Biotribological Tests of Osteochondral Grafts after Treatment with Pro-Inflammatory Cytokines.

Christoph Bauer,Vivek Jeyakumar,Eugenia Niculescu-Morzsa,Hakan Göçerler,Thomas Klestil,Friedrich Franek,Christoph Stotter,Stefan Nehrer

doi:10.1177/1947603521994900

Christoph Bauer, Vivek Jeyakumar + Show 6 more

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https://doi.org/10.1177/1947603521994900

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Abstract

ObjectiveDuring osteoarthritis progression, cartilage degrades in a manner that influences its biomechanical and biotribological properties, while chondrocytes reduce the synthesis of extracellular matrix components and become apoptotic. This study investigates the effects of inflammation on cartilage under biomechanical stress using biotribological tests.MethodsBovine osteochondral grafts from five animals were punched out from the medial condyle and treated with or without pro-inflammatory cytokines (interleukin-1β [IL-1β], tumor necrosis factor-α [TNF-α], IL-6) for 2 weeks. After incubation, biotribological tests were performed for 2 hours (alternating 10 minutes test and pause respectively at 39°C, 180 N, 1 Hz, and 2 mm stroke). Before and after testing, the cartilage surface was imaged with a 3-dimensional microscope. During testing, the coefficient of friction (COF) was measured, while gene expression analysis and investigation of metabolic activity of chondrocytes were carried out after testing. Histological sections of the tissue and wear debris from the test fluid were also analyzed.ResultsAfter biotribological tests, surface cracks were found in both treated and untreated osteochondral grafts. In treated grafts, the COF increased, and the proteoglycan content in the cartilage tissue decreased, leading to structural changes. Chondrocytes from treated grafts showed increased expression of genes encoding for degradative enzymes, while cartilage-specific gene expression and metabolic activity exhibited no significant differences between treated and untreated groups. No measurable difference in the wear debris in the test fluid was found.ConclusionsTreatment of osteochondral grafts with cytokines results in a significantly increased COF, while also leading to significant changes in cartilage proteoglycan content and cartilage matrix compression during biotribological tests.

Highlights

Osteoarthritis (OA) is one of the most common degenerative joint diseases worldwide, and frequently affects the hands and weightbearing joints of the body.[1,2] Etiological causes of the disease are diverse
The metabolic activity of chondrocytes in osteochondral grafts showed no differences between the untested groups
The occurrence of pro-inflammatory cytokines led to a significantly increased expression of matrix metalloproteinase-1 (MMP1) in the untested and tested group compared with both control groups, where levels were near the detection limit

Summary

Introduction

Osteoarthritis (OA) is one of the most common degenerative joint diseases worldwide, and frequently affects the hands and weightbearing joints of the body.[1,2] Etiological causes of the disease are diverse. Most common are biochemical imbalances between anabolic and catabolic factors as well as progressive surface degradation caused by mechanical stress.[3] The pathogenesis of OA leads to the formation of osteophytes, remodeling of the subchondral bone, and inflammation in the joint.[4,5] This inflammation is characterized by the release of pro-inflammatory cytokines such as interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and IL-6 as well as proteolytic mediators like matrix metalloproteinases (MMPs).[6,7,8] All these factors lead to an imbalance in metabolic homeostasis of the cartilage tissue followed by degradation and alteration of the synovial fluid. The biomechanical and biotribological properties of the joint are influenced,[9,10] which can lead to chondrocyte apoptosis and reduced synthesis of important components of the extracellular matrix (ECM)

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