Thiopurines exert harmful effects on spermatogenesis in Nudt15^R138C knock-in mice

The association between thiopurine use and testicular reproductive functions remains unclear. In this study, we investigated whether thiopurines affect testicular functions based on the NUDT15 genotypes using Nudt15^R138C knock-in mice.

The male Nudt15^R138C knock-in mice (9-12 weeks) were treated with mercaptopurine (MP: 0.5 mg/kg/day) for 4 or 12 weeks. To examine reversibility, some mice were maintained for a further 12 weeks under MP-free condition.

After MP treatment for 4 weeks, Nudt15^R138C/R138C mice exhibited a significant reduction of testis weight compared to Nudt15^+/+ mice and Nudt15^+/R138C mice. The epithelial height and diameter of seminiferous tubules were significantly reduced in Nudt15^R138C/R138C mice compared to Nudt15^+/+ and Nudt15^+/R138C mice. Apoptotic cells were significantly increased in Nudt15^R138C/R138C mice, and most of apoptotic cells were spermatogonia. There were no significant changes in sperm counts and sperm morphology in MP-treated Nudt15^R138C/R138C mice after 4-week MP treatment. On the other hand, after MP treatment for 12 weeks, the Nudt15^+/R138C mice, but not Nudt15^+/+ mice, exhibited a significant reduction in the testis weight and atrophic changes of seminiferous tubules, but these changes disappeared after 12-week rearing under MP-free condition. Despite a significant increase in abnormal sperm rate, there were no changes in the ability to conceive. No differences in serum levels of follicle-stimulating hormone or testosterone were observed between MP-treated Nudt15^+/R138C and Nudt15^+/+ mice after 12-week MP treatment.

Thiopurines exert harmful effects on testicular reproductive function according to host NUDT15 genotypes.