Proteomic analysis of articular cartilage vesicles from normal and osteoarthritic cartilage. Arthritis Rheum 2010 Oct 27:
Date
10/29/2010Pubmed ID
20981819Abstract
OBJECTIVES:: Articular cartilage vesicles (ACVs) are extracellular organelles found in normal articular cartilage. While they were initially defined by their ability to generate pathologic calcium crystals in osteoarthritic (OA) cartilage, they also can alter the phenotype of normal chondrocytes through transfer of RNA and protein. We analyzed the proteome of ACVs from normal and OA human cartilage. METHODS:: ACVs were isolated from 10 normal and 10 OA human knee cartilages. We identified the ACV proteomes using in-gel trypsin digestion, nanospray LC-MS/MS of tryptic peptides followed by searching an appropriate subset of the Uniprot database. We further identified a set of proteins that were significantly different between normal and OA ACVs using Holm-Sidak analysis for multiple comparison testing. RESULTS:: Over 1700 proteins were identified in ACVs. Approximately 170 proteins satisfied our stringent criteria of having more than one representative peptide per protein present and a false discovery rate ≤ 5%. These proteins included extracellular matrix components, phospholipid binding proteins, enzymes, and cytoskeletal components, including actin. While few proteins were seen exclusively in normal or OA ACVs, immunoglobulins and complement components were present only in OA ACVs. Compared to normal ACVs, OA ACVs displayed decreases in matrix proteoglycans and increases in TGFβ- induced protein βig-H3, DEL1, vitronectin, and serine protease HTRA1 (p<0.01). CONCLUSIONS:: These findings lend support to the concept of ACVs as physiologic structures in articular cartilage. Changes in OA ACVs are largely quantitative and reflect altered matrix and the presence of inflammation, rather than fundamental changes in composition.