Objective: It has been suggested that oxidized low-density lipoprotein (ox-LDL) has some roles in progression of osteoarthritis. The purpose of this study is to investigate whether ox-LDL binding to lectin-like ox-LDL receptor 1 (LOX-1) enhances monocyte chemoattractant protein I (MCP-1) expression in cultured human articular chondrocytes (HACs).Method. The time course and dose response of MCP-1 mRNA expression and MCP-1 protein release into medium following ox-LDL stimulation were investigated using quantitative Real time PCR (delta-delta Ct method) and enzyme-linked immunosorbent assay (ELISA), respectively. To examine the receptor specificity of ox-LDL action, HACs were preincubated with anti-human LOX-1 monoclonal antibody (TS92).Results: A time-course study revealed that MCP-1 mRNA expression increased 5.09 +/- 0.86 fold 12 h after ox-LDL stimulation compared to time-0. ox-LDL stimulation increased MCP-1 protein level in conditioned medium in a time-dependent manner. Increased MCP-1 level was evident 6 h after stimulation, reaching 830 +/- 91 pg/ml at 24 h (33 +/- 8 pg/ml at time-0). Dose responses of MCP-1 expression were also evident in mRNA and protein levels. Pretreatment with TS92 markedly suppressed these stimulating effects of ox-LDL, although that with non-specific IgG did not. Native LDL did not affect MCP-1 expression.Conclusion: Our results suggest that ox-LDL enhances MCP-1 expression in HACs and supports the hypothesis that ox-LDL is involved in cartilage degeneration. (C) 2008 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Presentationsdemonstrate cartilage destructive properties as expressed by an increased release and a decreased synthesis rate and content of cartilage proteoglycans.The synovial tissue destructive properties increase with time after the experimental haemorrhage (+168%/+260%; -76%/-83%; -18%/-32% respectively, for 24/48 hours).Conclusions: Although intra-articular blood is cleared within 2 days from the canine knee joint (<10% left), adverse effects on cartilage and synovium are already initiated within 1 day, and they are more severe 2 days after the experimental haemorrhage.Although these are only short-term effects in the canine joint, it is clear that only a small amount of blood in a joint for a short period of time can result in a condition significantly compromising the joint.

Objective: Using human cartilage samples and cultured chondrocytes, to assess the possible involvement of oxidized low-density lipoprotein (ox-LDL) and lectin-like ox-LDL receptor-1 (LOX-1) in pathogenesis and progression of osteoarthritis (OA).Methods: Thirty-two cartilage samples were obtained from 16 patients with knee OA, and 12 Control samples from six with femoral neck fracture. LOX-1 mRNA expressions in 12 OA and six Control samples were analyzed by reverse transcription-polymerase chain reaction (RTPCR). Immunohistochemistry for ox-LDL and LOX-1 was performed in all samples. The histological CA grade was assessed with the modified Mankin score. The relative percentage of the ox-LDL and LOX-1 immunopositive chondrocytes was calculated in all samples. The effects of ox-LDL on cell viability in cultured human chondrocytes were 5 investigated by the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay and on proteoglycan synthesis by monitoring [S-35] sulfate incorporation.Results: There was a statistically significant difference between mean LOX-1/GAPDH (LOX-1/human glyceralclehyde-3-phosphate dehydrogenase) ratio of OA samples and that of Control samples (40.6% +/- 10.3 and 11.9% +/- 2.8, respectively, P < 0.0001). The mean percentage of ox-LDL-positive cells was 23.0 +/- 15.7% in OA and 4.3 +/- 3.7% in Control cells (P = 0.0002). The mean percentage of LOX-1-positive cells was 51.7 +/- 29.5% in OA and 10.0 +/- 8.1% in Control cells (P < 0.0001). Both the ox-LDL immunoreactivity and the LOX-1 immunoreactivity were significantly correlated with the modified Mankin scores (R-2 = 0.67 and 0.48, respectively; P < 0.0001 for each). ox-LDL significantly reduced the human chondrocyte viability and proteoglycan synthesis, and pretreatment with anti-human LOX-1 monoclonal antibody reversed these effects.Conclusion: The ox-LDL/LOX-1 system may be involved in human OA. (C) 2006 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.