Abstract 14169: Pim-1 Kinase is Required for Endothelial Differentiation of Cardiac Stem Cells via STAT3 Signaling Pathway
Background: Cardiac Sca-1+ cells potentially differentiate into cardiac cells, including cardiomyocytes and endothelial cells (ECs). Previously we reported that STAT3 activation by IL-6 family cytokines induces EC differentiation of cardiac Sca-1 cells; however, precise mechanisms have not been fully elucidated.
Methods and Results: Sca-1+ cells were isolated from adult murine hearts by MACS system. First, we examined the expression profile of EC-related genes in cultured Sca-1+ cells in response to leukemia inhibitory factor (LIF) by RT-PCR and found that LIF upregulated Pim-1 gene transcript. Adenoviral transfer of dominant negative (DN) STAT3 prevented Pim-1 induction by LIF. Importantly, the overexpression of DN Pim-1 abrogated the induction of EC markers in vitro. Next, Sca-1+ cells were labeled with adenovirus vector expressing LacZ (Adeno-LacZ) and injected into the border zone of myocardial infarction. The efficiency of EC differentiation was immunohistochemically assessed with anti-CD31 antibody 2 weeks after transplantation. Ratio of EC differentiation, estimated as ratio of CD31+/LacZ+ cells to LacZ+, was increased in Sca-1+ cells adenovirally transduced with wild-type STAT3 (LacZ+ cells from 5 mice, 47.0 ± 3.6%), compared to non-treated Sca-1+ cells (LacZ+ cells from 4 mice, 33.6% ± 3.7%, P<0.01). In contrast, STAT3-null Sca-1+ cells, which were generated by infecting Adeno-Cre into Sca-1+ cells from STAT3 flox/flox mice, exhibited lower ratio of EC differentiation (LacZ+ cells from 4 mice, 23.0 ± 1.1%, P<0.01). Finally, by overexpressing DN Pim-1, EC differentiation was observed in LacZ-labeled Sca-1 cells at lower ratio (LacZ+ cells from 5 mice, 25.4 ± 2.6%, P<0.01). Collectively, STAT3/Pim-1 pathway plays functional roles in endothelial differentiation in vivo.
Conclusions: STAT3 activation upregulates Pim-1 in Sca-1+ cells, leading to endothelial differentiation both in vitro and in vivo.
- © 2010 by American Heart Association, Inc.