Assuntos
Folículo Piloso/metabolismo , Cabelo/metabolismo , Queratinócitos/fisiologia , Couro Cabeludo/citologia , Canais de Cátion TRPM/metabolismo , Proliferação de Células , Células Cultivadas , Regulação da Expressão Gênica , Técnicas de Silenciamento de Genes , Voluntários Saudáveis , Humanos , Fator de Crescimento Insulin-Like I/genética , Masculino , Organogênese , Transdução de Sinais , Canais de Cátion TRPM/genética , Fator de Crescimento Transformador beta2/genéticaRESUMO
The pilosebaceous unit (PSU) and the eccrine sweat gland (ESG) are classically described as completely independent skin appendages. However, careful inspection of scalp follicular units reveals that the secretory segment of the ESG spatially approximates the hair follicle in a position below the sebaceous gland and the insertion of the arrector pili muscle. Therefore, we propose here that, contrary to conventional wisdom, the PSU and the ESG should not be viewed in isolation, and may form instead, along with the arrector pili muscle and the apocrine gland (where present),one functional unit. For this, we suggest the more inclusive term of 'Hair Cluster' (HC). If confirmed, e.g. by 3D imaging techniques, the novel concept of a functional HC, whose individual components may communicate via secreted molecules and may share selected progenitor cell populations for HC repair/regeneration, has major physiological and pathological implications, which are briefly discussed.
Assuntos
Glândulas Écrinas/anatomia & histologia , Folículo Piloso/anatomia & histologia , Couro Cabeludo/anatomia & histologia , Glândulas Apócrinas/anatomia & histologia , Humanos , Músculo Liso/anatomia & histologia , Couro Cabeludo/fisiologiaRESUMO
Compared to murine models, data on cells responsible for the homeostasis of human epidermis are scarce and often contradictory. Given the conflicting results and the availability of clinical grade protocols to purify CD34 cells from a given tissue, we pursued to phenotypically characterize human epidermal CD34+ population. After magnetic separation of whole skin CD34+ and CD34- cell fractions and selection for cells highly adherent to extracellular matrix, both CD34+/- fractions retained the ability to form a stratified epidermis in organotypic cultures and presented similar in vitro migratory phenotypes. However CD34- cells showed higher clonogenic potential and in vitro proliferative capacity. These results indicated that CD34- cell fraction contains stem/early progenitor cells, while CD34+ cells might be a transit-amplifying precursor for hair follicle (HF) sheath cells. The ability to isolate living cells using differential cell adhesion and surface markers provides an opportunity to study cells from different morphological regions of the HF.
