Abstract : The insulin-like growth factor-1 (IGF-1) is a key regulator of reproductive functions. IGF-1 actions are primarily mediated by IGF-1 receptor (IGF-1R). The main objective of this research was to evaluate the presence of IGF-IR in broiler testicular tissue in different ages (9, 18, 36, and 72 weeks as pubertal, post-pubertal, adult and aged chickens, respectively) using immunohistochemistry and its association with mir-202-5p, reproductive hormones, and oxidative stress. Testicular tissues were collected from ten broilers per age group (n=10/group), yielding a total of forty animals (N=40). A positive response to IGF-1R was ob-served in both intratubular germ cells and Leydig cells in different aged birds through immunofluorescence evaluation. The findings demonstrated an age-related variation in the distribution of IGF-1R throughout the testes. The immunofluorescence labelling of IGF-1R decreases as animal age through different stages in an age-dependent manner. Spermatocytes of all ages showed faint labeling. The IGF-1R levels correlate nega-tively with malondialdehyde and miR-202-5p, and positively with luteinizing Hormone (LH), follicle-stimulating hormone (FSH), testosterone, and total antioxidant capacity levels, particularly at 9, 18, and 36 weeks of age. The localization of IGF-1R in chicken spermatogenic cells and interstitial areas of the testes suggests that it is implicated in chicken spermatogenesis and Leydig cell function at various stages of de-velopment. In conclusion, these findings demonstrate that the age-associated decline in testicular IGF-1R is closely linked to an increased in miR-202-5p and oxidative stress, and a reduction in key reproductive hor-mones, suggesting its central role in age-related testicular decline in broilers.
