Possible Functional Significance of Spatial Relationship Between Merkel Cells and Langerhans Cells in Human Hair Follicl
Merkel cells and Langerhans cells share some similar characteristics such as the localization in hair follicles, close association with peripheral nerves and the localization of several neuropeptides. We found that Merkel cells and Langerhans cells were i
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Summary Merkel cells and Langerhans cells share some similar characteristics such as the localization in hair follicles, close association with peripheral nerves and the localization of several neuropeptides. We found that Merkel cells and Langerhans cells were in contact with each other in the bulge area of human hair follicles under normal physiological conditions. This spatial relationship could imply that Merkel cells and Langerhans cells have a functional linkage within the specific site when stem cells are present or immature Langerhans cells are harbored. Merkel cells communicating with Langerhans cells in human hair follicles and Langerhans cells residing within the bulge should be considered. One explanation is that Merkel cells may support Langerhans cells that migrate into the basal layer of the bulge and then settle into this microenvironment. These mature or immature Langerhans cells, which are inhibited from circulating from the bulge to other regions, including lymph nodes and epidermis, may play some role in cross talk among stem cells, Merkel cells and/or peripheral nerves.
Introduction Langerhans cells were first described in 1868 by Paul Langerhans, a German pathologist, and are dendritic cells principally situated in the epidermis. It was established by means of in vitro and in vivo experiments that these cells are bone marrow-derived leukocytes (Hosoi et al. 1993; Moresi and Hom 1997), which act as antigen-presenting cells, playing a key role in immune function (Merkel 1875; Narisawa et al. 1993, 1994). In recent years, Langerhans cells have been shown to express many neuropeptide receptors, and are closely connected with nerve fibers (Garcia-Cabellero et al. 1989). Langerhans cells belong to the neuroimmunocutaneous system (NICS; Tachibana et al. 1997). K. I. Baumann et al. (eds.), The Merkel Cell © Springer-Verlag Berlin Heidelberg 2003
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Cutaneous neuromediators are synthesized by nerve fibers and Merkel cells and also Langerhans cells, keratinocytes, melanocytes and all immune cells (Tachibana et al. 1997). Merkel cells and Langerhans cells are generally considered to be independent from one another. Merkel cells and Langerhans cells share some similar characteristics such as the localization in the hair follicle, close association with peripheral nerves and the localization of several neuropeptides. We found an anatomic relationship between Merkel cells and Langerhans cells in the bulge area of human hair follicles. We will attempt to interpret the new finding that Merkel cells and Langerhans cells contact each other in the bulge area of human hair follicles under normal physiological conditions and consider the nature of Merkel cells.
Materials and Methods Tissue. Normal scalp skin was embedded in paraffin and 8-1-1m serial transverse sections (200 sections) were prepared. Preparation of Vellus Hair Follicles. The epidermal sheets with attached velIus hair follicles were prepared with EDTA. Hair follicles were observed threedimensionally under a light microscope in the wet
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