Liansheng Wang

AIMS: The inflammatory responses of monocytes/macrophages and the stimulation of lipid uptake into these cells by oxidized low density lipoprotein (oxLDL) are critical to the initiation and development of atherosclerosis. Increasing evidence has demonstrated that many microRNAs play important roles in the cell proliferation, apoptosis, and differentiation that accompany inflammatory responses. However, whether microRNAs are associated with monocyte/macrophage inflammatory responses or oxLDL stimulation is not yet known. The aim of the present study is to investigate microRNAs in monocytes/macrophages and their potential role in oxLDL-stimulation of lipid uptake and other atherosclerotic responses. METHODS AND RESULTS: Microarrays were used to analyse the global expression of microRNAs in oxLDL-stimulated human primary peripheral blood monocytes. Expression profiles of the microRNAs were verified using TaqMan real-time PCR. Five microRNAs (microRNA-125a-5p, microRNA-9, microRNA-146a, microRNA-146b-5p, and microRNA-155) were aberrantly expressed after oxLDL treatment of human primary monocytes. Bioinformatics analysis suggested that microRNA-125a-5p is related to a protein similar to ORP9 (oxysterol binding protein-like 9) and this was confirmed by a luciferase reporter assay. MicroRNA-125a-5p was found to mediate lipid uptake and to decrease the secretion of some inflammatory cytokines (interleukin-2, interleukin-6, tumour necrosis factor-alpha, transforming growth factor-beta) in oxLDL-stimulated monocyte-derived macrophages. CONCLUSION: MicroRNA-125a-5p may partly provide post-transcriptional regulation of the proinflammatory response, lipid uptake, and expression of ORP9 in oxLDL-stimulated monocyte/macrophages.

VEGF and angiopoietin-1 (Ang1) are two major angiogenic factors being investigated for the treatment of myocardial infarction (MI). Targeting VEGF and Ang1 expression in the ischemic myocardium can increase their local therapeutic effects and reduce possible adverse effects. Adeno-associated viral vectors (AAVs) expressing cardiac-specific and hypoxia-inducible VEGF [AAV-myosin light chain-2v (MLC)VEGF] and Ang1 (AAV-MLCAng1) were coinjected (VEGF/Ang1 group) into six different sites of the porcine myocardium at the peri-infarct zone immediately after ligating the left descending coronary artery. An identical dose of AAV-Cytomegalovirus (CMV)LacZ or saline was injected into control animals. AAV genomes were detected in the liver in addition to the heart. RT-PCR, Western blotting, and ELISA analyses showed that VEGF and Ang1 were predominantly expressed in the myocardium in the infarct core and border of the infarct heart. Gated single-photon emission computed tomography analyses showed that the VEGF/Ang1 group had better cardiac function and myocardial perfusion at 8 wk than at 2 wk after vector injection. Compared with the saline and LacZ controls, the VEGF/Ang1 group expressed higher phosphorylated Akt and Bcl-xL, less Caspase-3 and Bad, and had higher vascular density, more proliferating cardiomyocytes, and less apoptotic cells in the infarct and peri-infarct zones. Thus, cardiac-specific and hypoxia-induced coexpression of VEGF and Ang1 improves the perfusion and function of porcine MI heart through the induction of angiogenesis and cardiomyocyte proliferation, activation of prosurvival pathways, and reduction of cell apoptosis.

BACKGROUND: Mesenchymal stem cells (MSCs)-based regenerative therapy is currently regarded as an alternative approach to salvage the acute myocardial infarcted hearts. However, the efficiency of MSCs transplantation is limited by lower survival rate of engrafted MSCs. In previous study, we found that 1.0 microg/ml Lipopolysaccharide (LPS) could protect MSCs against apoptosis induced by oxidative stress and meanwhile enhance the proliferation of MSCs. Therefore, in the present study, we firstly preconditioned MSCs with 1.0 microg/ml LPS, then transplanted MSCs into ischemic myocardium, and observed the survival and cardiac protective capacity of MSCs in a rat model of acute myocardial infarction. Furthermore, we tried to explore the underlying mechanisms and the role of Toll-like receptor-4 (TLR4) in the signal pathway of LPS-induced cardiac protection. METHODS AND RESULTS: Acute myocardial infarction model was developed by left anterior descending coronary artery ligation. 60 rats were divided into 4 groups randomly and given an intramyocardial injection of one of the following treatments: 30 microl PBS (control group), 3 x 10(6) wild MSCs/30 microl (wMSCs group), 3 x 10(6) LPS-preconditioned wild MSCs/30 microl (LPS-wMSCs group), or 3 x 10(6) LPS-preconditioned TLR4 gene deleted MSCs/30 microl (LPS-tMSCs group). After 3 weeks, LPS-preconditioned wild MSCs transplantation ameliorated cardiac function and reduced fibrosis of infarcted myocardium. Vascular density was markedly increased in LPS-wMSCs group compared with other three groups. Survival rate of engrafted MSCs was elevated and apoptosis of myocardium was reduced in infarcted heart. Expression of vascular endothelial growth factor (VEGF) and phospho-Akt was increased in the infarcted myocardium after transplantation of LPS-preconditioned MSCs. CONCLUSION: LPS preconditioning enhanced survival of engrafted MSCs, stimulated expression of VEGF and activated PI3K/Akt pathway. LPS preconditioning before MSCs transplantation resulted in superior therapeutic neovascularization and recovery of cardiac function. LPS preconditioning provided a novel strategy in maximizing biologic and functional properties of MSCs.