Research interests in Dr. John Auchampach's laboratory center around two general areas. The first deals with the molecular and functional characterization of receptors for the endogenous nucleoside adenosine. The second addresses the potential for cardiac regeneration following myocardial infarction using embryonic stem cells.
Techniques in use:
Molecular biology – receptor cloning and expression, radioligand binding, siRNA, real-time PCR, western immunoblotting, ELISA, electromobility shift assay
Cell biology – isolation and functional analysis of mouse macrophages, neutrophils, endothelial cells, and lymphocytes
Mouse genetics – generation of global and tissue-specific gene 'knock-out' mouse lines, bone marrow transplantation
Mouse disease models – In vivo mouse infarction model, aortic banding model of cardiac hypertrophy, Langendorff-perfused isolated mouse heart model of ischemia/reperfusion injury
Mouse physiology – systemic blood pressure and left ventricular pressure and pressure – volume relationship measurements, echocardiography
Molecular and Functional Characterization of Adenosine Receptors
Adenosine is an important signaling molecule that exerts effects in essentially every organ system by interacting with four G protein-coupled receptors designated A1, A2A, A2B, and A3. Our laboratory employs modern techniques of molecular pharmacology to understand adenosine receptor function at both the molecular and physiological level. Current emphasis is focused on the two most recently identified receptors for adenosine, the A2B and A3 receptors. Studies underway in the laboratory include cloning and pharmacological characterization of adenosine receptors, analysis of adenosine receptor signaling in cells, and functional characterization of adenosine receptors in mouse models of pathogenesis using genetically modified mice.
We are currently assessing the importance of the newly discovered A3 adenosine receptor during myocardial infarction. Our laboratory has previously shown that administering agonists with high affinity for the A3 adenosine receptor reduces injury from myocardial ischemia and reperfusion in dogs, rabbits, and mice if given prior to the ischemic event or if given only during reperfusion. Using global and cardiac-specific A3 adenosine receptor gene 'knock-out' mice (Cre recombinase-loxP strategy) and bone marrow chimeric mice lacking the expression of the A3 adenosine receptor in bone marrow-derived cells, we are testing the hypothesis (see Figure 1 below) that activating the A3 adenosine receptor in cardiomyocytes protects against ischemic injury by improving mitochondrial function and reducing apoptosis, whereas activating the A3 adenosine receptor in immune cells during reperfusion is protective by suppressing inflammatory responses. Correlative molecular/cellular studies are underway to examine the function of the A3 adenosine receptor in specific populations of inflammatory cells isolated from the mouse including neutrophils, monocytes, macrophages, and endothelial cells.
Figure 1. Schematic diagram illustrating the potential role that A3 adenosine receptors play during myocardial ischemia/reperfusion injury.
Cardiac Regeneration Using Embryonic Stem Cells
Embryonic stem cells have the potential to differentiate into any cell type in the body and are therefore attractive for application to tissue regeneration. We and others have shown that injecting small numbers of pluripotent mouse embryonic stem cells results in cell engraftment and functional improvement of post-infarcted mouse myocardium (see Figure 2 below), although the mechanism for improvement is uncertain and the potential for tumorogenesis remains a concern. In collaboration with others at MCW, we are addressing the hypothesis that transplantation of mouse embryonic stem cells pre-differentiated in cell culture to specific cardiac lineages (i.e., cardiomyocytes, vascular precursor cells) will reduce the potential for tumor formation and improve functional recovery due to the incorporation of functional, electrically coupled myocytes into the myocardium.
Figure 2. X-gal staining of a mouse heart 9 weeks after infarction and transplantation of pluripotent ES cells with constitutive expression of a lacZ reporter gene.