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  • 1
    Electronic Resource
    Electronic Resource
    Perfusion of medium improves growth of human oral neomucosal tissue constructs (2001)
    Oxford, UK : Blackwell Science, Ltd.
    Wound repair and regeneration 9 (2001), S. 0 
    Details
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Tissue engineering of the oral mucosa may be useful in congenital cleft palate repairs, defects following extirpative oncologic surgery, and periodontal disease. One of the limitations of in vitro growth of oral mucosal constructs is central necrosis of 3-dimensional tissues. We tested the hypothesis that medium perfusion would enhance oral mucosal histogenesis in vitro. Normal human oral keratinocytes were obtained from young to middle-aged adults. Porous 3-dimensional matrices were prepared from collagen and chondroitin sulfate with some crosslinked with glutaraldehyde. Each device was seeded with 5.0 × 105 human oral keratinocytes. The seeded matrices were cultured with or without perfusion of medium at 1.3 ml/min. Histologic analysis of samples cultured for 3, 7, or 14 days showed superior viability and proliferation when perfused. At day 7, the average number of cell layers of the neoepithelium of sponges in the perfused culture system (9.4 ± 1.0) was 88% greater than for the nonperfused culture system (5.0 ± 0.9, p〈0.005). Glutaraldehyde crosslinking did not influence cellular proliferation or the extent of matrix's shrinkage in either culture system. This study shows that medium perfusion enhanced cell viability and proliferation of human oral keratinocytes cultured in porous 3-dimensional matrices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1524-475x.2001.00507.x
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  • 2
    Electronic Resource
    Electronic Resource
    Gene expression changes in an in vitro model of chondroinduction: a comparison of two methods (2003)
    Malden, USA : Blackwell Science Inc
    Wound repair and regeneration 11 (2003), S. 0 
    Details
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: There are many useful technologies to describe patterns of gene expression that occur during tissue repair and regeneration. Results from different methods used in one experimental setting are not often compared. In this case study of chondrogenesis, we compare two methods to identify differentially expressed genes, representational difference analysis and targeted macroarray analysis, as a model for investigating genes that may be relevant to tissue repair. We sought to identify genes whose expression was altered when human dermal fibroblasts were cultured in a three-dimensional, porous collagen sponge with the chondroinductive agent, demineralized bone. Both representational difference analysis and macroarray experiments revealed several functional families of genes as up-regulated or down-regulated in chondroinduced fibroblasts. An advantage of representational difference analysis is that altered expression of specific mRNA transcripts can be revealed. In this example, representational difference analysis uncovered the up-regulation of a specific transcript of Wnt5a in fibroblasts cultured with demineralized bone. Representational difference analysis is limited, however, as there can be false negatives for genes not readily amplified by polymerase chain reaction. We conclude that small arrays containing functional classes of genes can be used to ask specific, hypothesis-driven questions at minimal cost. It may be prudent, however, to use more than one method to survey differences in gene expression in order to validate and expand findings. (WOUND REP REG 2003;11:386–392)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1524-475X.2003.11512.x
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  • 3
    Electronic Resource
    Electronic Resource
    Cells of the mononuclear phagocytic system resorb implanted bone matrix: A histologic and ultrastructural study (1982)
    Springer
    Calcified tissue international 34 (1982), S. 488-494 
    Details
    ISSN: 1432-0827
    Keywords: Bone resorption ; Macrophages ; Epithelioid cells ; Giant cells ; Subplasmalemmal linear densities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Implantation of mineral-containing bone fragments into calvarial defects in rats initiates a rapid and reproducible resorption of the bone matrix. After 7 days, a dense tissue develops with mononucleated as well as multinucleated cells surrounding and between the bone fragments. Electron microscopy revealed that these cells belong to the mononuclear phagocytic system; they were identified as macrophages, epithelioid cells, foreign body giant cells, and Langerhans cells. In addition to the common ultrastructural characteristics, these cells had electron-dense, focal specializations along their cell membrane with a coating on the exterior, corresponding to subplasmalemmal linear densities. Small, unidentified cells with electron-dense ground cytoplasm were often seen in close proximity to more differentiated cells. No halisteresis had occurred on the surfaces of the bone fragments. Indentations resembling Howship's lacunae were frequent; these contained mononucleated as well as multinucleated cells. Some surfaces were frayed and collagen fibers were exposed, but the cells apposed to these surfaces did not have ruffled borders as are seen in osteoclasts. Some bone fragments were broken up and cell processes had penetrated deep into the cracks, separating pieces of matrix. Small matrix particles were phagocytosed by macrophages, but not by epithelioid cells or giant cells. It appears that enzymes capable of degrading bone matrix components were secreted by the more differentiated cells of the mononuclear phagocytic system. They eroded the bone surface in a way reminiscent of osteoclastic bone resorption. They also entered the canaliculi to act from within the bone fragment, a process possible only in dead bone. We suggest a possible relationship of these cells with osteoclasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02411290
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  • 4
    Electronic Resource
    Electronic Resource
    Fate of mineralized and demineralized osseous implants in cranial defects (1981)
    Springer
    Calcified tissue international 33 (1981), S. 71-76 
    Details
    ISSN: 1432-0827
    Keywords: Bone matrix ; Induced osteogenesis ; Mineral ; Bone resorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary We have evaluated the fate of mineralized and demineralized osseous implants placed into cranial defects in rats. By 2 weeks, 100% of the defects that had been filled with demineralized bone powder (DBP, 75–250 µm) showed bony repair as judged by histomorphometric analysis and incorporation of45Ca. The DBP was not appreciably resorbed but rather was amalgamated within the new bone. Histomorphometric evaluation of osteogenesis induced by equal masses of demineralized bone powders of various particle sizes (〈75, 75–250, 250–450, 〉450 µm) revealed that the smaller particles induced more bone per field than did the larger particles. In contrast, mineralized bone powder (BP) was completely resorbed by 3 weeks, without bony repair of the cranial defect. These specimens contained large multinucleated cells and connective tissue. Implants of bone minerals were also evaluated. Bone ash and deorganified bone powder were surrounded by multinucleated cells within 7 days and completely resorbed by 3 weeks. It is concluded that (a) demineralized bone powder predictably induces osteogenic healing of cranial defects, (b) demineralized bone powder is not appreciably resorbed prior to bone induction, (c) the extent of bone induction is a function of the surface area of the demineralized bone implant, and (d) mineralized bone powder undergoes obligatory resorption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02409414
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  • 5
    Electronic Resource
    Electronic Resource
    Polyethylene glycol/microfibrillar collagen composite as a new resorbable hemostatic bone wax (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 358-363 
    Details
    ISSN: 0021-9304
    Keywords: bone wax ; hemostasis ; polyethylene glycol ; microfibrillar collagen ; microcrystalline collagen ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Although bone wax is effective at achieving hemostasis, it is nonresorbable, causes a foreign body reaction, and inhibits osteogenesis. We report development of a polyethylene glycol/microfibrillar collagen composite (PEG/MFC) that has inherent hemostatic qualities, is biodegradable, and is compatible with bone repair. PEG/MFC composite (n = 42) was placed in 5 mm cranial defects in New Zealand white rabbits. Hemostasis and healing were compared to unfilled defects (n = 32) and defects filled with standard bone wax (n = 10). Both PEG/MFC and bone wax handled well and stopped bleeding. The polyethylene glycol component was resorbed by 8 h, and the microfibrillar collagen was resorbed over 2 months, eliciting only a minor inflammatory response during the first month. Defects filled with the PEG/MFC composite showed similar amounts of bony regeneration as did unfilled control defects. At 4 weeks, healing bone accounted for 43 ± 13% in those treated with PEG/MFC and 47 ± 19% defect area in untreated holes. In contrast, less than 1% of the area was bone in defects filled with bone wax (p 〈 0.05). PEG/MFC composite provided excellent bony hemostasis and did not inhibit bone growth. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 358-363, 1998.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Osteocalcin promotes differentiation of osteoclast progenitors from murine long-term bone marrow cultures (1994)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 55 (1994), S. 190-199 
    Details
    ISSN: 0730-2312
    Keywords: osteoclast ; osteocalcin ; bone marrow ; differentiation ; resorption ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Murine long-term bone marrow cultures (LTBMCs) were used to generate hematopoietic cells free from marrow stromal cells. These progenitor cells were treated with GM-CSF (5 U/ml) with or without rat bone osteocalcin or rat serum albumin in either α-MEM with 2% heat-inactivated horse serum alone (α) or supplemented with 10% L-cell-conditioned medium (as a source of M-CSF) (L10). Few substrate-attached cells survived in basal α medium, but when treated with L10 medium or GM-CSF, they survived and proliferated. Osteocalcin did not significantly affect survival or proliferation. Subcultures of cells treated with GM-CSF had large numbers of multinucleated cells, more than half of which were tartrate-resistant acid phosphatase-positive (TRAP). Osteocalcin further promoted the development of TRAP-positive multinucleated cells; a dose of 0.7 μg/ml osteocalcin promoted osteoclastic differentiation by 60%. Using a novel microphotometric assay, we detected significantly more tartrate-resistant acid phosphatase activity in the osteocalcin plus GM-CSF group (75.6 ± 14.2) than in GM-CSF alone (53.3 ± 7.3). In the absence of M-CSF, GM-CSF stimulated tartrate-resistant acid phosphatase activity, but osteocalcin did not have an additional effect. These studies indicate that osteocalcin promotes osteoclastic differentiation of a stromal-free subpopulation of hematopoietic progenitors in the presence of GM-CSF and L-cell-conditioned medium. These results are consistent with the hypothesis that this bone-matrix constituent plays a role in bone resorption. © 1994 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240550206
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