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Research Papers

Influence of Cartilaginous Matrix Accumulation on Viscoelastic Response of Chondrocyte/Agarose Constructs Under Dynamic Compressive and Shear Loading

[+] Author and Article Information
Shogo Miyata

Department of Mechanical Engineering, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japanmiyata@mech.keio.ac.jp

Tetsuya Tateishi

Biomaterial Center, National Institute for Material Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan

Takashi Ushida

Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan

J Biomech Eng 130(5), 051016 (Sep 15, 2008) (6 pages) doi:10.1115/1.2970059 History: Received February 21, 2007; Revised September 14, 2007; Published September 15, 2008

A method has been developed to restore cartilage defects by culturing autologous chondrocytes to create a three dimensional tissue and then implanting the cultured tissue. In this kind of approach, it is important to characterize the dynamic mechanical behavior of the regenerated cartilaginous tissue, because these tissues need to bear various dynamic loadings in daily life. The objectives of this study were to evaluate in detail the dynamic viscoelastic responses of chondrocyte-seeded agarose gel cultures in compression and torsion (shear) and to determine the relationships between these mechanical responses and biochemical composition. The results showed that both the dynamic compressive and shear stiffness of the cultured constructs increased during culture. The relative energy dissipation in dynamic compression decreased, whereas that in dynamic shear increased during culture. Furthermore, correlation analyses showed that the sulfated glycosaminoglycan (sGAG) content of the cultured construct showed significant correlations with the dynamic modulus in both compression and shear situations. On the other hand, the loss tangent in dynamic compression, which represents the relative energy dissipation capability of the constructs, showed a low correlation with the sGAG content, whereas this capability in shear exhibited moderate correlation. In conclusion, we explored the dynamic viscoelasticity of the tissue-engineered cartilage in dynamic compression and shear, and determined correlations between viscoelasticity and biochemical composition.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of dynamic compression testing

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Figure 2

Schematic of dynamic shear testing

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Figure 3

Gross appearance of 2% agarose gel with no cells (a) and cultured constructs on days 0 (b) and 28 (c)

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Figure 4

Cross-section of toluidine blue stained specimens at days 3 (a), 10 (b), 14 (c), and 28 (d)

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Figure 5

sGAG concentration (mg/ml of disk volume) in chondrocyte/agarose constructs and no cell control construct versus time in culture. Each data point represents the mean and standard deviation of four samples. * indicates significant difference from day 0 (P<0.05).

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Figure 6

Dynamic compressive viscoelasticity of cultured chondrocyte/agarose constructs. Magnitude (a) and loss tangent (b) of dynamic compressive modulus as a function of frequency. Each data point represents the mean and standard deviation of four samples. * indicates significant difference (P<0.05) from the value at 0.01 Hz at the same time point. # indicates significant difference (P<0.05) from day 3 at each testing frequency.

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Figure 7

Dynamic shear viscoelasticity of cultured chondrocyte/agarose constructs showing the magnitude (a) and loss tangent (b) of dynamic shear modulus as a function of frequency. Each data point represents the mean and standard deviation of four samples. * indicates significant difference (P<0.05) from the value at 0.01 Hz at the same time point. # indicates significant difference (P<0.05) between day 3 and day 14 at each testing frequency.

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Figure 8

Scatter plots relating the sGAG content to dynamic compressive viscoelasticity (dynamic compressive modulus (|E∗|) and loss tangent (tan δc)) at low frequency (f=0.01 Hz). (a) sGAG versus |E∗|; (b) sGAG versus tan δc.

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Figure 9

Scatter plots relating the sGAG content to dynamic compressive viscoelasticity (dynamic compressive modulus (|E∗|) and loss tangent (tan δc)) at “walking” frequency (f=0.5 Hz). (a) sGAG versus |E∗|; (b) sGAG versus tan δc.

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Figure 10

Scatter plots relating the sGAG content to dynamic shear viscoelasticity (dynamic shear modulus (|G∗|) and loss tangent (tan δs)) at low frequency (f=0.01 Hz). (a) sGAG versus |G∗|; (b) sGAG versus tan δs.

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Figure 11

Scatter plots relating the sGAG content to dynamic shear viscoelasticity (dynamic shear modulus (|G∗|) and loss tangent (tan δs)) at “walking” frequency (f=0.5 Hz). (a) sGAG versus |G∗|; (b) sGAG versus tan δs.

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