Matrix fixed‐charge density as determined by magnetic resonance microscopy of bioreactor‐derived hyaline cartilage correlates with biochemical and biomechanical properties

Abstract

Objective. To use noninvasive magnetic resonance imaging (MRI), biochemical analyses, and mechanical testing of engineered neocartilage grown in a hollowfiber bioreactor (HFBR) to establish tissue properties, and to test the hypothesis that MRI can be used to monitor biochemical and biomechanical properties of neocartilage.Methods. Chondrocytes from day 16 embryonic chick sterna were inoculated into an HFBR and maintained for up to 4 weeks with and without exposure to chondroitinase ABC. The fixed-charge density (FCD) of the cartilage was determined using the MRI gadolinium exclusion method. The sulfated glycosaminoglycan (S-GAG), hydroxyproline, and DNA contents were determined using biochemical procedures, while dynamic and equilibrium moduli were determined from mechanical indentation tests.Results. S-GAG content, tissue cross-sectional area, and equilibrium modulus of the neocartilage increased with development time. There was a gradient of S-GAG content across the length of control neocartilage at the 4-week time point, with higher values being found toward the inflow region. Exposure to chondroitinase ABC resulted in a decrease in tissue area, negative FCD, proteoglycan content, and equilibrium and dynamic moduli. The treated bioreactors displayed a lengthwise variation in S-GAG content, with higher values toward the outflow end. Linear correlations were established among FCD, proteoglycan content, and biomechanical properties.Conclusion. HFBR-derived neocartilage showed regional variation in S-GAG content under control conditions, and in the decrease of S-GAG in response to enzyme treatment. In addition, the results support the hypothesis that tissue parameters derived from MRI can be used to noninvasively monitor focal neocartilage formation and biochemical and biomechanical properties.

Material Properties of Fresh Cold-stored Allografts for Osteochondral Defects at 1 Year

“…The equilibrium aggregate moduli of full-thickness cartilage samples were determined by confined compression tests using a custom-designed, computer-automated soft tissue tester as previously described [12,14,60,61]. Confined compression testing was used to assess the biomechanical function of the transplanted cartilage.…”

“…Equilibrium aggregate modulus of the specimens was determined using a five-step stress relaxation test after removal from the subchondral bone. Specimens were immersed in a PBS solution with protease inhibitors (Sigma Chemicals, St Louis, MO) and tested using the custom-designed biomechanical test apparatus previously described [12,14,61]. Specimens were compressed using a 5-mm diameter nonporous indenter with 25-lm predisplacement to ensure uniform initial contact with the indenter.…”

Noninvasive Assessment of Glycosaminoglycan Production in Injectable Tissue-Engineered Cartilage Constructs Using Magnetic Resonance Imaging

“…The application of magnetic resonance imaging (MRI) for visualizing cartilage clinically has been well established, 1,2 while more recently, approaches have been developed to monitor cartilage matrix components in human subjects [3][4][5][6][7][8] and in engineered cartilage constructs. [9][10][11][12][13][14] These latter techniques may be particularly useful for tailoring therapeutic interventions after implantation into a defect.…”

“…The applicability of this technique has been demonstrated to extend to tissueengineered cartilage constructs as well. 9 However, the utility of the MRI-based noninvasive GAG measurement remains unvalidated in hydrogel systems suitable for implantation into cartilage defects. Accordingly, we assessed the ability of Gd-based MRI measurements to determine the FCD of cartilage developing within an injectable substrate for cartilage growth.…”

Magnetization Transfer Imaging Provides a Quantitative Measure of Chondrogenic Differentiation and Tissue Development

“…Therefore, changes in the absolute or relative amounts of CG and PG in different layers of cartilage or in each layer with time can be expected to reflect the biochemical and biomechanical status of engineered cartilage. Over the past decade, MRI has been increasingly used to monitor tissue-engineered constructs, [11][12][13][14][15][16][17] with a great deal of research directed at correlating the CG and PG content with the T 1 and T 2 relaxation times, 18 the apparent diffusion coefficient (ADC), 18 the fixed charge density, 15,19 and the MTR. 3,18 However, to our knowledge, there has not yet been a report applying the qMTI technique to assess the early growth and development of tissueengineered cartilage.…”