Analysis of the expression pattern of glial cell line-derived neurotrophic factor, neurturin, their cognate receptors GFRα-1 and GFRα-2, and a common signal transduction element c-Ret in the human scalp skin

Glial cell line-derived neurotrophic factor (GDNF) and a related family member, neurturin (NTN), as well as their cognate receptors (GDNF receptors, GFR alpha-1 and GFR alpha-2, respectively) are involved in nervous system development and murine hair cycle control. To date, their expression in human scalp skin is still unknown. The expression pattern of these proteins was examined in human scalp skin by immunofluorescence and immunoalkaline phosphatase staining methods as well as RT-PCR (GDNF). A total of 50 normal human scalp skin biopsy specimens were examined (healthy females, 53-57 years). The expression of GDNF protein was strong in the epidermis and sebaceous and sweat glands. In the epidermis, GDNF protein expression was seen in all layers except the stratum corneum. It was strong in the basal layer and decreased gradually towards the granular layer. The results of RT-PCR analysis revealed that GDNF protein is synthesised in the epidermis. The expression of NTN, GFR alpha-1, and GFR alpha-2 proteins was strong in the papillary dermis and sebaceous and sweat glands. In the epidermis, NTN protein expression was absent. The expression of GFR alpha-1 and GFR alpha-2 proteins was moderate in the epidermis. The expression of c-Ret protein was consistently strong in the epidermis and sebaceous and sweat glands. These proteins were strongly expressed in both epithelial and mesenchymal compartments of human anagen VI scalp hair follicles. Our investigation reports, for the first time, the expression patterns of GDNF, NTN, GFR alpha-1, GFR alpha-2, and c-Ret proteins in human scalp skin. The expression of these proteins in the skin suggests their possible roles in skin homeostasis. The clinical ramifications of these observations mandate further investigations.