Suppressive effect of an antioxidant enzyme, catalase, on RANKL-induced osteoclastogenesis in BMM cells. (Top) BMM cells were infected with a recombinant adenovirus for catalase (AdCat) or the control adenovirus expressing GFP (AdGFP) with the indicated MOI (multiplicity of infection). On day 5, infected cells were stained for TRAP, and TRAP-positive MNCs were counted (bottom). Formation of TRAP-positive MNCs was severely suppressed in catalase virus-infected BMM cells (original magnification, × 100). Data represent means ± SDs of 3 independent experiments, each performed in triplicates.