Silencing TNFa activity by using Remicade or Enbrel blocks inflammation in whole muscle grafts: an in vivo bioassay to assess the efficacy of anti-cytokine drugs in mice

Dramatic clinical success in the treatment of chronic inflammatory diseases has resulted from the use of anti-cytokine therapies including specific blocking antibodies, soluble receptors and traps to silence the actions of inflammatory cytokines such as tumour necrosis factor alpha (TNFα) and interleukin-1 (IL-1). Two agents used clinically to block the functional activity of TNFα protein are Remicade (an antibody) and Enbrel (a soluble TNF receptor). These tools are now being extended to many other clinical disorders. We have a specific interest in the treatment of muscle diseases. In order to study the effects of novel anti-cytokine drugs on mouse models of human disease, such drugs must be investigated to determine whether they are indeed effective in blocking the inflammatory response in mouse. This has been carried out by means of a simple in vivo bioassay. Histological examination of transverse sections from whole muscle autografts in C57BL/10ScSn mice sampled at 5 days after transplantation provides an excellent assay model and clearly shows that Remicade and Enbrel block the acute inflammatory cell response in vivo. This graft model has also been used to show that a single intraperitoneal injection of Remicade (10 μ g/g) is long-lived and effective when administered at 1 week and even 4 weeks prior to the assay. Enbrel is highly effective when injected twice at -3 days and -1 day (2x100 μ g) before muscle grafting but shows no inhibition of the inflammatory response after a single injection (100 μ g) 1 week prior to grafting. This striking ablation of inflammation by pharmacological blockage of TNFα is in marked contrast to the lack of any effect in TNFα null mice. This simple reproducible in vivo assay model in mice can be used to evaluate the efficacy of many novel anti-cytokine interventions designed to block inflammation.