Effect of collagen-induced residual stress on the frictional property of articular cartilage

Previous findings,such as split-line of the articular cartilage surface and curving of sliced cartilage specimen,would suggest that residual stress is contained in articular cartilage.This study was performed to determine the effect of collagen fibre-induced residual stress on the biphasic lubrication property of articular cartilage.A fibre-reinforced poroelastic model of articular cartilage was developed in Abaqus.In the model,residual stress was contained in the collagen fibre in the surface layer by applying 1-5%of tensile strain.Reciprocating friction analysis was performed between the model and a sphere at a friction speed of 1.0-10.0 mm/s.Results revealed that the coefficients of start-up and dynamic friction at second friction cycle were lower in residual stress model than in no-residual stress model,with the largest decreases observed at a friction speed of 1 mm/s.It was obse rved that re hydration was promoted in the bearing area in residual stress model.These results suggest that collagen-induced residual stress plays an important role in enhancing the biphasic lubrication property of articular cartilage.

Influence of collagen fibre orientation on the frictional properties of articular cartilage

Articular cartilage has a unique collagen fibre network structure that exhibits both anisotropy and depth dependency.Collagen fibre orientation in a cross-section parallel to the articular cartilage surface may affect the lubrication properties of articular cartilage.The effect of collagen fibre orientation on the frictional properties of articular cartilage was examined through finite element analysis of the friction.Specifically,a three-dimensional fibre-reinforced poroelastic biphasic model was used to determine the influence of collagen fibril orientation on the frictional properties of articular cartilage.The simulations reveal that collagen fibre orientation has a significant influence on the deformation behaviour of articular cartilage in front of and behind the contact area.The coefficient of dynamic friction was lower in the direction parallel to the collagen fibre orientation than in the direction perpendicular to the collagen fibre orientation,regardless of the indenter speed.

Morphology and gene expression of sex‐determining region Y‐box 9 and runt‐related transcription factor 2 in centrifugally compressed cell collagen‐combined constructs (C^(6))

The authors previously developed a scaffold‐free tissue‐engineered construct(TEC)from mesenchymal stem cells(MSCs).Although the TEC exhibited even cell distribution and was successfully applied for cartilage repair in animal models,it is unsuitable for relatively large‐scale cartilage defects due to its small size.To solve the problem,the authors recently developed a novel biomaterial,a centrifugally compressed cell‐collagen combined construct(C^(6))from a mixture of MSCs and atelocollagen,both of which are subjected to centrifugation.The results of the previous study indicated that C^(6) exhibited high cell viability(70%)and sufficient cell distribution similar to that of the TEC.In the present study,the morphology and gene expression of C^(6) were investigated.Histological ex-amination indicated that C6 is six times thicker(approximately 1 mm)than the TEC after a 7‐day culture.The C^(6) remained unchanged in scale with increased cell density after a 21‐day culture.Scanning electron microscopic observation indicated that C^(6) exhibited interconnected and porous microstructures,while the TEC had close‐knit microstruc-tures.Reverse transcriptase‐polymerase chain reaction analysis indicated that the expression of sex‐determining region Y‐box 9 and runt‐related transcription factor 2 was significantly higher in C^(6) than that in TEC.