A new path in defining light parameters for hair growth: Discovery and modulation of photoreceptors in human hair follicle

The study investigated the expression of light-sensitive receptors, specifically Opsin 2 (Rhodopsin) and Opsin 3 (Panopsin, Encephalopsin), in human hair follicles and examined the effects of UV-free blue light on hair growth. Using RT-qPCR and immunofluorescence, the researchers found that these receptors were present in distinct compartments of the skin and anagen hair follicles. Treatment with 3.2 J/cm² of blue light at a 453 nm wavelength significantly prolonged the anagen phase and sustained proliferation in hair follicles ex vivo, while red light at 689 nm did not have a significant effect. Silencing OPN3 in hair follicle cells altered gene expression related to proliferation and apoptosis, negating the stimulatory effects of blue light. The findings suggested that blue light promotes hair growth potentially through interaction with OPN3.