Expression of vascular endothelial growth factor (VEGF) in various compartments of the human hair follicle.

Hair follicle vascularization appears to be closely related to the processes involved in hair cycle regulation, in which growth factors, cytokines and other bioactive molecules are involved. In particular, vascular endothelial growth factor (VEGF), essential for angiogenesis and vascular permeability, may be responsible for maintaining proper vasculature around the hair follicle during the anagen growth phase. The aim of our study was to compare the in vitro angiogenic capacity, i.e. the steady-state expression of the VEGF gene, of different cultured cell types derived from normal human hair follicles, corresponding to different follicular compartments. Human dermal papilla cells (DPC), fibrous sheath fibroblasts, dermal fibroblasts, and follicular and interfollicular keratinocytes were cultured and studied in vitro for VEGF expression at the mRNA level using RT-PCR, and for VEGF protein synthesis by radioimmunoprecipitation and immunocytochemistry. In vivo examination for VEGF expression in human terminal hair follicles was performed using immunohistochemical methods. In the present report the expression of four different VEGF molecular isoforms, differing in their angiogenic capacity, are described in different cultured follicular cell types for the first time. Cultured follicular cells strongly expressed mRNA of four VEGF molecular species identified as the 121-, 145-, 165- and 189-amino acid splice variants, the most prominent being the 121-amino acid molecule. DPC, and also other mesenchymal cells such as fibrous sheath fibroblasts and dermal fibroblasts, in vivo and in vitro strongly expressed VEGF mRNA and synthesized a 46-kDa VEGF protein, whereas follicular and interfollicular keratinocytes in vitro expressed lower levels of VEGF mRNA and proteins than mesenchymal cells. As the highest expression of VEGF was found in DPC, we suggest that DPC are mainly responsible for angiogenic processes possibly related to the human hair cycle.