Matrix vesicle plasma cell membrane glycoprotein-1 regulates mineralization by murine osteoblastic MC3T3 cells

J Bone Miner Res. 1999 Jun;14(6):883-92. doi: 10.1359/jbmr.1999.14.6.883.


A naturally occurring nonsense truncation mutation of the inorganic pyrophosphate (PPi)-generating nucleoside triphosphate pyrophosphohydrolase (NTPPPH) PC-1 is associated with spinal and periarticular ligament hyperostosis and cartilage calcification in "tiptoe walking" (ttw) mice. Thus, we tested the hypothesis that PC-1 acts directly in the extracellular matrix to restrain mineralization. Cultured osteoblastic MC3T3 cells expressed PC-1 mRNA and produced hydroxyapatite deposits at 12-14 days. NTPPPH activity increased steadily over 14 days. Transforming growth factor-beta and 1,25-dihydroxyvitamin D3 increased PC-1 and NTPPPH in matrix vesicles (MVs). Because PC-1/NTPPPH was regulated in mineralizing MC3T3 cells, we stably transfected or infected cells with recombinant adenovirus, in order to express 2- to 6-fold more PC-1. PC-1/NTPPPH and PPi content increased severalfold in MVs derived from cells transfected with PC-1. Furthermore, MC3T3 cells transfected with PC-1 deposited approximately 80-90% less hydroxyapatite (by weight) than cells transfected with empty plasmid or enzymatically inactive PC-1. ATP-dependent 45Ca precipitation by MVs from cells overexpressing active PC-1 was comparably diminished. Thus, regulation of PC-1 controls the PPi content and function of osteoblast-derived MVs and matrix hydroxyapatite deposition. PC-1 may provide a novel therapeutic target in certain disorders of bone mineralization.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenoviridae / genetics
  • Animals
  • Bone Density / physiology*
  • Cell Differentiation / physiology
  • Cell Line
  • Durapatite / metabolism
  • Extracellular Matrix Proteins / physiology*
  • Gene Transfer Techniques
  • Liposomes
  • Membrane Glycoproteins / physiology*
  • Mice
  • Osteoblasts / physiology*
  • Phosphoric Diester Hydrolases*
  • Pyrophosphatases*


  • Extracellular Matrix Proteins
  • Liposomes
  • Membrane Glycoproteins
  • Durapatite
  • Phosphoric Diester Hydrolases
  • ectonucleotide pyrophosphatase phosphodiesterase 1
  • Pyrophosphatases