CXCL12/CXCR4 Axis Regulates Aggrecanase Activation and Cartilage Degradation in a Post-Traumatic Osteoarthritis Rat Model.

Weiwei Lu,Jia Shi,Jinming Zhang,Fengjing Guo,Hui Huang,Zhengtao Lv,Anmin Chen,Wentao Zhu

doi:10.3390/ijms17101522

Abstract

We evaluated the role of the CXCL12/CXCR4 (C-X-C motif chemokine ligand 12/C-X-C chemokine receptor type 4) axis in aggrecanase-mediated cartilage degradation, and explored the underlying mechanism in a post-traumatic osteoarthritis rat model. Expression of CXCL12/CXCR4 and ADAMTS-5 was analyzed in the knees of osteoarthritic and non-arthritic rats using Western blot, ELISA, immunohistochemistry and immunofluorescence. Rodent studies were performed using Sprague-Dawley rats, with animals divided into three groups: Destabilization of the medial meniscus/AMD3100-treated (DMM/AMD3100-treated), DMM/PBS-treated, and sham controls. Rats were sacrificed after eight weeks, and samples were collected for histology and immunohistochemistry analyses. IL-1-pretreated primary chondrocytes were cultured with untreated control, CXCL12a, siNC + CXCL12a, or siRNA CXCR4 + CXCL12a, and analyzed for expression of relevant markers and cellular pathways. Higher levels of CXCL12 were detected in the knee fluid of osteoarthritic subjects, with strong staining for CXCR4 in chondrocytes and CXCL12 in synoviocytes together with enhanced expression of ADAMTS-5. DMM/AMD3100-treated rats showed a significantly reduced immunological response, with minimal evidence of pathology in both histological and immunohistochemical analyses. Treatment with CXCL12a increased the expression of ACAN, RUNX-2, and ADAMTS-4/5 in IL-1-pretreated primary chondrocytes, together with a decrease in the expression of SOX-9. Molecular analyses revealed strong induction of NF-κB activation, along with phosphorylation of MAPKs, and activation of canonical Wnt/β-catenin signaling. In conclusion, inhibition of SDF-1α/CXCR4 signaling axis was able to inhibit aggrecanase expression and lessen cartilage degeneration in post-traumatic osteoarthritis rats.

Highlights

Osteoarthritis (OA) is the most common form of arthritis and a major cause of pain and disability in older adults, afflicting over 15% of the Western elderly population [1]
Western blotting revealed significant increases in the expression of ADAMTS-5 and CXCR4 proteins in OA samples, relative to controls (Figure 1a), with elevated CXCL12 levels detected in the synovial fluid of OA subjects (Figure 1b)
We found that the expressions of both CXCL12 and CXCR4 were increased in the context of OA, accompanied by stronger expression of ADAMTS-5, implying a strong correlation between the CXCL12/CXCR4 axis and aggrecanase-activated cartilage loss (Figure 1)

Summary

Introduction

Osteoarthritis (OA) is the most common form of arthritis and a major cause of pain and disability in older adults, afflicting over 15% of the Western elderly population [1]. Degradation of the articular cartilage is cardinal to OA pathogenesis, but other joint tissues are constantly affected. Lesions in ligaments and menisci develop at the same time as cartilage lesions [4]. Much of this cartilage destruction appears to be a result of extracellular matrix loss mediated by uncontrolled production of matrix-degrading enzymes [5]. Type II collagen is present as triple helical fibrils that provide cartilage with its structure and tensile strength, while multiple aggrecan monomers bind to hyaluronan and link proteins to form huge aggregates that fill in the interstices of the collagen network, providing compressibility and elasticity

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Results

Conclusion