Abstract 18698: Identification of a Novel Cardiac Progenitor Population Expressing Pw1/peg3 in the Murine Heart

Abstract

The myocardium responds to injury by recruiting cardiac progenitor cells (CPCs) to the injured tissue to promote cardiac repair. Although different classes of CPCs have been identified, their contribution in physiological and pathological conditions remains unclear. PW1 gene has recently been proposed as a marker of resident adult stem and progenitor cell populations in several adult tissues. Our goal was to characterize and determine the role of PW1+ population in the heart. Here, we employ immunostaining and fluorescence-activated cell sorting (FACS) analysis in PW1-reporter mouse to perform qualitative and quantitative analyses of PW1+ population in the heart. We first found that PW1+ cells are mainly located in the epicardium and myocardial interstitium of normal hearts. The average percentage of PW1+ cells, as assessed by FACS, was 1.56±1.41%. A subset of PW1+ cells also co-express other CPC markers such as Sca-1 (52±22%) or PDGFR1α (43±14%). In contrast, a very small proportion of PW1+ cells co-express c-kit (6±5%). To investigate the contribution of PW1+ cells in pathological conditions, we then performed myocardial infarction (MI) by LAD ligation in PW1-reporter mice. We found that MI resulted in a 3-fold increase in the number of PW1+ cells in infarcted mice compared with sham-operated groups, at 1 week post-MI (1.16%±0.47% in sham versus 3.43%±0.82 in MI). This population preferentially localized in the injured myocardium and border area. PW1+ cells were isolated by FACS from the whole infarcted heart from PW1-reporter mice. In vitro differentiation assays reveal that purified PW1+ cells are multipotent and can spontaneously differentiate into smooth muscle cells, endothelial cells and cardiomyocyte-like cells. Taken together, our data identify a novel PW1+ cardiac progenitor population with the potential to undergo differentiation into multiple cardiac lineages, suggesting their involvement in cardiac repair in normal and pathological conditions. The discovery of a novel population of cardiac progenitor cells, augmented following MI and with cardiogenic potential, provides a novel target for therapeutic approaches aimed at improving cardiac regeneration.