Preparation of recombinant tissue inhibitor of metalloproteinases-1 (TIMP-1) in high yield and identification of a hydrophobic surface feature

Retinoic acid and oncostatin M combine to promote cartilage degradation via matrix metalloproteinase-13 expression in bovine but not human chondrocytes

OBJECTIVES

Retinoic acid (RetA) and oncostatin M (OSM) have both been shown to mediate potent effects with respect to extracellular matrix integrity. This study assesses the effects of a RetA + OSM combination on cartilage catabolism.

METHODS

Animal and human cartilage samples were used to assess the ability of RetA + OSM to promote the release of collagen and proteoglycan fragments, which was determined by measuring glycosaminoglycan and hydroxyproline, respectively. Total collagenolytic and tissue inhibitor of metalloproteinases (TIMP) inhibitory activities were determined by bioassay, whilst gene expression of matrix metalloproteinases (MMPs) and TIMP-1 were determined by northern blotting. Immunohistochemistry was used to assess the presence of MMP-1 and -13 in resorbing cartilage explants.

RESULTS

Both agents alone induced proteoglycan release from bovine cartilage, whilst RetA-induced collagen release was variable. Reproducible and synergistic collagenolysis was observed with RetA + OSM, which appeared to be due to MMP-13. Similar collagen release was observed from porcine cartilage. Conversely, no collagen release was seen with human articular cartilage. In primary human chondrocytes, RetA + OSM failed to induce MMP-1 or -13 but caused a significant increase in TIMP-1 expression.

CONCLUSIONS

These novel observations show that the combination of RetA + OSM has profound effects on cartilage matrix turnover, but these effects are species-specific. A better understanding of the mechanism by which this combination differentially regulates MMP and TIMP expression in human chondrocytes could provide valuable insight into new therapeutic strategies aimed at the prevention of cartilage destruction.

Interleukin 17 induces cartilage collagen breakdown: novel synergistic effects in combination with proinflammatory cytokines

OBJECTIVE

To investigate whether interleukin 17 (IL17), derived specifically from T cells, can promote type II collagen release from cartilage. The ability of IL17 to synergise with other proinflammatory mediators to induce collagen release from cartilage, and what effect anti-inflammatory agents had on this process, was also assessed.

METHODS

IL17 alone, or in combination with IL1, IL6, oncostatin M (OSM), or tumour necrosis factor alpha (TNFalpha), was added to bovine nasal cartilage explant cultures. Proteoglycan and collagen release were determined. Collagenolytic activity was determined by bioassay. Chondroprotective effects of IL4, IL13, transforming growth factor beta1 (TGFbeta1) and insulin-like growth factor-1 (IGF1) were assessed by inclusion in the explant cultures.

RESULTS

IL17 alone stimulated a dose dependent release of proteoglycan and type II collagen from bovine nasal cartilage explants. Suboptimal doses of IL17 synergised potently with TNFalpha, IL1, OSM, and IL6 to promote collagen degradation. This collagen release was completely inhibited by tissue inhibitor of metalloproteinase-1 and BB-94 (a synthetic metalloproteinase inhibitor), and was significantly reduced by IL4, IL13, TGFbeta1, and IGF1. In IL17 treated chondrocytes, mRNA expression for matrix metalloproteinase (MMP)-1, MMP-3, and MMP-13 was detected. Moreover, a synergistic induction of these MMPs was seen when IL17 was combined with other proinflammatory cytokines.

CONCLUSIONS

IL17 can, alone and synergistically in combination with other proinflammatory cytokines, promote chondrocyte mediated MMP dependent type II collagen release from cartilage. Because levels of all these proinflammatory cytokines are raised in rheumatoid synovial fluids, this study suggests that IL17 may act as a potent upstream mediator of cartilage collagen breakdown in inflammatory joint diseases.

Activation of procollagenases is a key control point in cartilage collagen degradation: interaction of serine and metalloproteinase pathways

OBJECTIVE

Bovine and human cartilages in explant culture respond to proinflammatory cytokines with the up-regulation of procollagenases. In stimulated bovine nasal cartilage (BNC), >90% of collagen is released by day 14 of culture, but collagen release is rarely seen before day 7. The aim of this study was to investigate if activation of procollagenases is a rate-limiting step in cartilage collagen breakdown.

METHODS

BNC and human articular cartilage explants were cultured with interleukin-1alpha (IL-1alpha) and/or oncostatin M (OSM) with or without test reagents. Collagen levels were determined by assay of hydroxyproline. Collagenase activity was measured using the diffuse fibril assay.

RESULTS

The addition of procollagenase activators, matrix metalloproteinase 3 (MMP-3), and APMA to IL-1alpha/OSM-stimulated BNC resulted in early release of collagen. The release with APMA was completely blocked by the addition of tissue inhibitor of metalloproteinases 1. This shows that procollagenases are present early in the culture period, but cartilage collagen breakdown does not happen until activation occurs. The addition of plasminogen to IL-1alpha/OSM-stimulated cartilage produced early collagen release in bovine and a significant increase in human cartilage. Thus, plasminogen activators (PAs) are present and convert plasminogen to plasmin, a known activator of several MMPs, including collagenases. Addition of alpha1-proteinase inhibitor or a urokinase-type PA inhibitor, 7-amino-4-chloro-3-(3-isothiureidopropoxy) isocoumarin, partially blocked the breakdown of collagen from IL-1alpha/OSM-treated bovine cartilage. This suggests that serine proteinases are involved in the activation cascades of procollagenases that result in cartilage collagen breakdown.

CONCLUSION

The activation of procollagenases is a key control point in cartilage collagen breakdown, and serine proteinase pathways activate MMPs.

Refolding of therapeutic proteins produced in Escherichia coli as inclusion bodies

Overexpression of cloned or synthetic genes in Escherichia coli often results in the formation of insoluble protein inclusion bodies. Within the last decade, specific methods and strategies have been developed for preparing active recombinant proteins from these inclusion bodies. Usually, the inclusion bodies can be separated easily from other cell components by centrifugation, solubilized by denaturants such as guanidine hydrochloride (Gdn-HCl) or urea, and then renatured through a refolding process such as dilution or dialysis. Recent improvements in renaturation procedures have included the inhibition of aggregation during refolding by application of low molecular weight additives and matrix-bound renaturation. These methods have made it possible to obtain high yields of biologically active proteins by taking into account process parameters such as protein concentration, redox conditions, temperature, pH, and ionic strength.