Objective: To investigate the expression rules of FOXO1a, FOXO3a, FOXO4 and FOXO6 proteins in the human testis, and explore their roles in the development and progression of testicular aging.
Methods: We collected the para-carcinoma testis tissue from 4 testis cancer patients aged 28, 31, 32 and 46 years, and the testis tissue from another 2 PCa patients aged 66 and 81 years after castration surgery from January 2018 to December 2020. We detected the expressions of FOXO1a, FOXO3a, FOXO4 and FOXO6 proteins in the testis tissue by Western blot, determined the locations of FOXO1a, FOXO3a, FOXO4 and FOXO6 in the testis cells by immunofluorescence staining, and performed semi-quantitative and statistical analyses using image J and SPSS 23.0 software, respectively.
Results: The expression levels of FOXO1a and FOXO3a proteins were significantly decreased in the testis tissue of the elderly patients (P < 0.01), with an age-dependent reduction in the proportion of the positive cells. No statistically significant difference was observed in the expression levels of FOXO4 and FOXO6 between different age groups. FOXO1a was mainly expressed at the base of the seminiferous tubules, FOXO3a and FOXO4 in the Leydig cells, and FOXO6 in the seminiferous tubules. In addition, FOXO4 underwent age-related nuclear translocation in the senescent Leydig cells, suggesting its involvement in the aging of Leydig cells.
Conclusion: FOXO1a/3a/4 may be closely related to human testicular aging and corresponding pathological changes, but its underlying mechanism remains to be further explored.
Keywords: forkhead box O family; testicular aging; Leydig cell; spermatogenic cells.