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PubMed1979

Fine structural observations of calcium storage in human dental pulp cells in primary culture.

Primary culture of explants of human dental pulp tissue allows the study of the cytophysiology and differentiation of the cultured cells over a two-week period. The distribution of calcium was found in two different experimental conditions : with and without a calcium loading, by mean of a lead technique checked by microprobe analysis. The existence of two cell populations was revealed. Intra-mitochondrial ring-like granules characterize type 1 cells when overloaded, while a strong calcium storage is detected in the rough endoplasmic reticulum, Golgi apparatus and mitochondrial (without any inner organization of the deposits) of the type 2 cells. Our results also show the presence of calcium on gap-junctions (revealed) by lanthanum method), and on the extracellular matrix (collagen fibres and complex carbohydrates). The ability of some mitochondria to store calcium (ring-like granules) suggests that the type 1 cells are fully differentiated in odontoblast-like cells and perhaps engaged in mineralization processes. The calcium binding sites, localized on the extracellular matrix may therefore be considered as the earliest foci of calcification.

Calcium↗
PubMed1996

Vertebrate mineralized matrix proteins: structure and function.

The mineralized matrices of enamel, cementum, dentin, calcified cartilage and bone are similar in their ability to form a microenvironment that facilitates deposition of hydroxyapatite. However, they are not identical, as witnessed by the nature of apatite crystals that are formed. Enamel is devoid of collagen; and is composed of enamelins, amelogenins, tuftelin and ameloblastin, first described at this meeting. Cementum, dentin and bone matrices are composed primarily of type I collagen, however, each matrix may also contain unique moieties. The exact composition of cementum is not fully known, but in dentin there are unique matrix proteins, phosphophoryn (dentin phosphoprotein, DPP), a distinctive dentin matrix protein (DMP-1), and dentin sialoprotein (DSP). In bone, dentin and cementum, the matrix proteins include proteoglycans (versican, decorin, biglycan) and hyaluronan, glycoproteins which are often phosphorylated and sulfated (osteonectin, RGD-containing proteins) and gla-containing proteins (matrix gla protein, protein S, osteocalcin). The exact nature of all the non-collagenous proteins of calcified cartilage is not yet fully known. While there are no definitive functions for any of the mineralized matrix proteins to date, they most likely participate in regulation of cell metabolism, matrix deposition and mineralization, and bone turnover.

Animals↗
PubMed1976

Interrelations of matrix lipids, vesicles, and calcification.

When calcifying tissues were extracted with hot pyridine or hot benzene and then decalcified and stained with Sudan black B, the areas where mineralization was being initiated stained strongly, the rest of the calcified tissues being unstained. Histochemical methods showed that lipids were responsible for the staining. They were isolated biochemically and found to be phospholipids, very resistant to extraction before decalcification of the tissues and consisting predominantly of phosphatidyl serine and phosphatidyl inositol. It was proposed that these phospholipids were active at nucleating sites in apatite crystal formation, since it is known that phosphatidyl serine binds calcium strongly. It has been shown that phosphatidyl serine is present in matrix vesicles.

Animals↗
PubMed1977

The role of calcitonin in the calcification of ental matrix.

Chronic calcitonin (CT) deficiency was shown to have several effects on the incisors of young growing rats. The incisors had a significantly wider predentin layer, interglobular dentin, and frequent pulpal exposures at the incisal edge. It was concluded that CT plays a role in the normal calcification of dentin matrix.

Animals↗
PubMed1990

The rate of incisor dentine calcification and of mandibular growth in the molar region of the ovariectomized rat.

In 14 ovariectomized and 15 control rats, killed at intervals over a 117-day period, the height of the mandible in the molar region was determined radiographically. Mandibular height was significantly related to time after operation in both groups, but their rate of mandibular growth was not significantly different. In a separate study, the rate of dentine formation in the right mandibular incisor of 9 ovariectomized and 10 control rats was calculated from the distance between two fluorescent labels injected at known time intervals. The rate of dentine apposition was measured at 117 and 201 days after ovariectomy. In both groups, the distance between the fluorescent labels was significantly correlated with the time interval between the injections. There was no significant difference between the rate of dentine calcification in either group. Transient changes in dentine apposition may have occurred post-ovariectomy which would be undetected at either 117 or 201 days after operation. There was thus no evidence for an effect of ovariectomy on either the rate of mandibular growth or dentine apposition.

Animals↗
PubMed1997

Analysis of a general principle of crystal nucleation, formation in the different hard tissues.

We have found, at high EM magnification, on ultrathin sections of shock-frozen, freeze-dried, embedded pieces of the developing hard tissues, that the primary crystallites consist of strands composed of nanometer-sized apatitic islands, which rapidly coalesce to needles and afterward to platelets. By small-area electron diffraction, with energy-filtered electrons, it was clarified that these strands are already crystallographically oriented along the bipolar c-axis so that the center-to-center distances between the islands would reflect the distances between crystal-nucleating sites along the matrix. The EM analysis of the cross-cut stained unmineralized and of the unstained mineralized collagen fibers of turkey tibia tendon shows that the staining "nuclei" and the early crystallites, appearing as dark dots, surround "light" round structures, which we interpret as the collagen microfibrils, surrounded by the apatitic crystallites.

Animals↗
PubMed1998

[The role of basic fibroblast growth factor on expression of mineralization of periodontal ligament cell population and clones].

OBJECTIVE: To determine the effect of basic fibroblast growth factor (bFGF) on mineraliztion of PDL cell clone. METHODS: The PDL tissue that derived from three human donors was cultured and cells were cloned. The mineralizing ability were detected with or without bFGF treatment in the presence of dexamethasone. Cloned progenitor populations were assayed for their constitutive capacity to bind CAP and express ALP. RESULTS: The results show that bFGF increases clone mineralization (11%), but not in PDL cell population. The cell clones that mineralized only in the presence of bFGF have higher CAP binding ability and lower ALP expression compared with other mineralized clone cells. CONCLUSION: bFGF enhances mineralizing expression of PDL clone. The clones that mineralized only with bFGF treatment are different cell types from the bFGF-undependent mineralized clones.

Adult↗