A number of congenital and acquired disorders require esophageal tissue replacement.Various surgical techniques,such as gastric and colonic interposition,are standards of treatment,but frequently complicated by stenos...A number of congenital and acquired disorders require esophageal tissue replacement.Various surgical techniques,such as gastric and colonic interposition,are standards of treatment,but frequently complicated by stenosis and other problems.Regenerative medicine approaches facilitate the use of biological constructs to replace or regenerate normal tissue function.We review the literature of esophageal tissue engineering,discuss its implications,compare the methodologies that have been employed and suggest possible directions for the future.Medline,Embase,the Cochrane Library,National Research Register and ClinicalTrials.gov databases were searched with the following search terms:stem cell and esophagus,esophageal replacement,esophageal tissue engineering,esophageal substitution.Reference lists of papers identified were also examined and experts in this field contacted for further information.All full-text articles in English of all potentially relevant abstracts were reviewed.Tissue engineering has involved acellular scaffolds that were either transplanted with the aim of being repopulated by host cells or seeded prior to transplantation.When acellular scaffolds were used to replace patch and short tubular defects they allowed epithelial and partial muscular migration whereas when employed for long tubular defects the results were poor leading to an increased rate of stenosis and mortality.Stenting has been shown as an effective means to reduce stenotic changes and promote cell migration,whilst omental wrapping to induce vascularization of the construct has an uncertain benefit.Decellularized matrices have been recently suggested as the optimal choice for scaffolds,but smart polymers that will incorporate signalling to promote cell-scaffold interaction may provide a more reproducible and available solution.Results in animal models that have used seeded scaffolds strongly suggest that seeding of both muscle and epithelial cells on scaffolds prior to implantation is a prerequisite for complete esophageal replacement.Novel approaches need to be designed to allow for peristalsis and vascularization in the engineered esophagus.Although esophageal tissue engineering potentially offers a real alternative to conventional treatments for severe esophageal disease,important barriers remain that need to be addressed.展开更多
A numerical study of flow around two tandem cylinders with unequal diameters was carried out. The upstream larger cylinder was fixed and the downstream smaller cylinder was allowed to oscillate in the transverse direc...A numerical study of flow around two tandem cylinders with unequal diameters was carried out. The upstream larger cylinder was fixed and the downstream smaller cylinder was allowed to oscillate in the transverse direction only. Comparisons of the experimental and numerical results were made to investigate the effects of the gap ratio on the maximum vibration amplitude and vortex shedding frequency. The results showed that the vibration response of the smaller cylinder was significantly affected by the presence of the upstream larger cylinder, and resulted in greatly reduced vibration amplitudes. With an increasing gap ratio, the vibration amplitude increased. However, the magnitude was lower than that corresponding to a single cylinder (with the same diameter as that of the downstream smaller cylinder) under the same flow conditions.展开更多
Objective To detemine optimal conditions by using 5 bromodeoxyuridine (BrdU) as a marker of transplanted retinal pigment epithelial (RPE) cells in the subretinal space of albino rabbits ...Objective To detemine optimal conditions by using 5 bromodeoxyuridine (BrdU) as a marker of transplanted retinal pigment epithelial (RPE) cells in the subretinal space of albino rabbits Methods Pigmented rabbit RPE cells at second to fifth passage were fed with 20 μmol/L BrdU in Eagle’s minimal essential medium (MEM) for five days After extensive wash with phosphate buffered saline (PBS),the cells were detached by trypsin and used for transplantation onto Bruch’s membrane of albino rabbits Eyes were enucleated at various times post transplantation Acetone, 4% paraformaldehyde, periodate lysine paraformaldehyde (PLP),or half strength Karnovsky’s fixatives were individually used to fix the tissue in order to find optimal condition for detecting BrdU marker The fixation was followed by embedding in OCT compound, glycol plastic, or paraffin The transplanted area was then sectioned, pepsin digested, and used for immunohistochemical staining with monoclonal antibody against BrdU and avidin biotin alkaline phosphatase complex (ABC AP) Results Frozen sections of acetone or paraformaldehyde fixed tissue gave strong immunostaining of BrdU but the overall morphology was poor Karnovsky’s fixed tissue offered strong staining but this was buried by strong background When using PLP as a fixative, we obtained strongly positive blue staining with very low background, and also excellent morphologic preservation Conclusion In combination with immunohistochemical detection method, BrdU labeling is an excellent long term marker for RPE transplantation one year after surgery To use BrdU as a marker necessitates the use of pepsin digestion to make the BrdU antigen in the nuclei accessible to antibody But the pepsin digestion may damage other tissues and result in overall poor morphology Among the fixatives tested in this study, PLP fixed tissues offered both strong BrdU staining and good preservation of structural integrity, particularly the fine structure of photoreceptor and RPE cells展开更多
文摘A number of congenital and acquired disorders require esophageal tissue replacement.Various surgical techniques,such as gastric and colonic interposition,are standards of treatment,but frequently complicated by stenosis and other problems.Regenerative medicine approaches facilitate the use of biological constructs to replace or regenerate normal tissue function.We review the literature of esophageal tissue engineering,discuss its implications,compare the methodologies that have been employed and suggest possible directions for the future.Medline,Embase,the Cochrane Library,National Research Register and ClinicalTrials.gov databases were searched with the following search terms:stem cell and esophagus,esophageal replacement,esophageal tissue engineering,esophageal substitution.Reference lists of papers identified were also examined and experts in this field contacted for further information.All full-text articles in English of all potentially relevant abstracts were reviewed.Tissue engineering has involved acellular scaffolds that were either transplanted with the aim of being repopulated by host cells or seeded prior to transplantation.When acellular scaffolds were used to replace patch and short tubular defects they allowed epithelial and partial muscular migration whereas when employed for long tubular defects the results were poor leading to an increased rate of stenosis and mortality.Stenting has been shown as an effective means to reduce stenotic changes and promote cell migration,whilst omental wrapping to induce vascularization of the construct has an uncertain benefit.Decellularized matrices have been recently suggested as the optimal choice for scaffolds,but smart polymers that will incorporate signalling to promote cell-scaffold interaction may provide a more reproducible and available solution.Results in animal models that have used seeded scaffolds strongly suggest that seeding of both muscle and epithelial cells on scaffolds prior to implantation is a prerequisite for complete esophageal replacement.Novel approaches need to be designed to allow for peristalsis and vascularization in the engineered esophagus.Although esophageal tissue engineering potentially offers a real alternative to conventional treatments for severe esophageal disease,important barriers remain that need to be addressed.
基金financially supported by DHI-NTU Center, Maritime Research Center and Nanyang Environment and Water Research Institute, Nanyang Technological University (Singapore)
文摘A numerical study of flow around two tandem cylinders with unequal diameters was carried out. The upstream larger cylinder was fixed and the downstream smaller cylinder was allowed to oscillate in the transverse direction only. Comparisons of the experimental and numerical results were made to investigate the effects of the gap ratio on the maximum vibration amplitude and vortex shedding frequency. The results showed that the vibration response of the smaller cylinder was significantly affected by the presence of the upstream larger cylinder, and resulted in greatly reduced vibration amplitudes. With an increasing gap ratio, the vibration amplitude increased. However, the magnitude was lower than that corresponding to a single cylinder (with the same diameter as that of the downstream smaller cylinder) under the same flow conditions.
文摘Objective To detemine optimal conditions by using 5 bromodeoxyuridine (BrdU) as a marker of transplanted retinal pigment epithelial (RPE) cells in the subretinal space of albino rabbits Methods Pigmented rabbit RPE cells at second to fifth passage were fed with 20 μmol/L BrdU in Eagle’s minimal essential medium (MEM) for five days After extensive wash with phosphate buffered saline (PBS),the cells were detached by trypsin and used for transplantation onto Bruch’s membrane of albino rabbits Eyes were enucleated at various times post transplantation Acetone, 4% paraformaldehyde, periodate lysine paraformaldehyde (PLP),or half strength Karnovsky’s fixatives were individually used to fix the tissue in order to find optimal condition for detecting BrdU marker The fixation was followed by embedding in OCT compound, glycol plastic, or paraffin The transplanted area was then sectioned, pepsin digested, and used for immunohistochemical staining with monoclonal antibody against BrdU and avidin biotin alkaline phosphatase complex (ABC AP) Results Frozen sections of acetone or paraformaldehyde fixed tissue gave strong immunostaining of BrdU but the overall morphology was poor Karnovsky’s fixed tissue offered strong staining but this was buried by strong background When using PLP as a fixative, we obtained strongly positive blue staining with very low background, and also excellent morphologic preservation Conclusion In combination with immunohistochemical detection method, BrdU labeling is an excellent long term marker for RPE transplantation one year after surgery To use BrdU as a marker necessitates the use of pepsin digestion to make the BrdU antigen in the nuclei accessible to antibody But the pepsin digestion may damage other tissues and result in overall poor morphology Among the fixatives tested in this study, PLP fixed tissues offered both strong BrdU staining and good preservation of structural integrity, particularly the fine structure of photoreceptor and RPE cells
