Functional and structural properties of human patellar articular cartilage in osteoarthritis

Mikko T Nissinen,Mikko J Nissi,Nina Hänninen,Mithilesh Prakash,Janne T.A Mäkelä,Juha Töyräs,Miika T Nieminen,Rami K Korhonen,Petri Tanska

doi:10.1016/j.jbiomech.2021.110634

Mikko T Nissinen, Mikko J Nissi + Show 7 more

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https://doi.org/10.1016/j.jbiomech.2021.110634

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Abstract

Changes in the fibril-reinforced poroelastic (FRPE) mechanical material parameters of human patellar cartilage at different stages of osteoarthritis (OA) are not known. Further, the patellofemoral joint loading is thought to include more sliding and shear compared to other knee joint locations, thus, the relations between structural and functional changes may differ in OA. Thus, our aim was to determine the patellar cartilage FRPE properties followed by associating them with the structure and composition. Osteochondral plugs (n = 14) were harvested from the patellae of six cadavers. Then, the FRPE material properties were determined, and those properties were associated with proteoglycan content, collagen fibril orientation angle, optical retardation (fibril parallelism), and the state of OA of the samples. The initial fibril network modulus and permeability strain-dependency factor were 72% and 63% smaller in advanced OA samples when compared to early OA samples. Further, we observed a negative association between the initial fibril network modulus and optical retardation (r = -0.537, p < 0.05). We also observed positive associations between 1) the initial permeability and optical retardation (r = 0.547, p < 0.05), and 2) the initial fibril network modulus and optical density (r = 0.670, p < 0.01).These results suggest that the reduced pretension of the collagen fibrils, as shown by the reduced initial fibril network modulus, is linked with the loss of proteoglycans and cartilage swelling in human patellofemoral OA. The characterization of these changes is important to improve the representativeness of knee joint models in tissue and cell scale.

Highlights

Osteoarthritis (OA) is a degenerative joint disease, which affects approximately 10% of men and 18% of women over 60 years old (GlynJones et al, 2015)
The initial fibril network modulus (E0f ), and permeability strain-dependency factor (M) were smaller in the advanced OA group compared to the early OA group
We observed that the initial fibril network modulus and permeability strain-dependency factor were on average 72% and 60% smaller in the advanced OA group compared to the early OA group

Summary

Introduction

Osteoarthritis (OA) is a degenerative joint disease, which affects approximately 10% of men and 18% of women over 60 years old (GlynJones et al, 2015). When OA progresses into an advanced state, the collagen content reduces, proteoglycan loss is extensive, and fluid fraction inside the tissue continues to increase. All these changes impair the tissue function exposing it to mechanical damage and wear (Buckwalter and Mankin, 1997; Cuc chiarini et al, 2016; Glyn-Jones et al, 2015; Knecht et al, 2006; MartelPelletier et al, 2008; Saarakkala et al, 2010). The mechanical contribution of each constituent – collagen, proteoglycans, and fluid – cannot be separated directly from experiments This can be done by computational modeling (e.g., finite element (FE) modeling) in which a constituent-specific material model is fitted to experimental mechanical testing data. One example of a constituent-specific material model is the fibril reinforced poroelastic (FRPE) model which is previously reported to capture successfully equilibrium, transient and dynamic mechanical behavior of cartilage (Fortin et al, 2000; Julkunen et al, 2013; Li et al, 2009)

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