Effects of optogenetic stimulation on neural gene expression in human bone marrow and adipose-derived mesenchymal stem cells

Bone Marrow-derived Mesenchymal Stem Cells (BM-MSCs) and adipose tissue are widely applied in tissue engineering. Optogenetics enables millisecond-scale spatial and temporal control of particular cell populations. In this technology, genetically-modified cells, that express light-sensitive opsins, are stimulated or inhibited by light. Since an increase in intracellular cation flow is one of the causal factors of stem cell differentiation, the purpose of this study was to investigate the alterations in the expression levels of crucial neural biomarkers in BM-MSCs and Adipose-MSCs (A-MSCs) in terms of channelrhodopsin-2 (ChR2) expression and non-expression, low-power blue light radiation, or a combination of both treatments. A plasmid vector encoding the ChR2 (H134R) opsin protein gene, which belongs to the group of opsins activated by blue light, fused with the EYFP fluorescent protein gene, was employed in this study. After adding the plasmid vector to both BM-MSCs and A-MSCs, the surface expression of the EYFP fluorescent protein underneath a fluorescent microscope was examined. The conditioned cells were exposed to low-power blue light (470 nm wavelength, variable pulse width, 1 Hz frequency, and 1 mW power for 1-hour irradiation). The results indicated that integrating the plasmid vector into BM-MSCs and A-MSCs, along with expressing ChR2 and applying blue light irradiation, significantly increased the expression of selected neural genes. Also, Nestin expression continued to increase in both cell lineages. In addition, each therapy (ChR2 expression and light stimulation) or the combination of both did not have any significant cytotoxic effects on the cells. Our results demonstrate that the expression of neural biomarkers in BM-MSCs and A-MSCs can be increased by in vitro optogenetic stimulation of ChR2-MSCs.