scholarly journals An in silico Framework of Cartilage Degeneration That Integrates Fibril Reorientation and Degradation Along With Altered Hydration and Fixed Charge Density Loss

Author(s):  
Seyed Ali Elahi ◽  
Petri Tanska ◽  
Rami K. Korhonen ◽  
Rik Lories ◽  
Nele Famaey ◽  
...  

Injurious mechanical loading of articular cartilage and associated lesions compromise the mechanical and structural integrity of joints and contribute to the onset and progression of cartilage degeneration leading to osteoarthritis (OA). Despite extensive in vitro and in vivo research, it remains unclear how the changes in cartilage composition and structure that occur during cartilage degeneration after injury, interact. Recently, in silico techniques provide a unique integrated platform to investigate the causal mechanisms by which the local mechanical environment of injured cartilage drives cartilage degeneration. Here, we introduce a novel integrated Cartilage Adaptive REorientation Degeneration (CARED) algorithm to predict the interaction between degenerative variations in main cartilage constituents, namely collagen fibril disorganization and degradation, proteoglycan (PG) loss, and change in water content. The algorithm iteratively interacts with a finite element (FE) model of a cartilage explant, with and without variable depth to full-thickness defects. In these FE models, intact and injured explants were subjected to normal (2 MPa unconfined compression in 0.1 s) and injurious mechanical loading (4 MPa unconfined compression in 0.1 s). Depending on the mechanical response of the FE model, the collagen fibril orientation and density, PG and water content were iteratively updated. In the CARED model, fixed charge density (FCD) loss and increased water content were related to decrease in PG content. Our model predictions were consistent with earlier experimental studies. In the intact explant model, minimal degenerative changes were observed under normal loading, while the injurious loading caused a reorientation of collagen fibrils toward the direction perpendicular to the surface, intense collagen degradation at the surface, and intense PG loss in the superficial and middle zones. In the injured explant models, normal loading induced intense collagen degradation, collagen reorientation, and PG depletion both on the surface and around the lesion. Our results confirm that the cartilage lesion depth is a crucial parameter affecting tissue degeneration, even under physiological loading conditions. The results suggest that potential fibril reorientation might prevent or slow down fibril degradation under conditions in which the tissue mechanical homeostasis is perturbed like the presence of defects or injurious loading.

Author(s):  
Chun-Yuh Huang ◽  
Wei Yong Gu

Poor nutritional supply has been a major concern for the health of intervertebral disc (IVD) since the IVD is the largest avascular tissue in the human body. The transport of vital nutrients to cells relies on diffusion and convection through the extracellular matrix (ECM) in the IVD. Transport and metabolism of nutrients (e.g., oxygen and glucose) within the IVD depend on many factors, including the material properties of ECM (e.g., permeability, elastic modulus, and solute diffusivity), cellular metabolic rates, nutritional supply at the edge of the IVD, and mechanical loading [1–6]. Tissue degeneration alters the material properties of the IVD, such as an increase in elastic modulus and a decrease in water content, fixed charge density, permeability and solute diffusivity [6]. However, the effect of tissue degeneration on transport and metabolism of nutrients in the IVD under mechanical loading has not been elucidated. The objective of this study was to numerically investigate the distribution of glucose, oxygen and lactate in the degenerated IVD under static unconfined compression using the mechano-electrochemical mixture theory [7].


2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Petri Tanska ◽  
Siru M. Turunen ◽  
Sang Kuy Han ◽  
Petro Julkunen ◽  
Walter Herzog ◽  
...  

The aim of this study was to investigate if the experimentally detected altered chondrocyte volumetric behavior in early osteoarthritis can be explained by changes in the extracellular and pericellular matrix properties of cartilage. Based on our own experimental tests and the literature, the structural and mechanical parameters for normal and osteoarthritic cartilage were implemented into a multiscale fibril-reinforced poroelastic swelling model. Model simulations were compared with experimentally observed cell volume changes in mechanically loaded cartilage, obtained from anterior cruciate ligament transected rabbit knees. We found that the cell volume increased by 7% in the osteoarthritic cartilage model following mechanical loading of the tissue. In contrast, the cell volume decreased by 4% in normal cartilage model. These findings were consistent with the experimental results. Increased local transversal tissue strain due to the reduced collagen fibril stiffness accompanied with the reduced fixed charge density of the pericellular matrix could increase the cell volume up to 12%. These findings suggest that the increase in the cell volume in mechanically loaded osteoarthritic cartilage is primarily explained by the reduction in the pericellular fixed charge density, while the superficial collagen fibril stiffness is suggested to contribute secondarily to the cell volume behavior.


2002 ◽  
Vol 47 (2) ◽  
pp. 284-291 ◽  
Author(s):  
Erik M. Shapiro ◽  
Arijitt Borthakur ◽  
Alexander Gougoutas ◽  
Ravinder Reddy

2002 ◽  
pp. 387-395
Author(s):  
Robert J. Wilkins ◽  
Bethan Hopewell ◽  
Jill P. G. Urban

Author(s):  
Phong Phan ◽  
Anh Vo ◽  
Amirhamed Bakhtiarydavijani ◽  
Reuben Burch ◽  
Brian K. Smith ◽  
...  

Abstract Computational approaches, especially Finite Element Analysis (FEA), have been rapidly growing in both academia and industry during the last few decades. FEA serves as a powerful and efficient approach for simulating real-life experiments, including industrial product development, machine design, and biomedical research, particularly in biomechanics and biomaterials. Accordingly, FEA has been a "go-to" high biofidelic software tool to simulate and quantify the biomechanics of the foot-ankle complex, as well as to predict the risk of foot and ankle injuries, which are one of the most common musculoskeletal injuries among physically active individuals. This paper provides a review of the in silico FEA of the foot-ankle complex. First, a brief history of computational modeling methods and Finite Element (FE) simulations for foot-ankle models is introduced. Second, a general approach to build a FE foot and ankle model is presented, including a detailed procedure to accurately construct, calibrate, verify, and validate a FE model in its appropriate simulation environment. Third, current applications, as well as future improvements of the foot and ankle FE models, especially in the biomedical field, are discussed. Lastly, a conclusion is made on the efficiency and development of FEA as a computational approach in investigating the biomechanics of the foot-ankle complex. Overall, this review integrates insightful information for biomedical engineers, medical professionals, and researchers to conduct more accurate research on the foot-ankle FE models in the future.


1988 ◽  
Vol 254 (3) ◽  
pp. F364-F373 ◽  
Author(s):  
M. Wolgast ◽  
G. Ojteg

In the classical Starling model the hydrostatic pressure in the pores is generally lower than that in capillary plasma, a phenomenon that necessitates the assumption of a rigid porous membrane. In flexible gel membranes, the capillary pressure is suggested to be balanced by a gel swelling pressure generated by negative fixed charges. Regarding the fluid transfer, the transmembranous electrical potential gradient will generate a net driving electroosmotic force. This force will be numerically similar to the net driving Starling force in small pores, but distinctly different in large pores. From previous data on the hydrostatic and colloid osmotic forces, the fixed charge density at the two interfaces of 1) the glomerular and 2) the peritubular capillary membrane were calculated and used to predict the flux of a series of charged protein probes. The close fit to the experimental data in both the capillary beds is in line with the gel concept presented. The gel concept (but hardly a rigid membrane) explains the ability of capillary membranes to alter their permeability in response to external forces. Gel membranes can furthermore be predicted to have a self-rinsing ability, as entrapped proteins will increase the local fixed charge density, leading to fluid entry into the region between the particle and the pore rim, which by consequent widening of the channel will facilitate extrusion of trapped proteins.


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