Differential proteome analysis of normal and osteoarthritic chondrocytes reveals distortion of vimentin network in osteoarthritis.

OBJECTIVE: We conducted a proteome analysis of human articular chondrocytes, in order to identify proteins differentially expressed in chondrocytes during the progression of osteoarthritis (OA) and to characterize the phosphorylation status of these proteins.
METHODS: The proteins of 20 samples of human chondrocytes obtained from the cartilage of human knees (six from healthy cartilage (NoNo), seven from visually intact zones (NoOA) and seven from visually damaged zones (OAOA) of OA cartilage from the same knee joint) were sequentially extracted and subjected to two-dimensional gel electrophoresis (2-DE). Protein expression patterns were subjected to statistical analysis and protein spots of interest were identified by electrospray ionization tandem mass spectrometry.
RESULTS: We identified several protein spots, showing a differential expression between the sample groups. Cleaved vimentin was upregulated in OAOA samples, this was confirmed by 1-DE and Western blot. The possible impact of vimentin cleavage on the chondrocyte's cytoskeleton was illustrated by confocal microscopy analysis, which revealed a distorted vimentin organization in OA chondrocytes. In contrast, F-actin staining did not reveal differences.
CONCLUSION: All together, this study revealed substantial alterations in the vimentin cytoskeleton in OA-affected human articular chondrocytes.