Jaw-Lin Wang

Magnetic nanoparticle labeling of mesenchymal stem cells without transfection agent: Cellular behavior and capability of detection with clinical 1.5 T magnetic resonance at the single cell level

The purpose of this work was to evaluate the efficacy of labeling human mesenchymal stem cells (hMSCs) by ionic superparamagnetic iron oxide (SPIO) without a transfection agent and verifying its capability to be detected with clinical 1.5 T magnetic resonance (MR) at the single‐cell level. Human hMSCs were incubated for 24 h with an ionic SPIO, Ferucarbotran. The labeling efficiency of hMSCs was determined by iron content measurement spectrophotometrically, and the influence of labeling on cell behavior was ascertained by examination of cell viability using the trypan blue exclusion method, cell proliferation analysis using MTT (3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay, mitochondrial membrane potential (MMP) change, differentiation capacity, and reactive oxygen species (ROS) production measured by dichlorofluorescein diacetate (DCFDA) fluorescent probe. Labeled hMSCs were scanned under 1.5 T MRI with three‐dimensional (3D) and two‐dimensional (2D) T2‐weighted gradient echo (GRE) pulse sequences. Human hMSC labeling without transfection agent was efficient. The iron content in hMSCs was 23.4 pg Fe/cell. No significant change was found in viability, proliferation, MMP change, ROS production, or differentiation capacity. About 45.2% of the hMSCs could be detected using 1.5 T MRI at the single cell level with 3D GRE and four repetitions. Magn Reson Med 58:717–724, 2007.

Internal morphology of human cervical pedicles.

STUDY DESIGN The internal architecture of cervical spine pedicles was investigated by thin sectioning and digitization of radiographic images. OBJECTIVES To provide quantitative information on the internal dimensions and cortical shell thicknesses of the middle and lower cervical pedicles. SUMMARY OF BACKGROUND DATA Although there have been a number of studies presenting data on the external dimensions of the cervical pedicle, little is known regarding its internal architecture and cortical shell thickness along the pedicle axis. METHODS Twenty-five human cervical vertebrae (C3-C7) were secured to a thin-sectioning machine to produce three 0.7-mm-thick pedicle slices along its axis. Plain radiographs of the pedicle slices were scanned and digitized to facilitate measurement of the internal dimensions. Computer software was specifically developed to determine the external dimensions (i.e., pedicle height and width) and the internal dimensions (i.e., cortical shell thicknesses of the superior, inferior, lateral, and medial walls and the cancellous core height and width) of cervical pedicles. RESULTS Superior and inferior wall cortical thicknesses of pedicle thin slices were similar, whereas the lateral wall cortical thickness was significantly smaller than the medial wall thickness. The medial cortical shell (average value range: 1.2-2.0 mm) was measured to be 1.4 to 3.6 times as thick as the lateral cortical shell (average value range: 0.4-1.1 mm). When medial and lateral cortical thicknesses were normalized for external dimensions, the combined cortical shell thickness was thinnest at C7 (average value range: 18. 6-25.6% of the external width), and this result was statistically significant when compared with other vertebral levels. CONCLUSIONS The cervical pedicle is a complex, three-dimensional structure exhibiting extensive variability in internal morphology. Characteristics of the cervical pedicle at different spinal levels must be noted before transpedicular screw fixation.

The postural stability control and gait pattern of idiopathic scoliosis adolescents

OBJECTIVE: The static postural equilibrium and gait patterns between idiopathic scoliotic (IS) patients and normal subjects were studied to verify the best method to identify the functional disability in IS patients. DESIGN: The static stability in six postures and gait patterns among normal subjects and IS patients were compared. BACKGROUND: Postural stability control and gait analysis are non-invasive methods to identify many diseases. However, the dysfunction of IS patients in postural stability control and gait pattern is not clear. The results of this research may lead to further understanding of the etiology of idiopathic scoliosis in the postural equilibrium influencing aspects. METHODS: Thirty IS patients and fifteen normal subjects were recruited for postural stability control test and gait analysis using the force plate and 3-D motion analysis system. RESULTS: The IS patients generally produced higher sway area, lateral sway, sagittal sway, and sway radius than normal subjects. The cadence is smaller in the IS patients, but the stance phase and stride phase are similar to normal subjects. CONCLUSIONS: The IS patients are poor in postural stability control but their gait pattern is similar to that of normal subjects. Standing with trunk at full flexion is the most effective position to identify the postural stability control of IS patient.

Viscoelastic finite-element analysis of a lumbar motion segment in combined compression and sagittal flexion: Effect of loading rate

Study Design. A study using a validated viscoelastic finite-element model of a L2–L3 motion segment to identify the load sharing among the passive elements at different loading rates. Objective. To enhance understanding concerning the role of the loading rate (i.e., speed of lifting and lowering during manual material handling tasks) on the load sharing and safety margin of spinal structures. Summary of Background Data. Industrial epidemiologic studies have shown that jobs requiring a higher speed of trunk motion contribute to a higher risk of industrial low back disorders. Consideration of the dynamic loading characteristics, such as lifting at different speeds, requires modeling of the viscoelastic behavior of passive tissues. Detailed systematic analysis of loading rate effects has been lacking in the literature. Methods. Complex flexion movement was simulated by applying compression and shear loads at the top of the upper vertebra while its sagittal flexion angle was prescribed without constraining any translations. The lower vertebra was fixed at the bottom. The load reached its maximum values of 2000 N compression and 200 N anterior shear while L2 was flexed to 10° of flexion in the three different durations of 0.3, 1, and 3 seconds to represent fast, medium, and slow movements, respectively. The resisted bending moment, gross load-displacement response of the motion segment, forces in facet joints and ligaments, stresses and strains in anulus fibrosus, and intradiscal pressure were compared across different rates. Results. The distribution of stress and strain was markedly affected by the loading rate. The higher loading rate increased the peak intradiscal pressure (12.4%), bending moment (20.7%), total ligament forces (11.4%), posterior longitudinal ligament stress (15.7%), and anulus fiber stress at the posterolateral innermost region (17.9%), despite the 15.4% reduction in their strain. Conclusions. Consideration of the time-dependent material properties of passive elements is essential to improving understanding of motion segment responsesto dynamic loading conditions. Higher loading rate markedly reduces the safety margin of passive spinal elements. When the dynamic tolerance limits of tissues are available, the results provide bases for the guidelines of safe dynamic activities in clinics or industry.

Antibacterial activity and biocompatibility of a chitosan–γ-poly(glutamic acid) polyelectrolyte complex hydrogel

In this study, we prepared a polyelectrolyte complex (PEC) hydrogel comprising chitosan as the cationic polyelectrolyte and gamma-poly(glutamic acid) (gamma-PGA) as the anionic polyelectrolyte. Fourier transform infrared spectroscopy revealed that ionic complex interactions existed in the chitosan-gamma-PGA PEC hydrogels. The compressive modulus increased upon increasing the degree of complex formation in the chitosan-gamma-PGA PEC hydrogel; the water uptake decreased upon increasing the degree of complex formation. At the same degree of complex formation, the compressive modulus was larger for the chitosan-dominated PEC hydrogels; the water uptake was larger for the gamma-PGA-dominated ones. Scanning electron microscopy images revealed the existence of interconnected porous structures (pore size: 30-100mum) in all of the chitosan-gamma-PGA PEC hydrogels. The chitosan-gamma-PGA PEC hydrogels also exhibited antibacterial activity against Escherichia coli and Staphylococcus aureus. In addition, in vitro cell culturing of 3T3 fibroblasts revealed that all the chitosan-gamma-PGA PEC hydrogels were effective in promoting cell proliferation, especially the positively charged ones (chitosan-dominated). Therefore, the chitosan-gamma-PGA polyelectrolyte hydrogel appears to have potential as a new material for biomedical applications.

Stabilizing potential of anterior cervical plates in multilevel corpectomies.

STUDY DESIGN An in vitro investigation of three-dimensional kinematics of cervical spine models of one- and three-level corpectomy with anterior plate fixation. OBJECTIVES To evaluate the capability of an anterior plate to stabilize the reconstructed cervical spine under simulated physiologic motions, and to study the effects of fatigue loading. SUMMARY OF BACKGROUND DATA Clinical studies have found high failure rates of multilevel anterior cervical plate fusions, indicating suboptimal stabilization. However, no biomechanical studies have been done to investigate the stabilizing capabilities of long-plate instrumentations in corpectomy models. METHODS Seven fresh human cadaveric cervical spine specimens (C2-T1) were used. Flexibility tests consisted of flexion, extension, and bilateral torsion, and lateral bending, each with a pure moment of 0.25, 0.5, 0.75, and 1.0 Nm. Stabilizing potential indices [(MotionIntact-MotionInstrumented)/MotionIntact] for ranges of motion and neutral zones obtained from the flexibility tests, were measured when the specimen was intact and after one-level (C5) and three-level (C4, C5, and C6) corpectomies and anterior plate stabilizations). The stabilizing potential indices were re-measured after a 1000-cycle fatigue loading (1 Nm flexion and extension moments at C5 vertebra at 0.14 Hz). RESULTS The differences in stabilizing potential indices of range of motion and neutral zone between one-level and three-level plates were not significant before fatigue. However, after fatigue, the stabilizing potential indices significantly decreased (P < 0.05) for the three-level model, but not for the one-level plate model. CONCLUSIONS The capability of an anterior cervical plate to stabilize the spine after three-level corpectomy was significantly reduced with fatigue loading.

Macrophage physiological function after superparamagnetic iron oxide labeling.

Our goal was to analyze the changes in morphology and physiological function (phagocytosis, migratory capabilities, humoral and cellular response, and nitric oxide secretion) of murine macrophages after labeling with a clinically used superparamagnetic iron oxide (SPIO), ferucarbotran. In SPIO‐treated macrophages, nanoparticles were taken up in the cytoplasm and accumulated in a membrane‐bound organelle. Macrophage proliferation and viability were not modified after SPIO labeling. Phagocytic function decreased after labeling with only 10 µg Fe/mL SPIO, whereas other functions including migration and production of tumor necrosis factor‐α and nitric oxide increased at the highest SPIO concentration (100 µg Fe/mL). Copyright

Quantification of the pulse wave velocity of the descending aorta using axial velocity profiles from phase-contrast magnetic resonance imaging

The pulse wave velocity (PWV) of aortic blood flow is considered a surrogate for aortic compliance. A new method using phase‐contrast (PC)‐MRI is presented whereby the spatial and temporal profiles of axial velocity along the descending aorta can be analyzed. Seventeen young healthy volunteers (the YH group), six older healthy volunteers (the OH group), and six patients with coronary artery disease (the CAD group) were studied. PC‐MRI covering the whole descending aorta was acquired, with velocity gradients encoding the in‐plane velocity. From the corrected axial flow velocity profiles, PWV was determined from the slope of an intersecting line between the presystolic and early systolic phases. Furthermore, the aortic elastic modulus (Ep) was derived from the ratio of the brachial pulse pressure to the strain of the aortic diameter. The PWV increased from YH to OH to CAD (541 ± 94, 808 ± 184, 1121 ± 218 cm/s, respectively; P = 0.015 between YH and OH; P = 0.023 between OH and CAD). There was a high correlation between PWV and Ep (r = 0.861, P < 0.001). Multivariate analysis showed that age and CAD were independent risk factors for an increase in the PWV. Compared to existing methods, our method requires fewer assumptions and provides a more intuitive and objective way to estimate the PWV. Magn Reson Med, 2006.

Loosening at the screw-vertebra junction in multilevel anterior cervical plate constructs.

STUDY DESIGN An in vitro biomechanical study of one-level and three-level corpectomy and anterior cervical plate models. OBJECTIVE To investigate the failure of the screw-vertebra interfaces in one- and three-level corpectomy models. SUMMARY AND BACKGROUND DATA Although there are several biomechanical studies of strength and stability of anterior cervical plating, there has been no investigation into clinically observed failures. METHODS One- and three-level models (corpectomy, strut graft, and anterior plate) were constructed from eight cadaveric specimens (C2-T1). Multidirectional flexibility tests (1.0 Nm moments) performed before and after fatigue (1000 cycles, 1.0 Nm flexion-extension, 0.14 Hz) documented the screw-vertebra motions at upper and lower ends. Ranges of motion and neutral zones were determined. Analysis of variance was used to evaluate significant differences between the upper and lower ends of the plates and changes caused by fatigue loading (P < 0.05). RESULTS Extension motion at the lower ends was more than at the upper ends in both models. Fatigue increased three-level model ranges of motion at the lower end by 171% in flexion, 164% in extension, 153% in lateral bending, and 115% in axial rotation. Similar increases were observed in neutral zones. Fatigue loading produced no significant changes in one-level models. CONCLUSION There was excessive screw-vertebra motion caused by fatigue at the lower end of the three-level corpectomy model. These findings of loosening may explain clinically observed failures at the caudal end of long anterior cervical plate constructs. Longer screws, larger diameter screws, and supplemental posterior fixation may decrease screw-vertebra loosening.

Normal Systolic and Diastolic Functions of the Left Ventricle and Left Atrium by Cine Magnetic Resonance Imaging

Volume and phase characteristics of the left ventricle (LV) and left atrium (LA) were assessed in 31 healthy Asian adults (19 males and 12 females) using cine magnetic resonance imaging (MRI) and an automated boundary detection algorithm. Volume indexes of the LV and LA were smaller than published results obtained mostly from Westerners. Other than LV mass index and percent emptying of the LA, there was no gender difference in all LV/LA indexes. In associating LV/LA functions with the body size and heart rate (HR), we found that LV mass and the minimum LA volume correlated strongly with the body surface area, the maximum LA volume and the reservoir volume correlated strongly with the body weight, and the time to LV peak-filling rate (LVPFRt) and the time to LA peak-emptying rate (LAPERt) correlated strongly with the HR. In associating LV with LA functions, we found that LA conduit volume contributed more than 50% of the LV stroke volume, and correlated with both systolic and diastolic functions of the LV. Moreover, LVPFRt and LAPERt were virtually identical, indicating a mechanical coupling between LV and LA during diastole. In conclusion, using time-resolved, three-dimensional volume data obtained from cine MRI, we have established normative values of LV and LA functions and their functional relationships in healthy Asian adults. The imaging acquisition protocol, data analysis algorithms, and the established normative values provide the basis for the study of left heart function in patients.