Objective: neurotrophin - 3 (NT-3) and its high affinityreceptor tyrosine kinase C (TrK C) are essential for nervous system development. Recently, it has been shown thatthese members of the neurotrophin family are also involved in murine hair morhoenesis and ycling. However, their role in human hair follicle biology remains to be elucidated. As a first step towards this end, we have previously shown the immunohistochemical expression of NGF and TrK A in human skin and hair follicle (Adly and Nada..
Aim of work: In order continue exploring the role of neurotrophins in human skin and hair follicle biology, the immunreactivity (lR) of NT-3 and Trk C was studied, as a second step, in human scalp skin and hair follicles (Hf) in situ by immuucfluorescent and light microscopic immnunohistology.
Results: Both NT-3 and Trk C showed prominent, distinct IR patterns in human scalp anagen hair follicle (anagcn VI), whereas they were weakly expressed in catagen and re increased in telogen hair follicles. Within hair follicle compartment, NT-3 IR was prominent in ihe outer root sheath (ORSJ, inner ru1t sheath (IRS), dermal papilla (DPj and connective tissue sheath (CTS) Trk C IR was prominent in all hair follicle epithelial and mesenchymal compartments. Outside the hair follicle compartment, both NT-3 and Trk C showed prominent(IR) in the epidermis, sebaceous gland and sweat gland
Conclusion: These observations provide the first indication that NT-3 and Trk C are expressed in human scalp skin and HF, and suggest that Irk C- mediated signalling is involved, not only in murine, hut also in human HF biology, and promises prospective therapeutic strategy for the treatment of hair cycle and skin related disorders.
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