Potential therapeutic effects of red led light on testicular histology and sperm parameters in aged and adult rats

Introduction and Aim: The testes are among the most essential organs of the male reproductive system, responsible for sperm production and the synthesis of male sex hormones. Aging is associated with thinning of the seminiferous epithelium, decreased tubular diameter, reduced testosterone levels, and significant deterioration in sperm parameters. Although non-invasive photobiomodulation-based applications have recently been shown to exert regulatory and regenerative effects on various tissues, the number of studies comparatively evaluating the effects of red LED light on testicular structure and sperm quality across different age groups remains limited. This study aimed to investigate the potential regulatory effects of red LED light on testicular histology and sperm parameters in adult and aged rats. Materials and Methods: Following approval from the Çukurova University Local Ethics Committee for Animal Experiments (24.04.2025/decision no: 1), 24 male Wistar–Albino rats were used. The study consisted of four groups, each containing six rats classified by age and body weight: adult control (G1), adult LED (G2), aged control (G3), and aged LED (G4). All rats were housed under standard laboratory conditions with a 12-hour light–12-hour dark cycle for 30 days. In LED groups, red LED light (2835 SMD Strip LED; 4.8 W/620–750 nm/155 lm) was placed 20 cm above the cages and applied daily according to a fixed protocol. Testis tissue samples collected at the end of the experiment were evaluated histomorphometrically and immunohistochemically, while biochemical parameters were measured from blood samples. Statistical analyses were performed using SPSS 20.0 software, with p<0.05 considered significant. Results: No significant differences were found among the groups in terms of the biochemical parameters SOD (p=0.272), GPX1 (p=0.001), melatonin (p=0.102) and LH (p=0.267). Significant differences were observed between the G1–G2 and G3–G4 groups with respect to testosterone (p<0.001) and MDA (p<0.001) levels. Histological evaluations revealed significant differences among the groups in terms of seminiferous tubule epithelial thickness (p<0.001), sperm count (p<0.001), and sperm motility (p<0.001). In particular, the positive findings observed in the G4 group were found to be statistically significant compared with the G3 group. Immunohistochemical analysis of PCNA, BMAL1, and 3β-HSD immunoreactivity also demonstrated significant differences in the G4 group compared with the G3 group (p<0.05). Although a numerically positive increase was detected in the G2 group, no statistically significant difference was found.Conclusion: This study demonstrates that red LED light may exert beneficial effects on testicular structure and sperm parameters. The findings, particularly in aged rats, suggest that red LED therapy could represent a potential non-invasive approach to mitigating age-related testicular degeneration. However, studies with larger sample sizes and more extensive molecular analyses are needed to elucidate the underlying mechanisms in detail. Keywords: Red LED light, Photobiomodulation, Testicular histology, Sperm parameters, Aging, Rat