Abstract
BACKGROUND: Overexpression of Pim-1 in stem/progenitor cells stimulated cell cycling and enhanced cardiac regeneration in vivo. We proposed that hypoxic preconditioning could increase survival of bone marrow mesenchymal stem cells (MSCs) via upregulation of Pim-1 and aimed to determine the microRNAs that modulate the expression of Pim-1. METHODS AND RESULTS: MSCs were subjected to hypoxia exposure. The expression of Pim-1 in MSCs was enhanced in a time-dependent manner, detected by quantitative PCR and western blot. miR-206 is predicted as one of the potential microRNAs that target Pim-1. The expression of miR-206 was decreased in hypoxic MSCs and reversely correlated with Pim-1 expression. Luciferase activity assay further confirmed Pim-1 as a putative target of miR-206. In addition, gain and loss-of-function studies with miR-206 mimics and inhibitors showed that inhibition of miR-206 in hypoxic MSCs promoted the migration ability of the cells, prevented cell apoptosis, and protected membrane potential of mitochondria, while the benefits were all blocked by Pim-1 inhibitor. In an acute model of myocardial infarction, transplanted hypoxic MSCs showed a significantly improved survival as compared with hypoxic MSCs overexpressing miR-206. CONCLUSIONS: Hypoxic preconditioning could increase short-term survival of bone marrow MSCs via upregulation of Pim-1, and miR-206 was one of the critical regulators in this process.