Low-energy helium–neon laser induces melanocyte proliferation via interaction with type IV collagen: visible light as a therapeutic option for vitiligo

Background The treatment of vitiligo remains a challenge for clinical dermatologists. We have previously shown that the helium–neon laser (He–Ne laser, 632·8 nm) is a therapeutic option for treatment of this depigmentary disorder. Objectives Addressing the intricate interactions between melanocytes, the most important cellular component in the repigmentation scheme of vitiligo, and their innate extracellular matrix collagen type IV, the current study aimed to elucidate the effects of the He–Ne laser on melanocytes. Methods Cultured melanocytes were irradiated with the He–Ne laser. Relevant biological parameters including cell attachment, locomotion and growth were evaluated. In addition, the potentially involved molecular pathways were also determined. Results Our results show that in addition to suppressing mobility but increasing attachment to type IV collagen, the He–Ne laser stimulates melanocyte proliferation through enhanced α2β1 integrin expression. The expression of phosphorylated cyclic‐AMP response element binding protein (CREB), an important regulator of melanocyte growth, was also upregulated by He–Ne laser treatment. Using a specific mitochondrial uncoupling agent [carbonyl cyanide m‐chlorophenyl‐hydrazone (CCCP)], the proliferative effect of the He–Ne laser on melanocytes was abolished and suppression of melanocyte growth was noted. Conclusions In summary, we have demonstrated that the He–Ne laser imparts a growth stimulatory effect on functional melanocytes via mitochondria‐related pathways and proposed that other minor pathways including DNA damage may also be inflicted by laser treatment on irradiated cells. More importantly, we have completed the repigmentation scheme of vitiligo brought about by He–Ne laser light in vitro and provided a solid theoretical basis regarding how the He–Ne laser induces recovery of vitiligo in vivo.