Regulatory roles of zinc in matrix vesicle-mediated mineralization of growth plate cartilage

Thorsten Kirsch, Gerald Harrison, Kai P. Worch, Ellis E. Golub

    Research output: Contribution to journalArticle

    Abstract

    Zinc (Zn2+) has long been known to play important roles in mineralization and ossification of skeletal tissues, but the mechanisms of Zn2+ action are not well understood. In this study we investigated the effects of Zn2+ on mineralization in a cell culture system in which terminal differentiation and mineralization of hypertrophic growth plate chondrocytes was induced by retinoic acid (RA) treatment. Addition of Zn2+ to RA-treated cultures decreased mineralization in a dose-dependent manner without affecting alkaline phosphatase (APase) activity. Characterization of matrix vesicles (MVs), particles that initiate the mineralization process, revealed that vesicles isolated from RA-treated and RA/Zn2+-treated cultures showed similar APase activity, but vesicles from RA/Zn2+-treated cultures contained significantly less Ca2+ and P(i). MVs isolated from RA- treated cultures were able to take up Ca2+ and mineralize in vitro, whereas vesicles isolated from RA/Zn2+-treated cultures were not able to do so. Detergent treatment, which ruptures the MV membrane and exposes preformed intravesicular Ca2+-P(i)-phospholipid complexes, did not restore the Ca2+ uptake abilities of MVs isolated from RA/Zn2+treated cultures, suggesting that vesicles from RA/Zn2+-treated cultures did not contain functional Ca2+-P(i)phospholipid complexes. Zn2+ treatment did not affect the content of annexins II, V, and VI in MVs or the Ca2+-dependent, EDTA- reversible binding of these molecules to the membrane surface. However, Zn2+ treatment did affect the EDTA-nonreversible binding of these molecules to the MV membrane, suggesting that Zn2+ interferes with the assembly of annexins in the MV membrane. In addition, Zn2+ inhibited annexin II-, V-, and VI-mediated Ca2+ influx into liposomes. In conclusion, Zn2+ inhibits the mineralizing competence of intravesicular Ca2+-P(i)-phospholipid complexes and function of annexin channels, thereby controlling Ca2+ influx into MVs, the formation of the first crystal phase inside the vesicles and initiation of mineralization.

    Original languageEnglish (US)
    Pages (from-to)261-270
    Number of pages10
    JournalJournal of Bone and Mineral Research
    Volume15
    Issue number2
    DOIs
    StatePublished - 2000

    Keywords

    • Annexins
    • Chondrocytes
    • Matrix vesicles
    • Mineralization
    • Zinc

    ASJC Scopus subject areas

    • Endocrinology, Diabetes and Metabolism
    • Orthopedics and Sports Medicine

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