TGF-β signaling plays a key role in the temporal and spatial regulation of bone remodeling. During osteoclast bone resorption, TGF-β is released from the bone matrix and activated. Active TGF-β recruits mesenchymal stem cells to the bone resorption pit through the SMAD signaling pathway. Mesenchymal stem cells undergo osteoblast differentiation and deposit new bone fi lling in the resorption pit and maintaining the structural integrity of the skeleton. Thus, TGF-β signaling plays a key role in the coupling process and disruptions to the TGF-β signaling pathway lead to loss of skeletal integrity. This chapter describes methods on how to quantitate bone matrix TGF-β and assess its role in mesenchymal stem cell migration both in vitro and in vivo.