TY - JOUR T1 - [Hair cycle dynamics: the case of the human hair follicle]. A1 - Bernard,Bruno A, PY - 2003/7/19/pubmed PY - 2003/12/3/medline PY - 2003/7/19/entrez SP - 57 EP - 61 JF - Journal de la Societe de biologie JO - J Soc Biol VL - 197 IS - 1 N2 - The existence of a growth and regeneration cycle makes the hair follicle a true paradigm of tissue homeostasis. Analysis of about 9000 cycles led us to propose a stochastic model of human hair dynamics. The existence of hair cycles implies that stem cells must be cyclically activated and hair melanin unit has to be renewed. Using different markers, we were able to identify two distinct epithelial stem cell reservoirs, located in the upper and lower thirds of the anagen hair follicle outer root sheath. These two reservoirs fuse during the regression phase and individualize again in the new forming anagen hair follicle. Using a set of antibodies specific of melanocyte lineage and melanogenesis, pigmentation unit turnover was followed throughout the entire hair cycle. In the terminal anagen hair, active melanocytes were localized on top of the dermal papilla, while amelanotic melanocytes were identified in the upper third of the outer root sheath (ORS). Those amelanotic melanocytes located in upper ORS probably represented a melanocyte reservoir for successive hair generation, since at the induction of anagen phase, some melanocytes were committed to cell division and melanogenesis was turned on, but only in the nascent hair bulb, close to the dermal papilla. SN - 1295-0661 UR - https://www.unboundmedicine.com/medline/citation/12868268/[Hair_cycle_dynamics:_the_case_of_the_human_hair_follicle]_ DB - PRIME DP - Unbound Medicine ER -