In this study, Computational Fluid Dynamics(CFD) is used to investigate and compare the impact of bioreactor parameters(such as its geometry, medium flow-rate, scaffold configuration) on the local transport phenomena ...In this study, Computational Fluid Dynamics(CFD) is used to investigate and compare the impact of bioreactor parameters(such as its geometry, medium flow-rate, scaffold configuration) on the local transport phenomena and, hence, their impact on human mesenchymal stem cell(hM SC) expansion. The geometric characteristics of the TissueFlex174;(Zyoxel Limited, Oxford, UK) microbioreactor were considered to set up a virtual bioreactor containing alginate(in both slab and bead configuration) scaffolds. The bioreactor and scaffolds were seeded with cells that were modelled as glucose consuming entities. The widely used glucose medium, Dulbecco's Modified Eagle Medium(DMEM), supplied at two inlet flow rates of 25 and 100 μl·h^(-1), was modelled as the fluid phase inside the bioreactors. The investigation, based on applying dimensional analysis to this problem, as well as on detailed three-dimensional transient CFD results, revealed that the default bioreactor design and boundary conditions led to internal and external glucose transport, as well as shear stresses, that are conducive to h MSC growth and expansion. Furthermore, results indicated that the ‘top-inout' design(as opposed to its symmetric counterpart) led to higher shear stress for the same media inlet rate(25 μl·h^(-1)), a feature that can be easily exploited to induce shear-dependent differentiation. These findings further confirm the suitability of CFD as a robust design tool.展开更多
Objective： To demonstrate the validity and reliability of volumetric quantitative computed tomography （vQCT） with multi-slice computed tomography （MSCT） and dual energy X-ray absorptiometry （DXA） for hip bone m...Objective： To demonstrate the validity and reliability of volumetric quantitative computed tomography （vQCT） with multi-slice computed tomography （MSCT） and dual energy X-ray absorptiometry （DXA） for hip bone mineral density （BMD） measurements, and to compare the differences between the two techniques in discriminating postmenopausal women with osteoporosis-related vertebral fractures from those without. Methods： Ninety subjects were enrolled and divided into three groups based on the BMD values of the lumbar spine and/or the femoral neck by DXA. Groups 1 and 2 consisted of postmenopausal women with BMD changes 〈-2SD, with and without radiographically confirmed vertebral fracture （n= 11 and 33, respectively）. Group 3 comprised normal controls with BMD changes 〉-ISD （n-46）. Post-MSCT （GE, LightSpeed16） scan reconstructed images of the abdominal-pelvic region, 1.25 mm thick per slice, were processed by OsteoCAD software to calculate the following parameters： volumetric BMD values of trabecular bone （TRAB）, cortical bone （CORT）, and integral bone （INTGL） of the left femoral neck, femoral neck axis length （NAL）, and minimum cross-section area （mCSA）. DXA BMD measurements of the lumbar spine （AP-SPINE） and the left femoral neck （NECK） also were performed for each subject. Results： The values of all seven parameters were significantly lower in subjects of Groups 1 and 2 than in normal postmenopausal women （P〈0.05, respectively）. Comparing Groups 1 and 2, 3D-TRAB and 3D-INTGL were significantly lower in postmenopausal women with vertebral fracture（s） [（109.8±9.61） and （243.3±33.0） mg/cm^3, respectively] than in those without [（148.9±7.47） and （285.4±17.8） mg/cm^3, respectively] （P〈0.05, respectively）, but no significant differences were evident in AP-SPINE or NECK BMD. Conclusion： the femoral neck-derived volumetric BMD parameters using vQCT appeared better than the DXA-derived ones in discriminating osteoporotic postmenopausal women with vertebral fractures from those without, vQCT might be useful to evaluate the effect of osteoporotic vertebral fracture status on changes in bone mass in the femoral neck.展开更多
基金Department of Engineering Science, University of Oxford, Scholarship
文摘In this study, Computational Fluid Dynamics(CFD) is used to investigate and compare the impact of bioreactor parameters(such as its geometry, medium flow-rate, scaffold configuration) on the local transport phenomena and, hence, their impact on human mesenchymal stem cell(hM SC) expansion. The geometric characteristics of the TissueFlex174;(Zyoxel Limited, Oxford, UK) microbioreactor were considered to set up a virtual bioreactor containing alginate(in both slab and bead configuration) scaffolds. The bioreactor and scaffolds were seeded with cells that were modelled as glucose consuming entities. The widely used glucose medium, Dulbecco's Modified Eagle Medium(DMEM), supplied at two inlet flow rates of 25 and 100 μl·h^(-1), was modelled as the fluid phase inside the bioreactors. The investigation, based on applying dimensional analysis to this problem, as well as on detailed three-dimensional transient CFD results, revealed that the default bioreactor design and boundary conditions led to internal and external glucose transport, as well as shear stresses, that are conducive to h MSC growth and expansion. Furthermore, results indicated that the ‘top-inout' design(as opposed to its symmetric counterpart) led to higher shear stress for the same media inlet rate(25 μl·h^(-1)), a feature that can be easily exploited to induce shear-dependent differentiation. These findings further confirm the suitability of CFD as a robust design tool.
文摘Objective： To demonstrate the validity and reliability of volumetric quantitative computed tomography （vQCT） with multi-slice computed tomography （MSCT） and dual energy X-ray absorptiometry （DXA） for hip bone mineral density （BMD） measurements, and to compare the differences between the two techniques in discriminating postmenopausal women with osteoporosis-related vertebral fractures from those without. Methods： Ninety subjects were enrolled and divided into three groups based on the BMD values of the lumbar spine and/or the femoral neck by DXA. Groups 1 and 2 consisted of postmenopausal women with BMD changes 〈-2SD, with and without radiographically confirmed vertebral fracture （n= 11 and 33, respectively）. Group 3 comprised normal controls with BMD changes 〉-ISD （n-46）. Post-MSCT （GE, LightSpeed16） scan reconstructed images of the abdominal-pelvic region, 1.25 mm thick per slice, were processed by OsteoCAD software to calculate the following parameters： volumetric BMD values of trabecular bone （TRAB）, cortical bone （CORT）, and integral bone （INTGL） of the left femoral neck, femoral neck axis length （NAL）, and minimum cross-section area （mCSA）. DXA BMD measurements of the lumbar spine （AP-SPINE） and the left femoral neck （NECK） also were performed for each subject. Results： The values of all seven parameters were significantly lower in subjects of Groups 1 and 2 than in normal postmenopausal women （P〈0.05, respectively）. Comparing Groups 1 and 2, 3D-TRAB and 3D-INTGL were significantly lower in postmenopausal women with vertebral fracture（s） [（109.8±9.61） and （243.3±33.0） mg/cm^3, respectively] than in those without [（148.9±7.47） and （285.4±17.8） mg/cm^3, respectively] （P〈0.05, respectively）, but no significant differences were evident in AP-SPINE or NECK BMD. Conclusion： the femoral neck-derived volumetric BMD parameters using vQCT appeared better than the DXA-derived ones in discriminating osteoporotic postmenopausal women with vertebral fractures from those without, vQCT might be useful to evaluate the effect of osteoporotic vertebral fracture status on changes in bone mass in the femoral neck.
