Transcriptional induction of connective tissue growth factor/hypertrophic chondrocyte-specific 24 gene by dexamethasone in human chondrocytic cells

Bone. 2003 Oct;33(4):694-702. doi: 10.1016/s8756-3282(03)00227-8.

Abstract

Connective tissue growth factor (CTGF/Hcs24) is a critical growth factor for chondrocytic growth and differentiation. In this report, we describe for the first time glucocorticoid-mediated induction of the CTGF/Hcs24 gene in a chondrocytic cell line, HCS-2/8. Steady-state mRNA levels of CTGF/Hcs24 were remarkably increased after treatment with 50 nM dexamethasone, as confirmed by Northern blotting and quantitative real-time polymerase chain reaction (PCR) analysis. Corresponding to the increase in mRNA, production of CTGF/Hcs24 protein was remarkably enhanced, following a time course of up to 6 h. The observed increase in mRNA can be ascribed to transcriptional enhancement, since the stability of CTGF/Hcs24 mRNA was not affected by the same concentration of dexamethasone, which was indicated by the results of an mRNA degradation assay. However, unexpectedly, the prototypic ctgf/hcs24 promoter was not responsible for the dexamethasone stimulation, suggesting the glucocorticoid receptor binding site(s) to be elsewhere in the CTGF/Hcs24 gene. Enhancement of the prototypic promoter activity by dexamethasone was observed in murine fibroblastic cells, demonstrating the complexity of the regulatory mechanism of ctgf/hcs24 gene expression. Of importance, dexamethasone at the same concentration significantly stimulated proteoglycan synthesis in HCS-2/8 cells up to the same levels as exogenously added CTGF/Hcs24. These findings represent a novel effect of glucocorticoid on the production of CTGF/Hcs24 by chondrocytic cells, and indicate that CTGF/Hcs24 may mediate the stimulative effect of dexamethasone on chondrocytic phenotypes. Also, our results shed light on the complex mechanism of CTGF/Hcs24 induction by glucocorticoids.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3' Untranslated Regions
  • Cell Line
  • Chondrocytes / drug effects*
  • Chondrocytes / metabolism*
  • Connective Tissue Growth Factor
  • Dexamethasone / pharmacology*
  • Humans
  • Immediate-Early Proteins / genetics*
  • Intercellular Signaling Peptides and Proteins / genetics*
  • Promoter Regions, Genetic / drug effects
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Transcription, Genetic / drug effects

Substances

  • 3' Untranslated Regions
  • CCN2 protein, human
  • Immediate-Early Proteins
  • Intercellular Signaling Peptides and Proteins
  • RNA, Messenger
  • Connective Tissue Growth Factor
  • Dexamethasone