Wavelength-Dependent Modulation of Mesenchymal Stem Cell Fate: A Systems Biology Framework for Tissue Repair and...

Mesenchymal stem cells (MSCs) are central effectors in regenerative medicine, yet their clinical translation is hindered by inconsistent therapeutic outcomes and a lack of standardized light-delivery protocols. This review addresses an underexplored dimension of photobiomodulation (PBM): the divergent, wavelength-dependent signaling programs triggered in MSCs by red/near-infrared (NIR) versus blue light. By integrating biophysical principles of light delivery with a systems biology analysis of protein-protein interaction networks (STRING/GO), we delineate a "Dual Photonic Programming" framework. Red/NIR light (600-1100 nm) targets mitochondrial cytochrome c oxidase, activating a bioenergetic-anabolic program centered on PI3K/Akt/mTOR and Wnt/β-catenin-pathways essential for structural tissue repair. Blue light (400-500 nm) engages cytosolic flavins to drive a secretory-paracrine program that modulates vesicle trafficking and immunomodulatory cargo release. We further examine the dosimetric paradox, demonstrating how culture-environment optics and the Arndt-Schultz biphasic law govern the transition from regenerative stimulation to inhibitory oxidative stress. By tailoring photonic parameters to the MSC's anatomical origin and metabolic baseline, PBM can serve as a high-fidelity bio-switch for orchestrated tissue repair, providing a mechanistic roadmap for standardized regenerative therapies.