A specific subtype of osteoclasts secretes factors inducing nodule formation by osteoblasts

► Only mature osteoclasts are sources of anabolic stimuli for osteoblasts. ► Osteopetrotic osteoclasts secrete anabolic factors for osteoblasts. ► Enhanced osteoclast survival compensates for the lack of resorption derived factors. ► Osteoclasts on non-natural substrates fail to secrete anabolic molecules. ► Interaction with matrix strongly modulates anabolic potential of the osteoclasts.