Photobiomodulation-Induced Differentiation of Immortalized Adipose Stem Cells to Neuronal Cells

Background and Objectives: Transdermal differentiation of human adipose stem cells (ASCs) to other cell types is still a challenge in regenerative medicine. Studies using primary ASCs are also limited as they may undergo replicative senescence during repeated passages in vitro. However, ASCs immortalized (iASCs) with human telomerase enzyme expressing plasmid exhibits a uniform population suitable for differentiation in vitro. A right combination of biological and physical stimuli may induce transdermal differentiation of iASCs into neurons in vitro. Study Design/Materials and Methods: iASCs were differentiated to free-floating neural stem cell aggregates (neurospheres) using a combination of growth inducers. Cells in these spheres were induced to differentiate into neurons using low-intensity lasers by a process called photobiomodulation (PBM). Results: Laser at the near infrared (NIR) wavelength 825 nm and fluences 5, 10, and 15 J/cm² was capable of increasing the differentiation of neurospheres to neurons. Precisely, there was a statistically significant increase in the early neuronal marker at 5 J/cm² and a much appreciable increase at 15 J/cm² in correlation with the biphasic dose response of PBM. However, these differentiated cells failed to express late neuronal markers in vitro. Comparison of these differentiating iASCs with the primary ASCs revealed a sharp distinction between the metabolic processes of the primary ASCs, neurospheres, and newly differentiated neurons. Conclusion: We found that PBM increased the yield of neurons and effected stem cell differentiation through modulation of cellular metabolism and redox status. Our study also identifies that iASCs are an excellent model for analysis of stem cell biology and for performing transdermal differentiation. Significance: This study demonstrates that a combination of biological and physical inducers can advance the differentiation of adipose stem cells to neurons. We were able to establish the optimal energy for the neuronal differentiation of iASCs in vitro. Lasers Surg. Med.