Inhibition of matrix metalloproteinase-14 in osteosarcoma cells by clodronate.

BACKGROUND: Bisphosphonates reduce the bone metastasis formation and angiogenesis but the exact molecular mechanisms involved are unclear. Progelatinase A (proMMP-2; 78 KDa) is activated up during the tumor spread and metastasis by a cell surface-associated matrix metalloproteinase (membrane-type matrix metalloproteinase [MT1-MMP] or MMP-14). MATERIAL AND METHODS: We evaluated the effects of a bisphosphonate (clodronate) on MT1-MMP mRNA expression and protein production, catalytic activity and proteolytic activation of proMMP-2 by cultured human MG-63 osteosarcoma cells. RESULTS: Clodronate, at therapeutically attainable noncytotoxic concentrations, dose-dependently inhibited phorbol myristic acetate (PMA)-induced proteolytic activation of proMMP-2 by human MG-63 osteosarcoma cells. Clodronate also downregulated the PMA-induced expression of MT1-MMP mRNA and protein production in human MG-63 osteosarcoma cells, as evidenced by Northern analysis and fluorescent immunohistochemistry. Furthermore, clodronate inhibited directly and dose-dependently MT1-MMP activity, and the MT1-MMP inhibition by clodronate was reduced in the presence of an increased (5 mM) Ca(2+) concentrations when compared to physiological (1 mM) Ca(2+) concentrations. CONCLUSION: We conclude that (1) the extracellular/cell-associated mechanism of bisphosphonate involves inhibition of MT1-MMP catalytic activity eventually by chelation, and that (2) intracellular mechanism involves downregulation of induced MT1-MMP mRNA and protein expression. The inhibition and downregulation of MT1-MMP by clodronate can be related to their ability to reduce MG-63 osteosarcoma cell invasion and spread. These findings may, at least in part, explain at molecular level the antitumor and antibone resorption activities of clodronate observed in clinical studies.

The real contamination of femoral head allografts washed with pulse lavage.

At the Tampere Bone Bank, all the discarded femoral heads from September 1997 to May 2000 were recultured. The grafts had been washed with pulse lavage at harvesting. 48 grafts had been discarded because of a positive culture and 85 with negative cultures because of positive or insufficient serological information. The femoral heads were split into halves, which were recultured as a whole in thioglycolate broth for 14 days. The contamination of previously culture positive and negative femoral heads did not differ. In only 2 cases did we find the same type of bacteria in the primary as in the new culture. Most of the primary contamination proved to be false positive. The real contamination seems to be very low, at least after pulse lavage washing of the femoral head.