Sca1+/CD31−/PDGFRa+ Cardiac Stem Cells are from an Epicardial/Mesodermal but not Neural-crest, Cardiomyocyte or Bone-marrow Origin

3 SCA1+/CD31−/PDGFRA+ CARDIAC STEM CELLS ARE FROM AN EPICARDIAL/MESODERMAL BUT NOT NEURAL-CREST, CARDIOMYOCYTE OR BONE-MARROWORIGIN James Chong1,2, Owen Prall 1, Vashe Chandrakanthan1, Munira Xaymardan1, Ishtiaq Ahmed1, Chris Scarlett 2, Emily Colvin2, Mark Pinese2, Andrew Biankin2, Richard Harvey1 1 Victor Chang Cardiac Research Institute, Sydney, Australia 2 Garvan Institute of Medical Research, Sydney, Australia Background: Support for the ambitious goal of therapeutic cardiac regeneration has come from the recent discovery of endogenous cardiac stem cells in the postnatal heart. The biological origin of these cells remains a fundamental, yet unanswered question. Methods: By employing the colony forming unit fibroblast (CFU-F) assay, we have previously shown that a subpopulation (cCFU-F) of Sca1+/CD31−/PDGFRa+ cells from the adult murine heart are clonogenic, long term self renewing and multi-potent (properties of true stem cells). Using state-of-the-art Cre-Lox technology, double transgenic (Cre/ZEG-Reporter) mice were created to conduct lineage tracing of cCFU-F. A possible epicardial, mesodermal, neural-crest or cardiomyocyte origin was investigated by placing Cre-recombinase under the control of GATA5, Mesp1, Wnt1 and Nkx2.5 promoters, respectively. To investigate a possible bone-marrow (BM) origin, BM was transplanted from transgenic mice ubiquitously expressing enhanced green fluorescent protein ( -actin-EGFP) into lethally irradiated wild-type recipients. Results: Percentage of cCFU-F colonies from respective lineage origins (n= 3) were 70± 9% epicardial, 81± 11% mesodermal, 2± 2% cardiomyocyte, 0± 0% neural-crest. Few Sca1+/CD31−/PDGFRa+ cardiac cells were BM derived at 3 months (5.1± 1%) and 6 months (0.5± 0.4%) post-transplantation. Colony forming ability of cCFU-F in irradiated mice was lost and not rescued by the transplantation of non-irradiated donor BMeither after normal aging or myocardial infarction to stimulate BM stem cell homing. Conclusions/significance: cCFU-F endogenous cardiac stem cells are derived from an epicardial and mesodermal origin but not from the neural-crest, dedifferentiated cardiomyocytes or adult BM. Knowledge of stem cell origins will aid progress toward successful translation of cell/regenerative strategies. doi:10.1016/j.hlc.2009.05.005 Ralph Reader Finalists – Clinical