Toll-like receptor(TLR) 4, which mediates immunity to grand negative bacteria, is the first-identified TLR family member. TLR2 recognizes many pathogen-associated molecular patterns and responds to lipopolysaccharide stimuli with TLR4. TLR2 and TLR4 have been confirmed to regulate the osteogenesis of some cells. For example, TLR2 and TLR4 participate in aortic valve calcification through the upregulation of osteogenic differentiation in human aortic valve interstitial cells. TLR2 and TLR4 can also improve coronary atherosclerosis by increasing the expression of bone morphogenetic protein 2 in coronary artery endothelial cells, and they are involved in the osteogenic differentiation of bone marrow stromal cells. In dental pulp tissue, odontoblast-like cells, which express TLR4, migrate to damaged zones of odontoblasts and form reparative dentin. Both TLR2 and TLR4 regulate the expression of inflammation factors and odontoblastic differentiation when damage occurs. Thus, the regulation mechanism of TLR2 and TLR4 in osteogenic differentiation needs to be studied further.
