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Osteoarthritis Cartilage. 2018 Mar;26(3):414-421. doi: 10.1016/j.joca.2018.01.001. Epub 2018 Jan 8.

Functional effects of an interpenetrating polymer network on articular cartilage mechanical properties.

Author information

1
Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
2
Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA; Department of Chemistry, Boston University, Boston, MA, USA.
3
Department of Applied Physics, University of Eastern Finland, Kuopio, Finland; Diagnostic Imaging Center, Kuopio University Hospital, Kuopio, Finland.
4
Department of Chemistry, Boston University, Boston, MA, USA; Department of Biomedical Engineering, Boston University, Boston, MA, USA; Department of Medicine, Boston University, Boston, MA, USA. Electronic address: mgrin@bu.edu.
5
Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA; Department of Orthopaedic Surgery, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA. Electronic address: Brian.Snyder@childrens.harvard.edu.

Abstract

OBJECTIVE:

Depletion of glycosaminoglycans (GAGs) and degradation of collagen network are early hallmarks of osteoarthritis (OA). Currently, there are no chondroprotective therapies that mitigate the loss of GAGs or effectively restore the collagen network. Recently, a novel polymeric cartilage supplement was described that forms a charged interpenetrating polymer network (IPN) reconstituting the hydrophilic properties of the extracellular matrix (ECM). To investigate the mechanism by which this hydrophilic IPN improves articular cartilage material properties, a finite element (FE) model is used to evaluate the IPN's effect on the fibrillar collagen network, nonfibrillar matrix, and interstitial fluid flow.

METHODS:

Bovine osteochondral plugs were degraded with chondroitinase ABC to selectively decrease GAG content. Samples were mechanically tested before and after IPN treatment using unconfined testing geometry and stress-relaxation protocol. Every measurement was modeled separately using a fibril-reinforced poroviscoelastic FE model. Measurement replication was achieved by optimizing the following model parameters: initial and strain-dependent fibril network modulus (Ef0, Efε, respectively), nonfibrillar matrix modulus (Enf), initial permeability (k0) and strain-dependent permeability factor (M).

RESULTS:

Based on the FE model results, treatment of native and GAG depleted cartilage with the hydrophilic IPN increases the ECM stiffness and impedes fluid flow. The IPN did not alter the stiffness of fibrillary network. Cartilage permeability and the strain-dependent permeability factor decreased with increasing IPN w/v%.

CONCLUSIONS:

The IPN reconstitutes cartilage material properties primarily by augmenting the hydrophilic ECM. This reinforcement of the solid phase also affects the fluid phase reestablishing low permeability.

KEYWORDS:

Articular cartilage; Biomaterials; Biomechanics; Finite element analysis; Osteoarthritis

PMID:
29326062
DOI:
10.1016/j.joca.2018.01.001

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