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At least 1,747 records · Page 97Linked to original sources
PubMed2005

[Transforming growth factor-beta1-loaded fibrin sealant promote bone marrow Mesenchymal stem cells to contract injectable tissue engineering cartilage in vivo].

OBJECTIVE: To investigate the feasibility that transforming growth factor-beta1 (TGF-beta1) -loaded fibrin sealant (FS) promotes bone marrow mesenchymal stem cells (BMSCs) to create tissue engineering cartilage in vivo. METHODS: The BMSCs were isolated from healthy human and amplified in vitro, and then induced by defined medium containing TGF-beta1 and dexamethasone. After 7 days the induced BMSCs were collected and mixed with TGF-beta1-loaded FS or FS as BMSCs+ FS-TGF-beta1 group and BMSCs+ FS experimental group. Then the mixture was injected by a needle into the dorsum of nude mice. In control group, only FS or BMSCs were injected. The tissue engineering specimens were harvested from nude mice 12 weeks later. Gross observation, average wet weight measurement, glycosaminoglycan (GAG) quantification, histology and immunohistochemistry were used to evaluate the results. RESULTS: The BMSCs have possessed the shape and functional characters of chondrocyte when transferred to a defined medium. After injection of the mixture, the cartilage-like tissue were formed in two experimental groups. Compared with BMSC+ FS group, the specimens of BMSCs +FS-TGF-beta1 group were larger and firmer. Alcian staining showed better metachromatic matrix formation. The GAG contents were significantly higher. Immunohistochemical staining of collagen type II was stronger. However, no cartilage-like tissue was formed in two control groups. CONCLUSION: TGF-beta1-loaded FS can promote BMSCs to contract injectable tissue engineering cartilage in vivo.

Animals↗
PubMed2006

[The extracellular matrix in bone tissue engineering].

OBJECTIVE: To review the research progress of osteoblast extracellular matrix (ECM) and its application in bone tissue engineering. METHODS: The recent related literatures were extensively reviewed. RESULTS: The ECM was complex in its components. The configuration of cell and cell's adhesion, migration, proliferation, and differentiation were subject to the ECM. The bioactivity of the tissue engineering products was revealed by ECM, which predicted the product's efficiency in clinic application. CONCLUSION: ECM has the potential to become the effective index in evaluating tissue engineered products.

Extracellular Matrix↗
PubMed2006

[The study of tissue-engineering bone for repair of segmental bone defects].

OBJECTIVE: To investigate the effect of tissue-engineering bone on repair of segmental bone defects. METHODS: Segmental bone defect of 21mm was created at sheep left metatarsus, which was then implanted with tissue-engineering bone (the experimental group) and pure porous beta-TCP (the control group) respectively. The bone defect in the blank group was left without treatment. After the sheep were sacrificed at the 1st, 3rd, or 6th month postoperatively, the samples were taken and examined by radiological, histological and biomechanical methods as well as scanning electron microscopy. The sheep in the blank group were sacrificed at the 6th month postoperatively. RESULTS: The osteoid tissue, woven bone and lamellar bone in the defect of the experimental group occurred earlier than in the control group. The new bone formed directly without through a cartilaginous intermediate in the experimental group, while the defect was repaired in a "creep substitution" way in the control group. At the 6th month, radiological and biomechanical tests revealed nearly complete repair of the bone defect of the experimental group, partial repair in the control group and non-healing in the blank group. CONCLUSIONS: Tissue-engineering bone can repair bone defect, accelerating healing and without "creep substitution", which is a good option in repair of critical segmental bone defects. This study set up a basis for clinical applications in the future.

Animals↗
PubMed2006

[Reconstruction of urothelium tissue using issue-engineering technique].

OBJECTIVE: To evaluate the feasibility of reconstruction of urothelium tissue in vivo using tissue-engineering technique. METHODS: The urothelium cells were obtained from young rabbit, bladder by mechanical and enzyme digested methods. After expanded in vitro, the 4th to 5th generation urothelium cells were seeded onto the surface of 8 Polylatical/glycolic acid copolymer polymer, the polymer matrix without seeding cells served as control group. A total of 8 cell-polymer scaffolds and 4 simply scaffolds were separately implanted into subcutaneous pockets of athymic mice. The experiment groups included cell-polymer scaffolds 4 weeks and cell-polymer scaffolds 8 weeks. The control group included simply scaffold 4 weeks and simply scaffold 8 weeks. After 4 and 8 weeks, the specimens were obtained and examined by gross inspection, histologically and immunohistochemically. RESULTS: The results of HE and Masson staining showed that the polymer were covered by urothelium cells layers and cells layers increased markley in experimental group. Immunocytochemical studies revealed that the cells were stained positively for anti-cytokeratins (AE1/AE3) in experimental group. Fiber tissue deposition were found on the surface of polymers in control group by HE and Masson staining. Immunocytochemical staining of implants showed the negative result for cytokeratins in control group. CONCLUSION: It is feasibility that reconstruction of urothelium tissue using tissue-engineering technique,which provides basic understandings for further development of the bladder and ureteral tissue engineered research.

Animals↗
PubMed2006

[Tooth movement in tissue-engineered bone].

OBJECTIVE: To explore the effect and practical value of repairing the alveolar defects with tissue engineering technique and investigate the influence of the generated new bone on the orthodontic tooth movement. METHODS: The marrow stromal cells of rats were separated, cultured in vitro and induced to osteoblast-like cells. The osteoblast-like cells were implanted onto the ceramic bovine bone. Then the complex was implanted into the alveolar defect in one side of the rat's mandible. The other side of the mandible served as control. Eight weeks later, the orthodontic appliances were placed between the first molar and incisors of SD rats to move the first molar forward. The tooth movement and root resorption of the molar were observed. RESULTS: We found that the tooth movement in the experimental area was faster than that in the normal alveolar bone (P < 0.05). The root resorption and the alveolar bone height loss were less than that in the control area (P < 0.05). CONCLUSIONS: The tissue-engineered bone did not have negative influences on tooth movement. The repair of alveolar bone defect by tissue engineering approach may be used in craniofacial surgery and orthodontics.

Animals↗
PubMed2006

[Culture condition optimization of engineered E. coli BL21/pET-11c/hIL-2-mGM-CSF].

OBJECTIVE: To optimize the culture condition of engineered E.coli to improve its expression efficiency of hIL-2-mGM-CSF protein. METHODS: According to an orthogonal Latin square experiment design, the effects of the culture medium, temperature and IPTG concentration at different levels on the efficiency of the engineered E. coli were evaluated for its expression of hIL-2-mGM-CSF protein. The results of SDS-PAGE were analyzed with software and the culture conditions derived from the experimental results were tested in independent cultures. The optimal culture condition was used in three large-scale cultures and the results were compared with that of routine cultures. RESULTS: The cultures with TH broth yielded higher relative expression quantity of the target protein than those with 2 x YT and LB medium. Compared with the induction temperature at 37 degrees C, induction at 42 degrees C significantly improved the expression efficiency of the target protein. IPTG at the concentration as low as 0.3 mmol/L produced better effect than 1.0 mmol/L IPTG. Statistical analysis suggested that the optimized culture conditions could obviously improve the expression efficiency of the target protein. Large scale cultures with the optimized culture condition resulted in a 5-fold improvement of the relative expression quantity of the protein, which accounted for over 29% of total bacterial protein. CONCLUSION: The optimized culture condition of the engineered E. coli can remarkably increase the expression efficiency of hIL-2-mGM-CSF, which may facilitate the subsequent purification and functional study of the protein.

Culture Media↗
PubMed2006

[Long-term observation of large weight-bearing bone defect in goats repaired with tissue engineering technique].

OBJECTIVE: To observe the long-term effect of tissue engineering-based repair of large weight-bearing bone defect in goats, and the final outcome of the scaffold material coral hydroxyapatite (CHAP) in vivo. METHODS: Fifteen Chinese goats were subjected to operations to induce a 2-cm left tibial diaphyseal defect, which was filled subsequently with CHAP and bone marrow stromal stem cells (BMSCs). The repaired defects were evaluated by ECT, X-ray and histology in the early stage and at 6, 12, 18, and 24 months postoperatively. RESULTS: ECT showed good bone regeneration and revascularization within 2 months postoperatively. X-ray and histology displayed eccentric and gradual bone regeneration in the early stage, and the tissue-engineered bone graft was firmly healed with the goat tibia. X-ray and histological examination at 6, 12, 18, 24 months postoperatively revealed moulding of the new bones and medullary cavity recanalization, and the structure of CHAP disappeared and gradually integrated into the new bones. CONCLUSION: Tissue-engineered bone is capable of total repair of large bone defect in goats by forming normal functional new bones. CHAP can be eventually degraded completely and become the component of the newly generated bones.

Animals↗
PubMed2006

[Fast harvest of seed cells for composite tissue engineered skin at one time].

OBJECTIVE: To find a feasible method that can fast isolate seed cells, keratinocyte stem cell and fibroblasts, for composite tissue engineered skin. METHODS: The foreskin could be attained from posthectomy, the subcutaneous tissue was removed completely, and the full-thick skin was cut into pieces, 2 mm x 2 mm in size, then the pieces were submerged into a centrifuge tube containing collagenase I in a oscillator. After 3-hour digestion at 37 degrees C, the dermis was dissolved completely with all the fibroblasts in the digestion solution and the epidermis could be separated easily. With more than 10-minute digestion in trypsin at 37 degrees C, the epidermal cells could be harvested. Then flowcytometry and FITC-immunofluorescence for cytokeratin 19 of epidermal cells and FITC-immunofluorescence of vimentin of fibroblast were conducted to identify keratinocyte stem cells in the epidermal cells and fibroblasts in the digestion solution. Moreover, epidermal cells and fibroblasts were cultured in vitro for 7 days to investigate their biological behavior. RESULTS: Using collagenase I combined with trypsin, epidermal cells and fibroblasts could be isolated at one time within 3 hours. Up to 17% cells demonstrated cytokeratin 19 positive in the epidermal cells, with fibroblast vimentin positive. The amount of fibroblast could be enlarged to more than 100 times within 6 days, but the putative keratinocyte stem cells were difficult for subculture. CONCLUSION: Seed cells for composite tissue engineered skin could be harvested fast at one time, that made it possible to reconstruct composite tissue-engineered skin in vitro.

Adolescent↗
PubMed2006

Survival and function of transplanted islet cells on an in vivo, vascularized tissue engineering platform in the rat: A pilot study.

As in vivo tissue engineering of complex tissues and organs progresses, there is a need for an independently vascularized, alterable, and recoverable model. Current models of islet cell transplantation (release into the portal venous system, placement under the renal capsule, and microencapsulation) lack these qualities. We have developed a model of angiogenesis and spontaneous tissue generation in the rat that lends itself as a potential platform for tissue engineering. In this experiment, we examined the effectiveness of such a model in addressing some of the shortcomings of endocrine pancreatic transplantation. An arteriovenous loop was created in the groins of five adult inbred Sprague-Dawley rats, and placed within polycarbonate chambers. Isolated pancreatic islet cell clusters were placed within the chambers, suspended in a matrix of Matrigel. The chambers were recovered at 3 weeks, and the newly generated tissue was processed for histologic and immunohistochemical analysis. By 3 weeks, spontaneous generation of angiogenesis and collagen matrix and deposition of a collagen matrix was observed. Surviving islet cells were identified by histology and their viability was confirmed via immunohistochemistry for insulin and glucagon. This study demonstrates the ability to maintain viability and functionality of transplanted islet cells on a tissue-engineered platform with an independent vascular supply. The model provides the ability to alter the graft environment via matrix substitution, cellular coculture, and administration of growth factors. The transplanted tissues are recoverable without animal sacrifice and are microsurgically transferable. This model may provide an in vivo culture platform for the study of islet transplantation.

Animals↗
PubMedDate not supplied

The effect of hydrodynamic shear on 3D engineered chondrocyte systems subject to direct perfusion.

Bioreactors allowing direct-perfusion of culture medium through tissue-engineered constructs may overcome diffusion limitations associated with static culturing, and may provide flow-mediated mechanical stimuli. The hydrodynamic stress imposed on cells within scaffolds is directly dependent on scaffold microstructure and on bioreactor configuration. Aim of this study is to investigate optimal shear stress ranges and to quantitatively predict the levels of hydrodynamic shear imposed to cells during the experiments. Bovine articular chondrocytes were seeded on polyestherurethane foams and cultured for 2 weeks in a direct perfusion bioreactor designed to impose 4 different values of shear level at a single flow rate (0.5 ml/min). Computational fluid dynamics (CFD) simulations were carried out on reconstructions of the scaffold obtained from micro-computed tomography images. Biochemistry analyses for DNA and sGAG were performed, along with electron microscopy. The hydrodynamic shear induced on cells within constructs, as estimated by CFD simulations, ranged from 4.6 to 56 mPa. This 12-fold increase in the level of applied shear stress determined a 1.7-fold increase in the mean content in DNA and a 2.9-fold increase in the mean content in sGAG. In contrast, the mean sGAG/DNA ratio showed a tendency to decrease for increasing shear levels. Our results suggest that the optimal condition to favour sGAG synthesis in engineered constructs, at least at the beginning of culture, is direct perfusion at the lowest level of hydrodynamic shear. In conclusion, the presented results represent a first attempt to quantitatively correlate the imposed hydrodynamic shear level and the invoked biosynthetic response in 3D engineered chondrocyte systems.

Animals↗
PubMedDate not supplied

Poroelastic numerical modelling of natural and engineered cartilage based on in vitro tests.

The mechanisms underlying the ability of articular cartilage to withstand and distribute the loads applied across diarthrodial joints have been widely studied. Experimental tests have been done under several configurations to reveal the tissue response to mechanical stimuli, and theoretical models have been developed for the interpretation of the experimental results. The experiments demonstrated that the tissue is non-linear with strain, both in tension and in compression, non-linear with direction of stimulus, anisotropic in tension and compression, non-homogeneous with depth, resulting in depth dependent mechanical properties, and presents fluid dependent and fluid independent viscoelasticity. None of the models up to now developed is able to describe the whole set of responses of such a complex tissue. The purpose of this study was to develop a combined experimental-numerical approach for the proper description of the cartilage response under confined and unconfined compression. We defined a series of experimental tests to be performed on disks of natural and engineered cartilage and we developed a numerical model for cartilage, based on the biphasic theory, which potentially includes the tension-compression non-linearity, the strain non-linearity and the fluid independent viscoelasticity. The model successfully simulated the confined and unconfined compression experiments performed on disks of natural and engineered cartilage, and was also used to identify parameters of difficult experimental evaluation, such as the collagen stiffness and the permeability. In conclusion, the use of our model in combination with biomechanical experimental testing seems a valuable tool to analyze the mechanical properties of natural cartilage and the biofunctionality of tissue engineered cartilage.

Aged↗
PubMed2006

Repairing articular cartilage defects with tissue-engineering cartilage in rabbits.

OBJECTIVE: To investigate the effect of cancellous bone matrix gelatin (BMG) engineered with allogeneic chondrocytes in repairing articular cartilage defects in rabbits. METHODS: Chondrocytes were seeded onto three-dimensional cancellous BMG and cultured in vitro for 12 days to prepare BMG-chondrocyte complexes. Under anesthesia with 2.5% pentobarbital sodium (1 ml/kg body weight), articular cartilage defects were made on the right knee joints of 38 healthy New Zealand white rabbits (regardless of sex, aged 4-5 months and weighing 2.5-3 kg) and the defects were then treated with 2.5% trypsin. Then BMG-chondrocyte complex (Group A, n=18), BMG (Group B, n=10), and nothing (Group C, n=10) were implanted into the cartilage defects, respectively. The repairing effects were assessed by macroscopic, histologic, transmission electron microscopic (TEM) observation, immunohistochemical examination and in situ hybridization detection, respectively, at 2, 4, 8, 12 and 24 weeks after operation. RESULTS: Cancellous BMG was degraded within 8 weeks after operation. In Group A, lymphocyte infiltration was observed around the graft. At 24 weeks after operation, the cartilage defects were repaired by cartilage tissues and the articular cartilage and subchondral bone were soundly healed. Proteoglycan and type II collagen were detected in the matrix of the repaired tissues by Safranin-O staining and immunohistochemical staining, respectively. In situ hybridization proved gene expression of type II collagen in the cytoplasm of chondrocytes in the repaired tissues. TEM observation showed that chondrocytes and cartilage matrix in repaired tissues were almost same as those in the normal articular cartilage. In Group B, the defects were repaired by cartilage-fibrous tissues. In Group C, the defects were repaired only by fibrous tissues. CONCLUSIONS: Cancellous BMG can be regarded as the natural cell scaffolds for cartilage tissue engineering. Articular cartilage defects can be repaired by cancellous BMG engineered with allogeneic chondrocytes. The nature of repaired tissues is closest to the normal cartilage. Local administration of trypsin can promote the adherence of repaired tissues to host tissues. Transplantation of allogeneic chondrocytes has immunogenicity, but the immune reaction is weak.

Animals↗
PubMed2006

[Progress of silk fibroin in the cell scaffold of tissue engineering].

Recent researches about the application of silk fibroin in cell culture suggested that silk fibroin displayed high rate of cell attachment and growth in vitro culture of most kinds of cells, equivalent to collagen. So silk fibroin can be used for cell scaffold material of tissue engineering, and can be applied to several fields such as tissue engineering of skin, cartilage and blood vessel. The related researches and the prospect of the application of silk fibroin in cell scaffold of tissue engineering are reviewed in this paper.

Animals↗
PubMed1991

[Survival ability of genetically engineered strains of Escherichia coli. 1. Physiological characterization and the effect of different physiochemical conditions].

Two genetically engineered E. coli strains L+ and CAG+ possessing the ability to produce the enzyme Pro-urokinase and showing additionally ampicillin resistance, and wild-strains L- and CAG-, were characterized using 328 physiological tests. Their test profiles were compared with those of 30 clinical and nonclinical E. coli isolates. This biotyping made a differentiation and recognition of the genetically manipulated strains possible. It also allowed distinguishing them from the other tested isolates. The genetically engineered strains showed a narrower activity spectrum compared with their wild-strains. However, based on differentiating characteristics, all strains could be clearly biochemically identified as E. coli. Under different laboratory test conditions (organic load, pH, salt content, temperature), the E. coli strains showed no striking features or peculiarities with respect to their survival compared to data from literature. However, low pH (pH less than 5), high salt content (greater than 7%) as well as low (less than 8 degrees C) and high (greater than 37 degrees C) incubation temperatures clearly reduced their ability to survive. Apart from a few exceptions (e.g. survival of strain L+ at 44 degrees C and pH 7 with high cell densities), the survival of the genetically engineered strains corresponded to that of the control and wild-strains. Both CAG strains, especially the genetically manipulated strain CAG+, showed in many cases reduced viability compared with the other strains.

Bacterial Typing Techniques↗
PubMed1988

Monoclonal antibodies as probes of conformational changes in protein-engineered cytochrome c.

Determination of the nature of the antigen-antibody complex has always been the ultimate goal of three-dimensional epitope mapping studies. Various strategies for epitope mapping have been employed which include comparative binding studies with peptide fragments of antigens, binding studies with evolutionarily related proteins, chemical modifications of epitopes, and protection of epitopes from chemical modification or proteolysis by antibody shielding. In this study we report the use of protein engineering to modify residues in horse cytochrome c that are in or near the epitopes of four monoclonal antibodies specific for this protein. The results demonstrate not only that site-specific changes in the antigen binding site dramatically affect antibody binding, but, more importantly, that some of the site-specific changes cause local and long-range perturbations in structure that are detected by monoclonal antibody binding at other surfaces of the antigen. These findings emphasize the role of native conformation in the stabilization of the interaction between protein antigens and high affinity monoclonal antibodies. Furthermore, the results demonstrate that monoclonal antibodies are more sensitive probes of changes in conformation brought about by protein engineering than low resolution spectroscopic methods such as circular dichroism, where similar spectra are observed for all the analogues. These findings suggest a role for monoclonal antibodies in detecting conformational changes invoked by nonconservative amino acid substitutions or substitutions of evolutionarily conserved residues in protein-engineered or recombinant proteins.

Animals↗
PubMed1989

The theory and design of piezoelectric/pyroelectric polymer film sensors for biomedical engineering applications.

The unique properties of piezoelectric/pyroelectric polymers offer many new opportunities for biomedical engineering sensor applications. Since their discovery nearly 20 years ago, the polymer films have been used for many novel switching and sensor applications. Despite the prodigious exposure from many recent publications describing piezo film applications, methods of sensor fabrication and circuit interfacing still elude most engineers. This paper is presented as a tutorial guide to applying piezo polymers to biomedical engineering applications. A review of the fundamentals of piezoelectricity/pyroelectricity in piezo polymers is first presented. Their material properties are contrasted with piezoelectric ceramic materials. Some advantages and disadvantages of the films for biomedical sensors are discussed. Specific details on the fabrication of piezo film sensors are presented. Methods are described for forming, cutting, and mounting film sensors, and making lead connections. A brief discussion of equivalent circuit models for the design and simulation of piezoelectric/pyroelectric sensors is included, as well as common circuit interface techniques. Finally, several sources are recommended for further information on a variety of biomedical sensor applications.

Biomedical Engineering↗
PubMedDate not supplied

Clinical engineering standards, obligations, and accountability.

The growing volume and complexity of biomedical equipment in hospitals are creating legal implications for the clinical engineer. Statutory regulations, court decisions on product liability, and the patient's right to privacy and confidentially affect daily operations. The doctrines of agency, negligence, strict liability, and breach of contract, plus the medical Device Amendments of 1976 to the Federal Food, Drug, and Cosmetic Act, and the Joint Commission on Accreditation of Hospitals' 1976 standards, complicate the conventional clinical engineering functions. The need for the clinical engineer to be alert to his legal obligation is assessed.

Biomedical Engineering↗
PubMed1988

A survey of persons certified in clinical engineering and their thoughts on the profession.

A questionnaire was sent to 346 persons certified in clinical engineering (CCEs) worldwide. An impressive 72% return revealed the following: 57% of the CCEs are employed by hospitals, 15% by manufacturers, and 12% by academic institutions; 13% are consultants in private practice. Half of them have been with their current employer for over 9 years; their average age is 44.3 years. Thirty-six percent left hospitals for their present jobs. The median salary of the hospital-based CCEs was in the range of +40,000-45,000/year, whereas that of their non-hospital counterparts was in the range of +50,000-55,000/year. Of the nonhospital CCEs, 25% earned over +70,000/year, while only 3% of the hospital CCEs earned salaries in this category. The mean age of the hospitals CCEs is, however, 4.8 years less than that of the non-hospital CCEs. Although some comments on the profession were particularly critical, the respondents believed strongly that clinical engineering remains a viable career choice and has contributed significantly to health care. Underutilization of clinical engineering talents, particularly in the hospital setting, continues to be the predominate concern and greatest source of job-related frustration.

Adult↗