Abstract 304: Proteomic Analysis of Cardiac Stem Cells Derived from Adult Rat Hearts: Comparison of the Sphere and Adherent States of a Cardiosphere Forming Cell Clone by Protein Profiling
We recently isolated and established cardiac stem cells (CSCs) from adult rat heart using c-kit antibody. Among those cell clones, CSCs-2E showed distinct spheroid cell aggregates when maintained in the Cardiosphere (CS) medium. Sphere-forming is commonly used for isolating stem cells, since it is considered to be one of the markers for stemness. CSCs-2E showed floating spheroids (flCS) in CS medium in bacterial dishes, but adhered to the substrate showing fibroblastic morphology when transferred into gelatin coated dishes. This clone, however, reverted back to floating spheroids when transferred back to bacterial dishes. We asked whether it is possible to obtain characteristics of the cells by protein profiling analysis. In this work, we compared the protein profiles of CSCs-2E, in floating spheroids and adherent cells (adCS) by using 2D differential gel-electrophoresis (2D-DIGE). Although most of the proteins showed the same level of expression in both samples, a fraction showed different levels of expression. Among the identified proteins with the same level of expression, some of the proteins characteristically observed in human and murine embryonal stem (ES) cells were included, indicating the proteomic signature of stemness. On the other hand, some of the identified proteins in CSCs-2E are unique indicating that these cells may be distinctly different from ES cells, likely to have advanced into a course for differentiation. In the comparison of flCS and adCS, a minor portion of proteins lost expression with new proteins appearing after the adhesion to the gelatin coated dishes. Among a group of proteins differently expressed in flCS and adCS, those down regulated in adCS contained glycolytic enzymes and other metabolic enzymes while some category of proteins, namely chaperons and annexins seem to switch their members upon adhesion. Although flCS and adCS can be reversibly switched by changing culture conditions, somewhat more proteins were obtained in the profiles of adCS, implying that physical change of flCS cells could induce transcriptional and/or translational switches. The comparative protein profiling opens new horizon of the research into the understanding of the stem cell development and the character of cardiac stem cells.