OBJECTIVETo investigate the effect of substance P (SP) on the migration and differentiation of epidermal stem cells (ESCs) to hair follicle, and its mechanism.

METHODSESCs were cultured in vitro, and confirmed by positive staining of K19 and integrin beta1 with immunohistochemistry. SP was added into the culture of ESCs which were labelled with 5-BrdU, and the cell cultures were divided into control, 10(-5) mol/L SP, 10(-6) mol/L SP, and 10(-7) mol/L SP groups according to the different doses of SP addition. Cell suspension (0.3 ml) containing SP was injected into the dermis in the back of nude mice. Repeated injection of the equal amount of cell suspension in the same place was carried out on 4, 7, 10 and 14 days after first injection. The cells in control group received the same treatment but without SP. The skin specimens in the area of cell culture injection and the normal skin remote from cell injection were harvested for the histological examination and hair follicle counting by immunohistochemistry and electronmicroscope 28 days after injections.

RESULTSHair follicles in scattered distribution were observed in 10(-5) mol/L SP group,but some of them were defective in development. Hypoplasic hair follicle and a few hair follicles with distinct structure were observed in 10(-5) mol/L SP group. Large amounts of hair follicles with distinct structure in deep dermis and subcutaneous tissue were observed in 10(-6) mol/L SP, 10(-7) mol/L SP groups, and some of them showed positive staining of brown BrdU in the hair root, and most of them showed positive staining of brown beta-catenin, but a few of them showed developmental defect. In contrast, hypoplasia of hair follicle underneath epidermis and deep layer of dermis with positive staining of brown BrdU and beta-catenin in epidermis were observed in control group. The number of hair follicles in 10(-6)mol/L SP, 10(-7) mol/L SP groups [(1.9 +/- 1.2 ), (1.3 +/- 0.8)] was obviously less than that in control group [(10. 5 +/- 1.2), P < 0.01].

CONCLUSIONSP can induce ESCs to migrate from the basal layer into hair follicle, and this effect is dependent on the SP concentration. SP can also elevate the expression of beta-catenin in ESCs,which induces its differentiation to hair follicles.