Down-modulation of chemokine receptor cartilage expression in inflammatory arthritis

Objective. To evaluate in vivo expression of chemokine receptors in cartilage tissue samples from healthy and diseased joints. Methods. Presence and distribution of several chemokine receptors in cartilage samples from patients with osteoarthritis (OA) or inflammatory arthritis (IA) and from multi-organ donors were assessed by immunohistochemistry. The expression of messenger RNA (mRNA) for chemokine receptors was also analysed by reverse transcriptase-polymerase chain reaction (RT-PCR). Results. Normal and OA-affected cartilage showed a moderate to high expression of chemokine receptors, while staining of IA samples ranged from low to absent. Differences between OA and IA samples were present for all receptors but CCR2 and CXCR4. Moreover, mRNAs for CCR1, CCR5 and CXCR1 were found both in normal and pathological chondrocytes, suggesting that chemokine receptor down-modulation seen in IA samples could be a post-transcriptional event. Conclusion. Data on normal and pathological chondrocytes underline the role of chemokines in cartilage homeostasis and suggest an imbalance towards catabolic processes in inflammatory conditions.