Background Mitochondrial dysfunction is well documented in OA and has the capacity to promote abnormalities in chondrocyte function and viability contributing to cartilage degeneration. Previous studies have showed the mtDNA haplogroup J are associated with incidence and progression of OA. Cybrids are optimal cellular models to study the real mitochondrial biology and function implications in the cellular behaviour, since they carry different mitochondrial variants with the same nuclear background, therefore, excluding the variations because of nuclear genome.
Objectives The aim of this work is to test the real role of mtDNA in cellular activity, using cybrids with mtDNA from healthy donors (without OA) and from patients with knee OA.
Methods Cybrids were developed using 143B.TK- Rho-0 cell line (nuclear donor) and platelets (mitochondrial donors) from healthy (without AO-N-) and knee OA donors. The OXPHOS function was evaluated by SeaHorse XFp after addition of oligomycin, FCCP and Rotenone/Antimycin A. The metabolic status was evaluated by glucose consumption and lactic acid production. The glycolytic activity was measure after addition of glucose, oligomycin and 2-dioxyglucose using Seahorse XFp. Appropriate statistical analyses were performed with GraphPad Prism v6.
Results OA cybrids had lower basal respiration (92.07±39.9 and 155.5±54.08, p<0.0005), and maximal respiratory capacity (114.7±50.1 and 160.6±44.7, p<0.05) than N. The analysis of ATP production was lower in OA than in N cybrids (66.69±28.69 versus 101.5±42.04 p≤0.05). The % spare respiratory capacity value for the N was significantly lower than in OA cybrids (107±16.21 versus 124.7±5.97, p≤0.0005). Cybrids carrying the mtDNA from OA patients showed higher glucose consumption than N cybrids (43.77±8.87 mg/ml and 31.91±13.69 mg/ml; p<0.05) however in the lactic acid production did not exit differences. The glycolytic activity was evaluated and showed that OA cybrids had lower glycolysis (71.05±4.83 versus 85.43±11.18, p<0.05) but higher glycolytic reserve than N cybrids (56.60±7.5 versus 39.73±19.13, p≤0.05).
Conclusions Cybrids have different metabolic behaviour, being N more efficient using glucose via glycolysis. We found differences statistical significate in the parameters that describe the mitochondrial respiration capacity, in this line OA cybrids had lower mitochondrial respiration and produce less ATP than the cybrids obtained from healthy patients. These results showed that the mitochondria obtained from healthy and OA donors had a different behaviour. These data also offer a real rationale for why mitochondria alterations play an important role in the incidence of OA.
Disclosure of Interest None declared
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