The treatment based on calcineurin inhibitors and their conversion to sirolimus alter the morphology in the rat testis

The effects of three-drug immunosuppressive regimens on the testis are still not fully known. The aim of this study was to evaluate the long-term effects of immunosuppressive protocols based on calcineurin inhibitors (CNIs) and their conversion to monotherapy with sirolimus on morphology, proliferation, and nuclear DNA fragmentation in the male gonad using an experimental model. For 6 months, male Wistar rats were treated with cyclosporin A (CsA), tacrolimus (FK-506), sirolimus (SRL), mycophenolate mofetil (MMF), and prednisone (Pred). The following protocols were used: CMP (CsA, MMF, and Pred), CMP/S (CsA, MMF, and Pred with conversion to SRL), TMP (FK-506, MMF, and Pred), and TMP/S (FK-506, MMF, and Pred with conversion to SRL). Morphological analyses, including morphometric analysis, immunohistochemical evaluation for proliferation (Ki67), and nuclear DNA fragmentation using the terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) method in the testis, were conducted. In the testes of all the experimental groups, disorders in the organization of the seminiferous epithelium, a lower diameter and area of seminiferous tubules, and a lower percentage of Ki67-positive germinal cells than those in the control group were observed. A lower height of the seminiferous epithelium in the CMP, CMP/S and TMP/S groups than in the control group was noted. A higher percentage of TUNEL-positive germinal cells was detected in the CMP and TMP groups. In the groups with conversion to SRL, a lower diameter and area of seminiferous tubules and height of the seminiferous epithelium (TMP/S vs. TMP) and a lower percentage of Ki67- and TUNEL-positive cells (TMP/S vs. TMP; CMP/S vs. CMP) were revealed. The long-term administration of CNIs in multiple regimens can influence the course of spermatogenesis in the testes of rats, which manifests as morphological alterations in the seminiferous epithelium, vascular accumulation of collagen fibres in interstitial tissue, decreased proliferation of germinal cells and increased nuclear DNA fragmentation related to the apoptotic process. The conversion of treatment with CNIs to SRL also had adverse effects on the seminiferous epithelium; however, it had positive antiapoptotic effects. The obtained results may allow for a better understanding of changes in men undergoing immunosuppressive therapy and a preliminary assessment of which drug combination would be most beneficial in specific clinical cases.