Leukemia Inhibitory Factor Induces Endothelial Differentiation in Cardiac Stem Cells

Abstract

The importance of interleukin 6 (IL-6)-related cytokines in cardiac homeostasis has been studied extensively; however, little is known about their biological significance in cardiac stem cells. Here we describe that leukemia inhibitory factor (LIF), a member of IL-6-related cytokines, activated STAT3 and ERK1/2 in cardiac Sca-1؉ stem cells. LIF stimulation resulted in the induction of endothelial cell-specific genes, including VE-cadherin, Flk-1, and CD31, whereas neither smooth muscle nor cardiac muscle marker genes such as GATA4, GATA6, Nkx-2.5, and calponin were up-regulated. Immunocytochemical examination showed that about 25% of total cells were positively stained with anti-CD31 antibody 14 days after LIF stimulation. Immunofluorescent microscopic analyses identified the Sca-1؉ cells that were also positively stained with anti-von Willebrand factor antibody, indicating the differentiating process of Sca-1؉ cells into the endothelial cells. IL-6, which did not activate STAT3 and ERK1/2, failed to induce the differentiation of cardiac stem cells into the endothelial cells. In cardiac stem cells, the transduction with dominant negative STAT3 abrogated the LIFinduced endothelial differentiation. And the inhibition of ERK1/2 with the MEK1/2 inhibitor U0126 also prevented the differentiation of Sca-1؉ cells into endothelial cells. Thus, both STAT3 and ERK1/2 are required for LIF-mediated endothelial differentiation in cardiac stem cells. Collectively, it is proposed that LIF regulates the commitment of cardiac stem cells into the endothelial cell lineage, contributing to neovascularization in the process of tissue remodeling and/or regeneration.Cardiac homeostasis is maintained by various kinds of extracellular signals through paracrine factors. Among these signals, interleukin 6 (IL-6) 2 -related cytokines have been demonstrated to play important roles in cardioprotection (1), vessel formation (2, 3), and cell-cell adhesion (4) in the heart. IL-6-related cytokines utilize glycoprotein 130 (gp130) as a common receptor. Signals through gp130 activate the signal transducer and activator of transcription (STAT) proteins and extracellular signal-regulated kinases 1/2 (ERK1/2) (5). Activated STAT proteins function as latent transcription factors and up-regulate a wide range of target genes, including bcl-xL (6), VEGF (7), metallothionein (1), MnSOD (manganese superoxide dismutase) (8), and Wnt5a (4). Recently it has been reported that cardiomyocyte-restricted ablation of the STAT3 gene results in heart failure, accompanied by impairment of vessel growth and high sensitivity to cardiac injury (9, 10). Thus the importance of IL-6-related cytokines/gp130/STAT pathway has been established in cardiac myocytes; however, the possibility remains to be fully addressed that IL-6-related cytokines stimulate the non-myocyte population in the heart and contribute to cardiac homeostasis.Previously it was believed that cardiac myocytes exited from the cell cycle immediately after birth and regenerated only to a lesser extent. Howeve...

The Heme Oxygenase 1 Inducer (CoPP) Protects Human Cardiac Stem Cells against Apoptosis through Activation of the Extracellular Signal-regulated Kinase (ERK)/NRF2 Signaling Pathway and Cytokine Release

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