Xiaohu Ge

Direct Evaluation of Myocardial Viability and Stem Cell Engraftment Demonstrates Salvage of the Injured Myocardium

RATIONALE The mechanism of functional restoration by stem cell therapy remains poorly understood. Novel manganese-enhanced MRI and bioluminescence reporter gene imaging were applied to follow myocardial viability and cell engraftment, respectively. Human-placenta-derived amniotic mesenchymal stem cells (AMCs) demonstrate unique immunoregulatory and precardiac properties. In this study, the restorative effects of 3 AMC-derived subpopulations were examined in a murine myocardial injury model: (1) unselected AMCs, (2) ckit(+)AMCs, and (3) AMC-derived induced pluripotent stem cells (MiPSCs). OBJECTIVE To determine the differential restorative effects of the AMC-derived subpopulations in the murine myocardial injury model using multimodality imaging. METHODS AND RESULTS SCID (severe combined immunodeficiency) mice underwent left anterior descending artery ligation and were divided into 4 treatment arms: (1) normal saline control (n=14), (2) unselected AMCs (n=10), (3) ckit(+)AMCs (n=13), and (4) MiPSCs (n=11). Cardiac MRI assessed myocardial viability and left ventricular function, whereas bioluminescence imaging assessed stem cell engraftment during a 4-week period. Immunohistological labeling and reverse transcriptase polymerase chain reaction of the explanted myocardium were performed. The unselected AMC and ckit(+)AMC-treated mice demonstrated transient left ventricular functional improvement. However, the MiPSCs exhibited a significantly greater increase in left ventricular function compared with all the other groups during the entire 4-week period. Left ventricular functional improvement correlated with increased myocardial viability and sustained stem cell engraftment. The MiPSC-treated animals lacked any evidence of de novo cardiac differentiation. CONCLUSION The functional restoration seen in MiPSCs was characterized by increased myocardial viability and sustained engraftment without de novo cardiac differentiation, indicating salvage of the injured myocardium.

Human Amniotic Mesenchymal Stem Cell-Derived Induced Pluripotent Stem Cells May Generate a Universal Source of Cardiac Cells

Human amniotic mesenchymal stem cells (hAMSCs) demonstrated partially pluripotent characteristics with a strong expression of Oct4 and Nanog genes and immunomodulatory properties characterized by the absence of HLA-DR and the presence of HLA-G and CD59. The hAMSCs were reprogrammed into induced pluripotent stem cells (iPSCs) that generate a promising source of universal cardiac cells. The hAMSC-derived iPSCs (MiPSCs) successfully underwent robust cardiac differentiation to generate cardiomyocytes. This study investigated 3 key properties of the hAMSCs and MiPSCs: (1) the reprogramming efficiency of the partially pluripotent hAMSCs to generate MiPSCs; (2) immunomodulatory properties of the hAMSCs and MiPSCs; and (3) the cardiac differentiation potential of the MiPSCs. The characteristic iPSC colony formation was observed within 10 days after the transduction of the hAMSCs with a single integration polycistronic vector containing 4 Yamanaka factors. Immunohistology and reverse transcription-polymerase chain reaction assays revealed that the MiPSCs expressed stem cell surface markers and pluripotency-specific genes. Furthermore, the hAMSCs and MiPSCs demonstrated immunomodulatory properties enabling successful engraftment in the SVJ mice. Finally, the cardiac differentiation of MiPSCs exhibited robust spontaneous contractility, characteristic calcium transience across the membrane, a high expression of cardiac genes and mature cardiac phenotypes, and a contractile force comparable to cardiomyocytes. Our results demonstrated that the hAMSCs are reprogrammed with a high efficiency into MiPSCs, which possess pluripotent, immunomodulatory, and precardiac properties. The MiPSC-derived cardiac cells express a c-kit cell surface marker, which may be employed to purify the cardiac cell population and enable allogeneic cardiac stem cell therapy.

Apelin Enhances Directed Cardiac Differentiation of Mouse and Human Embryonic Stem Cells

Apelin is a peptide ligand for an orphan G-protein coupled receptor (APJ receptor) and serves as a critical gradient for migration of mesodermal cells fated to contribute to the myocardial lineage. The present study was designed to establish a robust cardiac differentiation protocol, specifically, to evaluate the effect of apelin on directed differentiation of mouse and human embryonic stem cells (mESCs and hESCs) into cardiac lineage. Different concentrations of apelin (50, 100, 500 nM) were evaluated to determine its differentiation potential. The optimized dose of apelin was then combined with mesodermal differentiation factors, including BMP-4, activin-A, and bFGF, in a developmentally specific temporal sequence to examine the synergistic effects on cardiac differentiation. Cellular, molecular, and physiologic characteristics of the apelin-induced contractile embryoid bodies (EBs) were analyzed. It was found that 100 nM apelin resulted in highest percentage of contractile EB for mESCs while 500 nM had the highest effects on hESCs. Functionally, the contractile frequency of mESCs-derived EBs (mEBs) responded appropriately to increasing concentration of isoprenaline and diltiazem. Positive phenotype of cardiac specific markers was confirmed in the apelin-treated groups. The protocol, consisting of apelin and mesodermal differentiation factors, induced contractility in significantly higher percentage of hESC-derived EBs (hEBs), up-regulated cardiac-specific genes and cell surface markers, and increased the contractile force. In conclusion, we have demonstrated that the treatment of apelin enhanced cardiac differentiation of mouse and human ESCs and exhibited synergistic effects with mesodermal differentiation factors.

Manganese-Enhanced Magnetic Resonance Imaging Enables In Vivo Confirmation of Peri-Infarct Restoration Following Stem Cell Therapy in a Porcine Ischemia-Reperfusion Model.

Background The exact mechanism of stem cell therapy in augmenting the function of ischemic cardiomyopathy is unclear. In this study, we hypothesized that increased viability of the peri-infarct region (PIR) produces restorative benefits after stem cell engraftment. A novel multimodality imaging approach simultaneously assessed myocardial viability (manganese-enhanced magnetic resonance imaging [MEMRI]), myocardial scar (delayed gadolinium enhancement MRI), and transplanted stem cell engraftment (positron emission tomography reporter gene) in the injured porcine hearts. Methods and Results Twelve adult swine underwent ischemia–reperfusion injury. Digital subtraction of MEMRI-negative myocardium (intrainfarct region) from delayed gadolinium enhancement MRI–positive myocardium (PIR and intrainfarct region) clearly delineated the PIR in which the MEMRI-positive signal reflected PIR viability. Human amniotic mesenchymal stem cells (hAMSCs) represent a unique population of immunomodulatory mesodermal stem cells that restored the murine PIR. Immediately following hAMSC delivery, MEMRI demonstrated an increased PIR viability signal compared with control. Direct PIR viability remained higher in hAMSC-treated hearts for >6 weeks. Increased PIR viability correlated with improved regional contractility, left ventricular ejection fraction, infarct size, and hAMSC engraftment, as confirmed by immunocytochemistry. Increased MEMRI and positron emission tomography reporter gene signal in the intrainfarct region and the PIR correlated with sustained functional augmentation (global and regional) within the hAMSC group (mean change, left ventricular ejection fraction: hAMSC 85±60%, control 8±10%; P<0.05) and reduced chamber dilatation (left ventricular end-diastole volume increase: hAMSC 24±8%, control 110±30%; P<0.05). Conclusions The positron emission tomography reporter gene signal of hAMSC engraftment correlates with the improved MEMRI signal in the PIR. The increased MEMRI signal represents PIR viability and the restorative potential of the injured heart. This in vivo multimodality imaging platform represents a novel, real-time method of tracking PIR viability and stem cell engraftment while providing a mechanistic explanation of the therapeutic efficacy of cardiovascular stem cells.

Manganese-enhanced MRI detects live human amnion-derived mesenchymal stem cells in vivo after transplantation and restoration of myocardial function in a pig ischemia-reperfusion injury model

Summary Human Amnion-derived Mesenchymal Stem Cells (hAMSCs) were transplanted into the infarct and periinfarct regions of a pig ischemia-reperfusion model. The hAMSC therapy improved cardiac systolic function post-MI, compared to control animals, and Cardiac MRI with Manganese-Enhanced MRI (MEMRI) was able to detect increased CNR from live populations of hAMSCs within infarct and peri-infarct zones, as confirmed by human nuclear antigen (hNA) immunostaining. Background

REGENERATIVE CHANGES OF THE PERI-INFARCT INJURY ALLOWS SUSTAINED RESTORATION OF THE INJURED MYOCARDIUM

The human amniotic mesenchymal stem cells (hAMSCs) exhibit immunomodulatory, partially pluripotent, and precardiac properties. They express the c-kit cardiac progenitor marker and are readily reprogrammed to iPSCs (MiPSCs). Dual contrast manganese-enhanced MRI and delayed-enhanced MRI (MEMRI-DEMRI)

DIRECT TRANSDIFFERENTIATION OF HUMAN AMNIOTIC MESENCHYMAL STEM CELLS INTO CARDIAC PROGENITOR-LIKE CELLS

Epigenetic reprogramming by valproic acid (VPA) induces intermediate pluripotency in human amniotic mesenchymal stem cells (hAMSCs). The hAMSCs dedifferentiate into precardiac mesoderms to undergo direct transdifferentiation into cardiac progenitor-like cells, using Wnt-pathway specific small

Manganese-Enhanced cardiac MRI (MEMRI) tracks long-term in vivo survival and restorative benefit of transplanted human Amnion-Derived Mesenchymal Stem Cells (hAMSC) after porcine ischemia-reperfusion injury

Manganese-Enhanced cardiac MRI (MEMRI) tracks long-term in vivo survival and restorative benefit of transplanted human Amnion-Derived Mesenchymal Stem Cells (hAMSC) after porcine ischemia-reperfusion injury Rajesh Dash, Paul J Kim, Yuka Matsuura, Xiaohu Ge, Fumiaki Ikeno, Jennifer K Lyons, Ngan F Huang, Scott Metzler, Patricia Nguyen, Shahriar Heidary, Marie-Claude Parent, Tomoaki Yamamoto, John Cooke, Pilar Ruiz-Lozano, Robert C Robbins, Joseph C Wu, Michael V McConnell, Alan Yeung, Phillip Harnish, Phillip C Yang

Dual contrast CMR for evaluation of telmisartan and amlodipine combination therapy in the diabetic murine myocardial injury model

Background Combination therapy has been shown to improve cardiovascular outcomes in hypertensive, diabetic patients. Amlodipine demonstrates beneficial pleiotropic effects including improved endothelial function, enhanced angiogenesis, and reduced cardiovascular risk. Telmisartan exhibits similar beneficial cardiovascular effects in diabetic patients. Amlodipine in combination with telmisartan may provide a synergistic benefit. In this study, dual contrast CMR, using manganese (manganese-enhanced MRI; MEMRI) and gadolinium (delayed-enhanced MRI; DEMRI), will evaluate the viable myocardium and myocardial scar, respectively, to investigate the underlying mechanism of combined telmisartan and amlodipine therapy.