Publications by authors named "Lewis Romer"

56 Publications

HEYL Regulates Neoangiogenesis Through Overexpression in Both Breast Tumor Epithelium and Endothelium.

Front Oncol 2020 15;10:581459. Epub 2021 Jan 15.

Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD, United States.

Blocking tumor angiogenesis is an appealing therapeutic strategy, but to date, success has been elusive. We previously identified HEYL, a downstream target of Notch signaling, as an overexpressed gene in both breast cancer cells and as a tumor endothelial marker, suggesting that HEYL overexpression in both compartments may contribute to neoangiogenesis. Carcinomas arising in double transgenic Her2-neu/HeyL mice showed higher tumor vessel density and significantly faster growth than tumors in parental Her2/neu mice. Providing mechanistic insight, microarray-based mRNA profiling of HS578T-tet-off-HEYL human breast cancer cells revealed upregulation of several angiogenic factors including CXCL1/2/3 upon HEYL expression, which was validated by RT-qPCR and protein array analysis. Upregulation of the cytokines CXCL1/2/3 occurred through direct binding of HEYL to their promoter sequences. We found that vessel growth and migration of human vascular endothelial cells (HUVECs) was promoted by conditioned medium from HS578T-tet-off-HEYL carcinoma cells, but was blocked by neutralizing antibodies against CXCL1/2/3. Supporting these findings, suppressing HEYL expression using shRNA in MDA-MB-231 cells significantly reduced tumor growth. In addition, suppressing the action of proangiogenic cytokines induced by HEYL using a small molecule inhibitor of the CXCl1/2/3 receptor, CXCR2, in combination with the anti-VEGF monoclonal antibody, bevacizumab, significantly reduced tumor growth of MDA-MB-231 xenografts. Thus, HEYL expression in tumor epithelium has a profound effect on the vascular microenvironment in promoting neoangiogenesis. Furthermore, we show that lack of HEYL expression in endothelial cells leads to defects in neoangiogenesis, both under normal physiological conditions and in cancer. Thus, HeyL-/- mice showed impaired vessel outgrowth in the neonatal retina, while the growth of mammary tumor cells E0771 was retarded in syngeneic HeyL-/- mice compared to wild type C57/Bl6 mice. Blocking HEYL's angiogenesis-promoting function in both tumor cells and tumor-associated endothelium may enhance efficacy of therapy targeting the tumor vasculature in breast cancer.
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http://dx.doi.org/10.3389/fonc.2020.581459DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7845423PMC
January 2021

Biomimetic human small muscular pulmonary arteries.

Sci Adv 2020 03 25;6(13):eaaz2598. Epub 2020 Mar 25.

Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.

Changes in structure and function of small muscular arteries play a major role in the pathophysiology of pulmonary hypertension, a burgeoning public health challenge. Improved anatomically mimetic in vitro models of these microvessels are urgently needed because nonhuman vessels and previous models do not accurately recapitulate the microenvironment and architecture of the human microvascular wall. Here, we describe parallel biofabrication of photopatterned self-rolled biomimetic pulmonary arterial microvessels of tunable size and infrastructure. These microvessels feature anatomically accurate layering and patterning of aligned human smooth muscle cells, extracellular matrix, and endothelial cells and exhibit notable increases in endothelial longevity and nitric oxide production. Computational image processing yielded high-resolution 3D perspectives of cells and proteins. Our studies provide a new paradigm for engineering multicellular tissues with precise 3D spatial positioning of multiple constituents in planar moieties, providing a biomimetic platform for investigation of microvascular pathobiology in human disease.
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http://dx.doi.org/10.1126/sciadv.aaz2598DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7096158PMC
March 2020

3D printing and characterization of a soft and biostable elastomer with high flexibility and strength for biomedical applications.

J Mech Behav Biomed Mater 2020 04 23;104:103649. Epub 2020 Jan 23.

Department of Mechanical Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD, 21218, USA; Hopkins Extreme Materials Institute, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD, 21218, USA; Institute for NanoBioTechnology, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD, 21218, USA. Electronic address:

Recent advancements in 3D printing have revolutionized biomedical engineering by enabling the manufacture of complex and functional devices in a low-cost, customizable, and small-batch fabrication manner. Soft elastomers are particularly important for biomedical applications because they can provide similar mechanical properties as tissues with improved biocompatibility. However, there are very few biocompatible elastomers with 3D printability, and little is known about the material properties of biocompatible 3D printable elastomers. Here, we report a new framework to 3D print a soft, biocompatible, and biostable polycarbonate-based urethane silicone (PCU-Sil) with minimal defects. We systematically characterize the rheological and thermal properties of the material to guide the 3D printing process and have determined a range of processing conditions. Optimal printing parameters such as printing speed, temperature, and layer height are determined via parametric studies aimed at minimizing porosity while maximizing the geometric accuracy of the 3D-printed samples as evaluated via micro-CT. We also characterize the mechanical properties of the 3D-printed structures under quasistatic and cyclic loading, degradation behavior and biocompatibility. The 3D-printed materials show a Young's modulus of 6.9 ± 0.85 MPa and a failure strain of 457 ± 37.7% while exhibiting good cell viability. Finally, compliant and free-standing structures including a patient-specific heart model and a bifurcating arterial structure are printed to demonstrate the versatility of the 3D-printed material. We anticipate that the 3D printing framework presented in this work will open up new possibilities not only for PCU-Sil, but also for other soft, biocompatible and thermoplastic polymers in various biomedical applications requiring high flexibility and strength combined with biocompatibility, such as vascular implants, heart valves, and catheters.
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http://dx.doi.org/10.1016/j.jmbbm.2020.103649DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7078069PMC
April 2020

Spectrum of Current Management of Pediatric Pulmonary Hypertensive Crisis.

Crit Care Explor 2019 Aug 9;1(8):e0037. Epub 2019 Aug 9.

Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD.

Pulmonary hypertension is a growing pediatric problem and children may present with pulmonary hypertensive crisis-a life-threatening emergency requiring acute interventions. The aim of this study was to characterize the broad spectrum of care provided in North American PICUs for children who present with pulmonary hypertensive crisis.

Design: Electronic cross-sectional survey. Survey questions covered the following: demographics of the respondents, institution, and patient population; pulmonary hypertension diagnostic modalities; pulmonary hypertension-specific pharmacotherapies; supportive therapies, including sedation, ventilation, and inotropic support; and components of multidisciplinary teams.

Setting: PICUs in the United States and Canada.

Subjects: Faculty members from surveyed institutions.

Interventions: None.

Measurement And Main Results: The response rate was 50% of 99 identified institutions. Of the respondents, 82.2% were pediatric intensivists from large units, and 73.9% had over a decade of experience beyond training. Respondents provided care for a median of 10 patients/yr with acute pulmonary hypertensive crisis. Formal echocardiography protocols existed at 61.1% of institutions with varying components reported. There were no consistent indications for cardiac catheterization during a pulmonary hypertensive crisis admission. All institutions used inhaled nitric oxide, and enteral phosphodiesterase type 5 inhibitor was the most frequently used additional targeted vasodilator therapy. Milrinone and epinephrine were the most frequently used vasoactive infusions. Results showed no preferred approach to mechanical ventilation. Fentanyl and dexmedetomidine were the preferred sedative infusions. A formal pulmonary hypertension consulting team was reported at 51.1% of institutions, and the three most common personnel were pediatric cardiologist, pediatric pulmonologist, and advanced practice nurse.

Conclusions: The management of critically ill children with acute pulmonary hypertensive crisis is diverse. Findings from this survey may inform formal recommendations - particularly with regard to care team composition and pulmonary vasodilator therapies - as North American guidelines are currently lacking. Additional work is needed to determine best practice, standardization of practice, and resulting impact on outcomes.
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http://dx.doi.org/10.1097/CCE.0000000000000037DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7063944PMC
August 2019

Surviving Sepsis Campaign International Guidelines for the Management of Septic Shock and Sepsis-Associated Organ Dysfunction in Children.

Pediatr Crit Care Med 2020 02;21(2):e52-e106

Paris South University Hospitals-Assistance Publique Hopitaux de Paris, Paris, France.

Objectives: To develop evidence-based recommendations for clinicians caring for children (including infants, school-aged children, and adolescents) with septic shock and other sepsis-associated organ dysfunction.

Design: A panel of 49 international experts, representing 12 international organizations, as well as three methodologists and three public members was convened. Panel members assembled at key international meetings (for those panel members attending the conference), and a stand-alone meeting was held for all panel members in November 2018. A formal conflict-of-interest policy was developed at the onset of the process and enforced throughout. Teleconferences and electronic-based discussion among the chairs, co-chairs, methodologists, and group heads, as well as within subgroups, served as an integral part of the guideline development process.

Methods: The panel consisted of six subgroups: recognition and management of infection, hemodynamics and resuscitation, ventilation, endocrine and metabolic therapies, adjunctive therapies, and research priorities. We conducted a systematic review for each Population, Intervention, Control, and Outcomes question to identify the best available evidence, statistically summarized the evidence, and then assessed the quality of evidence using the Grading of Recommendations Assessment, Development, and Evaluation approach. We used the evidence-to-decision framework to formulate recommendations as strong or weak, or as a best practice statement. In addition, "in our practice" statements were included when evidence was inconclusive to issue a recommendation, but the panel felt that some guidance based on practice patterns may be appropriate.

Results: The panel provided 77 statements on the management and resuscitation of children with septic shock and other sepsis-associated organ dysfunction. Overall, six were strong recommendations, 52 were weak recommendations, and nine were best-practice statements. For 13 questions, no recommendations could be made; but, for 10 of these, "in our practice" statements were provided. In addition, 49 research priorities were identified.

Conclusions: A large cohort of international experts was able to achieve consensus regarding many recommendations for the best care of children with sepsis, acknowledging that most aspects of care had relatively low quality of evidence resulting in the frequent issuance of weak recommendations. Despite this challenge, these recommendations regarding the management of children with septic shock and other sepsis-associated organ dysfunction provide a foundation for consistent care to improve outcomes and inform future research.
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http://dx.doi.org/10.1097/PCC.0000000000002198DOI Listing
February 2020

Surviving sepsis campaign international guidelines for the management of septic shock and sepsis-associated organ dysfunction in children.

Intensive Care Med 2020 02;46(Suppl 1):10-67

Paris South University Hospitals-Assistance Publique Hopitaux de Paris, Paris, France.

Objectives: To develop evidence-based recommendations for clinicians caring for children (including infants, school-aged children, and adolescents) with septic shock and other sepsis-associated organ dysfunction.

Design: A panel of 49 international experts, representing 12 international organizations, as well as three methodologists and three public members was convened. Panel members assembled at key international meetings (for those panel members attending the conference), and a stand-alone meeting was held for all panel members in November 2018. A formal conflict-of-interest policy was developed at the onset of the process and enforced throughout. Teleconferences and electronic-based discussion among the chairs, co-chairs, methodologists, and group heads, as well as within subgroups, served as an integral part of the guideline development process.

Methods: The panel consisted of six subgroups: recognition and management of infection, hemodynamics and resuscitation, ventilation, endocrine and metabolic therapies, adjunctive therapies, and research priorities. We conducted a systematic review for each Population, Intervention, Control, and Outcomes question to identify the best available evidence, statistically summarized the evidence, and then assessed the quality of evidence using the Grading of Recommendations Assessment, Development, and Evaluation approach. We used the evidence-to-decision framework to formulate recommendations as strong or weak, or as a best practice statement. In addition, "in our practice" statements were included when evidence was inconclusive to issue a recommendation, but the panel felt that some guidance based on practice patterns may be appropriate.

Results: The panel provided 77 statements on the management and resuscitation of children with septic shock and other sepsis-associated organ dysfunction. Overall, six were strong recommendations, 49 were weak recommendations, and nine were best-practice statements. For 13 questions, no recommendations could be made; but, for 10 of these, "in our practice" statements were provided. In addition, 52 research priorities were identified.

Conclusions: A large cohort of international experts was able to achieve consensus regarding many recommendations for the best care of children with sepsis, acknowledging that most aspects of care had relatively low quality of evidence resulting in the frequent issuance of weak recommendations. Despite this challenge, these recommendations regarding the management of children with septic shock and other sepsis-associated organ dysfunction provide a foundation for consistent care to improve outcomes and inform future research.
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http://dx.doi.org/10.1007/s00134-019-05878-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7095013PMC
February 2020

Direct Ink Writing of Poly(tetrafluoroethylene) (PTFE) with Tunable Mechanical Properties.

ACS Appl Mater Interfaces 2019 Aug 23;11(31):28289-28295. Epub 2019 Jul 23.

Poly(tetrafluoroethylene) (PTFE) is a unique polymer with highly desirable properties such as resistance to chemical degradation, biocompatibility, hydrophobicity, antistiction, and low friction coefficient. However, due to its high melt viscosity, it is not possible to three-dimensional (3D)-print PTFE structures using nozzle-based extrusion. Here, we report a new and versatile strategy for 3D-printing PTFE structures using direct ink writing (DIW). Our approach is based on a newly formulated PTFE nanoparticle ink and thermal treatment process. The ink was formulated by mixing an aqueous dispersion of surfactant-stabilized PTFE nanoparticles with a binding gum to optimize its shear-thinning properties required for DIW. We developed a multistage thermal treatment to fuse the PTFE nanoparticles, solidify the printed structures, and remove the additives. We have extensively characterized the rheological and mechanical properties and processing parameters of these structures using imaging, mechanical testing, and statistical design of experiments. Importantly, several of the mechanical and structural properties of the final-printed PTFE structures resemble that of compression-molded PTFE, and additionally, the mechanical properties are tunable. We anticipate that this versatile approach facilitates the production of 3D-printed PTFE components using DIW with significant potential applications in engineering and medicine.
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http://dx.doi.org/10.1021/acsami.9b07279DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6813788PMC
August 2019

Inositol hexakisphosphate kinase 3 promotes focal adhesion turnover via interactions with dynein intermediate chain 2.

Proc Natl Acad Sci U S A 2019 02 4;116(8):3278-3287. Epub 2019 Feb 4.

Department of Physiology and Pathophysiology, Tianjin Medical University, 300070 Tianjin, China;

Cells express a family of three inositol hexakisphosphate kinases (IP6Ks). Although sharing the same enzymatic activity, individual IP6Ks mediate different cellular processes. Here we report that IP6K3 is enriched at the leading edge of migrating cells where it associates with dynein intermediate chain 2 (DIC2). Using immunofluorescence microscopy and total internal reflection fluorescence microscopy, we found that DIC2 and IP6K3 are recruited interdependently to the leading edge of migrating cells, where they function coordinately to enhance the turnover of focal adhesions. Deletion of IP6K3 causes defects in cell motility and neuronal dendritic growth, eventually leading to brain malformations. Our results reveal a mechanism whereby IP6K3 functions in coordination with DIC2 in a confined intracellular microenvironment to promote focal adhesion turnover.
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http://dx.doi.org/10.1073/pnas.1817001116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6386689PMC
February 2019

Dual-Gel 4D Printing of Bioinspired Tubes.

ACS Appl Mater Interfaces 2019 Feb 12;11(8):8492-8498. Epub 2019 Feb 12.

JSR Corporation , 1-9-2, Higashi-Shimbashi , Minato-ku, Tokyo 105-8640 , Japan.

The distribution of periodic patterns of materials with radial or bilateral symmetry is a universal natural design principle. Among the many biological forms, tubular shapes are a common motif in many organisms, and they are also important for bioimplants and soft robots. However, the simple design principle of strategic placement of 3D printed segments of swelling and nonswelling materials to achieve widely different functionalities is yet to be demonstrated. Here, we report the design, fabrication, and characterization of segmented 3D printed gel tubes composed of an active thermally responsive swelling gel (poly N-isopropylacrylamide) and a passive thermally nonresponsive gel (polyacrylamide). Using finite element simulations and experiments, we report a variety of shape changes including uniaxial elongation, radial expansion, bending, and gripping based on two gels. Actualization and characterization of thermally induced shape changes are of key importance to robotics and biomedical engineering. Our studies present rational approaches to engineer complex parameters with a high level of customization and tunability for additive manufacturing of dynamic gel structures.
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http://dx.doi.org/10.1021/acsami.8b17218DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6785027PMC
February 2019

3D Hybrid Small Scale Devices.

Small 2018 07 10;14(27):e1702497. Epub 2018 May 10.

Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA.

Interfacing nano/microscale elements with biological components in 3D contexts opens new possibilities for mimicry, bionics, and augmentation of organismically and anatomically inspired materials. Abiotic nanoscale elements such as plasmonic nanostructures, piezoelectric ribbons, and thin film semiconductor devices interact with electromagnetic fields to facilitate advanced capabilities such as communication at a distance, digital feedback loops, logic, and memory. Biological components such as proteins, polynucleotides, cells, and organs feature complex chemical synthetic networks that can regulate growth, change shape, adapt, and regenerate. Abiotic and biotic components can be integrated in all three dimensions in a well-ordered and programmed manner with high tunability, versatility, and resolution to produce radically new materials and hybrid devices such as sensor fabrics, anatomically mimetic microfluidic modules, artificial tissues, smart prostheses, and bionic devices. In this critical Review, applications of small scale devices in 3D hybrid integration, biomicrofluidics, advanced prostheses, and bionic organs are discussed.
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http://dx.doi.org/10.1002/smll.201702497DOI Listing
July 2018

Hypoxia Triggers SENP1 (Sentrin-Specific Protease 1) Modulation of KLF15 (Kruppel-Like Factor 15) and Transcriptional Regulation of Arg2 (Arginase 2) in Pulmonary Endothelium.

Arterioscler Thromb Vasc Biol 2018 04 22;38(4):913-926. Epub 2018 Feb 22.

From the Departments of Anesthesiology and Critical Care Medicine (D.P., Y.N., M.C.R., D.H., A.B., L.S., D.B., L.R.), Cell Biology (L.R.), Biomedical Engineering (D.B., L.R.), and Pediatrics, and the Center for Cell Dynamics (L.R.), Division of Cardiology (G.K., T.L.), and Division of Pulmonary and Critical Care Medicine, Department of Medicine (L.A.S.), Johns Hopkins Medical Institutions, Baltimore, MD.

Objective: KLF15 (Kruppel-like factor 15) has recently been shown to suppress activation of proinflammatory processes that contribute to atherogenesis in vascular smooth muscle, however, the role of KLF15 in vascular endothelial function is unknown. Arginase mediates inflammatory vasculopathy and vascular injury in pulmonary hypertension. Here, we tested the hypothesis that KLF15 is a critical regulator of hypoxia-induced Arg2 (arginase 2) transcription in human pulmonary microvascular endothelial cells (HPMEC).

Approach And Results: Quiescent HPMEC express ample amounts of full-length KLF15. HPMECs exposed to 24 hours of hypoxia exhibited a marked decrease in KLF15 protein levels and a reciprocal increase in Arg2 protein and mRNA. Chromatin immunoprecipitation indicated direct binding of KLF15 to the Arg2 promoter, which was relieved with HPMEC exposure to hypoxia. Furthermore, overexpression of KLF15 in HPMEC reversed hypoxia-induced augmentation of Arg2 abundance and arginase activity and rescued nitric oxide (NO) production. Ectopic KLF15 also reversed hypoxia-induced endothelium-mediated vasodilatation in isolated rat pulmonary artery rings. Mechanisms by which hypoxia regulates KLF15 abundance, stability, and compartmentalization to the nucleus in HPMEC were then investigated. Hypoxia triggered deSUMOylation of KLF15 by SENP1 (sentrin-specific protease 1), and translocation of KLF15 from nucleus to cytoplasm.

Conclusions: KLF15 is a critical regulator of pulmonary endothelial homeostasis via repression of endothelial Arg2 expression. KLF15 abundance and nuclear compartmentalization are regulated by SUMOylation/deSUMOylation-a hypoxia-sensitive process that is controlled by SENP1. Strategies including overexpression of KLF15 or inhibition of SENP1 may represent novel therapeutic targets for pulmonary hypertension.
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http://dx.doi.org/10.1161/ATVBAHA.117.310660DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6738933PMC
April 2018

Perioperative events in children with pulmonary hypertension undergoing non-cardiac procedures.

Pulm Circ 2018 Jan-Mar;8(1):2045893217738143. Epub 2017 Oct 3.

6 Division of Anesthesiology, Sedation and Perioperative Medicine, Children's National Health System, Washington, DC, USA.

Prior limited research indicates that children with pulmonary hypertension (PH) have higher rates of adverse perioperative outcomes when undergoing non-cardiac procedures and cardiac catheterizations. We examined a single-center retrospective cohort of children with active or pharmacologically controlled PH who underwent cardiac catheterization or non-cardiac surgery during 2006-2014. Preoperative characteristics and perioperative courses were examined to determine relationships between the severity or etiology of PH, type of procedure, and occurrence of major and minor events. We identified 77 patients who underwent 148 procedures at a median age of six months. The most common PH etiologies were bronchopulmonary dysplasia (46.7%), congenital heart disease (29.9%), and congenital diaphragmatic hernia (14.3%). Cardiac catheterizations (39.2%), and abdominal (29.1%) and central venous access (8.9%) were the most common procedures. Major events included failed planned extubation (5.6%), postoperative cardiac arrest (4.7%), induction or intraoperative cardiac arrest (2%), and postoperative death (1.4%). Major events were more frequent in patients with severe baseline PH ( P = 0.006) and the incidence was associated with procedure type ( P = 0.05). Preoperative inhaled nitric oxide and prostacyclin analog therapies were associated with decreased incidence of minor events (odds ratio [OR] = 0.32, P = 0.046 and OR = 0.24, P = 0.008, respectively), but no change in the incidence of major events. PH etiology was not associated with events ( P = 0.24). Children with PH have increased risk of perioperative complications; cardiac arrest and death occur more frequently in patients with severe PH and those undergoing thoracic procedures. Risk may be modified by using preoperative pulmonary vasodilator therapy and lends itself to further prospective studies.
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http://dx.doi.org/10.1177/2045893217738143DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5731725PMC
October 2017

Opsin 3 and 4 mediate light-induced pulmonary vasorelaxation that is potentiated by G protein-coupled receptor kinase 2 inhibition.

Am J Physiol Lung Cell Mol Physiol 2018 01 7;314(1):L93-L106. Epub 2017 Sep 7.

Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University , Baltimore, Maryland.

We recently demonstrated that blue light induces vasorelaxation in the systemic mouse circulation, a phenomenon mediated by the nonvisual G protein-coupled receptor melanopsin (Opsin 4; Opn4). Here we tested the hypothesis that nonvisual opsins mediate photorelaxation in the pulmonary circulation. We discovered Opsin 3 (Opn3), Opn4, and G protein-coupled receptor kinase 2 (GRK2) in rat pulmonary arteries (PAs) and in pulmonary arterial smooth muscle cells (PASMCs), where the opsins interact directly with GRK2, as demonstrated with a proximity ligation assay. Light elicited an intensity-dependent relaxation of PAs preconstricted with phenylephrine (PE), with a maximum response between 400 and 460 nm (blue light). Wavelength-specific photorelaxation was attenuated in PAs from Opn4 mice and further reduced following shRNA-mediated knockdown of Opn3. Inhibition of GRK2 amplified the response and prevented physiological desensitization to repeated light exposure. Blue light also prevented PE-induced constriction in isolated PAs, decreased basal tone, ablated PE-induced single-cell contraction of PASMCs, and reversed PE-induced depolarization in PASMCs when GRK2 was inhibited. The photorelaxation response was modulated by soluble guanylyl cyclase but not by protein kinase G or nitric oxide. Most importantly, blue light induced significant vasorelaxation of PAs from rats with chronic pulmonary hypertension and effectively lowered pulmonary arterial pressure in isolated intact perfused rat lungs subjected to acute hypoxia. These findings show that functional Opn3 and Opn4 in PAs represent an endogenous "optogenetic system" that mediates photorelaxation in the pulmonary vasculature. Phototherapy in conjunction with GRK2 inhibition could therefore provide an alternative treatment strategy for pulmonary vasoconstrictive disorders.
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http://dx.doi.org/10.1152/ajplung.00091.2017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6335007PMC
January 2018

Pulmonary Hypertension Therapy and a Systematic Review of Efficacy and Safety of PDE-5 Inhibitors.

Pediatrics 2017 Mar;139(3)

Departments of Anesthesiology and Critical Care Medicine.

Pulmonary hypertension (PH) is a syndrome that is of growing concern to pediatricians worldwide. Recent data led to concerns about the safety of phosphodiesterase type 5 (PDE5) inhibitors in children and a US Food and Drug Administration safety advisory. Our objective is to provide insight into therapies for PH in children and to systematically review the comparative effectiveness and safety of PDE5 inhibitors in the management of pediatric patients with PH. We searched the following databases through February 2015: Medline, Embase, SCOPUS, and the Cochrane Central Register of Controlled Trials. We included studies that examined PDE5 inhibitor use in children with PH. Allowed comparators were either no medication or other classes of medication for management of PH. Study inclusion was via a 2-stage process with 2 reviewers and a predesigned form. Of 1270 papers identified by the literature search, 21 were included: 8 randomized controlled trials and 13 observational studies (9 retrospective, 4 prospective). There is strong evidence that PDE5 inhibitor use improves echocardiography measurements, cardiac catheterization parameters, and oxygenation compared with baseline or placebo in pediatric patients with PH. Evidence suggests that low- and moderate-dose sildenafil are safe regimens for children. There are a relatively small number of randomized controlled trials that address use of PDE5 inhibitors in pediatric patients with PH. PDE5 inhibitors are effective agents for cardiovascular and oxygenation end points in pediatric PH and important components of a multimodal pharmacotherapeutic approach to this growing challenge. Additional studies are needed to define optimal PH therapy in childhood.
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http://dx.doi.org/10.1542/peds.2016-1450DOI Listing
March 2017

Cystathionine γ-lyase protects vascular endothelium: a role for inhibition of histone deacetylase 6.

Am J Physiol Heart Circ Physiol 2017 Apr 10;312(4):H711-H720. Epub 2017 Feb 10.

Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland;

Endothelial cystathionine γ-lyase (CSEγ) contributes to cardiovascular homeostasis, mainly through production of HS. However, the molecular mechanisms that control CSEγ gene expression in the endothelium during cardiovascular diseases are unclear. The aim of the current study is to determine the role of specific histone deacetylases (HDACs) in the regulation of endothelial CSEγ. Reduced CSEγ mRNA expression and protein abundance were observed in human aortic endothelial cells (HAEC) exposed to oxidized LDL (OxLDL) and in aortas from atherogenic apolipoprotein E knockout (ApoE) mice fed a high-fat diet compared with controls. Intact murine aortic rings exposed to OxLDL (50 μg/ml) for 24 h exhibited impaired endothelium-dependent vasorelaxation that was blocked by CSEγ overexpression or the HS donor NaHS. CSEγ expression was upregulated by pan-HDAC inhibitors and by class II-specific HDAC inhibitors, but not by other class-specific inhibitors. The HDAC6 selective inhibitor tubacin and HDAC6-specific siRNA increased CSEγ expression and blocked OxLDL-mediated reductions in endothelial CSEγ expression and CSEγ promoter activity, indicating that HDAC6 is a specific regulator of CSEγ expression. Consistent with this finding, HDAC6 mRNA, protein expression, and activity were upregulated in OxLDL-exposed HAEC, but not in human aortic smooth muscle cells. HDAC6 protein levels in aortas from high-fat diet-fed ApoE mice were comparable to those in controls, whereas HDAC6 activity was robustly upregulated. Together, our findings indicate that HDAC6 is upregulated by atherogenic stimuli via posttranslational modifications and is a critical regulator of CSEγ expression in vascular endothelium. Inhibition of HDAC6 activity may improve endothelial function and prevent or reverse the development of atherosclerosis. Oxidative injury to endothelial cells by oxidized LDL reduced cystathionine γ-lyase (CSEγ) expression and HS production, leading to endothelial dysfunction, which was prevented by histone deacetylase 6 (HDAC6) inhibition. Our data suggest HDAC6 as a novel therapeutic target to prevent the development of atherosclerosis.
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http://dx.doi.org/10.1152/ajpheart.00724.2016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5407166PMC
April 2017

A Self-Folding Hydrogel In Vitro Model for Ductal Carcinoma.

Tissue Eng Part C Methods 2016 Apr 16;22(4):398-407. Epub 2016 Mar 16.

1 Department of Chemical and Biomolecular Engineering, Johns Hopkins University , Baltimore, Maryland.

A significant challenge in oncology is the need to develop in vitro models that accurately mimic the complex microenvironment within and around normal and diseased tissues. Here, we describe a self-folding approach to create curved hydrogel microstructures that more accurately mimic the geometry of ducts and acini within the mammary glands, as compared to existing three-dimensional block-like models or flat dishes. The microstructures are composed of photopatterned bilayers of poly (ethylene glycol) diacrylate (PEGDA), a hydrogel widely used in tissue engineering. The PEGDA bilayers of dissimilar molecular weights spontaneously curve when released from the underlying substrate due to differential swelling ratios. The photopatterns can be altered via AutoCAD-designed photomasks so that a variety of ductal and acinar mimetic structures can be mass-produced. In addition, by co-polymerizing methacrylated gelatin (methagel) with PEGDA, microstructures with increased cell adherence are synthesized. Biocompatibility and versatility of our approach is highlighted by culturing either SUM159 cells, which were seeded postfabrication, or MDA-MB-231 cells, which were encapsulated in hydrogels; cell viability is verified over 9 and 15 days, respectively. We believe that self-folding processes and associated tubular, curved, and folded constructs like the ones demonstrated here can facilitate the design of more accurate in vitro models for investigating ductal carcinoma.
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http://dx.doi.org/10.1089/ten.TEC.2015.0442DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4827285PMC
April 2016

Trends in Hospitalization for Pediatric Pulmonary Hypertension.

Pediatrics 2015 Aug 6;136(2):241-50. Epub 2015 Jul 6.

Departments of Anesthesiology and Critical Care Medicine, Pediatrics, Biomedical Engineering, and Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland.

Background And Objectives: Pulmonary hypertension (PH) has been associated with substantial morbidity and mortality in children, but existing analyses of inpatient care are limited to small single-institution series or focused registries representative of selected patient subgroups. We examined US national data on pediatric PH hospitalizations to determine trends in volume, demographics, procedures performed during admission, and resource utilization.

Methods: Retrospective cohort study using a national administrative database of pediatric hospital discharges: the Kids' Inpatient Database.

Results: Children with PH accounted for 0.13% of the 43 million pediatric hospitalizations in the United States between 1997 and 2012, and discharges demonstrated an increasing trend over the study period (P < .0001). Cumulative, inflation-adjusted national hospital charges for PH hospitalizations rose (P = .0003) from $926 million in 1997 to $3.12 billion in 2012. Patients with PH without associated congenital heart disease (CHD) comprised an increasing and majority (56.4%) proportion over the study period (P < .0001), children without associated CHD admitted at urban teaching hospitals comprised the fastest-growing subgroup. In-hospital, all-cause mortality was high (5.9%) in children with PH, but demonstrated a decreasing trend (P < .0001).

Conclusions: Morbidity and mortality of pediatric PH continue to represent substantial and growing health care burdens. Shifts in case mix toward PH not associated with CHD, toward noncardiac procedures, and toward care in urban teaching hospitals will increase pressure to manage resource utilization in this small but growing patient group and to improve expertise and define excellence in PH care across a wide range of clinical settings.
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http://dx.doi.org/10.1542/peds.2014-3834DOI Listing
August 2015

Patterning of Fibroblast and Matrix Anisotropy within 3D Confinement is Driven by the Cytoskeleton.

Adv Healthc Mater 2016 Jan 1;5(1):146-58. Epub 2015 Jun 1.

Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, 21287, USA.

Effects of 3D confinement on cellular growth and matrix assembly are important in tissue engineering, developmental biology, and regenerative medicine. Polydimethylsiloxane wells with varying anisotropy are microfabicated using soft-lithography. Microcontact printing of bovine serum albumin is used to block cell adhesion to surfaces between wells. The orientations of fibroblast stress fibers, microtubules, and fibronectin fibrils are examined 1 day after cell seeding using laser scanning confocal microscopy, and anisotropy is quantified using a custom autocorrelation analysis. Actin, microtubules, and fibronectin exhibit higher anisotropy coefficients for cells grown in rectangular wells with aspect ratios of 1:4 and 1:8, as compared to those in wells with lower aspect ratios or in square wells. The effects of disabling individual cytoskeletal components on fibroblast responses to anisotropy are then tested by applying actin or microtubule polymerization inhibitors, Rho kinase inhibitor, or by siRNA-mediated knockdown of AXL or cofilin-1. Latrunculin A decreases cytoskeletal and matrix anisotropy, nocodazole ablates both, and Y27632 mutes cellular polarity while decreasing matrix anisotropy. AXL siRNA knockdown has little effect, as does siRNA knockdown of cofilin-1. These data identify several specific cytoskeletal strategies as targets for the manipulation of anisotropy in 3D tissue constructs.
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http://dx.doi.org/10.1002/adhm.201500030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5817161PMC
January 2016

NEDDylation promotes endothelial dysfunction: a role for HDAC2.

J Mol Cell Cardiol 2015 Apr 2;81:18-22. Epub 2015 Feb 2.

Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21287-4904, USA; Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21287-4904, USA; Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21287-4904, USA; Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21287-4904, USA; Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21287-4904, USA. Electronic address:

Emerging evidence strongly supports a role for HDAC2 in the transcriptional regulation of endothelial genes and vascular function. We have recently demonstrated that HDAC2 reciprocally regulates the transcription of Arginase2, which is itself a critical modulator of endothelial function via eNOS. Moreover HDAC2 levels are decreased in response to the atherogenic stimulus OxLDL via a mechanism that is apparently dependent upon proteasomal degradation. NEDDylation is a post-translational protein modification that is tightly linked to ubiquitination and thereby protein degradation. We propose that changes in NEDDylation may modulate vascular endothelial function in part through alterations in the proteasomal degradation of HDAC2. In HAEC, OxLDL exposure augmented global protein NEDDylation. Pre-incubation of mouse aortic rings with the NEDDylation activating enzyme inhibitor, MLN4924, prevented OxLDL-induced endothelial dysfunction. In HAEC, MLN enhanced HDAC2 abundance, decreased expression and activity of Arginase2, and blocked OxLDL-mediated reduction of HDAC2. Additionally, HDAC2 was shown to be a substrate for NEDD8 conjugation and this interaction was potentiated by OxLDL. Further, HDAC2 levels were reciprocally regulated by ectopic expression of NEDD8 and the de-NEDDylating enzyme SENP8. Our findings indicate that the observed improvement in endothelial dysfunction with inhibition of NEDDylation activating enzyme is likely due to an HDAC2-dependent decrease in Arginase2. NEDDylation activating enzyme may therefore be a novel target in endothelial dysfunction and atherogenesis.
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http://dx.doi.org/10.1016/j.yjmcc.2015.01.019DOI Listing
April 2015

Oriented matrix promotes directional tubulogenesis.

Acta Biomater 2015 Jan 8;11:264-73. Epub 2014 Sep 8.

Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Anesthesiology and Critical Care Medicine, Cell Biology, and Pediatrics, and the Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD, USA.

Detailed control over the structural organization of scaffolds and engineered tissue constructs is a critical need in the quest to engineer functional tissues using biomaterials. This work presents a new approach to spatially direct endothelial tubulogenesis. Micropatterned fibronectin substrates were used to control lung fibroblast adhesion and growth and the subsequent deposition of fibroblast-derived matrix during culture. The fibroblast-derived matrix produced on the micropatterned substrates was tightly oriented by these patterns, with an average variation of only 8.5°. Further, regions of this oriented extracellular matrix provided directional control of developing endothelial tubes to within 10° of the original micropatterned substrate design. Endothelial cells seeded directly onto the micropatterned substrate did not form tubes. A metric for matrix anisotropy showed a relationship between the fibroblast-derived matrix and the endothelial tubes that were subsequently developed on the same micropatterns with a resulting aspect ratio over 1.5 for endothelial tubulogenesis. Micropatterns in "L" and "Y" shapes were used to direct endothelial tubes to turn and branch with the same level of precision. These data demonstrate that anisotropic fibroblast-derived matrices instruct the alignment and shape of endothelial tube networks, thereby introducing an approach that could be adapted for future design of microvascular implants featuring organ-specific natural matrix that patterns microvascular growth.
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http://dx.doi.org/10.1016/j.actbio.2014.08.037DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4256113PMC
January 2015

Endothelial matrix assembly during capillary morphogenesis: insights from chimeric TagRFP-fibronectin matrix.

J Histochem Cytochem 2014 Nov 25;62(11):774-90. Epub 2014 Jul 25.

Anesthesiology and Critical Care Medicine (FC, LR), Johns Hopkins Medical Institutions, Baltimore, MDDepartment of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA (CAL)Cell Biology (LR), Johns Hopkins Medical Institutions, Baltimore, MDBiomedical Engineering (LR), Johns Hopkins Medical Institutions, Baltimore, MDPediatrics (LR), Johns Hopkins Medical Institutions, Baltimore, MDCenter for Cell Dynamics (LR), Johns Hopkins Medical Institutions, Baltimore, MDGraduate Program in Cellular and Molecular Medicine (VN), Johns Hopkins Medical Institutions, Baltimore, MDDepartment of Molecular and Cell Biology, The Weizmann Institute of Science, Rehovot, Israel (VR)

Biologically relevant, three-dimensional extracellular matrix is an essential component of in vitro vasculogenesis models. WI-38 fibroblasts assemble a 3D matrix that induces endothelial tubulogenesis, but this model is challenged by fibroblast senescence and the inability to distinguish endothelial cell-derived matrix from matrix made by WI-38 fibroblasts. Matrices produced by hTERT-immortalized WI-38 recapitulated those produced by wild type fibroblasts. ECM fibrils were heavily populated by tenascin-C, fibronectin, and type VI collagen. Nearly half of the total type I collagen, but only a small fraction of the type IV collagen, were incorporated into ECM. Stable hTERT-WI-38 transfectants expressing TagRFP-fibronectin incorporated TagRFP into ~90% of the fibronectin in 3D matrices. TagRFP-fibronectin colocalized with tenascin-C and with type I collagen in a pattern that was similar to that seen in matrices from wild type WI-38. Human Umbilical Vein Endothelial Cells (HUVEC) formed 3D adhesions and tubes on WI38-hTERT-TagRFP-FN-derived matrices, and the TagRFP-fibronectin component of this new 3D human fibroblast matrix model facilitated the demonstration of concentrated membrane type 1 metalloprotease and new HUVEC FN and collagen type IV fibrils during EC tubulogenesis. These findings indicate that WI-38-hTERT- and WI-38-hTERT-TagRFP-FN-derived matrices provide platforms for the definition of new matrix assembly and remodeling events during vasculogenesis.
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http://dx.doi.org/10.1369/0022155414547419DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4209295PMC
November 2014

OxLDL triggers retrograde translocation of arginase2 in aortic endothelial cells via ROCK and mitochondrial processing peptidase.

Circ Res 2014 Aug 5;115(4):450-9. Epub 2014 Jun 5.

From the Department of Anesthesiology and Critical Care Medicine (D.P., A.B., Y.J.O., F.C., Y.B., J.H.K., J.S., D.E.B., L.H.R.), Biomedical Engineering (J.S., D.E.B., L.H.R.), and Cell Biology, Pediatrics, Center for Cell Dynamics (L.H.R.), Mass Spectrometry and Proteomics Facility (T.N.B., R.N.C.), and Departments of Medicine and Biological Chemistry (J.V.E.), Johns Hopkins University School of Medicine, Baltimore, MD; and Lipoprotein Metabolism Section, Cardiovascular-Pulmonary Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (A.T.R.).

Rationale: Increased arginase activity contributes to endothelial dysfunction by competition for l-arginine substrate and reciprocal regulation of nitric oxide synthase (NOS). The rapid increase in arginase activity in human aortic endothelial cells exposed to oxidized low-density lipoprotein (OxLDL) is consistent with post-translational modification or subcellular trafficking.

Objective: To test the hypotheses that OxLDL triggers reverse translocation of mitochondrial arginase 2 (Arg2) to cytosol and Arg2 activation, and that this process is dependent on mitochondrial processing peptidase, lectin-like OxLDL receptor-1 receptor, and rho kinase.

Methods And Results: OxLDL-triggered translocation of Arg2 from mitochondria to cytosol in human aortic endothelial cells and in murine aortic intima with a concomitant rise in arginase activity. All of these changes were abolished by inhibition of mitochondrial processing peptidase or by its siRNA-mediated knockdown. Rho kinase inhibition and the absence of the lectin-like OxLDL receptor-1 in knockout mice also ablated translocation. Aminoterminal sequencing of Arg2 revealed 2 candidate mitochondrial targeting sequences, and deletion of either of these confined Arg2 to the cytoplasm. Inhibitors of mitochondrial processing peptidase or lectin-like OxLDL receptor-1 knockout attenuated OxLDL-mediated decrements in endothelial-specific NO production and increases in superoxide generation. Finally, Arg2(-/-) mice bred on an ApoE(-/-) background showed reduced plaque load, reduced reactive oxygen species production, enhanced NO, and improved endothelial function when compared with ApoE(-/-) controls.

Conclusions: These data demonstrate dual distribution of Arg2, a protein with an unambiguous mitochondrial targeting sequence, in mammalian cells, and its reverse translocation to cytoplasm by alterations in the extracellular milieu. This novel molecular mechanism drives OxLDL-mediated arginase activation, endothelial NOS uncoupling, endothelial dysfunction, and atherogenesis.
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http://dx.doi.org/10.1161/CIRCRESAHA.115.304262DOI Listing
August 2014

Transcriptional regulation of endothelial arginase 2 by histone deacetylase 2.

Arterioscler Thromb Vasc Biol 2014 Jul 15;34(7):1556-1566. Epub 2014 May 15.

Department of Anesthesiology and Critical Care Medicine, Johns Hopkins Medical Institutions, Baltimore, MD 21287-4904.

Objective: Arginase 2 (Arg2) is a critical target in atherosclerosis because it controls endothelial nitric oxide, proliferation, fibrosis, and inflammation. Regulators of Arg2 transcription in the endothelium have not been characterized. The goal of the current study is to determine the role of specific histone deacetylases (HDACs) in the regulation of endothelial Arg2 transcription and endothelial function.

Approach And Results: The HDAC inhibitor trichostatin A increased levels of Arg2 mRNA, protein, and activity in both human aortic endothelial cells and mouse aortic rings. These changes occurred in both time- and dose-dependent patterns and resulted in Arg2-dependent endothelial dysfunction. Trichostatin A and the atherogenic stimulus oxidized low-density lipoprotein enhanced the activity of common promoter regions of Arg2. HDAC inhibition with trichostatin A also decreased endothelial nitric oxide, and these effects were blunted by arginase inhibition. Nonselective class I HDAC inhibitors enhanced Arg2 expression, whereas the only selective inhibitor that increased Arg2 expression was mocetinostat, a selective inhibitor of HDACs 1 and 2. Additionally, mouse aortic rings preincubated with mocetinostat exhibited dysfunctional relaxation. Overexpression of HDAC2 (but not HDAC 1, 3, or 8) cDNA in human aortic endothelial cells suppressed Arg2 expression in a concentration-dependent manner, and siRNA knockdown of HDAC2 enhanced Arg2 expression. Chromatin immunoprecipitation indicated direct binding of HDAC2 to the Arg2 promoter, and HDAC2 overexpression in human aortic endothelial cells blocked oxidized low-density lipoprotein-mediated activation of the Arg2 promoter. Finally, overexpression of HDAC2 blocked oxidized low-density lipoprotein-mediated vascular dysfunction.

Conclusions: HDAC2 is a critical regulator of Arg2 expression and thereby endothelial nitric oxide and endothelial function. Overexpression or activation of HDAC2 represents a novel therapy for endothelial dysfunction and atherosclerosis.
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http://dx.doi.org/10.1161/ATVBAHA.114.303685DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4378272PMC
July 2014

Arginase II: atherogenesis beyond enzyme activity.

J Am Heart Assoc 2013 Aug 12;2(4):e000392. Epub 2013 Aug 12.

Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD.

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http://dx.doi.org/10.1161/JAHA.113.000392DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3828780PMC
August 2013

Nanotopography modulates mechanotransduction of stem cells and induces differentiation through focal adhesion kinase.

ACS Nano 2013 Jun 24;7(6):4785-98. Epub 2013 May 24.

Department of Bioengineering, National University of Singapore, 9 Engineering Drive 1, EA 03-12, Singapore 117576, Singapore.

Regulated biophysical cues, such as nanotopography, have been shown to be integral for tissue regeneration and embryogenesis in the stem cell niche. Tissue homeostasis involves the interaction of multipotent cells with nanoscaled topographical features in their ECM to regulate aspects of cell behavior. Synthetic nanostructures can drive specific cell differentiation, but the sensing mechanisms for nanocues remain poorly understood. Here, we report that nanotopography-induced human mesenchymal stem cell (hMSC) differentiation through cell mechanotransduction is modulated by the integrin-activated focal adhesion kinase (FAK). On nanogratings with 250 nm line width on polydimethylsiloxane, hMSCs developed aligned stress fibers and showed an upregulation of neurogenic and myogenic differentiation markers. The observed cellular focal adhesions within these cells were also significantly smaller and more elongated on the nanogratings compared to microgratings or unpatterned control. In addition, our mechanistic study confirmed that this regulation was dependent upon actomyosin contractility, suggesting a direct force-dependent mechanism. The topography-induced differentiation was observed on different ECM compositions but the response was not indicative of a direct ECM-induced hMSC differentiation pathway. FAK phosphorylation was required for topography-induced hMSC differentiation while FAK overexpression overruled the topographical cues in determining cell lineage bias. The results indicated that FAK activity had a direct impact on topography-induced gene expression, and that this effect of FAK was independent of cell shape. These findings suggest that hMSC sense and transduce nanotopographical signals through focal adhesions and actomyosin cytoskeleton contractility to induce differential gene expression.
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http://dx.doi.org/10.1021/nn304966zDOI Listing
June 2013

Frontiers in pulmonary hypertension in infants and children with bronchopulmonary dysplasia.

Pediatr Pulmonol 2012 Nov 6;47(11):1042-53. Epub 2012 Jul 6.

Eudowood Division of Pediatric Respiratory Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287-2533, USA.

Pulmonary hypertension (PH) is an increasingly recognized complication of premature birth and bronchopulmonary dysplasia (BPD), and is associated with increased morbidity and mortality. Extreme phenotypic variability exists among preterm infants of similar gestational ages, making it difficult to predict which infants are at increased risk for developing PH. Intrauterine growth retardation or drug exposures, postnatal therapy with prolonged positive pressure ventilation, cardiovascular shunts, poor postnatal lung and somatic growth, and genetic or epigenetic factors may all contribute to the development of PH in preterm infants with BPD. In addition to the variability of severity of PH, there is also qualitative variability seen in PH, such as the variable responses to vasoactive medications. To reduce the morbidity and mortality associated with PH, a multi-pronged approach is needed. First, improved screening for and increased recognition of PH may allow for earlier treatment and better clinical outcomes. Second, identification of both prenatal and postnatal risk factors for the development of PH may allow targeting of therapy and resources for those at highest risk. Third, understanding the pathophysiology of the preterm pulmonary vascular bed may help improve outcomes through recognizing pathways that are dysregulated in PH, identifying novel biomarkers, and testing novel treatments. Finally, the recognition of conditions and exposures that may exacerbate or lead to recurrent PH is needed to help with developing treatment guidelines and preventative strategies that can be used to reduce the burden of disease.
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http://dx.doi.org/10.1002/ppul.22609DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3963167PMC
November 2012

Respiratory failure secondary to human metapneumovirus requiring extracorporeal membrane oxygenation in a 32-month-old child.

Case Rep Pediatr 2012 22;2012:268074. Epub 2012 May 22.

Department of Pediatrics, Johns Hopkins Hospital, Baltimore, MD 21287, USA.

Human metapneumovirus (HMPV) is a common virus that can cause respiratory problems ranging from mild upper respiratory tract disease to respiratory failure requiring mechanical support. Here, we report a case of a 32-month-old male with a previous history of asthma, who developed respiratory failure two weeks after onset of cough and rhinorrhea and required extracorporeal membrane oxygenation (ECMO) for 9 days after failing high-frequency oscillatory ventilation (HFOV). To our knowledge, this is the oldest reported pediatric patient with respiratory failure secondary to human metapneumovirus that did not respond to mechanical ventilation. This case highlights three critical points: the potentially fatal causative role of HMPV in respiratory failure in an older pediatric age group of immunocompetent hosts, the importance of early recognition of impending respiratory failure, and the timely utilization of ECMO.
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http://dx.doi.org/10.1155/2012/268074DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3364540PMC
August 2012

Inhaled epoprostenol therapy for pulmonary hypertension: Improves oxygenation index more consistently in neonates than in older children.

Pulm Circ 2012 Jan-Mar;2(1):61-6

Department of Anesthesiology and Critical Care Medicine, Baltimore, Maryland, USA.

The purpose of this study was to determine the efficacy of inhaled epoprostenol for treatment of acute pulmonary hypertension (PH) in pediatric patients and to formulate a plan for a prospective, randomized study of pulmonary vasodilator therapy in this population. Inhaled epoprostenol is an effective treatment for pediatric PH. A retrospective chart review was conducted of all pediatric patients who received inhaled epoprostenol at a tertiary care hospital between October 2005 and August 2007. The study population was restricted to all patients under 18 years of age who received inhaled epoprostenol for greater than 1 hour and had available data for oxygenation index (OI) calculation. Arterial blood gas values and ventilator settings were collected immediately prior to epoprostenol initiation, and during epoprostenol therapy (as close to 12 hours after initiation as possible). Echocardiograms were reviewed during two time frames: Within 48 hours prior to therapy initiation and within 96 hours after initiation. Of the 20 patients in the study population, 13 were neonates, and the mean OI for these patients improved during epoprostenol administration (mean OI before and during therapy was 25.6±16.3 and 14.5±13.6, respectively, P=0.02). Mean OI for the seven patients greater than 30 days of age was not significantly different during treatment (mean OI before and during therapy was 29.6±15.0 and 25.6±17.8, P=0.56). Improvement in echocardiographic findings (evidence of decreased right-sided pressures or improved right ventricular function) was demonstrated in 20% of all patients. Inhaled epoprostenol is an effective therapy for the treatment of selected pediatric patients with acute PH. Neonates may benefit more consistently from this therapy than older infants and children. A randomized controlled trial is needed to discern the optimal role for inhaled prostanoids in the treatment of acute PH in childhood.
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http://dx.doi.org/10.4103/2045-8932.94835DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3342750PMC
August 2012