Photobiomodulation-induced Differentiation of Adipose-derived Stem Cells into Neuronal Organoid-like Structures

The ability to regulate stem cell differentiation into organized neural tissue remains a major challenge in regenerative medicine, particularly in the development of physiologically relevant three-dimensional (3D) organoid models. Photobiomodulation (PBM) is a new non-invasive technology for controlling cellular metabolism and differentiation using light-mediated signalling pathways; however, its role in neural organoid development remains insufficiently understood. This study investigated the effects of PBM on the differentiation of adipose-derived mesenchymal stem cells (ADMSCs) into neuronal organoid-like structures using a 3D culture system. Immortalized ADMSCs were exposed to 525 nm and 825 nm wavelengths, individually and in combination, at fluences of 5 and 10 J/cm². PBM's effects were assessed using morphological assessment, cell viability, ATP-based metabolic activity, mitochondrial membrane potential (ΔΨm), and neural gene expression. PBM treatment affected organoid morphology, metabolic activity, and mitochondrial function in a dose- and wavelength-dependent way. Low-fluence irradiation (5 J/cm²), especially at 525 nm, promotes stem cell maintenance and early neural development, as evidenced by enhanced expression of progenitor and neuronal markers. Higher fluence (10 J/cm²) inhibited early differentiation responses, but mixed wavelength therapy promoted late-stage neuronal maturation with increased RBFOX3 gene expression. These findings indicate PBM as a viable method for controlling stem cell destiny and improving neuronal organoid formation for neuroregenerative applications.