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PubMedDate not supplied

[Physiology of microbial cell and metabolic engineering].

This review is devoted to the problems of the physiology and cell biology of microorganisms in relation to metabolic engineering. The latter is considered as a branch of fundamental and applied biotechnology aimed at controlling microbial metabolism by methods of genetic engineering and classical genetics and based on intimate knowledge of cell metabolism. Attention is also given to the problems associated with the metabolic limitation of microbial biosyntheses, analysis and control of metabolic fluxes, rigidity of metabolic pathways, the role of pleiotropic (global) regulatory systems in the control of metabolic fluxes, and prospects of physiological and evolutionary approaches in metabolic engineering.

Genetic Engineering↗
PubMed2000

[Progress in the field of tissue engineering].

Tissue engineering is a new field in biomedical engineering. In this review, progress in the field of tissue engineering is presented in detail, including a general introduction, design and fabrication principles, key technologies, various applications, new directions, as well as related market and R&D issues.

Animals↗
PubMed2001

[Expression of endogenic bone morphogenetic protein in repairing rabbit skull with tissue engineering technique].

OBJECTIVE: To explore the distribution and effect of endogenic bone morphogenetic protein (BMP) in repairing rabbit skull with tissue engineered bone. METHODS: The autologous osteoblast-like cells were instantly implanted onto polyglycolic acid (PGA) matrix coated with collagen. The rabbit skull defect models were established by resection of bilateral 1.5 cm x 1.0 cm full-thickness parietal bone in 18 New Zealand rabbits, which were randomly divided into two groups. In one group, the composite of osteoblast- like cells and PGA matrix were grafted into the defect on one side of the skull as experimental group I, leaving the same defect area on the other side as control group without any graft implanted. In the other group, simply PGA was done in the same way as experimental group II. The tissue samples were harvested at 3, 8 and 14 days postoperatively and examined by histological and immunohistochemistry methods. The concentrations of BMP in different regions of the samples were measured using computer image analysis system. RESULTS: After 3 days of operation, the BMP positive cells were found in the matrix of experimental group I. At 8 days postoperatively, the formation of new bone on experimental group I was prior to that of experimental group II and control group. On the 14th day, bone trabecula was formed on the experimental group I, but there was only fibrous tissue on control group. The concentration of BMP on the experimental group I and II were higher than that of corresponding region on control side. CONCLUSION: The osteoblast-like cells instantly implanted onto PGA matrix can synthesize and secrete BMP. It may be one of the reasons of tissue engineered bone inducing new bone regeneration that localizing endogenic BMP in bone defect area, increasing the concentration of endogenic BMP and improving its distribution by tissue engineering technique.

Animals↗
PubMed2001

[The current situation and future of extracellular matrix materials for bone tissue engineering].

The requirements of ideal extracellular matrix materials for bone tissue engineering were stated, and the advantages and disadvantages of bioceramics, biodegradable synthetic polymers and natural polymers were analyzed. Based on these, we highlight a point that the ideal extracellular matrix materials for bone tissue engineering should be made up of bioceramics materials, synthetic polymers or natural polymers. These materials should possess a morphological structure of three-dimensional foam and have a self-mediated drug delivery system of bone growth factors. The design and manufacture of such compound extracellular matrix materials for bone tissue engineering is a very important and urgent challenge.

Biocompatible Materials↗
PubMed2001

Muscle-based gene therapy and tissue engineering.

The development of new biological approaches based on cell and gene therapies, in combination with tissue engineering, may create innovative ways to treat various tissues of the musculoskeletal system. It is vital for practicing orthopaedic surgeons to understand the terminology, fundamental concepts, and current research in this burgeoning field so that they may practice their discipline in its fullest form. Such techniques, coupled with advances in cell biology and polymer chemistry, are resulting in novel approaches to treating musculoskeletal disorders in which surgeons, who have traditionally used the tools of excision and reconstruction to treat patients, may now serve as surgical gardeners who create microenvironments that are conducive for tissue regeneration. Gene therapy and tissue engineering applications for bone healing, articular disorders, and skeletal muscle diseases and injuries are currently being explored. This review is intended to update readers on the principles and current advances in muscle-based gene therapy and tissue engineering for the musculoskeletal system.

Animals↗
PubMed2001

[Formation of the allogeneic tissue engineered cartilage using injectable biomaterial].

OBJECTIVE: To study the feasibility of the formation of allogeneic tissue-engineered cartilage of certain shape in immunocompetent animal using the injectable biomaterial. METHODS: Fresh newborn rabbits' articular cartilages were obtained under sterile condition (< 6 hours after death) and incubated in the sterile 0.3% type II collagenase solution. After digestion of 8 to 12 hours, the solution was filtered through a 150 micron nylon mesh and centrifuged, then the chondrocytes were washed twice with phosphate buffered saline (PBS) and mixed with the biomaterial to create a final cell density of 5 x 10(7)/ml. The cell-biomaterial admixture was injected into rabbits subcutaneously 0.3 ml each point while we drew the needle back in order to form the neocartilage in the shape of cudgel, and the control groups were injected with only the biomaterial or the suspension of chondrocytes with the density of 5 x 10(7)/ml. After 4, 6, 8 and 12 weeks, the neocartilages were harvested to analyze. RESULTS: The new nodes could be touched subcutaneously after 2 weeks. In the sections of the samples harvested after 4 weeks, it was found that the matrix secreted and the collagen formed. After 6 weeks and later than that, the neocartilages were mature and the biomaterial was almost completely degraded. The cudgel-shaped samples of neocartilage could be formed by injection. In the experiment group, there was no obvious immune rejection response. On the contrary, there were no neocartilage formed in the control group. CONCLUSION: The injectable biomaterial is a relatively ideal biomaterial for tissue engineering, and it is feasible to form allogeneic tissue engineered cartilage of certain shape by injection in an immunocompetent animal.

Animals↗
PubMed2001

[Experimental study of tissue engineered bone with coralline hydroxyapatite as scaffolds].

OBJECTIVE: To investigate the feasibility of coralline hydroxyapatite (CHA) as scaffolds in bone tissue engineering. METHODS: The bone marrow stromal cells from 4-month New Zealand rabbits were harvested and cultured in vitro. After multiplied, dexamethasone was used to promote the osteoblastic phenotype of the cells. The cells were harvested and then seeded into CHA. By means of tissue engineering technique, osteoblastic cells/CHA complex were formed. The complex were implanted subcutaneously in nude mice. The CHA alone was implanted as control. Bone regeneration was assessed 6, 8 weeks after implantation by histological and roentgenographic analysis. RESULTS: After six weeks of implantation, x-ray film showed high-density signal, osteoid tissue formed under histological examination. Large amount of new bone were formed and connected to trabecularism 8 weeks after implantation in the experimental group. While in the control group, there were no new bone formation, but amount of fiber tissue grew into the pore of CHA 8 weeks after implantation. CONCLUSION: CHA may be used as a good scaffold material for bone tissue engineering.

Animals↗
PubMed2001

Lack of calcification of tissue engineered heart valves in juvenile sheep.

The presence of viable endothelial cells may support longer durability and the absence of calcification in valve prostheses. This study shows the development of a tissue engineered heart valve, constructed from viable autologous endothelial cells on an acellular matrix and its evaluation in juvenile sheep. In 3-month-old sheep (n = 8) a piece of vein was harvested to culture autologous endothelial cells. A porcine acellular matrix was reendothelialized and implanted in juvenile sheep as pulmonary interposition. The valves were explanted after 1 week, 3 and 6 months. Examination was performed by X-ray, light microscopy, and atomic absorption spectrometry. Reendothelialization mean rate was 10.3 x 10(5) cells/cm(2) with a mean endothelial cell viability of 95.5% (0.98 x 10(5) cells/cm(2)). X-ray examination showed no cusp calcification at 1 week, 3 and 6 months, which was confirmed by light microscopy. Immunostaining for factor VIII demonstrated colonization of viable mature autologous endothelial cells on the heart valve after the seeding process. The atomic absorption spectrometry showed no significant increase of the calcium content after 3 (P value >.1) and 6 months (P value >.1) compared with nonimplanted tissue engineered heart valves. The tissue engineered valve showed no cusp calcification in the juvenile sheep after 3 and 6 months.

Animals↗
PubMed1998

[Tissue engineering of hyaline cartilage].

OBJECTIVE: To study the new way to repair the defect of the articular cartilage. METHOD: The articular-epiphyseal cartilage complexes from 8 newborn rabbits were enzymatically dissolved, and the chondrocytes were seeded onto the fibrous chitin mesh in a 96-well plate in DMEM medium. RESULT: Cultured for 21 days, the "membrane-like cartilage" was strong enough to be transferred. At the 110th day, the semitransparent cartilage discs were 4.4 mm in diameter and 14.8 mg in weightness. Staining of SatranO showed that engineered "cartilage" was bound of GAGs and the chondrocytes expressed the mRNA of type II collagen by in situ hybridization, which is resemble to that of the normal hyaline cartilage beside the biodegraded fibrous chitin embedded in. The "membrane-like cartilage" cultured for 21 days was grafted into the articular cartilage defects of knee of adult rabbits. Seven of 9 defects healed with new cartilage and the structure was well organized in 16 weeks. CONCLUSION: The biodegradable fibrous chitin is a good "matrix" for cartilage tissue engineering. The engineered "cartilage" is true hyaline cartilage, which is a new "alive cartilage tissue" for the repairment of the defect of articular cartilage.

Animals↗
PubMed1999

[Bone tissue engineering seeded with bone marrow stromal cells].

OBJECTIVE: To assess the ability of bone graft substitutes to support the growth of cells in vitro and new bone formation in vivo. METHODS: The methods of tissue engineering were employed, the bone marrow derived stromal cells were seeded onto blocks of hydroxypatite (HA), cultured for two weeks, and implanted intermuscularly into the rabbit back muscle, scanning electron microscopy and undecalcified bone tissue sections were used to evaluate the the growth of cells in vitro and new bone formation in vivo. RESULTS: The stromal cells were attached to and grew upon the surface of the periphery HA pores, especially in the pores adjacent to the bottom of culture flasks. No cell growth was found on the surface of the central pores. At four weeks after implantation, new bone formation was observed in most HA blocks, almost all of the new bones were lamellar bone and deposited directly on the surface of the HA pore. Active osteoblast and osteoid were found on the surface of the newly formed bone, invasion of bone marrow was observed in some newly formed bone. CONCLUSION: Bone marrow stromal cells are potentially the source of seeded cells for use in bone tissue engineering, and the HA may be considered as a suitable scaffold for these cells. The findings may be useful for detailed researches on seeded cells, scaffold and implanting fashion of bone tissue engineering.

Animals↗
PubMedDate not supplied

[Bioethics in genetic engineering].

The advances in the field of molecular biology and genetics have widened the possibilities for the diagnosis and treatment of hereditary diseases. At the same time research into this field has broken bounds of its legal and ethical regulation. The intention of this paper is not to analyze these advances from scientific and technical point of view which is the area of the specialist, but rather to review historical antecedents of genetic engineering; the legal and ethical repercussions of the human genome project (HGP); in vitro fertilization and embryo transfer (FIVET); the embryo research which is being caused out and which may be possible; other fields of genetics and cloning especially germinal cells and human beings; genetic diagnosis and its family, social and work repercussions; treatment through genetic engineering, research into cloning in order to obtain organs and tissues for transplants; and the use of genetic engineering in the biomedical industry. To avoid these advances working against humans, the organization and participation of multidisciplinary bodies are required to provide legal and ethical supervision.

Bioethical Issues↗
PubMed2002

Medical informatics: between science and engineering, between academia and industry.

OBJECTIVE: To analyze the nature and appropriate role of the Medical Informatics research and practice area in the 21st Century, and to determine its links to academic environments versus industrial companies and health-care organizations. METHODS: A qualitative analysis of the state of the art of Medical Informatics, based on observation of current medical informatics programs and research in academic and industrial sites. RESULTS AND CONCLUSIONS: Medical Informatics is definitely a scientific and technological area of endeavor, although somewhat ill-defined in scope. It is situated between science and engineering, but much closer to the engineering world, and its multidisciplinary nature fits well the engineering paradigm. It is better viewed as a specialization of the informatics field rather than as a basic medical science. However, there are good arguments as to why Medicine should be the first among equals to have its own informatics domain. Medical Informatics must have extensions to both academia and industry to survive. Medical informaticians, whether implicitly or explicitly, exist in three different environments: academic, clinical (user), and industrial (informatics developer); all three environments must be considered when trying to predict the future of this new multidisciplinary area.

Engineering↗
PubMed1998

[Evaluation of penicilloyl proteins of allergic impurity in gene engineering drugs].

It is well known that penicillins are necessary for prevention of contamination during cell culture or fermentation in the production of gene engineering drugs. As penicillins are easily combined with proteins forming allergic impurities, the benzyl penicilloyl proteins in aqueous solution, an evaluation system should be established for control of the gene engineering drugs. An enzyme linked immunosorbent assay (ELISA) with high specificity and high sensitivity in vitro, by which the conjugated penicillins of 0.3 ppm in a sample could be detected and a passive cutaneous anaphylaxis (PCA) test, a classical method for evaluation of allergic reaction in vivo are integral parts of this system. Some domestic gene engineering drugs such as erythropoietin (EPO), G-CSF, GM-CSF and 125SerIL-2 are evaluated with this system. No matter whether the expression products was produced in secretion manner or in inclusion body, it was possible that some residues of allergic impurities may remain in the finished products if an unsuitable process of isolation and purification was used. The maximum absolute content of the conjugated penicillins in a sample was up to about one per thousand.

Animals↗
PubMed2002

[Progress in studies of tissue-engineered heart valves].

Valve replacement represents the most common surgical therapy for valvular heart diseases. However, the long-term results of the valve protheses in clinical use are not satisfying. Recently, with the development of tissue engineering, more and more studies are focusing on creating ideal valve substitutes through seeding autologous cells on biodegradable scaffold. This article describes the definition of valvular tissue engineering, the choice of scaffold biomaterials, the methods of cell culture and seeding, and the evaluation of tissue-engineered heart valves. Furthermore, the problems which should be resolved in the future are also presented in the article.

Animals↗
PubMed2002

[Repair of porcine full-thickness skin defects with autologous tissue engineered skin].

OBJECTIVE: To explore a feasible method to repair full-thickness skin defects with tissue engineered techniques. METHODS: The skin specimens were cut from the Changfeng hybrid swines' abdomen, then keratinocytes and fibroblasts were isolated and harvested by trypsin, EDTA and type II collagenase. The cells were seeded in petri dishes for primary culture. When the cells were in logarithmic growth phase, they were treated with dispase II (keratinocytes) or trypsin (fibroblasts) to separate them from the floor of the tissue culture dishes. A biodegradable material-pluronic F-127 was prefabricated and mixed with these cells, and then the cells-pluronic compounds were seeded evenly into polyglycolic acid (PGA). Tinally the constructs were replanted to autologous animals to repair full-thickness skin defects. Histological changes were observed in 1, 2, 4 and 8 weeks postsurgery. RESULTS: The cells-pluronic F-127-PGA compounds could repair autologous full-thickness skin defects. Histologically, the tissue engineered skin was similar to normal skin with stratified epidermis overlying a moderately thick collageneous dermis. CONCLUSION: Tissue engineered skin can repair autologous full-thickness skin defects with primary-cultured keratinocytes and fibroblasts as seed cells and PGA as a cell carrier.

Animals↗
PubMed2000

[Tissue engineering of skin].

OBJECTIVE: To review the recent progresses on tissue engineering of skin. METHODS: Recent original articles about tissue engineering of skin were extensively reviewed, which focused on the progresses and major problems concerning the epidermal substitutes, dermal substitutes, cultured-epidermal composite skin graft. RESULTS: Most investigators had come to conclusion that the optimal skin substitute should provide for immediate reconstruction of both the lost epidermis and dermis. The research was mainly focused on how to transplant epidermal cells immediately, preserve their activity and function, and develop the extracellular matrix which could effectively accelerate the function of transplanted cells, induce vascular growth from the wound bed, could be biodegradable, no toxicity and no danger of carrying pathogen. CONCLUSION: The major research trends of tissue engineering of skin should be focused on the study of immediate transplantation of epidermal cells, accelerate wound healing and developing extracellular matrix of dermis.

Cell Transplantation↗
PubMed1999

[A review on the application of myoblast on gene therapy and tissue engineering].

OBJECTIVE: Because of its special biological characteristics, myoblast might play a role in gene delivery and cell-to-biomaterial interactions. In this paper, the biological features of myoblast and its application on gene therapy and tissue engineering was discussed. METHODS: Documents about proliferation and differentiation of myoblast were reviewed in details. The prospects of its application on gene therapy and tissue engineering were also presented. RESULTS: Myoblast was important in muscle regeneration. The activation of myoblast to proliferate and differentiate was the very beginning of regeneration after injury. The cultured myoblast had high potential to proliferate, it was ready to fuse with each other and to form myotube (the special behavior of myoblast differentiation). Myoblast transplantation had been studied as a possible treatment for inherited myopathies, such as Duchenne muscular dystrophy. The transplanted myoblast could fuse with host myofibers, so the delivered target gene integrated into host. Several myoblast-mediated gene delivery system had been established, including the gene delivery of human factor IX (hFIX), erythropoietin (EPO) and clony stimulating factor-1 (CSF-1). Results from animal experiments demonstrated that myoblast-mediated gene delivery could be used as gene therapy for some inherited diseases. And recently, some authors have shown great interest in the interaction between myoblast and type I collagen gels. It was found that myoblast could keep on proliferating and differentiating in collagen gels and could form discoid, tubular materials. CONCLUSION: Myoblast has great importance in gene therapy and tissue engineering. It is suggested that more efforts should be made in this field.

Cell Transplantation↗
PubMed2000

[Development of biodegradable polymer scaffolds for bone tissue engineering].

OBJECTIVE: To investigate the selection and manufacture of ideal extracellular matrix materials in bone tissue engineering. METHODS: The recent literatures about biodegradable polymers served as culture scaffolds of osteoblasts were widely reviewed, the advantages and disadvantages of biodegradable synthetic polymers and natural polymers were analysed. RESULTS: The ideal extracellular matrix material in bone tissue engineering should be made up of inorganic materials, synthetic polymers and natural polymers, which possesses morphological structure of three-dimensional foam with self-mediated drug slow delivery system of bone growth factors. CONCLUSION: The design and manufacture of combined extracellular matrix materials in bone tissue engineering is a very important and urgent challenge.

Absorbable Implants↗