Fig. 8.

Illustration of the role of osteocytic integrin a5β1 in anabolic response to mechanical stimulation in bone. Upon mechanical loading, COX-2 and PGE2 level are increased. Integrin α5β1 expressed on the osteocyte surface will be activated to change its extended extracellular domain and trigger the opening of Cx43 hemichannels as shown previously.¹⁵ The opened hemichannels will release PGE2 that functions in an autocrine manner⁸⁴ through the EP4 receptor to reduce SOST expression.⁵⁴ As a result, β-catenin expression is increased in osteoblasts, which leads to an increase in osteoblast activity and endosteal bone formation. HC, hemichannel