Tissue-specific transgene regulation for studies of molecular pathophysiology

Our leadership in exploiting conditional cardiovascular tissue-specific gene regulation as a research tool for mechanistic studies in mouse models in vivo is based on our early development of transgenic mice possessing arterial SMC-restricted expression of a tetracycline-responsive transcriptional activator (tTA) and our use of this system to conditionally express a variety of tTA-dependent transgenes in vivo (Myb-Engrailed: a dominant negative Myb; PMCA1a; and PMCA4b).  We characterized the function of the tTA system in a wire-mediated denudation model of carotid artery injury and used this model to gauge the physiological importance of transgenes of interest.  Upon breeding our conditional transactivation system into LDL receptor knockout mice (LDLr-/-) we discovered that the transgenic line had undergone silencing.  We are currently redesigning the transgenic constructs to insulate them against possible silencing and hope to generate new mice in which we will study the effects of our transgenes of interest in cholesterol-mediated atherogenesis.  Prior to their silencing event, Myb-Engrailed over-expressing animal were shown to be protected from the neointima formation that follows arterial injury in control animals. PMCA4b over-expressing animals were also protected in such a model, but showed an additional phenotype which became a major focus of our research.  Namely, PMCA4b over-expression in arterial SMC resulted in a unique model of increased blood pressure, which is associated with enhanced myogenic tone and increased sensitivity to endogenous vasoconstrictors.  We showed this to be due to heightened pharmaco-mechanical coupling of SMC contraction caused by compensatory increases in the storage of intracellular Ca2+, and decreased activity of neuronal nitric oxide synthase (nNOS) which has been shown to be both structurally and functionally coupled with PMCA4b.  These two mechanisms are not mutually exclusive and both require definition.

Collaborative studies of genetic and experimental models of cardiovascular disease

We have been very active in a number of collaborative projects employing our mouse models of injury and tissue-specific conditional gene expression for other transgenes of interest.  These include Elafin, an elastase inhibitor, and Chymase, an endogenous matrix and zymogen protease (Marlene Rabinovitch, Stanford University), and iNOS and Endothelin (Duncan Stewart, University of Ottawa). The latter two genes have also been expressed in a conditional cardiac-restricted pattern. The cardiac iNOS over-expressing mouse represents a unique model of sudden cardiac death due to a particular propensity of the mouse AV conduction system for iNOS-derived peroxynitrite and/or superoxide.  The cardiac Endothelin over-expressing animal is a fascinating model of immune cardiomyopathy resulting in heart failure. Both the iNOS and Endothelin projects were parts of HSFO and CIHR grants from Duncan Stewart (University of Ottawa) and I, and these models remain an area of our collaborative research. For example, in collaboration with Kumarswamy Nanthakumar (University of Toronto) we are employing intracardiac and epicardial mapping of the murine heart to study the temporal and molecular basis of electrophysiological remodeling in the ET-1 model of heart failure. Other collaborations in which we began by characterizing the cardiovascular phenotypes of other genetically engineered mice have revealed unique models of diastolic cardiac dysfunction and cardiac hypertrophy (GLP-1R knockout; Dan Drucker, University of Toronto) and vasomotor dysfunction leading to arteriovenous malformations (Endoglin knockout; Michelle Letarte, University of Toronto). Our interest in GLP-1R biology in particular has led to a new highly active HSFO-funded research program on the cardiovascular effects of incretins. This work has stimulated our interest in characterizing other cellular and molecular events that accompany both ventricular and vascular remodeling after myocardial infarction.  To this end, we have recently described an intriguing multifaceted failure of cell survival, arteriogenesis and fibrosis following myocardial infarction in mice lacking the bone morphogenic protein, growth differentiation factor-5 (GDF-5). The significance of this work is the potential that GDF5 will improve post-MI repair.  Finally, we have two more projects underway with translational promise. First, in collaboration with Steffen-Sebastian bolz (University of Toronto), we have discovered a novel molecular mechanism underlying the increased peripheral vascular resistance that complicates heart failure. The targets identified by this work are now worthy of testing in vivo. Second, our new HSFO-funded grant on PMCA biology will allow us to elucidate the mechanisms for salutary effects of cardiac-specific over-expression of hPMCA4b in the mouse heart.

Clinical and experimental cardiovascular imaging

As a board-certified Nuclear Cardiologist and member of the Department of Medical Imaging at my base hospital (University Health Network), I work closely with Robert Mark Iwanochko and Douglas Lee (University of Toronto), to study the role of 99mTc and/or 201Thal myocardial perfusion imaging with Single Photon Emission Computed Tomography (SPECT) in the diagnosis and prognosis of coronary artery disease.  In collaboration with Ren-Ke Li and Richard Weisel (University of Toronto), we have employed SPECT to gauge the viability and function of autologous cardiac cell transplants in a pig model of myocardial infarction.  In collaboration with David Jaffray and Steffen-Sebastian Bolz (University of Toronto), we have developed protocols for magnetic resonance (MR)-based measurements of cerebral blood flow in animals models of heart failure and are correlating these with vasomotor physiology of explanted cerebral arteries.

Acute cardiac care

As an attending cardiologist in the Coronary Intensive Care Unit of the Toronto General Hospital, I was the local PI for the CURE trial (multicentre randomized placebo-controlled clinical trial of Clopidogrel in unstable angina), and for the Canadian Heart Research Centre’s Registry of Acute Coronary Syndromes.  We have also studied the role of acute physiological scoring systems in the prognosis and management of patients requiring cardiac intensive care.  Currently, my burgeoning interest in the role of incretins in cardiovascular physiology will be exemplified by a UofT-led Phase II randomized controlled double blinded study of a GLP-1 analogue in acute myocardial infarction. I have worked closely with my colleague Vladimir Dzavik (University of Toronto) to attract industry funding for this investigator-initiated trial.

Graduate Students

Dhanwantee Mundil, M.Sc. Candidate with intent to transfer to PhD

Project focus: “Studies of GLP-1 in cardiac health and disease”

Hussein Butt, MSc. Candidate

Project focus: “Is IQGAP a calcium-sensitive modulator of cell cycle in vascular smooth muscle cells?”

Aki Shikantani, PhD Candidate

Project focus: “Differentiating vascular and hematopoietic roles of c-myb in mouse models of vascular and cardiac disease”

Postdoctoral Fellows

Omar El-Mounayri, Postdoctoral Fellow,

Project focus: “Derivation of distinct and pure populations of contractile smooth muscle cells from human stem cells”

Sarah Steinbach, Postdoctoral Fellow,

Project focus: “Differentiation of skin-derived progenitors into vascular smooth muscle cells: diagnostic and therapeutic implications”

Masayoshi Ishida, Postdoctoral Fellow,

Project focus: “Cardiac regenerative potential of bioreactor-derived progenitors”

Technicians and Associates

Talat Afroze

Mohammed Hossein Noyan-Ashraf

Abdul Momen

Haiyan Xiao

Contact Information

101 College Street MaRS 3-910

Toronto, ON M5G 1L7

Research Administration: 416-581-7489

Lab Phone: 416-581-7491 or 416-581-7647

Selected Publications

1. - Senior Responsible Author. Zaidi SHE, Huang Q, Momen A, Riazi A, Husain M. Growth Differentiation Factor 5 (Bone Morphogenetic Protein 14) regulates cardiac repair after myocardial infarction. Journal of American College of Cardiology 2009 Jan; 55 (2):135-143.
2. - Senior Responsible Author. Kolodziejska KM, Noyan Ashraf H, Nagy A, Bacon A, Frampton J, Xin H, Kotlikoff MI, Husain M. c-Myb-dependent smooth muscle cell differentiation. Circ. Res. 2008; 102(5): 554-61. (Trainee publication, Supervisor of Kolodziejska, Noyan Ashraf).
3. - Senior Responsible Author. Ban K, Noyan-Ashraf MH, Hoefer J, Bolz SS, Drucker DJ, Husain M. Cardioprotective and vasodilatory actions of GLP-1 are mediated through both GLP-1 receptor-dependent and independent pathways. Circulation 2008; 117(18): 2340-50. (Trainee publication, Supervisor of Ban, Noyan Ashraf, Hoefer).
4. - Senior Responsible Author. Choi J, Chiang A, Taulier N, Gros R, Pirani A, Husain M. A Calmodulin-binding site on Cyclin E mediates Ca2+-sensitive G1/S transitions in vascular smooth muscle cells. Circ. Res. 2006; 98:1273-1281 with accompanying Editorial: 1240-3. (Trainee publication, Supervisor of Choi, Chiang, Gros, Pirani).
5. - Senior Responsible Author. Yang L, Kabir G, Gros R, El-Moselhi A, Husain M, Stewart D. Conditional cardiac-specific over-expression of ET-1 in transgenic mice results in an inflammatory cardiomyopathy and heart failure. Circulation 2004; 109(2): 255-261. (Trainee publication, Corresponding and Co-Senior Author, Supervisor of Yang, Kabir, Gros, El-Moselhi). Publications in the last 3 years
6. - Senior Responsible Author. Hoefer J, Azam MA, Poi HL, Momen MA, Scherer EQ, Meissner A, Bolz SS, Husain M. Spingosine-1-phosphate-dependent activation of p38 AMPK maintains elevated peripheral resistance in heart failure. Circ Res. 2010 Oct 1;107(7):923-33. Epub 2010 Jul 29. (Trainee publication, Supervisor of Hoefer, Azam).
7. - Collaborator. Caruso L, Yeun S, Smith J, Husain M, Opavsky MA. Cardiomyocyte-targeted overexpression of the coxsackie-adenovirus receptor causes a cardiomyopathy in association with b-catenin signaling. Journal of Molecular and Cellular Cardiology; June 2010 48(6); 1194-1205.
8. - Senior Responsible Author. Ban K, Kim KH, Cho CK, Sauvé M, Diamandis EP, Backx PH, Drucker DJ, Husain M. GLP-1 (9-36) amide-mediated cytoprotection is blocked by exendin (9-39) yet does not require the known GLP-1 receptor. Endocrinology 2010; 151(4):1520-31 (Trainee publication, Supervisor of Ban).
9. - Senior Responsible Author. Sauvé M, Ban K, Momen MA, Zhou YQ, Henkelman RM, Husain M, Drucker DJ. Genetic deletion or pharmacological inhibition of dipeptidyl peptidase-4 improves cardiovascular outcomes following myocardial infarction in mice. Diabetes 2010 Apr; 59(4):1063-73 (Trainee publication, Supervisor of Ban).
10. - Collaborator. Toporsian M, Jerkic M, Zhou YQ, Kabir MG, Yu LX, McIntyre BA, Davis A, Wang YJ, Stewart DJ, Belik J, Husain M, Henkelman M, Letarte M. Spontaneous adult-onset pulmonary arterial hypertension attributable to increased endothelial oxidative stress in a murine model of Hereditary Hemorrhagic Telangiectasia. Arterioscler Throm Vasc Biol. 2010 Mar; 30(3):509-17.
11. - Collaborator. Niebruegge S, Bauwens CL, Peerani R, Thavandiran N, Masse S, Sevaptisidis E, Nanthakumar K, Woodhouse K, Husain M, Kumacheva E, Zandstra PW. Generation of human embryonic stem cell-derived mesoderm and cardiac cells using size-specified aggregates in an oxygen controlled bioreactor. Biotech. & Bioeng. 2009; 102(2): 493-507. (Trainee publication, Co-Supervisor of Niebruegge).
12. - Collaborator. dos Santos CC, Gattas DJ, Tsoporis JN, Kabir MG, Slutsky AS, Husain M, Sibbald W, Parker TG. Sepsis-induced myocardial depression is associated with transcriptional changes in energy metabolism and contractile related genes: a physiological and gene expression based approach. Crit Care Med. 2010 Mar;38(3):894-902. (Trainee publication, Co-Supervisor of dos Santos, Gattas).
13. - Senior Responsible Author. Zaidi SHE, Huang Q, Momen A, Riazi A, Husain M. Growth Differentiation Factor 5 (Bone Morphogenetic Protein 14) regulates cardiac repair after myocardial infarction. Journal of American College of Cardiology 2009 Jan; 55 (2):135-143.
14. - Senior Responsible Author. Noyan-Ashraf MH, Momen MA, Ban K, Sadi AM, Zhou YQ, Riazi AM, Baggio LL, Henkelman RM, Husain M, Drucker DJ. The GLP-1R agonist liraglutide activates cytoprotective pathways and improves outcomes following experimental myocardial infarction in mice. Diabetes 2009 Apr;58(4):975-83. Epub 2009 Jan 16. (Trainee publication, Co-Senior Author, Supervisor of Noyan-Ashraf, Ban, Sadi).
15. - Senior Responsible Author. Ban K, Noyan-Ashraf MH, Hoefer J, Bolz SS, Drucker DJ, Husain M. Cardioprotective and vasodilatory actions of GLP-1 are mediated through both GLP-1 receptor-dependent and independent pathways. Circulation 2008; 117(18): 2340-50. (Trainee publication, Supervisor of Ban, Noyan Ashraf, Hoefer).
16. - Senior Responsible Author. Kolodziejska KM, Noyan Ashraf H, Nagy A, Bacon A, Frampton J, Xin H, Kotlikoff MI, Husain M. c-Myb-dependent smooth muscle cell differentiation. Circ. Res. 2008; 102(5): 554-61. (Trainee publication, Supervisor of Kolodziejska, Noyan Ashraf).
17. - Senior Responsible Author. Handa S, Sadi MA, Cybulsky MI, Stewart DJ, Husain M. Region-specific patterns of vascular remodeling occur early in atherosclerosis and without loss of smooth muscle cell markers. Atherosclerosis 2008; 196(2): 617-623. (Trainee publication, Supervisor of Handa, Sadi).
18. - Collaborator. Bauwens CL, Peerani R, Niebruegge S, Woodhouse KA, Kumacheva E, Husain M, Zandstra PW. Control of Human Embryonic Stem Cell Colony and Aggregate Size Heterogeneity Influences Differentiation Trajectories. Stem Cells 2008; 26(9): 2300-10. (Trainee publication, Co-Supervisor of Niebruegge).
19. - Collaborator. Umapathy K, Masse S, Kolodziejska K, Veenhuyzen GD, Chauhan VS, Husain M, Farid T, Downar E, Sevaptsidis E, Nanthakumar K. Electrogram fractionation in murine HL-1 atrial monolayer model. Heart Rhythm 2008; 5(7): 1029-1025. (Trainee publication, Supervisor of Kolodziejska).
20. - Collaborator. Chalmers J, Lin SY, Martino T, Arab S, Liu P, Husain M, Sole M, Belsham D. Diurnal Profiling of Neuroendocrine Genes in Murine Heart, and Shift in Proopiomelanocortin Gene Expression with Pressure-Overload Cardiac Hypertrophy. J. Mol. Endocrinol. 2008; 41(3): 117-24.