cellular respiration, ATP measurement, and histological studies. Cellular respiration was measured using a phosphorescence oxygen analyzer and ATP using a bioluminescent assay system. Histology was performed using processed tissue fragments stained with hematoxylin and eosin (H&E). Results Cellular ATP levels in testicular tissue were higher than ovarian tissue in both groups, but this was not significant ( p =0.4 and 0.2). Although the sirolimus group had higher cellular ATP levels, no significant difference was observed in either testicular (p=0.6) or ovarian ( p =0.9) tissue. Both DMSO ( p =0.01) and sirolimus groups ( p =0.008) showed lower cellular respiration in ovarian than testicular tissue. Cellular respiration was lower in sirolimus group than DMSO group in both testicular ( p =0.6) and ovarian ( p =0.2) tissue. Testicular cellular respiration remained unchanged up to day 11 before declining, while ovarian respiration reduced up to day 11 and remained unchanged. Testicular histopathology showed normal sperm production and normal follicular development in ovarian tissue. Conclusion The results suggest that the 5 µg/g dose of sirolimus does not cause significant short-term changes in the cellular bioenergetics of the gonads or produce noticeable histopathological changes.