Junwei Liu

Novel MicroRNA Prosurvival Cocktail for Improving Engraftment and Function of Cardiac Progenitor Cell Transplantation

Background— Although stem cell therapy has provided a promising treatment for myocardial infarction, the low survival of the transplanted cells in the infarcted myocardium is possibly a primary reason for failure of long-term improvement. Therefore, the development of novel prosurvival strategies to boost stem cell survival will be of significant benefit to this field. Methods and Results— Cardiac progenitor cells (CPCs) were isolated from transgenic mice, which constitutively express firefly luciferase and green fluorescent protein. The CPCs were transduced with individual lentivirus carrying the precursor of miR-21, miR-24, and miR-221, a cocktail of these 3 microRNA precursors, or green fluorescent protein as a control. After challenge in serum free medium, CPCs treated with the 3 microRNA cocktail showed significantly higher viability compared with untreated CPCs. After intramuscular and intramyocardial injections, in vivo bioluminescence imaging showed that microRNA cocktail-treated CPCs survived significantly longer after transplantation. After left anterior descending artery ligation, microRNA cocktail-treated CPCs boost the therapeutic efficacy in terms of functional recovery. Histological analysis confirmed increased myocardial wall thickness and CPC engraftment in the myocardium with the microRNA cocktail. Finally, we used bioinformatics analysis and experimental validation assays to show that Bim, a critical apoptotic activator, is an important target gene of the microRNA cocktail, which collectively can bind to the 3′UTR region of Bim and suppress its expression. Conclusions— We have demonstrated that a microRNA prosurvival cocktail (miR-21, miR-24, and miR-221) can improve the engraftment of transplanted cardiac progenitor cells and therapeutic efficacy for treatment of ischemic heart disease.

Preclinical derivation and imaging of autologously transplanted canine induced pluripotent stem cells

Derivation of patient-specific induced pluripotent stem cells (iPSCs) opens a new avenue for future applications of regenerative medicine. However, before iPSCs can be used in a clinical setting, it is critical to validate their in vivo fate following autologous transplantation. Thus far, preclinical studies have been limited to small animals and have yet to be conducted in large animals that are physiologically more similar to humans. In this study, we report the first autologous transplantation of iPSCs in a large animal model through the generation of canine iPSCs (ciPSCs) from the canine adipose stromal cells and canine fibroblasts of adult mongrel dogs. We confirmed pluripotency of ciPSCs using the following techniques: (i) immunostaining and quantitative PCR for the presence of pluripotent and germ layer-specific markers in differentiated ciPSCs; (ii) microarray analysis that demonstrates similar gene expression profiles between ciPSCs and canine embryonic stem cells; (iii) teratoma formation assays; and (iv) karyotyping for genomic stability. Fate of ciPSCs autologously transplanted to the canine heart was tracked in vivo using clinical positron emission tomography, computed tomography, and magnetic resonance imaging. To demonstrate clinical potential of ciPSCs to treat models of injury, we generated endothelial cells (ciPSC-ECs) and used these cells to treat immunodeficient murine models of myocardial infarction and hindlimb ischemia.

Early stem cell engraftment predicts late cardiac functional recovery: preclinical insights from molecular imaging.

Background— Human cardiac progenitor cells have demonstrated great potential for myocardial repair in small and large animals, but robust methods for longitudinal assessment of their engraftment in humans is not yet readily available. In this study, we sought to optimize and evaluate the use of positron emission tomography (PET) reporter gene imaging for monitoring human cardiac progenitor cell (hCPC) transplantation in a mouse model of myocardial infarction. Methods and Results— hCPCs were isolated and expanded from human myocardial samples and stably transduced with herpes simplex virus thymidine kinase (TK) PET reporter gene. Thymidine kinase-expressing hCPCs were characterized in vitro and transplanted into murine myocardial infarction models (n=57). Cardiac echocardiographic, magnetic resonance imaging and pressure-volume loop analyses revealed improvement in left ventricular contractile function 2 weeks after transplant (hCPC versus phosphate-buffered saline, P<0.03). Noninvasive PET imaging was used to track hCPC fate over a 4-week time period, demonstrating a substantial decline in surviving cells. Importantly, early cell engraftment as assessed by PET was found to predict subsequent functional improvement, implying a “dose–effect” relationship. We isolated the transplanted cells from recipient myocardium by laser capture microdissection for in vivo transcriptome analysis. Our results provide direct evidence that hCPCs augment cardiac function after their transplantation into ischemic myocardium through paracrine secretion of growth factors. Conclusions— PET reporter gene imaging can provide important diagnostic and prognostic information regarding the ultimate success of hCPC treatment for myocardial infarction.

Safe Genetic Modification of Cardiac Stem Cells Using a Site-Specific Integration Technique

Background— Human cardiac progenitor cells (hCPCs) are a promising cell source for regenerative repair after myocardial infarction. Exploitation of their full therapeutic potential may require stable genetic modification of the cells ex vivo. Safe genetic engineering of stem cells, using facile methods for site-specific integration of transgenes into known genomic contexts, would significantly enhance the overall safety and efficacy of cellular therapy in a variety of clinical contexts. Methods and Results— We used the phiC31 site-specific recombinase to achieve targeted integration of a triple fusion reporter gene into a known chromosomal context in hCPCs and human endothelial cells. Stable expression of the reporter gene from its unique chromosomal integration site resulted in no discernible genomic instability or adverse changes in cell phenotype. Namely, phiC31-modified hCPCs were unchanged in their differentiation propensity, cellular proliferative rate, and global gene expression profile when compared with unaltered control hCPCs. Expression of the triple fusion reporter gene enabled multimodal assessment of cell fate in vitro and in vivo using fluorescence microscopy, bioluminescence imaging, and positron emission tomography. Intramyocardial transplantation of genetically modified hCPCs resulted in significant improvement in myocardial function 2 weeks after cell delivery, as assessed by echocardiography (P=0.002) and MRI (P=0.001). We also demonstrated the feasibility and therapeutic efficacy of genetically modifying differentiated human endothelial cells, which enhanced hind limb perfusion (P<0.05 at day 7 and 14 after transplantation) on laser Doppler imaging. Conclusions— The phiC31 integrase genomic modification system is a safe, efficient tool to enable site-specific integration of reporter transgenes in progenitor and differentiated cell types.

Early Stem Cell Engraftment Predicts Late Cardiac Functional Recovery: Pre-Clinical Insights from Molecular Imaging

Background— Human cardiac progenitor cells have demonstrated great potential for myocardial repair in small and large animals, but robust methods for longitudinal assessment of their engraftment in humans is not yet readily available. In this study, we sought to optimize and evaluate the use of positron emission tomography (PET) reporter gene imaging for monitoring human cardiac progenitor cell (hCPC) transplantation in a mouse model of myocardial infarction. Methods and Results— hCPCs were isolated and expanded from human myocardial samples and stably transduced with herpes simplex virus thymidine kinase (TK) PET reporter gene. Thymidine kinase-expressing hCPCs were characterized in vitro and transplanted into murine myocardial infarction models (n=57). Cardiac echocardiographic, magnetic resonance imaging and pressure-volume loop analyses revealed improvement in left ventricular contractile function 2 weeks after transplant (hCPC versus phosphate-buffered saline, P<0.03). Noninvasive PET imaging was used to track hCPC fate over a 4-week time period, demonstrating a substantial decline in surviving cells. Importantly, early cell engraftment as assessed by PET was found to predict subsequent functional improvement, implying a “dose–effect” relationship. We isolated the transplanted cells from recipient myocardium by laser capture microdissection for in vivo transcriptome analysis. Our results provide direct evidence that hCPCs augment cardiac function after their transplantation into ischemic myocardium through paracrine secretion of growth factors. Conclusions— PET reporter gene imaging can provide important diagnostic and prognostic information regarding the ultimate success of hCPC treatment for myocardial infarction.

Long noncoding RNA Meg3 regulates cardiomyocyte apoptosis in myocardial infarction

Myocardial infarction (MI), with a major process of cardiomyocyte death, remains a leading cause of morbidity and mortality worldwide. To date, it has been shown that lncRNAs play important roles in cardiovascular pathology. However, the detailed studies on lncRNAs regulating cardiomyocyte death in myocardial infarction are still limited. In this study, we found a progressively upregulated expression of Meg3 in mouse injured heart after MI. Gain-of-function and loss-of-function approaches further revealed pro-apoptotic functions of Meg3 in rodent cardiomyocytes. Moreover, Meg3 was directly upregulated by p53 in hypoxic condition, and involved in apoptotic regulation via its direct binding with RNA-binding protein FUS (fused in sarcoma). Afterwards, adult MI mice that underwent intramyocardial injection with adeno-associated virus serotype 9 (AAV9) system carrying Meg3 shRNA showed a significant improvement of cardiac function. Moreover, we also found that MEG3 was increased in clinical heart failure samples, and had conservatively pro-apoptotic function in human cardiomyocytes that were differentiated from the human embryonic stem cells. Together, these results indicate that p53-induced Meg3–FUS complex plays an important role in cardiomyocyte apoptosis post-MI, and its specific knockdown in cardiomyocytes with AAV9 system represents a promising method to treat MI for preclinical investigation.

Application of Endoscopic Vein Harvesting in Obese Patients Undergoing Coronary Artery Bypass Grafting

SummaryThis study aims to evaluate the clinical outcomes of endoscopic vein harvesting (EVH) for coronary artery bypass grafting (CABG) in obese patients. Totally, 153 obese patients who underwent EVH (n=81) or standard bridging technique (SBT, n=12) in CABG surgery from May 2012 to October 2014 in our hospital were enrolled in this retrospective non-randomized controlled study. The general situation of operation, postoperative complications and short medium-term outcomes were analyzed. The baseline characteristics were similar between these two groups (P>0.05). There were no statistical differences in total operation time (226±28 min vs. 224±30 min, P>0.05), number of damaged vessels (0.12±0.05 vs. 0.16±0.06,P>0.05) and short medium-term outcomes including revascularization rate (1.25% vs. 2.78%, i 0.05), vessel dysfunction rate (11.25% vs. 11.11%,P>0.05) and mortality (0.00% v . 0.00%, P>0.05). Use of EVH was associated with significant reduction of total harvesting time (41 ±6 min vs. 63± 11 min, P<0.05), incision length (4.4±1.1 cm 18.2±4.5 cm, P<0.05) and postoperative lower extremity complications (P<0.05). EVH can reduce the risk of wound complications, whereas does not influence short- and medium-term outcomes in obese patients. It can be considered a reliable procedure of harvesting vessel conduits for obese patients undergoing CABG.

Early Stem Cell Engraftment Predicts Late Cardiac Functional RecoveryClinical Perspective

Background— Human cardiac progenitor cells have demonstrated great potential for myocardial repair in small and large animals, but robust methods for longitudinal assessment of their engraftment in humans is not yet readily available. In this study, we sought to optimize and evaluate the use of positron emission tomography (PET) reporter gene imaging for monitoring human cardiac progenitor cell (hCPC) transplantation in a mouse model of myocardial infarction. Methods and Results— hCPCs were isolated and expanded from human myocardial samples and stably transduced with herpes simplex virus thymidine kinase (TK) PET reporter gene. Thymidine kinase-expressing hCPCs were characterized in vitro and transplanted into murine myocardial infarction models (n=57). Cardiac echocardiographic, magnetic resonance imaging and pressure-volume loop analyses revealed improvement in left ventricular contractile function 2 weeks after transplant (hCPC versus phosphate-buffered saline, P<0.03). Noninvasive PET imaging was used to track hCPC fate over a 4-week time period, demonstrating a substantial decline in surviving cells. Importantly, early cell engraftment as assessed by PET was found to predict subsequent functional improvement, implying a “dose–effect” relationship. We isolated the transplanted cells from recipient myocardium by laser capture microdissection for in vivo transcriptome analysis. Our results provide direct evidence that hCPCs augment cardiac function after their transplantation into ischemic myocardium through paracrine secretion of growth factors. Conclusions— PET reporter gene imaging can provide important diagnostic and prognostic information regarding the ultimate success of hCPC treatment for myocardial infarction.

Early Stem Cell Engraftment Predicts Late Cardiac Functional RecoveryClinical Perspective: Preclinical Insights From Molecular Imaging

Background— Human cardiac progenitor cells have demonstrated great potential for myocardial repair in small and large animals, but robust methods for longitudinal assessment of their engraftment in humans is not yet readily available. In this study, we sought to optimize and evaluate the use of positron emission tomography (PET) reporter gene imaging for monitoring human cardiac progenitor cell (hCPC) transplantation in a mouse model of myocardial infarction. Methods and Results— hCPCs were isolated and expanded from human myocardial samples and stably transduced with herpes simplex virus thymidine kinase (TK) PET reporter gene. Thymidine kinase-expressing hCPCs were characterized in vitro and transplanted into murine myocardial infarction models (n=57). Cardiac echocardiographic, magnetic resonance imaging and pressure-volume loop analyses revealed improvement in left ventricular contractile function 2 weeks after transplant (hCPC versus phosphate-buffered saline, P<0.03). Noninvasive PET imaging was used to track hCPC fate over a 4-week time period, demonstrating a substantial decline in surviving cells. Importantly, early cell engraftment as assessed by PET was found to predict subsequent functional improvement, implying a “dose–effect” relationship. We isolated the transplanted cells from recipient myocardium by laser capture microdissection for in vivo transcriptome analysis. Our results provide direct evidence that hCPCs augment cardiac function after their transplantation into ischemic myocardium through paracrine secretion of growth factors. Conclusions— PET reporter gene imaging can provide important diagnostic and prognostic information regarding the ultimate success of hCPC treatment for myocardial infarction.