F4 HUMAN HAIR FOLLICLES EXPRESS THE GENES FOR THE RECEPTOR FOR STEM CELL FACTOR (SCF), C-KIT, AS WELL AS TWO FORMS OF SCF: IMPLICATIONS FOR THE CONTROL OF HAIR PIGMENTATION
Vafaee T, Picksley SM, Randall VA
Department of Biomedical Sciences, University of Bradford, UNITED KINGDOM

The paracrine factor Stem Cell Factor (SCF) also known as Mast Cell Growth Factor (MGF), Steel factor or c-kit ligand (CL), regulates rodent hair pigmentation via a cell surface receptor, c-kit. We showed previously that SCF is secreted by cultured human dermal papilla cells suggesting that the dermal papilla is a local source of SCF. SCF exists in two forms: a soluble form, synthesised as a 248 amino acid form (cleaved for release to 165 amino acids), and a 220 amino acid form which remains bound to the plasma membrane. The aim of this study was to determine whether the genes for c-kit and the two forms of SCF are expressed in adult human hair follicles. Human skin samples were treated with RNA later to inhibit degradation of mRNA by ribonucleases, before, and while, the lower parts of individual anagen follicles were isolated by microdissection. Total and poly(A)RNA were isolated, cDNA prepared and then reverse transcription-polymerase chain reactions (RT-PCR) carried out with sets of primers for c-kit and SCF. cDNA quality was checked by parallel RT-PCR reactions with the highly expressed gene, ß-actin. PCR products were separated by gel electrophoresis, checked for appropriate size, extracted and sequenced. ß-actin was expressed in all samples. In addition, all follicles produced appropriate sized bands for c-kit, and both the soluble and membrane-bound forms of SCF. Sequence analysis showed 100% correlation with the known gene sequences. The expression of both the receptor, c-kit, and SCF within the lower part of human anagen hair follicles strongly supports a paracrine role for this signalling system in human hair pigmentation. The soluble form of SCF was expected, as this would correspond to the form secreted by dermal papilla cells, presumably to influence melanocytes in the hair bulb. The membrane-bound form has not been previously demonstrated in hair follicles.