Abstract 302: Cardiac Stromal Cells Response to Lineage-Specific Differentiation Signals Reveals Commitment to a Cardiovascular Differentiation Default Program
INTRODUCTION: stromal cells are able to transdifferentiate into different cell types even unrelated to the origin tissue. Among them, the most characterized are bone marrow stromal cells (BMSC). Here we report a quantitative comparison between the in vitro differentiative potential of BMSCs, used as reference cells, and cardiac stromal cells (CSC) both derived from the same patients.
METHODS AND RESULTS: Plastic adherent CSC and BMSC were obtained from auricle fragments and sternal bone marrow respectively. FACS analysis revealed a phenotype virtually indistinguishable from BMSC, characterized by the presence of CD105, CD13, CD44, CD73, CD29 while HLA-DR, CD45, CD34 and CD14 were negative. In spite of this similarity several molecular and biological differences emerged between the two cell populations. Specifically, real-time PCR analysis showed that CSC expressed higher basal levels of Gata4 and Gata6 mRNA respectively 120 and 35 fold above BMSCs. In addition, micro RNA (miRNA) expression profiling identified a specific CSC miRNA signature consisting of miRNA 146a, 146b, 330 and miRNA 10a, 10b, 196a, 196b respectively up- and down-regulated compared to BMSC. A series of “in vitro” differentiation assays identified further differences:
BMSC, but not CSC, became positive to alkaline phosphatase assay when cultured into osteogenic medium.
BMSC cultured in adipogenic medium, revealed a significant increase in the expression of PPAR-gamma2 and Adipsin transcripts and in Oil-Red-O content.
CSC acquired endothelial markers includimg CD144, VEGFR2 and CD31 and their ability to form capillary-like structure on a cultrex layer was siginificantly higher compared to BMSC.
When treated with All-Trans Retinoic Acid and Phenylbutyrate, CSC exhibited a gene expression pattern clearly oriented towards a cardiomyogenic phenotype compared to BMSC, as demonstrated by the increase in GATA4, alpha-MHC, Tn-I and alpha-sarcomeric actin transcripts.
CONCLUSION: although immunologically similar CSC and BMSC differ in their lineage-specific responses and reveals distinct predispositions to differentiation signals, being CSC more sensitive to vasculogenic and cardiogenic stimuli.