24.    Human hair follicles express genes for all components of potassium channels, enabling direct responses to minoxidil and other types of potassium channel regulators.
Katie Shorter, Steve M Picksley, Val A Randall. Department of Biomedical Sciences, University of Bradford, Bradford, UK.

How minoxidil, a widely used treatment for hair loss, actually acts is not well understood. Suggested mechanisms include stimulation of the vasculature or ATP-sensitive potassium (KATP) channels within the follicle itself. KATP channels consist of inwardly rectifying K+ channel (Kir) and regulatory sulfonylurea receptors (SUR). Although deer follicles are directly regulated by potassium channel regulators in vitro, human studies are predominantly negative. This study was designed to determine whether genes for both specific sulphonylurea receptors, (SUR1, SUR2A, SUR2B) and the actual pore channel protein itself (Kir6.2) are expressed in human follicles. Human scalp was treated with RNAlater™ stabilisation reagent to preserve mRNA. Anagen follicles were isolated by micro-dissection, pooled and total RNA extracted. RNA quality was checked before poly(A)RNA isolation; DNase treatment removed any contaminating DNA, before cDNA synthesis by reverse transcription. Reverse transcription-polymerase chain reaction (RT-PCR) was carried out using primer sets designed to detect Kir6.2, SUR1, SUR2A and SUR2B. cDNA quality was assessed by RT-PCR using primers for the highly expressed gene, beta-actin. PCR products were separated by gel electrophoresis and appropriately sized bands sequenced. Beta-actin was expressed in all 5 samples, confirming cDNA quality. Bands were produced which correlated to Kir6.2, SUR1 and SUR2B; no bands corresponding to SUR2A were detected. Sequence analysis of all products confirmed homology to the known human gene sequences. These results confirm for the first time that human hair follicles express the genes for all components of KATP channels; the Kir6.2 channel protein and two different sulphonylurea receptors SUR1 and SUR2B. The SUR2B form, previously detected in human cultured dermal papilla cells, would facilitate hair growth stimulation by minoxidil; however, the SUR1 form would not respond to minoxidil and has not previously been reported in human follicles. Further studies of these channels should lead to novel treatments for hair loss.