Figure 7.

Regression analysis between osteoclast phenotype and its anabolic effects and the schematic of the hypothesis of interactions between osteoblastic cells, osteoclasts, and surface roughness. The average nuclei number of each osteoclast on different surfaces was correlated with its anabolic effects on osteoblastic cells. Both (A) average nuclei number of osteoclasts from RAW264.7 and their anabolic effects on mouse osteoprogenitor cells and (B) average nuclei number of primary mouse osteoclasts and their anabolic effects on primary rat MSCs displayed a logarithmic correlation, respectively. (C) On the basis of our findings of different osteoclast phenotypes and their anabolic effects, the hypothesis of the effect of roughness on osteoclastogenic differentiation and further osteogenic differentiation was proposed. On smoother surfaces, osteoclasts exhibit larger size and more nuclei in each osteoclast and secrete more anabolic clastokines to promote osteogenic differentiation of MSCs. In contrast, on rougher surfaces, osteoclasts exhibit smaller size and fewer nuclei in each osteoclast and secrete less anabolic clastokines to promote osteogenic differentiation. Green dots indicate potential clastokines (such as CTHRC1) secreted from osteoclasts.