ADIPOSE-DERIVED STEM CELLS AND THEIR CARDIOGENIC DIFFERENTIATION

Heart diseases are leading causes of death in the world. The inability of heart muscles to regenerate or restore the lost function makes the use of stem cells an attractive therapeutic option for patients with heart diseases. Stromal cells from fat tissue, namely adipose-derived stem cells (ADSCs), exhibit properties of mesenchymal stem cells and can be differentiated towards several cell types. That adipose tissue is abundant and easily harvested from patient¡¯s own body makes it an ideal source for patient specific stem cells. Yet, less is known about the capacity for self-renewal and stability properties of mesenchymal ADSCs during expansion in culture. Furthermore, efficient differentiation of these cells towards cardiogenic lineage has not been established. We first characterized human ADSCs cultured for varying times. Flow cytometry indicated that ADSCs maintained expression of mesenchymal markers (CD29, CD44 and CD90) for extended expansion over 20 passages. In contrast, mRNAs for pluripotent markers, such as Nanog, Oct4 and Sox2, were significant only in early passages, but were dramatically declined during culture. Serum removal increased mRNA levels for various cardiogenic genes, such as Mef2C, cardiac actin and troponin. Moreover, the protein kinase activator phorbol ester (phorbol myristate acetate PMA, 10 nM) caused further increases in these cardiac mRNAs. The upregulation of cardiac mRNAs by serum removal and PKC activation were constant in ADSCs cultured for various times. The use of various inhibitors specific for PKC subtypes suggested that the novel PKC theta/delta isoforms mediate this upregulation. RT-PCR revealed that ADSCs express significant mRNA for PKC delta, but not theta isoform. Overexpression of cDNA for PKC delta resulted in marked increases in cardiac mRNA expression. These results indicate that activation of PKC delta induces expression of multiple cardiogenic genes freshly-prepared and expanded ADSCs. These findings demonstrated that human ADSCs maintain the expression of mesenchymal markers and the ability to exhibit cardiac gene expression for extended expansion. They also suggest that a specific signaling molecule is involved in the transdifferentiation towards cardiogenic lineage