2009 Volume 18 Issue 3 Pages 135-140
Using a transmission electron microscope, we compared the ultrastructure of apatite crystals of normal calcified hard tissue to that of apatite crystals created under pathological conditions. We also sought to verify whether the process of calcification resembles that of osteogenesis after the phenotypic change of soft tissue cells into hard tissue-forming cells. Electron micrographs clearly revealed that cellular debris, plausibly originating from degenerated immune cells like macrophages as well as perivascular cells in intima of femoral artery lesions, seemed to serve in the formation of an organic envelope. This indicates that crystal formation is accompanied by the death of cells. Judging from the lattice image, we also found that the calcified deposits consisted of 2 distinct types of apatite crystals. One type has central dark lines, while the other does not have lines. In addition, the crystals were of various sizes and some showed lattice defects. From these findings, we concluded that ectopic calcification occurred in a manner different from the calcification of normal hard tissues, suggesting that cellular phenotypic change may not happen in vivo.
