Two- and three-dimensional demonstrations of morphological alterations of early anagen hair follicle with special reference to the bulge area

Abstract

During late telogen to early anagen secondary hair germ is newly formed by the downgrowth of a clubbed column which is indistinguishable from the bulge. Serial vertical sections demonstrated that the early anagen terminal hair follicle formed the new secondary hair germ associated with a lateral protuberance of basaloid cells which could be considered as the bulge of the new hair follicle. Interestingly, the arrector pili muscle bundle was divided into two branches, one inserted into the original clubbed end and the other into this protuberance of the secondary hair germ. CAM5.2-reactive Merkel cells were present not only in the clubbed ends of the old follicle but also in the protuberance of the new hair germ. The formation of the lateral protuberance of the new hair germ preceded the appearance of CAM5.2-reactive Merkel cells in this location. Ks19.1 immunoreactivity was observed from the clubbed end to the upper half of the new hair germ. These phenomena occurred in early anagen before the club hairs were shed. It is postulated that the early anagen hair follicle formed the area within the new hair germ equivalent to the bulge and Merkel cells either moved from the bulge of the old hair follicle or differentiated de novo from immature epithelial cells. Merkel cells or their products in the bulge may serve as attractants for the readjusting arrector pili muscle to anchor to the bulge of the new hair follicle.

Manipulation of stem cell proliferation and lineage commitment:visualisation of label-retaining cells in wholemounts of mouse epidermis

“…1C,F). This protuberance of the outer root sheath may be caused by the presence of the club hair (Morris and Potten, 1994;Narisawa and Kohda, 1996;Stenn and Paus, 2001). Whereas the visible bulge lies on one side of the follicle (Cotsarelis et al, 1990;Morris and Potten, 1994), the LRC were usually distributed symmetrically (Fig.…”

“…As many hair follicles lack a physical bulge in the outer root sheath, the term 'bulge' has come to refer loosely to the permanent region of the follicle below the sebaceous gland (Morris and Potten, 1994;Narisawa and Kohda, 1996;Stenn and Paus, 2001). In wholemounts of tail and dorsal follicles, LRC typically were clustered symmetrically along the entire length of the permanent section of the follicle below the sebaceous glands.…”

Niche regulation of corneal epithelial stem cells at the limbus

“…In this regard, melanocytes, distributed in the limbal basal layer with their cellular projections extending to surrounding basal epithelial cells [51], may be one candidate of niche cells ( Figure 2). These cells produce and transport melanin pigments into epithelial cells so as to minimize damage caused by ultraviolet irradiation, a presumed action similarly described in the SC-containing bulge area of the human skin [65]. Little is known about the molecular mechanism explaining cytokine dialogues operating between melanocytes and limbal SCs, let alone between those of other cells in the vicinity.…”

Gene Correction by RNA‐DNA Oligonucleotides

“…Melanocytes are comprised of two distinct populations, melanogenic and amelanogenic cell types. Melanogenic cells are located only in the bulb matrix of the hair follicle, where they are distributed in close contact with the basal lamina separating the matrix and the dermal papilla (38). Transcription of the tyrosinase gene is highly tissue-specific and takes place only in melanogenic cells present in hair bulbs (39,40).…”

“…In contrast, amelanogenic cells do not express tyrosinase activity and are present throughout the outer root sheath of hair follicles. It has been hypothesized that these cells may be precursors of melanogenic cells (38). The hair growth is characterized by a period of hair fiber production and proliferation of cells (anagen), a brief regression phase resulting in the loss of up to 70% of the hair follicle (catagen) and the resting period of minimal activity (telogen) (41,42 during the anagen stage of the hair cycle (43).…”