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PubMed1997

Exposure to mineral oil mist and respiratory symptoms in marine engineers.

The purpose of the study was to see if marine engineers have an increased prevalence of respiratory symptoms, and if so whether it can be related to occupational exposures. A self-administered questionnaire was sent to 700 male seamen from three Norwegian ferry companies. Of the 492 respondents, 169 were currently working as marine engineers and 295 had never worked as marine engineers. The outcomes of cough and wheezing, chronic bronchitis, severe dyspnea, any dyspnea, and mucous membrane irritation (MMI) were defined from the questionnaire. Age and smoking-adjusted prevalences of these respiratory conditions were compared between the groups. Logistic regression was used to further elucidate the explanatory variables. The exposure assessment indicated an exposure (TWAC) to oil mist for marine engineers in the range from 0.12 to 0.74 mg/m3 (mean 0.45 mg/m3) When comparing current marine engineers with those who had never worked as marine engineers, the prevalence ratios were 1.38 (95% CI 1.0-1.9) for MMI, 1.53 (95% CI 1.2-1.9) for any dyspnea, and 1.63 (95% CI 1.0-2.6) for severe dyspnea. The differences remained for some of the symptoms after controlling for self-reported former asbestos exposure in the regression analysis. The increased prevalence of respiratory symptoms found among marine engineers in this investigation may partly be explained be oil-mist exposure, or more probably by a combination of past asbestos exposure and past and present oil-mist exposure.

Cross-Sectional Studies↗
PubMed2001

Tissue engineering in plastic reconstructive surgery.

Tissue engineering (TE) is a new interdisciplinary field of applied research combining engineering and biosciences together with clinical application, mainly in surgical specialities, to develop living substitutes for tissues and organs. Tissue engineering approaches can be categorized into substitutive approaches, where the aim is the ex vivo construction of a living tissue or organ similar to a transplant, vs. histioconductive or histioinductive concepts in vivo. The main successful approaches in developing tissue substitutes to date have been progresses in the understanding of cell-cell interactions, the selection of appropriate matrices (cell-matrix interaction) and chemical signalling (cytokines, growth factors) for stimulation of cell proliferation and migration within a tissue-engineered construct. So far virtually all mammalian cells can be cultured under specific culture conditions and in tissue specific matrices. Future progress in cell biology may permit the use of pluripotent stem cells for TE. The blueprint for tissue differentiation is the genome: for this it is reasonable to combine tissue engineering with gene therapy. The key to the progress of tissue engineering is an understanding between basic scientists, biochemical engineers, clinicians, and industry.

Animals↗
PubMed2002

Engineering of molecular and cellular biocatalysts: selected contributions by James E. Bailey.

James (Jay) E. Bailey was a pioneer in biotechnology and biochemical engineering. During his 30 years in academia he made seminal contributions to many fields of chemical engineering science, including catalysis and reaction engineering, bioprocess engineering, mathematical modeling of cellular processes, recombinant DNA technology, enzyme engineering, and metabolic engineering. This article celebrates some of his contributions to the engineering of molecular and cellular biocatalysts, and identifies the influence he had on current and future research in biotechnology.

Biochemistry↗
PubMed1999

Successful design and development of genetically engineered Saccharomyces yeasts for effective cofermentation of glucose and xylose from cellulosic biomass to fuel ethanol.

Ethanol is an effective, environmentally friendly, nonfossil, transportation biofuel that produces far less pollution than gasoline. Furthermore, ethanol can be produced from plentiful, domestically available, renewable, cellulosic biomass. However, cellulosic biomass contains two major sugars, glucose and xylose, and a major obstacle in this process is that Saccharomyces yeasts, traditionally used and still the only microorganisms currently used for large scale industrial production of ethanol from glucose, are unable to ferment xylose to ethanol. This makes the use of these safest, most effective Saccharomyces yeasts for conversion of biomass to ethanol economically unfeasible. Since 1980, scientists worldwide have actively been trying to develop genetically engineered Saccharomyces yeasts to ferment xylose. In 1993, we achieved a historic breakthrough to succeed in the development of the first genetically engineered Saccharomyces yeasts that can effectively ferment both glucose and xylose to ethanol. This was accomplished by carefully redesigning the yeast metabolic pathway for fermenting xylose to ethanol, including cloning three xylose-metabolizing genes, modifying the genetic systems controlling gene expression, changing the dynamics of the carbon flow, etc. As a result, our recombinant yeasts not only can effectively ferment both glucose and xylose to ethanol when these sugars are present separately in the medium, but also can effectively coferment both glucose and xylose present in the same medium simultaneously to ethanol. This has made it possible because we have genetically engineered the Saccharomyces yeasts as such that they are able to overcome some of the natural barrier present in all microorganisms, such as the synthesis of the xylose metabolizing enzymes not to be affected by the presence of glucose and by the absence of xylose in the medium. This first generation of genetically engineered glucose-xylose-cofermenting Saccharomyces yeasts relies on the presence of a high-copy-number 2 mu-based plasmid that contains the three cloned genetically modified xylose-metabolizing genes to provide the xylose-metabolizing capability. In 1995, we achieved another breakthrough by creating the super-stable genetically engineered glucose-xylose-cofermenting Saccharomyces yeasts which contain multiple copies of the same three xylose-metabolizing genes stably integrated on the yeast chromosome. This is another critical development which has made it possible for the genetically engineered yeasts to be effective for cofermenting glucose and xylose by continuous fermentation. It is widely believed that the successful development of the stable glucose-xylose-cofermenting Saccharomyces yeasts has made the biomass-to-ethanol technology a step much closer to commercialization. In this paper, we present an overview of our rationales and strategies as well as our methods and approaches that led to the ingenious design and successful development of our genetically engineered Saccharomyces yeasts for effective cofermentation of glucose and xylose to biofuel ethanol.

Biomass↗
PubMed2004

Creating artificial perichondrium by polymer complex membrane macroencapsulation: immune protection and stabilization of subcutaneously transplanted tissue-engineered cartilage.

Functional organ or tissue failure is one of the most frequent, devastating and costly problems in modern health care. The field of tissue engineering has tremendous potential for developing new functional tissue. In reconstructive surgery, cartilage engineering could be a serious alternative to the established method of autologous cartilage transplantation. Recent studies demonstrate cartilage engineering by subcutaneous implantation of chondrocyte-seeded PGA/PLA-fibrin glue scaffolds in the backs of nude mice. In both autologous cartilage transplantation and cartilage engineering, the host immune response affects transplant integrity and cartilage morphology to an unforeseeable extent. To investigate whether polyelectrolyte complex (PEC) membranes can prevent rejection of cartilage transplants without neglecting tissue metabolism, tissue-engineered cartilage encapsulated with a PEC membrane was subcutaneously implanted in the backs of nude mice. Non-encapsulated tissue-engineered cartilage was used for the control group. Histochemistry and scanning electron microscopy were performed 4 and 12 weeks after implantation. There was no interaction between the host and the implant with an intact PEC membrane. With protection by PEC encapsulation, implanted tissue-engineered cartilage showed no signs of degeneration and had a significantly weaker cellular immune response than without it. Thus, PEC membrane encapsulation appears to be a novel approach for protecting cartilage implants from host immune response after autologous transplantation.

Animals↗
PubMed2004

Cartilage and bone tissue engineering for reconstructive head and neck surgery.

The loss of cartilage and bone because of congential defects, trauma and after tumor resection is a major clinical problem in head and neck surgery. The most prevalent methods of tissue repair are through autologous grafting or using implants. Tissue engineering applies the principles of engineering and life sciences in order to create bioartificial cartilage and bone. Most strategies for cartilage tissue engineering are based on resorbable biomaterials as temporary scaffolds for chondrocytes or precursor cells. Clinical application of tissue-engineered cartilage for reconstructive head and neck surgery as opposed to orthopedic applications has not been well established. While in orthopedic and trauma surgery engineered constructs or autologous chondrocytes are placed in the immunoprivileged region of joints, the subcutaneous transplant site in the head and neck can lead to strong inflammatory reactions and resorption of the bioartificial cartilage. Encapsulation of the engineered cartilage and modulation of the local immune response are potential strategies to overcome these limitations. In bone tissue engineering the combination of osteoconductive matrices, osteoinductive proteins such as bone morphogenetic proteins and osteogenic progenitor cells from the bone marrow or osteoblasts from bone biopsies offer a variety of tools for bone reconstruction in the craniofacial area. The utility of each technique is site dependent. Osteoconductive approaches are limited in that they merely create a favorable environment for bone formation, but do not play an active role in the recruitment of cells to the defect. Delivery of inductive signals from a scaffold can incite cells to migrate into a defect and control the progression of bone formation. Rapid osteoid matrix production in the defect site is best accomplished by using osteoblasts or progenitor cells.

Bone and Bones↗
PubMed2006

Heart valve tissue engineering: concepts, approaches, progress, and challenges.

Potential applications of tissue engineering in regenerative medicine range from structural tissues to organs with complex function. This review focuses on the engineering of heart valve tissue, a goal which involves a unique combination of biological, engineering, and technological hurdles. We emphasize basic concepts, approaches and methods, progress made, and remaining challenges. To provide a framework for understanding the enabling scientific principles, we first examine the elements and features of normal heart valve functional structure, biomechanics, development, maturation, remodeling, and response to injury. Following a discussion of the fundamental principles of tissue engineering applicable to heart valves, we examine three approaches to achieving the goal of an engineered tissue heart valve: (1) cell seeding of biodegradable synthetic scaffolds, (2) cell seeding of processed tissue scaffolds, and (3) in-vivo repopulation by circulating endogenous cells of implanted substrates without prior in-vitro cell seeding. Lastly, we analyze challenges to the field and suggest future directions for both preclinical and translational (clinical) studies that will be needed to address key regulatory issues for safety and efficacy of the application of tissue engineering and regenerative approaches to heart valves. Although modest progress has been made toward the goal of a clinically useful tissue engineered heart valve, further success and ultimate human benefit will be dependent upon advances in biodegradable polymers and other scaffolds, cellular manipulation, strategies for rebuilding the extracellular matrix, and techniques to characterize and potentially non-invasively assess the speed and quality of tissue healing and remodeling.

Animals↗
PubMed2003

What's philosophically interesting about engineering ethics?

What makes a subject philosophically interesting is hard-to-resolve confusion about fundamental concepts. Engineering ethics suffers from at least three such fundamental confusions. First, there is confusion about what the "ethics" in engineering ethics is (ordinary morality, philosophical ethics, special standards, or something else?) Second, there is confusion about what the profession of engineering is (a function, discipline, occupation, kind of organization, or something else?) Third, there is confusion about what the discipline of engineering is. These fundamental confusions in engineering ethics connect with philosophically interesting work in moral theory, political philosophy, and philosophy of science. Work in these areas may help with the philosophical problems of engineering ethics. But, equally important, work in engineering ethics may help with the philosophical problems in these others fields.

Engineering↗
PubMed2003

"Things that went well--no serious injuries or deaths": ethical reasoning in a normal engineering design process.

We argue that considering only a few 'big' ethical decisions in any engineering design process--both in education and practice--only reinforces the mistaken idea of engineering design as a series of independent sub-problems. Using data collected in engineering design organisations over a seven year period, we show how an ethical component to engineering decisions is much more pervasive. We distinguish three types of ethical justification for engineering decisions: (1) consequential, (2) deontological or non-consequential, and (3) virtue-based. We find that although there is some evidence for engineering designers as 'classic' consequentialists, a more egocentric consequentialism would appear more fitting. We also explain how the idea of a 'folk ethics'--a justification in the second category that consciously weighs one thing with another--fits with the idea of the engineering design process as social negotiation rather than as technological progress.

Architecture↗
PubMed2004

Ethics education in the consulting engineering environment: where do we start?

As a result of in-house discussions stimulated by previous Gonzaga engineering ethics conferences, Coffman Engineers began the implementation of what is to be a company-wide ethics training program. While preparing a curriculum aimed at consulting engineers, we found very little guidance as to how to proceed with most available literature being oriented towards the academic environment. We consulted a number of resources that address the teaching of engineering ethics in higher education, but questioned their applicability for the Consulting Engineering environment. This lack of guidance led us to informal research into the ethical knowledge and attitudes of both consulting engineers and engineering students. Some of our findings were unexpected, and suggest that a simpler approach to teaching ethics to working professionals might be preferred to that typically promoted in higher education.

Consultants↗
PubMed2005

Mechano-active tissue engineering of vascular smooth muscle using pulsatile perfusion bioreactors and elastic PLCL scaffolds.

Blood vessels are subjected in vivo to mechanical forces in a form of radial distention, encompassing cyclic mechanical strain due to the pulsatile nature of blood flow. Vascular smooth muscle (VSM) tissues engineered in vitro with a conventional tissue engineering technique may not be functional, because vascular smooth muscle cells (VSMCs) cultured in vitro typically revert from a contractile phenotype to a synthetic phenotype. In this study, we hypothesized that pulsatile strain and shear stress stimulate VSM tissue development and induce VSMCs to retain the differentiated phenotype in VSM engineering in vitro. To test the hypothesis, rabbit aortic smooth muscle cells (SMCs) were seeded onto rubber-like elastic, three-dimensional PLCL [poly(lactide-co-caprolactone), 50:50] scaffolds and subjected to pulsatile strain and shear stress by culturing them in pulsatile perfusion bioreactors for up to 8 weeks. As control experiments, VSMCs were cultured on PLCL scaffolds statically. The pulsatile strain and shear stress enhanced the VSMCs proliferation and collagen production. In addition, a significant cell alignment in a direction radial to the distending direction was observed in VSM tissues exposed to radial distention, which is similar to that of native VSM tissues in vivo, whereas VSMs in VSM tissues engineered in the static condition randomly aligned. Importantly, the expression of SM alpha-actin, a differentiated phenotype of SMCs, was upregulated by 2.5-fold in VSM tissues engineered under the mechano-active condition, compared to VSM tissues engineered in the static condition. This study demonstrates that tissue engineering of VSM tissues in vitro by using pulsatile perfusion bioreactors and elastic PLCL scaffolds leads to the enhancement of tissue development and the retention of differentiated cell phenotype.

Animals↗
PubMed2005

Cell sheet engineering: recreating tissues without biodegradable scaffolds.

While tissue engineering has long been thought to possess enormous potential, conventional applications using biodegradable scaffolds have limited the field's progress, demonstrating a need for new methods. We have previously developed cell sheet engineering using temperature-responsive culture dishes in order to avoid traditional tissue engineering approaches, and their related shortcomings. Using temperature-responsive dishes, cultured cells can be harvested as intact sheets by simple temperature changes, thereby avoiding the use of proteolytic enzymes. Cell sheet engineering therefore allows for tissue regeneration by either direct transplantation of cell sheets to host tissues or the creation of three-dimensional structures via the layering of individual cell sheets. By avoiding the use of any additional materials such as carrier substrates or scaffolds, the complications associated with traditional tissue engineering approaches such as host inflammatory responses to implanted polymer materials, can be avoided. Cell sheet engineering thus presents several significant advantages and can overcome many of the problems that have previously restricted tissue engineering with biodegradable scaffolds.

Animals↗
PubMed2006

Stem cells and adipose tissue engineering.

A large proportion of the plastic and reconstructive surgical procedures performed each year are to repair soft tissue defects that result from traumatic injury, tumor resection, and congenital defects. These defects typically result from the loss of a large volume of adipose tissue. To date, no ideal filler material which is successful in all cases has been developed. Additionally, the success of using autologous fat tissue grafts to repair soft tissue defects has been limited. Researchers are thus investigating strategies to engineer volumes of adipose tissue that may be used in these cases. A necessary component for engineering a viable tissue construct is an appropriate cell source. Attempts to engineer adipose tissue have involved the use of preadipocytes and adipocytes as the base cell source. Increased interest surrounding the research and development of stem cells as a source of cells for tissue engineering has, however, led to a new path of investigation for developing adipose tissue-engineering strategies. This manuscript serves as a review of the current state of adipose tissue-engineering methods and describes the shift toward tissue-engineering strategies using stem cells.

Adipocytes↗
PubMed2002

Human umbilical cord cells: a new cell source for cardiovascular tissue engineering.

BACKGROUND: Tissue engineering of viable, autologous cardiovascular constructs with the potential to grow, repair, and remodel represents a promising new concept for cardiac surgery, especially for pediatric patients. Currently, vascular myofibroblast cells (VC) represent an established cell source for cardiovascular tissue engineering. Cell isolation requires the invasive harvesting of venous or arterial vessel segments before scaffold seeding, a technique that may not be preferable, particularly in pediatric patients. In this study, we investigated the feasibility of using umbilical cord cells (UCC) as an alternative autologous cell source for cardiovascular tissue engineering. METHODS: Human UCC were isolated from umbilical cord segments and expanded in culture. The cells were sequentially seeded on bioabsorbable copolymer patches (n = 5) and grown in vitro in laminar flow for 14 days. The UCC were characterized by flow cytometry (FACS), histology, immunohistochemistry, and proliferation assays and were compared to saphenous vein-derived VC. Morphologic analysis of the UCC-seeded copolymer patches included histology and both transmission and scanning electron microscopy. Characterization of the extracellular matrix was performed by immunohistochemistry and quantitative extracellular matrix protein assays. The tissue-engineered UCC patches were biomechanically evaluated using uniaxial stress testing and were compared to native tissue. RESULTS: We found that isolated UCC show a fibroblast-like morphology and superior cell growth compared to VC. Phenotype analysis revealed positive signals for alpha-smooth muscle actin (ASMA), desmin, and vimentin. Histology and immunohistochemistry of seeded polymers showed layered tissue formation containing collagen I, III, and glycoaminoglycans. Transmission electron microscopy showed viable myofibroblasts and the deposition of collagen fibrils. A confluent tissue surface was observed during scanning electron microscopy. Glycoaminoglycan content did not reach values of native tissue, whereas cell content was increased. The biomechanical properties of the tissue-engineered constructs approached native tissue values. CONCLUSIONS: Tissue engineering of cardiovascular constructs using UCC is feasible in an in vitro environment. The UCC demonstrated excellent growth properties and tissue formation with mechanical properties approaching native tissue. It appears that UCC represent a promising alternative autologous cell source for cardiovascular tissue engineering, offering the additional benefits of using juvenile cells and avoiding the invasive harvesting of intact vascular structures.

Actins↗
PubMed2003

Tissue-engineered esophagus: experimental substitution by onlay patch or interposition.

OBJECTIVES: We proposed to fabricate a tissue-engineered esophagus and to use it for replacement of the abdominal esophagus. METHODS: Esophagus organoid units, mesenchymal cores surrounded by epithelial cells, were isolated from neonatal or adult rats and paratopically transplanted on biodegradable polymer tubes, which were implanted in syngeneic hosts. Four weeks later, the tissue-engineered esophagus was either harvested or anastomosed as an onlay patch or total interposition graft. Green Fluorescent Protein labeling by means of viral infection of the organoid units was performed before implantation. Histology and immunohistochemical detection of the antigen alpha-actin smooth muscle were performed. RESULTS: Tissue-engineered esophagus grows in sufficient quantity for interposition grafting. Histology reveals a complete esophageal wall, including mucosa, submucosa, and muscularis propria, which was confirmed by means of immunohistochemical staining for alpha-actin smooth muscle. Tissue-engineered esophagus architecture was maintained after interposition or use as a patch, and animals gained weight on a normal diet. Green Fluorescent Protein-labeled tissue-engineered esophagus preserved its fluorescent label, proving the donor origin of the tissue-engineered esophagus. CONCLUSIONS: Tissue-engineered esophagus resembles the native esophagus and maintains normal histology in anastomosis, with implications for therapy of long-segment esophageal tissue loss caused by congenital absence, surgical excision, or trauma.

Actins↗
PubMed2003

Engineering of muscle tissue.

The loss or failure of an organ or tissue is one of the most frequent, devastating, and costly problems in health care. Tissue engineering and regenerative medicine is an emerging interdisciplinary field that applies the principles of biology and engineering to the development of viable substitutes that restore, maintain, or improve the function of human tissues and organs. Tissue engineering science has provided critical new knowledge that will deepen our understanding of the phenotype of an important category of cell types-the muscle cells-and this knowledge may enable meaningful advances in musculoskeletal tissue engineering. There are two principle strategies for the replacement of impaired muscle tissues. One approach uses the application of isolated and differentiated cells (in vivo tissue engineering), using a transport matrix for the cell delivery; the other uses in vitro-designed and pre-fabricated tissue equivalents (in vitro tissue engineering). Future developments and the decision regarding which approach is more promising depend on the elucidation of the relationships among cell growth and differentiation, the three-dimensional environment, the architecture of the cells, and gene expression of the developmental process and the survival of the cells and integration in the host in in vivo experiments. As the techniques of tissue engineering become more sophisticated and as issues such as vascularization and innervation are addressed, the usefulness of these methods for reconstructive surgery may grow significantly.

Humans↗
PubMed2004

Role of gene therapy in tissue engineering procedures in rheumatology: the use of animal models.

Tissue engineering is not only the application of cells and scaffolds to generate a new tissue but should also bring into play biological principles to guide cellular behavior. A way to modify cellular behavior is genetic modification of the cells used for tissue engineering (gene therapy). In the field of rheumatic diseases, cellular modification by overexpressing anabolic factors, such as insulin-like growth factor-I or transforming growth factor beta, or inhibitors of catabolic cytokines or proteolytic enzymes can protect tissues form further destruction and stimulate tissue repair. To test the effect of transgenes on tissue engineering adequate test systems have to be available. Initial testing can be done in simple in vitro systems. However, animal models are unavoidable to study the interaction between the environment and tissue engineering. Optimal models to study gene therapy in combination with tissue engineering in the field of rheumatology are not available at this moment. Arthritis models are mainly developed in small animals while high-quality tissue engineering experiments ask for a large animal model. Development of animal models that can be used for tissue engineering experiments and mimic end stage arthritic diseases is needed.

Animals↗
PubMed2004

Biomechanical considerations of animal models used in tissue engineering of bone.

Tissue engineering combines the aspects of cell biology, engineering, material science, and surgery to generate new functional tissue, and provides an important approach to the repair of segmental defects and in restoring biomechanical function. The development of tissue-engineering strategies into clinical therapeutic protocols requires extensive, preclinical experimentation in appropriate animal models. The ultimate success of any treatment strategy must be established in these animal models before clinical application. It is clear that the demands of the biological and mechanical environment in the clinical repair of critical size defects with tissue-engineered materials is significantly different from those existing in experimental animals. The major considerations facing any tissue-engineering testing logic include the choice of the defect, the animal, the age of the animal, the anatomic site, the size of the lesion, and most importantly, the micro-mechanical environment. With respect to biomechanical considerations when selecting animals for tissue- engineering of bone, it is evident that no common criteria have been reported. While in smaller animals due to size constraint only structural properties of whole bones can be measured, in larger animals and humans both material properties and structural properties are of interest. Based on reported results, comparison between the tissue-engineered bone across species may be of importance in establishing better model selection criteria. It has already been found that the deformation of long bones is fairly constant across species, and that stress levels during gait are dependent on the weight of the animal and the material properties of the bone tissue. Future research should therefore be geared towards developing better biomechanical testing systems and then finding the right animal model for the existing equipment.

Animals↗