Objective. Osteoarthritis (OA) is a degenerative rheumatic disease that is associated with extracellular matrix degradation and chondrocyte apoptosis in the articular cartilage. The role of mitochondria in degenerative diseases is widely recognized. We undertook this study to evaluate mitochondrial function in normal and OA chondrocytes and to examine age-related changes in mitochondria.Methods. Mitochondrial function was evaluated by analyzing respiratory chain enzyme complexes and citrate synthase (CS) activities as well as changes in mitochondrial membrane potential (⌬⌿m). The activities of mitochondrial respiratory chain complexes (complex I: rotenone-sensitive NADH-coenzyme Q 1 reductase; complex II: succinate dehydrogenase; complex III: antimycin-sensitive ubiquinol cytochrome c reductase; and complex IV: cytochrome c oxidase) and CS were measured in human articular chondrocytes isolated from OA and normal cartilage. ⌬⌿m was measured by JC-1 using flow cytometry. Statistical analysis was performed using the Mann-Whitney U test and Student's t-test as well as several models of multiple linear regression.Results. OA articular chondrocytes had reduced activities of complexes II and III compared with cells from normal cartilage. However, the mitochondrial mass was increased in OA. Cultures of OA chondrocytes contained a higher proportion of cells with de-energized mitochondria. We found no relationship between mitochondrial function and donor age either in normal or in OA chondrocytes. Conclusion. These findings suggest the involvement of mitochondrial function in the pathophysiology of OA. Cartilage degradation by OA and cartilage aging may be two different processes.Osteoarthritis (OA) is a degenerative joint disease that is characterized by articular cartilage degradation. The final phase of OA seems to reflect a failure of the reparative process, resulting in degradation of the matrix, cell death, and total loss of cartilage integrity. The chondrocyte is the only cell type that is present in mature cartilage, and it is responsible for repairing the damaged tissue (1,2).Mitochondria are complex organelles that oxidize a wide range of metabolic intermediates. It has been reported that in living cells, these organelles have a characteristic appearance that depends on the tissue type and the oxidative state of the cell. Multienzyme complexes located both in the inner mitochondrial membrane and in the mitochondrial matrix oxidize tricarboxylic acid-cycle intermediates derived from primary nutrients. ATP is generated by the activity of an electrogenic proton pump that spans the inner mitochondrial membrane. The energy for synthesis of ATP is derived from two components: a pH gradient and the electric potential across the mitochondrial membrane.Mitochondrial impairment and defective oxidative phosphorylation have been linked to some human disorders (3,4). Mitochondria are important in regulating cell survival (5-9), and the classic signs of cell death

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Objective: To investigate the effect of nitric oxide (NO) on mitochondrial activity and its relation with the apoptosis of human articular chondrocytes. Materials and methods: Mitochondrial function was evaluated by analysing respiratory chain enzyme complexes, citrate synthase (CS) activities, and mitochondrial membrane potential (Dym). The activities of the mitochondrial respiratory chain (MRC) complexes (complex I: NADH CoQ 1 reductase, complex II: succinate dehydrogenase, complex III: ubiquinol cytochrome c reductase, complex IV: cytochrome c oxidase) and CS were measured in human articular chondrocytes isolated from normal cartilage. The Dym was measured by 5,59,6,69-tetracholoro-1,19,3,39-tetraethylbenzimidazole carbocyanide iodide (JC-1) using flow cytometry. Apoptosis was analysed by flow cytometry. The mRNA expression of caspases was analysed by ribonuclease protection analysis and the detection of protein synthesis by western blotting. Sodium nitroprusside (SNP ) was used as an NO compound donor. Results: SNP at concentrations higher than 0.5 mmol/l for 24 hours induced cellular changes characteristic of apoptosis. SNP elicited mRNA expression of caspase-3 and caspase-7 and down regulated bcl-2 synthesis in a dose and time dependent manner. Furthermore, 0.5 mM SNP induced depolarisation of the mitochondrial membrane at 5, 12, and 24 hours. Analysis of the MRC showed that at 5 hours, 0.5 mM SNP reduced the activity of complex IV by 33%. The individual inhibition of mitochondrial complex IV with azide modified the Dym and induced apoptosis. Conclusions: This study suggests that the effect of NO on chondrocyte survival is mediated by its effect on complex IV of the MRC.

ObjectivesThe prognostic value of genetic studies in cardiomyopathies is still controversial. Our objective was to evaluate the outcome of patients with cardiomyopathy with mutations in the converter domain of β myosin heavy chain (MYH7).MethodsClinical characteristics and survival of 117 affected members with mutations in the converter domain of MYH7 were compared with 409 patients described in the literature with mutations in the same region.ResultsTwenty-five mutations were evaluated (9 in our families including 3 novel (Ile730Asn, Asp717Gly and Arg719Pro)). Clinical diagnoses were hypertrophic (n=407), dilated (n=15), non-compaction (n=4) and restrictive (n=5) cardiomyopathies, unspecified cardiomyopathy (n=11), sudden death (n=50) and 35 healthy carriers. One hundred eighty-four had events (cardiovascular death or transplant). Median event-free survival was 50±2 years in our patients and 53±3 years in the literature (p=0.27). There were significant differences in the outcome between mutation: Ile736Thr had fewer events than other mutations in the region (p=0.01), while Arg719Gln (p<0.01) had reduced event-free survival.ConclusionsMutations in the converter region are generally associated with adverse prognosis although there are differences between mutations. The identification of a mutation in this particular region provides important prognostic information that should be considered in the clinical management of affected patients.

Articular cartilage has only a limited ability to regenerate. The transplantation of autologous chondrocytes is currently used to treat focal defects in human articular cartilage, although use of organs, tissues, or cells from different species is being investigated as an alternative treatment. The object of this study was to use xeno-transplantation of cultured pig chondrocytes for the repair of rabbit chondral defects, and to analyze the significance of tissue rejection in this animal model. Partial chondral defects, including removal of cartilage tissue and a part of the subchondral bone, were created in the lateral femoral condyles of 30 adult New Zealand White rabbits. A periosteal flap was sutured to the native cartilage with the cambium layer facing the defect. As a control, culture medium was injected into the defect void of one group of rabbits while in a treatment group, chondrocytes, isolated from normal femoral pig cartilage, were injected into the defect void. All rabbits were killed by 24 weeks. Macroscopic changes of the cartilage were analyzed using Mankin's score. The distal femoral portion was studied histologically using hematoxylin and eosin, alcian blue, toluidine blue, and Mason's trichrome. Pig cells and pig genetic material were detected in the neo-synthesized tissue by immunohistochemical detection of SLA-II-DQ and polymerase chain reaction analysis of the gene SLA-II-DQB. The synovial membrane was studied histologically by hematoxylin and eosin staining. In the control group, on average, less than 25 percent of the chondral defect was filled. The repair tissue had an irregular surface with few cells similar to chondrocytes or fibroblasts and a minimal formation of extracellular matrix. In the treatment group, the chondral defect was approximately 90 percent filled with good integration between the neo-synthesized cartilage and the native cartilage. The repair tissue had a smooth surface with cells similar to chondrocytes and a hyaline-like extracellular matrix. The neo-synthesized cartilage was morphologically similar to hyaline cartilage. Importantly, there were no signs of graft-vs.-host rejections or infiltration by immune cells. In the neo-synthesized tissue, pig genetic material was detected in 27 +/- 5 percent of all cells. These cells containing pig genetic material were distributed throughout the neo-synthesized cartilage. We conclude that the xeno-transplantation of chondrocytes could be an alternative method for the repair of articular cartilage defects.