ObjectiveTo compare the fixation strength of optimum placed pedicle screw (OS) with re-directionally correctly placed pedicle screw (RS) following a violation of lateral pedicle. MethodsThirty fresh lumbar vertebrae (L1-5) were obtained from 6 pigs weighing 95-105 kg, male or female. Each vertebra was instrumented with a monoaxial pedicle screw into each pedicle using two different techniques. On one side, a perfect screw path was created using direct visualization and fluoroscopy. A pedicle screw of 5 mm in diameter and 35 mm in length was placed with a digital torque driver (OS). On the other side, a lateral pedicle wall violation was created at the pedicle-vertebral body junction with a guide wire, a cannulated tap, and a pedicle probe. This path was then redirected into a correct position, developed, and instrumented with a 5-mm-diameter by 35-mm-long pedicle screw (RS). For each pedicle screw, the maximal torque, seating torque, screw loosening force, and post-loosening axial pullout were measured. Screw loosening and axial pullout were assessed using an MTS machine. ResultsMaximal insertion torque was (111.4±8.2) N·cm and (78.9±6.4) N·cm for OS and RS respectively, showing significant difference (Z=3.038, P=0.002). The seating torque was (86.3±7.7) N·cm and (59.7±5.3) N·cm for OS and RS respectively, showing significant difference (Z=2.802, P=0.005). The screw loosening force was (76.3±6.2) N and (53.0±5.8) N for OS and RS respectively, showing significant difference (Z=2.861, P=0.004). The post-loosening axial pullout force was (343.0±12.6) N and (287.0±10.5) N for OS and RS respectively, showing significant difference (Z=2.964, P=0.003). ConclusionCompared with OS, RS placement after a lateral wall violation shows significantly decreased maximal insertion torque, seating torque, screw loosening force, and post-loosening axial pullout. On this occasion, RS augmentation is a probable option for remediation.
ObjectiveTo explore the application of extracorporeal venovenous bypass in orthotopic liver transplantation in pigs and to compare hemodynamic changes during operation of two different bypass ways. MethodsTwentyfive porcine orthotopic liver transplantations were performed and extracorporeal venovenous bypass was established during anhepatic phase through a catheter in portal vein (group A,n=16) or in splenic vein (group B,n=9).Hemodynamic changes were monitored continuously.ResultsFourteen recipients survived two days after operation (14/16) in group A while all survived in group B (9/9).Transient hemodynamic disturbance (MAP and CVP decreased,and HR increased) was monitored at both the beginning and the end of anhepatic stage in group A,while these parameters kept stable in group B (P＜0.05).ConclusionApplying venovenous bypass may stabilize recipients’ hemodynamics in porcines orthotopic liver transplantation,and splenic vein draining way has more advantages than portal vein.
ObjectiveTo investigate the aim antigen coursing the hyperacute rejection of xenotransplantation. MethodsDocuments about hyperacute rejection in xenotransplantation were reviewed and summarized in detail. ResultsPig is thought to be one of the ideal donors of xenotransplantation, but the major obstacle is hyperacute rejection mediated by complement that is activated though human serum. αGal is recognized as the major antigen and its expression is controlled by α1,3 galactosyltransferase. Immunoabsorption of preexsisted antibody, enzymatic digestion of αGal, knockout αGT gene and transgenic technology have been used to solve this problem. Even so, there remain other antigens which can combine with natural antibodies in human serum, such as, 40×103 molecule in erythrocyte, 210×103, 105×103 and 50×103 antigen in pig embryo brain cell, etc. Conclusion αGal is the major antigen which course the hyperacute rejection. Besides αGal, many nonalphagal need further investigation.
Objective To investigate the mechanism of hyperacute rejection (HAR) in pig to rhesus monkey vein xenograft. Methods Porcine femoral vein was transplanted into rhesus monkey. Deposits of IgM, IgG, C3 and C4 on the grafts were observed by immunoflurescence. Results Great deal of IgM, C3 and C4 were seen along the endothelium of donor vein, but IgG was not seen. ConclusionIn pig to monkey xenograft model, HAR is intiated by the binding of xenoreactive IgM to donor xenoantigens and followed by the activation of complement via the classical pathway.
Objective To investigate the effect of intra-abdominal hypertension(IAH) on respiratory function in pigs.Methods Twelve pigs were randomly divided into two groups (n=6 in each group),ie.IAH20 group(intra-abdominal pressure=20 mm Hg) and IAH30 group(intra-abdominal pressure=30 mm Hg).Pig model of IAH was established by intraperitoneally injection of carbon dioxide.The changes in respiratory function parameters including pulmonary dynamic compliance（Cdyn），peak inspiratory pressure(PIP) ,SpO2 and PaCO2 were recorded at different time points.Results Cdyn was significantly decreased at different time points compared with baseline in group IAH30 and group IAH20.PIP significantly increased at different time points compared with baseline in both IAH groups，but group IAH30 was more severe than group IAH20. No significant changes of SpO2 and PaCO2 were found in two IAH groups.Conclusion IAH can impair respiratory function by decreasing lung compliance and increasing inspiratory pressure.
Objective To study and test novel hybrid valves in vitro and in vivo, and provide basis for clinical use in future. Methods The hybrid valves were fabricated from decellularized porcine aortic valves coated with poly (3-hydroxybutyrate-co-3hydroxyhexanoate, PHBHHx).（1）In the mechanical test in vitro, the uniaxial tensile biomechanics test of the fresh (n=12), uncoated (n=12) and hybrid valve leaflets (n=12) were investigated. (2）In study in vivo, hybrid valves(n=5) implanted in pulmonary position in sheep without cardiopulmonary bypass. Uncoated grafts (n=5) used as control. The specimens of the hybrid or uncoated valve in sheep were explanted and examined by scanning electron microscopy, histology, calcium content and immunofluorescence staining 18 weeks after surgery. Results The mechanical test in vitro revealed that coating with PHBHHx increased maximal tensile strength of hybrid valves compared with the fresh and uncoated state (P＜0.05). The results in vivo indicated the hybrid valves maintained original shape and softness. Immunofluorescence staining for CD31 confirmed that the surface of hybrid valve was covered by confluent CD31+ cells.The interstitium of hybrid valve indicated that smooth muscle actin (SMA)+ cells population were similar to native valvular tissue. The calcium content of hybrid valve was significantly lower than that of uncoated valve leaflets (P＜0.05). Conclusion Decellularized porcine aortic valves coated with PHBHHx have good biological and biomechanical characteristics. The hybrid valve may provide superior valve replacement with current techniques.
Objective To study the development of a physiologic fixation method and investigate the effect of physiologic fixation method on porcine aortic root and aortic valve leaflets. Methods Physiological fixer of aortic root was manufactured in a factory. The fixers with different diameter were made of organic glass. Porcine aortic root with ascending aorta and anterior leaflet of mitral valve and partial ventricular septum were dissected out from the fresh heart. The roots were attached to appropriately sized inflow and outflow spigots. Physiologic fixation was utilized to maintain aortic root and leaflets natural anatomical shape, the aortic root was pressurized to the inflow and outflow portions simultaneously, and the leaflets floated freely at zero-pressure differential with in the pressurized root. Results The process of physiologic fixation retained the properties of a native valve. The leaflets were much softer and extensible than those from valves fixed under low pressure. The results of pulsatile flow testing indicated that the effective orifice areas of predilation at 80mmHg were significantly greater than those of predilation at 40 mmHg（P〈0.05）, while mean pressure differences were found to be lower comparatively（P〈0.05）. This difference translates into a mode of valve function that more closely approximates that of the native aortic valve. Conclusion Physiologic fixation process retains the valve＇s natural anatomical shape as well as the underlying structure of the leaflets, providing improved flow characteristics.
Objective To construct recombinant lentiviral vectors of porcine bone morphogenetic protein 2 (BMP-2) gene and to detect BMP-2 gene activity and bone marrow mesenchymal stem cells (BMSCs) osteogenetic differentiation so as to lay a foundation of the further study of osteochondral tissue engineering. Methods BMSCs were isolated from bone marrow of 2-month-old Bama miniature porcines (weighing, 15 kg), and the 2nd generation of BMSCs were harvested for experiments. The porcine BMP-2 gene lentiviral vector was constructed by recombinant DNA technology and was used to transfect BMSCs at multiplicity of infection (MOI) of 10, 25, 50, 100, and 200, then the optimal value of MOI was determined by fluorescent microscope and inverted phase contrast microscope. BMSCs transfected by BMP-2 recombinant lentiviral vectors served as experimental group (BMP-2 vector group); BMSCs transfected by empty vector (empty vector group), and non-transfected BMSCs (non-transfection group) were used as control groups. RT-PCR, immunohistochemistry staining, and Western blot were performed to detect the expressions of BMP-2 mRNA and protein. Then the BMSCs osteogenesis was detected by alkaline phosphatase (ALP) staining, ALP activities, and Alizarin red staining. Results The recombinant lentiviral vectors of porcine BMP-2 gene was successfully constructed and identified by RT-PCR and gene sequencing, and BMSCs were successfully transfected by BMP-2 recombinant lentiviral vectors. Green fluorescent protein could be seen in the transfected BMSCs, especially at MOI of 100 with best expression. The immunohistochemistry staining and Western blot showed that BMSCs transfected by BMP-2 recombinant lentiviral vectors could express BMP-2 protein continuously and stably at a high level. After cultivation of 2 weeks, the expression of ALP and the form of calcium nodules were observed. Conclusion The porcine BMP- 2 gene lentiviral vector is successfully constructed and transfected into the BMSCs, which can express BMP-2 gene and protein continuously and stably at a high level and induce BMSCs differentiation into osteoblasts.