Previous studies found that RANKL-deficient mice showed severe osteopetrosis, with no osteoclasts, marrow spaces, or tooth eruption, and exhibited profound growth retardation at several skeletal sites, including the limbs, skull, and vertebrae (36, 37) , and therefore it seems unsuitable to use RANKL-deficient mice for long-term CS exposure. This evidence concerns the gene TNFSF11 and osteopetrosis.