Aplicação de células tronco mesenquimais alogênicas em parênquima testicular equino - características histopatológicas

Abstract

The promising therapeutic effect of allogeneic mesenchymal stem cells (MSCs) has been observed in several fields of veterinary medicine, including reproductive medicine. This effect is attributed to their ability to produce cytokines, growth factors, and other chemokines, which exert paracrine effects on tissues, playing an important role in immunomodulation and thus contributing to the recovery and regeneration of other cell and tissue types in the organism. Consequently, MSCs represent a potential therapeutic approach for testicular pathologies in stallions. The present study aimed to evaluate the effect and safety of allogeneic adipose tissue-derived MSC application into the testicular parenchyma of young stallions. A total of nine young animals, aged between 3 and 7 years and of different breeds, located in the region of Uberlândia, Minas Gerais (Brazil), were used. The animals were allocated into three experimental groups: treated (intratesticular application of 3 × 10⁶ MSCs), control (no application), and sham (intratesticular application of 3 mL Dulbecco’s Phosphate-Buffered Saline – DPBS, the same dilution vehicle used for MSCs). Between 20 and 40 days post-application, the animals underwent orchiectomy. Transverse cuts, 0.5 cm thick and not completely sectioned, were made with a scalpel in the testes, which were then fixed in 10% buffered formalin, transferred to 70% ethanol, and subsequently embedded in paraffin. For histopathological evaluation, tissue blocks were sectioned at 5 μm using a microtome, mounted on slides, and stained with hematoxylin and eosin. Each slide was divided into four quadrants, within which seminiferous tubule diameter (in micrometers), seminiferous tubule area, seminiferous epithelium height, and the number of blood vessels were measured. For statistical analysis, data were initially tested for normality assumptions (Shapiro–Wilk test) and homogeneity of variances (Bartlett’s test). Variables that did not meet these assumptions, even after transformation, were analyzed using the non-parametric Kruskal–Wallis test, with interpretation based on medians. Variables that met the assumptions were analyzed using analysis of variance (ANOVA). For seminiferous tubule area, a significant difference was observed between groups (p < 0.001), with the control group showing the highest median value (0.126), followed by MSC (0.101) and DPBS (0.099), with all groups being statistically distinct. For epithelial height, a significant difference was also detected (p < 0.001), with the MSC group (0.009) being superior to both control (0.008) and DPBS (0.007) groups, which did not differ from each other. The number of blood vessels did not differ significantly among groups (p = 0.920). As no animal exhibited adverse reactions, it can be concluded that intratesticular application of MSCs in stallions is safe. The data further suggest that MSC treatment may be associated with accelerated testicular maturation, as evidenced by the significant increase in epithelial height, which may indicate the regenerative and immunomodulatory potential of mesenchymal stem cells in reproductive therapies for the equine species. Further studies, however, are required to confirm these findings.