Daniel Bernstein

Stanford University, Palo Alto, California, United States

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Publications (162)925.63 Total impact

  • Journal of the American College of Cardiology 03/2015; DOI:10.1016/j.jacc.2015.03.006 · 15.34 Impact Factor
  • Circulation 03/2015; DOI:10.1161/CIR.0000000000000199 · 14.95 Impact Factor
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    Circulation 03/2015; DOI:10.1161/CIR.0000000000000190 · 14.95 Impact Factor
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    ABSTRACT: Nanoparticle-mediated sustained delivery of therapeutics is one of the highly effective and increasingly utilized applications of nanomedicine. Here, we report the development and application of a drug delivery system consisting of polyethylene glycol (PEG)-conjugated liposomal nanoparticles as an efficient in vivo delivery approach for [Pyr1]-apelin-13 polypeptide. Apelin is an adipokine that regulates a variety of biological functions including cardiac hypertrophy and hypertrophy-induced heart failure. The clinical use of apelin has been greatly impaired by its remarkably short half-life in circulation. Here, we investigate whether [Pyr1]-apelin-13 encapsulation in liposome nanocarriers, conjugated with PEG polymer on their surface, can prolong apelin stability in the blood stream and potentiate apelin beneficial effects in cardiac function. Atomic force microscopy and dynamic light scattering were used to assess the structure and size distribution of drug-laden nanoparticles. [Pyr1]-apelin-13 encapsulation in PEGylated liposomal nanocarriers resulted in sustained and extended drug release both in vitro and in vivo. Moreover, intraperitoneal injection of [Pyr1]-apelin-13 nanocarriers in a mouse model of pressure-overload induced heart failure demonstrated a sustainable long-term effect of [Pyr1]-apelin-13 in preventing cardiac dysfunction. We concluded that this engineered nanocarrier system can serve as a delivery platform for treating heart injuries through sustained bioavailability of cardioprotective therapeutics.
    Biomaterials 01/2015; 37:289-298. DOI:10.1016/j.biomaterials.2014.08.045 · 8.31 Impact Factor
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    ABSTRACT: Many children who undergo heart transplantation will survive into adulthood. We sought to examine the QOL and capacity for achievement in long-term adult survivors of pediatric heart transplantation. Adults >18 yr of age who received transplants as children (≤18 yr old) and had survived for at least 10 yr post-transplant completed two self-report questionnaires: (i) Ferrans & Powers QLI, in which life satisfaction is reported as an overall score and in four subscale domains and is then indexed from 0 (very dissatisfied) to 1 (very satisfied); and (ii) a "Metrics of Life Achievement" questionnaire regarding income, education, relationships, housing status, and access to health care. A total of 20 subjects completed the survey. The overall mean QLI score was 0.77 ± 0.16. Subjects were most satisfied in the family domain (0.84 ± 0.21) and least satisfied in the psychological/spiritual domain (0.7 ± 0.28). Satisfaction in the domains of health/functioning and socioeconomic were intermediate at 0.78 and 0.76, respectively. Most respondents had graduated from high school, reported a median annual income >$50 000/yr, and lived independently. Adult survivors of pediatric heart transplant report a good QOL and demonstrate the ability to obtain an education, work, and live independently.
    Pediatric Transplantation 11/2014; 33(4). DOI:10.1111/petr.12384 · 1.63 Impact Factor
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    ABSTRACT: The proteasome inhibitor bortezomib has been used with variable success in the treatment of AMR following heart transplant. There is limited experience with this agent as a pretransplant desensitizing therapy. We report a case of successful HLA desensitization with a bortezomib-based protocol prior to successful heart transplantation. A nine-yr-old boy with dilated cardiomyopathy, not initially sensitized to HLA (cPRA of zero), required three days of ECMO, followed by implantation of a Heartmate II LVAD. Within six wk, the patient developed de novo class I IgG and C1q complement-fixing HLA antibodies with a cPRA of 100%. Two doses of IVIG (2 g/kg) failed to reduce antibody levels, although two courses of a novel desensitization protocol consisting of rituximab (375 mg/m(2) ), bortezomib (1.3 mg/m(2) × 5 doses), and plasmapheresis reduced his cPRA to 0% and 87% by the C1q and IgG assays, respectively. He underwent heart transplantation nearly two months later. The patient is now >one yr post-transplant, is free of both AMR and ACR, and has no detectable donor-specific antibodies by IgG or C1q. Proteasome inhibition with bortezomib and plasmapheresis may be an effective therapy for HLA desensitization pretransplant.
    Pediatric Transplantation 09/2014; 18(8). DOI:10.1111/petr.12347 · 1.63 Impact Factor
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    ABSTRACT: The role of long noncoding RNA (lncRNA) in adult hearts is unknown; also unclear is how lncRNA modulates nucleosome remodelling. An estimated 70% of mouse genes undergo antisense transcription, including myosin heavy chain 7 (Myh7), which encodes molecular motor proteins for heart contraction. Here we identify a cluster of lncRNA transcripts from Myh7 loci and demonstrate a new lncRNA-chromatin mechanism for heart failure. In mice, these transcripts, which we named myosin heavy-chain-associated RNA transcripts (Myheart, or Mhrt), are cardiac-specific and abundant in adult hearts. Pathological stress activates the Brg1-Hdac-Parp chromatin repressor complex to inhibit Mhrt transcription in the heart. Such stress-induced Mhrt repression is essential for cardiomyopathy to develop: restoring Mhrt to the pre-stress level protects the heart from hypertrophy and failure. Mhrt antagonizes the function of Brg1, a chromatin-remodelling factor that is activated by stress to trigger aberrant gene expression and cardiac myopathy. Mhrt prevents Brg1 from recognizing its genomic DNA targets, thus inhibiting chromatin targeting and gene regulation by Brg1. It does so by binding to the helicase domain of Brg1, a domain that is crucial for tethering Brg1 to chromatinized DNA targets. Brg1 helicase has dual nucleic-acid-binding specificities: it is capable of binding lncRNA (Mhrt) and chromatinized-but not naked-DNA. This dual-binding feature of helicase enables a competitive inhibition mechanism by which Mhrt sequesters Brg1 from its genomic DNA targets to prevent chromatin remodelling. A Mhrt-Brg1 feedback circuit is thus crucial for heart function. Human MHRT also originates from MYH7 loci and is repressed in various types of myopathic hearts, suggesting a conserved lncRNA mechanism in human cardiomyopathy. Our studies identify a cardioprotective lncRNA, define a new targeting mechanism for ATP-dependent chromatin-remodelling factors, and establish a new paradigm for lncRNA-chromatin interaction.
    Nature 08/2014; 514(7520). DOI:10.1038/nature13596 · 42.35 Impact Factor
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    ABSTRACT: Monitoring allograft health is an important component of posttransplant therapy. Endomyocardial biopsy is the current gold standard for cardiac allograft monitoring but is an expensive and invasive procedure. Proof of principle of a universal, noninvasive diagnostic method based on high-throughput screening of circulating cell-free donor-derived DNA (cfdDNA) was recently demonstrated in a small retrospective cohort. We present the results of a prospective cohort study (65 patients, 565 samples) that tested the utility of cfdDNA in measuring acute rejection after heart transplantation. Circulating cell-free DNA was purified from plasma and sequenced (mean depth, 1.2 giga-base pairs) to quantify the fraction of cfdDNA. Through a comparison with endomyocardial biopsy results, we demonstrate that cfdDNA enables diagnosis of acute rejection after heart transplantation, with an area under the receiver operating characteristic curve of 0.83 and sensitivity and specificity that are comparable to the intrinsic performance of the biopsy itself. This noninvasive genome transplant dynamics approach is a powerful and informative method for routine monitoring of allograft health without incurring the risk, discomfort, and expense of an invasive biopsy.
    Science translational medicine 06/2014; 6(241):241ra77. DOI:10.1126/scitranslmed.3007803 · 14.41 Impact Factor
  • 04/2014; 5(3):193-197. DOI:10.4161/bioe.27751
  • The Journal of Heart and Lung Transplantation 04/2014; 33(4):S84-S85. DOI:10.1016/j.healun.2014.01.261 · 5.61 Impact Factor
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    ABSTRACT: Due to the limited self-renewal capacity of cardiomyocytes, the mammalian heart exhibits impaired regeneration and insufficient ability to restore heart function after injury. Cardiovascular tissue engineering is currently considered as a promising alternative therapy to restore the structure and function of the failing heart. Recent evidences suggest that the epicardium may play critical roles in regulation of myocardial development and regeneration. One of the mechanisms has been proposed for the restorative effect of the epicardium is the specific physiomechanical cues that this layer provides to the cardiac cells. In this article we explore whether a new generation of epicardium-mimicking, acellular matrices can be utilized to enhance cardiac healing after injury. The matrix consists of a dense collagen scaffold, with optimized biomechanical properties approaching those of embryonic epicardium. Grafting the epicardial patch onto the ischemic myocardium, promptly post the incidence of infarct, resulted in preserved contractility, attenuated ventricular remodeling, diminished fibrosis, and vascularization within the injured tissue in the adult murine heart.
    01/2014; 5(3).
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    ABSTRACT: Earlier studies have indicated that the pharmacokinetics of mycophenolic acid (MPA) is influenced by polymorphisms of ABCC2, which encodes for the membrane transporter MRP2. The ABCC2 rs717620 A allele has been associated with enterohepatic recirculation of MPA, and our previous work had correlated the discontinuance of MPA with this allele in pediatric heart transplant patients. Therefore, we hypothesized that the ABCC2 rs717620 A allele would be associated with poorer outcomes including rejection with hemodynamic compromise (RHC), graft failure, and death in the pediatric heart transplant (PHTx) population receiving MPA. PHTx recipients from 6 institutions in the Pediatric Heart Transplantation Study (PHTS) from the period of 1993-2009, receiving MPA therapy, were genotyped for ABCC2 rs717620. Genotyping was accomplished by direct sequencing. Demographic and outcome data were limited to the data routinely collected as part of the PHTS and included RHC and mortality. Two hundred ninety patients were identified who received MPA at some point post transplantation, of which 200 carried the GG genotype, 81 carried the AG genotype, and 9 carried the AA genotype. Follow-up time after transplantation was 6 years. RHC occurred in 76 patients and 18 patients died. In the 281 patients followed up more than 1 year, late RHC (>1 year post transplantation) occurred in 42 patients. While both RHC and late RHC were associated with the ABCC2 rs717620 GG genotype (hazard ratios: 1.80 and 4.57, respectively, p<0.05) in all patients, this association was not significant in PHTx patients receiving only MPA as the antiproliferative agent from the time of transplant (n=142). ABCC2 rs717620 polymorphisms varied within racial groups. As a candidate gene assessment, the ABCC2 rs717620 AG and AA genotypes may be associated with improved, rather than poorer, RHC in PHTx patients receiving MPA therapy. ABCC2 rs717620 polymorphisms should be included in any expanded pharmacogenomic analysis of outcomes after pediatric heart transplantation.
    01/2014; 19(1):16-24. DOI:10.5863/1551-6776-19.1.16
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    ABSTRACT: There are few substantive methods to measure the health of the immune system, and the connection between immune strength and the viral component of the microbiome is poorly understood. Organ transplant recipients are treated with posttransplant therapies that combine immunosuppressive and antiviral drugs, offering a window into the effects of immune modulation on the virome. We used sequencing of cell-free DNA in plasma to investigate drug-virome interactions in a cohort of organ transplant recipients (656 samples, 96 patients) and find that antivirals and immunosuppressants strongly affect the structure of the virome in plasma. We observe marked virome compositional dynamics at the onset of the therapy and find that the total viral load increases with immunosuppression, whereas the bacterial component of the microbiome remains largely unaffected. The data provide insight into the relationship between the human virome, the state of the immune system, and the effects of pharmacological treatment and offer a potential application of the virome state to predict immunocompetence.
    Cell 11/2013; 155(5):1178-1187. DOI:10.1016/j.cell.2013.10.034 · 33.12 Impact Factor
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    ABSTRACT: HC is a rare cause of congestive heart failure that typically presents with malignant ventricular arrhythmias in infants, often requiring urgent intervention. Successful heart transplantation in a patient with HC has only been reported once (J Heart Lung Transplant 2004: 23: 902). The combination of HC with concurrent LVNC has only been described three times (Int J Legal Med 2009: 123: 47; Hum Pathol 2005: 36: 403; Pediatr Dev Pathol 2012: 15: 397). We report two rare cases of HC with LVNC in two infants presenting with cardiogenic shock, one requiring ECMO support who was successfully bridged to orthotopic heart transplantation with a Berlin Heart LVAD.
    Pediatric Transplantation 11/2013; 17(7):E165-E167. DOI:10.1111/petr.12141 · 1.63 Impact Factor
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    ABSTRACT: Regeneration of the damaged myocardium is one of the most challenging fronts in the field of tissue engineering due to the limited capacity of adult heart tissue to heal and to the mechanical and structural constraints of the cardiac tissue. In this study we demonstrate that an engineered acellular scaffold comprising type I collagen, endowed with specific physiomechanical properties, improves cardiac function when used as a cardiac patch following myocardial infarction. Patches were grafted onto the infarcted myocardium in adult murine hearts immediately after ligation of left anterior descending artery and the physiological outcomes were monitored by echocardiography, and by hemodynamic and histological analyses four weeks post infarction. In comparison to infarcted hearts with no treatment, hearts bearing patches preserved contractility and significantly protected the cardiac tissue from injury at the anatomical and functional levels. This improvement was accompanied by attenuated left ventricular remodeling, diminished fibrosis, and formation of a network of interconnected blood vessels within the infarct. Histological and immunostaining confirmed integration of the patch with native cardiac cells including fibroblasts, smooth muscle cells, epicardial cells, and immature cardiomyocytes. In summary, an acellular biomaterial with specific biomechanical properties promotes the endogenous capacity of the infarcted myocardium to attenuate remodeling and improve heart function following myocardial infarction.
    Biomaterials 08/2013; 34(36). DOI:10.1016/j.biomaterials.2013.08.017 · 8.31 Impact Factor
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    ABSTRACT: Aims Beta adrenergic receptor (β-AR) subtypes act through diverse signaling cascades to modulate cardiac function and remodeling. Previous in vitro studies suggest that β1-AR signaling is cardiotoxic whereas β2-AR signaling is cardioprotective, and may be the case during ischemia/reperfusion in vivo. The objective of this study was to assess whether β2-ARs also played a cardioprotective role in the pathogenesis of non-ischemic forms of cardiomyopathy. Methods and Results To dissect the role of β1 vs β2-ARs in modulating MLP (Muscle LIM Protein) cardiomyopathy, we crossbred MLP-/- with β1-/- or β2-/- mice. Deletion of the β2-AR improved survival, cardiac function, exercise capacity and myocyte shortening; in contrast haploinsufficency of the β1-AR reduced survival. Pathologic changes in Ca(2+) handling were reversed in the absence of β2-ARs: peak Ca(2+) and SR Ca(2+) were decreased in MLP-/- and β1+/-/MLP-/- but restored in β2-/-MLP-/-. These changes were associated with reversal of alterations in troponin I and phospholamban phosphorylation. Gi inhibition increased peak and baseline Ca(2+), recapitulating changes observed in the β2-/-/MLP-/-. The L-type Ca(2+)blocker verapamil significantly decreased cardiac function in β2-/-MLP-/- vs WT. We next tested if the protective effects of β2-AR ablation were unique to the MLP model using TAC-induced heart failure. Similar to MLP, β2-/- mice demonstrated delayed progression of heart failure with restoration of myocyte shortening and peak Ca(2+) and Ca(2+) release. Deletion of β2-ARs prevents the development of MLP-/- cardiomyopathy via positive modulation of Ca(2+) due to removal of inhibitory Gi signaling and increased phosphorylation of troponin I and phospholamban. Similar effects were seen after TAC. Unlike previous models where β2-ARs were found to be cardioprotective, in these two models, β2-AR signaling appears to be deleterious, potentially through negative regulation of Ca(2+) dynamics.
    Journal of Molecular and Cellular Cardiology 08/2013; 63. DOI:10.1016/j.yjmcc.2013.07.016 · 5.22 Impact Factor
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    ABSTRACT: Dysfunctional bone morphogenetic protein receptor-2 (BMPR2) signaling is implicated in the pathogenesis of pulmonary arterial hypertension (PAH). We used a transcriptional high-throughput luciferase reporter assay to screen 3,756 FDA-approved drugs and bioactive compounds for induction of BMPR2 signaling. The best response was achieved with FK506 (tacrolimus), via a dual mechanism of action as a calcineurin inhibitor that also binds FK-binding protein-12 (FKBP12), a repressor of BMP signaling. FK506 released FKBP12 from type I receptors activin receptor-like kinase 1 (ALK1), ALK2, and ALK3 and activated downstream SMAD1/5 and MAPK signaling and ID1 gene regulation in a manner superior to the calcineurin inhibitor cyclosporine and the FKBP12 ligand rapamycin. In pulmonary artery endothelial cells (ECs) from patients with idiopathic PAH, low-dose FK506 reversed dysfunctional BMPR2 signaling. In mice with conditional Bmpr2 deletion in ECs, low-dose FK506 prevented exaggerated chronic hypoxic PAH associated with induction of EC targets of BMP signaling, such as apelin. Low-dose FK506 also reversed severe PAH in rats with medial hypertrophy following monocrotaline and in rats with neointima formation following VEGF receptor blockade and chronic hypoxia. Our studies indicate that low-dose FK506 could be useful in the treatment of PAH.
    The Journal of clinical investigation 07/2013; DOI:10.1172/JCI65592 · 13.77 Impact Factor
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    ABSTRACT: The relationship between SES and outcomes surrounding pediatric cardiac transplantation is complex and influenced by recipient race. Broad-based studies of SES have not been performed. A retrospective review of all 5125 primary pediatric heart transplants performed in the United States between 2000 and 2011. Patients were stratified by SES based on zip code of residence and U.S. census data (low SES: 1637; mid-SES: 2253; high SES: 1235). Survival following listing and transplantation was compared across strata. Risk-adjusted long-term mortality on the waitlist was higher among low SES patients (hazard 1.32, CI 1.07-1.63). The relationship between SES and outcomes varied by race. Early risk-adjusted post-transplant outcomes were worst among high SES patients (10.8% vs. low SES: 8.9%, p < 0.05). The incidence of non-compliance was higher among low SES patients (p < 0.0001). Long-term risk-adjusted patient survival was poorer among low (hazard 1.41, CI 1.10-1.80) and mid-SES (1.29, 1.04-1.59) groups. Low SES is associated with worse outcomes on both the waitlist and late following transplantation. Higher SES patients had more complex transplants with higher early mortality. Further research should be directed at identifying and addressing underlying causal factors for these disparities.
    Pediatric Transplantation 07/2013; DOI:10.1111/petr.12117 · 1.63 Impact Factor
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    ABSTRACT: Background: Alterations in the ubiquitin-proteasome system (UPS) have been described in left ventricular hypertrophy and failure, although results have been inconsistent. The role of the UPS in right ventricular hypertrophy (RVH) and failure (RVF) is unknown. Given the greater percent increase in RV mass associated with RV afterload stress, as present in many congenital heart lesions, we hypothesized that alterations in the UPS could play an important role in RVH/RVF. Methods and Results: UPS expression and activity were measured in the RV from mice with RVH/RVF secondary to pulmonary artery constriction (PAC). Epoxomicin and MG132 were used to inhibit the proteasome, and overexpression of the 11S PA28α subunit was used to activate the proteasome. PAC mice developed RVH (109.3% increase in RV weight to body weight, RVW/BW), RV dilation with septal shift, RV dysfunction and clinical RVF. Proteasomal function (26S β5 chymotrypsin-like activity) was decreased 26% (p<0.05). Protein expression of 19S subunit Rpt5 (p<0.05), UCHL1 deubiquitinase (p<0.0001), and Smurf1 E3 ubiquitin ligase (p<0.01) were increased, as were polyubiquitinated proteins (p<0.05) and free-ubiquitins (p=0.05). Pro-apoptotic Bax was increased (p<0.0001), while anti-apoptotic Bcl-2 decreased (p<0.05) resulting in a 6-fold increase in Bax/Bcl-2 ratio. Proteasomal inhibition did not accelerate RVF. However, proteasome enhancement by cardiac-specific proteasome overexpression partially improved survival. Conclusions: Proteasome activity is decreased in RVH/RVF, associated with upregulation of key UPS regulators and pro-apoptotic signaling. Enhancement of proteasome function partially attenuates RVF suggesting that UPS dysfunction contributes to RVF.
    AJP Heart and Circulatory Physiology 05/2013; DOI:10.1152/ajpheart.00771.2012 · 4.01 Impact Factor
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    ABSTRACT: Pulmonary insufficiency (PI) is a common long-term sequel after repair of tetralogy of Fallot, causing progressive right ventricular (RV) dilation and failure. We describe the physiologic and molecular characteristics of the first murine model of RV volume overload. Methods: PI was created by entrapping the pulmonary valve leaflets with sutures. Imaging, catheterization and exercise testing were performed at 1, 3 and 6 months and compared to sham controls. RNA from the RV free wall was hybridized to Agilent whole-genome oligonucleotide microarrays. Results: Volume overload resulted in RV enlargement, decreased RV outflow tract shortening fraction at 1 month followed by normalization at 3 and 6 months (39±2, 44±2 and 41±2 vs. 46±3% in sham), early reversal of E/A ratio followed by pseudonormalization (0.87±0.08, 0.82±0.08 and 0.96±0.08 vs. 1.04±0.03, p<0.05), elevated end diastolic pressure (7.6±0.7, 6.9±0.8 and 7±0.5 vs. 2.7±0.2mmHg, p<0.05) and decreased exercise duration (26±0.4, 26±1 and 22±1.3 vs. 30±1.1 min, p<0.05). Subendocardial RV fibrosis was evident by 1 month. At 1 month, 372 genes were significantly downregulated. Mitochondrial pathways and G-protein coupled receptor signaling were the most represented categories. At 3 months, 434 genes were upregulated and 307 downregulated. While many of the same pathways continued to be downregulated, TNF-α, TGF-β1, p53-signaling, and extracellular matrix (ECM) remodeling transitioned from down- to upregulated. Conclusions: We describe a novel murine model of chronic RV volume overload recapitulating aspects of the clinical disease with gene expression changes suggesting early mitochondrial bioenergetic dysfunction, enhanced TGF-β signaling, ECM remodeling and apoptosis.
    AJP Heart and Circulatory Physiology 03/2013; 304(10). DOI:10.1152/ajpheart.00776.2012 · 4.01 Impact Factor

Publication Stats

4k Citations
925.63 Total Impact Points

Institutions

  • 1992–2015
    • Stanford University
      • • Department of Pediatrics
      • • Division of Pediatric Cardiology
      • • Department of Pathology
      Palo Alto, California, United States
  • 2013
    • University of Texas at Dallas
      Richardson, Texas, United States
  • 2010–2013
    • Lucile Packard Children’s Hospital at Stanford
      Palo Alto, California, United States
  • 1992–2012
    • Stanford Medicine
      • • Department of Medicine
      • • Department of Pediatrics
      • • Division of Pediatric Cardiology
      Stanford, California, United States
  • 1997–2011
    • University of Pittsburgh
      • • Department of Pathology
      • • Department of Pediatrics
      Pittsburgh, PA, United States
  • 2003–2005
    • University of Toronto
      • Department of Laboratory Medicine and Pathobiology
      Toronto, Ontario, Canada