How do osteoblast and osteoclast communicate with each other?

Osteoblast and osteoclast are two types of bone cells that work together to regulate bone growth by forming new bone tissue and breaking down old or damaged bone tissue. Communication between osteoblasts and osteoclasts occurs in a basic multicellular unit (BMU) during the three bone remodeling phases - initiation, transition and termination. In the bone environment osteoblast and osteoclast communicate with each other through cell-to-cell interaction, cell-bone matrix interaction, and paracrine signaling molecules. 

Molecular mechanisms of cellular communication between osteoblast and osteoclast: 

Osteoblasts and osteoclasts communicate directly through interactions involving EFNB2-EPHB4, FAS-FASL, and NRP1-SEMA3A to control cell proliferation, differentiation, and survival. 

Osteoblast-mediated bone formation is stimulated by TGF-β and IGF-1, which is released from the bone matrix during osteoclast-mediated bone resorption.  

M-CSF, RANKL, and WNT5A secreted by osteoblasts promote formation and development of osteoclasts. Osteoblasts also release OPG and WNT16 to inhibit the activity of osteoclasts. Conversely, osteoclasts secrete S1P, CTHRC1, and C3 to promote osteoblast differentiation and SEMA4D to suppress osteoblast differentiation.