Dynamic Confined Compression Alters Extracellular Matrix Synthesis And Mechanical Properties By Chondrocytes Cultured In Agarose-Gel

The articular cartilage defects caused by injuries or degenerative events are very common in clinic practice, yet it has a limited capacity of self-regeneration. At present, the research of treatment for cartilage defect focuses on regeneration and reconstruction. Given the well-known limitations of cartilage repair, many investigators have attempted to the search for methods of restoring the cartilage loss, but less effective methods can be applied for its therapy. In the past years, tissue engineering, a promising method for regeneration of tissue and organs, were introducing for the repair of cartilage. Articular cartilage is an important tissue of a joint. Its mechanical character plays a critical role in normal joint. The mechanical behavior of articular cartilage is essential for the research of movement mechanism, load carrying capacity and pathology of diarthrosis and has great significances and practical values for the treatment and diagnosis of arthropathy as well as the development of artificial tissue articular materials. Chondrocytes and the matrix composed of the cartilage tissue, whereas the chondrocytes, shielded from impacts by the collagen network, share little pressure. In view of this, we designed the experiment in the present work as follows:At first, we study the dynamic compression influence the matrix metabolite of cultured chondrocytes agarose gel. As rabbit knee chondrocytes agarose-gel had cultured 7d in static state, then divided into two groups, static comparison group and intermittent dynamic compression group. After static culture or intermittent compression under Flexercell 4000 compression system 7d, 14d and 21d, histochemistry analysis of extracellular matrix was determined.No obvious difference was observed between S₇ and I₇ or S₁₄ and I₁₄ by HE, toluidine blue and safranin O stain; but the amount of extracellular matrix in group I₂₁ increased compared to S₂₁.Second, we measured the mechanical properties of gel cultured cartilage tissue by the machine of material testing 5544. Chondrocytes/agarose constructs were cultured in static state or subjected to intermittent dynamic compression for 7d, 14d and 21d respectively. No significant difference was found among the Young's moduli of S₇ (0.558±0.036MPa), S₁₄ (0.586±0.095MPa), I₇ (0.56±0.041MPa) and I₁₄ (0.602±0.01MPa). A little significant difference was observed between S₂₁ (0.608±0.061MPa) and I₂₁ (0.799±0.013MPa).The curves of relax and creep were used to characterize viscoelastic behavior of different group of chondrocytes/agarose constructs. As for viscoelastic parameters E₁, E₂ andη, there was no significant difference between I₇, I₁₄ and S₇, S₁₄; While in I₂₁ group, they exhibited a significant increase compared to S₂₁ from relax curve. In creep curve, a significant difference was found between S₂₁ and I₂₁ in viscoelastic parameters E₁ andη, but no significant difference in other groups.This study will provide new insight on how mechanical loading influences the extracellular matrix synthesis. Furthermore, a detailed understanding of the mechanical properties of the chondrocytes/agarose constructs will facilitate the development of tissue engineering.