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Morphological and biochemical characterization of mineralizing primary cultures of avian growth plate chondrocytes: evidence for cellular processing of Ca2+ and Pi prior to matrix mineralization.
- Source :
-
Journal of cellular biochemistry [J Cell Biochem] 1995 Feb; Vol. 57 (2), pp. 218-37. - Publication Year :
- 1995
-
Abstract
- Advances in the culture of mineralizing growth plate chondrocytes provided an opportunity to study endochondral calcification under controlled conditions. Here we report that these cultures synthesize large amounts of proteins characteristically associated with mineralization: type II and X collagens, sulfated proteoglycans, alkaline phosphatase, and the bone-related proteins, osteonectin and osteopontin. Certain chondrocytes appeared to accumulate large amounts of Ca2+ and Pi during the mineralization process: laser confocal imaging revealed high levels of intracellular Ca2+ in their periphery and X-ray microanalytical mapping revealed the presence of many Ca(2+)- and Pi-rich cell surface structures ranging from filamentous processes 0.14 +/- 0.02 microns by 0.5-2.0 microns, to spherical globules 0.70 +/- 0.27 microns in diameter. Removal of organic matter with alkaline sodium hypochlorite revealed numerous deposits of globular (0.77 +/- 0.19 micron) mineral (calcospherites) in the lacunae around these cells. The size and spatial distribution of these mineral deposits closely corresponded to the Ca(2+)-rich cell surface blebs. The globular mineral progressively transformed into clusters of crystallites. Taken with earlier studies, these findings indicate that cellular uptake of Ca2+ and Pi leads to formation of complexes of amorphous calcium phosphate, membrane lipids, and proteins that are released as cell surface blebs analogous to matrix vesicles. These structures initiate development of crystalline mineral. Thus, the current findings support the concept that the peripheral intracellular accumulation of Ca2+ and Pi is directly involved in endochondral calcification.
- Subjects :
- Animals
Cell Membrane metabolism
Cell Membrane ultrastructure
Cells, Cultured
Chickens
Collagen biosynthesis
Culture Media
Electrophoresis, Polyacrylamide Gel
Growth Plate cytology
Growth Plate ultrastructure
Kinetics
Microscopy, Confocal
Microscopy, Electron, Scanning
Molecular Weight
Pepsin A
Proline metabolism
Proteins analysis
Proteins isolation & purification
Proteoglycans biosynthesis
Time Factors
Calcification, Physiologic
Calcium metabolism
Growth Plate physiology
Phosphates metabolism
Protein Biosynthesis
Subjects
Details
- Language :
- English
- ISSN :
- 0730-2312
- Volume :
- 57
- Issue :
- 2
- Database :
- MEDLINE
- Journal :
- Journal of cellular biochemistry
- Publication Type :
- Academic Journal
- Accession number :
- 7759559
- Full Text :
- https://doi.org/10.1002/jcb.240570206