摘要:

AbstractInsulin‐like growth factor‐II is known to stimulate the proliferation and differentiation of osteoblasts in part through activation of the type‐2 insulin‐like growth factor receptor. The present study examined the type‐2 insulin‐like growth factor receptors of three normal osteoblast‐like cells and three osteosarcoma‐derived osteoblast‐like cells (OGA, SU, and IMAI) from humans. [125I]insulin‐like growth factor‐II was used for the binding studies. All of the cell types had high affinity binding sites for insulin‐like growth factor‐II (dissociation constants [Kd] ⩽ 1 nM). The concentration of these sites was 10 to 24‐fold higher in normal osteoblasts than in the osteosarcoma cells studied. Unlabeled insulin‐like growth factor‐II inhibited the binding of [125I]insulin‐like growth factor‐II to the cells in a dose‐dependent manner; however, unlabeled insulin‐like growth factor‐I and insulin were less effective. Covalent crosslinking of insulin‐like growth factor‐II binding sites gave molecular mass estimates of Mr250,000 in human osteoblast cells, 250,000 and 130,000 in OGA cells. 240,000 in SU cells, and 250,000 and 130,000 in IMAI cells. Unlabeled insulin‐like growth factor‐II inhibited all affinity labeling. In Northern blot analysis, the type‐2 insulin‐like growth factor receptor mRNA of normal osteoblasts was seen in greater abundance than it was in osteosarcoma cells. These results indicate that the numbers of type‐2 insulin‐like growth factor receptors differ between normal and transformed osteoblasts and that the differential expression of th

ISSN:0736-0266    

DOI:10.1002/jor.1100130502

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA simple and rapid method was established for the cultivation of bone cell tissue. Human bone tissue derived from orthopaedic surgery was cultivated in the presence of14C‐proline and β‐aminopropionitrile.De novosynthesized collagen was extracted from the tissue and quantified by determination of radioactivity in the purified protein. Measurements of the oxygen consumption of the tissue provided evidence that the physiological conditions for the tissue were optimal. The tissue was vital over a period of as long as 7 days, showing normal respiration and a constant rate of collagen synthesis. The observed levels of alkaline phosphatase and acid phosphatase activity clearly demonstrated that mainly osteoblasts were involved in metabolic activity. The described system is suitable for investigations of bone cell metabolism under quasiphysiological condit

ISSN:0736-0266    

DOI:10.1002/jor.1100130503

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractOsteoblast‐like cells have been shown to be sensitive to the proliferative action of a wide variety of growth factors. Many of these growth factors have been isolated from platelets and are thought to be released at local sites in response to injury. In this study, we tested whether human platelet concentrate, as a supplement to basic medium, would support the proliferative and functional activity of human fetal osteoblast‐like cells in both short‐term and long‐term culture. In short‐term studies, uptake of [3H]thymidine was increased in platelet‐treated cultures by more than 4‐fold compared with 10% serum‐supplemented controls. When cultured for prolonged periods on coverslips, the cells formed multilayers, with a collagen‐based matrix separating the layers. Long‐term cultures that were treated with 1.5% (vol/vol) platelets in serum‐supplemented medium showed increases in the depth of the multilayers of as much as 36‐fold at 30 days after confluence, compared with the 10% serum‐supplemented controls; this difference persisted until day 50. Incorporation of growth factor in the matrix was examined with the use of colloidal gold immunoelectron microscopy. Immunogold labeling intensities for transforming growth factor‐β1 were significantly lower in the platelet‐treated cultures at 20 days and then increased to a maximum level of 2.1‐fold more than in the controls at 40 days. Labeling intensities for insulin‐like growth factor‐I and basic fibroblast growth factor were significantly lower in the platelet‐treated cultures than in the controls at all stages of culture. These results indicate that platelet‐supplemented medium stimulates proliferation and maintains the differentiated function of human osteoblast‐like cells. Platelets may play an important role in early healing of fractures and also may be useful as a cheap autologous source of multiple growth factors to enhance

ISSN:0736-0266    

DOI:10.1002/jor.1100130504

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractLimitedin vivoandin vitroexperiments suggest that bone and bone‐like cells respond to mechanical signals in a trigger‐like rather than a dose‐response fashion; i.e., they fail to respond until they have been stimulated with some given number of cycles of loading, and then once they respond, additional cycles produce little or no effect. To explore this notion, rat calvaria‐derived osteoblast‐like cells and the cell line MC3T3‐E1 were plated at a high cell density (5,000 cells/mm2) on silicone membranes coated with type‐I collagen and were allowed to attach for 24 hours. The membranes then were exposed to vacuum pressure (−1 kPa, 0.5 Hz) on a daily basis, and cultures were assayed every 2 days for 2 weeks. The proliferation of nontransformed cells increased 7‐fold with as few as four daily cycles but not with one cycle per day. Furthermore, 1,800 cycles of vacuum did not result in a greater response than four cycles per day. We observed inverse phenotypic responses: the expression of osteocalcin was depressed compared with controls in the cultures of osteoblast‐like cells that were strained with as few as four cycles per day. Alkaline phosphatase activity was depressed in the cultures of both the osteoblast‐like cells and the MC3T3‐E1 cells exposed to low vacuum pressures (−1 kPa) with four daily cycles of vacuum pressure. Increasing the vacuum magnitude did not affect the occurrence of a “trigger response” between one and four cycles of vacuum application. Bone‐like cellsin vitroappear to exhibit trigger‐response behavior analogous to that seen in bonein vivo; the phenotypic response occurs in the opposite directio

ISSN:0736-0266    

DOI:10.1002/jor.1100130505

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractFifteen archival human osteosarcoma specimens were examined byin situhybridization for the expression of human and mouse transforming growth factor‐β (isoforms 1, 2, and 3), c‐fos, and metalloproteinase (stromelysin‐3 and matrilysin). Osteosarcoma subtypes were confirmed by review of patients' radiographs, histopathology, and age at diagnosis. The outcome and method of treatment were documented. The subtypes of osteosarcoma consisted of nine conventional osteosarcomas and two each of fibroblastic, telangiectatic, and post‐radiation osteosarcomas. Each specimen was histologically examined under light microscopy, and then adjacent paraffin sections were assayed with sense and anti‐sense RNA probes byin situhybridization. The probes localized to the neoplastic cells, confirming the methodology of the technique. Human transforming growth factor‐β1 had the most uniform binding affinity to the osteosarcomas examined and was more specific in binding than mouse transforming growth factor‐β1. Specific mRNA encoding for the transforming growth factor‐βs, c‐fos, and metalloproteinases are detectable in patterns within osteosarcoma cells, and collectively, their expression parallels the different histopathologic subtypes. The less differentiated subtypes (telangiectatic and post‐radiation osteosarcomas) expressed the fewest molecular markers. Osteosarcoma is a heterogeneous tumor. Differential expression of matrilysin in osteosarcoma is the first reported detection of metalloproteinase activity in

ISSN:0736-0266    

DOI:10.1002/jor.1100130506

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractErodible polymers are an alternative to metals for fracture fixation (for example, in the malleolus) and for maxillofacial reconstruction. In this study, the vascular response to eroding polylactide‐polyglycolide copolymer threads was observed chronically in a bone chamber implant, with use of intravital microscopy. A bone chamber implant loaded with 100 μm thick polylactide‐polyglycolide threads was implanted into the right tibia in 15 mature female New Zealand White rabbits. Periodic intravital microscopic observations were performed from the third to the tenth or twelfth week after implantation. Vascularization, blood flow, and trabecular growth into the chambers from the medial cortex were recorded on videotape and analyzed using digital image processing. A statistically significant delay of neo‐osteogenesis in the presence of this copolymer was described in an earlier report. The present report describes the measures of neoangiogenesis and blood supply; there was a significant delay in neoangiogenesis. It is suggested that both delayed angiogenesis and osteogenesis were secondary consequences of the macrophage response to slowly eroding poly‐L‐lactide crystal nanoparticles and the influence of reduced nutrient exchange. The lesser effect on blood supply and vascular volume fraction was seen to be linked to the slowing down of angiogenesis, as the latter allowed vessels to mature, with a widening of their calibers. This homeostatic adjustment was interpreted as being only partially successful in restoring control levels of oxygen delivery, because resulting increases in vessel surface area did not reach control levels. Thus, in the presence of eroding polylactide‐polyglycolide, the oxygen supply and extravasation of other nutrients may be below normal during healing phases when the need

ISSN:0736-0266    

DOI:10.1002/jor.1100130507

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractStructural models of long‐bone preparations usually assume left‐right symmetry of contralateral bones under normal (baseline) conditions. To obtain insight on how this assumption affects the detection of subtle changes (as from functional adaptation), we formally examined the three‐dimensional geometric and structural symmetry of paired long bones, using contemporary image reconstruction and stress analysis techniques. Nine pairs of ulnae from normal male turkeys were reconstructed computationally from serial transverse images obtained by either (a) mechanical sectioning and digital photographic imaging or (b) computed tomography. Computed tomography scans allowed greater precision in reconstruction than did digitally imaged photographs. Left‐right comparisons of parameters of geometric symmetry (from computed tomography reconstructions) revealed average differences in whole bone volume and whole bone principal moments of inertia of 3.6 and 3.0%, respectively. Differences in bone curvature were indexed as noncolinearity of left compared with (mirrored) right centroidal axes, giving a disparity of 0.7 ± 0.3 mm. Within the longitudinal central 20% of the diaphysis (the customary region for histomorphometry), average left‐right differences in cross‐sectional area and area principal moments of inertia for computed tomography images were 4.7 and 5.0%, respectively. The overlap of longitudinally paired cross sections of the mid‐diaphysis, aligned at common centroids and oriented in the respective principal inertial directions, was greatest (as much as 95%) in the central 20% of the diaphysis. Paired three‐dimensional finite element models demonstrated nearly identical left and right stress/strain fields throughout the ulnar diaphyses for both compressive and torsional loading. Our data suggest that the assumption of contralateral geometric symmetry in long bones should be judged in the context of the specific attribute of symmetry under consideration; however, we conclude that for purposes of finite element modeling the assumption of symmet

ISSN:0736-0266    

DOI:10.1002/jor.1100130508

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractGrowth, functional adaptation, and torsional strength were examined in the femora of 39‐day‐old male Sprague‐Dawley rats subjected to hindlimb suspension for 0, 1, 2, 3, or 4 weeks and were compared with measurements for age‐matched control animals. Our goal was to understand the effect of reduced loading on the normal age‐related changes in femoral properties during growth. The control animals exhibited growth‐related increases in all geometric and torsional properties of the femur. The mean body mass and femoral length of the hindlimb‐suspended rats were similar to those of the controls throughout the experiment. Over 4 weeks, the femoral cross‐sectional and torsional measurements from the hindlimb‐suspended rats demonstrated increases in comparison with the basal values (+33% cross‐sectional area, +64% polar moment of inertia, +67% ultimate torque, and +181% torsional rigidity), but the age‐matched controls showed significantly greater growth‐related increases (+71% cross‐sectional area, +136% polar moment of inertia, +127% ultimate torque, and +367% torsional rigidity). The differences in femoral structural strength between the hindlimb‐suspended animals and the age‐matched controls were attributable to differences in alt

ISSN:0736-0266    

DOI:10.1002/jor.1100130509

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractStrains induced in the skeleton by functional activity are critical to the homeostasis of bone tissue. Anin vivomodel of disues osteopenia was used to examine whether the removal of these regulatory stimuli induces a uniform loss of crotical bone through the whole organ or whether the loss of bone is focused at specific sites of the cortex. The right radii of five adult male turkeys were isolated from their normal functional loading for 8 weeks. The corresponding left radius from each animal served as an intact contralateral control. An additional group of five turkeys was used as time‐zero controls to assess the initial areal symmetry of the left and right radii. Areal properties were assessed at three sites at equal intervals spanning the middle 3 cm of the diaphysis. Adaptation was determined for each cross section as a whole, as well as specifically by site by division of each cross section into 12 equal angle sectors. The average across all experimental sections after 8 weeks of disuse was 12.1 ± 1.9% (± SE) loss of bone mass. The change in mean cross‐sectional area varied little between the three diaphyseal sites (−10.2 ± 3.3%, −13.5 ± 3.8%, and −12.6 ± 4.0%) and occurred primarily (84%) by uniform expansion of the endosteal envelope. However, elevated intracortical porosity following 8 weeks of disuse was highly nonuniform, with 58% of the increased porosity preferentially located in the ventral/caudal cortex (representing only 25% of the cortical area). From these data, it is concluded that bone responds to the removal of functional stimuli with a uniform, organ‐wide loss of mass, yet intracortical remodeling occurs preferentially within specific areas of the cortex. The lack of spatial coupling between these events suggests that the two processes may be governed by distinct phys

ISSN:0736-0266    

DOI:10.1002/jor.1100130510

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe limited contact dynamic compression plate and partial contact plate were designed to decrease contact with cortical bone in an attempt to decrease cortical ischemia, remodeling, and eventual porosis under the plate after use of standard dynamic compression plates. This study quantified cortical bone blood flow beneath the plate with these three different designs in a sheep tibia fracture model. In 18 skeletally immature sheep, the right tibia was fractured and then was internally fixed with an interfragmentary screw and a dynamic compression plate, limited contact dynamic compression plate, or partial contact plate. At 12 weeks, cortical bone perfusion was assessed with laser Doppler flowmetry in nine areas beneath the plate. The baseline (before fracture) cortical bone cell flux averaged 100 ± 60 mV. After fracture, this decreased to 60 ± 48 mV (p<0.0003); immediately after plating, the perfusion averaged 29 ± 25 mV (p<0.01). Cortical bone perfusion then increased to 106 ± 52, 165 ± 71, and 163 ± 71 mV at 2, 6, and 12 weeks after fracture (p<0.001 for all when compared with values after plating). No significant differences in cortical perfusion were seen between the types of plate. Cortical porosity under the plate was assessed with digital density analysis of microradiographs of this region. No significant difference was seen between the types of plate in this analysis or in biomechanical and disulphine blue perfusion analysis. Thus, no significant advantage was seen for the new plate designs used in this model. This lack of advantage may be a result of the immature animals used in the study, the protocol for blood flow measurement, the invasive periosteal stripping employed to create the fracture, or all three. However, as advantages with the new plate designs have been seen in other studies, this area warrants further investig

ISSN:0736-0266    

DOI:10.1002/jor.1100130511

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY