The inner root sheath (IRS) of human hair follicles consists of three concentric cell layers: the cuticle, Huxley's layer, and Henle's layer. All three layers are formed from the peripheral mass of matrix cells in the hair bulb. The formation of the IRS during the evolution of the mammalian epidermis allowed the physiological exit of hairs produced inside the skin. Its dimension and curvature largely determine the shape of the hair. Previous studies have reported the expression of specific type II epithelial keratins and a unique fibroblast growth factor (FGF) in the IRS, suggesting a preferential role for these proteins in hair development. HHIRSC from ScienCell Research Laboratories are isolated from human scalp. HHIRSC are cryopreserved at passage one and delivered frozen. Each vial contains >5 x 105 cells in 1 ml volume. HHIRSC are characterized by their mesenchymal cell morphology and immunofluorescence with antibodies specific to fibronectin and/or CD105. HHIRSC are negative for HIV-1, HBV, HCV, mycoplasma, bacteria, yeast, and fungi. HHIRSC are guaranteed to further expand for 10 population doublings under the conditions provided by ScienCell Research Laboratories. Recommended Medium It is recommended to use Mesenchymal Cell Medium (MCM, Cat. #7501) for culturing HHIRSC in vitro.