title: Drug discovery for alopecia: gone today, hair tomorrow.
abstract: BACKGROUND
  Hair loss or alopecia affects the majority of the population at some time in their life, and increasingly, sufferers are demanding treatment. Three main types of alopecia (androgenic [AGA], areata [AA] and chemotherapy-induced [CIA]) are very different, and have their own laboratory models and separate drug-discovery efforts.
  
  
  METHODS
  In this article, the authors review the biology of hair, hair follicle (HF) cycling, stem cells and signaling pathways. AGA, due to dihydrotesterone, is treated by 5-α reductase inhibitors, androgen receptor blockers and ATP-sensitive potassium channel-openers. AA, which involves attack by CD8(+)NK group 2D-positive (NKG2D(+)) T cells, is treated with immunosuppressives, biologics and JAK inhibitors. Meanwhile, CIA is treated by apoptosis inhibitors, cytokines and topical immunotherapy.
  
  
  CONCLUSIONS
  The desire to treat alopecia with an easy topical preparation is expected to grow with time, particularly with an increasing aging population. The discovery of epidermal stem cells in the HF has given new life to the search for a cure for baldness. Drug discovery efforts are being increasingly centered on these stem cells, boosting the hair cycle and reversing miniaturization of HF. Better understanding of the molecular mechanisms underlying the immune attack in AA will yield new drugs. New discoveries in HF neogenesis and low-level light therapy will undoubtedly have a role to play.
authors: Massachusetts General Hospital, Wellman Center for Photomedicine , Boston, MA 02114 , USA +1 617 726 6182 ; +1 617 726 6643 ; hamblin@helix.mgh.harvard.edu.
authors: Zenildo
authors: Z
authors: Santos
authors: Pinar
authors: P
authors: Avci
authors: Michael R
authors: MR
authors: Hamblin
mesh_terms: D000287:Administration, Topical; D000505:Alopecia / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D000818:Animals; D055808:Drug Discovery / Q000379:methods*; D006197:Hair / Q000187:drug effects* / Q000254:growth & development; D018859:Hair Follicle / Q000378:metabolism; D006801:Humans; D007167:Immunotherapy / Q000379:methods; D004364:Pharmaceutical Preparations / Q000008:administration & dosage; D013234:Stem Cells / Q000166:cytology
chemical_list: D004364:Pharmaceutical Preparations
keywords: 5-α-reductase inhibitor; alopecia areata; androgenic alopecia; anti-androgen; baldness; chemotherapy-induced alopecia; hair follicle; low-level laser (light) therapy; stem cells; topical immunotherapy