title: The Modulatable Stem Cell Niche: Tissue Interactions during Hair and Feather Follicle Regeneration.
abstract: Hair and feathers are unique because (1) their stem cells are contained within a follicle structure, (2) they undergo cyclic regeneration repetitively throughout life, (3) regeneration occurs physiologically in healthy individuals and (4) regeneration is also induced in response to injury. Precise control of this cyclic regeneration process is essential for maintaining the homeostasis of living organisms. While stem cells are regulated by the intra-follicle-adjacent micro-environmental niche, this niche is also modulated dynamically by extra-follicular macro-environmental signals, allowing stem cells to adapt to a larger changing environment and physiological needs. Here we review several examples of macro-environments that communicate with the follicles: intradermal adipose tissue, innate immune system, sex hormones, aging, circadian rhythm and seasonal rhythms. Related diseases are also discussed. Unveiling the mechanisms of how stem cell niches are modulated provides clues for regenerative medicine. Given that stem cells are hard to manipulate, focusing translational therapeutic applications at the environments appears to be a more practical approach.
authors.affiliation: Department of Pathology, University of Southern California, Los Angeles, CA 90033, USA; Department of Dermatology, Taipei Veterans General Hospital, Taipei, Taiwan 112; Institute of Clinical Medicine and Department of Dermatology, National Yang-Ming University, Taipei, Taiwan 112.
authors.forename: Chih-Chiang
authors.initials: CC
authors.lastname: Chen
authors.affiliation: Department of Developmental and Cell Biology, Sue and Bill Gross Stem Cell Research Center, Center for Complex Biological Systems, University of California, Irvine, CA 92697, USA.
authors.forename: Maksim V
authors.initials: MV
authors.lastname: Plikus
authors.affiliation: Department of Pathology, University of Southern California, Los Angeles, CA 90033, USA; Department of Animal Science and Center for the Integrative and Evolutionary, National Chung Hsing University, Taichung, Taiwan 402.
authors.forename: Pin-Chi
authors.initials: PC
authors.lastname: Tang
authors.affiliation: Department of Pathology, University of Southern California, Los Angeles, CA 90033, USA.
authors.forename: Randall B
authors.initials: RB
authors.lastname: Widelitz
authors.affiliation: Department of Pathology, University of Southern California, Los Angeles, CA 90033, USA; International Laboratory of Wound Repair and Regeneration, Graduated Institute of Clinical Medicine, National Cheng Kung University, Tainan, Taiwan 701; Integrative Stem Cell Center, China Medical University, Taichung, Taiwan 404. Electronic address: cmchuong@usc.edu.
authors.forename: Cheng Ming
authors.initials: CM
authors.lastname: Chuong
mesh_terms: D000818:Animals; D005241:Feathers / Q000166:cytology / Q000502:physiology*; D018859:Hair Follicle / Q000166:cytology / Q000502:physiology*; D006801:Humans; D012038:Regeneration / Q000502:physiology*; D055153:Stem Cell Niche / Q000502:physiology*; D054457:Tissue Scaffolds
keywords: aging; circadian rhythm; immune response; quorum sensing; stem cell