Sertoli cell number is altered in dogs with immune-mediated orchitis

The most common diagnosis in infertile male dogs is acquired non- obstructive azoospermia (NOA). NOA is not only associated with severe histological and inflammatory changes but also with a sig-nificant impairment of spermatogenesis and immune cell infiltration, indicating orchitis. Due to the lack of clinical signs and unknown, but chronic aetiology, it is defined as chronic immune-mediated orchitis (IMO). Despite the presence of some spermatogonial stem cells, spermatogenesis is irreversibly affected indicating an impor-tant role for Sertoli cells (SC) in this process. SC number determines the fate of spermatogenesis. Therefore, Sertoli cell number was counted in 20 approximately round seminiferous tubules in testis samples obtained from IMO-affected dogs (n = 12), healthy adult control dogs with histologically normal spermatogenesis and nor-mospermia (n = 10) and healthy juvenile dogs (2–3 months; n = 3). Vimentin-stained slides were used for the evaluation of Sertoli cells at 400-fold magnification. Numbers were statistically compared by one-way ANOVA followed by pairwise comparison by t-test. SC number differed significantly between groups (p < .0001) with signif-icantly fewer SCs in AIO compared to CG and JG (each p < .001). SC numbers in CG and JG did not differ, however. Our results indicate that SC survive in the damaged testis, but the SC number is reduced. This might play an important role in treating AIO aiming for restora-tion of spermatogenesis. Further studies should focus on evaluating the differences in SC function to get gain further insights that might be suitable for (re-)initializing spermatogenesis.