Role of matrix vesicles in biomineralization

Background: Matrix vesicles have been implicated in the mineralization of calcified cartilage, bone and dentin for more than 40 years. During this period, their exact role, if any in the nucleation of hydroxyapatite mineral, and its subsequent association with the collagen fibrils in the organic matrix has been debated and remains controversial. Scope of Review: This review summarizes studies spanning the whole history of matrix vesicles, but emphasizes recent findings and several hypotheses which have been recently introduced to explain in greater detail how matrix vesicles function in biomineralization. Major Conclusions: It is now generally accepted that matrix vesicles have some role(s) in mineralization: that they are the initial site of mineral formation; that MV bud from the plasma membrane of mineral forming cells, but that they take with them only a subset of the materials found in the parent membrane: that the three proteins, alkaline phosphatase, nucleotide pyrophosphatase phosphodiesterase and annexin V have important roles in the process and that matrix vesicles participate in regulating the concentration of PPi in the matrix. In contrast, many open questions remain to be answered. General Significance: Understanding the role of matrix vesicles in biomineralization will increase our knowledge of this important process. (C) 2009 Elsevier B.V. All rights reserved.