In vivo administration of recombinant TNF-α promotes bone resorption in mice

Background: In vitro studies demonstrated that proinflammatory cytokine tumor necrosis factor alpha (TNF-α) modulates bone metabolism. Objective: The aim of our study was to confirm the ability of TNF-α to induce osteoclastogenesis and bone resorption in an in vivo experiment, with the use of calvarial model in mice. Materials and methods: Twenty C57-Black mice were divided into four groups with five animals in each. The first group was infused subcutaneously on their back with recombinant mouse (rm) TNF-α via osmotic minipumps for 3 d, the second group was similarly infused with phosphate-buffered saline (PBS), the third group was infused with rmTNF-α to the region above the parietal bone and the fourth group with PBS in the same manner. Number of osteoclasts on parietal bone was determined morphometrically. Serum calcium and phosphates were monitored colorimetrically. Results: Serum calcium level and number of osteoclasts on parietal bone were significantly greater after infusion of rmTNF-α above the parietal bone, whereas after subcutaneous delivery these parameters were similar to the control group. Conclusion: We are concluding that TNF-α has the ability to change the bone metabolism in a paracrine manner only.