Shearing of synovial fluid activates latent TGF-β

M. B. Albro, A. D. Cigan, R. J. Nims, K. J. Yeroushalmi, S. R. Oungoulian, C. T. Hung, G. A. Ateshian

Research output: Contribution to journalArticlepeer-review

65 Scopus citations

Abstract

Objective: TGF-β is synthesized in an inactive latent complex that is unable to bind to membrane receptors, thus unable to induce a cellular biological response until it has been activated. In addition to activation by chemical mediators, recent studies have demonstrated that mechanical forces may activate latent TGF-β via integrin-mediated cellular contractions, or mechanical shearing of blood serum. Since TGF-β is present in synovial fluid in latent form, and since normal diarthrodial joint function produces fluid shear, this study tested the hypothesis that the native latent TGF-β1 of synovial fluid can be activated by shearing. Design: Synovial fluid from 26 bovine joints and three adult human joints was sheared at mean shear rates up to 4000 s-1 for up to 15 h. Results: Unsheared synovial fluid was found to contain high levels of latent TGF-β1 (4.35 ± 2.02 ng/mL bovine, 1.84 ± 0.89 ng/mL human; mean ± radius of 95% confidence interval) and low amounts (<0.05 ng/mL) of the active peptide. Synovial fluid concentrations of active TGF-β1 increased monotonically with shear rate and shearing duration, reaching levels of 2.64 ± 1.22 ng/mL for bovine and 0.60 ± 0.39 ng/mL for human synovial fluid. Following termination of shearing, there was no statistical change in these active levels over the next 8 h for either species, demonstrating long-term stability of the activated peptide. The unsheared control group continued to exhibit negligible levels of active TGF-β1 at all times. Conclusions: Results confirmed the hypothesis of this study and suggest that shearing of synovial fluid might contribute an additional biosynthetic effect of mechanical loading of diarthrodial joints.

Original languageEnglish
Pages (from-to)1374-1382
Number of pages9
JournalOsteoarthritis and Cartilage
Volume20
Issue number11
DOIs
StatePublished - Nov 2012

Keywords

  • Cartilage
  • Mechanical shearing
  • Synovial fluid
  • TGF-β activation

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