Mechanism of calcification: Role of collagen fibrils and collagen‐phosphoprotein complexes in vitro and in vivo

Glimcher, Melvin J.

doi:10.1002/ar.1092240205

Cited by 307 publications

(172 citation statements)

References 72 publications

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“…AFM demonstrated that "HA" nanoparticles of about 20 nm were embedded within the gelatine structure so that they split the bed of gelatine nanofibrils into flat bundles of about 45 nm width. HA crystals of similar size are found in natural bone [12][13][14]. Gaps were detected every 200-300 nm along these flat bundles which are also found in the collagen of natural bone [9].…”

Section: Discussionmentioning

confidence: 56%

Structural hierarchy of biomimetic materials for tissue engineered vascular and orthopedic grafts

et al. 2007

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Gelatine gels and gelatine/elastin gels have been prepared to be used in tissue engineered vascular grafts. Optical microscopy and AFM revealed that the gelatine formed nanofibrils as in soft collagen tissues. The gelatine/elastin gels were nanocomposites with flat elastin nanodomains embedded in the gelatine matrix mimicking the structure of the tunica media in arteries. Gelatine/"hydroxyapatite" nanocomposites were prepared with the in situ production of "hydroxyapatite" in solution. AFM revealed "hydroxyapatite" solid nanoparticles of about 20 nm size embedded in the gelatine matrix which formed a hierarchical structure similar to that of the collagen matrix in bone. The application of a magnetic field of 9.4 T resulted in the elongation and orientation of gelatine particles and orientation of gelatine microfibrils in a direction perpendicular to that of the magnetic field.3

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Section: Discussionmentioning

confidence: 56%

Structural hierarchy of biomimetic materials for tissue engineered vascular and orthopedic grafts

et al. 2007

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“…The postulated roles of matrix proteins are diverse: a nucleator by providing certain stereochemical arrangement of charged groups, which is sufficient to lower the activation energy barrier for nucleation of a crystal phase (Glimcher, 1989;Gorski, 1992); or an inhibitor by blocking the growth sites through specific adsorption (Moreno et al, 1979;Termine et al, 1980;Romberg et al, 1986) or by providing spacial constraints as exemplified by the lateral growth of apatitic mineral in calcified turkey tendon (Heywood et al, 1990). Casein phosphoproteins in milk, as cited above, act as a stabilizer of amorphous calcium phosphate in nanometer-sized clusters (Holt et al, 1996).…”

Section: Interaction Between Macromolecules and Calcium Phosphatesmentioning

confidence: 99%

The Effect of Fluoride On Apatite Structure and Growth

Aoba

1997

Critical Reviews in Oral Biology & Medicine

189

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Fluoride participates in many aspects of calcium phosphate formation in vivo and has enormous effects on the process and on the nature and properties of formed mineral. The most well-documented effect of fluoride is that this ion substitutes for a column hydroxyl in the apatite structure, giving rise to a reduction of crystal volume and a concomitant increase in structural stability. In the process of enamel mineralization during amelogenesis (a unique model for the cell-mediated formation of well-crystallized carbonatoapatite), free fluoride ions in the fluid phase are supposed to accelerate the hydrolysis of acidic precursor(s) and increase the driving force for the growth of apatitic mineral. Once fluoride is incorporated into the enamel mineral, the ion likely affects the subsequent mineralization process by reducing the solubility of the mineral and thereby modulating the ionic composition in the fluid surrounding the mineral, and enhancing the matrix protein-mineral interaction. But excess fluoride leads to anomalous enamel formation by retarding tissue maturation. It is worth noting that enameloid/enamel minerals found in vertebrate teeth have a wide range of CO3 and fluoride substitutions. In the evolutionary process from elasmobranch through teleost enameloid to mammalian enamel, the biosystems appear to develop regulatory functions for limiting the fluoridation of the formed mineral, but this development is accompanied by an increase of carbonate substitution or defects in the mineral. In research on the cariostatic effect of fluoride, considerable emphasis is placed on the roles of free fluoride ions (i.e., preventing the dissolution and accelerating the kinetics of remineralization) in the oral fluid bathing tooth mineral. Fluoride also has been used for the treatment of osteoporosis, but much still remains to be learned about maximizing the benefit and minimizing the risk of fluoride when used as a public health measure.

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“…This view is also supported by in vitro nucleation experiments, which attempted to simulate the postulated in vivo nucleation substrate of bone tissue by cross-linking the resident phosphoproteins in situ in their native positions and comparing the efficacy (induction or lag time) of this nucleation substrate with samples containing the collagen-phosphoprotein complexes after the covalent phosphate groups were enzymatically cleaved. Not only did the decalcified bone samples containing the collagen-phosphoproteins complexes markedly decrease the nucleation induction time, but this property was lost when the phosphate groups alone were removed enzymatically, leaving the dephosphorylated collagen-phosphoprotein completely intact and, hence, pinpointing the role of the phosphate groups in this in vitro crystal nucleation event (27,28). In addition to their postulated role in calcification, these phosphoproteins have been implicated in many other biological functions (13)(14)(15)(16)29).…”

mentioning

confidence: 99%

Identification of the Phosphorylated Sites of Metabolically 32P-Labeled Osteopontin from Cultured Chicken Osteoblasts

Salih

Ashkar

Gerstenfeld

et al. 1997

Journal of Biological Chemistry

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Osteopontin (OPN) is one of the major secretory phosphoproteins in both calcifying and non-calcifying tissues. Evidence has accumulated for the biological importance of the phosphoproteins and, in particular, the phosphate groups in bone formation, resorption, and calcification. The precise locations of the phosphate groups in the OPN molecule were determined by metabolically labeling OPN with 32 P in cultured chicken osteoblasts, followed by purification to homogeneity. Nterminal sequencing showed a single sequence of WPVSKRQHAISA, consistent with that deduced from both cDNA, and previous amino acid sequencing of the protein isolated from chicken bone. Three 32 P-labeled peptides were isolated by reverse-phase high performance liquid chromatography of thrombin-digested, 32 Plabeled OPN. The N-terminal sequencing of each of these thrombin fragments gave single sequences as follows: WPVSKSRQHAIS, SHHTHRYHQDHVD, and ASKLRKAARKL, with approximate molecular masses of 5, 30, and 20 kDa. These data demonstrate that 32 P was incorporated throughout the N-to C-terminal sequence of the protein. Thrombin specifically cleaved chicken OPN at two sites: between Arg-22 and Ser-23, which generated the 5-kDa N-terminal end fragment, and another between Lys-138 and Ala-139, which generated the 30-and 20-kDa fragments. To further define the exact locations of the phosphorylated amino acids and the surrounding amino acid sequences, OPN was digested with trypsin, which generated seven major 32 P-labeled peptides whose amino acid sequences were determined. The phosphorylated peptide regions of osteopontin were identified as amino acids 8 -18 (QHAIS*AS*S*EEK), -54 (LASQQTHYS*S*EENAD), 150 -171 (LIEDDAT*A-EVGDSQLAGLWLPK), 179 -191 (ELAQHQSVENDSR), 194 -205 (FDS*PEVGGDSK), 214 -219 (ES*LASR), and 2-248 (HSIENNEVTR).The phosphorylated amino acid sites are followed by an asterisk (*). Of the seven identified phosphorylated peptide regions, three were localized on the N-terminal end of the osteopontin molecule (with five phosphorylated serines) and contained the sequence motifs that were phosphorylated by casein kinase II type(s), whereas the remaining four peptides are concentrated toward the C-terminal half of the molecule (with five phosphorylated residues) and contained recognition motifs for other kinases as well as casein kinase II.It has been well established that the processes of phosphorylation and dephosphorylation of proteins catalyzed by protein kinases and phosphatases, respectively, play a major role in the initiation, regulation, and termination of a wide range of intracellular biochemical processes with significant functional consequences. Such processes may also play an important role in a wide variety of intercellular mechanisms, including general cell-cell signal transduction of extracellular agonists via specific transmembrane receptors, often causing alterations of intracellular concentrations of cAMP, calcium, inositol polyphosphates, and/or diacylglycerol. These intracellular modulators in turn induce a cascade of b...

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Mechanism of calcification: Role of collagen fibrils and collagen‐phosphoprotein complexes in vitro and in vivo

Cited by 307 publications

References 72 publications

Structural hierarchy of biomimetic materials for tissue engineered vascular and orthopedic grafts

Structural hierarchy of biomimetic materials for tissue engineered vascular and orthopedic grafts

The Effect of Fluoride On Apatite Structure and Growth

Identification of the Phosphorylated Sites of Metabolically 32P-Labeled Osteopontin from Cultured Chicken Osteoblasts

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