Photobiomodulation of Human Embryonic Stem Cell-Derived Mesenchymal Stem Cells by 355 nm Low-Level Ultraviolet Laser Exposure

Purpose: The aim of the present investigation was to observe the effects of different energy densities of ultraviolet A photobiomodulation (UVA PBM) on human embryonic stem cell-derived mesenchymal stem cells (hESC-MSCs). Methods: The hESC-MSCs were cultured and irradiated with UVA PBM at energy densities ranging from 0.5 to 5.0 J/cm 2 at a wavelength of 355 nm. Key biological parameters, including proliferation, viability, and migration, were evaluated at 72 h postirradiation. Results: Compared with the control, the UVA PBM significantly increased cell proliferation and viability at energy densities ranging from 0.5 to 2.0 J/cm 2 and 0.5 to 3.0 J/cm 2 , respectively. Further, UVA PBM notably increased the migratory capacity of hESC-MSCs within the 0.5–2.0 J/cm 2 range. Interestingly, higher energy densities beyond this threshold were found to be ineffective in promoting these cellular responses. In addition to examining proliferation, viability, and migration, this study explored the role of UVA PBM in osteogenic differentiation. Following irradiation, hESC-MSCs were induced toward osteogenesis, and differentiation was assessed through Alizarin Red S staining to evaluate calcium deposition. The results indicated that UVA PBM at optimal low-energy densities not only enhanced early proliferation but also supported osteogenic potential, as evidenced by increased mineralization in treated cells. To further understand the molecular mechanisms underlying these effects, quantitative PCR (qPCR) was performed to analyze the expression of key osteogenic markers, including RUNX2, Alkaline phosphatase, and Osteocalcin (OCN). Gene expression analysis revealed significant upregulation of these markers in the UVA PBM-treated groups, suggesting that UVA PBM promotes osteogenesis at the transcriptional level. UVA PBM at low energy densities significantly enhances the proliferation, viability, migration, and osteogenic differentiation of hESC-MSCs, potentially through the modulation of osteogenic gene expression. Conclusion: These findings highlight the therapeutic potential of UVA PBM in regenerative medicine and bone tissue engineering, particularly dentistry.