Institute for Medicine and Engineering

The mission of the Institute for Medicine and Engineering (IME) is to stimulate fundamental research at the interface between biomedicine and engineering/physical/computational sciences leading to innovative applications in biomedical research and clinical practice. The IME was created in 1996 by the Schools of Medicine (SOM) and Engineering and Applied Science (SEAS) to pursue opportunities for collaborative research. The IME has been successful in obtaining over $80 million in extramural grants, and funded programs. These include a research center in Cell Studies of Pulmonary Artery Hypertension, and a Penn Center for Molecular Discovery.

Membership: The Institute houses 11 core faculty, 6 from the School of Medicine and 5 from SEAS, who were recruited to form the basis for the IME; however, the Institute extends beyond the core group to include 106 members from various schools including School of Medicine, SEAS and Arts and Sciences faculty. The Institute interacts with 24 other Centers or departments.

Multi-disciplinary Research: The IME mission to foster research at the interface of medicine and engineering is met (i) through 8 central investigators who span these disciplines in both schools, (ii) through the core facilities, pilot grant programs, research training, and educational events involving its very wide membership (of 106). The research conducted by central investigators is quite broad, ranging from cell and molecular biology to tissue engineering, biophysics and nanobiology/medicine. Having established a strong basic research foundation the Institute is now expanding translational programs in medicine and engineering.

Strategic Importance: The IME relates directly to 3 major themes of the SOM Research Strategic Plan: Cancer, Neurosciences and Cardiovascular Biology. The University Strategic Plan identifies the link between engineering and medicine as one of the key drivers of success and recommends "fostering advances in engineering, computing, chemistry, mathematics and behavioral sciences that can be applied to life sciences." Because of the multi-disciplinary nature of the Institute, it is well positioned to take advantage of the new NIH roadmap. Because of its unique interface with SEAS, the IME is a strong force in faculty retention by providing unique directions and connections for research among faculty.

 

 

 

 

School of Engineering and Applied Science

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  • Publication
    Impaired Notch Signaling Promotes De novo Squamous Cell Carcinoma Formation
    (2006-08-01) Lepore, John J.; Cheng, Lan; Seykora, John J; Proweller, Aaron; Millar, Sarah E; Tu, Lili; Pear, Warren S; Parmacek, Michael S; Lu, Min Min
    Signaling through Notch receptors in the skin has been implicated in the differentiation, proliferation, and survival of keratinocytes, as well as in the pathogenesis of basal cell carcinoma (BCC). To determine the composite function of Notch receptor–mediated signaling in the skin and overcome potential redundancies between receptors, conditional transgenic mice were generated that express the pan-Notch inhibitor, dominant-negative Mastermind Like 1 (DNMAML1), to repress all canonical [CBF-1/Suppressor of hairless/LAG-1 (CSL)–dependent] Notch signaling exclusively in the epidermis. Here, we report that DNMAML1 mice display hyperplastic epidermis and spontaneously develop cutaneous squamous cell carcinoma (SCC) as well as dysplastic precursor lesions, actinic keratoses. Mice expressing epidermal DNMAML1 display enhanced accumulation of nuclear ß-catenin and cyclin D1 in suprabasilar keratinocytes and in lesional cells from SCCs, which was also observed in human cutaneous SCC. These results suggest a model wherein CSL-dependent Notch signaling confers protection against cutaneous SCC. The demonstration that inhibition of canonical Notch signaling in mice leads to spontaneous formation of SCC and recapitulates the disease in humans yields fundamental insights into the pathogenesis of SCC and provides a unique in vivo animal model to examine the pathobiology of cutaneous SCC and for evaluating novel therapies.
  • Publication
    Kinetics of random aggregation-fragmentation processes with multiple components
    (2003-05-09) Laurenzi, Ian J; Diamond, Scott L
    A computationally efficient algorithm is presented for exact simulation of the stochastic time evolution of spatially homogeneous aggregation-fragmentation processes featuring multiple components or conservation laws. The algorithm can predict the average size and composition distributions of aggregating particles as well as their fluctuations, regardless of the functional form (e.g., composition dependence) of the aggregation or fragmentation kernels. Furthermore, it accurately predicts the complete time evolutions of all moments of the size and composition distributions, even for systems that exhibit gel transitions. We demonstrate the robustness and utility of the algorithm in case studies of linear and branched polymerization processes, the last of which is a two-component process. These simulation results provide the stochastic description of these processes and give new insights into their gel transitions, fluctuations, and long-time behavior when deterministic approaches to aggregation kinetics may not be reliable.
  • Publication
    Interaction of the Gelsolin-Derived Antibacterial PBP 10 Peptide with Lipid Bilayers and Cell Membranes
    (2006-09-01) Bucki, Robert; Janmey, Paul
    PBP 10, an antibacterial, cell membrane-permeant rhodamine B-conjugated peptide derived from the polyphosphoinositide binding site of gelsolin, interacts selectively with both lipopolysaccharides (LPS) and lipoteichoic acid (LTA), the distinct components of gram-negative and gram-positive bacteria, respectively. Isolated LPS and LTA decrease the antimicrobial activities of PBP 10, as well as other antimicrobial peptides, such as cathelicidin-LL37 (LL37) and mellitin. In an effort to elucidate the mechanism of bacterial killing by PBP 10, we compared its effects on artificial lipid bilayers and eukaryotic cell membranes with the actions of the mellitin, magainin II, and LL37 peptides. This study reveals that pore formation is unlikely to be involved in PBP 10-mediated membrane destabilization. We also investigated the effects of these peptides on platelets and red blood cells (RBCs). Comparison of these antimicrobial peptides shows that only mellitin has a toxic effect on platelets and RBCs in a concentration range concomitant with its bactericidal activity. The hemolytic activities of the PBP 10 and LL37 peptides significantly increase when RBCs are osmotically swollen in hypotonic solution, indicating that these antibacterial peptides may take advantage of the more extended form of bacterial membranes in exerting their killing activities. Additionally, we found that LL37 hemolytic activity was much higher when RBCs were induced to expose phosphatidylserine to the external leaflet of their plasma membranes. This finding suggests that asymmetrical distribution of phospholipids in the external membranes of eukaryotic cells may represent an important factor in determining the specificity of antibacterial peptides for targeting bacteria rather than eukaryotic cells.
  • Publication
    Domain unfolding in neurofilament sidearms: effects of phosphorylation and ATP
    (2002-10-10) Aranda-Espinoza, Helim; Carl, Philippe; Janmey, Paul; Leterrier, Jean-François; Discher, Dennis E
    Lateral projections of neuro¢laments (NF) called sidearms (SA) a¡ect axon stability and caliber. SA phosphorylation is thought to modulate inter-NF distance and interactions between NF and other subcellular organelles. SA were probed by atomic force microscopy (AFM) and dynamic light scattering (DLS) as a function of phosphorylation and ATP content. DLS shows SA are larger when phosphorylated, and AFM shows four unfoldable domains in SA regardless of phosphorylation state or the presence of ATP. However, the native phosphorylated SA requires three-fold higher force to unfold by AFM than dephosphorylated SA, suggesting a less pliant as well as larger structure when phosphorylated.
  • Publication
    Mechanisms of Mitochondria–Neurofilament Interactions
    (2003-10-08) Wagner, Oliver I; Lifshitz, Jonathan; Janmey, Paul A; Linden, M.; McIntosh, T. K; Leterrier, Jean-François
    Mitochondria are localized to regions of the cell where ATP consumption is high and are dispersed according to changes in local energy needs. In addition to motion directed by molecular motors, mitochondrial distribution in neuronal cells appears to depend on the docking of mitochondria to microtubules and neurofilaments. We examined interactions between mitochondria and neurofilaments using fluorescence microscopy, dynamic light scattering, atomic force microscopy, and sedimentation assays. Mitochondria-neurofilament interactions depend on mitochondrial membrane potential, as revealed by staining with a membrane potential sensitive dye (JC-1) in the presence of substrates/ADP or uncouplers (valinomycin/carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone) and are affected by the phosphorylation status of neurofilaments and neurofilament sidearms. Antibodies against the neurofilament heavy subunit disrupt binding between mitochondria and neurofilaments, and isolated neurofilament sidearms alone interact with mitochondria, suggesting that they mediate the interactions between the two structures. These data suggest that specific and regulated mitochondrial-neurofilament interactions occur in situ and may contribute to the dynamic distribution of these organelles within the cytoplasm of neurons.
  • Publication
    Separate Functions of Gelsolin Mediate Sequential Steps of Collagen Phagocytosis
    (2005-11-01) Arora, P. D; Chan, M.W. C; Anderson, R. A; Janmey, Paul A; McCulloch, C. A
    Collagen phagocytosis is a critical mediator of extracellular matrix remodeling. Whereas the binding step of collagen phagocytosis is facilitated by Ca2+-dependent, gelsolin-mediated severing of actin filaments, the regulation of the collagen internalization step is not defined. We determined here whether phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2] regulation of gelsolin is required for collagen internalization. In gelsolin null fibroblasts transfected with gelsolin severing mutants, actin severing and collagen binding were strongly impaired but internalization and actin monomer addition at collagen bead sites were much less affected. PI(4,5)P2 accumulated around collagen during internalization and was associated with gelsolin. Cell-permeable peptides mimicking the PI(4,5)P2 binding site of gelsolin blocked actin monomer addition, the association of gelsolin with actin at phagosomes, and collagen internalization but did not affect collagen binding. Collagen beads induced recruitment of type 1 γ phosphatidylinositol phosphate kinase (PIPK1γ661) to internalization sites. Dominant negative constructs and RNA interference demonstrated a requirement for catalytically active PIPK1γ661 for collagen internalization. We conclude that separate functions of gelsolin mediate sequential stages of collagen phagocytosis: Ca2+-dependent actin severing facilitates collagen binding, whereas PI(4,5)P2-dependent regulation of gelsolin promotes the actin assembly required for internalization of collagen fibrils.
  • Publication
    Counterion-Mediated Attraction and Kinks on Loops of Semiflexible Polyelectrolyte Bundles
    (2006-06-21) Cebers, A.; Dogic, Z.; Janmey, Paul
    The formation of kinks in a loop of bundled polyelectrolyte filaments is analyzed in terms of the thermal fluctuations of charge density due to polyvalent counterions adsorbed on the polyelectrolyte filaments. It is found that the counterion-mediated attraction energy of filaments depends on their bending. By consideration of curvature elasticity energy and counterion-mediated attraction between polyelectrolyte filaments, the characteristic width of the kink and the number of kinks per loop is found to be in reasonable agreement with existing experimental data for rings of bundled actin filaments.
  • Publication
    Regulation and Function of Tenascin-C in Heart Valve Homeostasis
    (2006-10-01) Kalola, Anand
    Tenascin-C (TN-C) interacts with extracellular molecules and plays a role in cell adhesion, signaling, and differentiation. There is evidence that TN-C is regulated by mechanical forces and since the heart valve is a highly dynamic structure, it is possible that TN-C is expressed within specific sites within the aortic valve, as these sites are subject to unique mechanical forces. It is also reasonable to expect differences in TN-C expression between the pulmonary and the aortic valve because these two locations experience different levels of mechanical force. Here we compare TN-C expression levels in adult pulmonary versus aortic valves and determine if different cell types within aortic valves express different amounts of TNC. Our results indicate that TN-C is expressed in normal post-natal heart valves and expression is higher on the aortic versus ventricular side of the aortic valve. TN-C expression may be higher in aortic versus pulmonary valve. SMC, fibroblasts or myofibroblasts may produce TN-C, but endothelial cells appear not to produce TN-C. These studies will help us in determining the role TN-C plays in normal heart valve tissue homeostasis and how different cell types react to different mechanical forces.
  • Publication
    Phosphatidylinositol-4,5 Bisphosphate Produced by PIP5K(gamma) Regulates Gelsolin, Actin Assembly, and Adhesion Strength of N-Cadherin Junctions
    (2005-08-01) El Sayegh, T. Y.; Arora, P. D; Ling, K.; Laschinger, C.; Janmey, Paul; Anderson, R. A.; McCulloch, C. A.
    Phosphoinositides regulate several actin-binding proteins but their role at intercellular adhesions has not been defined. We found that phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) was generated at sites of N-cadherin–mediated intercellular adhesion and was a critical regulator of intercellular adhesion strength. Immunostaining for PI(4,5)P2 or transfection with GFP-PH-PLCδ showed that PI(4,5)P2 was enriched at sites of N-cadherin adhesions and this enrichment required activated Rac1. Isoform-specific immunostaining for type I phosphatidylinositol 4-phosphate 5 kinase (PIP5KI) showed that PIP5KIγ was spatially associated with N-cadherin–Fc beads. Association of PIP5KIγ with N-cadherin adhesions was in part dependent on the activation of RhoA. Transfection with catalytically inactive PIP5KIγ blocked the enrichment of PI(4,5)P2 around beads. Catalytically inactive PIP5KIγ or a cell-permeant peptide that mimics and competes for the PI(4,5)P2-binding region of the actin-binding protein gelsolin inhibited incorporation of actin monomers in response to N-cadherin ligation and reduced intercellular adhesion strength by more than twofold. Gelsolin null fibroblasts transfected with a gelsolin severing mutant containing an intact PI(4,5)P2 binding region, demonstrated intercellular adhesion strength similar to wild-type transfected controls. We conclude that PIP5KIγ-mediated generation of PI(4,5)P2 at sites of N-cadherin contacts regulates intercellular adhesion strength, an effect due in part to PI(4,5)P2-mediated regulation of gelsolin.
  • Publication
    Signal-to-noise measurements utilizing a novel dual-energy multimedia detector
    (2001-08-01) Giakos, G. C; Chowdhury, S.; Shah, N.; Vedantham, Srinivasan; Passerini, A. G; Suryanarayanan, Sankararaman; Nemer, R.; Mehta, K.; Patnekar, N.; Sumrain, S.; Nataraj, K.; Scheiber, Christian
    Dual-energy measurements are presented utilizing a novel slot-scan digital radiographic imaging detector, operating on gaseous solid state ionization principles. The novel multimedia detector has two basic functional components: a noble gas-filled detector volume operating on gas microstrip principles, and a solid state detector volume. The purpose of this study is to investigate the potential use of this multimedia detector for enhanced dual-energy imaging. The experimental results indicate that the multimedia detector exhibits a large subtracted signal-to-noise ratio. Although the intrinsic merit of this device is being explored for medical imaging, potential applications of the multimedia detector technology in other industrial areas, such as aerospace imaging, aviation security, and surveillance, are also very promising.