References: Hair growth and hair loss
FASEB J. 1998 Mar;12(3):287-97.
Hair cycle-dependent expression of corticotropin-releasing factor (CRF) and CRF receptors in murine skin.
Roloff B, Fechner K, Slominski A, Furkert J, Botchkarev VA, Bulfone-Paus S, Zipper J, Krause E, Paus R.
Institute of Molecular Pharmacology, Berlin, Germany.
We demonstrate the presence and hair cycle-dependent expression of corticotropin-releasing factor (CRF) and CRF receptors (CRF-R) in C57BL/6 mouse skin. To correlate this with a physiological, developmentally controlled tissue remodeling process, we have analyzed CRF and CRF-R expression during defined stages of the murine hair cycle with its rhythmic changes between growth (anagen), regression (catagen), and resting (telogen). Using reversed-phase HPLC combined with two independent anti-CRF radioimmunoassays, we have identified CRF in murine skin. Maximal CRF levels were found in anagen III-IV skin, and minimal values were detected in catagen and telogen skin. By immunofluorescence, maximal CRF immunoreactivity (CRF-IR) was seen in the basal epidermis, nerve bundles of skin, the outer root sheath and matrix region of anagen IV-VI follicles, and in defined sections of their perifollicular neural network, whereas catagen and telogen skin displayed minimal CRF-IR. Using quantitative autoradiography and 125I-CRF as a tracer, high-affinity binding sites for CRF were detected in murine skin. The highest density of specific binding sites was detected in the panniculus carnosus, the epidermis, and the hair follicle. CRF-R type 1 (CRF-R1) IR was detected by immunohistology mainly in the outer root sheath, hair matrix, and dermal papilla of anagen VI follicles, as well as in the inner and outer root sheaths of early catagen follicles. CRF-R1 expression was also hair cycle dependent. Therefore, in normal murine skin, the CRF-CRF-R signaling system may operate as an additional neuroendocrine pathway regulating skin functions, possibly in the context of cutaneous stress responses.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9506472&dopt=Abstract
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The human hair cycle is characterized by successive phases of growth and involution that imply tissue regression and regeneration. As a consequence, the hair melanin unit has to be renewed in a cyclic manner. Actually, the behavior of human hair follicle melanocytes throughout the hair cycle has been poorly studied. Thus, the origin of melanocytes present in the bulb after human hair regeneration is still not clarified, and neither are the events that control the melanin biosynthesis activity in the human hair bulb. In this study, we showed at the cellular level that in human pigmented hair follicles, the expression of tyrosinase and tyrosinase-related protein-1 (TRP-1) was detectable during the anagen phases III/IV through VI, only in those melanocytes which were located in the bulb. During the catagen phase, the two evaluated melanogenic enzymes were detectable no more, although melanocytes were still present in the preceding bulbar area. The epithelial column of catagen follicles and the capsule of telogen follicles also contained inactive melanocytes as evidenced by pMel-17 labeling. At the induction of a new anagen hair follicle, some melanocytes were committed to cell division, but only when located in the nascent bulb close to the dermal papilla. Our results emphasize the close relationship between melanogenesis and the hair cycle and suggest that in humans, melanogenesis is restricted to anagen hair follicles not because of the regulation of tyrosinase activity, but because of melanogenic enzyme expression, e.g., tyrosinase and TRP-1. Furthermore, the fact that in the newly developing anagen hair follicles, cell-division commitment and tyrosinase and TRP-1 expression were observed in melanocytes only when located in the nascent bulb suggests a highly regio-specific melanocyte stimulation in early the anagen phase.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10952393&dopt=Abstract
Neuroreport. 1998 Jan 26;9(2):263-8.
Replacement of mammalian auditory hair cells.
Zine A, de Ribaupierre F.
Institut de Physiologie, Lausanne, Switzerland.
We investigated the potential for hair cell regeneration in neonatal rat organs of Corti grown in culture following destruction of hair cells by neomycin toxicity. Replacement hair cells were observed by light and scanning electron microscopy in lesion sites in the cultures treated with transforming growth factor-alpha, epidermal growth factor or a combination of both factors for 5-7 days post-injury. These new cells had morphological characteristics of immature hair cells. Autoradiographic localization of [3H]thymidine-labelled cells on semi-thin sections indicated that these replacement hair cells did not arise through renewed mitotic division, although an important mitotic proliferation was observed outside the area of supporting and sensory cells.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9507966&dopt=Abstract
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