18.97.9.171
18.97.9.171
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Regulation of hair growth and cycles: dermal papilla approach
강훈 ( Hoon Kang )
UCI I410-ECN-0102-2017-510-000524676
This article is 4 pages or less.

The dermal papilla (DP) cells of the hair follicle are permanent repository for epithelial progenitor cells that regenerate the hair follicle and generate the hair shaft. In this session, I will review experiments that revealed the importance of the DP cells (DPCs) in regulating the hair follicle regeneration and the hair growth cycles. I. DPCs in hair morphogenesis · Epidermal placode recruits cells from the underlying dermis · Dermal condensate: a local increase in dermal cell density beneath the epidermal placode · Active signaling between dermal condensate and placode stabilizes both populations and drives further development of the hair peg · Dermal condensate becomes the DP as it further compacts and is engulfed by the growing hair peg · DP act as the progenitor population that produces the inner root sheath (IRS) and hair shaft · At the end of the growth phase, the progenitor population adjacent the DPCs either differentiate or die · The hair shaft and IRS are drawn upward to the permanent portion of the follicle · Secondary germ: compact ball shaped DPCs which located at the base of resting follicle · Start of a new anagen phase: DPCs becomes less compact and the subsequent regeneration of the lower follicle is quite similar to initial morphogenesis · Throughout the hair cycle, the DP is well positioned to provide inductive signals that guide the activity of the cells that generate and regenerate the follicle · DPCs serve as the physical niche for progenitor cells II. DPCs as a regulator of hair growth environment · DPCs are dynamic regulator of hair follicle · Various types of gene expression of DPCs indicate that DPCs are source of diffusible signals that influence follicular epithelium · Implantation of DP was sufficient to restore regeneration · The role of the mesenchyme in directing morphology of the hair produced is maintained in the mature DPCs III. Anagen initiation · DPCs send signals to the stem cells of the follicular bulge to initiate a new anagen phase · Activation of the keratinocytes adjacent the DPCs is the first step of anagen initiation · DPCs expresse Wnts, FGFs, Noggin and R-spondins all of which can promote follicle growth and contribute to initiating follicular regeneration · Regeneration of the follicle accompany initial activation of signaling between mesenchyme and epithelium · β-catenin gene in DPCs is essential for the initiation of anagen -β-catenin gene lacking in the DP enter the telogen phase, fail to reenter anagen · Reduced cell number of DP induce delayed anagen initiation · Importance of macroenvironmental factor - signals from adjacent follicles - signals from other cell types in the skin - hormonal signals generated outside the skin IV. Maintenance of DP size · DPCs population in a follicle is not fixed - decrease number during telogen phase, but restore at anagen · Healthy and normal-sized epithelial compartment can either recruit new cells or sustain the proliferation of existing DPCs to regenerate its niche · The source of additional DPCs during regeneration after damage has not been characterized

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