Comparative assessment of intrinsic mechanical stimuli on knee cartilage and compressed agarose constructs

Abstract

A well-established cue for improving the properties of tissue-engineered cartilage is mechanical stimulation. However, the explicit ranges of mechanical stimuli that correspond to favorable metabolic outcomes are elusive. Usually, these outcomes have only been associated with the applied strain and frequency, an oversimplification that can hide the fundamental relationship between the intrinsic mechanical stimuli and the metabolic outcomes. This highlights two important key issues: the firstly is related to the evaluation of the intrinsic mechanical stimuli of native cartilage; the second, assuming that the intrinsic mechanical stimuli will be important, deals with the ability to replicate them on the tissue-engineered constructs. This study quantifies and compares the volume of cartilage and agarose subjected to a given magnitude range of each intrinsic mechanical stimulus, through a numerical simulation of a patient-specific knee model coupled with experimental data of contact during the stance phase of gait, and agarose constructs under direct-dynamic compression. The results suggest that direct compression loading needs to be parameterized with time-dependence during the initial culture period in order to better reproduce each one of the intrinsic mechanical stimuli developed in the patient-specific cartilage. A loading regime which combines time periods of low compressive strain (5%) and frequency (0.5Hz), in order to approach the maximal principal strain and fluid velocity stimulus of the patient-specific cartilage, with time periods of high compressive strain (20%) and frequency (3Hz), in order to approach the pore pressure values, may be advantageous relatively to a single loading regime throughout the full culture period.

Computational technology for nasal cartilage-related clinical research and application

“…Mimics (Materialise, USA), Ansys Workbench (ANSYS, USA) 42 and FEBio (The University of Utah, USA) 45 have been used for mesh generation and preprocessing in nasal cartilage and nasal-related research. Hypermesh (Altair Engineering, USA), 46 Trelis (Csimsoft, USA) 47 and CATIA (Dassault, USA) 48 have been used for other kinds of cartilage in mesh generation and preprocessing and can also be applied to nasal cartilage. In addition to its convenient model reconstruction function, Mimics has certain advantages in surface 3D meshing.…”

Utilization of Finite Element Analysis for Articular Cartilage Tissue Engineering

“…To mimic the physiological environment of cartilage, computational models should include solid and fluid phases with an assigned fluid volume ratio or a void ratio (i.e., porosity) and permeability. Multiple groups have demonstrated the utility of biphasic solid-fluid and poroelastic cartilage scaffolds models [17,26,28,31]. The matrix is defined either as a linear elastic [27,31] or non-linear elastic isotropic material [26].…”

“…Multiple groups have demonstrated the utility of biphasic solid-fluid and poroelastic cartilage scaffolds models [17,26,28,31]. The matrix is defined either as a linear elastic [27,31] or non-linear elastic isotropic material [26]. Linear elastic models were assigned Young’s modulus (E) and Poisson’s ratio (v) to the solid phase of the scaffold of: E = 34.99 kPa, v = 0.495 [27]; E = 133 kPa, v = 0.3 [31]; and E = 9.5 kPa, v = 0.3 [17].…”

“…The matrix is defined either as a linear elastic [27,31] or non-linear elastic isotropic material [26]. Linear elastic models were assigned Young’s modulus (E) and Poisson’s ratio (v) to the solid phase of the scaffold of: E = 34.99 kPa, v = 0.495 [27]; E = 133 kPa, v = 0.3 [31]; and E = 9.5 kPa, v = 0.3 [17]. Poro-elastic and biphasic models are assigned porosity, fluid permeability, solid bulk modulus, and fluid bulk modulus to simulate fluid-filled tissues.…”

“…The porosity value of a scaffold varies for each design and is usually input as void ratio in the equation. Void ratios of three (75% porous) [31] and four (80% porous) [28,32] have been assigned to scaffolds, though other values based on different designs can be found in the literature. Fluid permeability is either defined as a uniform value or deformation-dependent exponential function based on van der Voet’ formulation with initial permeability assigned to the solid matrix [31].…”