Elevated expression of hypoxia inducible factor-2α in terminally differentiating growth plate chondrocytes

Alan James Stewart, B Houston, C Farquharson

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)

Abstract

Growth plate chondrocytes exist in a hypoxic environment where it is recognized that hypoxia-inducible factor-1alpha (HIF-1alpha) is essential for their survival. Its regulation of chondrocyte viability may be mediated by the increased expression of vascular endothelial growth factor (VEGF) and glycolytic enzymes. However, the full chondrocyte response to hypoxia and the molecular control of VEGF expression in relation to growth plate differentiation and vascularization remains poorly understood. Using Percoll density gradient centrifugation, chick chondrocytes were separated into populations of different maturational phenotype. A differential display analysis of the populations showed highly upregulated expression of HIF-2alpha mRNA during chondrocyte differentiation. HIF-2alpha is a homologue of the HIF-1alpha transcription factor, both of which play a role in the activation of a number of hypoxia responsive genes. HIF-1alpha mRNA was also found to be expressed, although levels of expression were found to be similar in all of the chondrocyte fractions. The elevated expression of HIF-2alpha during chondrocyte differentiation was accompanied by increased VEGF expression. Analysis of the murine chondrocyte cell line, ATDC5, which undergoes ordered maturation indicated that HIF-2alpha, VEGF, placental growth factor, and glucose transporter-1 expression all increased in parallel with chondrocyte differentiation. This observation was supported by immunohistochemistry on sections of mouse bone which showed staining corresponding to the presence of HIF-2alpha in hypertrophic growth plate chondrocytes. The presence of HIF-2alpha was also observed in articular chondrocytes but was restricted to the superficial tangential zone. HIF-2alpha is, therefore, likely to be involved in the initiation of blood vessel formation and a metabolic shift in the growth plate, processes crucial for endochondral ossification.
Original languageEnglish
Pages (from-to)435-440
Number of pages6
JournalJournal of Cellular Physiology
Volume206
Issue number2
DOIs
Publication statusPublished - Feb 2006

Keywords

  • Hypoxia-inducible factor-1-alpha
  • Endochondral bone-formation
  • PAS domain protein-1
  • Transcriptional regulation
  • Cell-line

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