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Objective To investigate the effect of a new biomaterial combining calcium citrate and recombinant human bone morphogenetic protein-2 (rhBMP-2) on bone regeneration in a bone defect rabbit model. Methods Totally 30 male New Zealand white rabbits were randomly and equally divided into calcium citrate-rhBMP-2 (CC-rhBMP-2) group and rhBMP-2 only group. Two 10 mm-long and 5 mm-deep bone defects were respectively created in the left and right femoral condyles of the rabbits. Subsequently 5 pellets of calcium citrate (10 mg) combined with rhBMP-2 (2 mg) or rhBMP-2 alone were implanted into the bone defects and compressed with cotton swab. Bone granules were obtained at 2, 4 and 6 weeks after procedure and received histological analysis. LSD /-test and a subsequent /-test were adopted for statistical analysis. Results Histomorphometric analysis revealed newly formed bones, and calcium citrate has been absorbed in the treatment group. The percent of newly formed bone area in femoral condyle in control group and CC-rhBMP-2 group was respectively 31.73%±L26% vs 48.21%±2.37% at 2 weeks; 43.40%±1.65% vs 57.32%±1.47% at 4 weeks, and 51.32%±7.80% vs 66.74%±4.05% at 6 weeks (P<0.05 for all). At 2 weeks, mature cancellous bone was observed to be already formed in the treatment group. Conclusion From this study, it can be concluded that calcium citrate combined with rhBMP-2 signifcantly enhances bone regeneration in bone defects. This synthetic gelatin matrix stimulates formation of new bone and bone marrow in the defect areas by releasing calcium ions. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the in vitro and in vivo osteogenic capability of adipose-derived stromal cells (ASCs).Methods: ASCs were isolated from New Zealand white rabbits and determined by alkaline phosphatase (ALP) staining, von Kossa staining and alizarin red staining. Some specific markers of osteogenic differentiation, including ALP, osteocalcin (OCN), osteopontin (OPN) were examined by reverse transcription-polymerase chain reaction (RT-PCR). In vivo, demineralized bone matrix (DBM)-ASCs composites were implanted into the rabbit calvarial defects created at each side of the longitudinal midline. After 6 weeks, histologic properties of the transplants were analyzed.Results: ASCs were successfully induced into osteogenesis. ALP staining, von Kossa staining and alizarin red staining showed positive results. The expressions of ALP, OCN and OPN were detected in ASCs after cultivation in osteogenic medium. Extensive new bone was observed in the defects transplanted with DBM-ASCs composites.Conclusion: ASCs have the potential to differentiate into osteogenic lineage and DBM-ASCs constructs are a promising method for regeneration in bone defects. [ABSTRACT FROM AUTHOR]

A boundary layer theory for buckling and postbuckling of anisotropic laminated thin shells is extended to shear deformable stiffened anisotropic laminated shells. A postbuckling behavior is investigated for a shear deformable anisotropic laminated cylindrical shell with geodesical stiffener of finite length subjected to lateral or hydrostatic pressure. The material of each layer of the shell is assumed to be linearly elastic, anisotropic, and fiber-reinforced. The governing equations are based on a higher-order shear deformation shell theory with von Kármán-Donnell-type of kinematic nonlinearity and including the extension/twist, extension/flexural, and flexural/twist couplings. The nonlinear prebuckling deformations and initial geometric imperfections of the shell are both taken into account. A singular perturbation technique is employed to determine the buckling pressure and postbuckling equilibrium paths. The numerical illustrations concern the postbuckling response of perfect and imperfect, moderately thick, geodesically stiffened shells, axial and ring stiffened shells, and unstiffened shells with different values of shell parameters and stacking sequence. The results confirm that there exists a circumferential stress along with an associate shear stress when the shell is subjected to lateral pressure. The postbuckling equilibrium path is stable for the moderately long shell under external pressure and the shell structure is virtually imperfection-insensitive. [ABSTRACT FROM AUTHOR]