title: A two-step mechanism for stem cell activation during hair regeneration.
abstract: Hair follicles (HFs) undergo cyclic bouts of degeneration, rest, and regeneration. During rest (telogen), the hair germ (HG) appears as a small cell cluster between the slow-cycling bulge and dermal papilla (DP). Here we show that HG cells are derived from bulge stem cells (SCs) but become responsive quicker to DP-promoting signals. In vitro, HG cells also proliferate sooner but display shorter-lived potential than bulge cells. Molecularly, they more closely resemble activated bulge rather than transit-amplifying (matrix) cells. Transcriptional profiling reveals precocious activity of both HG and DP in late telogen, accompanied by Wnt signaling in HG and elevated FGFs and BMP inhibitors in DP. FGFs and BMP inhibitors participate with Wnts in exerting selective and potent stimuli to the HG both in vivo and in vitro. Our findings suggest a model where HG cells fuel initial steps in hair regeneration, while the bulge is the engine maintaining the process.
authors.affiliation: Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10065, USA.
authors.forename: Valentina
authors.initials: V
authors.lastname: Greco
authors.forename: Ting
authors.initials: T
authors.lastname: Chen
authors.forename: Michael
authors.initials: M
authors.lastname: Rendl
authors.forename: Markus
authors.initials: M
authors.lastname: Schober
authors.forename: H Amalia
authors.initials: HA
authors.lastname: Pasolli
authors.forename: Nicole
authors.initials: N
authors.lastname: Stokes
authors.forename: June
authors.initials: J
authors.lastname: Dela Cruz-Racelis
authors.forename: Elaine
authors.initials: E
authors.lastname: Fuchs
mesh_terms: D000818:Animals; D019070:Cell Lineage; D002478:Cells, Cultured; D005260:Female; D051523:Fibroblast Growth Factor 7 / Q000235:genetics / Q000378:metabolism; D018859:Hair Follicle / Q000166:cytology / Q000502:physiology; D051379:Mice; D008822:Mice, Transgenic; D009024:Morphogenesis / Q000502:physiology; D012038:Regeneration / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D013234:Stem Cells / Q000166:cytology / Q000502:physiology*; D014158:Transcription, Genetic; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
chemical_list: C496454:Fgf7 protein, mouse; D051153:Wnt Proteins; D051176:beta Catenin; D051523:Fibroblast Growth Factor 7