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PubMed1989

Osteocalcin-hydroxyapatite interaction in the extracellular organic matrix of bone.

Osteocalcin, a major noncollagenous matrix protein of bone, dentin, and cementum, is found in tight association with the calcium phosphate mineral phase of these tissues. This article reviews the structural data for osteocalcin relevant to mineral adsorption. The equilibrium-binding properties for Ca2+ ions and hydroxyapatite are considered, along with the apparent physicochemical effects of osteocalcin on bone mineral dynamics. Several of osteocalcin's possible biological activities (involvement in mineralization, chemoattraction, and leukocyte elastase inhibition) are discussed in relation to the mineral-adsorption characteristics of this protein.

1-Carboxyglutamic Acid↗
PubMed1991

Xenogeneic osteogenin, a bone morphogenetic protein, and demineralized bone matrices, including human, induce bone differentiation in athymic rats and baboons.

Subcutaneous implantation of xenogeneic demineralized bone matrix does not initiate endochondral bone differentiation. Dissociative extraction in 4 M guanidine-HCl or 6 M urea has shown that the apparent species-specificity of intact bone matrix resides in its insoluble immunogenic component, since there is homology in solubilized osteogenic proteins amongst mammals. To further investigate the species-specificity and cross-species reactivity of bone matrix components, baboon and human demineralized bone matrix (DBM) and bovine osteogenin, purified greater than 50,000-fold and with an apparent molecular mass of 28-42 kilodaltons, were implanted in the subcutaneous space of athymic and euthymic rats and into the rectus abdominis of 16 baboons (Papio ursinus). Baboon DBM was also implanted in athymic and euthymic mice. Alkaline phosphatase activity and histology of implants harvested at day 11 and 30 showed that baboon and human DBM induced endochondral bone differentiation both in athymic rats and baboons. Bovine osteogenin in conjunction with baboon insoluble collagenous matrix induced extensive bone differentiation in athymic rats and baboons. Baboon and human DBM did not induce bone differentiation in euthymic rats and, in athymic mice, baboon DBM failed to induce bone differentiation, determining instead the recruitment of multinucleated giant cells. The results indicate that in rodents bone differentiation induced by intact bone matrix is species specific and that T-cell functions are not a requirement for bone induction, although immunologically competent rats block bone differentiation from xenogeneic matrix. Bone differentiation induced by human DBM in baboons suggests that intact bone matrices may not be species-specific amongst primates.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1997

X-ray pole figure analysis of apatite crystals and collagen molecules in bone.

X-ray pole figure analysis was performed on apatite (AP) crystals in bone mineral and collagen molecules in the bone matrix. For AP in bone mineral, the (0002) plane (c-axis) and {2130} plane were examined. The diffraction peaks from both planes were well isolated from other diffraction peaks in the bone. To investigate the orientation of collagen molecules in the bone matrix, demineralized bone by EDTA treatment was used. For collagen, the diffraction peak from about the 0.3 nm period along the helix axis of the collagen molecule was investigated. The c-axis of AP and the helical axis of the collagen molecule have strongly preferred orientations in a direction parallel to the bone axis. The c-axis of AP has an appreciable pole density peak in the radial and tangential direction of the bone, whereas collagen molecules were almost uniaxially oriented in the bone axis direction though having an appreciable distribution. This suggests that there are more than two types of morphology in the AP particle in bone mineral: one with the c-axis almost parallel to the bone axis and the other in which the c-axis is oriented almost perpendicular to the bone axis. The {2130} plane has isolated peaks of pole density in pole figures in both radial and tangential directions. On the basis of the classification of orientation for elongated polyethylene, the main portion of AP particles in bone is concluded to be biaxially oriented.

Animals↗
PubMed1986

Light and electron microscopic demonstration of osteocalcin antigenicity in embryonic and adult rat bone.

Of the noncollagenous proteins in bone, about 20% consists of osteocalcin. This vitamin K-dependent protein can be found in adult bone, but its presence in embryonic bone could not be demonstrated unequivocally by biochemical methods. Therefore, we used light and electron microscopic immunohistochemical methods to investigate whether osteocalcin antigenicity could be demonstrated in radii of 20-day-old rat embryos. The results show that osteocalcin antigenicity can be demonstrated in the bone matrix of adult bone and in the shaft and endochondral bone matrix of embryonic bone. It could not be demonstrated in calcified cartilage matrix. In bone the antigenicity was observed in the early foci of calcification, i.e., the mineralization nodules.

Animals↗
PubMed2003

Osteoclast ruffled border has distinct subdomains for secretion and degraded matrix uptake.

Subosteoclastic bone resorption is a result of HCl and proteinase secretion through a late endosome-like bone facing membrane domain called ruffled border. As bone matrix is degraded, it enters osteoclasts' transcytotic vesicles for further processing and is then finally exocytosed to the intercellular space. The present study clarifies the spatial relationship between these vesicle fusion and matrix uptake processes at the ruffled border. Our results show the presence of vacuolar H+-ATPase, small GTPase rab7 as well as dense aggregates of F-actin at the peripheral ruffled border, where basolaterally endocytosed transferrin and cathepsin K are delivered. On the contrary, rhodamine-labeled bone matrix enters transcytotic vesicles at the central ruffled border, where the vesicle budding proteins such as clathrin, AP-2 and dynamin II are also localized. We present a model for the mechanism of ruffled border turnover and suggest that, due to its late endosomal characteristics, the ruffled border serves as a valuable model for studying the dynamic organization of other endosomal compartments as well.

Actins↗
PubMed2004

Impaired calcification around matrix vesicles of growth plate and bone in alkaline phosphatase-deficient mice.

The presence of skeletal hypomineralization was confirmed in mice lacking the gene for bone alkaline phosphatase, ie, the tissue-non-specific isozyme of alkaline phosphatase (TNAP). In this study, a detailed characterization of the ultrastructural localization, the relative amount and ultrastructural morphology of bone mineral was carried out in tibial growth plates and in subjacent metaphyseal bone of 10-day-old TNAP knockout mice. Alizarin red staining, microcomputerized tomography (micro CT), and FTIR imaging spectroscopy (FT-IRIS) confirmed a significant overall decrease of mineral density in the cartilage and bone matrix of TNAP-deficient mice. Transmission electron microscopy (TEM) showed diminished mineral in growth plate cartilage and in newly formed bone matrix. High resolution TEM indicated that mineral crystals were initiated, as is normal, within matrix vesicles (MVs) of the growth plate and bone of TNAP-deficient mice. However, mineral crystal proliferation and growth was inhibited in the matrix surrounding MVs, as is the case in the hereditary human disease hypophosphatasia. These data suggest that hypomineralization in TNAP-deficient mice results primarily from an inability of initial mineral crystals within MVs to self-nucleate and to proliferate beyond the protective confines of the MV membrane. This failure of the second stage of mineral formation may be caused by an excess of the mineral inhibitor pyrophosphate (PPi) in the extracellular fluid around MVs. In normal circumstances, PPi is hydrolyzed by the TNAP of MVs' outer membrane yielding monophosphate ions (Pi) for incorporation into bone mineral. Thus, with TNAP deficiency a buildup of mineral-inhibiting PPi would be expected at the perimeter of MVs.

Alkaline Phosphatase↗
PubMed1996

Histomorphological and chemico-physical analyses of the mineral matrix of micropetrotic human bone.

Micropetrotic areas of human bone were analyzed with reference to their distance from blood vessels and to the age of the subjects. Undecalcified bone sections were treated with various solvent, soaking and etching substances to establish the nature of the material occluding the osteocytic canalicular cavities, and were examined by means of microradiographic and microdurimetric methods and X-ray microanalysis to evaluate the degree of mineralization in the bone matrix. Since it was only after strong etching with HCl that the canalicular network became visible under light and scanning electron microscopy, it is clear that the debris filling the canalicular network consists almost entirely of mineral substance. The degree of mineralization of micropetrotic bone is high because it is always a more mature type of bone, but the mineral content of the matrix and the Ca/P ratio do not differ significantly from those of neighbouring bone where the canalicular network is fully pervious.

Adult↗
PubMed1995

Cranioplasty in the growing canine skull using demineralized perforated bone.

This study was designed to test the hypothesis that demineralized perforated bone matrix implant from canine skull and tibia induces new bone formation within the calvarial defect comparable with the bone induced by autogenous graft. We also were interested in determining whether demineralized perforated bone matrix implants from membranous bone have greater osseoinductive capacity in the calvarial area than demineralized perforated bone matrix implants from endochondral bone. Forty 12-week-old purebred beagles were used. Group I consisted of animals with unrepaired surgically created calvarial defects healed by secondary intention (n = 10). Group II consisted of animals with surgically created calvarial defects in which the bone was removed and replaced with an autograft (n = 10). Group III consisted of animals with surgically created calvarial defects in which the bony defect was closed with a demineralized perforated bone matrix implant obtained from beagle calvaria (n = 10). Group IV consisted of animals with surgically created calvarial defects in which the bony defect was closed with a demineralized perforated bone matrix implant obtained from beagle tibia (n = 10). The two control groups (I and II) allowed us to isolate the inductive capacity of demineralized perforated bone matrix implants and compare it with the healing of the bone defects left unrepaired or repaired with calvarial autografts. Animals were sacrificed after 8 and 12 weeks. In the present study we were able to verify that demineralized perforated bone matrix implants are well accepted in the calvarial defects with little tissue reaction and remarkably little osteoclastic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Cartilage resurfacing of the rabbit knee. The use of an allogeneic demineralized bone matrix-autogeneic perichondrium composite implant.

A full-thickness articular-cartilage defect was created in the medial femoral condyles of 32 adult rabbits. The defects were filled with demineralized bone or a composite of demineralized bone and perichondrium. Results of cartilage repair were assessed after 12 weeks of implantation. We conclude that demineralized bone matrix used as a subchondral matrix in a cartilage repair model 1) stimulates and induces subchondral bone ingrowth, 2) provides a surface on which cartilage repair can proceed, and 3) can be utilized as a platform on which perichondrium can be fixed to provide a cellular source for cartilage repair. Repair tissue that developed from perichondrium was thicker, more closely resembled normal articular cartilage, and was of a less fibrous nature than the repair tissue that developed de novo on the demineralized bone matrix.

Animals↗
PubMed1994

IgG monoclonal antibodies that inhibit osteoinductivity of human bone matrix-derived proteins (hBMP/NCP).

Monoclonal hBMP/NCP (human bone morphogenetic protein and associated noncollagenous proteins) antibodies of the IgG class were produced. In vitro, 12 of 19 hBMP/NCP antibodies showed functional inhibition of hBMP/NCP-induced chondroneogenesis in a neonatal muscle tissue assay. Inducing factors were characterized by their inhibiting antibodies with immunoblotting. Several peptide factors seem to be involved in the cascade of induced chondro- and osteogenesis.

Animals↗
PubMed2000

Rapid quantitative bioassay of osteoinduction.

We developed a reproducible, relatively rapid bioassay that quantitatively correlates with the osteoinductive capacity of demineralized bone matrix obtained from human long bones. We have found that Saos human osteosarcoma cells proliferate in response to incubation with demineralized bone matrix and that an index of this proliferative activity correlates with demineralized bone matrix-induced osteogenesis in vivo. The bioassay (Saos cell proliferation) had an interassay coefficient of variation of 23 +/- 2% and an intra-assay coefficient of 11 +/- 1%. Cell proliferation was normalized to a standard sample of demineralized bone matrix with a clinically high osteoinductive capacity, which was assigned a value of one. The Saos cell proliferation for each sample was related to the standard and assigned a value placing it into the low (0.00-0.39), intermediate (0.40-0.69), or high (0.70-1.49) osteoinductive index group. Osteoinduction of human demineralized bone matrix was quantitated by expressing new bone formation as a function of the total bone volume (new bone plus the demineralized bone powder). The demineralized bone matrix was placed in pouches formed in the rectus abdominis muscles of athymic rats, and endochondral bone formation was assessed at 35 days following implantation, when marrow spaces in the ossicles were formed by new bone bridging the spaces between demineralized bone matrix particles. The proliferative index correlated with the area of new bone formation in histological sections of the newly formed ossicles. When the proliferative index (the osteoinductive index) was divided into low, intermediate, and high groups, the correlation between it and new bone formation (osteoinduction) was 0.850 (p < 0.0005) in 25 samples of demineralized bone matrix. There was no overlap in the osteoinduction stimulated between the samples with low and high osteoinductive indices. We conclude that the proliferation assay is useful for the routine screening of bone allograft donors for osteoinductive potential. Furthermore, the two-dimensional area of new bone formation, as it relates to total new bone area, is a quantitative measure of osteoinduction.

Adolescent↗
PubMed2002

The degree of mineralization of bone tissue measured by computerized quantitative contact microradiography.

Strength of bones depends on bone matrix volume (BMV), bone microarchitecture, but also bone mineralization, and we have recently shown in osteoporotic patients treated with alendronate that fracture risk and bone mineral density (BMD) were changed without modifications of BMV or bone microarchitecture. Mineralization of bone matrix implies two successive steps: a rapid primary mineralization on the calcification front followed by a slow process of secondary mineralization progressively adding about one-half of the mineral content on bone matrix. These two steps are clearly illustrated by microradiographs of compact and cancellous bone tissue from transiliac human biopsies. Our working hypothesis is based on the impact of changes in bone remodeling rate on the degree of mineralization of bone, i.e., on the BMD measured at the tissue level. Contact quantitative microradiography using a computerized microdensitometric method, is described and allows the measurement of the mean degree of mineralization of bone (MDMB). This parameter may be quantitatively evaluated by exposing an aluminum calibration step-wedge and a plane-parallel calcified tissue section simultaneously to the same beam of X-rays, then determining, from the resulting microradiograph, the thickness of aluminum that produces the same X-ray absorption as a given region of the bone tissue section. To be used as a control group, iliac bone samples were taken at necropsy from 43 subjects (30 women aged 48.4 +/- 3.7 years and 13 men aged 66.0 +/- 4.4 years) who died suddenly showing no apparent bone disease. A control MDMB, which does not change with age, and a control distribution of these values are thus established. These control values are necessary for interpreting the changes in MDMB observed in bone conditions untreated or treated.

Absorptiometry, Photon↗
PubMed1985

Isolation and characterization of two sialoproteins present only in bone calcified matrix.

Two different sialoproteins were isolated from the mineralized matrix of bovine bone by using extraction with guanidinium chloride first without and then with EDTA. The sialoproteins were purified by chromatography on DEAE-cellulose eluted with a sodium acetate gradient in 7 M-urea, pH 6. Two sialoproteins (I and II) were then separated by chromatography on DEAE-cellulose eluted with a sodium chloride gradient in 7 M-urea, pH 4. The ratio between recovered sialoprotein I and II was 1:5. The chemical analysis of the two sialoproteins showed that they differed. Both, however, had very high contents of aspartic acid/asparagine and glutamic acid/glutamine though they differed markedly in contents of leucine and glycine. Both sialoproteins contained phosphate, sialoprotein I more than sialoprotein II. Content of sialic acid was substantially higher in the more prominent sialoprotein II (13.4% of dry weight) than in sialoprotein I (4.8% of dry weight). The peptide patterns produced by trypsin digests of [125I]iodinated sialoproteins I and II showed both structural similarities and structural differences. Sialoprotein II, being the major component, was characterized further. Its molecular mass was 57300 Da determined by sedimentation-equilibrium centrifugation in 6 M-guanidinium chloride, and its sedimentation coefficient (S0(20),w) was 2.53 S. Upon rotary shadowing, sialoprotein II appeared as an extended rod, having a core with an average length of 40 nm. Two types of oligosaccharides, N-glycosidically and O-glycosidically linked to the core protein, were isolated from sialoprotein II. Contents of mannose and sialic acid in the O-linked oligosaccharide were surprisingly high. Antibodies against sialoprotein II were raised in rabbits and an enzyme-linked immunosorbent assay was developed. Antigenicity of sialoprotein II was not affected by reduction and alkylation, was only partially lost upon trypsin digestion and was completely lost upon fragmentation of the core protein by alkaline-borohydride treatment, indicating that all antigenic sites were located in the protein portion. Sialoprotein I expectedly showed only partial immunological cross-reactivity with sialoprotein II. The quantity of sialoprotein II in bone extracts was found to be about 1.5 mg/g wet wt. of bone, but the protein was not detected in extracts of a number of other bovine tissues i.e. aorta, cartilage, dentine, kidney, liver, muscle, sclera, skin and tendon.

Amino Acids↗
PubMed1995

Transplanted demineralized bone graft in cranial reconstructive surgery.

Surgical reconstruction of cranial deformities and synostosis is occasionally accompanied by incomplete bone growth to cover all areas of cranial vault that have been exposed in the correction. The restrictive nature of some forms of synostosis require more bone in the repair than is available using the child's natural skull for autogenous bone cranioplasty. Rib and iliac crest autografts have been used with success. These grafts must be harvested form a remote site with increased morbidity. A split-thickness skull autograft is the cranioplasty material of choice but children under the age of 6 years may lack the skull thickness needed to use this technique. Perforated demineralized bone matrix has been transplanted in 46 operations in 42 patients from 1990 to 1995 for repair of residual skull defects in children having previously undergone craniofacial repairs, for primary reconstruction of the cranial vault for patients with synostosis and for repair of skull defects resulting from trauma and skull tumor excisions. The vast majority of grafts have resulted in complete closure of the defect, providing a matrix for new bone formation. These patients are presented. Surgical techniques of cranial defect repair with perforated demineralized bone matrix are discussed.

Adolescent↗
PubMedDate not supplied

[Assessment of bovine biomaterials containing bone morphogenetic proteins bound to absorbable hydroxyapatite in rabbit segmental bone defects].

PURPOSE: To evaluate the osteo-regenerative capacity of two proprietary bone grafting materials, using a segmental defect model in both radial diaphyses of rabbits. METHODS: The right defect was filled with pooled bone morphogenetic proteins (pBMPs) bound to absorbable ultrathin powdered hydroxyapatite (HA) mixed with inorganic and demineralized bone matrix and bone-derived collagen, derived from bovine bone (Group A). The left defect was filled with bovine demineralized bone matrix and pBMPs bound to absorbable ultrathin powdered HA (Group B). In both groups, an absorbable membrane of demineralized bovine cortical was used to retain the biomaterials in the bone defects, and to guide the tissue regeneration. The rabbits were euthanized 30, 90 and 150 days after surgery. Radiographic, tomographic and histologic evaluations were carried out on all specimens. RESULTS: At 30 days, the demineralized cortical bone cover was totally resorbed in both groups. HA was totally resorbed from Group A defects, whereas HA persisted in Group B defects. A prominent foreign body reaction was evident with both products, more pronounced in sections from Group B. At 90 days, the defects in Group B exhibited more new bone than Group A. However, at 150 days after surgery, neither treatment had stimulated complete repair of the defect. CONCLUSION: The partial bone healing of the segmental defect occurred with low or none performance of the biomaterials tested.

Animals↗
PubMed1992

Production of matrix metalloproteinases 2 and 3 (stromelysin) by stromal cells of giant cell tumor of bone.

Matrix metalloproteinases play a central role in the catabolism of extracellular matrix macromolecules. Here the authors report that giant cell tumor of bone (GCT) produces two matrix metalloproteinases (MMPs) in zymogen form, which have been identified as proMMP-2 (also known as "72-kDa-progelatinase/type IV procollagenase") and proMMP-3 (prostromelysin). Giant cell tumor is known to consist of two major cell populations, multinucleated giant cells and stromal cells. On several passages of the tumor cells in culture, only stromal cells proliferated. These stromal cells produced proMMP-2 but not proMMP-3. Addition of the conditioned medium of primary GCT culture or human macrophage-conditioned medium to the passaged stromal cells induced the production of proMMP-3. The production of proMMP-3 was also induced by interleukin 1 (IL-1), but not by tumor necrosis factor alpha (TNF alpha). ProMMP-1 (tissue procollagenase) was not detected even after treatment with these stimuli. Immunohistochemical studies have demonstrated that multinucleated giant cells in GCT both produce IL-1 and TNF alpha, suggesting that IL-1 secreted by multinucleated giant cells may be responsible for in vivo production of proMMP-3 by the stromal cells. The authors propose that GCT has a self-stimulatory system for the production of matrix-degrading proteinases and that the ability of the passaged stromal cells to synthesize and secrete proMMP-3 with appropriate stimuli may contribute the malignant behavior of GCT.

Adult↗
PubMed1987

Mechanism of fibroblast attachment to bone extracellular matrix: role of a 44 kilodalton bone phosphoprotein.

While the exact mechanisms regulating bone homeostasis are unknown, it is generally accepted that factors with the capacity to regulate cell attachment and spreading play a role in osteogenesis. A 44 kDa bone phosphoprotein (44K BPP), isolated from rat bone and synthesized by osteoblasts, was evaluated for its role in attachment and spreading of fibroblasts. In uncoated plates, enhanced cell attachment and spreading were observed when fibroblasts were exposed to the 44K BPP. The attachment properties of the bone phosphoprotein are different from those of fibronectin, in that the 44K BPP did not promote cell attachment in type I collagen wells, as was seen with fibronectin. Also, 44K BPP continued to enhance cell attachment up to 24 h, whereas cell attachment declined in time with cells exposed to fibronectin. Cycloheximide did not alter 44K BPP promotion of cell attachment, indicating that de novo protein synthesis was not required. These studies suggest that the 44K BPP is important in the regulation of cell attachment and spreading at sites of mineralization.

Bone and Bones↗