IGF-1 does not moderate the time-dependent transcriptional patterns of key homeostatic genes induced by sustained compression of bovine cartilage

C. A. Wheeler, S. R. Jafarzadeh, David M Rocke, A. J. Grodzinsky

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

Objective: To determine changes in chondrocyte transcription of a range of anabolic, catabolic and signaling genes following simultaneous treatment of cartilage with Insulin-like growth factor-1 (IGF-1) and ramp-and-hold mechanical compression, and compare with effects on biosynthesis. Methods: Explant disks of bovine calf cartilage were slowly compressed (unconfined) over 3-min to their 1 mm cut-thickness (0%-compression) or to 50%-compression with or without 300 ng/ml IGF-1. Expression of 24 genes involved in cartilage homeostasis was measured using qPCR at 2, 8, 24, 32, 48 h after compression ±IGF-1. Clustering analysis was used to identify groups of co-expressed genes to further elucidate mechanistic pathways. Results: IGF-1 alone stimulated gene expression of aggrecan and collagen II, but simultaneous 24h compression suppressed this effect. Compression alone up-regulated expression of matrix metalloproteinase (MMP)-3, MMP-13, a disintegrin and metalloproteinase with thrombospondin motif (ADAMTS)-5 and transforming growth factor (TGF)-β, an effect not reversed by simultaneous IGF-1 treatment. Temporal changes in expression following IGF-1 treatment were generally slower than that following compression. Clustering analysis revealed five distinct groups within which the pairings, tissue inhibitor of metalloproteinase (TIMP)-3 and ADAMTS-5, MMP-1 and IGF-2, and IGF-1 and Collagen II, were all robustly co-expressed, suggesting inherent regulation and feedback in chondrocyte gene expression. While aggrecan synthesis was transcriptionally regulated by IGF-1, inhibition of aggrecan synthesis by sustained compression appeared post-transcriptionally regulated. Conclusion: Sustained compression markedly altered the effects of IGF-1 on expression of genes involved in cartilage homeostasis, while IGF-1 was largely unable to moderate the transcriptional effects of compression alone. The demonstrated co-expressed gene pairings suggest a balance of anabolic and catabolic activity following simultaneous mechanical and growth factor stimuli.

Original languageEnglish (US)
Pages (from-to)930-938
Number of pages9
JournalOsteoarthritis and Cartilage
Volume17
Issue number7
DOIs
StatePublished - Jul 2009

Keywords

  • Chondrocyte gene expression
  • Growth factor treatment
  • IGF-1
  • Mechanical compression
  • Mechanobiology

ASJC Scopus subject areas

  • Biomedical Engineering
  • Orthopedics and Sports Medicine
  • Rheumatology

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