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Expression and Regulation of Na‐Dependent P i Transport in Matrix Vesicles Produced by Osteoblast‐like Cells
Author(s) -
Montessuit C.,
Bonjour J.P.,
Caverzasio J.
Publication year - 1995
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1002/jbmr.5650100416
Subject(s) - osteoblast , alkaline phosphatase , chemistry , cell culture , microbiology and biotechnology , extracellular matrix , vesicle , biophysics , stimulation , biochemistry , biology , endocrinology , in vitro , membrane , enzyme , genetics
Abstract Extracellular matrix vesicles (MV) are the loci of initial mineralization in several calcifying tissues. We recently reported that MV isolated from chicken epiphyseal cartilage are equipped with a Na‐dependent P i transport (NaP i T) system. The activity of the NaP i T system appeared to be crucial for the development of MV‐mediated calcification. In the present study we investigated the expression of NaP i T activity in MV produced by the osteoblast‐like cells MC3T3‐E1. The relationship between changes in NaP i T activity in the intact cells and in the released MV was also examined. NaP i T activity in MV harvested from cultured MC3T3‐E1 cells was transiently expressed. It was markedly increased between Days 8 and 10 (5‐ to 6‐fold), and then gradually decreased. NaP i T activity was enriched in MV as compared with the parent osteoblast‐like cells, while the Na‐dependent transport system for alanine (NaAIaT) was not. When NaP i T activity was enhanced in osteoblast‐like cells by fetal calf serum (FCS) or P i depletion, P i transport stimulation was observed in the derived MV as well. Alkaline phosphatase (AP) was differentially expressed and regulated in MV from MC3T3‐E1 cell cultures, as compared with NaP i T. In contrast to the transient expression of NaP i T, AP activity in MV increased continuously with time in culture. It was stimulated by FCS treatment of the parent cells, but decreased in MV obtained from P i ‐depleted cultures. These results suggest that the presence in osteogenic cells of selective regulatory mechanisms for the insertion and enrichment of P i transport activity in released MV. This process is probably of biological significance for the regulation of the cascade of events that leads to the mineralization of the bone matrix.