The primary goal of my laboratory is to define the earliest steps in mammalian cardiogenesis. We use genetically-modified mice as our in vivo model to take advantage of a broad range of molecular tools available for germline manipulation (Figure 1). The developmental similarity between a four-chambered heart in mice and humans allows us to translate directly our research findings into relevant human disease contexts. Despite these advantages, the mouse model is difficult, if not impossible, to gain access into earliest developing mesoderm, particularly if one wishes to investigate the mechanisms involved in myocardial lineage commitment and separation from other mesodermal lineages. To overcome this challenge, we employed murine embryonic stem (ES) cells as an in vitro model of cardiogenesis. ES cells are pluripotent and differentiate spontaneously in vitro into cells of many lineages including beating cardiomyocytes (Video 1). Their developmental progression from undifferentiated to lineage-specific progenitor cells mimics early embryonic development. To isolate the earliest committed cardiac progenitor cells, we applied a lineage tracing approach combined with fluorescent-activated cell sorting to isolate a rare population of Nkx2.5 expressing cells that develop specifically into beating cardiomyocytes both in vitro and in vivo. These cells are clonogenic, highly proliferative, and express markers of stem cells such as c-kit and Sca-1. We found, quite unexpectedly, that the c-kit and Nkx2.5 double positive cells from both ES cells and the developing embryo are capable of differentiating into vascular smooth muscle cells as well. These findings suggest a common origin for myocardial and smooth muscles cells in the developing precardiac mesoderm and that regulatory mechanisms must exist to facilitate differentiation of these precursor cells into either lineage.
Expression of eGFP Specifically in the Developing Heart Tube. Transgenic mouse embryo at embryonic day 9.5 is directed to express eGFP under a cardiac-specific enhancer from the murine Nkx2.5 locus. Image shown is a composite of eGFP signal (in green) with the body of the embryo (in white).
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Beating Cardiomyocytes Derived from In Vitro Differentiated ES Cells. CJ7 ES cells were electroporated with a-MHC-eGFP vector and selected for stably integrated clones that expresses eGFP specifically in beating cardiomyocytes. Video shown represents fluorescence microscopy images of one such ES cell clone that has differentiated for 17 days.
The current research projects in the laboratory address the following aims:
1. Identify molecular determinants regulating lineage separation and commitment of
mammalian precardiac mesoderm into myocardial, vascular smooth muscle, and
2. Characterize the developmental potential and gene expression signature of cardiac
progenitor cells (CPCs) and confirm in vivo the cardiac specificity of novels genes
identified through transcript profiling.
3. Generate a monoclonal antibody library against unique cell surface markers on CPCs
and CPC-derived myocytes. With the availability of such antibody, the identity of the
surface marker will be uncovered through biochemical approaches.
4. Determine the myocardial regenerative potentials of CPCs in a myocardial
injury-reconstitution model and compare them with those of bone marrow-derived
cells, undifferentiated ES cells, and ES cell-derived cardiomyocytes.
Sean Wu's lab is a part of the Stem Cell Biology + Therapy Program.
Click here to view Sean Wu's publications. Also review these publications that are relevant to Sean Wu's research:
Wu SM, Fujiwara Y, Scibulsky SM, Clapham DE, Lien C-L, Schultheiss TM, Orkin SH. Developmental origin of a bi-potential myocardial and smooth muscle cell precursor in the mammalian heart. Cell. 2006; 127:1137-1151.
Karra, R. and Wu, SM. Multipotent stem cells in cardiac regeneration. Regen Med. 2008; 3:189-198.
Bin, Z., Ma, Q., Rajagopal, S., Wu, SM., Domian, I., Rivera-Feliciano, J., Jiang, D., von Gise, A., Ikeda, S., Chien, KR., Pu, WT. Epicardial progenitors contribute to the cardiomyocyte lineage in the developing heart. Nature. 2008; 454:109-113.
Wu, SM., Chien, KR., Mummery, C. Origins and fates of cardiovascular progenitor cells. Cell. 2008; 132:537-543.
Liu, Y-H., Karra, R., and Wu, S.M. Cardiovascular stem cells in regenerative medicine: ready for prime time? Drug Discovery Today: Therapeutic Strategies. 2008; 5:201-207.
Wu, S.M. Mesp1 at the heart of mesodermal lineage specification. Cell Stem Cell. 2008; 3:1-2.
Gregoire, S. and Wu, S.M. Developmental Biology of the Heart. In: Semigran, M.J. and Shin, J. editors. Heart Failure, 2nd Ed. 2008. In press.
Wu, SM. The in vivo fate of induced pluripotent stem cells. Mol Reprod Dev. 2009; 76:525.
Domian, IJ., Chiravuri, M., van der Meer, P., Feinberg, AW., Shi, X., Ying, C., Wu, SM., Parker, KK., Chien, KR. Committed ventricular progenitors in the Islet-1 lineage expand and assemble into functional ventricular heart muscle. Science. 2009; 326(5951):426-9.
Ptaszek LM, Saldana F, Palacios IF, Wu SM. Patypnea-orthodeoxia syndrome in two previously healthy adults: a case-based review. Clinical Medicine: Cardiology. 2009; 3:37-43.
Huang, X., Oh, J.B., and Wu, S.M. Pluripotent stem cells and cardiac regeneration. In: Appasani, K. editor. Stem Cells and Regenerative Medicine. 1st Ed. 2009. Humana Press. In press.
Pijnappels, D.A., Gregoire, S., Wu, SM. Integrated aspects of cardiac cell therapy. Ann. N.Y. Acad. Sci. 2010; 1188:7-14.
Huang, X., Wu, S.M. Isolation and characterization of cardiac progenitor cells from pluripotent stem cells. Curr Protoc Stem Cell Biol. 2010; In Press.
Liu, Y-H., Chen, W-P., Wu, S.M. Cardiac progenitor cells as a target of pharmacological intervention in an aging heart. Ageing Health. 2010; In Press.
Krane, M., and Wu, S.M. Cell replacement strategies in heart failure. Drug Discovery Today: Disease Mechanisms. 2010; In Press.
Wu, S.M. Limited contribution by cardiomyogenic precursors cells in postnatal cardiomyogenesis and regeneration after infarction. J Cell Physiology. 2010; In Press.
For additional information regarding current research projects and availability of job position or if you are interested in supporting our research efforts, please contact:
Sean M. Wu, M.D. Ph.D.
CPZ3224 Simches Research Building
185 Cambridge St.
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