Anti-Müllerian hormone in feline cryptorchidism: Serum levels, tissue expression, and implications for testicular health

Anti-Müllerian hormone (AMH) has become a pivotal subject in the study of testicular descent, maturation, integrity, and male fertility. Recent studies explored its roles and implications across various domestic species. A prominent approach involved the understanding of the modulation of AMH in reproductive disorders, including cryptorchidism. While substantial findings have been reported in dogs, ruminants, swine, and horses, data on AMH in feline cryptorchidism remains limited. Here, we aimed to bridge this gap by comparing AMH serum levels among cryptorchid, healthy intact, and castrated tomcats, employing an enzyme-linked immunosorbent assay (ELISA) kit for quantification. In addition, AMH expression in retained and descended testes was evaluated through immunohistochemistry, with positive staining quantified via pixel analysis in two distinct regions of interest: the seminiferous tubule and the interstitial space. Furthermore, tissue samples were subjected to histological evaluation and morphometric analysis, which included the calculation of seminiferous tubule areas (STA) and assessment of Johnsen scores. Thus, the relationship between AMH expression, altered testicular histology, and impaired spermatogenesis could be examined. The expression of AMH in retained and descended testes, was investigated, and the relationship between AMH expression, altered testicular histology, and impaired spermatogenesis was examined. Mean serum AMH levels differed significantly (P < 0.001) across the different groups being 15.35 ± 4.66 ng/mL (mean ± SD) in healthy intact tomcats (n = 15), 25.55 ± 2.86 ng/mL (mean ± SD) in cryptorchids (n = 10) and below 0.015 ng/mL in castrated cats (n = 10). STAs and Johnsen scores were significantly reduced in retained testes when compared to descended gonads (P < 0.01). Furthermore, serum AMH was negatively correlated with both the STA (ρ = -0.725, P < 0.001) and the Johnsen scores (ρ = -0.699, P < 0.001), suggesting its potential value for tissue integrity and spermatogenesis evaluation. In addition, positive immunostaining was significantly higher in retained testes (P < 0.05), especially in the interstitial space (P < 0.01), suggesting an involvement of the Leydig cells. Additionally, the increased interstitial expression was linked to the degree of tissue degeneration and the impaired spermatogenesis being negatively corelated with both Johnsen scores (ρ = -0.309, P < 0.01) and STA (ρ = -0.208, P < 0.05). Our findings underscore the potential of AMH in assessing testicular health and reveal possible interspecific differences, stressing the need for further investigation in cats.