Research Papers

The Regional Sensitivity of Chondrocyte Gene Expression to Coactive Mechanical Load and Exogenous TNF-α Stimuli

[+] Author and Article Information
S. L. Bevill

Department of Physical and
Environmental Sciences,
Colorado Mesa University,
1100 North Avenue,
Grand Junction, CO 81501
e-mail: sbevill@coloradomesa.edu

K. A. Boyer

Department of Kinesiology,
University of Massachusetts-Amherst,
110 Totman Building,
30 Eastman Lane,
Amherst, MA 01003-9258
e-mail: kboyer@kin.umass.edu

T. P. Andriacchi

Department of Mechanical Engineering,
Stanford University,
227 Durand Building,
Stanford, CA 94305-4038;
Department of Orthopedic Surgery,
Stanford University Medical Center,
227 Durand Building,
Stanford, CA 94305-4038;
Bone and Joint Center of Excellence,
Palo Alto, CA
e-mail: tandriac@stanford.edu

1Corresponding author.

Manuscript received December 18, 2013; final manuscript received June 18, 2014; accepted manuscript posted July 2, 2014; published online July 15, 2014. Assoc. Editor: Carlijn V. C. Bouten.

J Biomech Eng 136(9), 091005 (Jul 15, 2014) (7 pages) Paper No: BIO-13-1579; doi: 10.1115/1.4027937 History: Received December 18, 2013; Revised June 18, 2014; Accepted July 02, 2014

Both mechanical load and elevated levels of proinflammatory cytokines have been associated with the risk for developing osteoarthritis (OA), yet the potential interaction of these mechanical and biological factors is not well understood. The purpose of this study was to evaluate the response of chondrocytes to the effects of dynamic unconfined compression, TNF-α, and the simultaneous effects of dynamic unconfined compression and TNF-α. The response to these three treatments was markedly different and, taken together, the response in the gene expression of chondrocytes to the different treatment conditions suggest a complex interaction between structure, biology, and mechanical loading.

Copyright © 2014 by ASME
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Fig. 1

Time course of study. Explants equilibrate in free-swelling culture for ∼48 h prior to being subjected to one of four treatment groups. After 6 h in the assigned treatment (e.g., dynamic unconfined compression), explants are digested and total RNA is isolated.

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Fig. 2

Validation of the 2−ΔΔCt method. ΔCt calculated as Ct,target gene − Ct,18 s for each cDNA dilution. Data were fit using a least-squares regression analysis (with each reaction run in triplicate) to calculate the slope of the best fit line. A slope < 0.1 indicates that amplification efficiencies are adequately similar to use the 2−ΔΔCt method [31].

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Fig. 3

Relative expression levels (averaged central and peripheral) of (a) type II collagen and aggrecan, (b) MMPs 1, 3, and 13, (c) ADAM-TS4, ADAM-TS5, and TNF-α. (d) TIMPs 1 and 2. * indicates significant difference (p < 0.05) from free-swelling control values, + indicates Load/TNF-α interaction term significant (MMP1, ADAM-TS5, TNF).

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Fig. 4

Relative expression of ADAM-TS4, stratified by region. * indicates significant difference relative to free-swelling controls and + indicates significant regional differences (p < 0.05).

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Fig. 5

Relative expression levels of CII (left) and aggrecan (right) stratified by region. * indicates significant difference from free-swelling controls and + indicates significant regional differences in the upregulation of mRNA (p < 0.05).

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Fig. 6

Relative expression of MMP1 (left) and MMP3 (right) stratified by region. * indicates significant difference from free-swelling controls, + indicates significant regional differences in the upregulation of mRNA.




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