P41 EXPRESSION OF PROLACTIN AND ITS RECEPTOR IN SKIN IS HAIR-CYCLE DEPENDENT AND PROLACTIN IS ABLE TO INDUCE CATAGEN IN MURINE SKIN ORGAN CULTURE

¹Krause K, ¹Paus R, ²Nixon A, ² Kelly S, ²Craven A, ²Pearson A, ¹Spexard T, ¹Moll I and ¹Foitzik K; ¹University Hospital Eppendorf, Hamburg, Germany, ²AgResearch, Ruakura Research Centre, Hamilton, New Zealand.

The anterior pituitary hormone prolactin (PRL), which is expressed in several extrapituitary tissues, has been implicated in hair follicle cycling and differing effects of PRL on hair growth have been reported in various species.  In sheep, prolactin receptors (PRLR) are expressed in the dermal papilla, outer root sheath (ORS), inner root sheath (IRS), matrix, sebaceous gland (SG), and PRL injection induces premature catagen.  Here, we provide the first study of PRL and PRLR expression during the murine hair cycle and report the influence of PRL on anagen hair follicles in murine skin organ culture.  

The long-form PRL-R transcript was shown by RT-PCR to be transiently down-regulated during early anagen, whereas PRL was up-regulated during mid anagen.  PRL-like immunoreactivity (IR) was detected in the ORS, epidermis, fibroblasts and capsule of the SG.  The dermal papilla was PRL-negative throughout the hair cycle. In the IRS, PRL was expressed temporarily during early anagen, but disappeared in late anagen and catagen.  In catagen follicles, PRL IR was seen in the secondary hair germ.  PRLR IR occurred in the distal part of the ORS around the developing IRS during anagen IV.  This was seen throughout anagen IV-VI in a specific area of the ORS, at a constant distance from the hair bulb, independent of the length of the hair follicle.  This PRLR IR disappeared again during late catagen and telogen.  The dermal papilla, SG, matrix and IRS were PRLR negative.  Addition of PRL (400ng/ml) to anagen hair follicles in murine skin organ culture for 72h induced premature catagen: 20% of PRL treated versus 7% of control hair follicles had entered late catagen (p<0,05).  These data show that PRL and PRLR expression are hair-cycle dependent and support the concept that locally generated PRL acts in a paracrine manner to modulate the hair cycle.