Cultured Human Fibroblasts and Not Cultured Human Keratinocytes Express a PTH/PTHrP Receptor mRNA

There is increasing evidence that parathyroid hormone (PTH) and PTH-related peptides 0PTHrP) are involved in normal skin cell growth; therefore, we investigated whether the PTH/PTHrP receptor was expressed in cultured human keratinocytes and dermal fibroblasts. Northern analyses of poly (A)+ RNA isolated from cultured fibroblasts revealed two PTH/ PTHrP receptor transcripts with one major band at 2.5 kb and one minor band at 2.3 kb. These transcripts were consistent with those found in human osteosarcoma cells, which are known to express PTH/ PTHrP-R mRNAs. In contrast, after repeated Northern analyses no PTH/PTHrP receptor transcripts were found in poly (A)+K RNA isolated from cultured keratinocytes. Reverse-transcriptase/nested polymerase chain reaction analyses of total RNA isolated from cultured keratinocytes and fibroblasts confirmed the Northern analyses data that the PTH/ PTHrP receptor was expressed in cultured fibroblasts but not in cultured keratinocytes. When cultured fibroblasts and keratinocytes were exposed to 10-7 M PTH (1-34) there was a twofold increase in cAMP levels in the fibroblasts and no demonstrable increase was noted in keratinocytes. These results suggest that skin fibroblasts possess the classical PTH/PTHrP receptor and are target cells for PTH and PTHrP whereas keratinocytes do not have the receptor and are unresponsive to its N-terminal agonist in the stimulation of cAMP formation