Vesalius Research Center (VRC) , VIB3

Gene Transfer & Cell for Cardiology Group

Stefan Janssens, M.D, Ph.D. Principal Investigator Tel. +32-16-346182 Fax. +32-16-345990 E-mail: stefan.janssens@med.kuleuven.be

Affiliations & Appointments

- Head of Clinic, Department of Cardiology, University Hospital Gasthuisberg,KU-Leuven
- University of Leuven, Professor of Medicine
- Clinical investigator FWO-Flanders (50%)
- Deputy editor European Heart Journal

Research Topics

PRECLINICAL STUDIES IN MURINE AND PORCINE MODELS OF MYOCARDIAL INFARCTION, AND PULMONARY HYPERTENSION

The common focus in these studies is the role of Nitric Oxide (NO)/cGMP signaling in ventricular remodeling following myocardial infarction and in pulmonary hypertension. Nitric oxide (NO) is an important messenger molecule in blood vessels and mediates vasorelaxation, decreases smooth muscle cell proliferation, migration and extracellular matrix production, inhibits platelet aggregation and adhesion, and stimulates endothelial cell proliferation. Nitric oxide acts, in part, by binding to a soluble guanylate cyclase receptor, a heterodimer composed of alpha and beta subunits, which converts guanosine triphosphate (GTP) to cyclic guanosine monophosphate (cGMP) leading to activation of cGMP-dependent protein kinases (PKG). Nitric oxide is also produced by cardiomyocytes and modulates cardiac function through actions on inotropic and lusitropic state, b-adrenergic responsiveness and excitation–contraction coupling. We will investigate the role of NO/cGMP in pulmonary vascular remodeling and in right and left ventricular remodeling following pressure and volume overload using different transgenic approaches (transgenic mice with cardiomyocyte- or smooth muscle cell-specific modulated expression of components of the NO/cGMP signaling cascade) and using progenitor cells, genetically engineered to overexpress NO synthase.

Specific aims Short term (2005-2006):

Myocardial infarction studies in pigs and mice:

• To assess the mechanisms whereby regional myocardial NOS gene transfer in the ischemic porcine heart reduces ischemia reperfusion injury and to explore whether or not these effects can be mimicked by NO inhalation.
• To assess the mechanisms whereby NO modulates LV remodeling following myocardial infarction in mice with conditional cardiac-restricted expression of a dominant negative sGCalpha mutant.

  
  Pulmonary hypertension studies in mice:

• To evaluate the role of NO in systemic and pulmonary vasorelaxation in transgenic mice with inactivated soluble guanylate cyclase gene function (deletion exon 6 sGC alpha1) (collaboration P. Brouckaert, VIB Gent)
• To evaluate the role of NO in hypoxic pulmonary vascular remodeling in transgenic mice with inactivated soluble guanylate cyclase gene function (deletion exon 6 sGC alpha1)
• To characterize the duration and distribution of intrapulmonary transgene expression using new adeno-associated viral vectors (collaboration Drs. T. Vandendriessche and M. Chuah, VRC).
• To investigate the regulation of epoxygenase gene function in mice exposed to acute and chronic hypoxia and to explore whether pharmacological or gene transfer interventions may augment the effects of NO.

Longer term (2006-2007)

Progenitor Cell transfer studies.
Experimental data in infarcted rodent hearts have suggested that circulating mouse bone marrow stem cells can incorporate into the damaged heart and adapt a cardiomyocyte- or endothelial cell-like phenotype. Direct injection of endothelial progenitor cells in border zones of infarcted myocardium may induce vascular cell formation and improve cardiac function. More recently, multipotent adult progenitor cells (MAPCs) have been shown to adopt an endothelial-like phenotype but whether or not MAPCs or mesenchmymal (MSC) stem cells can transdifferentiate into functional cardiomyocytes in vitro or in vivo remains unknown. Alternatively, injection of conditioned medium from mesenchymal stem cells may reduce infarct size due to trophic effects. Despite insufficient preclinical data on the long-term fate of bone marrow stem cells, their integration and differentiation in the myocardium and the mechanism of any presumed functional effect in vivo, several uncontrolled non-randomized small scale clinical trials have been initiated in myocardial infarction patients and in patients undergoing coronary artery bypass grafting.
In the studies proposed we will investigate underlying mechanisms of in vivo cell transfer (autrocrine transdifferentiation versus paracrine trophic effects) and explore the possibilities of novel progenitor cell transfer approaches to target the failing heart and the hypertensive pulmonary circulation.

In vitro studies:

• To adapt stem cell culture protocols for maintenance and expansion of porcine MAPCs.
• To explore potential transdifferentiation of human and porcine adult multipotent stem cells into cardiomyocytes.

In vivo studies:

• To investigate different in vivo stem cell transfer protocols in ischemic porcine myocardium and evaluate incorporation, residence, and functional integration in surrounding myocardium.
• To evaluate the potential of undifferentiated versus more differentiated stem cell populations to enhance myocardial contractile function following myocardial infarction and explore possible mechanisms involved.
• To investigate the role of endothelial progenitor cells (EPC) in experimental pulmonary hypertension, we will perform bone marrow transplantation with Tie-2 GFP donor mice and follow homing of progenitor cells to the hypertensive lungs. At the same time, we will study the effect of EPC transfer in pulmonary hypertensive mice.

Post-Doctoral and PhD Students

Peter Pokreisz, Pieter Vermeersch, Glenn Marsboom, Peter Liu, Vandewyngaerd Sarah

Technical Staff

Hilde Gillijns, Marijke Pellens