P8 DIFFERENTIAL EXPRESSION OF CRH PEPTIDES AND RECEPTORS IN HAIR FOLLICLE CELLS IN SITU AND IN VITRO
Kauser S1, Slominski A2, Tobin DJ1
1Medical Biosciences, School of Life Sciences, University of Bradford, United Kingdom
2Dept. of Pathology, University of Tennessee, Memphis, USA

Corticotropin-releasing hormone (CRH) is the most proximal element of the hypothalamic-pituitary-adrenal axis (HPA) where it regulates pituitary POMC gene expression and the subsequent production and secretion of POMC peptides. Mammalian skin appears to contain an equivalent of the HPA axis comprised of locally-produced CRH that signals via CRH receptors -1 and -2 to regulate skin homeostasis. While we have recently demonstrated that CRH acts on the human epidermis and that CRH can stimulate HF melanocyte (HFM) differentiation in vitro, CRH action in human HF biology remains poorly characterized. In the current immunohisto(cyto)chemical study we extend this evaluation by assessing the expression of CRH and urocortin, in addition to their cognate receptors (CRH-R1 & CRH-R2), in specific cell populations of human haired scalp and in cultures of normal human scalp HF melanocytes (HFM), follicular keratinocytes (FK) and follicular papilla fibroblasts (FPF). Results showed that the expression of CRH, urocortin and CRH-R1/-R2 was confined to only a minor sub-population of gp100-positive melanocytes located in the most proximal and peripheral matrix of the anagen hair bulb and not in the melanogenically-actively hair bulb melanocytes. Moreover, CRH peptide and receptor expression was also detected in FK and FPF of anagen HF. Importantly; here the expression of these peptides and receptors was retained in these HF cell populations in vitro, although expression was heterogeneous and commonly associated with differentiation status. In summary, the differential expression of CRH, urocortin and their receptors in a sub-population of HFM in situ and in vitro suggests a potential role in the regulation of HFM differentiation through autocrine or paracrine mechanisms (e.g., from nearby FK or FPF). Furthermore, the up-regulation of expression of these peptides and receptors in certain sub-populations of FK and FPF may reflect a modulatory role for the CRH system in other aspects of hair biology.