Abstract
The surface microstructures are essential for osteogenesis induced by tricalcium phosphate (TCP). Current studies have mainly focused on the effects on osteoblasts, while the role of its surface microstructure on osteoclasts has been less studied. This study aimed to investigate the effect and mechanism of TCP with different surface microstructures on osteoclasts. The sintering temperature was controlled to produce three different surface microstructures of TCP disks. The behavior of RAW264.7 cells on TCP disk(cell proliferation activity, differentiation, and function), cell autophagy, and the expression of factors in MAPK/ERK signaling pathway were evaluated. The three TCP materials had the same chemical properties and sizes. The surfaces of TCP-compact (TCPc), TCP-middle (TCPm), and TCP-porous (TCPp) were smooth, rough, and the roughest, respectively. The crystal size of TCPc was small, whereas the crystal size of TCP-porous (TCPp) was similar to that of TCPm but larger than that of TCPc. The culture of RAW264.7 cells on the three kinds of TCP disks revealed that the crystal size of the TCP disks had a greater influence on the activity and function of osteoclasts. Osteoclasts cocultured with TCPm and TCPp showed inhibited activity and autophagy, meanwhile the MAPK/ERK signaling pathway was activated in the process. This study demonstrated for that TCP with different surface microstructures may regulate the autophagy in RANKL-induced osteoclasts via ERK1/2 and p38 signaling pathways, sequently affecting osteoclast activity and function in bone fomation.