Papers by Author: Yun Yu Hu

Abstract: Large osseous defects are difficult to treat because of deficient blood supply on the defected area. To get sufficient blood supply, we designed to establish the adenovirus simultaneously encoding both VEGF and Ang-1 (pAd-VIA) to accelerate the formation of new vessels in the process of bone defect repair. The construction of the adenovirus was performed according to the method reported by Tong-Chuan HE with a tiny modification. Three kinds of adenoviruses were acquired. They are adenovirus pAd-VIA simultaneously encoding VEGF and Ang-1, adenovirus pAd-VEGF encoding VEGF, and adenovirus pAd-Ang-1 encoding Ang-1. The adenovirus prepared in this study could successfully transfer VEGF and Ang-1 into mesenchymal stem cells(MSCs) with high efficiency. Two-gene modified artificial bone was established by use of these adenovirus. In the end, the two-gene modified artificial bone was proved to have good biocompatibility and biological function. Study reports presented here will pave the way for further exploration of vascularization in the process of large osseous defects repair.

Abstract: Grafting of autologous iliac crest and decortication approach in posterior spinal fusion surgery has been the “gold standard”. However, the limited source of autograft has prompted extensive research into bone substitute and biological enhancement of the fusion mass. In this study, the application of stem cell therapy by tissue engineering method was investigated to enhance posterior spinal fusion with
-tricalcium phosphate ceramics in rabbit model. Rabbit bone marrow derived mesenchymal stem cells were aspirated from trochanter region of proximal femur. The mesenchymal stem cells were grown and directed to differentiate into osteogenic cells by osteogenic supplement (ascorbic acid,
-glycerophosphate and dexamethasone) in basal medium (10% FBS in DMEM). The osteogenic cells were seeded on tricalcium phosphate ceramics for one day (MSC group, n=6). The cell-ceramics composite was implanted onto autologous L5 and L6 transverse processes with decortication approach in posterior spinal fusion. The cell free ceramics acts as control (Control group, n=6) and iliac crest autograft as positive control (Autograft group). The spinal segments were harvested at week 7 post-operation. Manual palpation was performed with spinal segments to assess any movement of L5-L6 vertebral joint. The stiffness of the joint was considered as solid fusion. The specimens then were fixed by formalin and transferred to 70% ethanol. The BMC and volume of fusion transverse processes of L5 and L6 was measured by peripheral quantitative computed tomography. In manual palpation, 50% solid fusion was found in MSC group, 60% in autograft group but none in control group. Moreover, the BMC of L5 and L6 transverse processes in MSC group was greater than autograft and control group (45%, 40% respectively, p<0.01). The volume of transverse processes in MSC group was greater than autograft by 45% (p<0.01) and control group by 26% (p<0.05). In conclusion, the mesenchymal stem cells derived osteogenic cells augmented spinal fusion and bone mineralization.

Abstract: The limited source of autograft has prompted extensive research on bone substitute and biological enhancement of the fusion mass in spinal fusion. Biomaterials impregnated with bone marrow aspirate has been applied to spinal fusion surgery. In this study, the effect of stem cell therapy in enhancing posterior spinal fusion was compared with the bone marrow aspirate method in a standard rabbit model. Bone marrow was aspirated from rabbit proximal femur (BMA group, n=6) and loaded on β-tricalcium phosphate ceramics (β-TCP) in excess. The composite was then implanted onto L5 and L6 transverse processes of the same animal in posterior spinal fusion operation with decortication on the same day. For stem cell therapy group, mesenchymal stem cells (MSCs) were isolated from bone marrow aspirate by adherence on plastic culture-ware. The MSCs were treated with osteogenic supplements (OS) during ex vivo cell expansion (MSC group, n=6). The osteogenic cells were seeded on β-TCP ceramics and cultured for one day. The cell-ceramics composite was implanted into the same rabbit as BMA group. The ceramics acted as control (n=6). Three fluorochromes, tetracycline, xyelonol orange and caclein were injected at week 2, 4 and 6 sequentially. The spinal segments were harvested at week 7 post-operation. The manual palpation of vertebral joint was assesses for solid fusion. The gap distance of inter-transverse process was measured by microCT and the bone mineral content (BMC) and volume of transverse processes by peripheral quantitative computed tomography. The specimens were undergone undecalcified histological analysis. The mineralization process was examined by fluorescent microscopy. By manual palpation, 50% of MSC group samples were found to have solid fusion in comparison with the incomplete fusion observed in the BMA and control group. The gap distance of inter-transverse processes in MSC group was the shortest. The volume of the transverse processes in MSC group was significantly greater than BMA and control group by 16% and 26% respectively. The BMC of transverse processes in MSC group was 40% greater than control (p<0.05) and 8% greater than BMA group. In fluorescent microscopy, both green fluorescent signal (labeled at week 6) and orange fluorescent signal (labeled at week 4) were observed in MSC group compare with the predominantly green fluorescent signal in the BMA group. In conclusion, the augmentation of MSC derived osteogenic cells is superior to bone marrow aspirate in rabbit posterior spinal fusion.

Abstract: Basic fibroblast growth factor (bFGF) has been shown to maintain the osteogenicity of bone marrow derived mesenchymal stem cell (MSCs) in vitro. This study was to investigate whether bFGF with osteogenic supplements could enhance bone formation of posterior spinal fusion. Rabbit bone marrow derived mesenchymal stem cells were selected by adherence on plastic culture-ware. The MSCs were exposed to dexamethasone with (bFGF group, n=6) or without bFGF (OS group, n=6). Treated cells of two groups were seeded on β-tricalcium phosphate ceramics for one day and then implanted onto L5 and L6 transverse processes of the same animal in posterior spinal fusion without decortication. The ceramics acted as control (n=6). Three fluorochromes were injected sequentially as tetracycline at week 2, xylenol orange at week 4 and calcein at week 6. The spinal segments were harvested at week 7. The bone mineral content (BMC) and volume of transverse processes was measured by peripheral quantitative computed tomography. The specimens were underwent undecalcified histology. The mineralization process was examined by fluorescent microscopy. The BMC of transverse processes in OS group was 16% greater than bFGF and control group significantly. The volume of transverse process in OS and bFGF group was significantly greater than control group by 54% and 46% respectively. The volume of transverse processes in OS group was 6% greater than bFGF group though not statistically significant. In histology, newly formed bone grew from two processes towards each other resulting in a relatively short gap distance in OS and bFGF group while less regenerated bone was observed in the control group. At the mineralization front, calcein which was injected into animal at week 6, was predominately labeled in bFGF group. In OS group, both xylenol orange (at week 4) and calcein labeled were found. In conclusion, mesenchymal stem cells pre-exposed to bFGF were not found to give additional enhancement effect on bone formation in the posterior spinal fusion model.

Abstract: It is important to improve the reliability of the eddy current non-destructive testing. It is generally difficult to reduce the probability of non-detection and the number of false alarms same time. Model Based Measurement (MBM), including estimation of state, failure diagnosis and trend analysis, has excellent results on general estimation. Actual results of MBM vary with the application domain, mathematical model and data processing. The time series model is a description of system in time domain based on equivalent output. The Kalman filter is an efficient method for suppressing the disturbance and improving the state estimation. A new method, called as eddy current testing (ECT) using a model based measurement, is presented. Two time series models are used for the normal status and the abnormal status in ECT. The Kalman filter on these models is applied to give useful information for decision making. Results of the experiment on aluminum plates demonstrate that this method is useful to improve the detection reliability.

Abstract: Research achievements in a high speed attraction type magnetic levitation vehicle experimental system are reported. The high speed attraction type magnetic levitation vehicle constitutes a typical long stator linear synchronous motor. The study on levitation and propulsive electromagnetic fields is of great importance and is studied. Owing to the influence of the stator grooves and the material discontinuousness, the magnetic field distribution is very complex to be analyzed in analytical forms. The magnetic fields in the air gap are determined using the finite element method. The levitation force and thrust produced by the levitation magnetic field and the propulsive magnetic field are calculated. They are found to vary following the change of the air gap and exciting current. A magnetic field strength measurement system based on a hall sensor is designed. Experimental results are compared with the results from the magnetic field analysis.

Abstract: Bone marrow mesenchymal stem cells (BMSCs) possess a high replicative capacity and have the capacity to differentiate into various connective tissue cell types. With the advance in cell culture technique, the BMSCs have been induced to differentiate to osteoblastics linage. To improve the situation of non-union in posterior spinal fusion (PSF), tissue engineering approach to combine BMSCs supported by the calcium phosphate ceramics was applied in PSF and its effect was investigated in the present study. Autologous BMSCs from 16-week-old rabbit tibiae were expanded and induced to differentiate into osteoblastic cells with defined medium and osteogenic supplement. Calcium phosphate ceramic (CPC) was used as the scaffold to deliver the cells to the standardized rabbit posterior spinal fusion model. The assessment of bone mineral and fusion mass volume was conducted at week 7 post-operation with quantitative computed tomography and micro-computed tomography. When compared with control, the composite of BMSCs with CPC enhanced the fusion mass volume by 40% (p<0.05) and bone mineral content in the CPC was 7% (p=0.05) higher. Our study showed that additional BMSCs at the fusion site of PSF did provide extra resource for new bone formation and enhanced the fusion rate.