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Histological Study and Localization of Stem/ Progenitor Cells in Human Dental Follicle

A human dental follicle（hDF）is a connective tissue that comprises ectomesenchymal cells, which originate from the neural crest, and contains stem cells and/or progenitor cells of the periodontium. hDF have the capacity to commit to differentiation into multiple cell lineages, such as osteoblastic, adipogenic, and neurogenic. The aim of this study was to examine the histological findings and localize stem/progenitor cells in hDF. Our findings revealed that the hDF structure comprised 3 layers, including the outer, intervening, and inner layers. The outer layer seen to comprise fibrous connective tissue that contained fibroblasts and some peripheral nerves. The inner layer of the intervening layer comprised dense fibrous connective tissue with many fibroblast-like cells. The intervening layer contained eosin-stained collagen fiber. The collagen fibers were ar-ranged in the interior but were irregular in the outer layer. The intervening layer comprised slightly dense fibrous connective tissue, which contained The hDF samples were stained for the suggested markers for mesenchymal stem cells（i.e., CD90, CD106, and CD271）. The cells positive for CD90 and CD106 were most frequent in the inner layer of the crown side, whereas those that were positive for CD271 were frequent in the outer layer of crown side. The hDF samples were stained for the suggested markers for pluripotent stem cells（i.e., CD15, STRO-1, and Notch-1）. The cells positive for these markers were most frequent in the outer layer of root side. In conclusion, hDF comprised a 3-layer structure of outer, middle, and inner layers. Several cells that expressed stem cell markers were found in the outer layer of the hDF.