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PubMed2005

Molecular aspects of vascular tissue engineering.

Cardiovascular disease remains the number one cause of death in the United States. Most current surgical procedures to alleviate this disease rely on the availability of suitable small diameter vascular grafts, which are constrained by several limitations. Tissue engineering brings new hope to this field, but still faces many challenges. This review focuses on the molecular aspects of the different components of vascular tissue engineering. The topics addressed include the cell type, extracellular matrix, and physical and biochemical stimulation with respect to their role in the development of a tissue engineered vascular graft.

Animals↗
PubMedDate not supplied

The importance of certification/registration in expanding engineering career opportunities.

The difficulties of the engineering profession in exploiting to the full the opportunities available to it are not due to the oft-repeated and reputed lack of academic/industrial orientation and liaison. I am convinced that the reasons are due to present-day attempts to guide the profession in a characteristically multiprofessional world by inapplicable, restrictive and inhibitive uni-professional concepts and principles. The Engineering Council in particular should evolve active, rather than passively reactive means of recognizing and encouraging multi-professional team efforts on a much wider spectrum of activities than at present. This spectrum should, in particular, recognize the Health Service as the industry pertinent to biomedical engineering. The way forward lies in pre-experience registration of the newly qualified, followed by training 'on-the-job' accredited by the professional Institutions, culminating in 'certified' specialties. The process of accreditation/certification should be flexibly designed so as to permit changes of specialty orientation and even that of total career content.

Certification↗
PubMedDate not supplied

Role of the clinical engineer in patient monitoring services.

The basic role of a clinical engineer is to provide safe and effective management and application of technology within patient care settings. In the UK the total number of such people is still relatively small. Clinical engineering as a profession requires a proper career structure and professional status. This can be achieved only by the support of a professional body such as the Biological Engineering Society.

Biomedical Engineering↗
PubMed1988

New approaches to animal vaccines utilizing genetic engineering.

Control of infectious diseases in livestock is an important determinant in the success of a nation's effort to efficiently meet its need for animal products. Genetic engineering offers many new options in the design of animal vaccines. Monoclonal antibodies, DNA cloning, recombination, and transfection are examples of techniques that facilitate innovative strategies in antigen identification, production, and delivery. This article reviews the use of genetic engineering in the production of vaccines directed against foot-and-mouth disease virus and other important pathogens of animals. The advantages and disadvantages of vaccines produced through the use of genetic engineering are discussed.

Animal Diseases↗
PubMed2001

Growth factor delivery for bone tissue engineering.

Bone is a dynamic tissue that undergoes significant turnover during the life cycle of an individual. Despite having a significant regenerative capability, trauma and other pathological scenarios commonly require therapeutic intervention to facilitate the healing process. Bone tissue engineering, where cellular and biological processes at a site are deliberately manipulated for a therapeutic outcome, offers a viable option for the treatment of skeletal diseases. In this review paper, we aim to provide a brief synopsis of cellular and molecular basis of bone formation that are pertinent to current efforts of bone healing. Different approaches for engineering bone tissue were presented with special emphasis on the use of soluble (diffusible) therapeutic agents to accelerate bone healing. The latter agents have been used for both local bone repair (i.e. introduction of agents directly to a site of repair) as well as systemic bone regeneration (i.e. delivery for regeneration throughout the skeletal system). Critical drug delivery and targeting issues pertinent for each mode of bone regeneration are provided. In addition, future challenges and opportunities in bone tissue engineering are proposed from the authors' perspective.

Bone Morphogenetic Proteins↗
PubMed1999

Genetically engineered polymers for drug delivery.

Genetic engineering methodology offers the ability to synthesize protein-based polymers with precisely controlled structures. Protein-based polymers synthesized by recombinant techniques have a well-defined monomer composition and sequence, stereochemistry, and a narrow molecular weight distribution. The structure of the polymeric carrier at the molecular level influences its biological disposition and drug release profile. Current methodologies of polymer synthesis (chemical polymerization) result in the production of polymers with heterogeneous molecular weights, and with monomer sequences and compositions defined in terms of statistical distributions. Genetic engineering methodologies can be used to design new polymeric drug carriers with improved properties, such as better-defined biorecognition, pharmacokinetic, biodegradation, and drug release profiles. In this review article the rationale and methodology of polymer synthesis using genetic engineering techniques, the status of such polymers in drug delivery to-date, and the potential of these polymers for the development of new systems in the future are discussed.

Drug Delivery Systems↗
PubMed2000

Tissue engineering of urinary organs.

Tissue engineering can serve as an alternative treatment for a malfunctioning or lost organ. Isolated and expanded cells adhere to a temporary scaffold, proliferate, and secrete their own extracellular matrices (ECM) replacing the biodegrading scaffold. The genitourinary system, composed of the kidney, ureter, bladder, urethra, and genital organs, is exposed to a variety of possible injury sites from the time of fetal development. All the urinary organs are mainly composed of smooth muscle and uroepithelial cells and which may be approached by tissue engineering techniques. A large number of materials, including naturally-derived and synthetic polymers have been utilized to fabricate prostheses for the genitourinary system. Usually, whenever there is a lack of native urologic tissue, reconstruction is considered with native non-urologic tissue, such as, gastrointestinal segments, or skin or mucosa from multiple body sites. Engineering tissues using selective cell transplantation may provide a means to create functional new genitourinary tissues. This review concerns urinary tissues reconstructed with bladder uroepithelial cells and smooth muscle cells (SMCs) implanted on biodegradable polymer matrices.

Animals↗
PubMed2000

Tissue engineering applications in the genitourinary tract system.

The concept of cell transplantation using tissue engineering techniques has provided numerous possibilities in the area of urologic tissue reconstruction. Tissue engineering applications in the genitourinary tract system have been investigated in almost every tissue in order to improve, restore and replace existing tissue function. Although most reconstructive efforts still remain in the experimental stage, several technologies have been transferred to the bedside with satisfactory outcome. In this article, we describe tissue engineering approaches attempted in the genitourinary system for reconstruction.

Animals↗
PubMed2000

Viability evaluation of engineered tissues.

Biohybrid artificial organs encompass all devices capable of substituting for an organ or tissue function and are fabricated from both synthetic materials and living cells. The viability of engineered tissue could be related to the viability of implanted cells. The system of viability assay for mammalian cell culture can be applied to the determination of cell viability for engineered tissue. This review explores various methods of cell viability assay which can be applied to the viability evaluation of engineered tissue. The major criteria employed in viability assays include survival and growth in tissue culture, functional assay, metabolite incorporation, structural altercation, and membrane integrity. Each viability assay method is based on different definitions of cell viability, and has inherent advantages and disadvantages. In order to be able to assess the viability of cells with one assay method, it is desirable to compare the viability measurements from various assays derived from different criteria.

Animals↗
PubMed2005

In vivo noninvasive monitoring of a tissue engineered construct using 1H NMR spectroscopy.

Direct, noninvasive monitoring of tissue engineered substitutes containing live, functional cells would provide valuable information on dynamic changes that occur postimplantation. Such changes include remodeling both within the construct and at the interface of the implant with the surrounding host tissue, and may result in changes in the number of viable cells in the construct. This study investigated the use of 1H NMR spectroscopy in noninvasively monitoring the viable cell number within a tissue engineered construct in vivo. The construct consisted of mouse betaTC3 insulinomas in a disk-shaped agarose gel, surrounded by a cell-free agarose gel layer. Localized 1H NMR spectra were acquired from within implanted constructs, and the total choline resonance was measured. Critical issues that had to be addressed in accurately quantifying total choline from the implanted cells included avoiding signal from host tissue and correcting for interfering signal from diffusing solutes. In vivo NMR measurements were correlated with MTT assays and NMR measurements performed in vitro on explanted constructs. Total choline measurements accurately and noninvasively quantified viable betaTC3 cell numbers in vivo, in the range of 1 x 10(6) to more than 14 x 10(6) cells, and monitored changes in viable cell number that occurred in the same construct over time. This is the first study using NMR techniques to monitor viable cell numbers in an implanted tissue substitute. It established architectural characteristics that a construct should have to be amenable to NMR monitoring, and it set the foundation for future in vivo investigations with other tissue engineered implants.

Animals↗
PubMed2001

Specific immunotherapy by genetically engineered APCs: the "guided missile" strategy.

We tested the hypothesis that APCs genetically engineered to present an Ag and to express Fas ligand (FasL) simultaneously can target and eliminate Ag-specific T cells. Transgenic T cells specific for influenza hemagglutinin (HA) were used as targets. We prepared recombinant vaccinia virus vectors (VVV) to transfer the gene constructs individually or simultaneously into APCs. We prevented unwanted viral replication by attenuating the VVVs with psoralen-UV light treatment. For presentation of the HA Ag, APCs were transduced with cDNA for HA flanked by sequences of the lysosome-associated membrane protein that direct efficient processing and presentation of the Ag by APCs. As a "warhead" for the APCs, we transduced them with the gene for FasL, which induces apoptosis of Fas-expressing activated T cells. To protect the transduced APCs from self-destruction by FasL, we transferred cDNA for a truncated form of Fas-associated death domain, which inhibits Fas-mediated cell death. Our results show that the engineered APCs effectively expressed the genes of interest. APCs transduced with VVV carrying all three gene constructs specifically killed HA-transgenic T cells in culture. Coculture with T cells specific for an unrelated Ag (OVA) had no significant effect. Our in vitro findings show that APCs can be genetically engineered to target and kill Ag-specific T cells and represent a promising novel strategy for the specific treatment of autoimmune diseases.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Tissue engineering.

Wound care has become one of the first fields to see the benefit of a new technology: tissue engineering. Tissue engineering involves the development of new materials or devices capable of specific interactions with biological tissues. In wound care, these materials may be based entirely on naturally occurring tissues and cells, or may be materials that combine synthetics, usually polymers, with biological layers. Both wound dressings and skin substitutes are available. The complexity of the materials depends on the end uses. Generally, synthetics made from polymeric materials such as Tegaderm and Opsite are used as wound dressings over relatively simple and shallow wounds or as coverings over more complex dressings. Their function is one of protection from water loss, drying, and mechanical injury. More complex dressings vary from dermal replacements made of reconstituted collagen and chondroitan sulfate backed by a polymer layer such as Integra(R) to the complex Apligraftrade mark that contains collagen and seeded cells. This last is designed as a complete skin replacement or skin substitute. Ultimately, engineered skin will contain all of the components necessary to modulate healing and provide the desired response: a wound closed with limited scar tissue that retains all of the characteristics of natural skin.

Biocompatible Materials↗
PubMed1999

Spontaneous and engineered mutant mice as models for experimental and comparative pathology: history, comparison, and developmental technology.

During the last half-century pathologists have explored the biologic mechanisms associated with inherited human and veterinary diseases by using inbred and inbred mutant (spontaneous) strains of mice. The first successful gene transfer to mice by pronuclear injection of the herpes simplex virus thymidine kinase gene and rabbit and human beta-globulin genes was achieved in the early 1980s. This accomplishment was followed a few years later with the creation of a mouse bearing a disrupted hypoxanthine phosphoribosyl transferase (hrpt) gene (targeted mutation based on ES cell blastocyst injection). Since then, hundreds of genetically engineered models of biomedical importance have been created. The unprecedented scale and scope of development of engineered models present great opportunities as well as experimental challenges to the investigator. The aim of the present review is to provide a framework of information on engineered mouse models from the perspective of experimental and comparative pathology research. Sections include: 1) a brief historical account of the development of mouse models of disease, with increasing progression of genetic refinement as represented by inbred (spontaneous) and congenic (targeted) mutant strains of mice; 2) a synopsis of spontaneous and targeted mutations, with anecdotal examples of expression of individual genes and interactions between multiple mutant genes; 3) selected examples of targeted mutations of interest to developmental and cancer biologists and immunologists; 4) an overview of the technology of development of transgenic mice; and 5) an introduction to on-line database resources of current multi-species genomic information.

Animals↗
PubMed1984

Radiology inhouse engineering.

In summary, a brief discussion of the advantages and disadvantages of inhouse radiology engineering has been presented. There are potential dollars to be saved, as well as the possibility of improving the quality of care we provide. If an institution cannot support an engineering program by themselves, a shared program should be considered. As legislation continues to impact imaging, we must consider different ways to accomplish our tasks: inhouse radiology engineering is one program that may warrant investigation.

Cost-Benefit Analysis↗
PubMedDate not supplied

Tissue engineering and the development of Apligraf a human skin equivalent.

In recent years, skin grafting has evolved from the initial autograft and allograft preparations to biosynthetic and tissue-engineered living skin replacements. This review details the pioneering work of numerous investigators that led to the following precursors of tissue-engineered skin replacement: cultured autologous keratinocyte grafts, cultured allogeneic keratinocyte grafts, autologous/allogeneic composites, acellular collagen matrices, and cellular matrices. It also discusses the rationale for the development of the newer products and describes the technical advances leading to the development of Apligraf, a tissue-engineered human skin product.

Biomedical Engineering↗
PubMed1999

Gene-enhanced tissue engineering: applications for bone healing using cultured periosteal cells transduced retrovirally with the BMP-7 gene.

Periosteum has cell populations, including osteoprogenitor and chondroprogenitor cells, that can be grown in cell culture and form both bone and cartilage under appropriate conditions. The authors have shown previously that cultured periosteal cells can be used in the tissue engineering of bone, and they demonstrated substantial bone formation in a rabbit cranial defect model. In the current study, principles of tissue engineering were combined with principles of gene therapy to produce cultured periosteal cells transduced retrovirally with the bone morphogenetic protein 7 (BMP-7) gene to be used in the treatment of bone defects. Human BMP-7 complementary deoxyribonucleic acid was generated from a cell line using reverse transcription polymerase chain reaction and cloned into a retroviral vector plasmid. Retroviral vector particles were then used to transduce New Zealand White rabbit periosteal cells. Transduced periosteal cells demonstrated substantial production of both BMP-7 messenger ribonucleic acid by Northern blot analysis and BMP-7 protein by enzyme-linked immunosorbent assay. These cells were then seeded into polyglycolic acid (PGA) matrices and used to repair critical-size rabbit cranial defects. At 12 weeks, defect sites repaired with BMP-7-transduced periosteal cells/PGA had significantly increased radiographic and histological evidence of bone repair compared with those defect sites repaired with negative control-transduced cells/PGA, nontransduced cells/PGA, PGA alone, or unrepaired defects. Thus, this study demonstrates successfully a tissue engineering approach to bone repair using genetically modified cells.

Animals↗
PubMed1999

Characterization of a novel stable biocatalyst obtained by protein engineering.

Protein engineering is a powerful tool for the improvement of the properties of biocatalysts. Previously we have applied protein engineering technologies to obtain an extremely stable variant of the thermolysin-like protease from Bacillus stearothermophilus [Van den Burg, Vriend, Veltman, Venema and Eijsink (1998) Proc. Natl. Acad. Sci. U.S.A. 95, 2056-2060]. This variant is much more resistant to denaturing conditions (temperature and denaturing agents) than the wild-type enzyme. An extensive enzymic characterization was undertaken to explore the suitability of the variant as a biocatalyst at high temperatures. By comparing a range of variants with increasing thermal stabilities we show that the additivity of the mutations is accompanied by an increase in activity at elevated temperatures in accordance with the Arrhenius law. The results suggest that the constructed protease variants could be suitable alternatives to proteases that are currently used industrially. Our studies demonstrate how protein engineering can be exploited to obtain high-performance biocatalysts.

Catalysis↗
PubMed2000

Engineering of coordinated up- and down-regulation of two glycosyltransferases of the O-glycosylation pathway in Chinese hamster ovary (CHO) cells.

Production of O-linked oligosaccharides that interact with selectins to mediate cell-cell adhesion occurs in one segment of a branched glycan biosynthesis network. Prior efforts to direct the branched pathway towards selectin-binding oligosaccharides by amplifying enzymes in this branch of the network have had limited success, suggesting that metabolic engineering to simultaneously inhibit the competing pathway may also be required. We report here the partial cloning of the CMP-sialic acid:Galbeta1,3GalNAcalpha2, 3-sialyltransferase (ST3Gal I) gene from Chinese hamster ovary (CHO) cells and the simultaneous inhibition of expression of CHO cell ST3Gal I gene and overexpression of the human UDP-GlcNAc:Galbeta1, 3GalNAc-R beta1,6-N-acetylglucosaminyltransferase (C2GnT) gene. A tetracycline-regulated system adjoined to tricistronic expression technology allowed "one-step" transient manipulation of multiple enzyme activities in the O-glycosylation pathway of a previously established CHO cell line already engineered to express alpha1, 3-fucosyltransferase VI (alpha1,3-Fuc-TVI). Tetracycline-regulated co-expression of a ST3Gal I fragment, cloned in the antisense orientation, and of C2GnT cDNA resulted in inhibition of the ST3Gal I enzymatic activity and increase in C2GnT activity which varied depending on the extent of tetracycline reduction in the cell culture medium. This simultaneous regulated inhibition and activation of the two key enzyme activities in the O-glycosylation pathway of mammalian cells is an important addition to the metabolic engineering field.

Alkaline Phosphatase↗