Dynamic changes in bone cells and extracellular matrix vesicles during healing of alveolar bones in rats: An ultrastructural and biochemical study

The changes In ultrastructure, quantities and enzymatic activity of cells and extracellular matrix vesicles were studied during alveolar bone healing after tooth extraction in rats. Biochemical studies revealed a marked decrease In protein content of the isolated fractions of vesicles immediately after the surgical procedure. Transmission electron microscopy confirmed that an extensive tissue disruption occurred at that stage. These changes were accompanied by decreased activities of cellular and vesicular alkaline phosphatase and of different ATPases. The recovery of enzymatic activity on the 9th day was expressed in cells and vesicles. The different stages of healing were characteristic of primary calcification comprising active osteoblasts, matrix vesicles and calcifying nodules. It is suggested that the amounts and enzymatic activities of extracellular matrix vesicles may serve as a marker system to evaluate the different stages of primary mineralization.