Nanoscale architecture in atherosclerotic calcification.

Calcium mineral deposits are radiographically evident in the majority of significant atherosclerotic lesions.1 These deposits generally consist of a nonhomogeneous composite containing hydroxyapatite mineral nanocrystals embedded in an organic matrix including type I collagen nanofibers. The morphometry varies over a spectrum. Amorphous deposits lack organization at the lightmicroscopic scale, whereas bone-like deposits have varying degrees of architectural macro-organization similar to those of developing and mature skeletal bone, which also consist of a nonhomogeneous composite containing hydroxyapatite nanocrystals embedded in a collagenous organic matrix. Based on histopathologic features, the organized, bone-like deposits appear to arise from angiogenic invasion of the amorphous deposits.2 This is consistent with the known sequence of events that leads to bone formation in fracture repair, embryonic intramembranous ossification, and in embryonic endochondral ossification, where bone arises from a cartilage scaffold.