Abstract 328: Signals Through Glycoprotein 130 Promote the Endothelial Differentiation of Cardiac Sca-1+ Cells
Background: Cardiac Sca-1+ cells were originally identified as multipotent stem cells that can be differentiated into various types of cardiac cells, including cardiomyocytes and endothelial cells. We have previously reported that cardiac Sca-1+ cells are differentiated into endothelial cells by leukemia inhibitory factor (LIF), a proinflammatory cytokine; however, the cytokine signals responsible for the stem cell differentiation have not been fully elucidated. In the present study, we investigated the effects of various cytokines, such as IL-1α, TNF-β, IL-6, IL-11 and cardiotrophin-1 (CT-1), on endothelial differentiation of cardiac Sca-1+ cells, since these cytokines are produced by myocardium.
Methods and Results: Cardiac Sca-1+ cells were prepared from adult murine hearts by magnetic cell sorting. Analyzed by RT-PCR, it was revealed that IL-1 receptor (R), TNFR1/2, IL-11R, and LIFR, a common receptor for CT-1 and LIF, were expressed in cardiac Sca-1+ cells, but not IL-6R. The expression of glycoprotein 130 (gp130), a common β receptor of IL-6 family cytokines, such as IL-6, IL-11, CT-1 and LIF, was also confirmed in cardiac Sca-1+ cells. RT-PCR analyses demonstrated that cardiac Sca-1+ cells, cultured with IL-11 or CT-1 for 14 days, showed the upregulation of the endothelial marker genes, such as VE-cadherin, CD31 and Flk-1, while none of IL-1β, TNF-α and IL-6 exhibited such effects. Immunocytochemical examination demonstrated that VE-cadherin-positive cells were observed in Sca-1+ cells treated with IL-11 or CT-1 for 14 days (IL-11: 7.8 ± 2.0%, CT-1: 3.1 ± 1.1% of total cells). Importantly, CT-1 and IL-11, but not IL-1β, TNF-α or IL-6, induced the phosphorylation of STAT3 reaching a peak within 15 min in cardiac Sca-1+ cells, analyzed by Western blotting. Finally, in the presence of soluble IL-6 receptor (sIL-6R) which has the potential for activating gp130 in an-IL-6 dependent manner, IL-6 showed the ability to induce VE-cadherin-positive cells (sIL-6R(−): 0.3 ± 0.3%, (+): 8.3 ± 1.6%), accompanied by the rapid activation of STAT3 in cardiac Sca-1+ cells.
Conclusion: Activation of gp130 by IL-6 family cytokines induces the endothelial differentiation in cardiac Sca-1+ cells, proposing a novel mechanism for neovascularization in the heart.