FTIR spectroscopic characterization reveals short-term macromolecular responses to photobiomodulation in mesenchymal stem cells.

Photobiomodulation (low-level laser therapy) was reported to promote tissue repair, stem cell differentiation and proliferation; however, the underlying cellular mechanisms remain unclear. Investigating early, subtle cellular responses may be the key to optimize therapeutic outcomes and understand the biological effects of photobiomodulation. This study aimed to assess short-term macromolecular alterations in adipose-derived mesenchymal stem cells (ADSCs) subjected to 671 nm low-level laser irradiation via Fourier transform infrared (FTIR) spectroscopy. ADSCs were divided into control, 1-hour (1 H post-L) and 3-hour (3 H post-L) post-irradiation groups. 671 nm low-level laser irradiation was applied at a fluency of 25 J/cm(2). After 1 and 3 h, cells were collected and placed on the ATR unit of the FTIR spectrophotometer, dried under mild nitrogen flow and analyzed. Photobiomodulation resulted in explicit differences in FTIR spectra of 1 H and 3 H post-L groups, including alterations in lipid composition, protein secondary structure, protein phosphorylation together with changes in metabolic turnover of carbohydrates over time. Additionally, the membrane order decreased and fluidity increased in the 1 H post-L group, suggesting a temporary lateral phase separation in ADSC membranes. Photobiomodulation induced short-term structural and compositional alterations in biomolecules of ADSCs, which is further remarkable to provide insights into its action mechanism.