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NC STATE UNIVERSITY
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Orthopaedic Biomaterials Group
| Faculty Leader | Mansoor Haider |
| Postdoctoral Fellow | |
| Graduate Students |
Brandy Benedict |
| Undergraduate Students |
Jeff Olander |
1. Modeling the dynamic mechanical environment of cells in articular cartilage
Cyclic loading of articular cartilage results in a complex microscale biomechanical environment that affects cellular metabolic activity. Cartilage cells (chondrocytes) are sparsely distributed throughout the extracellular matrix (ECM) and are encapsulated by a pericellular matrix (PCM) that is rich in a distinct type of collagen [left]. A multiscale axisymmetric finite element model [middle] was developed for simulating biphasic fluid-solid mechanical interactions in a 3-zone domain subjected to confined compressive loading at varying frequencies. The model was used to conduct a parametric analysis evaluating the dual role of the PCM as both a protective and a transmissive layer around the cell. The protective role of the PCM is illustrated via a plot of traction normal to the cell at a loading frequency of 0.01Hz [right].
Reference: E Kim, F Guilak and MA Haider (to appear) The dynamic mechanical environment of the chondrocyte: A biphasic finite element model of cell-matrix interactions under cyclic compressive loading, Journal of Biomechanical Engineering.
[Experimental image courtesy of F. Guilak, Dept. of Surgery, Duke University Medical Center.]
Cyclic loading of articular cartilage results in a complex microscale biomechanical environment that affects cellular metabolic activity. Cartilage cells (chondrocytes) are sparsely distributed throughout the extracellular matrix (ECM) and are encapsulated by a pericellular matrix (PCM) that is rich in a distinct type of collagen [left]. A multiscale axisymmetric finite element model [middle] was developed for simulating biphasic fluid-solid mechanical interactions in a 3-zone domain subjected to confined compressive loading at varying frequencies. The model was used to conduct a parametric analysis evaluating the dual role of the PCM as both a protective and a transmissive layer around the cell. The protective role of the PCM is illustrated via a plot of traction normal to the cell at a loading frequency of 0.01Hz [right].
Reference: E Kim, F Guilak and MA Haider (to appear) The dynamic mechanical environment of the chondrocyte: A biphasic finite element model of cell-matrix interactions under cyclic compressive loading, Journal of Biomechanical Engineering.
[Experimental image courtesy of F. Guilak, Dept. of Surgery, Duke University Medical Center.]
A mathematical model and numerical solutions were developed for an interface problem that models an in vitro experiment for regeneration of articular cartilage in a localized defect region. In this experiment, a cylindrical tissue explant has a core region removed and replaced with a nutrient-rich hydrogel material [left]. The gel-tissue aggregate is immersed in nutrient-rich media for several weeks. An axisymmetric reaction-diffusion model of this experiment was developed to capture coupling between cell-mediated nutrient absorption and matrix biosynthesis, and diffusive transport of nutrients and matrix constituents. The reaction at the gel-tissue interface was modeled via a level set method and potential effects of local interface curvature were also considered. A parametric analysis was conducted to simulate tissue regeneration times required to completely degrade the hydrogel. Advancement of the gel-tissue interface [right] as the hydrogel degrades is governed by coupled effects of spatial gradients in non-dimensional nutrient concentration [middle] and the local reaction along the gel-tissue interface.
Reference: SD Olson and MA Haider (in review) A level set reaction-diffusion model for tissue regeneration in a cartilage-hydrogel aggregate.
[preprint available upon request]