Lipid analysis of human primary dermal fibroblasts and epidermal keratinocytes after near-infrared exposure using mass spectrometry imaging.

Photobiomodulation (PBM) therapy is the application of near-infrared (NIR) exposure to injuries or lesions to (among others) improve wound healing, reduce inflammation, and decreases acute and chronic pain. However, the understanding of the molecular mechanism of PBM, more specifically the effects of NIR on skin cells is still lacking behind. Lipids are essential components of cellular membranes that are integral to skin structure and function. This study aims to elucidate the impact of NIR exposure on the skin's lipidome by investigating the molecular effect of NIR exposure on single skin cells. Primary human dermal fibroblasts (NHDFa) and human epidermal keratinocytes (HEKa) were exposed to NIR (850 nm) with a dose of 6.5 J/cm for 5 consecutive days between 09.00 and 12.00 am. A workflow utilizing matrix-assisted laser desorption/ionization mass spectrometry imaging combined with liquid chromatography tandem mass spectrometry for lipidomics analysis was performed. This study provides evidence that adequate exposure of NIR influences lipid metabolism in NHDFa, whereas no alterations were found in HEKa. This work lays the groundwork in explaining the beneficial properties on both skin-related effects and systemic health benefits as seen in clinical studies.