Figure 2.

Dynamic remodeling and morphology of the dermal sheath during the hair cycle. During the growth phase (anagen), expanding DS tightly wraps the follicle and is closely juxtaposed with the epithelial ORS progenitors, with the proximal bulbar DS cells referred to as the DS cup. During the regression phase (catagen), the DS more loosely encases the epithelial strand around which restructuring of the basement membrane occurs (referred to as “glassy”). Apoptotic DS cells trail the regressing follicle in the DS “sleeve,” and by the resting phase (telogen) only a few DS cells persist and intimately surround the DP, which are bipotent stem cells termed hair follicle dermal stem cells (hfDSCs). DS = dermal sheath; DP = dermal papilla; Mx = matrix; ORS = outer root sheath progenitors; BM = basement membrane.