Purification and Activity Determination of ADAMTS-4 and ADAMTS-5 and Their Domain Deleted Mutants

Determination of Versikine Levels by Enzyme-Linked Immunosorbent Assay (ELISA)

The proteoglycan versican plays multiple roles in cancer progression, from promoting cell invasion and proliferation to evasion of immune surveillance. Metalloproteinases of the A Disintegrin and Metalloproteinase with Thrombospondin-like motif (ADAMTS) family cleave versican at a specific Glu-Ala bond, thus releasing a bioactive fragment named versikine, whose biological function, still not entirely revealed, seems that of antagonizing the effects of the parental molecule. Here we describe an enzyme-linked immunosorbent assay (ELISA) that specifically detects versikine in media, pure component systems, and biological fluids using neoepitope antibodies. Such antibodies recognize their target proteolytic fragment but not the intact, parental molecule. Versikine fragments are captured by neoepitope antibodies and detected by antibodies directed against its N-terminal globular (G1) domain. The method here described can therefore be used to measure ADAMTS versicanase activity and provides a quantitative alternative to immunoblotting.

Development of Selective ADAMTS-5 Peptide Substrates to Monitor Proteinase Activity

The dysregulation of proteinase activity is a hallmark of osteoarthritis (OA), a disease characterized by progressive degradation of articular cartilage by catabolic proteinases such as a disintegrin and metalloproteinase with thrombospondin type I motifs-5 (ADAMTS-5). The ability to detect such activity sensitively would aid disease diagnosis and the evaluation of targeted therapies. Förster resonance energy transfer (FRET) peptide substrates can detect and monitor disease-related proteinase activity. To date, FRET probes for detecting ADAMTS-5 activity are nonselective and relatively insensitive. We describe the development of rapidly cleaved and highly selective ADAMTS-5 FRET peptide substrates through in silico docking and combinatorial chemistry. The lead substrates 3 and 26 showed higher overall cleavage rates (∼3-4-fold) and catalytic efficiencies (∼1.5-2-fold) compared to the best current ADAMTS-5 substrate ortho-aminobenzoyl(Abz)-TESE↓SRGAIY-N-3-[2,4-dinitrophenyl]-l-2,3-diaminopropionyl(Dpa)-KK-NH2. They exhibited high selectivity for ADAMTS-5 over ADAMTS-4 (∼13-16-fold), MMP-2 (∼8-10-fold), and MMP-9 (∼548-2561-fold) and detected low nanomolar concentrations of ADAMTS-5.

Inhibition of SMAD3 effectively reduces ADAMTS-5 expression in the early stages of osteoarthritis

OBJECTIVE

As one of the most important protein-degrading enzymes, ADAMTS-5 plays an important role in the regulation of cartilage homeostasis, while miRNA-140 is specifically expressed in cartilage, which can inhibit the expression of ADAMTS-5 and delay the progression of OA (osteoarthritis). SMAD3 is a key protein in the TGF-β signaling pathway, inhibiting the expression of miRNA-140 at the transcriptional and post-transcriptional levels, and studies have confirmed the high expression of SMAD3 in knee cartilage degeneration, but whether SMAD3 can mediate the expression of miRNA-140 to regulate ADAMTS-5 remains unknown.

METHODS

Sprague-Dawley (SD) rat chondrocytes were extracted in vitro and treated with a SMAD3 inhibitor (SIS3) and miRNA-140 mimics after IL-1 induction. The expression of ADAMTS-5 was detected at the protein and gene levels at 24 h, 48 h, and 72 h after treatment. The OA model of SD rats was created using the traditional Hulth method in vivo, with SIS3 and lentivirus packaged miRNA-140 mimics injected intra-articularly at 2 weeks, 6 weeks and 12 weeks after surgery. The expression of miRNA-140 and ADAMTS-5 in the knee cartilage tissue was observed at the protein and gene levels. Concurrently, knee joint specimens were fixed, decalcified, and embedded in paraffin prior to immunohistochemical, Safranin O/Fast Green staining, and HE staining analyses for ADAMTS-5 and SMAD3.

RESULTS

In vitro, the expression of ADAMTS-5 protein and mRNA in the SIS3 group decreased to different degrees at each time point. Meanwhile, the expression of miRNA-140 in the SIS3 group was significantly increased, and the expression of ADAMTS-5 in the miRNA-140 mimics group was also significantly downregulated (P < 0.05). In vivo, it was found that ADAMTS-5 protein and gene were downregulated to varying degrees in the SIS3 and miRNA-140 mimic groups at three time points, with the most significant decrease at the early stage (2 weeks) (P < 0.05), and the expression of miRNA-140 in the SIS3 group was significantly upregulated, similar to the changes detected in vitro. Immunohistochemical results showed that the expression of ADAMTS-5 protein in the SIS3 and miRNA-140 groups was significantly downregulated compared to that in the blank group. The results of hematoxylin and eosin staining showed that in the early stage, there was no obvious change in cartilage structure in the SIS3 and miRNA-140 mock groups. The same was observed in the results of Safranin O/Fast Green staining; the number of chondrocytes was not significantly reduced, and the tide line was complete.

CONCLUSION

The results of in vitro and in vivo experiments preliminarily showed that the inhibition of SMAD3 significantly reduced the expression of ADAMTS-5 in early OA cartilage, and this regulation might be accomplished indirectly through miRNA-140.

Transcription factor Krüppel-like factor 5-regulated N-myc downstream-regulated gene 2 reduces IL-1β-induced chondrocyte inflammatory injury and extracellular matrix degradation

Previous research has identified N-myc downstream-regulated gene 2 (NDRG2) as one of the differentially expressed genes common to rat models of osteoarthritis (OA) and human OA. The purpose of this study was to investigate the role of NDRG2 in OA. In this study, an in vitro OA model was constructed by challenging ATDC5 chondrocytes with 10 ng/ml IL-1β. After transfection of pcDNA3.1(+)/NDRG2, qPCR and western blot were performed to assay NDRG2 expression. The analyses of cell viability, apoptosis and inflammatory molecule expression were employed respectively by CCK-8, TUNEL and ELISA. The protein expression related to apoptosis, inflammation or extracellular matrix (ECM) degradation was detected by western blot. The binding of Krüppel-like factor 5 (KLF5) to NDRG2 promoter was verified by means of dual-luciferase reporter assay. After overexpression of both NDRG2 and KLF5 in IL-1β-stimulated ATDC5 chondrocytes, corresponding assays were performed to examine cell viability, apoptosis, inflammatory response and ECM degradation. In ATDC5 chondrocytes challenged with IL-1β, NDRG2 expression was much lower than that in the control group, whereas it’s overexpression helped restored cell viability and reduce cell apoptosis, inflammatory response and ECM degradation. It was also observed that KLF5 expression was decreased in IL-1β-stimulated ATDC5 chondrocytes, and that KLF5 bound to the NDRG2 promoter. Importantly, overexpressing KLF5 could reverse the protective effect of NDRG2 overexpression on IL-1β-stimulated ATDC5. Overall, NDRG2 could be transcriptionally regulated by transcription factor KLF5 and may play a protective role against chondrocyte the inflammatory response and ECM degradation in OA.