Possible Functional Significance of Spatial Relationship Between Merkel Cells and Langerhans Cells in Human Hair Follicles

Abstract

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.