Extracellular calcium regulates the adhesion and migration of osteoclast via integrin α v β 3 / Rho A/Cytoskeleton signaling.

Integrin αv β3 is a transmembrane integrin which can initiate osteoclasts' attachment on bone, leading to downward signaling pathways and subsequent bone resorption. Different calcium concentrations have reported to have influence on the activation of integrin αv β3 . To elucidate the regulatory mechanism of extracellular calcium concentrations on osteoclasts, a controlled micro flow plate (M04S) was utilized in the ONIX flow control system to observe osteoclasts' adhesion and migration in different calcium concentration medium. Fluorescent staining is conducted to show the distribution of integrin αv β3 and cytoskeleton reorganization. In addition, western blots were performed to detect the expression of integrin αv β3 and its downstream signaling pathways related to bone resorption. Also, real-time RT-PCR data of transcription co-activator (YAP/TAZ) and hydrolytic enzymes (the matrix metalloproteinase 9 and cathepsin K) is evaluated. Our findings suggest that osteoclasts' migration and adhesion is better promoted at 0.5 mM than 1.2 mM, which can be partly explained by the induced cytoskeleton organization via integrin αv β3 /Rho GTPase. But the activation and nuclear localization of YAP/TAZ, and the secretion of hydrolytic enzymes were upregulated when calcium concentration is at a higher level (1.2 mM). According to our study, there is a highly possibility that the migration and attachment of osteoclasts and subsequent osteoclastic bone resorption are regulated by a specific range of extracellular calcium concentration.