Extracellular matrix vesicles in human osteogenic neoplasms: An ultrastructural and enzymatic study

The results of a study of the ultrastructural and enzymatic features of extracellular matrix vesicles in human osteogenic neoplasms are reported. Specimens from three osteosarcomas, a chondrosarcoma, and an osteoblastoma were processed for electron microscopic study and for preparation of vesicular, membrane, and cellular fractions. Electron micrographs of each lesion showed primary mineralization comprised of matrix vesicles and calcifying nodules. There was a distinct pattern of distribution of enzymatic activity among fractions from the osteosarcomas; namely that the highest values for specific activity of alkaline and pyrosphosphatases and adenosine triphosphases (ATPases) in the vesicle fractions and lowest in the cell fractions. This pattern was not consistent in fractions from the other neoplasms. The aforementioned enzymes are considered essential for the onset of mineralization. The data presented establish the role of matrix vesicles in neoplastic calcification and suggest the need for further studies into the diagnostic value of the vesicles.