Photobiomodulation of tissue regeneration: low-power light therapy accelerates wound healing in earthworms.

Low-power light therapy also referred to as Photobiomodulation (PBM) has emerged as a promising approach for enhancing tissue repair, yet its molecular mechanisms remain underexplored. This study investigates the effects of green, red, yellow, and white light (2-hour, 6-hour, and 24-hour exposures) on regeneration kinetics and molecular pathways in an earthworm (Eudrilus eugeniae) amputation model. Quantitative analysis revealed that 2-hour red (650 nm) and white (400–700 nm) light exposure significantly accelerated regeneration growth rates compared to other wavelengths and durations. Gene expression profiling through real-time qPCR and western blotting showed distinct pathway activation patterns: TCTP (Translationally Controlled Tumor Protein) and arrestin expression increased 2.3-fold and 1.8-fold respectively in green (525 nm) and red light groups; WNT3a signaling pathway components were upregulated 2.1-fold in white and yellow (590 nm) exposure cohorts. Notably, prolonged 24-hour exposure regimes demonstrated inhibitory effects across all wavelengths, with H2AX DNA repair markers showing elevated activity. These findings establish that brief photostimulation (particularly 2-hour red/white light) optimally activates pro-regenerative pathways through TCTP-mediated cell proliferation and WNT3a-dependent morphogenetic signaling. These results suggest wavelength-specific therapeutic windows for photobiomodulation, providing a mechanistic foundation for developing targeted light-based wound healing strategies in regenerative medicine.