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PubMedDate not supplied

[Formation of an organic matrix in the traction method of bone regeneration and characteristics of its mineralization in experimental tibia lengthening].

Stretching of dog crus was carried out using transbone distractional osteosynthesis method by Ilizarov. Distribution of calcium, phosphorus and organic substances in zones of regenerating tissue was studied within 1 and 2 months after stretching and within 2 months after the subsequent fixation of the leg in the apparatus. Zones of non-mineralized osteoids were not found already during destruction. In the zones content of minerals varied only slightly and the less mineralized middle zone contained about 66% of calcium and phosphorus as compared with their level in mature compact bone tissue. Crystals of hydroxyapatite were found in zones close to bone fragments using electron microscopy. The data obtained suggest that under optimal conditions of regeneration provided by the method the newly formed bone matrix is partially mineralized during its synthesis. Reverse correlation was detected between contents of minerals and glycosaminoglycans. Middle zones with a slightly higher concentration of glycosaminoglycans were less mineralized. Within 2 months after stopping of distraction differences between zones were decreased, content of glycosaminoglycans was lowered as minerals accumulated; content of minerals became higher than in spongy bone tissue but slightly lower as compared with compact bone.

Animals↗
PubMed1991

A comparison of four particulate bone derivatives.

Samples of four types of particulate bone matrix derivatives were prepared and surgically inserted into standardized critical-sized defects in calvariae of Long-Evans rats. Implantation of demineralized bone matrix (DBM), bone regenerative matrix, and two types of particulate chemosterilized, antigen-extracted, autolyzed, allogeneic (AAA) bone from endochondral (eAAA) and intramembranous (iAAA) sources will result in the regeneration of bone in orthotopic skull defects. The four preparations were tested in orthotopic, 8-mm calvarial wounds to compare the quantity of new bone that formed 28 days postimplantation. Quantitative computer imaging was used to measure roentgenographic gray levels and bone volume of new trabeculae (calcified plus osteoid). All experimental bone matrix derivatives produced more bone volume than the nontreated control wounds. Bone volume regenerated from iAAA was significantly less than eAAA and DBM-regenerated bone.

Analysis of Variance↗
PubMed2005

Measurement of estrogen effect on bone turnover by 2H2O labeling.

Estrogen loss has been known to increase bone turnover through accelerated bone resorption coupled by increased bone formation. In the present study, we measured estrogen effect on bone turnover by incorporation of 2H from 2H2O into amino acids. At 6 weeks of age, rats were either sham-operated (sham) or ovariectomized (ovx). Two weeks after surgery, 17beta-estradiol (est) was implanted subcutaneously to ovx rats. At 9 weeks of age, 2H2O labeling started by administration of 4% 2H2O to rats for 4 or 7 weeks in drinking water after a single intraperitonial bolus injection with 99.9% 2H2O. Body 2H2O enrichments were stable at approximately 3.0% over labeling period. Fractional replacements (f) of the midshaft femur were higher in the sham group (40.36 +/- 4.89% vs 42.47 +/- 11.22%) than the ovx (28.57 +/- 9.67% vs 37.47 +/- 8.34%) and est (26.57 +/- 4.00% vs 30.35 +/- 5.34%) groups 4 and 7 weeks after labeling, respectively. Ovariectomy-induced bone loss was observed in the trabecular bone along with a significantly increased number of osteoclasts, all of which were normalized after estradiol treatment. Taken together, our results indicate that estrogen deficiency significantly reduces the proportion of newly synthesized bone matrix as well as the total amount of bone matrix. The reduced portion of new matrix in ovx rats, presumably caused by activated osteoclastic degradation, was compensated rapidly with time. In addition, estradiol treatment protected the bone matrix by decreasing bone turnover rate.

Alanine↗
PubMed1986

Effect of ethane-1-hydroxy-1,1-diphosphonate on ectopic bone formation induced by murine osteosarcoma-derived bone-inducing substance.

The effects of ethane-1-hydroxy-1,1-diphosphonate (EHDP) on ectopic bone formation were studied qualitatively and quantitatively in an experimental system for ectopic bone formation induced by murine osteosarcoma-derived bone-inducing substance. At a low dose of EHDP (3 mg/kg per day i.p.), histologic sequelae of ectopic bone formation were normal, and the size of the induced bone mass was unaffected. At a high dose of EHDP (30 mg/kg per day i.p.), an unmineralized bone matrix with hematopoietic bone marrow was formed without evidence of retardation. This osteoid tissue showed no radiologic and histologic evidence of mineralization during the period of EHDP administration. When EHDP was withdrawn, its inhibitory effect on mineralization was reversed. The induced bone mass was almost the same size as that in controls. These results suggest that EHDP might not prevent ectopic bone matrix formation, but its mineralization and withdrawal of EHDP might lead to the formation of a normal bone similar in size to that formed without EHDP treatment.

Animals↗
PubMed1989

A study of the mechanical strength of long bone defects treated with various bone autograft substitutes: an experimental investigation in the rabbit.

This study was designed to determine which of several bone grafting materials would be the most efficacious substitute for autogenous bone graft in the treatment of segmental long bone defects. The experimental model was a 1-cm defect in the rabbit ulna. The control group had nothing implanted in the defect. The six grafts tested were: (a) autogenous iliac crest bone, (b) autogenous cortical bone (ulna), (c) hydroxylapatite, (d) hydroxylapatite-demineralized bone matrix (allograft) composite graft, (e) freeze-dried bone (allograft), and (f) demineralized bone matrix (allograft). At 6 weeks postoperatively, the ulnas were harvested, examined radiographically, and tested mechanically in torsion. The radiographic examination proved to be of little value because some materials were radiodense at the time of implantation. The rates (percentage) of union, torques at failure, and energy to failure values were statistically significantly higher than control for all groups except hydroxylapatite. We concluded that demineralized bone matrix and hydroxylapatite-demineralized bone matrix composite graft compare favorably with cortical replacement (autograft) in mechanical strength and rate of union and therefore may be satisfactory substitutes for bone grafting. Freeze-dried bone did not appear to be as satisfactory because of its low mean energy to failure, but statistical analysis failed to confirm this opinion. Hydroxylapatite graft, when used alone, does not appear to be a suitable material for grafting segmental bone defects.

Animals↗
PubMed2001

Temporal and spatial gene expression of major bone extracellular matrix molecules during embryonic mandibular osteogenesis in rats.

It is not known how gene expression of bone extracellular matrix molecules is controlled temporally and spatially, or how it is related with morphological differentiation of osteoblasts during embryonic osteogenesis in vivo. The present study was designed to examine gene expressions of type I collagen, osteonectin, bone sialoprotein, osteopontin, and osteocalcin during mandibular osteogenesis using in situ hybridization. Wistar rat embryos 13-20 days post coitum were used. The condensation of mesenchymal cells was formed in 14-day rat embryonic mandibles and expressed genes of pro-alpha 1 (I) collagen, osteonectin, bone sialoprotein and osteopontin. Cuboidal osteoblasts surrounding the uncalcified bone matrix were seen as early as in 15-day embryonic mandibles, while flat osteoblasts lining the surface of the calcified bone were seen from 16-day embryonic mandibles. Cuboidal osteoblasts expressed pro-alpha 1(I) collagen, osteonectin and bone sialoprotein intensely but osteopontin very weakly. In contrast, flat osteoblasts expressed osteopontin very strongly. Osteocytes expressed the extracellular matrix molecules actively, in particular, osteopontin. The present study demonstrated the distinct gene expression pattern of type I collagen, osteonectin, bone sialoprotein, osteopontin and osteocalcin during embryonic mandibular osteogenesis in vivo.

Animals↗
PubMed2005

Modeling deformation-induced fluid flow in cortical bone's canalicular-lacunar system.

To explore the potential role that load-induced fluid flow plays as a mechano-transduction mechanism in bone adaptation, a lacunar-canalicular scale bone poroelasticity model is developed and implemented. The model uses micromechanics to homogenize the pericanalicular bone matrix, a system of straight circular cylinders in the bone matrix through which bone fluids can flow, as a locally anisotropic poroelastic medium. In this work, a simplified two-dimensional model of a periodic array of lacunae and their surrounding systems of canaliculi is used to quantify local fluid flow characteristics in the vicinity of a single lacuna. When the cortical bone model is loaded, microscale stress, and strain concentrations occur in the vicinity of individual lacunae and give rise to microscale spatial variations in the pore fluid pressure field. Furthermore, loading of the bone matrix containing canaliculi generates fluid pressures in the contained fluids. Consequently, loading of cortical bone induces fluid flow in the canaliculi and exchange of fluid between canaliculi and lacunae. For realistic bone morphology parameters, and a range of loading frequencies, fluid pressures and fluid-solid drag forces in the canalicular bone are computed and the associated energy dissipation in the models compared to that measured in physical in vitro experiments on human cortical bone. The proposed model indicates that deformation-induced fluid pressures in the lacunar-canalicular system have relaxation times on the order of milliseconds as opposed to the much shorter times (hundredths of milliseconds) associated with deformation-induced pressures in the Haversian system.

Animals↗
PubMed1995

Comparative study of bone marrow induced by purified BMP and recombinant human BMP-2.

Into a calf muscle pouch in Wistar rats, 50 micrograms purified bone morphogenetic protein (pBMP) or 50 micrograms recombinant human bone morphogenetic protein-2 (rhBMP-2) was implanted using atelopeptide type I collagen solution (CL) as a carrier. Three weeks later bone and bone marrow were induced in both groups. These induced bone and bone marrow were studied histologically. In the pBMP+CL group (n = 5), rich bone matrix and little bone marrow were observed. There was no fatty marrow or angioid tissue observed. In the rhBMP-2+CL group (n = 5), bone matrix and rich marrow including fatty marrow and angioid tissue were observed around and among the bony trabeculae. It was suggested that a "self-supporting bone organ" was induced.

Animals↗
PubMedDate not supplied

Variations in bone regeneration adjacent to implants augmented with barrier membranes alone or with demineralized freeze-dried bone or autologous grafts: a study in dogs.

A study was performed in two large hound dogs to evaluate the bone-induction potential of demineralized freeze-dried bone (DFDBA) placed into defects adjacent to implants that were placed into extraction sockets. Two implants were untreated controls, two implants received only Gore-Tex Augmentation Membrane (GTAM), two implants received GTAM and autologous bone, and six sites received GTAM and DFDBA. DFDBA was prepared from the long bones of a dog of the same breed as the experimental dogs. P2, P3, and P4 were extracted bilaterally, and buccal defects were created and measured. Twelve commercially pure titanium Brånemark implants were placed. At 12 weeks, clinical measurements were taken and the dogs were sacrificed. The untreated control defects had a mean clinical bone fill of 1.75 mm (37%). Sites treated with autologous bone had a mean of 5.0 mm (95%) of clinical bone fill within the original defects. Sites treated with DFDBA and barriers had 3.8 mm (75%) of bone fill, while sites treated with membranes alone had a mean of 4.2 mm (80%) of bone fill. Histologic evaluation revealed that DFDBA sites had retained nonviable bone chips in 45.4% of the bone matrix, and only 8.3% was lamellar bone. Autologous graft sites had 26.2% retained bone chips within the bone matrix, and 61% percent of the matrix consisted of lamellar bone. For GTAM-only sites, 70.2% of the matrix was lamellar bone and 29.8% was woven bone. Retained DFDBA bone chips were nonviable, occasionally surrounded by woven bone, and appeared to break up and then remineralize without the presence of osteoclastic or osteoblastic activity. Retained autologous bone chips were surrounded and incorporated by the host bone. The autologous bone grafts and DFDBA implants were considered to be osteoconductive. For the three treatment groups, within the defects there were sparse bone-implant contacts. The results indicate that GTAM barriers alone or with autologous bone grafts produced the best clinical and histologic results. DFDBA did not appear to induce bone formation in any of the evaluated specimens.

Alveolar Process↗
PubMed2000

Bone morphogenetic protein excipients: comparative observations on poloxamer.

Clinicians await the availability of synthetic bioimplants that will replace the need for autogeneic bone grafts in bone reconstructive surgery. For more than a decade, researchers have evaluated delivery vehicles for the tissue morphogen bone morphogenetic protein. The object of this investigation was to measure induced bone development when bone morphogenetic protein was delivered by human tendon collagen, human demineralized bone matrix, hydroxyapatite, a composite of human tendon collagen and human demineralized bone matrix (tendon collagen + demineralized bone matrix), Poloxamer 407, and a composite of human demineralized bone matrix and Poloxamer 407. Sixty-three adult male Swiss Webster mice (Harlan Sprague-Dawley, Indianapolis, Ind.) received 126 implants. The animals were divided into seven groups of nine animals, depending on carrier (six carriers plus the positive control group) used. Each animal received a bone morphogenetic protein-enhanced carrier in one hindquarter muscle mass, with the contralateral leg being implanted with the carrier alone. Implants were evaluated by quantitative radiomorphometry validated by histologic methods. Radiographically, no significant differences were identified among any of the implants evaluated (p > 0.05). Histomorphometric analysis demonstrated that Poloxamer 407 was significantly (p < 0.05) better at delivering bone morphogenetic protein than the other carriers involved in this investigation. The new bone developed in a tubular or spherical shape. Interaction of endogenous and exogenous delivery systems seems to be essential for optimal transmission of bone morphogenetic protein. The importance of the excipient to deliver bone morphogenetic protein and develop a bone morphogenetic protein concentration gradient has been emphasized by other investigators and confirmed by our research on poloxamer. With further research on the physicochemical mechanisms of localization and transmission of bone morphogenetic protein, it may be possible to avoid hazardous operations with autogeneic bone.

Animals↗
PubMed1977

Pathogenesis of osteopetrosis in the microphthalmic mouse: reduced bone resorption.

Bone resorption, stimulated by injection of parathyroid extract, was measured in vivo in microphthalmic mice as the rate of release of 3H from bone after incorporation of 3H-proline. Bone resorption in these mice, which inherit osteopetrosis, was less than 10% of the in normal litermates. Autoradiography confirmed the reduction in removal of radioactive bone matrix and in bone growth in microphthalmic mice. The ability of these mice to raise the serum calcium concentration in response to PTE was also reduced. These results, that bone resorption is reduced in microphthalmic mice, are discussed in relation to the pathogenesis and cure of the disease.

Animals↗
PubMed2006

Bioabsorbable scaffold for in situ bone regeneration.

A non-porous poly-DL-lactide tubular chamber filled by demineralised bone matrix (DBM) and bone marrow stromal cells (BMSC) in combination, was evaluated as a scaffold for guided bone regeneration (GBR) in an experimental model using the rabbit radius. The tubular chamber had an internal diameter of 4.7 mm, a wall thickness of 0.4 mm and a length of 18 mm. Autologous BMSC were obtained, under general anaesthesia from rabbit iliac crest and isolated by centrifugation technique. Allogenic DBM was obtained from cortico-cancellous bone of rabbits. In general anaesthesia, a 10-mm defect was bilaterally created in the radii of 10 rabbits. On the right side (experimental side) the defect was bridged with the chamber filled with both BMSC and DBM. On the left side (control side) the defect was treated by positioning DBM and BMSC between the two stumps. At an experimental time of 4 months histology and histomorphometry demonstrated that the presence of a tubular chamber significantly improved bone regrowth in the defect The mean thickness of newly-formed bone inside the chamber was about 56.7+/-3.74% of the normal radial cortex, in comparison with 46.7+/-10.7% when DBM and BMSC without the chamber were placed in the defect, P<0.05). These results confirmed the effectiveness of the chamber as a container for factors promoting bone regeneration.

Absorbable Implants↗
PubMed2003

Making bone: implant insertion into tissue-engineered bone for maxillary sinus floor augmentation-a preliminary report.

Autologous, allogenic and alloplastic materials for bony reconstruction in the cranio-maxillofacial area have many drawbacks thus stimulating the on-going search for new (bio-)materials. Whereas cultivated skin and mucosa are already in clinical routine use in head and neck reconstruction, so far there has been no successful clinical application to the best of our knowledge of periosteum-derived, tissue-engineered bone for augmentation of the edentulous posterior maxilla. In a pilot study, augmentation of the posterior maxilla was carried out using a bone matrix derived from mandibular periosteal cells on a polymer fleece. This paper demonstrates fabrication of the matrix, clinical application, and the histological results in two patients. The results suggest that periosteum-derived osteoblasts on a suitable matrix form lamellar bone within 4 months which allows reliable implant insertion.

Alveolar Ridge Augmentation↗
PubMed2001

Selective delivery of estradiol to bone by aspartic acid oligopeptide and its effects on ovariectomized mice.

We have developed a novel osteotropic prodrug of estradiol (E(2)) conjugated with L-Asp-hexapeptide (E(2).3D(6)), which has very low affinity for estrogen receptors, and in this study, we examined its pharmacokinetic behavior and pharmacological potential. After a single iv injection of E(2) x 3D(6) to mice, the half-time for elimination from plasma was about 100 min; however, E(2) was selectively delivered to the bone and eliminated very slowly, declining to the endogenous level at about 7 days. After a single iv injection of E(2), the half-time in plasma was about 70 min, whereas E(2) was highly distributed to the uterus, and the bone concentration of E(2) was only slightly increased at 6 h. When E(2) (0.37 micromol/kg, sc, every third day) or E(2) x 3D(6) (0.11 to 1.1 micromol/kg, sc, every seventh day) was administered to OVX mice for 4 weeks, E(2) increased the bone mineral density (BMD) together with weights of liver and uterus, whereas E(2) x 3D(6) increased only the BMD, in a dose-dependent manner. E(2) x 3D(6) enhanced the expression of messenger RNAs of bone matrix proteins (osteopontin, bone sialoprotein, type I collagen alpha) of OVX mice at 4 h after administration, but E(2) did very slightly. These results indicate that the E(2) prodrug was delivered to the bone, where it gradually released E(2), thereby ameliorating bone loss. This acidic oligopeptide appears to be a good candidate for selective drug delivery to bone.

Animals↗
PubMed1994

Qualitative and quantitative comparative study on different filling materials used in bone tissue regeneration: a controlled clinical study.

This study compared, in a human model, the ability of (1) expanded polytetrafluorethylene (e-PTFE) membranes plus bone-chip autografts, (2) e-PTFE membranes plus demineralized freeze-dried bone, (3) e-PTFE membranes plus a new form of demineralized allograft bone tissue, and (4) e-PTFE membranes alone to enhance bone regeneration around dental implants placed into recent extraction sockets. The histologic results demonstrated that, in humans, guided tissue regeneration techniques are capable of producing new bone osseointegrated with titanium dental implants. Among the graft materials, autogenous bone provided the densest and the greatest amount of bone formation, but use of demineralized freeze-dried bone and a new form of de-mineralized allogenic bone matrix also improved bone regeneration compared to membranes alone after 6 months of healing.

Alveolar Bone Loss↗
PubMed1988

Chondrogenesis and osteogenesis of bone marrow-derived cells by bone-inductive factor.

Rat bone marrow cells were intraperitoneally implanted within a diffusion chamber with a decalcified bone matrix or a 4 M guanidine hydrochloride extracted matrix (G-res) as control. The chamber was harvested after 28 days and soft X-ray photography, histological examination, determination of alkaline phosphatase activity and calcium content were performed. With the decalcified bone matrix, cartilage and bone formation was observed and both alkaline phosphatase activity and calcium content were significantly higher than those in control chambers. Each chromatographic fraction on Sephacryl S-200 of the 4 M guanidine hydrochloride extract (G-ext) from the decalcified bone matrix was reconstituted with G-res and implanted either subcutaneously or intraperitoneally within a diffusion chamber with marrow cells. Intrachamber or subcutaneous cartilage and bone formation was detected by only one chromatographic fraction. When marrow-derived fibroblast-like cells were implanted intraperitoneally within a diffusion chamber with a decalcified bone matrix, cartilage and bone formation was detected, which was not the case with G-res. These results suggest that a certain factor, probably bone morphogenetic protein, which induces ectopic bone formation, allows marrow cells to differentiate into bone and cartilage tissues and there may exist so-called "inducible osteoprogenitor cells" in the marrow-derived fibroblast-like cell preparation.

Animals↗
PubMed2005

Degradation of the organic phase of bone by osteoclasts: a secondary role for lysosomal acidification.

UNLABELLED: Osteoclasts degrade bone matrix by secretion of hydrochloric acid and proteases. We studied the processes involved in the degradation of the organic matrix of bone in detail and found that lysosomal acidification is involved in this process and that MMPs are capable of degrading the organic matrix in the absence of cathepsin K. INTRODUCTION: Osteoclasts resorb bone by secretion of acid by the vacuolar H+-adenosine triphosphatase (V-ATPase) and the chloride channel ClC-7, followed by degradation of the matrix, mainly collagen type I, by cathepsin K and possibly by matrix metalloproteinases (MMPs). However, the switch from acidification to proteolysis and the exact roles of both the ion transporters and the proteinases still remain to be studied. MATERIALS AND METHODS: We isolated CD14+ monocytes from human peripheral blood from either controls or patients with autosomal dominant osteopetrosis type II (ADOII) caused by defective ClC-7 function and cultured them in the presence of RANKL and macrophage-colony stimulating factor (M-CSF) to generate osteoclasts. We decalcified cortical bovine bone slices and studied the osteoclasts with respect to morphology, markers, and degradation of the decalcified matrix in the presence of various inhibitors of osteoclast acidification and proteolysis, using normal calcified bone as a reference. RESULTS: We found that ADOII osteoclasts not only have reduced resorption of the calcified matrix, but also 40% reduced degradation of the organic phase of bone. We found that both acidification inhibitors and cathepsin K inhibitors reduced degradation of the organic matrix by 40% in normal osteoclasts, but had no effect in the ADOII osteoclasts. Furthermore, we showed that inhibition of MMPs leads to a 70% reduction in the degradation of the organic bone matrix and that MMPs and cathepsin K have additive effects. Finally, we show that osteoclastic MMPs mediate release of the carboxyterminal telopeptide of type I collagen (ICTP) fragment in the absence of cathepsin K activity, and therefore, to some extent, are able to compensate for the loss of cathepsin K activity. CONCLUSIONS: These data clearly show that osteoclastic acidification of the lysosomes plays a hitherto nonrecognized role in degradation of the organic matrix. Furthermore, these data shed light on the complicated interplay between acidification dependent and independent proteolytic processes, mediated by cathepsin K and the MMPs, respectively.

Adult↗
PubMed1988

Accumulation, localization, and compartmentation of transforming growth factor beta during endochondral bone development.

Endochondral bone formation was induced in postnatal rats by implantation of demineralized rat bone matrix. Corresponding control tissue was generated by implanting inactive extracted bone matrix, which did not induce bone formation. At various times, implants were removed and sequentially extracted with guanidine hydrochloride, and then EDTA and guanidine hydrochloride. Transforming growth factor beta (TGF beta) in the extracts was quantitated by a radioreceptor assay. TGF beta was present in demineralized bone matrix before implantation, and the concentration had decreased by 1 d after implantation. Thereafter, TGF beta was undetectable by radioreceptor assay until day 9. From day 9-21 the TGF beta was extracted only after EDTA demineralization, indicating tight association with the mineralized matrix. During this time, the content of TGF beta per milligram soluble protein rose steadily and remained high through day 21. This increased concentration correlated with the onset of vascularization and calcification of cartilage. TGF beta was detected only between days 3-9 in the controls; i.e., non-bone-forming implants. Immunolocalization of TGF beta in bone-forming implants revealed staining of inflammatory cells at early times, followed later by staining of chondrocytes in calcifying cartilage and staining of osteoblasts. The most intense staining of TGF beta was found in calcified cartilage and mineralized bone matrix, again indicating preferential compartmentalization of TGF beta in the mineral phase. In contrast to the delayed expression of TGF beta protein, northern blot analysis showed TGF beta mRNA in implants throughout the sequence of bone formation. The time-dependent accumulation of TGF beta when cartilage is being replaced by bone in this in vivo model of bone formation suggests that TGF beta may play a role in the regulation of ossification during endochondral bone development.

Animals↗