Combined transmyocardial revascularization and cell-based angiogenic gene therapy increases transplanted cell survival

Midterm outcomes of transmyocardial laser revascularization with intramyocardial injection of adipose derived stromal cells for severe refractory angina

Introduction

Refractory angina has limited effective therapeutic options and often contributes to frequent hospitalizations, morbidity and impaired quality of life.

Aim

We sought to examine midterm results of a bio-interventional therapy combining transmyocardial laser revascularization (TMLR) and intramyocardial injection of adipose derived stem cells (ADSC) in patients with refractory angina not amenable to percutaneous or surgical revascularization.

Material and methods

We included 15 patients with severe refractory angina and anterior wall ischemia who were ineligible for revascularization strategies. Adipose tissue was harvested and purified, giving the stem cell concentrate. All patients underwent left anterior thoracotomy and TMLR using a low-powered holmium : yttrium–aluminum–garnet laser and intramyocardial injection of ADSC using a combined delivery system.

Results

No deaths or major adverse cardiovascular or cerebrovascular events were observed in the 6-month follow-up. Mean ejection fraction increased from 35% to 38%, and mean Canadian Cardiovascular Society Angina Score decreased from 3.2 to 1.4, with decreased necessity of nitrate usage. Seventy-three percent of patients reported health improvement particularly regarding general health and bodily pain. Improvement in endocardial movement, myocardial thickening and stroke volume index (35.26 to 46.23 ml/m²) on cardiac magnetic resonance imaging (MRI) was observed in 3 patients who had repeat CMR imaging after 6 months.

Conclusions

Our study suggested that interventional therapy combining TMLR with intramyocardial implantation of ADSC may reduce symptoms and improve quality of life in patients with refractory angina. These early findings need further validation in large scale randomized controlled trials.

Remodeling an infarcted heart: novel hybrid treatment with transmyocardial revascularization and stem cell therapy

Transmyocardial revascularization (TMR) has emerged as an additional therapeutic option for patients suffering from diffuse coronary artery disease (CAD), providing immediate angina relief. Recent studies indicate that the volume of surgical cases being performed with TMR have been steadily rising, utilizing TMR as an adjunctive therapy. Therefore the purpose of this review is to provide an up-to-date appreciation of the current state of TMR and its future developmental directions on CAD treatment. The current potential of this therapy focuses on the implementation of stem cells, in order to create a synergistic angiogenic effect while increasing myocardial repair and regeneration. Although TMR procedures provide increased vascularization within the myocardium, patients suffering from ischemic cardiomyopathy may not benefit from angiogenesis alone. Therefore, the goal of introducing stem cells is to restore the functional state of a failing heart by providing these cells with a favorable microenvironment that will enhance stem cell engraftment.

Effect of low-level laser irradiation on oxygen free radicals and ventricular remodeling in the infarcted rat heart

OBJECTIVE

The purpose of this study was to assess the effects of low-level laser irradiation (LLLI) on the expression of oxygen free radicals (OFR) and ventricular remodeling (VR) in the model of rat myocardial infarction (RMMI).

BACKGROUND DATA

LLLI reduces the infarct size and formation of scar tissue in the rat heart after myocardial infarction (MI). However, the exact mechanism has not been demonstrated so far.

METHODS

RMMI was induced by ligating the left anterior descending coronary artery (LAD). After 3 weeks, LLLI (635 nm, 6 mW laser, 7.64 mW/cm(2), 125 sec, 0.96 J/cm(2)) was applied to the surface of heart directly. Four to six rats were euthanized at 1 h, 24 h, 48 h, 72 h, and 1 week after LLLI, and the infarcted myocardia were excised for the measurement of the activity of superoxide dismutase (SOD) and the content of malondialdehyde (MDA). At the end of 4 weeks after MI, the hearts were harvested for histological analysis.

RESULTS

Myocardial SOD activity with LLLI was lower compared with control (p<0.05), and myocardial MDA content with LLLI was higher compared with control (p<0.05), at all the time points. In all rats, the activity of SOD was down to the minimum and the content of MDA was up to the peak at 48 h after laser irradiation. The infarct size was reduced (35±10% vs. 18±9%, p<0.05), the left ventricular wall thickness was increased (0.31±0.03 vs. 0.84±0.02 mm, p<0.05) and the percentage of collagen fibers in the infarcted area was attenuated (64.34±2.20% vs. 30.97±2.60%) by LLLI.

CONCLUSIONS

LLLI could cause OFR accumulation, reduce infarct size, increase ventricular wall thickness, and attenuate the formation of collagen fibers, suggesting the beneficial effects of LLLI on improvement of VR after MI.

The promise and challenges of cardiac stem cell therapy

After an extensive myocardial infarction, restoration of heart function depends on the ability of the heart to promote regeneration and prevent adverse ventricular remodeling. Preclinical research demonstrated that the transplantation of healthy stem cells restored heart function, but the stem cells obtained from older animals or patients were not as efficacious as those from younger individuals. In this paper, we review the successes and limitations discovered in preclinical studies and clinical trials examining cell therapy for damaged hearts. After the modest successes of the early clinical trials, research is now exploring the benefits of enhanced stem cell therapy. Cell based gene therapy markedly improves the angiogenesis achieved. Rejuvenating aged stems cells prior to transplantation restores the functional benefits attained. Transplanting healthy allogeneic stem cells from young donors into aged individuals can restore function if rejection can be prevented. Finally, modulating the cellular environment in aged individuals permits the full functional benefits of stem cell therapy to be realized. Significant challenges remain, but these approaches show promise that cell therapy may become routine therapy to improve functional recovery of older patients after an extensive myocardial infarction.

Myocardial regeneration by transplantation of modified endothelial progenitor cells expressing SDF-1 in a rat model

Cell based therapy has been shown to attenuate myocardial dysfunction after myocardial infarction (MI) in different acute and chronic animal models. It has been further shown that stromal-cell derived factor-1α (SDF-1α) facilitates proliferation and migration of endogenous progenitor cells into injured tissue. The aim of the present study was to investigate the role of exogenously applied and endogenously mobilized cells in a regenerative strategy for MI therapy. Lentivirally SDF-1α-infected endothelial progenitor cells (EPCs) were injected after 90 min. of ligation and reperfusion of the left anterior descending artery (LAD) intramyocardial and intracoronary using a new rodent catheter system. Eight weeks after transplantation, echocardiography and isolated heart studies revealed a significant improvement of LV function after intramyocardial application of lentiviral with SDF-1 infected EPCs compared to medium control. Intracoronary application of cells did not lead to significant differences compared to medium injected control hearts. Histology showed a significantly elevated rate of apoptotic cells and augmented proliferation after transplantation of EPCs and EPCs + SDF-1α in infarcted myocardium. In addition, a significant increased density of CD31⁺ vessel structures, a lower collagen content and higher numbers of inflammatory cells after transplantation of SDF-1 transgenic cells were detectable. Intramyocardial application of lentiviral-infected EPCs is associated with a significant improvement of myocardial function after infarction, in contrast to an intracoronary application. Histological results revealed a significant augmentation of neovascularization, lower collagen content, higher numbers of inflammatory cells and remarkable alterations of apoptotic/proliferative processes in infarcted areas after cell transplantation.

Mesenchymal stem cells overexpressing ephrin-b2 rapidly adopt an early endothelial phenotype with simultaneous reduction of osteogenic potential

Restoration of the vascular supply to ischemic tissues is of high clinical relevance, and proangiogenic therapies aim to reduce morbidity and mortality rates associated with the onset of cardiovascular disease. Stem cell therapy has been proposed as a potentially useful proangiogenic therapy. Mesenchymal stem cells (MSCs) have been shown to be proangiogenic and produce a number of cytokines involved in vessel development and maturation. Preclinical studies have reported increased angiogenesis after MSC delivery to the heart, and similar outcomes have been reported in recent clinical trials. Stem-cell-mediated neovascularization has been augmented by genetic modification with overexpression of angiogenic cytokines, including vascular endothelial growth factor (VEGF) and platelet-derived growth factor, showing promising results. In this study we aimed to enhance the proangiogenic capability of MSCs. MSCs were genetically modified to overexpress a versatile molecule, Ephrin-B2, involved in tissue morphogenesis and vascular development to enhance inherent neovascularization potential. Using nucleofection, Ephrin-B2 was transiently overexpressed on the cell surface of MSCs to recapitulate embryonic signaling and promote neovascularization. Ephrin-B2-expressing MSCs adopted an early endothelial phenotype under endothelial cell culture conditions increasing expression of von Willebrand factor and VEGF-Receptor 2. The cells had an increased ability to form vessel-like structures, produce VEGF, and incorporate into newly formed endothelial cell structures. These data indicate that MSCs expressing Ephrin-B2 represent a novel proangiogenic cell source to promote neovascularization in ischemic tissues.

Intraoperative CD133+ cell transplantation during coronary artery bypass grafting in ischemic cardiomyopathy

If traditional treatment of coronary artery disease has failed, intramyocardial transplantation of CD133+ stem cells with the potential to improve myocardial function is an alternative approach to treating ischemic cardiomyopathy. The INSTEM trial aims at evaluating safety and feasibility of isolation and subsequent intramyocardial transplantation of CD133+ cells in combination with coronary artery bypass grafting (CABG). Patients suffering from severe ischemic cardiomyopathy (ejection fraction ≫15% and ≪35%) are enrolled in this trial. Bone marrow is harvested from the iliac crest and CD133+ cells are purified up to 99%. The myocardial region of interest is pre-treated by transmyocardial laser revascularization in order to trigger homing of transplanted cells. Autologous bone marrow CD133+ cells (up to 30×10(6) cells) are injected into predefined myocardial regions. Cardiac function prior to as well as three, six and 12 months after cell transplantation is assessed by echocardiography. Neither operative mortalities nor any cardiac deaths during follow-up occurred. Left ventricular ejection fraction improved from 25%±5% preoperatively to 40%±8% after six months. Our method of intraoperative CD133+ cell isolation while performing CABG and subsequent transmyocardial cell transplantation is feasible and safe. Although the follow-up has not yet been completed we propose this procedure to be a promising causal therapy of severe ischemic cardiomyopathy.

Low level laser irradiation precondition to create friendly milieu of infarcted myocardium and enhance early survival of transplanted bone marrow cells

We suggested that low-level laser irradiation (LLLI) precondition prior to cell transplantation might remodel the hostile milieu of infarcted myocardium and subsequently enhance early survival and therapeutic potential of implanted bone marrow mesenchymal stem cells (BMSCs). Therefore, in this study we wanted to address: (1) whether LLLI pre-treatment change the local cardiac micro-environment after myocardial infarction (MI) and (2) whether the LLLI preconditions enhance early cell survival and thus improve therapeutic angiogenesis and heart function. MI was induced by left anterior descending artery ligation in female rats. A 635 nm, 5 mW diode laser was performed with energy density of 0.96 J/cm(2) for 150 sec. for the purpose of myocardial precondition. Three weeks later, qualified rats were randomly received with LLLI precondition (n= 26) or without LLLI precondition (n= 27) for LLLI precondition study. Rats that received thoracotomy without coronary ligation were served as sham group (n= 24). In the cell survival study, rats were randomly divided into 4 groups: serum-free culture media injection (n= 8), LLLI precondition and culture media injection (n= 8), 2 million male BMSCs transplantation without LLLI pre-treatment (n= 26) and 2 million male BMSCs transplantation with LLLI precondition (n= 25) group, respectively. Vascular endothelial growth factor (VEGF), glucose-regulated protein 78 (GRP78), superoxide dismutase (SOD) and malondialdehyde (MDA) in the infarcted myocardium were evaluated by Western blotting, real-time PCR and colorimetry, respectively, at 1 hr, 1 day and 1 week after laser irradiation. Cell survival was assayed with quantitative real-time PCR to identify Y chromosome gene and apoptosis was assayed with transferase-mediated dUTP end labelling staining. Capillary density, myogenic differentiation and left ventricular function were tested by immunohistochemistry and echocardiography, respectively, at 1 week. After LLLI precondition, increased VEGF and GRP78 expression, as well as the enhanced SOD activity and inhibited MDA production, was observed. Compared with BMSC transplantation and culture media injection group, although there was no difference in the improved heart function and myogenic differentiation, LLLI precondition significantly enhanced early cell survival rate by 2-fold, decreased the apoptotic percentage of implanted BMSCs in infarcted myocardium and thus increased the number of newly formed capillaries. Taken together, LLLI precondition could be a novel non-invasive approach for intraoperative cell transplantation to enhance cell early survival and therapeutic potential.

Proinflammatory stem cell signaling in cardiac ischemia

Cardiovascular disease remains a leading cause of mortality in developed nations, despite continued advancement in modern therapy. Progenitor and stem cell-based therapy is a novel treatment for cardiovascular disease, and modest benefits in cardiac recovery have been achieved in small clinical trials. This therapeutic modality remains challenged by limitations of low donor-cell survival rates, transient recovery of cardiac function, and the technical difficulty of applying directed cell therapy. Understanding the signaling mechanisms involved in the stem cell response to ischemia has revealed opportunities to modify directly aspects of these pathways to improve their cardioprotective abilities. This review highlights general considerations of stem cell therapy for cardiac disease, reviews the major proinflammatory signaling pathways of mesenchymal stem cells, and reviews ex vivo modifications of stem cells based on these pathways.

Sex of muscle stem cells does not influence potency for cardiac cell therapy

We have previously shown that populations of skeletal muscle-derived stem cells (MDSCs) exhibit sex-based differences for skeletal muscle and bone repair, with female cells demonstrating superior engrafting abilities to males in skeletal muscle while male cells differentiating more robustly toward the osteogenic and chondrogenic lineages. In this study, we tested the hypothesis that the therapeutic capacity of MDSCs transplanted into myocardium is influenced by sex of donor MDSCs or recipient. Male and female MDSCs isolated from the skeletal muscle of 3-week-old mice were transplanted into recipient male or female dystrophin-deficient (mdx) hearts or into the hearts of male SCID mice following acute myocardial infarction. In the mdx model, no difference was seen in engraftment or blood vessel formation based on donor cell or recipient sex. In the infarction model, MDSC-transplanted hearts showed higher postinfarction angiogenesis, less myocardial scar formation, and improved cardiac function compared to vehicle controls. However, sex of donor MDSCs had no significant effects on engraftment, angiogenesis, and cardiac function. VEGF expression, a potent angiogenic factor, was similar between male and female MDSCs. Our results suggest that donor MDSC or recipient sex has no significant effect on the efficiency of MDSC-triggered myocardial engraftment or regeneration following cardiac injury. The ability of the MDSCs to improve cardiac regeneration and repair through promotion of angiogenesis without differentiation into the cardiac lineage may have contributed to the lack of sex difference observed in these models.

Genetic enhancement of stem cell engraftment, survival, and efficacy

Cell-based therapies for the prevention and treatment of cardiac dysfunction offer the potential to significantly modulate cardiac function and improve outcomes in patients with cardiovascular disease. To date several clinical studies have suggested the potential efficacy of several different stem cell types; however, the benefits seen in clinical trials have been inconsistent and modest. In parallel, preclinical studies have identified key events in the process of cell-based myocardial repair, including stem cell homing, engraftment, survival, paracrine factor release, and differentiation that need to be optimized to maximize cardiac repair and function. The inconsistent and modest benefits seen in clinical trials combined with the preclinical identification of mediators responsible for key events in cell-based cardiac repair offers the potential for cell-based therapy to advance to cell-based gene therapy in an attempt to optimize these key events in the hope of maximizing clinical benefit. Below we discuss potential key events in cardiac repair and the mediators of these events that could be of potential interest for genetic enhancement of stem cell-based cardiac repair.

Myocardial repair: from salvage to tissue reconstruction

Cardiac tissue reconstruction following myocardial infarction represents a major challenge in cardiovascular therapy, as current clinical approaches are limited in their ability to regenerate or replace damaged myocardium. Thus, different novel treatments have been introduced aimed at myocardial salvage and repair. Here, we present a review of recent advancements in cardiac cell, gene-based and tissue engineering therapies. Selected strategies in cell therapy and new tools for myocardial gene transfer are summarized. Finally, we consider novel approaches to myocardial tissue engineering as a platform for the integration of various modalities in an attempt to rejuvenate infarcted tissue in vivo.