Proteomic analysis of cytokine-induced cartilage degradation in normal cartilage and cartilage lacking ADAMTS-5 activity

Destruction of the cartilage aggrecan network is a key event in joint pathologies such as osteoarthritis. Aggrecanases, such as ADAMTS-5 (a disintegrin and metalloprotease with thrombospondin repeats 5), are therefore prospective therapeutic targets. To date, the consequences of ADAMTS-5 ablation in cartilage have yet to be investigated at the proteome level.

Here we compared interleukin-1a (IL-1a) and retinoic acid (RetA) -induced cartilage degradation in the presence and absence of ADAMTS-5 catalytic activity using WT and TS5Dcat mouse femoral head cartilage explants. Proteins harvested from the media of control and stimulated cartilage were analyzed by nano-LC and tandem mass spectrometry (LTQ-Orbitrap), and MaxQuant/Perseus software used for protein identification and to compare peptide ion intensities between treatments. We identified 384 proteins based on two or more distinct peptides (protein FDR < 0.01%). Principal components analysis identified IL-1a treatment having the strongest influence over protein variance (PC1 = 48%). Proteins significantly modulated in WT and TS5Dcat IL-1a -treated cartilage included proteases (Mmp3, Mmp12, Mmp13), protease inhibitors (Serpina3n, Serpine2, Serpinf1 and Timp1), chemokines (Cxcl1, Cxcl2, Cxcl3) and complement factors (CfB and C3). In addition to notable matrix components (Hpln1, Acan) and secreted factors (S100a11, Serpine1, Ctsd) a major difference between genotypes was the IL-1a-induced down-regulation of key glycolytic enzymes (Eno1, Pkm, Aldoa and Tpi1) in WT cartilage only. A further unanticipated genotype-specific effect was the increased abundance of several histone subunits in RetA-treated WT samples only. Further experiments are underway to confirm these findings and investigate novel consequences of ADAMTS-5 ablation on cartilage degradation.