In this model, the ligation of the medial collateral ligament coupled with disruption of the meniscus from its ante rior medial attachment induces reproducible OA devel selleckchem Trichostatin A opment over a three month period. In the present studies, we will determine the role of MMP13 in MLI induced OA progression. We will use Col2CreER, Mmp13fx fx mice to block Mmp13 expression in chondrocytes and use MMP13 inhibitors to inhibit MMP13 activity. Methods Meniscal ligamentous injury induced osteoarthritis model and treatment of MMP13 inhibitor Wild type C57BL 6J and Mmp13fx fx mice were obtained from Jackson Laboratories. Col2CreER transgenic mice were crossed with Mmp13fx fx mice to generate Col2CreER,Mmp13fx fx mice. Tamoxifen was administered to two week old Mmp13Col2ER mice and littermate con trols by intraperitoneal injection for five days.

MLI surgery Inhibitors,Modulators,Libraries was performed to induce knee OA in 10 week old Mmp13Col2ER and Cre negative control mice. Details regarding MLI sur gery were previously described. The surgery was performed on the right hind limbs as follows, 1 following anesthesia, making a 5 mm parapatellar, 2 identifying and transecting the medial collateral ligament with a 25 gauge needle, 3 applying Inhibitors,Modulators,Libraries valgus stress to the knee to confirm disruption and provide access to the meniscus, 4 detach ing and partially Inhibitors,Modulators,Libraries removing the anterior horn of the medial meniscus, 5 closing of the wound with 4. 0 nylon sutures applied in an interrupted pattern. The left hind limb was used as a control. The left hind limb was opened and the structures of the knee were exposed and then the skin incision closed without manipulating the joint tissue.

Pre and post surgery, mice were provided analgesia every 24 hours for 72 hours and the sutures were removed after 10 days. Both left and right knee joints were harvested, processed, sectioned and stained 4, 8, 12, and 16 weeks post surgery. MLI and sham surgeries were Inhibitors,Modulators,Libraries also performed on 10 week old C57BL 6J mice. The MMP13 inhibitor CL82198 was administered to Inhibitors,Modulators,Libraries wild type mice begin ning one day after surgery by i. p. injection every other day for up to 16 weeks at doses of 1, 5, 10 mg kg body weight. Normal saline was used as a control. Knee joints were col lected, sectioned and stained 12 weeks post surgery. All protocols were approved by the Institu tional Animal Care and Use Committee at the University of Rochester.

Histology and histomorphometry Knee joints from each group were harvested and prepared for sectioning and not analysis. Samples were fixed in 10% neutral buffered formalin for three days, then decalcified with formic acid for seven days. After neu tralizing with Cal arrest, samples were processed and embedded in paraffin. Three um thick mid saggital sections at three different levels were cut from the medial compartment of the joints. The sections were stained with Alcian blue H E and safranin O Fast Green.