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PubMed2000

Biomedical engineering: issues and opportunity.

As defined by the National Institutes of Health (NIH), bioengineering is an interdisciplinary field that applies physical, chemical, and mathematical sciences and engineering principles to the study of biology, medicine, behavior, and health. It advances knowledge from the molecular to the organ systems level, and develops new and novel biologics, materials, processes, implants, devices, and informational approaches for the prevention, diagnosis, and treatment of disease for patient rehabilitation and for improving health.

Biomedical Engineering↗
PubMed2000

Ethical considerations for biomedical scientists and engineers: issues for the rank and file.

Biomedical science and engineering is inextricably linked with the fields of medicine and surgery. Yet, while physicians and surgeons, nurses, and other medical professionals receive instruction in ethics during their training and must abide by certain codes of ethics during their practice, those engaged in biomedical science and engineering typically receive no formal training in ethics. In fact, the little contact that many biomedical science and engineering professionals have with ethics occurs either when they participate in government-funded research or submit articles for publication in certain journals. Thus, there is a need for biomedical scientists and engineers as a group to become more aware of ethics. Moreover, recent advances in biomedical technology and the ever-increasing use of new devices virtually guarantee that biomedical science and engineering will become even more important in the future. Although they are rarely in direct contact with patients, biomedical scientists and engineers must become aware of ethics in order to be able to deal with the complex ethical issues that arise from our society's increasing reliance on biomedical technology. In this brief communication, the need for ethical awareness among workers in biomedical science and engineering is discussed in terms of certain conflicts that arise in the workaday world of the biomedical scientist in a complex, modern society. It is also recognized that inasmuch as workers in the many branches of bioengineering are not regulated like their counterparts in medicine and surgery, perhaps academic institutions and professional societies are best equipped to heighten ethical awareness among workers in this important field.

Authorship↗
PubMed2002

Model-based approaches to biomarker discovery and evaluation: a multidisciplinary integrated review.

The most common use of any mathematical or statistical model in physiology, pathophysiology, or therapy evaluation is to organize all relevant components characterizing the system behavior into a rigorously testable framework. This approach is widely applied both to the study of complex homeostatic paradigms involving endogenous substances and to the evaluation of the kinetics and dynamics of xenobiotics such as toxicants and drugs. In either case, one seeks a quantitative framework of the system that is consistent with known physiology and pharmacology and is "compatible" (in some meaningful sense) with all available data. The models are then evaluated and subjected to identifiability and validity tests and can then be used to estimate unknown parameters of interest, to make predictions about system behavior, to simulate previously unobserved behavior in response to a putative perturbation, and to aid in further experimental design. In a broader context, however, the focus and ultimate goal of this set of methodologies (whether this is explicitly stated or not) lies in understanding the mechanisms of physiology and pathophysiology and measuring the effect of therapeutic interventions through the accurate quantification of biomarkers of interest. In this review, we attempt to bring together under this comprehensive framework more than four decades of investigation on modeling and simulation in the life sciences (in particular, we will concentrate on the areas of pharmacology, physiology, and bioengineering). We demonstrate that such modeling approaches, when appropriately designed and evaluated, have significant potential and can be used to understand the multiple factors of disease progression and response to therapeutic interventions, the most likely causes of variability in population and individual responses to therapy, and the most appropriate timing of treatment administration. Lastly, they may allow estimation and prediction of significant outcomes in feasibility and clinical studies.

Animals↗
PubMed2002

Asymmetric cell kinetics genes: the key to expansion of adult stem cells in culture.

A singular challenge in stem cell research today is the expansion and propagation of functional adult stem cells. Unlike embryonic stem cells, which are immortal in culture, adult stem cells are notorious for the difficulty encountered when attempts are made to expand them in culture. One overlooked reason for this difficulty may be the inherent asymmetric cell kinetics of stem cells in postnatal somatic tissues. Senescence is the expected fate of a culture whose growth depends on adult stem cells that divide with asymmetric cell kinetics. Therefore, the bioengineering of strategies to expand adult stem cells in culture requires knowledge of cellular mechanisms that control asymmetric cell kinetics. The properties of several genes recently implicated to function in a cellular pathway(s) that regulates asymmetric cell kinetics are discussed. Understanding the function of these genes in asymmetric cell kinetics mechanisms may be the key that unlocks the adult stem cell expansion problem.

Animals↗
PubMed2005

Efficient lentiviral transduction and improved engraftment of human bone marrow mesenchymal cells.

Human bone marrow (BM) mesenchymal stem/progenitor cells are potentially attractive targets for ex vivo gene therapy. The potential of lentiviral vectors for transducing BM mesenchymal cells was examined using a self-inactivating vector that expressed the green fluorescent protein (GFP) from an internal cytomegalovirus (CMV) promoter. This vector was compared with oncoretroviral vectors expressing GFP from the CMV promoter or a modified long-terminal repeat that had been optimized for long-term expression in stem cells. The percentage of GFP-positive cells was consistently higher following lentiviral versus oncoretroviral transduction, consistent with increased GFP mRNA levels and increased gene transfer efficiency measured by polymerase chain reaction and Southern blot analysis. In vitro GFP and FVIII expression lasted for several months post-transduction, although expression slowly declined. The transduced cells retained their stem/progenitor cell properties since they were still capable of differentiating along adipogenic and osteogenic lineages in vitro while maintaining high GFP and FVIII expression levels. Implantation of lentivirally transduced human BM mesenchymal cells using collagen scaffolds into immunodeficient mice resulted in efficient engraftment of gene-engineered cells and long-term transgene expression in vivo. These biocompatible BM mesenchymal implants represent a reversible, safe, and versatile protein delivery approach because they can be retrieved in the event of an unexpected adverse reaction or when expression of the protein of interest is no longer required. In conclusion, efficient gene delivery with lentiviral vectors in conjunction with the use of bioengineered reversible scaffolds improves the therapeutic prospects of this novel approach for gene therapy, protein delivery, or tissue engineering.

Adipogenesis↗
PubMed2005

Multipotent stem cells in human corneal stroma.

Keratocytes of the corneal stroma secrete a specialized extracellular matrix essential for vision. These quiescent cells exhibit limited capacity for self-renewal and after cell division become fibroblastic, secreting nontransparent tissue. This study sought to identify progenitor cells for human keratocytes. Near the corneal limbus, stromal cells expressed ABCG2, a protein present in many adult stem cells. The ABCG2-expressing cell population was isolated as a side population (SP) by cell sorting after exposure to Hoechst 33342 dye. The SP cells exhibited clonal growth and continued to express ABCG2 and also PAX6, product of a homeobox gene not expressed in adult keratocytes. Cloned SP cells cultured in medium with fibroblast growth factor-2 lost ABCG2 and PAX6 expression and upregulated several molecular markers of keratocytes, including keratocan, aldehyde dehydrogenase 3A1, and keratan sulfate. Cloned corneal SP cells under chondrogenic conditions produced matrix staining with toluidine blue and expressed cartilage-specific markers: collagen II, cartilage oligomatrix protein, and aggrecan. Exposure of cloned SP cells to neurogenic culture medium upregulated mRNA and protein for glial fibrillary acidic protein, neurofilament protein, and beta-tubulin II. These results demonstrate the presence of a population of cells in the human corneal stroma expressing stem cell markers and exhibiting multipotent differentiation potential. These appear to be the first human cells identified with keratocyte progenitor potential. Further analysis of these cells will aid elucidation of molecular mechanisms of corneal development, differentiation, and wound healing. These cells may be a resource for bioengineering of corneal stroma and for cell-based therapeutics.

ATP Binding Cassette Transporter, Subfamily G, Mem↗
PubMed2005

Differentiation of human embryonic stem cells after transplantation in immune-deficient mice.

Our current knowledge of how human tissues grow and develop is limited. We need to increase our understanding of tissue formation if we are to fully realize the potential of stem cells as a source of material for research into health and disease and possible therapeutic applications. Transplanted pluripotent human embryonic stem cells (hESCs) provide a potential system to model and investigate cell differentiation in humans. hESCs transplanted into immune-deficient mice form complex teratomas consisting of a range of differentiated somatic tissues, some of which appear highly organized and resemble structures normally identified in the embryo and adult. Analysis of such tumors may provide a unique opportunity to study organogenesis and lead to novel approaches in bioengineering and the growth of functioning structures composed of a range of alternative cell types. However, little has been done to characterize the developmental potential of hESCs after transplantation. This concise review presents evidence for the ability of hESCs to differentiate in vivo and highlights some of the prominent questions that need to be addressed if transplantation is to be used as a research tool to study hESC differentiation.

Animals↗
PubMed2006

Regrow or repair: potential regenerative therapies for the kidney.

Regenerative medicine is being heralded in a similar way as gene therapy was some 15 yr ago. It is an area of intense excitement and potential, as well as myth and disinformation. However, with the increasing rate of end-stage renal failure and limited alternatives for its treatment, we must begin to investigate seriously potential regenerative approaches for the kidney. This review defines which regenerative options there might be for renal disease, summarizes the progress that has been made to date, and investigates some of the unique obstacles to such treatments that the kidney presents. The options discussed include in situ organ repair via bone marrow recruitment or dedifferentiation; ex vivo stem cell therapies, including both autologous and nonautologous options; and bioengineering approaches for the creation of a replacement organ.

Adult Stem Cells↗
PubMed1992

Automated fabrication of mobility aids (AFMA): below-knee CASD/CAM testing and evaluation program results.

In 1988 the Department of Veterans Affairs Rehabilitation Research and Development Service, under the directorship of Margaret J. Giannini, M.D., began a nationally directed computer-aided design and computer-aided manufacturing (CAD/CAM) research program for the Automated Fabrication of Mobility Aids (AFMA). Under this program CAD/CAM research and development centers were established at the Prosthetics Research Study in Seattle, WA; at Northwestern University and the VA Lakeside Medical Center in Chicago, IL; and at the VA Medical Center and New York University Medical Center in New York, NY. These three centers conducted a collaborative program: (a) to introduce CAD/CAM technologies to prosthetists, physicians, therapists, and rehabilitation health care professionals in the United States; (b) to evaluate the feasibility of using CAD/CAM systems in clinical prosthetics settings; (c) to test and evaluate the University College London-Bioengineering Center's and the University of British Columbia-Medical Engineering Resource Unit's respective systems for the computer-aided design and computer-aided manufacture of prosthetic sockets (CASD/CAM) for below-knee amputees; and, (d) to obtain quantitative data for refinement of the CASD/CAM systems tested, and for the development of new, enhanced, more efficacious, and expedient systems.

Adult↗
PubMed2006

Application of periodontal tissue engineering using enamel matrix derivative and a human fibroblast-derived dermal substitute to stimulate periodontal wound healing in Class III furcation defects.

BACKGROUND: Enamel matrix derivative (EMD) has been shown to promote several aspects of periodontal regeneration in vitro and in vivo. Recently, a bioengineered tissue (DG) was developed to promote wound healing of chronic skin ulcers. This pilot study sought to assess the effects of EMD and DG, alone or in combination, on periodontal wound healing in surgically created Class III furcation defects. METHODS: Six female baboons received bilateral ostectomy of approximately 10 mm around the first and second mandibular molars to achieve Class III, subclass C furcation defects. Wire ligatures and cotton pellets were left in place for 2 months to maintain the depth of the defects and promote plaque accumulation. Each furcally involved molar was then assigned to one of four treatments: open flap debridement (OFD), OFD plus EMD, OFD plus DG, or OFD plus DG and EMD. This resulted in six total sites per treatment group. Seven months after defect creation and 5 months after treatment, and after no oral hygiene, tissue blocks of the mandible were taken for blinded histometric analysis to assess parameters of periodontal regeneration adjacent to furcal root surfaces and from the mid-furcal aspect (i.e., new bone, new connective tissue attachment, new epithelial attachment, and new cementum formation). RESULTS: Histometric analysis demonstrated differential regenerative responses with respect to treatment within each animal. However, statistically significant differences between treatments from all six animals were not observed (P >0.20, mixed-model analysis of variance). EMD-treated sites presented mildly positive regenerative results and no negative responses. Both DG only and combination therapy demonstrated similar or less than positive responses relative to OFD controls. CONCLUSION: The descriptive analysis may suggest a positive effect of enamel matrix proteins and a negative effect of DG used alone or in combination with enamel matrix proteins on the regeneration of Class III furcation defects in baboons.

Animals↗
PubMed1997

Future directions in the development of new antitubercular drugs. Where do we go from here?

The global resurgence of tuberculosis and rampant drug resistance have rekindled the need for and interest in the development of new antitubercular drugs. Delineation of the possible drug targets furnished by the various mycobacterial cell components might result in rational approaches to the development of such agents. In the future, molecular genetics might help both in the bioengineering and rapid screening of the activity of new compound. Collaboration is anticipated between the pharmaceutical industry and academic institutions in these areas.

Antitubercular Agents↗
PubMed2002

Pharmacokinetics and pharmacodynamics of tenecteplase in fibrinolytic therapy of acute myocardial infarction.

Tenecteplase is a novel fibrinolytic protein bioengineered from human tissue plasminogen activator (alteplase) for the therapy of acute ST-segment elevation myocardial infarction. Specific mutations at three sites in the alteplase molecule result in 15-fold higher fibrin specificity, 80-fold reduced binding affinity to the physiological plasminogen activator inhibitor PAI-1 and 6-fold prolonged plasma half-life (22 vs 3.5 minutes). Consequently, tenecteplase can be administered as a single intravenous bolus of 30-50mg (0.53 mg/kg bodyweight) over 5-10 seconds, in contrast to the 90-minute accelerated infusion regimen of alteplase. Tenecteplase plasma concentration-time profiles have been obtained from a total of 179 patients with acute myocardial infarction. Tenecteplase exhibited biphasic disposition; the initial disposition phase was predominant with a mean half-life of 17-24 minutes, and the mean terminal half-life was 65-132 min. Over the clinically relevant dose range of 30-50mg, mean clearance (CL) was 105 ml/min. The mean initial volume of distribution V(1) was 4.2-6.3L, approximating plasma volume, and volume of distribution at steady state was 6.1-9.9L, suggesting limited extravascular distribution or binding. Bodyweight and age were found to influence significantly both CL and V(1). Total bodyweight explained 19% of the variability in CL and 11% of the variability in V(1), and a 10kg increase in total bodyweight resulted in a 9.6 ml/min increase in CL. This relationship aided the development of a rationale for the weight-adjusted dose regimen for tenecteplase. Age explained only a further 11% of the variability in CL. The percentage of patients who achieved normal coronary blood flow was clearly related to AUC. More than 75% of patients achieved normal flow at 90 minutes after administration when their partial AUC(2-90) exceeded 320 microg.min/ml, corresponding to an average plasma concentration of 3.6 microg/ml. Systemic exposure to tenecteplase at all times after bolus administration of 30-50mg was higher than for alteplase 100mg. Tenecteplase has demonstrated equivalent efficacy and improved safety compared with the current gold standard alteplase in a large mortality trial (ASSENT-2). This suggests that the reduced clearance, greater fibrin specificity and higher PAI-1 resistance of tenecteplase allow higher plasma concentrations and thus a more rapid restoration of coronary patency to be attained, while providing a reduction in major non-cerebral bleeding events.

Acute Disease↗
PubMed2002

Clinical management of pyoderma gangrenosum.

Pyoderma gangrenosum is a noninfectious neutrophilic dermatosis that usually starts with sterile pustules which rapidly progress to painful ulcers of variable depth and size with undermined violaceous borders. In 17 to 74% of cases, pyoderma gangrenosum is associated with an underlying disease, most commonly inflammatory bowel disease, rheumatological or hematological disease or malignancy. Diagnosis of pyoderma gangrenosum is based on a history of an underlying disease, typical clinical presentation and histopathology, and exclusion of other diseases that would lead to a similar appearance. Randomized, double-blinded prospective multicenter trials investigating the treatment of pyoderma gangrenosum are not available. The treatments with the best clinical evidence are systemic corticosteroids (in the initial phase usually 100 to 200 mg/day) and cyclosporine (mainly as a maintenance treatment). Combinations of corticosteroids with cytotoxic drugs such as azathioprine, cyclophosphamide or chlorambucil are used in patients with disease that is resistant to corticosteroids. The combination of corticosteroids with sulfa drugs, such as dapsone, or clofazimine, minocycline and thalidomide, has been used as a corticosteroid-sparing alternative. Limited experience has been documented with methotrexate, colchicine, nicotine, and mycophenolate mofetil, among other drugs. Alternative treatments include local application of granulocyte-macrophage colony-stimulating factor, intravenous immunoglobulins and plasmapheresis. Skin transplants (split-skin grafts or autologous keratinocyte grafts) and the application of bioengineered skin is useful in selected cases in conjunction with immunosuppression. Topical therapy with modern wound dressings is useful to minimize pain and the high risk of secondary infection. The application of topical antibacterials cannot be recommended because of their potential to sensitize and their questionable efficacy, but systemic antibacterial therapy is mandatory when infection is present. Despite recent advances in therapy, the prognosis of pyoderma gangrenosum remains unpredictable.

Adrenal Cortex Hormones↗
PubMed2001

New strategies to prevent restenosis.

The Holy Grail of cardiovascular pharmacology has been the search for an effective therapy targeting restenosis after angioplasty and/or intra-arterial stenting. The failure of promising therapeutics in clinical trials underscores the complexity and redundancy of the signaling cascades regulating mitogenesis and fibrogenesis. Novel therapeutic modalities have potential to target dysfunctional signaling elements directly in vascular smooth muscle cells. Significant progress in the treatment against restenosis will require the exploitation and cross-fertilization of developments in the fields of pharmacology, bioengineering, genetics, and molecular biology. Collaboration among researchers in these fields will be essential.

Angioplasty↗
PubMed2006

Soft condensed matter in pharmaceutical design.

In recent years pharmaceutical design has been facing the needs expressed by new therapeutic methodologies such as gene therapy, targeted delivery and closely related diagnostic fields as contrast enhancing agents for ultrasonic investigations. In this context pharmaceutical research has diversified the efforts toward a more integrated approach where the efficacy of an active molecule is enhanced and assisted by the surrounding carrier. Usually this drug platform is a hydrogel matrix, a multicomponent system constituted by an aqueous solution and a polymeric moiety imparting different functions to the matrix, as responsiveness to external stimuli, affinity to receptors, controlled drug release. Such devices represent one of the leading topics of the soft condensed matter recent research, a domain where physics, chemistry and bioengineering cross each other with the aim to achieve an integrated description of these materials. In this respect modern drug design will make use more and more of concepts proper of soft condensed polymer and colloidal sciences. In this review we will describe the state-of-art in the field of the matrices used in innovative drug formulations with a particular emphasis on the implications to pharmaceutical design along with the experimental and theoretical investigation tools worked out in the last decade.

Chemistry, Pharmaceutical↗
PubMed2025

The Application of Preventive Medicine in the Future Digital Health Era.

A number of seismic shifts are expected to reshape the future of medicine. The global population is rapidly aging, significantly impacting the global disease burden. Medicine is undergoing a paradigm shift, defining and diagnosing diseases at earlier stages and shifting the health care focus from treating diseases to preventing them. The application and purview of digital medicine are expected to broaden significantly. Furthermore, the COVID-19 pandemic has further accelerated the shift toward predictive, preventive, personalized, and participatory (P4) medicine, and has identified health care accessibility, affordability, and patient empowerment as core values in the future digital health era. This "left shift" toward preventive care is anticipated to redefine health care, emphasizing health promotion over disease treatment. In the future, the traditional triad of preventive medicine-primary, secondary, and tertiary prevention-will be realized with technologies such as genomics, artificial intelligence, bioengineering and wearable devices, and telemedicine. Breast cancer and diabetes serve as case studies to demonstrate how these technologies such as personalized risk assessment, artificial intelligence-assisted and app-based technologies, have been developed and commercialized to provide personalized preventive care, identifying those at a higher risk and providing instructions and interventions for healthier lifestyles and improved quality of life. Overall, preventive medicine and the use of advanced technology will hold great potential for improving health care outcomes in the future.

Humans↗
PubMed1976

Radiology of knee joint replacement.

As total knee replacement becomes more successful due to advances in surgery and bioengineering, a greater number of patients will be offered this procedure as a viable alternative to arthrodesis. Radiologic consultation will be sought for evaluation of proper alignment as well as postoperative complications such as loosening, instability, dislocation, limitation of range of motion, fracture, and infection. This evaluation may be accomplished by plain films and arthrography. Radiographic aspects of these features are discussed and illustrated.

Biomechanical Phenomena↗
PubMed2004

Tissue-engineered human asthmatic bronchial equivalents.

The isolation of human bronchial epithelial (HBEC) and fibroblastic cells (HBFC) from biopsies of asthmatic and non-asthmatic volunteers provided unique cellular materials to be used for the production of bioengineered bronchial equivalents (BE) in vitro. The HBEC are grown on a mesenchymal layer seeded with HBFC and the BE can be maintained for at least 15 days in culture. Under the BE culture conditions established previously, HBEC undergo differentiation into ciliated and goblet cells, within a pseudostratified organization comparable to human bronchi. We published previously the results from histologic and functional analyses of such BE produced exclusively using non-asthmatic HBEC and HBFC. We report here the comparative analyses of BE produced with non-asthmatic and asthmatic living HBEC and HBFC (naBE and aBE, respectively). Our data indicated that all asthmatic HBEC populations grown on a mesenchymal layer, containing non-asthmatic HBFC, slowly reached a confluent state but then detached from the matrix upon culture time. These BE appear to be very good models to study the mechanisms involved in asthma in vitro.

Adult↗