Dermal papilla cell‐secreted biglycan regulates hair follicle phase transit and regeneration by activating Wnt/β‐catenin

Abstract Alopecia is a prevalent problem of cutaneous appendages and lacks effective therapy. Recently, researchers have been focusing on mesenchymal components of the hair follicle, i.e. dermal papilla cells, and we previously identified biglycan secreted by dermal papilla cells as the key factor responsible for hair follicle‐inducing ability. In this research, we hypothesized biglycan played an important role in hair follicle cycle and regeneration through regulating the Wnt signalling pathway. To characterize the hair follicle cycle and the expression pattern of biglycan, we observed hair follicle morphology in C57BL/6 mice on Days 0, 3, 5, 12 and 18 post‐depilation and found that biglycan is highly expressed at both mRNA and protein levels throughout anagen in HFs. To explore the role of biglycan during the phase transit process and regeneration, local injections were administered in C57BL/6 and nude mice. Results showed that local injection of biglycan in anagen HFs delayed catagen progression and involve activating the Wnt/β‐catenin signalling pathway. Furthermore, local injection of biglycan induced HF regeneration and up‐regulated expression of key Wnt factors in nude mice. In addition, cell analyses exhibited biglycan knockdown inactivated the Wnt signalling pathway in early‐passage dermal papilla cell, whereas biglycan overexpression or incubation activated the Wnt signalling pathway in late‐passage dermal papilla cells. These results indicate that biglycan plays a critical role in regulating HF cycle transit and regeneration in a paracrine and autocrine fashion by activating the Wnt/β‐catenin signalling pathway and could be a potential treatment target for hair loss diseases.