Expression and secretion of parathyroid hormone-related protein by human bone-derived cells in vitro : effects of glucocorticoids

We investigated the production of parathyroid hormone-related protein (PTHrP) by cells derived from explants of human bone. Using an immunoradiometric assay (iRMA), PTHrP was detected in conditioned medium from cultures of fine-derived cells from 6 of 7 patients investigated in this study. PTHrP mRNA was identified in human bone cells using reverse transcriptase-linked polymerase chain reaction (RT-PCR) and by Northern analysis. Transcripts for PTHrP were detected in a purified population of alkaline phosphatase positive cells isolated from human bone marrow cultures by flow cytometry, confirming the expression of PTHrP mRNA by cells of the osteoblastic lineage. Production of PTHrP was inhibited by 10 -6 M of the glucocorticoids, prednisolone and desacetylated deflazacort, in a dose-dependent manner. In addition, RT-PCR followed by Southern blot analysis detected a decrease in steady-state PTHrP mRNA in cultures of human bone-derived cells treated with 10 -6 M prednisolone