2 Background of bone remodeling from a local perspective Modern understanding of bone remodeling focuses locally on a basic multicellular unit (BMU) . The prevalent view of the BMU typically consists of three cell types: osteoclasts, osteoblasts, and osteocytes. Osteoclast cells are responsible for bone resorption, which involves the dissolution of the hydroxyapatite mineral layer and enzymatic degradation of the bone protein matrix . In opposition, osteoblast cells form the bone protein matrix by depositing unmineralized tissue called osteoid, which undergoes a highly regulated mineralization process . Osteoblasts embedded in the osteoid tissue during this process differentiate into osteocyte cells. These osteocytes trigger and possibly terminate remodeling by releasing signaling molecules at various cycle phases .