Laser microscopic measurement of osteoclastic resorption pits on biomaterials

The color 3D profile measurement laser microscope was applied and evaluated for the quantitative analysis of resorption pits made by osteoclasts cultured on biomaterials for the first time. In this study, we measured the exact volume of resorption pits made by osteoclasts cultured on two synthetic biomaterials, TCP (tricalcium phosphate) and ZnTCP (zinc-containing TCP), and compared the resorbing activity of osteoclasts on the two materials. Mature osteoclasts were isolated from rabbit bone marrow and cultured on discs of TCP and ZnTCP for 24 h. The depth and volume of resorption pits was significantly decreased on ZnTCP compared to TCP, although the plane area of the pits differed little between the two materials. These results suggested that Zn ions released from ZnTCP on mature osteoclasts do not contribute to the early phase of the resorption cycle, but mainly affect the later phase. We demonstrated that the depth, volume, and area of resorption pits can be measured reliably by this technique.