IDENTIFICATION AND LOCALIZATION OF INSULIN-LIKE GROWTH FACTOR-BINDINGPROTEIN (IGFBP) MESSENGER-RNAS IN HUMAN HAIR FOLLICLE DERMAL PAPILLA

The role of the insulin-like growth factors (IGFs) in hair follicle bi ology has recently been recognized, although their actions, sites of p roduction, and modulation by the insulin-like growth factor-binding pr oteins (IGFBPs) have not to date been defined. IGF-I is essential for normal hair growth and development, and may be important in regulation of the hair growth cycle, In many culture systems, IGF-I actions are modulated by the IGFBPs. Thus, if IGFBPs are produced in the human hai r follicle, they may play a role in targeting IGF-I to its receptor or may modulate IGF-I action by interaction with matrix proteins. We hav e used in situ hybridization to localize messenger RNA for the six IGF BPs in anagen hair follicles, Anti-sense and sense RNA probes for the IGFBPs (IGFBP-1 to -6) were produced, and 5-mu m sections of adult fac ial skin were probed. Messenger RNA for IGFBP-3, -4, and -5 were ident ified, with predominantly IGFBP-3 and -5 mRNA found in the dermal papi lla, and to a lesser extent IGFBP-4 mRNA. IGFBP-C mRNA was also found at the dermal papilla/epithelial matrix border, Messenger RNAs for bot h IGFBP-4 and -5 were also demonstrated in the dermal sheath surroundi ng the hair follicle. Messenger RNAs for IGFBP-1, -2, and -6 were not identified, These studies demonstrate specific localization of IGFBP m RNAs in hair follicles, suggesting that they each play specific roles in the local modulation of IGF action during the hair growth cycle.