Annexin-mediated Ca2+ influx regulates growth plate chondrocyte maturation and apoptosis

Wei Wang, Jinping Xu, Thorsten Kirsch

    Research output: Contribution to journalArticle

    Abstract

    Maturation of epiphyseal growth plate chondrocytes plays an important role in endochondral bone formation. Previously, we demonstrated that retinoic acid (RA) treatment stimulated annexin-mediated Ca2+ influx into growth plate chondrocytes leading to a significant increase in cytosolic Ca2+, whereas K-201, a specific annexin Ca2+ channel blocker, inhibited this increase markedly. The present study addressed the hypothesis that annexin-mediated Ca2+ influx into growth plate chondrocytes is a major regulator of terminal differentiation, mineralization, and apoptosis of these cells. We found that K-201 significantly reduced up-regulation of expression of terminal differentiation marker genes, such as cbfal, alkaline phosphatase (APase), osteocalcin, and type I collagen in RA-treated cultures. Furthermore, K-201 inhibited up-regulation of annexin II, V, and VI gene expression in these cells. RA-treated chondrocytes released mineralization-competent matrix vesicles, which contained significantly higher amounts of annexins II, V, and VI as well as APase activity than vesicles isolated from untreated or RA/K-201-treated cultures. Consistently, only RA-treated cultures showed significant mineralization. RA treatment stimulated the whole sequence of terminal differentiation events, including apoptosis as the final event. After a 6-day treatment gene expression of bcl-2, an anti-apoptotic protein, was down-regulated, whereas caspase-3 activity and the percentage of TUNEL-positive cells were significantly increased in RA-treated cultures compared with untreated cultures. Interestingly, the cy-. tosolic calcium chelator BAPTA-AM and K-201 protected RA-treated chondrocytes from undergoing apoptotic changes, as indicated by higher bcl-2 gene expression, reduced caspase-3 activity, and the percentage of TUNEL-positive cells. In conclusion, annexin-mediated Ca2+ influx into growth plate chondrocytes is a positive regulator of terminal differentiation, mineralization, and apoptosis events in growth plate chondrocytes.

    Original languageEnglish (US)
    Pages (from-to)3762-3769
    Number of pages8
    JournalJournal of Biological Chemistry
    Volume278
    Issue number6
    DOIs
    StatePublished - Feb 7 2003

    ASJC Scopus subject areas

    • Biochemistry
    • Molecular Biology
    • Cell Biology

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