Comparative effects of mesenchymal progenitor cells, endothelial progenitor cells, or their combination on myocardial infarct regeneration and cardiac function

Co-culture of vascular endothelial cells enhances corticosterone production in steroid hormone-producing cells generated from adipose-derived mesenchymal stromal cells

Cell therapy for adrenocortical insufficiency can potentially provide steroid replacement in response to physiological stimuli. Previously, we reported that adipose tissue-derived stromal cells (ADSCs) are transformed into steroid-producing cells by overexpression of nuclear receptor subfamily 5 group A member 1 (NR5A1). The steroidogenic cells are characterized by the production of both adrenal and gonadal steroids. Cytotherapy for adrenocortical insufficiency requires cells with more adrenocortical characteristics. Considering the highly developed vascular network within the adrenal cortex, all adrenocortical cells are adjacent to and interact with vascular endothelial cells (VECs). In this study, NR5A1-induced steroidogenic cells derived from mouse ADSCs (NR5A1-ADSCs) were co-cultured with mouse VECs. Testosterone secretion in NR5A1-ADSCs was not altered; however, corticosterone secretion significantly increased while levels of steroidogenic enzymes significantly increased in the corticosterone synthesis pathway. Co-culture with lymphatic endothelial cells (LECs) or ADSCs, or transwell culture with NR5A1-ADSCs and VECs did not alter corticosterone production. VECs expressed higher levels of collagen and laminin than LECs. Culture in type-IV collagen and laminin-coated dishes increased corticosterone secretion in NR5A1-ADSCs. These results suggest that VECs may characterize ADSC-derived steroidogenic cells into a more corticosterone-producing phenotype, and VECs may be useful for generating adrenal steroidogenic cells from stem cells.

Iron-Quercetin Complex Preconditioning of Human Peripheral Blood Mononuclear Cells Accelerates Angiogenic and Fibroblast Migration: Implications for Wound Healing

Cell-based therapy is a highly promising treatment paradigm in ischemic disease due to its ability to repair tissue when implanted into a damaged site. These therapeutic effects involve a strong paracrine component resulting from the high levels of bioactive molecules secreted in response to the local microenvironment. Therefore, the secreted therapeutic can be modulated by preconditioning the cells during in vitro culturing. Herein, we investigated the potential use of magnetic resonance imaging (MRI) probes, the "iron-quercetin complex" or IronQ, for preconditioning peripheral blood mononuclear cells (PBMCs) to expand proangiogenic cells and enhance their secreted therapeutic factors. PBMCs obtained from healthy donor blood were cultured in the presence of the iron-quercetin complex. Differentiated preconditioning PBMCs were characterized by immunostaining. An enzyme-linked immunosorbent assay was carried out to describe the secreted cytokines. In vitro migration and tubular formation using human umbilical vein endothelial cells (HUVECs) were completed to investigate the proangiogenic efficacy. IronQ significantly increased mononuclear progenitor cell proliferation and differentiation into spindle-shape-like cells, expressing both hematopoietic and stromal cell markers. The expansion increased the number of colony-forming units (CFU-Hill). The conditioned medium obtained from IronQ-treated PBMCs contained high levels of interleukin 8 (IL-8), IL-10, urokinase-type-plasminogen-activator (uPA), matrix metalloproteinases-9 (MMP-9), and tumor necrosis factor-alpha (TNF-α), as well as augmented migration and capillary network formation of HUVECs and fibroblast cells, in vitro. Our study demonstrated that the IronQ-preconditioning PBMC protocol could enhance the angiogenic and reparative potential of non-mobilized PBMCs. This protocol might be used as an adjunctive strategy to improve the efficacy of cell therapy when using PBMCs for ischemic diseases and chronic wounds. However, in vivo assessment is required for further validation.

Combining stem cells in myocardial infarction: The road to superior repair?

Myocardial infarction irreversibly destroys millions of cardiomyocytes in the ventricle, making it the leading cause of heart failure worldwide. Over the past two decades, many progenitor and stem cell types were proposed as the ideal candidate to regenerate the heart after injury. The potential of stem cell therapy has been investigated thoroughly in animal and human studies, aiming at cardiac repair by true tissue replacement, by immune modulation, or by the secretion of paracrine factors that stimulate endogenous repair processes. Despite some successful results in animal models, the outcome from clinical trials remains overall disappointing, largely due to the limited stem cell survival and retention after transplantation. Extensive interest was developed regarding the combinational use of stem cells and various priming strategies to improve the efficacy of regenerative cell therapy. In this review, we provide a critical discussion of the different stem cell types investigated in preclinical and clinical studies in the field of cardiac repair. Moreover, we give an update on the potential of stem cell combinations as well as preconditioning and explore the future promises of these novel regenerative strategies.

Conditioned medium derived from FGF-2-modified GMSCs enhances migration and angiogenesis of human umbilical vein endothelial cells

BACKGROUND

Angiogenesis plays an important role in tissue repair and regeneration, and conditioned medium (CM) derived from mesenchymal stem cells (MSC-CM) possesses pro-angiogenesis. Nevertheless, the profile and concentration of growth factors in MSC-CM remain to be optimized. Fibroblast growth factor-2 (FGF-2) has been proven to be an effective angiogenic factor. Thus, the aim of this study was to verify whether FGF-2 gene overexpression optimized CM from human gingival mesenchymal stem cells (hGMSCs) and whether such optimized CM possessed more favorable pro-angiogenesis effect.

METHODS

First, FGF-2 gene-modified hGMSCs were constructed using lentiviral transfection technology (LV-FGF-2+-hGMSCs) and the concentration of angiogenesis-related factors in LV-FGF-2+-hGMSC-CM was determined by ELISA. Then, human umbilical vein endothelial cells (HUVECs) were co-cultured for 3 days with LV-FGF-2+-hGMSC-CM, and the expression level of placenta growth factor (PLGF), stem cell factor (SCF), vascular endothelial growth factor receptor 2 (VEGFR2) in HUVECs were determined by qRT-PCR, western blot, and cellular immunofluorescence techniques. The migration assay using transwell and in vitro tube formation experiments on matrigel matrix was conducted to determine the chemotaxis and angiogenesis enhanced by LV-FGF-2+-hGMSC-CM. Finally, NOD-SCID mice were injected with matrigel mixed LV-FGF-2+-hGMSC-CM, and the plug sections were analyzed by immunohistochemistry staining with anti-human CD31 antibody.

RESULTS

LV-FGF-2+-hGMSC-CM contained significantly more FGF-2, vascular endothelial growth factor A (VEGF-A), and transforming growth factor β (TGF-β) than hGMSC-CM. HUVECs pretreated with LV-FGF-2+-hGMSC-CM expressed significantly more PLGF, SCF, and VEGFR2 at gene and protein level than hGMSC-CM pretreated HUVECs. Compared with hGMSC-CM, LV-FGF-2+-hGMSC-CM presented significantly stronger chemotaxis to HUVECs and significantly strengthened HUVECs mediated in vitro tube formation ability. In vivo, LV-FGF-2+-hGMSC-CM also possessed stronger promoting angiogenesis ability than hGMSC-CM.

CONCLUSIONS

Overexpression of FGF-2 gene promotes hGMSCs paracrine of angiogenesis-related growth factors, thereby obtaining an optimized conditioned medium for angiogenesis promotion.

Endothelial progenitor cells promote viability and nerve regenerative ability of mesenchymal stem cells through PDGF-BB/PDGFR-β signaling

Denervation-induced erectile dysfunction (ED) is a prevailing health problem. Our previous study revealed that endothelial progenitor cells (EPCs) promoted the effect of mesenchymal stem cells (MSCs) on restoration of denervation-induced ED in rats. However, underling mechanisms are still largely elusive. In this study, EPCs and MSCs were co-cultured and resorted to co-EPCs and co-MSCs. EPCs-derived paracrine factors containing PDGF-BB (platelet-derived growth factor) were detected, and MSCs were pre-treated with PDGF-BB, while co-MSCs were pre-treated with PDGFR inhibitor AG1296. Either viability or nerve regenerative ability of MSCs was evaluated. In addition, inhibition of either PI3K/Akt or MEK/Erk pathway was performed to evaluate the role of PI3K/Akt and MEK/Erk pathway in PDGF-BB-induced viability of MSCs. The results revealed that PDGF-BB significantly increased the proportion of PDGFR-β⁺ MSCs, and promoted both in-vitro and in-vivo viability, as well as nerve regenerative capacity and erectile function restoration of MSCs in rats. Inhibition of PI3K/Akt, MEK/Erk pathway or mTOR led to decrease of PDGF-BB/PDGFR-β induced viability of MSCs. To our knowledge, our study first demonstrates that EPCs promote viability and potential nerve regenerative ability of MSCs through PDGF-BB/PDGFR-β signaling and its downstream PI3K/Akt and MEK/Erk pathways. mTOR acts as a co-mediator in PI3K/Akt and MEK/Erk pathways.

Combined Transplantation of Mesenchymal Stem Cells and Endothelial Progenitor Cells Restores Cavernous Nerve Injury-Related Erectile Dysfunction

BACKGROUND

Whether combined transplantation of mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) is more effective than transplantation of a single cell type in the restoration of erectile function is unknown.

AIM

To investigate the effect of combined transplantation of MSCs and EPCs on restoration of erectile function in rats with cavernous nerve injury (CNI).

METHODS

MSCs were isolated from human bone marrow and EPCs were isolated from human umbilical cord blood. MSCs and EPCs were identified by flow cytometry and in vitro differentiation or immunofluorescence staining. 25 8-week-old male Sprague-Dawley rats were allocated to 1 of 5 groups: sham operation group, bilateral CNI group receiving periprostatic implantation of MSCs plus EPCs, MSCs, EPCs, or phosphate buffered saline (control group). 2 weeks after CNI and treatment, erectile function of rats was measured by electrically stimulating the CN. The penis and major pelvic ganglia were harvested for histologic examinations. RNA and protein levels of neurotrophin factors (vascular endothelial growth factor, nerve growth factor, and brain-derived neurotrophic factor) in mono- or coculture MSCs and EPCs were assessed by real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively.

OUTCOMES

Intracavernous pressure and mean arterial pressure were measured to evaluate erectile function. Histologic examinations of the penis and major pelvic ganglia and RNA and protein levels of neurotrophin factors in MSCs and EPCs were performed.

RESULTS

MSCs and EPCs expressed the specified cell markers and exhibited the typical appearance and characteristics. Treatments using MSCs and/or EPCs could increase endothelial and smooth muscle contents of the corpus cavernosum, decrease caspase-3 expression and increase penile neuronal nitric oxide synthase expression, and restore the neural component of the major pelvic ganglia in rats with CNI. Combined transplantation of MSCs and EPCs had a better effect on improving erectile function than single transplantation of MSCs or EPCs. Expression levels of vascular endothelial growth factor and nerve growth factor in coculture MSCs and EPCs were significantly higher than those of primary MSCs or EPCs.

CLINICAL TRANSLATION

Combined transplantation of MSCs and EPCs was more effective in restoring erectile function in CNI-related erectile dysfunction models.

STRENGTHS AND LIMITATIONS

The study, for the 1st time, proved that combined transplantation of MSCs and EPCs was more effective in restoring erectile function in rats with CNI. The rat model might not represent the human condition.

CONCLUSION

Combined periprostatic transplantation of MSCs and EPCs could restore erectile function in rats with CNI more effectively. MSCs might restore CN fibers by secreting neurotrophin factors such as vascular endothelial growth factor and nerve growth factor, and EPCs could enhance the paracrine activity of MSCs. Fang J-f, Huang X-n, Han X-y, et al. Combined Transplantation of Mesenchymal Stem Cells and Endothelial Progenitor Cells Restores Cavernous Nerve Injury-Related Erectile Dysfunction. J Sex Med 2018;15:284-295.

Tissue Engineering of the Microvasculature

The ability to generate new microvessels in desired numbers and at desired locations has been a long-sought goal in vascular medicine, engineering, and biology. Historically, the need to revascularize ischemic tissues nonsurgically (so-called therapeutic vascularization) served as the main driving force for the development of new methods of vascular growth. More recently, vascularization of engineered tissues and the generation of vascularized microphysiological systems have provided additional targets for these methods, and have required adaptation of therapeutic vascularization to biomaterial scaffolds and to microscale devices. Three complementary strategies have been investigated to engineer microvasculature: angiogenesis (the sprouting of existing vessels), vasculogenesis (the coalescence of adult or progenitor cells into vessels), and microfluidics (the vascularization of scaffolds that possess the open geometry of microvascular networks). Over the past several decades, vascularization techniques have grown tremendously in sophistication, from the crude implantation of arteries into myocardial tunnels by Vineberg in the 1940s, to the current use of micropatterning techniques to control the exact shape and placement of vessels within a scaffold. This review provides a broad historical view of methods to engineer the microvasculature, and offers a common framework for organizing and analyzing the numerous studies in this area of tissue engineering and regenerative medicine. © 2019 American Physiological Society. Compr Physiol 9:1155-1212, 2019.

STAT3 Phosphorylation Mediating DMSO's Function on Fetal Cardiomyocyte Proliferation with Developmental Changes

Endogenous cardiac regeneration has been focused for decades as a potential therapy for heart diseases with cell loss, and dimethyl sulfoxide (DMSO) has been proposed as a treatment for many diseases. In this study, we aimed to investigate the function of DMSO on fetal cardiomyocyte proliferation. By tracing BrdU⁺/α actinin⁺ cells or Ki67⁺/α actinin⁺ cells with immunohistochemical staining, we found that DMSO remarkably promoted fetal cardiomyocytes proliferation, and at the late developmental stage (LDS), such effects were more efficient than that at early developmental stage (EDS). Western blot data revealed a significant increase in STAT3 phosphorylation under DMSO treatments at LDS, while not at EDS. Consistently, STAT3 phosphorylation blocker STA21 could greatly reverse DMSO's function at LDS whereas hardly at EDS. Moreover, hearts at the EDS had less total STAT3 protein, but relatively much higher level of phosphorylated STAT3. This suggests that DMSO promote fetal cardiomyocytes proliferation, and STAT3 phosphorylation play a pivotal role in DMSO's function. With maturation, DMSO exerted a better ability to favor cardiomyocyte proliferation depending on STAT3 phosphorylation. Therefore, DMSO could serve as an effective, economic, and safe therapy for heart diseases with cell loss.

Expanded CD133+ Cells from Human Umbilical Cord Blood Improved Heart Function in Rats after Severe Myocardial Infarction

Pharmacological approaches are partially effective in limiting infarct size. Cell therapies using a cell population enriched with endothelial progenitor cells (EPCs) CD133⁺ have opened new perspectives for the treatment of ischemic areas after infarction. This preclinical study evaluated the effect of intramyocardial transplantation of purified or expanded human umbilical cord blood-derived CD133⁺ cells on the recovery of rats following acute myocardial infarction (AMI). Histology studies, electrocardiogram, and fluorescence in situ hybridization (FISH) were used to evaluate heart recovery. Purified CD133⁺ cells, enriched in endothelial progenitor cells, when expanded in vitro acquired an endothelial-like cell phenotype expressing CD31 and von Willebrand factor (vWF). The group of infarcted rats that received expanded CD133⁺ cells had a more significant recovery of contraction performance and less heart remodeling than the group that received purified CD133⁺ cells. Either purified or expanded CD133⁺ cells were able to induce neovascularization in the infarcted myocardium in an equivalent manner. Few human cells were detected in the infarcted myocardium of the rats 28 days after transplantation suggesting that the effects observed might be related primarily to paracrine activity. Although both cell populations ameliorated the infarcted heart and are suitable for regeneration of the vascular system, expanded CD133⁺ cells are more beneficial and promising candidates for vascular regeneration.

Shear stress: An essential driver of endothelial progenitor cells

The blood flow through vessels produces a tangential, or shear, stress sensed by their innermost layer (i.e., endothelium) and representing a major hemodynamic force. In humans, endothelial repair and blood vessel formation are mainly performed by circulating endothelial progenitor cells (EPCs) characterized by a considerable expression of vascular endothelial growth factor receptor 2 (VEGFR2), CD34, and CD133, pronounced tube formation activity in vitro, and strong reendothelialization or neovascularization capacity in vivo. EPCs have been proposed as a promising agent to induce reendothelialization of injured arteries, neovascularization of ischemic tissues, and endothelialization or vascularization of bioartificial constructs. A number of preconditioning approaches have been suggested to improve the regenerative potential of EPCs, including the use of biophysical stimuli such as shear stress. However, in spite of well-defined influence of shear stress on mature endothelial cells (ECs), articles summarizing how it affects EPCs are lacking. Here we discuss the impact of shear stress on homing, paracrine effects, and differentiation of EPCs. Unidirectional laminar shear stress significantly promotes homing of circulating EPCs to endothelial injury sites, induces anti-thrombotic and anti-atherosclerotic phenotype of EPCs, increases their capability to form capillary-like tubes in vitro, and enhances differentiation of EPCs into mature ECs in a dose-dependent manner. These effects are mediated by VEGFR2, Tie2, Notch, and β1/3 integrin signaling and can be abrogated by means of complementary siRNA/shRNA or selective pharmacological inhibitors of the respective proteins. Although the testing of sheared EPCs for vascular tissue engineering or regenerative medicine applications is still an unaccomplished task, favorable effects of unidirectional laminar shear stress on EPCs suggest its usefulness for their preconditioning.

Specific recruitment of circulating angiogenic cells using biomaterials as filters

Endogenous recruitment of circulating angiogenic cells (CACs) is an emerging strategy to induce angiogenesis within a defect site, and multiple recent strategies have deployed soluble protein releasing biomaterials for this purpose. However, the way in which the design of biomaterials affects CAC recruitment and invasion are poorly understood. Here we used an enhanced-throughput cell invasion assay to systematically examine the effects of biomaterial design on CAC recruitment. The screens co-optimized hydrogel presentation of a stromal-derived factor-1α (SDF-1α) gradient, hydrogel degradability, and hydrogel stiffness for maximal CAC invasion. We also examined the specificity of this invasion by assessing dermal fibroblast, mesenchymal stem cell, and lymphocyte invasion individually and in co-culture with CACs to identify hydrogels specific to CAC invasion. These screens suggested a subset of MMP-degradable hydrogels presenting a specific range of SDF-1α gradient slopes that induced specific invasion of CACs, and we posit that the design parameters of this subset of hydrogels may serve as instructive templates for the future design of biomaterials to specifically recruit CACs. We also posit that this design concept may be applied more broadly in that it may be possible to utilize these specific subsets of biomaterials as "filters" to control which types of cell populations invade into and populate the biomaterial.

STATEMENT OF SIGNIFICANCE

The recruitment of specific cell types for cell-based therapies in vivo is of great interest to the regenerative medicine community. Circulating angiogenic cells (CACs), CD133+ cells derived from the blood stream, are of particular interest for induction of angiogenesis in ischemic tissues, and recent studies utilizing soluble-factor releasing biomaterials to recruit these cells in vivo show great promise. However, these studies are largely "proof of concept" and are not systematic in nature. Thus, little is currently known about how biomaterial design affects the recruitment of CACs. In the present work, we use a high throughput cell invasion screening platform to systematically examine the effects of biomaterial design on circulating angiogenic cell (CAC) recruitment, and we successfully screened 263 conditions at 3 replicates each. Our results identify a particular subset of conditions that robustly recruit CACs. Additionally, we found that these conditions also specifically recruited CACs and excluded the other tested cells types of dermal fibroblasts, mesenchymal stem cells, and lymphocytes. This suggests an intriguing new role for biomaterials as "filters" to control the types of cells that invade and populate that biomaterial.

Optimizing the host substrate environment for cardiac angiogenesis, arteriogenesis, and myogenesis

INTRODUCTION

The diseased host milieu, such as endothelial dysfunction (ED), decreased NO bioavailability, and ischemic/inflammatory post-MI environment, hamper the clinical success of existing cardiac regenerative therapies. Area covered: In this article, current strategies including pharmacological and nonpharmacological approaches for improving the diseased host milieu are reviewed. Specifically, the authors provide focus on: i) the mechanism of ED in patients with cardiovascular diseases, ii) the current results of ED improving strategies in pre-clinical and clinical studies, and iii) the use of biomaterials as a novel modulator in damaged post-MI environment. Expert opinion: Adjunct therapies which improve host endothelial function have demonstrated promising outcomes, potentially overcoming disappointing results of cell therapy in human studies. In the future, elucidation of the interactions between the host tissue and therapeutic agents, as well as downstream signaling pathways, will be the next challenges in enhancing regenerative therapy. More careful investigations are also required to establish these agents' safety and efficacy for wide usage in humans.

Current State of Stem Cell Therapy for Ischemic Heart Disease

Improvements in the care of patients with ischemic cardiovascular disease have led to improved survival but also a burgeoning population of patients with advanced ischemic heart disease. Cell therapies offer a novel approach toward cardiac "rejuvenation" via stimulation of new blood vessel growth, enhancing tissue perfusion, and via preservation or even regeneration of myocardial tissue, leading to improvements in cardiac performance after myocardial infarction and in patients with advanced heart failure. Here, we summarize and offer some thoughts on the state of the field of cell therapy for ischemic heart disease, targeting three separate conditions that have been the subject of significant clinical research: enhancing left ventricular recovery after MI, improving outcomes and symptoms in patients with congestive heart failure (CHF), and treatment of patients with refractory angina, despite maximal medical therapy.

Combined transplantation of mesenchymal stem cells and endothelial progenitor cells for tissue engineering: a systematic review and meta-analysis

BACKGROUND

Combined cell implantation has been widely applied in tissue engineering in recent years. In this meta-analysis, we aimed to establish whether the combined transplantation of mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) promotes angiogenesis and tissue repair, compared with transplantation of a single cell type, following tissue injury or during tissue regeneration.

METHODS

The electronic databases PubMed, EMBASE, MEDLINE, Chinese Biomedical Literature, and China National Knowledge Infrastructure were searched in this systematic review and meta-analysis. Eighteen controlled preclinical studies involving MSC and EPC transplantation in animal models of disease, or in coculture in vitro, were included in this review. The vessel density and other functional indexes, which were classified according to the organ source, were used to evaluate the efficiency of cotransplantation. Publication bias was assessed.

RESULTS

There was no obvious difference in angiogenesis following combined cell transplantation (EPCs and MSCs) and transplantation of EPCs alone; however, an improvement in the function of damaged organs was observed following cotransplantation. In addition, combined cell transplantation significantly promoted tissue recovery in cardiovascular disease, cerebrovascular disease, and during bone regeneration. Compared with combined transplantation (EPCs and MSCs) and transplantation of MSCs alone, cotransplantation significantly promoted angiogenesis and bone regeneration, as well as vessel revascularization and tissue repair in cerebrovascular disease; however, no obvious effects on cardiovascular disease were observed.

CONCLUSIONS

As an exploratory field in the discipline of tissue engineering, MSC and EPC cotransplantation offers advantages, although it is essential to assess the feasibility of this approach before clinical trials can be performed.

Nanoparticle drug delivery systems and their use in cardiac tissue therapy

Cardiovascular diseases make up one of the main causes of death today, with myocardial infarction and ischemic heart disease contributing a large share of the deaths reported. With mainstream clinical therapy focusing on palliative medicine following myocardial infarction, the structural changes that occur in the diseased heart will eventually lead to end-stage heart failure. Heart transplantation remains the only gold standard of cure but a shortage in donor organs pose a major problem that led to clinicians and researchers looking into alternative strategies for cardiac repair. This review will examine some alternative methods of treatment using chemokines and drugs carried by nanoparticles as drug delivering agents for the purposes of treating myocardial infarction through the promotion of revascularization. We will also provide an overview of existing studies involving such nanoparticulate drug delivery systems, their reported efficacy and the challenges facing their translation into ubiquitous clinical use.

Nicorandil enhances the efficacy of mesenchymal stem cell therapy in isoproterenol-induced heart failure in rats

Stem cell transplantation has emerged as a promising technique for regenerative medicine in cardiovascular therapeutics. However, the results have been less than optimal. The aim of the present study was to investigate whether nicorandil could offer an additional benefit over bone marrow-derived mesenchymal stem cell therapy in isoproterenol-induced myocardial damage and its progression to heart failure in rats. Isoproterenol was injected subcutaneously for 2 consecutive days at doses of 85 and 170 mg/kg/day, respectively. Nicorandil (3 mg/kg/day) was then given orally with or without a single intravenous bone marrow-derived mesenchymal stem cell administration. Electrocardiography and echocardiography were recorded 2 weeks after the beginning of treatment. Rats were then sacrificed and the ventricle was isolated for estimation of tumor necrosis factor-alpha, vascular endothelial growth factor and transforming growth factor-beta. Moreover, protein expressions of caspase-3, connexin-43 as well as endothelial and inducible nitric oxide synthases were evaluated. Finally, histological studies of myocardial fibrosis and blood vessel density were performed and cryosections were done for estimation cell homing. Combined nicorandil/bone marrow-derived mesenchymal stem cell therapy provided an additional improvement compared to cell therapy alone toward reducing isoproterenol-induced cardiac hypertrophy, fibrosis and inflammation. Notably, combined therapy induced significant increase in angiogenesis and cell homing and prevented isoproterenol-induced changes in contractility and apoptotic markers. In conclusion, combined nicorandil/bone marrow-derived mesenchymal stem cell therapy was superior to cell therapy alone toward preventing isoproterenol-induced heart failure in rats through creation of a supportive environment for mesenchymal stem cells.

Mesenchymal stem cells alleviate airway inflammation and emphysema in COPD through down-regulation of cyclooxygenase-2 via p38 and ERK MAPK pathways

Bone marrow-derived mesenchymal stem cells (MSCs) have been identified as one possible strategy for the treatment of chronic obstructive pulmonary disease (COPD). Our previous studies have demonstrated that MSC administration has therapeutic potential in airway inflammation and emphysema via a paracrine mechanism. We proposed that MSCs reverse the inflammatory process and restore impaired lung function through their interaction with macrophages. In our study, the rats were exposed to cigarette smoke (CS), followed by the administration of MSCs into the lungs for 5 weeks. Here we show that MSC administration alleviated airway inflammation and emphysema through the down-regulation of cyclooxygenase-2 (COX-2) and COX-2-mediated prostaglandin E2 (PGE2) production, possibly through the effect on alveolar macrophages. In vitro co-culture experiments provided evidence that MSCs down-regulated COX-2/PGE2 in macrophages through inhibition of the activation-associated phosphorylation of p38 MAPK and ERK. Our data suggest that MSCs may relieve airway inflammation and emphysema in CS-exposed rat models, through the inhibition of COX-2/PGE2 in alveolar macrophages, mediated in part by the p38 MAPK and ERK pathways. This study provides a compelling mechanism for MSC treatment in COPD, in addition to its paracrine mechanism.

Direct intracardiac injection of umbilical cord-derived stromal cells and umbilical cord blood-derived endothelial cells for the treatment of ischemic cardiomyopathy

The development of new therapeutic strategies is necessary to reduce the worldwide social and economic impact of cardiovascular disease, which produces high rates of morbidity and mortality. A therapeutic option that has emerged in the last decade is cell therapy. The aim of this study was to compare the effect of transplanting human umbilical cord-derived stromal cells (UCSCs), human umbilical cord blood-derived endothelial cells (UCBECs) or a combination of these two cell types for the treatment of ischemic cardiomyopathy (IC) in a Wistar rat model. IC was induced by left coronary artery ligation, and baseline echocardiography was performed seven days later. Animals with a left ventricular ejection fraction (LVEF) of ≤40% were selected for the study. On the ninth day after IC was induced, the animals were randomized into the following experimental groups: UCSCs, UCBECs, UCSCs plus UCBECs, or vehicle (control). Thirty days after treatment, an echocardiographic analysis was performed, followed by euthanasia. The animals in all of the cell therapy groups, regardless of the cell type transplanted, had less collagen deposition in their heart tissue and demonstrated a significant improvement in myocardial function after IC. Furthermore, there was a trend of increasing numbers of blood vessels in the infarcted area. The median value of LVEF increased by 7.19% to 11.77%, whereas the control group decreased by 0.24%. These results suggest that UCSCs and UCBECs are promising cells for cellular cardiomyoplasty and can be an effective therapy for improving cardiac function following IC.

Stem cell therapy for cardiovascular disease: the demise of alchemy and rise of pharmacology

Regenerative medicine holds great promise as a way of addressing the limitations of current treatments of ischaemic disease. In preclinical models, transplantation of different types of stem cells or progenitor cells results in improved recovery from ischaemia. Furthermore, experimental studies indicate that cell therapy influences a spectrum of processes, including neovascularization and cardiomyogenesis as well as inflammation, apoptosis and interstitial fibrosis. Thus, distinct strategies might be required for specific regenerative needs. Nonetheless, clinical studies have so far investigated a relatively small number of options, focusing mainly on the use of bone marrow-derived cells. Rapid clinical translation resulted in a number of small clinical trials that do not have sufficient power to address the therapeutic potential of the new approach. Moreover, full exploitation has been hindered so far by the absence of a solid theoretical framework and inadequate development plans. This article reviews the current knowledge on cell therapy and proposes a model theory for interpretation of experimental and clinical outcomes from a pharmacological perspective. Eventually, with an increased association between cell therapy and traditional pharmacotherapy, we will soon need to adopt a unified theory for understanding how the two practices additively interact for a patient's benefit.

Preclinical evaluation of biopolymer-delivered circulating angiogenic cells in a swine model of hibernating myocardium

BACKGROUND

Vasculogenic cell-based therapy combined with tissue engineering is a promising revascularization approach targeted at patients with advanced coronary artery disease, many of whom exhibit myocardial hibernation. However, to date, no experimental data have been available in this context; we therefore examined the biopolymer-supported delivery of circulating angiogenic cells using a clinically relevant swine model of hibernating myocardium.

METHODS AND RESULTS

Twenty-five swine underwent placement of an ameroid constrictor on the left circumflex artery. After 2 weeks, animals underwent echocardiography, rest and stress ammonia-positron emission tomography perfusion, and fluorodeoxyglucose positron emission tomography viability scans. The following week, swine were randomized to receive intramyocardial injections of PBS control (n=10), circulating angiogenic cells (n=8), or circulating angiogenic cells+collagen-based matrix (n=7). The imaging protocol was repeated after 7 weeks. Baseline positron emission tomography myocardial blood flow and myocardial flow reserve were reduced in the left circumflex artery territory (both P<0.001), and hibernation (mismatch) was observed. At follow-up, stress myocardial blood flow had increased (P≤0.01) and hibernation decreased (P<0.01) in the cells+matrix group only. Microsphere-measured myocardial blood flow validated the perfusion results. Arteriole density and wall motion abnormalities improved in the cells+matrix group. There was also a strong trend toward an improvement in ejection fraction (P=0.07).

CONCLUSIONS

In this preclinical swine model of ischemic and hibernating myocardium, the combined delivery of circulating angiogenic cells and a collagen-based matrix restored perfusion, reduced hibernation, and improved myocardial wall motion.

Injectable small intestine submucosal extracellular matrix in an acute myocardial infarction model

BACKGROUND

The mechanisms involved in myocardial regeneration and cardiac remodeling were examined by injecting porcine-derived small intestine submucosal extracellular matrix (SIS-ECM), with and without circulating angiogenic cells (CACs), in a mouse model of acute myocardial infarction (MI).

METHODS

Nine- to 10-week-old female C57BL/6J mice had the left anterior descending (LAD) coronary artery ligated. Seven days after ligation, 38 randomly allocated animals received echocardiographically guided intramyocardial injections of phosphate buffered saline (PBS), CACs, SIS-ECM, or SIS-ECM + CACs. Repeated echocardiography and immunohistochemical analysis were performed at 28 days after ligation.

RESULTS

Baseline postligation left ventricular ejection fraction (LVEF) was equivalent in all groups. Twenty-one days after treatment, ejection fraction improved in the SIS-ECM + CAC treatment group (by 38% ± 2.12%) and the SIS-ECM treatment group (by 36% ± 3.71%), compared with the CAC-alone and PBS treatment groups (p < 0.1). Masson's trichrome staining showed reduced infarct size in SIS-ECM + CACs (34.2% ± 3.1%) and SIS-ECM alone (34.5% ± 4.7%) compared with CACs alone (47.3% ± 6.0%) and PBS (61.9% ± 5.5%; p < 0.002). Arteriolar density in periinfarct regions was enhanced in both SIS-ECM-treated groups (by ≥ 78% ± 7%; p = 0.03). More GATA4- and β-catenin-positive cardiac cells were found in the myocardium of SIS-ECM-treated animals.

CONCLUSIONS

Intramyocardial delivery of SIS-ECM 7 days after MI in a mouse model reduced infarct size and improved myocardial vessel density and function; when combined with CACs it helped restore myocardial cellularity, suggesting a potential therapeutic role for SIS-ECM in cardiac regeneration.

Ex vivo Akt/HO-1 gene therapy to human endothelial progenitor cells enhances myocardial infarction recovery

The aim of this study was to evaluate the overexpression of genes central to cell survival and angiogenesis to enhance the function of human late outgrowth endothelial progenitor cells (EPCs) and their utility for infarct recovery. Ischemic myocardial injury creates a hostile microenvironment, which is characterized by hypoxia, oxidative stress, and inflammation. The infarct microenvironment prevents adhesion, survival, and integration of cell transplants that promote neovascularization. EPCs are dysfunctional as a result of risk factors in cardiovascular patients. Protein kinase B (Akt) and heme-oxygenase-1 (HO-1) are intracellular proteins that play an important role in angiogenesis and cell survival. Late outgrowth EPCs transduced ex vivo with Akt and HO-1 demonstrate improved adhesion to extracellular matrix, improved migration toward human cardiomyocytes, and an improved paracrine profile under stress. Enhanced late outgrowth EPCs reduce the tumor necrosis factor-α (TNF-α) burden both in vitro and in vivo, attenuating nuclear factor-κB (NF-κB) activity and promoting cell survival. Akt and HO-1 enhance late outgrowth EPC neovascularization, resulting in improved cardiac performance and reduced negative remodeling after myocardial infarction in nude mice. Alteration of the infarct microenvironment through gene modification of human late outgrowth EPCs enhances the function and integration of transplanted cells for restoration of cardiac function.

Shock wave treatment induces angiogenesis and mobilizes endogenous CD31/CD34-positive endothelial cells in a hindlimb ischemia model: implications for angiogenesis and vasculogenesis

OBJECTIVES

Shock waves have been shown to induce recruitment of intravenously injected endothelial progenitor cells to ischemic hind limbs in rats. We hypothesized that shock wave treatment as sole therapy would induce angiogenesis in this ischemia model and would lead to mobilization of endogenous endothelial (progenitor) cells.

METHODS

A total of 18 rats, aged 5 weeks old, were subdivided into 3 groups: sham (n = 6), ischemic muscle with shock wave treatment (shock wave treatment group, n = 6), and without shock wave treatment (control, n = 6). Hind limb ischemia was induced by ligation of the femoral artery. Three weeks later, shock wave treatment (300 impulses at 0.1 mJ/mm(2)) was applied to the adductor muscle; the controls were left untreated. Muscle samples were analyzed using real-time polymerase chain reaction for angiogenic factors and chemoattractants for endothelial progenitor cell mobilization. Fluorescence activated cell sorting analysis of the peripheral blood was performed for CD31/CD34-positive cells. Perfusion was measured using laser Doppler imaging. Functional improvement was evaluated by walking analysis.

RESULTS

Angiogenic factors/endothelial progenitor cell chemoattractants, stromal cell-derived factor-1 and vascular endothelial growth factor, were increased in the treatment group, as shown by real-time polymerase chain reaction, indicating the mobilization of endothelial progenitor cells. Fluorescence activated cell sorting analysis of the peripheral blood revealed high numbers of CD31/CD34-positive cells in the treatment group. Greater numbers of capillaries were found in the treated muscles. Blood perfusion increased markedly in the treatment group and led to functional restoration, as shown by the results from the walking analysis.

CONCLUSIONS

Shock wave therapy therefore could develop into a feasible alternative to stem cell therapy in regenerative medicine, in particular for ischemic heart and limb disease.

Cell-based vasculogenic studies in preclinical models of chronic myocardial ischaemia and hibernation

INTRODUCTION

Coronary artery disease commonly leads to myocardial ischaemia and hibernation. Relevant preclinical models of these conditions are essential to evaluate new therapeutic options such as cell-based vasculogenic therapies.

AREAS COVERED

In this article, the authors first review basic concepts of myocardial ischaemia/hibernation and relevant techniques to assess myocardial viability. Then, preclinical models of chronic myocardial ischaemia and hibernation, induced by devices such as ameroid constrictors, Delrin stenosis, hydraulic occluders, and coils/stents are described. Lastly, the authors discuss cell-based vasculogenic therapy, and summarise studies conducted in large animal models of chronic myocardial ischaemia and hibernation.

EXPERT OPINION

Approximately one-third of patients with viable myocardium do not undergo revascularisation; however, this population is at high risk for cardiac events and would surely benefit from effective cell-based therapy. Because of the modest benefits in clinical studies, preclinical models accurately representing clinical myocardial ischemia/hibernation are necessary to better understand and appropriately direct regenerative therapy research.

18F-FDG Cell Labeling May Underestimate Transplanted Cell Homing: More Accurate, Efficient, and Stable Cell Labeling with Hexadecyl-4-[18F]Fluorobenzoate for in Vivo Tracking of Transplanted Human Progenitor Cells by Positron Emission Tomography

Cell therapy is expected to restore perfusion and improve function in the ischemic/infarcted myocardium; however, the biological mechanisms and local effects of transplanted cells remain unclear. To assess cell fate in vivo, hexadecyl-4-[18F]fluorobenzoate (18F-HFB) cell labeling was evaluated for tracking human circulating progenitor cells (CPCs) with positron emission tomography (PET) and was compared to the commonly used 2-[18F]fluoro-2-deoxy-d-glucose (18F-FDG) labeling method in a rat myocardial infarction model. CPCs were labeled with 18F-HFB or 18F-FDG ex vivo under the same conditions. 18F-HFB cell-labeling efficiency (23.4 ± 7.5%) and stability (4 h, 88.4 ± 6.0%) were superior to 18F-FDG (7.6 ± 4.1% and 26.6 ± 6.1%, respectively; p < 0.05). Neither labeling approach significantly altered cell viability, phenotype or migration potential up to 24 h postlabeling. Two weeks after left anterior descending coronary artery ligation, rats received echo-guided intramyocardial injection in the infarct border zone with 18F-HFB-CPCs, 18F-FDG-CPCs, 18F-HFB, or 18F-FDG. Dynamic PET imaging of both 18F-HFB-CPCs and 18F-FDG-CPCs demonstrated that only 16–37% of the initial injection dose (ID) was retained in the injection site at 10 min postdelivery, and remaining activity fell significantly over the first 4 h posttransplantation. The 18F-HFB-CPC signal in the target area at 2 h (23.7 ± 14.7% ID/g) and 4 h (17.6 ± 13.3% ID/g) postinjection was greater than that of 18F-FDG-CPCs (5.4 ± 2.3% ID/g and 2.6 ± 0.7% ID/g, respectively; p < 0.05). Tissue biodistribution confirmed the higher radioactivity in the border zone of 18F-HFB-CPC rats. Immunostaining of heart tissue sections revealed no significant difference in cell retention between two labeled cell transplantation groups. Good correlation with biodistribution results was observed in the 18F-HFB-CPC rats ( r = 0.81, p < 0.05). Compared to 18F-FDG, labeling human CPCs with 18F-HFB provides a more efficient, stable, and accurate way to quantify the distribution of transplanted cells. 18F-HFB cell labeling with PET imaging offers a better modality to enhance our understanding of early retention, homing, and engraftment with cardiac cell therapy.

Impairment of human cell-based vasculogenesis in rats by hypercholesterolemia-induced endothelial dysfunction and rescue with L-arginine supplementation

OBJECTIVE

Clinical efficacy of cardiac cell therapy may be compromised by its target population, patients with endothelial dysfunction. In vivo inhibition by endothelial dysfunction has been demonstrated for protein angiogenesis but remains unclear for cell therapy. We examined whether hypercholesterolemia inhibits vasculogenic effects of transplanted human circulating progenitor cells in ischemic tissue and whether L-arginine, a nitric oxide donor, might prevent impairment.

METHODS

Athymic rats were fed either normal (group A) or high-cholesterol diets, the latter without (group B) or with (group C) oral L-arginine supplementation. Two weeks later, these rats underwent left femoral artery ligation followed by injection of 2 x 10(6) human circulating progenitor cells into left hind-limb muscle. A fourth group (group D) received supplemented high-cholesterol diets but no cells.

RESULTS

Group B had biochemical evidence of endothelial dysfunction and reduced tissue endothelial nitric oxide synthase expression, whereas group A levels were the same as in group C. By 21 postoperative days, left hind-limb perfusion had recovered fully in groups A and C, partially in D, and not at all in B (38% lower than group A, P < or = .004). Lower arteriolar densities were found in groups and B and D than in groups A and C (P < or = .02). Engrafted human cell numbers were equivalent in all cell-transplanted groups after 3 weeks.

CONCLUSIONS

Endothelial dysfunction inhibited effects of cell therapy, specifically vasculogenesis, suggesting a role for substrate modification to overcome this inhibition. Involved mechanisms appear related to use of cells but not engraftment and require further investigation.

In vitro functional comparison of therapeutically relevant human vasculogenic progenitor cells used for cardiac cell therapy

OBJECTIVE

In cardiac cell therapy almost every cell type tested experimentally has yielded some benefit. However, there is a lack of studies directly comparing the function of various stem/progenitor cell populations. This study describes the expansion of peripheral blood CD133(+) cells and compares their functional properties with those of other commonly used human progenitor cell populations.

METHODS

CD133(+) cells were generated from the CD133(-) fraction of peripheral blood, either serially (pooled-derived) or after 14 days of culture (derived). Their phenotypic, migratory, and vasculogenic properties were compared with those of 4 commonly used progenitor cell populations in vitro.

RESULTS

Serial expansion resulted in an 11-fold increase in the number of CD133(+) cells. The proportion of derived CD133(+) cells collected between 0 and 8 days also expressing CD34 and vascular endothelial growth factor receptor 2 was similar (approximately 60%, P = .41). Adherent, 4-day cultured endothelial progenitor cells demonstrated enhanced migration compared with each of the other 5 cell populations (all P < or = .002). The migration of derived CD133(+) progenitors was enhanced by coculture with CD133(-) cells or their supernatant (P < .05). In vitro vasculogenesis assays revealed that derived and pooled-derived CD133(+) cells had superior vasculogenic potential compared with other progenitor populations (P < or = .03).

CONCLUSIONS

A novel source of expandable CD133(+) cells can be generated from the CD133(-) fraction of peripheral blood. The CD133 phenotypic marker translates into the cell being vasculogenically more potent in vitro, which could be beneficial to inducing vasculogenesis in the ischemic heart. Furthermore, intercellular interactions appear important for improving the therapeutic efficacy of cell transplantation.

Cell therapies for therapeutic angiogenesis: back to the bench

The discovery, over a decade ago, of endothelial progenitor cells that are able to participate in neovascularization of adult tissue has been greeted enthusiastically because of the potential for new cell-based therapies for therapeutic angiogenesis. Since that time, an ever-growing list of candidate cells has been proposed for cardiovascular regeneration. However, to date, pre-clinical and clinical studies evaluating the therapeutic potential of various cell therapies have reported conflicting results, generating controversy. Key issues within the field of cell therapy research include a lack of uniform cellular definitions, as well as inadequate functional characterization of the role of putative stem/progenitor cells in angiogenesis. Given the mixed results of initial clinical studies, there is now a scientific imperative to understand better the vascular biology of candidate cells in order to better translate cell therapy to the bedside. This review will provide a translationally relevant overview of the biology of candidate stem/progenitor cells for therapeutic angiogenesis.

Association of electrostimulation with cell transplantation in ischemic heart disease

BACKGROUND

Until now, cell therapy has constituted a passive therapeutic approach; the only effects seem to be related to the reduction of the myocardial fibrosis and the limitation of the adverse ventricular remodeling. Cardiac resynchronization therapy is indicated in patients with heart failure to correct conduction disorders associated with chronic systolic and diastolic dysfunction. The association of electrostimulation with cellular cardiomyoplasty could be a way to transform passive cell therapy into "dynamic cellular support." Electrostimulation of ventricles following skeletal myoblast implantation should induce the contraction of the transplanted cells and a higher expression of slow myosin, which is better adapted for chronic ventricular assistance. The purpose of this study is to evaluate myogenic cell transplantation in an ischemic heart model associated with cardiac resynchronization therapy.

METHODS

Twenty two sheep were included. All animals underwent myocardial infarction by ligation of 2 coronary artery branches (distal left anterior descending artery and D2). After 4 weeks, autologous cultured myoblasts were injected in the infarcted areas with or without pacemaker implantation. Atrial synchronized biventricular pacing was performed using epicardial electrodes. Echocardiography was performed at 4 weeks (baseline) and 12 weeks after infarction.

RESULTS

Echocardiography showed a significant improvement in ejection fraction and limitation of left ventricular dilatation in cell therapy with cardiac resynchronization therapy as compared with the other groups. Viable cells were identified in the infarcted areas. Differentiation of myoblasts into myotubes and enhanced expression of slow myosin heavy chain was observed in the electrostimulated group. Transplantation of cells with cardiac resynchronization therapy caused an increase in diastolic wall thickening in the infarcted zone relative to cells-only group and cardiac resynchronization therapy-only group.

CONCLUSIONS

Biventricular pacing seems to induce synchronous contraction of transplanted myoblasts and the host myocardium, thus improving ventricular function. Electrostimulation was related with enhanced expression of slow myosin and the organization of myoblasts in myotubes, which are better adapted at performing cardiac work. Patients with heart failure presenting myocardial infarct scars and indication for cardiac resynchronization therapy might benefit from simultaneous cardiac pacing and cell therapy.

An acellular matrix-bound ligand enhances the mobilization, recruitment and therapeutic effects of circulating progenitor cells in a hindlimb ischemia model

Circulating progenitor cells home to and engraft to sites of ischemia, mediated in part by the adhesion molecule L-selectin; however, accumulation in tissues such as the heart is low. In this study, an acellular collagen-based matrix containing sialyl Lewis(X) (sLe(X)), which binds L-selectin, was developed in order to enhance the endogenous progenitor cell therapeutic response. Its effect on progenitor cells and angiogenesis were assessed in vitro and using a hindlimb ischemia model with rats. In culture, the sLe(X)-collagen matrix recruited more CD133(+)CD34(+)L-selectin(+) cells than collagen-only matrix, with adhesion mediated by L-selectin binding. Increased angiogenic/chemotactic cytokine production and improved resistance to apoptosis appeared in cells cultured on sLe(X)-collagen matrix. In vivo, mobilization of endogenous circulating progenitor cells was increased, and greater recruitment of these and systemically injected human peripheral blood CXCR4(+)L-selectin(+) cells to sLe(X)-collagen treated limbs was observed compared to collagen-only. This condition was associated with differences in angiogenic/chemotactic cytokine levels, with greater arteriole density and increased perfusion in sLe(X)-collagen treated hindlimbs. With these factors taken together, we demonstrated that an acellular matrix-bound ligand approach can enhance the mobilization, recruitment, and therapeutic effects of endogenous and/or transplanted progenitor cells, possibly through paracrine and antiapoptotic mechanisms, and could be used to improve cell-based regenerative therapies.

Expression of cardiac function genes in adult stem cells is increased by treatment with nitric oxide agents

Mesenchymal stem cells (MSCs) have received special attention for cardiomyoplasty because several studies have shown that they differentiate into cardiomyocytes both in vitro and in vivo. Nitric oxide (NO) is a free radical signaling molecule that regulates several differentiation processes including cardiomyogenesis. Here, we report an investigation of the effects of two NO agents (SNAP and DEA/NO), able to activate both cGMP-dependent and -independent pathways, on the cardiomyogenic potential of bone marrow-derived mesenchymal stem cells (BM-MSCs) and adipose tissue-derived stem cells (ADSCs). The cells were isolated, cultured and treated with NO agents. Cardiac- and muscle-specific gene expression was analyzed by indirect immunofluorescence, flow cytometry, RT-PCR and real-time PCR. We found that untreated (control) ADSCs and BM-MSCs expressed some muscle markers and NO-derived intermediates induce an increased expression of some cardiac function genes in BM-MSCs and ADSCs. Moreover, NO agents considerably increased the pro-angiogenic potential mostly of BM-MSCs as determined by VEGF mRNA levels.

Improving cell engraftment with tissue engineering

Cardiac cell therapy has not yet resulted in long-term clinical benefits or major recovery of myocardial function in humans. To date, most of the cardiac effects of cell-based therapy are believed to be mediated by a local angiogenic response rather than by the formation of neosyncytial contractile units such as had initially been hoped for. Therefore, repopulation of the ischemic or infarcted heart with progenitor cells that have vasculogenic potential may be an important mechanism to improve contractile function, both in the presence of viable and nonviable myocardium. This constitutes a focus within scientific reach; however, the low engraftment and viability of progenitor cells after transplantation necessitate the exploration of novel delivery techniques. Because biomaterials have the capacity to improve cell retention, survival, and differentiation, tissue engineering is now being explored as an approach to support cell-based therapies and enhance their efficacy. In this article, we address current progress made in tissue engineering to support cell therapy for the heart, and summarize our work in the development of biomaterials toward improving cell delivery and vascularization of ischemic tissue.

Combined transplantation of endothelial progenitor cells and mesenchymal stem cells into a rat model of isoproterenol-induced myocardial injury

BACKGROUND

Endothelial progenitor cells (EPCs) and mesenchymal stem cells (MSCs) have different biological properties, but their potential for synergy in the treatment of injured myocardium has not been studied extensively.

AIM

To determine if outcome could be improved by simultaneously transplanting MSCs and EPCs into a rat model of isoproterenol (ISO)-induced injured myocardium.

METHODS

Four weeks after ISO injection, 50 rats were separated randomly into five groups (n=10 per group) and allocated to receive a saline injection (control group), 200 microL medium alone, 200 microL medium plus 2x10(6) EPCs, 200 microL medium plus 2x10(6) MSCs, or 200 microL medium plus a combination of 1x10(6) EPCs and 1x10(6) MSCs. Echocardiography and invasive catheterization were performed to evaluate dynamic changes in cardiac performance, 12 weeks after treatment administration.

RESULTS

Transplanted cells were detected in myocardial tissue by fluorescence in situ hybridization, indicating either differentiation or integration into cardiac tissue cells. The group of rats that received both EPCs and MSCs had an increased level of angiogenic growth factors expression, less collagen deposition, fewer apoptotic cells and an improved regional myocardial blood flow compared with the other groups; these effects resulted in greater enhancement of cardiac function in that group.

CONCLUSION

Transplantation of EPCs combined with MSCs may represent a novel and efficient therapeutic strategy for enhancing regional myocardial blood flow and improving cardiac function in injured myocardium.