The implication of blue light-emitting diode on mesenchymal stem cells: a systematic review

The application of blue light (400-480 nm) in photobiotherapy remains controversial. This systematic review aimed to collect and analyze the biological effects of blue light-emitting diode (LED) on mesenchymal stem cells (MSCs). Inclusion and exclusion criteria were formulated, and relevant English articles from January 1982 to September 2022 were searched in PubMed, Scopus, and Web of Science. Nine articles with a medium (n = 4) to low (n = 5) risk of bias were included. Most of the MSCs reported were derived from human tissue; only one article used MSCs derived from mouse. The wavelength of the LED used was in the 400-480 nm range, and the irradiation modes were continuous (n = 8) and pulse waves (n = 1). A chiral polarizer was used in one such study in which the irradiance was 14 mW/cm² and the irradiation time was 24 h. The energy densities used in other studies were between 0.378 and 72 J/cm², and the irradiation times were between 10 and 3600 s. Blue LED light can inhibit proliferation and promote differentiation of MSCs in an appropriate energy density range, which may be related to the activation of transient receptor potential vanilloid 1 (TRPV1). Additionally, polarized light may reduce the toxic effects of blue light on MSCs. However, the heterogeneity of the design schemes and LED parameters, as well as the small number of studies, limited the conclusiveness of the review. Therefore, further studies are needed to determine the optimal irradiation strategy for promoting MSC function.