095 Expression of Insulin-Like Growth Factors in the Hair Cycle of Rats

P. I. Hynd and N. M. Penno Dept. of Animal Science, Adelaide University, Roseworthy Campus, Roseworthy, South Australia, Australia, 5371.

The insulin-like growth factors (IGF) are thought to play a role in the regulation of hair growth, but presentation of IGF to their receptors depends on binding proteins (IGFBP-1to -6) in tissues. We report here the sites of expression of mRNA for the six IGFBP throughout the rat hair cycle. In situ hybridisation to DIG-labelled mRNA probes for the six rat IGFBP was used to identify the sites of expression throughout the hair cycle in skin from the back of rats from days 3 to 35 after birth. Histone mRNA expression was used as a positive control and sense probes used as negative controls. The positive histone control identified strong and specific labelling of the mitotic region of the follicle bulbs as expected. Sense probes were largely colour-free. IGFBP- Telogen (21d) Anagen 1 (3-5d) Catagen (20d) Anagen 2 (19d) 1 ORS nd nd nd 2 DP condensate ORS, BC, DPC, E KZ ORS, BC, DPC, E 3 DP condensate nd DPC nd 4 DP condensate DPCells (few) nd nd 5 DP condensate fibre tip, I BC (few) nd 6 nd nd nd nd (ORS outer root sheath; DP dermal papilla; BC bulb cells; KZ keratinising zone; E epidermis; I infundibulum; nd not detected) Spatial differences within the hair follicle, and changes in the expression of the IGFBP in the hair cycle, lend credence to the possibility that the IGFBP may regulate the action of IGF and alter follicle activity. In contrast to Batch et al. (1996) we did not detect IGFBP-3 and -5 in the dermal papilla of anagen follicles, although these binding proteins were detected in the dermal papilla condensate of inactive follicles. Further work is required to clarify these discrepancies and to elucidate the role of the IGF axis in the regulation of hair follicles. Batch, J. A., Mercuri, F. A. And Werther, G. A. (1996). J. Invest. Dermatol. 106:471-475.