P18 IMPLICATION OF PROTEIN KINASE C ISOFORMS IN THE REGULATION OF HAIR FOLLICLE VASCULARIZATION IN VIVO AND IN VITRO

Thibaut S., Lachgar S., Saint-Cyr F., Charveron M., Gall Y., Institut de Recherche Pierre Fabre, Laboratoire de Biologie Cellulaire Cutanée, Faculté de médecine de Rangueil, Toulouse, France.

Some members of the protein kinase C (PKC) family play a key regulatory role in a variety of cellular functions including gene expression, hormone secretion, cell growth and differenciation. Vascular Endothelial Growth Factor (VEGF) promotes endothelial cell proliferation and migration. PKC a, b1, d and q isoforms are described vascular endothelial cell functions (Shizukuda et al.,Circ.Res.,1999). In this study, we are interested by their involvement in the modulation of hair cells vascular responses in vivo and in vitro.

Firstly, we analysed PKC a, b1, d and q isoforms expression during the human hair cycle by immunohistochemistry. Western Blot and RT-PCR analysis were performed on cultured dermal papilla cells (DPC) in the presence of specific modulators of PKC isoforms e.g. PMA; calphostin C; safingol (PKC a inhibitor) and hispidin (PKC d inhibitor), and some tyrosin kinase inhibitors (Sugimoto et al., Biochem.Pharm., 2000). Immunohistochemical results showed that PKC isoforms expression is modified with the hair cycle. PKC a and d were highly expressed in dermal papilla during the anagen stage. The localisation of these two proteins was similar to that of VEGF receptors flt-1. PKC d expression decreased during catagen and telogen stages and PKC a localisation was restrcted to the outer root sheath and hair matrix. Western Blot analysis showed that PKC a and  d were also strongly expressed in vitro by cultured DPC. In parallel, we studied by RT-PCR analysis the VEGF receptors expression. These two responses were regulated by the different specific modulators of PKC isoforms.

Our results show that PKC a and d expression is associated with the growing stage of the hair cycle and suggest that VEGF receptors are required for the expression of these PKC isoforms.