An aggrecan fragment drives osteoarthritis pain through Toll-like receptor 2
Rachel E. Miller, … , Amanda J. Fosang, Anne-Marie Malfait
Rachel E. Miller, … , Amanda J. Fosang, Anne-Marie Malfait
Published March 22, 2018
Citation Information: JCI Insight. 2018;3(6):e95704. https://doi.org/10.1172/jci.insight.95704.
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Research Article Bone biology Neuroscience

An aggrecan fragment drives osteoarthritis pain through Toll-like receptor 2

Abstract

Pain is the predominant symptom of osteoarthritis, but the connection between joint damage and the genesis of pain is not well understood. Loss of articular cartilage is a hallmark of osteoarthritis, and it occurs through enzymatic degradation of aggrecan by cleavage mediated by a disintegrin and metalloproteinase with thrombospondin motif 4 (ADAMTS-4) or ADAMTS-5 in the interglobular domain (E373–374A). Further cleavage by MMPs (N341–342F) releases a 32-amino-acid aggrecan fragment (32-mer). We investigated the role of this 32-mer in driving joint pain. We found that the 32-mer excites dorsal root ganglion nociceptive neurons, both in culture and in intact explants. Treatment of cultured sensory neurons with the 32-mer induced expression of the proalgesic chemokine CCL2. These effects were mediated through TLR2, which we demonstrated was expressed by nociceptive neurons. In addition, intra-articular injection of the 32-mer fragment provoked knee hyperalgesia in WT but not Tlr2-null mice. Blocking the production or action of the 32-mer in transgenic mice prevented the development of knee hyperalgesia in a murine model of osteoarthritis. These findings suggest that the aggrecan 32-mer fragment directly activates TLR2 on joint nociceptors and is an important mediator of the development of osteoarthritis-associated joint pain.

Authors

Rachel E. Miller, Shingo Ishihara, Phuong B. Tran, Suzanne B. Golub, Karena Last, Richard J. Miller, Amanda J. Fosang, Anne-Marie Malfait

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Figure 1

The 32-mer upregulates CCL2 protein production through TLR2 in cultured dorsal root ganglion (DRG) cells.

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The 32-mer upregulates CCL2 protein production through TLR2 in cultured ...
(A) WT DRG cells were stimulated with 0–30 μM synthetic 32-mer or scrambled peptide. Repeated 0 vs. 3 μM synthetic 32-mer in 4 independent cultures. (B) WT DRG cells were stimulated with 10 μM synthetic or native porcine 32-mer in the presence of 30 μg/ml polymyxin-B. Representative of two independent experiments. (C) Tlr4–/– DRG cells were stimulated with 0 vs. 3 μM synthetic 32-mer. Representative of three independent experiments. (D) Tlr2–/– DRG cells were stimulated with 0 vs. 3 μM synthetic 32-mer. Representative of 3 independent experiments. (E) WT DRG cells were stimulated with 0 vs. 1 μg/ml synthetic TLR2 ligand Pam3CSK4. Representative of 3 independent experiments. (F) Tlr2–/– DRG cells were stimulated with 0 vs. 1 μg/ml synthetic TLR2 ligand Pam3CSK4. Representative of two independent experiments. For A and B: 1-way ANOVA with Bonferroni’s post hoc tests; for C–F: unpaired 2-tailed Student’s t tests assuming equal variances; for A–F: **P < 0.01, ****P < 0.0001; mean ± SEM.