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At least 613 records · Page 34Linked to original sources
PubMed1987

Effect of bone marrow mononuclear phagocytes on the bone matrix-induced bone formation in rats.

Experimental ulnar bone defects in rats were grafted with freshly isolated whole bone marrow cells; bone marrow mononuclear phagocytes (macrophages); or both types of marrow cell preparations in combination with demineralized bone matrix gelatin (BMG). In the absence of BMG, the osteogenic performance of the marrow cell preparations was superior to that of the macrophages. In the presence of BMG (composite grafts), their osteogenic potential was nearly identical and significantly improved the level of bone formation stimulated by implants of BMG alone. The results encourage speculation and further research on sequential activities of bone marrow monocyte-macrophage (osteoclast) lineages and marrow stromal (osteoprogenitor) cell in bone morphogenetic protein (BMP)-induced regeneration.

Animals↗
PubMed1993

Biochemical changes in the collagen of human osteoporotic bone matrix.

Although it is known that collagen imparts mechanical strength to bone no detailed biochemical analysis has been made of osteoporotic bone collagen. We report for the first time significant changes in the properties of the collagen. Analysis of collagen types revealed little change in the proportion of Type III collagen, but in some cases there was a significant loss of the Type VI. However, the major differences were observed in the post-translational modifications, namely, in the stabilizing cross-links and the hydroxylation of the collagen. These changes indicated a higher turnover in the head region compared to the neck region of the femoral head and are consistent with the susceptibility of the neck region to fracture. Clearly, the collagen is altered in osteoporosis and these changes may play a role in the pathogenesis of the disease.

Aged↗
PubMed2001

Demineralized Bone Matrix-stimulated Bone Regeneration in Rats Enhanced by an Angiogenic Dipeptide Derivate.

A lysyl-proline derivate (LP) known to stimulate angiogenesis and formation of granulation tissue was tested as a local additive to allogeneic demineralized bone matrix (DBM) using a rat craniotomy model. Peracetic-acid sterilized DBM (10 mg/defect) was implanted into three groups of 45 animals each with 0, 6 and 20 microg LP. Subsequent evaluation was done by descriptive histology, histomorphometry, and determination of the calcium content of the explants 7, 14, 28, 42 and 84 days post-implantation. Grafting with DBM alone resulted in defect bridging by newly formed bone with incorporated DBM residues on day 84. Addition of LP to the implants caused an enhanced capillarization on day 14 and 28 as well as an enhanced mineralization on day 14, 28, 42 and 84. Both effects were dose-dependent. These data suggest that the local application of a synthetic angiogenic factor significantly improve bone regeneration in DBM-grafted trephine defects in rats. Thereby, they reinforce the opinion that early angiogenesis is crucial for a number of subsequent events in the bone regeneration process.

Journal Article↗
PubMed2003

[Component analysis of bone matrix via cell extraction].

OBJECTIVE: To investigate the preparation of bone acellular extra-cell matrix(AECM) and to analyze its component. METHODS: With low-osmosis theory and method of cell extraction by detergent, bone acellular extra-cell matrix was prepared. We observed morphologic changes with HE, Mallory-Heidenhain rapid one-step dyeing and Alcian blue dyeing and examined fibronectin(FN) and laminin(LN) with immunohistochemistry. RESULTS: Light microscope showed that the collagen fibers arranged regularly in AECM with blankness of bone lacunas by HE, Mallory-Heidenhain rapid one-step dyeing and that the region around bone lacunas was stained different degrees of blue-green by Alcian blue dyeing. The result of immunohistochemistry showed there are positive markers of FN and LN in ECM. CONCLUSION: This method for preparation of bone acellular extra-cell matrix is effective, and it can keep natural structure of collagen fibers and maintain components of ECM, such as proteoglycan, FN and LN.

Bone and Bones↗
PubMedDate not supplied

Evaluation of decalcified allogenic bone matrix grafts in and around root apices. A histological study.

Decalcified Allogenic Bone grafts were implanted in and around eighteen root apices after apicoectomy. The procedure was carried out on eighteen rabbits, dividing them into three groups of six rabbits each. The animals were sacrificed after 48-72 hours, 8-10 days & 8-10 weeks period of interval. Result of the present investigation reveal that DABM grafts stimulate osteogenesis and cementogenesis after the initial phase of inflammation. Tissues simulating bone and cementum appear at the apical end, speculating that the grafts would certainly result in physiological sealing of root apices. The possibility of saving the life of non vital teeth with or without wide apical foramen will enhance in future.

Animals↗
PubMed2005

Low oxygen tension enhances chondroinduction by demineralized bone matrix in human dermal fibroblasts in vitro.

Endochondral bone formation is induced by demineralized bone powder (DBP) when DBP is implanted subcutaneously in rodents. Previously, we developed an in vitro model of this process, wherein human dermal fibroblasts (hDFs) differentiate to chondrocytes when cultured in a three-dimensional porous collagen sponge containing DBP. In other studies, medium perfusion was beneficial in maintaining phenotype and viability of many cell types in plain porous collagen sponges, including fibroblasts, bone marrow stromal cells, osteoblasts, and epidermal cells. In contrast, medium perfusion inhibited chondrogenesis by articular chondrocytes; reduction of oxygen tension to 5%, however, restored chondrogenesis. These observations are consistent with the fact that in vivo cartilage is avascular and relatively hypoxic compared with other vascularized tissues. In this study, we tested the hypothesis that low oxygen tension (hypoxia, 5% oxygen) would enhance induced chondrogenesis in hDFs cultured with DBP. As expected, hypoxia upregulated hypoxia-inducible factor-1alpha in hDFs in all conditions (i.e. +/- perfusion, +/- DBP). Hypoxia increased accumulation of cartilage-specific matrix chondroitin 4-sulfate in hDFs, but only in the presence of DBP (165%, compared to normoxia, p < 0.05). Hypoxia did not appear to have detrimental effects on cell viability and proliferation. In sum, hypoxia enhanced cartilage matrix accumulation by hDFs cultured with DBP. These defined conditions can optimize the use of dermal fibroblasts for cartilage tissue engineering.

Biocompatible Materials↗
PubMedDate not supplied

Evaluation of processed bovine cancellous bone matrix seeded with syngenic osteoblasts in a critical size calvarial defect rat model.

INTRODUCTION: Biologic bone substitutes may offer alternatives to bone grafting procedures. The aim of this study was to evaluate a preformed bone substitute based on processed bovine cancellous bone (PBCB) with or without osteogenic cells in a critical size calvarial defect rat model. METHODS: Discs of PBCB (Tutobone) were seeded with second passage fibrin gel-immobilized syngenic osteoblasts (group A, n = 40). Cell-free matrices (group B, n = 28) and untreated defects (group C; n=28) served as controls. Specimens were explanted between day 0 and 4 months after implantation and were subjected to histological and morphometric evaluation. RESULTS: At 1 month, bone formation was limited to small peripheral areas. At 2 and 4 months, significant bone formation, matrix resorption as well as integration of the implants was evident in groups A and B. In group C no significant regeneration of the defects was observed. Morphometric analysis did not disclose differences in bone formation in matrices from groups A and B. Carboxyfluorescine-Diacetate-Succinimidylester (CFDA) labeling demonstrated low survival rates of transplanted cells. DISCUSSION: Osteoblasts seeded into PBCB matrix display a differentiated phenotype following a 14 days cell culture period. Lack of initial vascularization may explain the absence of added osteogenicity in constructs from group A in comparison to group B. PBCB is well integrated and represents even without osteogenic cells a promising biomaterial for reconstruction of critical size calvarial bone defects.

Animals↗
PubMed1992

Bone matrix mRNA expression in differentiating fetal bovine osteoblasts.

In the accompanying study, we report an in vitro culture system from bovine bone cells that can be applied to investigate bone cell growth and differentiation. In this system, bovine bone cells placed in mineralization medium formed multilayers (days 2-3), began deposition of mineral (days 5-6), and eventually acquired a mineralized matrix sheet (days 14-20) through the stages of mineralizing nodules and trabecular-like structure. In the current study we used this system to investigate the relative expression of bone matrix genes that may play an important role in bone development and metabolism. alpha 1(I)-collagen, alkaline phosphatase, osteonectin, biglycan (PgI), decorin (PgII), osteopontin, and bone sialoprotein mRNA gene expression were measured on days 0, 2, 6, 10, and 20 (date when the cells were placed in mineralization medium as day 0). Total RNA was purified and analyzed by northern blot using radiolabeled cDNA encoding these genes. To comprehend the relationship between gene expression and mineralization, total calcium content in the cultures was also measured. During the culture period we observed several very different gene expression profiles. The expression of both alpha 1(I)-collagen and biglycan increased 3- to 4-fold by day 6 and then returned to basal levels by day 20. The osteonectin gene was highly expressed throughout the culture, with no significant increase in induction found during any time of culture. A significant induction of alkaline phosphatase (13.8-fold) gene expression was observed by day 6. Osteopontin showed a similar profile to that of alkaline phosphatase but had a much greater level of relative expression (26-fold) compared to day 0. Interestingly, downregulation during mineral accumulation seemed a common occurrence among many of the genes measured. In contrast, the bone sialoprotein gene showed a significant and distinct expression pattern, increasing rapidly after the onset of mineralization on day 6 and ultimately reaching 140-fold that of day 0. Decorin (Pg II) showed an increasing pattern, with the final relative level of induction 5-fold on day 20. These data suggest that the development of the mature osteoblastic phenotype, complete with the ability to produce a thick mineralized matrix, requires the differential regulation of a series of genes and their gene products over the culture period.

Alkaline Phosphatase↗
PubMed2004

Inductive effects of dexamethasone on the gene expression of Cbfa1, Osterix and bone matrix proteins during differentiation of cultured primary rat osteoblasts.

Runx2/core binding factor alpha 1 (Cbfa1) and Osterix (Osx) are osteoblast-specific transcription factors essential for the development of a mature osteoblast phenotype and are thought to activate osteoblast marker genes in vivo to produce a bone-specific matrix. Dexamethasone (Dex) is known to be a potent stimulator of osteoblastic differentiation in vitro, however, the exact role is still unclear. To investigate the mechanisms of the stimulation of osteoblastic differentiation by Dex, we evaluated the effects of Dex on proliferation and mineralization as well as on mRNA expression of Cbfa1, Osx and osteoblast marker genes, osteocalcin (OC) and bone sialoprotein (BSP) mRNAs in differentiating foetal rat calvarial cells (FRCC), which were cultured for 35 days in the presence or absence of 10(-7) M Dex. Treatment of FRCC with Dex resulted in the stimulation of cell proliferation and increased the number of cells, which are able to produce bone-like nodules with a mineralized matrix when compared to untreated controls. Northern blot analysis revealed that, in the absence of Dex, Cbfa1 mRNA expressed at day 8, while Osx mRNA expressed at day 15. Subsequently expression of these mRNAs increased up to day 21, followed by constant expression during the culture period. The expression of OC and BSP mRNAs appeared to be synchronous with that of Osx mRNA and was detectable at day 15 with an increase thereafter. The presence of Dex resulted in an induction in Cbfa1 and Osx mRNA expression. The former appeared at day 5 and the latter appeared at day 11. Subsequently expression of Cbfa1 and Osx mRNAs increased up to day 15 with a decrease thereafter. Expression of OC and BSP mRNAs appeared to be coincident with that of Osx mRNA and was detectable at day 11 and reached a maximum at day 15 followed by constant expression. These observations indicate that induction of Cbfal and Osx mRNAs by Dex may be followed by activation of osteoblast marker genes such as OC and BSP mRNAs to produce a bone-specific matrix that subsequently becomes mineralized. Thus, it is likely that Dex may promote osteoblastic differentiation and mineralization of FRCC by inducing the expression of Cbfa1 and Osx genes in vitro.

Alkaline Phosphatase↗
PubMed1980

Normal maturational changes in bone matrix, mineral, and crystal size in the rat.

Normal rat bone maturation has been studied using biochemical methods and hydrazine separation of matrix and mineral for X-ray diffraction. In the bone, the amount of mineral increases between 4 and 22 weeks of age, while in the matrix, the ratio of noncollagenous protein to collagen progressively decreases. In mineral, in the absence of serum ion changes, growth in mean crystal size appears to be the determinant of the changing ratios of calcium, magnesium, carbonate, and phosphorus, and of the increasing mineral density.

Aging↗
PubMedDate not supplied

Newer knowledge of non-collagenous protein in dentin and cortical bone matrix.

The current state of knowledge of the composition of the NCM components of bone and dentin has been summarized at the end of the appropriate sections. It is significant that increasing interest in the chemistry of hard tissue matrices has coincided with the development and refinement of a wide range of separation techniques, resulting in the isolation of an unexpectedly large number of components. The most sophisticated techniques, such as iso-electric focusing and isotachophoresis, give rise to discrete fractions often of very similar composition, particularly in terms of amino acid content. Such components might best be considered in groups, especially should such groups be identified in terms of common immunochemical properties. Dickson has used such an approach in a recent study of the proteins of sheep cortical bone. The Liverpool group has approached the problem on a broad front and thus directed attention to the number and diversity of NCM components, but it will be seen that those studies directed to the isolation of a specific component have invariably revealed the presence of several other fractions, set aside while attention was directed to the component under investigation. It is clear that the major proportion of bone and dentin NCM consists of glycoproteins of the less-acidic and anionic types. Several of the anionic components contain phosphate, levels being higher in those derived from dentin. Glycosaminoglycans, the first class of non-collagenous compounds to be identified in hard tissue matrices, are now known to comprise only about 5-7 per cent of the NCM. Precise details of the glycosaminoglycan fraction of human dentin and considerable information concerning that of bovine bone are now available. The major component in each tissue is chondroitin-4-sulfate, which exists in the form of proteoglycan, the protein moieties of those from bovine bone and human dentin being very different. Although greater interest is currently being shown in the glycoprotein fractions, several studies have been made of the calcium-binding properties of proteoglycan preparations and of individual glycosaminoglycans. Attempts to relate differences in chemical composition and properties to specific bone sites may not prove to be the best approach to the study of the precise chemistry of mineralization. It is clear, from the earlier work of Lindenbaum and Kuettner that mineralization takes place in a very narrow layer which will normally represent only a fraction of a typical zone prepared for analysis...

Amino Acids↗
PubMed2001

Differential expression of bone matrix regulatory proteins in human atherosclerotic plaques.

In the present study, we examined the expression of regulators of bone formation and osteoclastogenesis in human atherosclerosis because accumulating evidence suggests that atherosclerotic calcification shares features with bone calcification. The most striking finding of this study was the constitutive immunoreactivity of matrix Gla protein, osteocalcin, and bone sialoprotein in nondiseased aortas and the absence of bone morphogenetic protein (BMP)-2, BMP-4, osteopontin, and osteonectin in nondiseased aortas and early atherosclerotic lesions. When atherosclerotic plaques demonstrated calcification or bone formation, BMP-2, BMP-4, osteopontin, and osteonectin were upregulated. Interestingly, this upregulation was associated with a sustained immunoreactivity of matrix Gla protein, osteocalcin, and bone sialoprotein. The 2 modulators of osteoclastogenesis (osteoprotegerin [OPG] and its ligand, OPGL) were present in the nondiseased vessel wall and in early atherosclerotic lesions. In advanced calcified lesions, OPG was present in bone structures, whereas OPGL was only present in the extracellular matrix surrounding calcium deposits. The observed expression patterns suggest a tight regulation of the expression of bone matrix regulatory proteins during human atherogenesis. The expression pattern of both OPG and OPGL during atherogenesis might suggest a regulatory role of these proteins not only in osteoclastogenesis but also in atherosclerotic calcification.

Adult↗
PubMed2001

Estrogen reduces the depth of resorption pits by disturbing the organic bone matrix degradation activity of mature osteoclasts.

Decreased E2 levels after menopause cause bone loss through increased penetrative resorption. The reversal effect of E2 substitution therapy is well documented in vivo, although the detailed mechanism of action is not fully understood. To study the effects of E2 on bone resorption, we developed a novel in vitro bone resorption assay in which degradation of inorganic and organic matrix could be measured separately. E2 treatment significantly decreased the depth of resorption pits, although the area resorbed was not changed. Electron microscopy further revealed that the resorption pits were filled with nondegraded collagen, suggesting that E2 disturbed the organic matrix degradation. Two major groups of proteinases, matrix metalloproteinases (MMPs) and cysteine proteinases, have been suggested to participate in organic matrix degradation by osteoclasts. We show here that MMP-9 released a cross-linked carboxyl-terminal telopeptide of type I collagen from bone collagen, and cathepsin K released another C-terminal fragment, the C-terminal cross-linked peptide of type I collagen. E2 significantly inhibited the release of the C-terminal cross-linked peptide of type I collagen into the culture medium without affecting the release of cross-linked carboxyl-terminal telopeptide of type I collagen in osteoclast cultures. These results suggest that organic matrix degradation is initiated by MMPs and continued by cysteine proteases; the latter event is regulated by E2.

Animals↗