1. Regulation of the membrane bound matrix metalloprotease (MT1-MMP) in mechanically stimulated bioengineered articular cartilage. 1 CIHR BioEngineering of Skeletal Tissues Team, Mount Sinai Hospital 2 Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada. 1 De Croos, J. N. A. , 1 S é guin, C. A., 1,2 Grynpas, M. D., 1,2 Pilliar R. M., and 1,2, Kandel, R. A.
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4. Formation of Articular Cartilage in vitro Cell culture Chondrocytes Bone Substitute
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6. Implantation of a biphasic construct Sheep Knee, 9 months post-implantation Toluidine blue/trichrome, X25 magnification
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8. Mechanical Stimulation Chondrocytes were cyclically compressed within three days of initial seeding for 30 minutes (1kPa, 1Hz) MACH-1 mechanical tester Tissue CPP Tygon Tubing Agarose Plug MACH-1 Mechanical Stimulator
9. Background Waldman et al. 2006. Osteoarthritis.Cartilage. De Croos et al. 2006. Matrix Biol. De Croos et al. 2007. Osteoarthritis.Cartilage. 24 h 0 h mmp-13 aggrecan type II collagen MMP-13 Proteoglycan Collagen Egr-1 pERK1/2 , egr-1 2h 0h 6h 12h 24h 0.5h During cyclic compression (30 minutes, 1kPa, 1Hz). Stimulation ends
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11. Egr-1 binds to MT1-MMP promoter A) B) Supershift DNA/Protein DNA/Protein US S US S US S 0 min 15 min 60 min + - - - - - - Egr-1 Antibody - + - - - - - Sp-1 competitor (10X) - - + - - - - Egr-1 competitor (10X) - - - + + - - Mutant MT1-MMP + + + - - + + MT1-MMP S S S S US S US
14. MT1-MMP expression patterns * p <0.05, n=4 * significant difference compared to corresponding controls, p <0.05, n=4. *
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18. Collagen and Proteoglycan accumulation (at 4 weeks) * significant difference compared to corresponding controls, p <0.05, n=6. * * * *
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Editor's Notes
Single cells embedded in ECM. Proteoglycans and collagens are the major protein in ECM Avascularity.
We are tissue engineers and are interested in articular cartilage. This tissue is unique in that when damaged there is a reduced ability for the tissue to self-repair. Our approach involves generating articular cartilage in vitro and replacing the damaged tissue.
Bovine. Seeded on top of a 4mm bone substitute
The creation of a biphasic construct is to allow integration and anchoring. This tissue is inferior to native tissue. We are not sure how a bigger construct would be like given the reduced physical properties.
Cartilage is always loaded. Unloading causes atrophy.
In particular we saw an increase in MMp13, a catabolic enzyme followed by anabolic changes. This suggests a remodelling pathway. As scuh I was interested in what initiates this catabolic event so…
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