EXPRESSION OF GROWTH-HORMONE RECEPTOR, INSULIN-LIKE GROWTH FACTOR-I (IGF-1) AND IGF-1 RECEPTOR MESSENGER-RNA AND PROTEINS IN HUMAN SKIN

A cDNA corresponding to the membrane receptor for growth hormone (GH) was amplified by polymerase chain reaction (PCR) directly from human skin. The cDNA was cloned and found to have complete sequence homology to the extracellular domain of human liver GH receptor (GH-R). Northern analysis, using the cloned GH-R as probe, revealed relatively higher levels of GH-R transcripts in cultured human dermal fibroblasts compared to cultured keratinocytes or keratome biopsies. Semi-quantitative PCR analysis indicated that the levels of GH-R mRNA in cultured melanocytes was similar to that in fibroblasts. The receptor protein encoded by GH-R mRNA in fibroblasts was shown by affinity cross-linking to have, an apparent M(r) of 115-120 kDa, similar to that of 3T3-F442A fibroblasts used as a control. mRNA transcripts for the major mediator of GH actions, insulin-like growth factor 1 (IGF-1), were detected by PCR in fibroblasts, melanocytes, and keratome biopsies, but not in keratinocytes. In contrast, IGF-1 receptor mRNA were abundant in cultured keratinocytes and skin biopsies, as determined by Northern analysis. IGF-1 but not GH (5-50 ng/ml) promoted clonal proliferation of cultured keratinocytes. In contrast, GH (10 ng/ml) after 5 d markedly increased fibroblast cell numbers (70%, p < 0.009) over 0.2% serum control. These data indicate that human skin cells possess the molecular elements necessary to respond to GH and raise the possibility that GH may influence skin growth in vivo.