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PubMed1992

Structure, expression, and regulation of the major noncollagenous matrix proteins of bone.

The noncollagenous proteins (NCPs) that predominate the bone matrix have recently been the focus of intense investigation because of their potential influence on cell attachment, Ca2+ and hydroxyapatite binding, and the mineralization of bone tissue. With the advent of molecular biology, all of the major NCPs of bone have been cloned and their amino acid sequences completely determined. While each of the proteins has distinct structural properties, some proteins appear to be part of gene families. Examples include the small proteoglycans, decorin and biglycan, as well as the gamma carboxyglutamic acid proteins, such as matrix gla protein and osteocalcin (bone gla protein). Some of the NCPs that are clearly not members of any known gene family still share several common characteristics. One such example of this "convergent evolution" is bone sialoprotein and osteopontin. Both are highly posttranslationally modified glycoproteins that share the cell attachment amino acid sequence RGD (arginine-glycine-aspartic acid), which facilitates the attachment of bone cells in vitro, yet they are clearly not related genetically. Using cDNAs and antisera as probes, the precise temporal localization of NCP expression has been determined, and it has been shown that NCPs are produced in skeletal, and in most cases, nonskeletal tissue as well. This observation implies that the functions of the NCPs are not necessarily limited to bone tissue. Many of the promoters for these genes have been isolated and functional domains determined by a combination of chloramphenicol acetyltransferase assay, gel shift, and footprint analyses. The most extensively studied promoter in the NCP category is osteocalcin, whose sensitivity to 1,25-dihydroxycholecalciferol has been delineated in detail. Future studies on the individual and cooperative activities of the NCPs in bone are likely to involve site-directed mutagenesis of cloned DNA and a combination of in vitro and in vivo functional analyses.

Biglycan↗
PubMed2003

Comparison of bone grafts for posterior spinal fusion in adolescent idiopathic scoliosis.

STUDY DESIGN: A retrospective comparison of three different types of bone grafts for posterior spinal fusion in adolescent idiopathic scoliosis. OBJECTIVE: To determine the efficacy of bone marrow and demineralized bone matrix as a bone graft substitute for spinal fusion. SUMMARY OF BACKGROUND DATA: Several reports have documented a high morbidity associated with harvesting autologous iliac crest bone graft (ICBG) for spinal fusion. Composite bone graft consisting of demineralized bone matrix and aspirated bone marrow may reduce the morbidity and still retain the osteoinductive properties of iliac crest autograft. METHODS: Three different bone grafting techniques were used by a single surgeon in 88 consecutive patients who had posterior spinal fusion for adolescent idiopathic scoliosis. Segmental instrumentation with dual-rod fixation was used in all cases. Selection of type of graft was determined historically by the time when the operations were performed. Autologous ICBG was used in Group A, freeze-dried corticocancellous allograft in Group B, and composite graft of autologous bone marrow and demineralized bone matrix in Group C. Seventy-seven patients were reviewed, with a minimum of 2 years' follow-up (mean, 3 years 7 months; range, 2 years-9 years 5 months). Radiographs were assessed for pseudarthrosis and loss of correction of 10 degrees or more. Loss of 10 degrees of correction has been previously identified as an indicator of potential pseudarthrosis or fusion instability. Both of these criteria were used to compare success of fusion. RESULTS: Failure caused by pseudarthroses was seen in two patients (2.6%), one in Group A and one in Group B. Eleven patients lost greater than 10 degrees of correction, but only one demonstrated pseudarthroses. The 13 patients with pseudarthroses or loss of correction constitute the failure group for purposes of graft assessment. The failure rate was 12.5% in Group A (ICBG), 28% in Group B (freeze-dried corticocancellous allograft), and 11.1% in Group C (composite graft of autologous bone marrow and demineralized bone matrix). Eliminating patients with crankshaft phenomenon did not substantially change the results. There was no morbidity associated with bone marrow aspiration. CONCLUSIONS: Fusion rates were comparable for GroupA (ICBG) and Group C (composite graft of autologous bone marrow and demineralized bone matrix). The composite graft is our preferred graft for fusions in adolescent idiopathic scoliosis.

Adolescent↗
PubMed1988

Isolation, partial purification and in vitro characterization of osteogenic inhibitory protein.

A noncollagenous protein has been extracted and partially purified from adult cortical bone. This protein copurifies with another bone matrix protein, bone morphogenetic protein, until treatment with nonionic detergents. Characterization of the biological activity of this new protein has demonstrated it to be a potent osteogenic inhibitor in vitro. The inhibitor antagonizes the chondrogenic activity of devitalized, demineralized bone matrix as well as the activity of soluble bone morphogenetic protein. Bone matrix induced collagen and glycosaminoglycan synthesis are both inhibited in the presence of various concentrations of the osteogenic inhibitory protein. Inhibition of collagen synthesis required the presence of osteogenic inhibitory protein from the initiation of the tissue culture while glycosaminoglycan synthesis could be inhibited at any stage of differentiation. We postulate that this osteogenic inhibitory protein is essential in normal homeostatic bone metabolism, perhaps acting directly on bone morphogenetic protein.

Animals↗
PubMed1994

Effect of poly DL-lactide--co-glycolide implants and xenogeneic bone matrix-derived growth factors on calvarial bone repair in the rabbit.

Polymer implant discs composed of 50:50 poly DL-lactide-co-glycolide (molecular weight about 9000) were used to repair 5 mm calvarial defects in 2 kg rabbits and osseous repair compared to spontaneous healing (control). After 4 weeks the implants had undergone substantial degradation with little evidence of residual polymer. The extent to which the defects had been replaced by bone showed individual variation. In some animals a layer of bone with normal cancellous architecture had bridged the defect, but at no time was bone observed in intimate contact with the polymer matrix, suggesting that the material had acted as a tissue spacer rather than an osteoconductive substrate. Non-osseous tissue consisted of a highly vascular fibrous connective tissue containing variable numbers of inflammatory cells. In some sites numerous macrophages and multinucleate giant cells were observed, the majority of which were shown by immunocytochemistry to be MHC class II-positive. Histomorphometric analysis demonstrated no statistically significant difference in osseous repair between control and polymer implant groups after 1, 2 or 3 months. Incorporation of bone matrix proteins extracted from bovine cortical bone into the discs, however, provoked a cellular and humoral immune response which had a significant inhibitory effect on osseous repair. These data suggest, first, that while synthetic polymers have potential as bone graft substitutes, improvements in their performance in vivo are needed and, second, it is advisable to use allogeneic proteins in rabbit models of bone regeneration.

Animals↗
PubMed1983

Identification of a bone matrix-derived chemotactic factor.

When demineralized bone matrix powder is implanted subcutaneously in the rat, the early responses involve the appearance and proliferation of mesenchymal cells at the site of implantation, followed by cartilage and bone formation. The ability of cells to migrate to the implant suggests that chemotaxis may be a critical event in this process. Therefore, using the modified Boyden chamber assay, we tested extracts of demineralized bone matrix for chemotactic activity. We have identified and partially purified, on molecular sieve chromatography, a heat labile and trypsin-sensitive protein (Mr = 60,000-70,000) that is a potent chemoattractant for mouse calvaria, osteoblast-like cells (MMB-1), but not for monocytes (putative osteoclast precursors). These findings suggest that chemotactic protein(s) have a significant role in the recruitment of osteoprogenitor cells to a site of bone repair.

Bone Matrix↗
PubMed1989

The influence of fibrin sealant on demineralized bone matrix-dependent osteoinduction. A quantitative and qualitative study in rats.

Allogeneic demineralized bone matrix (DBM) and bone matrix gelatin (BMG) were implanted with or without fibrin sealant (FS) ectopically (abdominal wall) and orthotopically (7-mm trepanation defect) in 38 male Sprague-Dawley rats. Evaluation was done by descriptive histology, histomorphometry of orthotopic implants, and determination of alkaline phosphatase in ectopic implants. The observation period was 21 days with ectopic implantation and 26 days with orthotopic implantation. In all ectopic specimens, new bone developed without any qualitative difference between specimens with and without FS. The alkaline phosphatase activity did not change significantly upon addition of FS. Morphometry revealed slight differences between the groups with and without FS. The peripheral bone deposits in the BMG + FS group, was significantly larger than in the BMG group. These investigations demonstrated neither a clearly positive nor negative effect of FS on ectopic osteoinduction or BMG-dependent osteoregeneration.

Alkaline Phosphatase↗
PubMed1995

Aging and matrix microdamage accumulation in human compact bone.

Bone matrix microdamage in bone matrix, evidenced as microcracks, occurs consequent to cyclic loading. Microdamage caused by in vivo loading has been described in human rib cortex; however, the existence and extent of microcracks in human long bone cortices are largely unknown. Using histomorphometric methods to examine the incidence and localization of microcracks in human femoral compact bone specimens, we found that the amount of microdamage present in femoral compact bone increases dramatically with increasing age. Least squares regression analysis showed that in males, microcrack density (Cr.De., #/mm2) increases exponentially with age (r2 = 0.70). In females, Cr.De. also increases as an exponential function of increasing age (r2 = 0.79), at a significantly higher rate than in male specimens (p < 0.001). The current studies indicate that with increasing age, bone microdamage accumulates more rapidly than intrinsic processes can effect its repair. A combination of cumulative loading history, focal changes in material properties and alteration in the ability of the tissue to perceive and/or react to microcracks may all play role in this accumulation of bone microdamage with aging. This accumulation of microdamage in bone will contribute to decreased strength and stiffness. In addition, and perhaps most significantly for understanding aging and increased bone fragility, matrix microdamage in composite materials like bone will result in a profoundly reduced resistance to fracture. The importance of this accumulation of matrix microdamage in human bone with increasing age in contributing to the increased fragility of the aging skeleton is discussed.

Adolescent↗
PubMed1998

The correlation between immune rejection and osteoinduction of allogeneic bone grafting.

OBJECTIVE: To evaluate the relationship between the immune rejection and the osteoinductive potential of bone allograft. METHODS: Allogeneic and syngeneic fresh bone, autolyzed antigen-extracted bone, bone matrix gelatin and demineralized bone matrix were implanted into the muscle of mice, and immunological tests, histological observation and alkaline phosphatase assay were performed. RESULTS: Three and 6 weeks after implantation, all kinds of allogeneic implants activated immune rejection, among them, fresh bone induced the most vigorous immune rejection and bone matrix gelatin caused the weakest response. Allogeneic autolyzed antigen-extracted bone, bone matrix gelatin and demineralized bone matrix inhibited proliferation of the lymphocytes in vitro and bone matrix gelatin had the most powerful inhibiting effect. Both allogeneic and syngeneic autolyzed antigen-extracted bone, bone matrix gelatin, and demineralized bone matrix induced heterotopic osteogenesis in vivo and bone matrix gelatin had the best osteoinductive capacity. CONCLUSION: There is a negative correlation between immune rejection to bone allograft and osteoinductive capacity of the graft.

Animals↗
PubMed1986

Effects of bisphosphonates on the incorporation of calcium-45 and 3H-proline in orthotopic and in demineralized matrix-induced bone in rats.

The influence of the two bisphosphonates, 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) and dichloromethylene bisphosphonate (Cl2MBP), on bone formation was studied in demineralized matrix-induced bone in young rats. Cl2MBP was given in doses of 0.3 and 3 mg P/kg per day and HEBP 2,4, and 8 mg P/kg per day starting immediately after implantation of the bone matrix and continued until sacrifice at 3 weeks. Rates of collagen synthesis and mineralization of implants, femurs, and incisor teeth were quantified by assay of 3H-proline and 45Ca injected 24 h before death. New bone formation in implants was also evaluated by histologic examinations. Implants from Cl2MBP-treated animals had wider bone trabeculae than controls but were colonized by normal appearing hematopoietic tissue. Implants and femurs from both Cl2MBP groups had a higher ash content than controls, but uptake of the two isotopes was not affected. These results indicate that Cl2MBP, at these dose levels, inhibits bone resorption without affecting bone formation in rats. The uptake of 45Ca in implants decreased with increasing doses of HEBP; almost no ash or 45Ca activity was encountered with the highest dose. The bone in implants from this group appeared less mature, and only scanty areas of bone marrow were seen. The uptake of 3H-proline was not affected by HEBP. It appears that, in rats, HEBP primarily inhibits mineralization and resorption, whereas matrix formation remains largely unaffected.

Animals↗
PubMed1984

Bone morphogenetic protein-induced cartilage development in tissue culture.

Outgrowths of mesenchyme-type cells from explants of allogeneic rat muscle onto a substratum of bone matrix containing bone morphogenetic protein (BMP) differentiate into cartilage. When BMP is chemically extracted from the bone matrix, the explanted cells develop only into fibrous tissue. When exogenous bovine BMP is introduced into the culture medium, either as a microsuspension or as a layer of particles between the matrix and the muscle cell tissue, cartilage develops at the interface between the matrix and the mesenchymal cell outgrowth. The chondrogenetic response is induced by as little as 2 micrograms of BMP; the optimum dose is 10 micrograms/40 mg (wet weight) of explant. The endogenous BMP equivalent for a comparable chondrogenetic response is about 0.6 micrograms/mg of allogeneic matrix. The minimum time for transfer of BMP to mesenchymal cell receptors is 1.0 hour, adequate time is 2.5 hours, and optimum time is approximately 5.0 hours. Measured in terms of incorporation of 3H-thymidine into DNA and of 35S sulfate into glycosaminoglycan, there is a latent period of one to three days preceeding the differentiation of mesenchyme-type cells into cartilage. During this latent period BMP-modulated mesenchymal cells disaggregate, migrate, reaggregate, and proliferate on new surfaces and constitute the morphogenetic phase of bone development. By the fourth day cells simultaneously undergo mitotic division, synthesize extracellular cartilage matrix, and establish the cytodifferentiation phase of development.

Animals↗
PubMed1983

Matrix constituents of early developing bone examined by freeze fracture.

Specimens of aldehyde-fixed and glycerol-impregnated early developing bone matrix, obtained from rat calvaria, were examined by the freeze-fracture method. The developing bone matrix reveals collagen fibrils, numerous membranous structures and a granular background. The collagen fibrils, when viewed longitudinally, exhibit a substructure of thinner filaments (microfibrils) which appear to follow a twisted course along the fibril-axis. Some of the membranous structures are readily identified as osteoblast processes. Others, which are round, ovoid or irregular in shape, were found either with or without intramembrane particles (IMPs). It is concluded that the round or ovoid IMP-containing membranous structures correspond to matrix-vesicles. The nature of the IMP-free bodies, however, is uncertain. They may be artefacts or genuine matrix-vesicles deriving from unstable membrane domains which have a propensity for blebbing or budding off. Confirmation of the latter possibility might come from examination of directly frozen specimens.

Animals↗
PubMed1999

Growth hormone and the expression of mRNAs for matrix proteins and oncogenes in bone.

To examine the effects of growth hormone (GH) on the expression of the mRNAs of bone matrix proteins, three experiments were carried out with 3-month-old female Sprague-Dawley rats. In the first experiment rats were given a single subcutaneous injection of recombinant human GH (8 mg rhGH/kg b. wt.), sacrificed 15 min, 1 h, 2 h, 4 h, 8 h, 16 h and 24 h later, and RNA isolated from cancellous bone from the distal femoral metaphysis. Growth hormone increased the level of type I collagen mRNA by 187, 417, and 509% over the control level at 15 min, 1 h and 2 h, respectively; the mRNA levels declined to 119 and 99% at 4 and 8 h, respectively, and then rose again to 351 and 423% over the control level at 16 and 24 h, respectively. Osteocalcin mRNA transcript increased by 89, 90, 325, 342, 361, and 407% over the control level at 15 min, 1 h, 2 h, 4 h, 8 h and 16 h, respectively, and fell to 66% at 24 h. The level of IGF-I mRNA increased by 45, 83, 120, 140, and 175% over the control level at 2, 4, 8, 16, and 24 h, respectively. In the second experiment, following the administration of rhGH (8 mg/kg b. wt.) bone osteocalcin mRNA increased by 127, 177, 361, and 413% over the control level at 30 min, 1 h, 2 h and 4 h, respectively; IGF-I mRNAs increased by 38, 33, 87, and 437 at 30 min, 1 h, 2 h and 4 h, respectively, but the levels did not become significant until 2 h; c-fos mRNA increased significantly at 30 min, and c-jun and c-myc mRNAs did not increase until 4 h. In the third experiment, animals were given a single injection of rhGH (8 mg/kg b. wt.) and the animals were bled at timed intervals and acid ethanol-extractable serum IGF-I determined. Serum IGF-I increased significantly only at 12 h following rhGH administration. Our data indicate that GH stimulates a rapid increase in the expression of mRNAs for the bone matrix proteins, type I collagen and osteocalcin, by a mechanism that appears to be independent of IGF-I, the early response oncogenes or an increase in osteoblast number.

Animals↗
PubMed1979

Changes in proline synthetic and degradative enzymes during matrix-induced cartilage and bone formation.

Proline biosynthetic and degradative enzymes are unevenly distributed in differentiated mammalian tissues. Activities of the synthetic enzymes are relatively high in collagenous tissues, whereas activities of the degradative enzymes are high in noncollagenous tissues. In order to further characterize tissue-specific proline biosynthesis and degradation, we have determined proline enzyme activities during cartilage and bone formation induced by demineralized bone matrix. We can thus follow temporal changes in enzyme activity in a single tissue as different cell types develop. Ornithine aminotransferase and pyrroline-5-carboxylate reductase have peaks of activity which correlate with maximal type II collagen synthesis by chondrocytes. Both enzymes also are active during bone formation. In contrast, proline oxidase and pyrroline-5-carboxylate dehydrogenase are present at low levels and do not change as new cell types appear. Arginase activity peaks during the first 3 days and then rapidly decreases by the time cartilage and bone formation begin. These observations further substantiate the importance of proline biosynthesis in collagenous tissues. The close correlation between ornithine aminotransferase activity and type II collagen synthesis suggests that the pathway from ornithine to proline may be especially important during formation of type II collagen.

Animals↗
PubMed1981

Changes in intracellular enzymes of collagen biosynthesis during matrix-induced cartilage and bone development.

The activities of five intracellular enzymes of collagen biosynthesis were determined during cartilage and bone formation induced in rats by demineralized bone matrix. The five enzymes, prolyl 4-hydroxylase, prolyl 3-hydroxylase, lysyl hydroxylase, hydroxylysyl galactosyltransferase and galactosyl-hydroxylysyl glucosyltransferase, exhibited broadly parallel profiles; the activities rising steeply from day one to reach their highest values on day nine and decreasing gradually thereafter. The maximal enzyme activity correlated with the period of chondrogenesis and hypertrophic cartilage characterized by the synthesis of cartilage-specific type II collagen. Prolyl 4-hydroxylase was also studied in respect of its tissue distribution and cellular location using indirect immunofluorescence. The enzyme was mainly located in the mesenchymal cells on day three, in the chondrocytes and hypertrophic chondrocytes on days seven to nine, and in the osteoblasts on day eleven and thereafter.

Animals↗
PubMed2005

Effects of osteoprotegerin administration on osteoclast differentiation and trabecular bone structure in osteoprotegerin-deficient mice.

Osteoprotegerin (OPG)-deficient mice exhibit severe bone loss including the destruction of growth plate cartilage. Using OPG-deficient mice, we attempted to clarify the differentiation and ultrastructure of osteoclasts located on the destroyed growth plate cartilage and trabecular bone matrix in long bones. In (-/-) homozygous OPG knockout mice, adjacent to the growth plate cartilage, the formation of bone trabeculae without a calcified cartilaginous core resulted in an irregular chondrocyte distribution in the growth plate cartilage. At the metaphyseal ossification center, TRAP-positive osteoclasts showed unusual localization on both type-II collagen-positive cartilage and type-I collagen-positive bone matrix. Osteoclasts located on cartilage matrix lacked a typical ruffled border structure, but formed resorption lacunae. During growth plate cartilage destruction, osteoclasts formed ruffled border structures on bone matrix deposited on the remaining cartilage surfaces. These findings suggest that, in OPG (-/-) mice, osteoclast structure differs, depending on the matrix of either cartilage or bone. Then, we examined the effects of OPG administration on the internal trabecular bone structure and osteoclast differentiation in OPG (-/-) mice. OPG administration to OPG (-/-) mice significantly inhibited trabecular bone loss and maintained the internal trabecular bone structure, but did not reduce the osteoclast number on bone trabeculae. For most osteoclasts, OPG administration caused disappearance or reduction of the ruffled border, but induced neither necrotic nor apoptotic damages. These results suggest that OPG administration is an effective means of maintaining the internal structure and volume of trabecular bone in metabolic bone diseases by inhibition of osteoclastic bone resorption.

Acid Phosphatase↗
PubMed1993

Distribution of noncollagenous proteins in the matrix of adult human bone: evidence of anatomic and functional heterogeneity.

The microanatomic distribution of several noncollagenous proteins (NCPs) in bone matrix was examined by immunohistochemical analysis of glycol-methyl methacrylate-embedded normal adult human bone biopsies. Osteopontin and bone sialoprotein stained throughout the lamellae of both trabecular and cortical bone. Cement lines (cortical and trabecular) and the mineralized matrix immediately adjacent to each Haversian canal were intensely stained. Osteocalcin was detected in cement lines; however, lamellar staining varied depending on the location within the individual unit of bone. In cortical bone, the inner concentric lamellae of osteons were often unstained but the outer lamellae were heavily stained for osteocalcin. Osteonectin was not detected in cement lines and in most specimens revealed a pattern similar to that of osteocalcin with respect to the absence of immunostaining within the inner concentric lamellae. Decorin was prominent in the perilacunar matrix, the canaliculi of osteocytes, and the matrix immediately adjacent to quiescent Haversian canals. Biglycan appeared evenly distributed throughout cortical and trabecular bone matrix. These results suggest that the incorporation of NCPs into matrix may vary depending on the stage of formation of individual bone units. The specific distribution and spatial relationship of these NCPs may be related to the function of each protein during bone resorption and formation. The distinct patterns of NCP localization in bone support the hypothesis that in addition to their structural and mineral-inducing properties, these proteins may influence the events associated with bone remodeling, such as recruitment, attachment, differentiation, and activity of bone cells.

Adult↗