International Journal of Molecular Sciences · 6 authors, 4 centres
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Multi-wavelength photobiomodulation (PBM) using 680, 780, and 830 nm light safely protected retinal structure and function in a rat model of dry age-related macular degeneration (AMD) induced by sodium iodate. PBM significantly preserved outer nuclear layer thickness, reduced apoptosis, and maintained photoreceptor and retinal pigment epithelium markers. These findings support PBM as a promising non-invasive therapy for dry AMD, for which no cure currently exists.
**Background:** Age-related macular degeneration (AMD) is a leading cause of blindness in older adults, with dry AMD lacking effective treatments. Photobiomodulation (PBM) using low-energy red-to-near-infrared light has shown promise in reducing inflammation and oxidative stress, key drivers of AMD. However, most studies used single wavelengths, and the effects of multi-wavelength PBM on retinal degeneration are poorly understood. This study aimed to evaluate the safety and efficacy of multi-wavelength PBM (680, 780, and 830 nm) in a sodium iodate (NaIO₃)-induced rat model of dry AMD.
**Methods:** In vitro, ARPE-19 retinal pigment epithelial cells were exposed to multi-wavelength PBM at energies of 0, 1.125, 2.25, 4.5, 9.0, and 18 J/cm², and cell viability was assessed via MTT assay at 24, 48, and 72 hours. In vivo, six-week-old male Sprague-Dawley rats were divided into three groups: control (no treatment), dry AMD (35 mg/kg NaIO₃ intravenous injection), and dry AMD+LED (NaIO₃ plus PBM). PBM was delivered daily for 5 days starting 1 day after NaIO₃ injection, using LEDs at 680, 780, and 830 nm with a total energy of 4.5 J/cm² per session. Rats were sacrificed on day 7. Retinal histology (H&E staining) measured total retinal thickness, outer nuclear layer (ONL) thickness, and ganglion cell layer plus nerve fiber layer (GCL+NFL) thickness. Apoptosis was quantified by TUNEL assay. Immunohistochemistry assessed rod bipolar cells (PKCα), photoreceptors (rhodopsin), and RPE cells (RPE65). Statistical analysis used one-way ANOVA with Bonferroni post hoc test.
**Key Results:** In vitro, multi-wavelength PBM showed no cytotoxicity at any energy level up to 18 J/cm², and cell proliferation was unaffected at 24, 48, and 72 hours. In vivo, NaIO₃ significantly reduced total retinal thickness at days 4 and 7 (p < 0.05) and ONL thickness at days 3, 4, and 7 (p < 0.0001) compared to sham. Multi-wavelength PBM significantly preserved ONL thickness (p < 0.001) and GCL+NFL thickness (p < 0.05) compared to NaIO₃ alone. TUNEL-positive cells in the ONL were significantly reduced by PBM (p < 0.001). PKCα-positive rod bipolar cells in the INL were significantly decreased by NaIO₃ (p < 0.0001) and significantly increased by PBM (p < 0.05). Rhodopsin and RPE65 fluorescence intensities were significantly reduced by NaIO₃ (p < 0.0001 and p < 0.01, respectively) and significantly increased by PBM (p < 0.01 and p < 0.05, respectively).
**Clinical Implications:** This study provides preclinical evidence that multi-wavelength PBM is safe and effective in protecting retinal structure and reducing apoptosis in a dry AMD model. The combination of 680, 780, and 830 nm light may target different retinal layers, potentially offering synergistic benefits over single-wavelength approaches. These findings support ongoing clinical trials (e.g., NCT03878420) and suggest PBM as a promising non-invasive therapy for dry AMD, for which no approved treatments exist. Limitations include the use of young rats rather than aged animals and the short 7-day experimental duration, which may not fully replicate chronic AMD. Further studies are needed to elucidate mechanisms and optimize parameters for human translation.