Locally overexpressing hepatocyte growth factor prevents post-ischemic heart failure by inhibition of apoptosis via calcineurin-mediated pathway and angiogenesis

Effect of Expansion Media on Functional Characteristics of Bone Marrow-Derived Mesenchymal Stromal Cells

The therapeutic efficacy of mesenchymal stromal cells (MSCs) has been shown to rely on their immunomodulatory and regenerative properties. In order to obtain sufficient numbers of cells for clinical applications, MSCs have to be expanded ex vivo. Expansion media with xenogeneic-free (XF) growth-promoting supplements like human platelet lysate (PL) or serum- and xenogeneic-free (SF/XF) formulations have been established as safe and efficient, and both groups provide different beneficial qualities. In this study, MSCs were expanded in XF or SF/XF media as well as in mixtures thereof. MSCs cultured in these media were analyzed for phenotypic and functional properties. MSC expansion was optimal with SF/XF conditions when PL was present. Metabolic patterns, consumption of growth factors, and secretome of MSCs differed depending on the type and concentration of supplement. The lactate per glucose yield increased along with a higher proportion of PL. Many factors in the supernatant of cultured MSCs showed distinct patterns depending on the supplement (e.g., FGF-2, TGFβ, and insulin only in PL-expanded MSC, and leptin, sCD40L PDGF-AA only in SF/XF-expanded MSC). This also resulted in changes in cell characteristics like migratory potential. These findings support current approaches where growth media may be utilized for priming MSCs for specific therapeutic applications.

Recent advances in pre-conditioned mesenchymal stem/stromal cell (MSCs) therapy in organ failure; a comprehensive review of preclinical studies

Mesenchymal stem/stromal cells (MSCs)-based therapy brings the reassuring capability to regenerative medicine through their self-renewal and multilineage potency. Also, they secret a diversity of mediators, which are complicated in moderation of deregulated immune responses, and yielding angiogenesis in vivo. Nonetheless, MSCs may lose biological performance after procurement and prolonged expansion in vitro. Also, following transplantation and migration to target tissue, they encounter a harsh milieu accompanied by death signals because of the lack of proper tensegrity structure between the cells and matrix. Accordingly, pre-conditioning of MSCs is strongly suggested to upgrade their performances in vivo, leading to more favored transplantation efficacy in regenerative medicine. Indeed, MSCs ex vivo pre-conditioning by hypoxia, inflammatory stimulus, or other factors/conditions may stimulate their survival, proliferation, migration, exosome secretion, and pro-angiogenic and anti-inflammatory characteristics in vivo. In this review, we deliver an overview of the pre-conditioning methods that are considered a strategy for improving the therapeutic efficacy of MSCs in organ failures, in particular, renal, heart, lung, and liver.

Are There Hopeful Therapeutic Strategies to Regenerate the Infarcted Hearts?

Ischemic heart disease remains the primary cause of morbidity and mortality worldwide. Despite significant advancements in pharmacological and revascularization techniques in the late 20th century, heart failure prevalence after myocardial infarction has gradually increased over the last 2 decades. After ischemic injury, pathological remodeling results in cardiomyocytes (CMs) loss and fibrosis, which leads to impaired heart function. Unfortunately, there are no clinical therapies to regenerate CMs to date, and the adult heart's limited turnover rate of CMs hinders its ability to self-regenerate. In this review, we present novel therapeutic strategies to regenerate injured myocardium, including (1) reconstruction of cardiac niche microenvironment, (2) recruitment of functional CMs by promoting their proliferation or differentiation, and (3) organizing 3-dimensional tissue construct beyond the CMs. Additionally, we highlight recent mechanistic insights that govern these strategies and identify current challenges in translating these approaches to human patients.

Recent advances in the therapeutic efficacy of hepatocyte growth factor gene-modified mesenchymal stem cells in multiple disease settings

Mesenchymal stem cell (MSC) therapy is considered a new treatment for a wide range of diseases and injuries, but challenges remain, such as poor survival, homing and engraftment rates, thus limiting the therapeutic efficacy of the transplanted MSCs. Many strategies have been developed to enhance the therapeutic efficacy of MSCs, such as preconditioning, co-transplantation with graft materials and gene modification. Hepatocyte growth factor (HGF) is secreted by MSCs, which plays an important role in MSC therapy. It has been reported that the modification of the HGF gene is beneficial to the therapeutic efficacy of MSCs, including diseases of the heart, lung, liver, urinary system, bone and skin, lower limb ischaemia and immune-related diseases. This review focused on studies involving HGF/MSCs both in vitro and in vivo. The characteristics of HGF/MSCs were summarized, and the mechanisms of their improved therapeutic efficacy were analysed. Furthermore, some insights are provided for HGF/MSCs' clinical application based on our understanding of the HGF gene and MSC therapy.

Catecholamine-induced cardiotoxicity: A critical element in the pathophysiology of stroke-induced heart injury

Cerebrovascular diseases such as ischemic stroke, brain hemorrhage, and subarachnoid hemorrhage provoke cardiac complications such as heart failure, neurogenic stress-related cardiomyopathy and Takotsubo cardiomyopathy. With regards to the pathophysiology of stroke-induced heart injury, several mechanisms have been postulated to contribute to this complex interaction between brain and heart, including damage from gut dysbiosis, immune and systematic inflammatory responses, microvesicle- and microRNA-mediated vascular injury and damage from a surge of catecholamines. All these cerebrovascular diseases may trigger pronounced catecholamine surges through diverse ways, including stimulation of hypothalamic-pituitary adrenal axis, dysregulation of autonomic system, and secretion of adrenocorticotropic hormone. Primary catecholamines involved in this pathophysiological response include norepinephrine (NE) and epinephrine. Both are important neurotransmitters that connect the nervous system with the heart, leading to cardiac damage via myocardial ischemia, calcium (Ca²⁺) overload, oxidative stress, and mitochondrial dysfunction. In this review, we will aim to summarize the molecular mechanisms behind catecholamine-induced cardiotoxicity including Ca²⁺ overload, oxidative stress, apoptosis, cardiac hypertrophy, interstitial fibrosis, and inflammation. In addition, we will focus on how synchronization among these pathways evokes cardiotoxicity.

Genetic Engineering as a Strategy to Improve the Therapeutic Efficacy of Mesenchymal Stem/Stromal Cells in Regenerative Medicine

Mesenchymal stem/stromal cells (MSCs) have been widely studied in the field of regenerative medicine for applications in the treatment of several disease settings. The therapeutic potential of MSCs has been evaluated in studies in vitro and in vivo, especially based on their anti-inflammatory and pro-regenerative action, through the secretion of soluble mediators. In many cases, however, insufficient engraftment and limited beneficial effects of MSCs indicate the need of approaches to enhance their survival, migration and therapeutic potential. Genetic engineering emerges as a means to induce the expression of different proteins and soluble factors with a wide range of applications, such as growth factors, cytokines, chemokines, transcription factors, enzymes and microRNAs. Distinct strategies have been applied to induce genetic modifications with the goal to enhance the potential of MCSs. This review aims to contribute to the update of the different genetically engineered tools employed for MSCs modification, as well as the factors investigated in different fields in which genetically engineered MSCs have been tested.

Renal subcapsular transplantation of hepatocyte growth factor-producing mesothelial cell sheets improves ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) is a clinically important cause of acute kidney injury leading to chronic kidney disease. Furthermore, IRI in renal transplantation still remains a risk factor for delayed graft function. Previous studies on IRI have had some limitations, and few of the studied therapies have been clinically applicable. Therefore, a new method for treating renal IRI is needed. We examined the effects of human mesothelial cell (MC) sheets and hepatocyte growth factor (HGF)-transgenic MC (tg MC) sheets transplanted under the renal capsule in an IRI rat model and compared these two treatments with the intravenous administration of HGF protein and no treatment through serum, histological, and mRNA analyses over 28 days. MC sheets and HGF-tg MC sheets produced HGF protein and significantly improved acute renal dysfunction, acute tubular necrosis, and survival rate. The improvement in necrosis was likely due to the cell sheets promoting the migration and proliferation of renal tubular cells, as observed in vitro. Expression of α-smooth muscle actin at day 14 and renal fibrosis at day 28 after IRI were significantly suppressed in MC sheet and HGF-tg MC sheet treatment groups compared with the other groups, and these effects tended to be reinforced by the HGF-tg MC sheets. These results suggest that the cell sheets locally and continuously affect renal paracrine factors, such as HGF, and support recovery from acute tubular necrosis and improvement of renal fibrosis in chronic disease.

The membrane mesenchymal stem cell derived conditioned medium exerts neuroprotection against focal cerebral ischemia by targeting apoptosis

OBJECTIVE

The mesenchymal stem cells derived from human amniotic membrane have the ability to secrete and release some factors that can promote the repair of damaged tissues. This secretome contains proteins and factors that reduce apoptosis and increase angiogenesis in the ischemia/reperfusion models. The present study was conducted to determine whether this secretome provides protection against transient focal cerebral ischemia.

MATERIALS AND METHODS

A rat model of focal cerebral ischemia was established through middle cerebral artery occlusion (MCAO) for 60 min and 24 h reperfusion. The amniotic mesenchymal stem cells-conditioned medium (AMSC-CM) at the dose of 0.5 μl was injected intracerebroventriculary (ICV) 30 min after reperfusion. Infarct volume, brain edema, neurobehavioral functions, and blood brain barrier (BBB) integrity were assessed 24 h after reperfusion. Neuronal loss and expression of caspase-3, Bax and Bcl-2 in motor cortex were evaluated by nissl staining and immunohistochemistry assay respectively.

RESULTS

ICV administration of AMSC-CM markedly reduced infarct volume, brain edema and the evans blue penetration rate compared with MCAO group (P < 0.05). Additionally, post-treatment with AMSC-CM significantly reduced neuronal loss, neurological motor disorders and expression of caspase-3, Bax and Bcl-2 in motor cortex compared with MCAO group (P < 0.05).

CONCLUSION

The results of this study indicate that treatment with AMSC-CM improves the pathological effects in the acute phase of cerebral ischemia. These findings establish a substantial foundation for stroke therapy and future research.

The Multiplicity of Infection-Dependent Effects of Recombinant Adenovirus Carrying HGF Gene on the Proliferation and Osteogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells

Absence of effective therapeutic methods for avascular necrosis of femoral head (ANFH) is still perplexing the world’s medical community. Bone marrow mesenchymal stem cells (BMSCs) adoptive cell therapy combined with core decompression is a promising modality, which is highly dependent on the cellular activities of BMSCs. Hepatocyte growth factor (HGF) is a survival factor for BMSCs, yet the underlying mechanism is not fully elucidated. In this study, the effects of multiplicity of infections (MOIs) of recombinant adenovirus carrying HGF gene (rAd-HGF) on human BMSC proliferation and osteogenic differentiation were systemically examined. Infection of rAd-HGF produced secretory HGF and promoted hBMSC proliferation in a MOI-dependent manner, while the osteogenesis was also strengthened as indicated by enhanced calcium nodule formation with the strongest effects achieved at MOI = 250. Blocking the activities of c-MET or its downstream signaling pathways, WNT, ERK1/2, and PI3K/AKT led to differential consequents. Specifically, blockage of the WNT pathway significantly promoted osteogenic differentiation, which also showed additive effects when combined application with rAd-HGF. Our data demonstrated the pro-osteogenic effects of optimized MOIs of rAd-HGF, while inhibition of WNT pathway or activation of PI3K/AKT pathway may act as candidate adjuvant modalities for promoting osteogenic differentiation in rAd-HGF-modified hBMSC treatment on ANFH.

Hepatocyte growth factor: Molecular biomarker and player in cardioprotection and cardiovascular regeneration

The liver possesses impressive regenerative capacities. Grafts of embryonic liver explants and liver explant-conditioned media have been shown to enhance the mitotic activity of hepatocytes. Hepatocyte growth factor (HGF), also named scatter factor (SF), has been identified as a primary candidate in promoting and regulating liver regeneration. Although initially thought to be a liver-specific mitogen, HGF was later reported to have mitogenic, motogenic, morphogenic, and anti-apoptotic activities in various cell types. By promoting angiogenesis and inhibiting apoptosis, endogenous HGF may play an important role in cardioprotection as well as in the regeneration of endothelial cells and cardiomyocytes after myocardial infarction. Since serum concentration of HGF increases in the early phase of myocardial infarction and in heart failure, HGF may also play a key role as a prognostic and diagnostic biomarker of cardiovascular disease. Here we discuss the role of HGF as a biomarker and mediator in cardioprotection and cardiovascular regeneration.

Role of miR-128 in hypertension-induced myocardial injury

The present study aimed to investigate the role and mechanism of micro RNA (miR)-128 in hypertension-induced myocardial injury. The peripheral blood of patients with hypertension was collected and the expression of miR-128 was detected using fluorescence reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Primary myocardial cells isolated from rat in vitro were cultured under conditions of hypoxia and glucose deprivation, and miR-128 expression was measured by RT-qPCR. The expression of c-Met protein was measured using western blot analysis and the apoptosis of transfected cells was measured by flow cytometry in rat myocardial cells following transfection with miR-128 mimics or c-Met siRNA. A luciferase assay was applied to assess the binding of miR-128 to c-Met mRNA. miR-128 expression was significantly higher in hypertension patients compared with controls (P<0.05). miR-128 expression was higher in patients with stage III/IV hypertension compared with patients with stage II hypertension. Similarly, miR-128 expression in primary cardiomyocytes cultured under deprivation of oxygen and glucose increased with the culture time and reached a peak at 12 h. c-Met expression decreased significantly (P<0.05) and the ratio of apoptotic cells increased significantly (P<0.05), following transfection of miR-128 mimics. The number of apoptotic cells also increased when c-Met expression was knocked down by siRNA. The dual luciferase assay indicated that fluorescence intensity decreased significantly in miR-128 mimics and wild type c-Met group (P<0.05), indicating that miR-128 can directly target c-Met. Therefore, the results of the current study suggest that miR-128 may promote myocardial cell injury by regulating c-Met expression.

Extracellular matrix protein laminin enhances mesenchymal stem cell (MSC) paracrine function through αvβ3/CD61 integrin to reduce cardiomyocyte apoptosis

Myocardial ischaemia (MI) results in extensive cardiomyocyte death and reactive oxygen species (ROS)-induced damage in an organ with little or no regenerative capacity. Although the use of adult bone marrow mesenchymal stem cells (BMMSCs) has been proposed as a treatment option, the high cell numbers required for clinical use are difficult to achieve with this source of MSCs, and animal studies have produced inconsistent data. We recently demonstrated in small and large animal models of acute MI that the application of human term placenta-derived multipotent cells (PDMCs), a foetal-stage MSC, resulted in reversal of cardiac injury with therapeutic efficacy. However, the mechanisms involved are unclear, making it difficult to strategize for therapeutic improvements. We found that PDMCs significantly reduced cardiomyocyte apoptosis and ROS production through the paracrine factors GRO-α, HGF and IL-8. Moreover, culturing PDMCs on plates coated with laminin, an extracellular matrix (ECM) protein, resulted in significantly enhanced secretion of all three paracrine factors, which further reduced cardiomyocyte apoptosis. The enhancement of PDMC paracrine function by laminin was mediated through αvβ3 integrin, with involvement of the signalling pathways of JNK, for GRO-α and IL-8 secretion, and PI3K/AKT, for HGF secretion. Our results demonstrated the utility of PDMC therapy to reduce cardiomyocyte apoptosis through modulation of ECM proteins in in vitro culture systems as a strategy to enhance the therapeutic functions of stem cells.

Can the outcomes of mesenchymal stem cell-based therapy for myocardial infarction be improved? Providing weapons and armour to cells

Use of mesenchymal stem cell (MSC) transplantation after myocardial infarction (MI) has been found to have infarct-limiting effects in numerous experimental and clinical studies. However, recent meta-analyses of randomized clinical trials on MSC-based MI therapy have highlighted the need for improving its efficacy. There are two principal approaches for increasing therapeutic effect of MSCs: (i) preventing massive MSC death in ischaemic tissue and (ii) increasing production of cardioreparative growth factors and cytokines with transplanted MSCs. In this review, we aim to integrate our current understanding of genetic approaches that are used for modification of MSCs to enable their improved survival, engraftment, integration, proliferation and differentiation in the ischaemic heart. Genetic modification of MSCs resulting in increased secretion of paracrine factors has also been discussed. In addition, data on MSC preconditioning with physical, chemical and pharmacological factors prior to transplantation are summarized. MSC seeding on three-dimensional polymeric scaffolds facilitates formation of both intercellular connections and contacts between cells and the extracellular matrix, thereby enhancing cell viability and function. Use of genetic and non-genetic approaches to modify MSC function holds great promise for regenerative therapy of myocardial ischaemic injury.

Empowering Adult Stem Cells for Myocardial Regeneration V2.0: Success in Small Steps

Much has changed since our survey of the landscape for myocardial regeneration powered by adult stem cells 4 years ago.(1) The intervening years since that first review has witnessed an explosive expansion of studies that advance both understanding and implementation of adult stem cells in promoting myocardial repair. Painstaking research from innumerable laboratories throughout the world is prying open doors that may lead to restoration of myocardial structure and function in the wake of pathological injury. This global effort has produced deeper mechanistic comprehension coupled with an evolving appreciation for the complexity of myocardial regeneration in the adult context. Undaunted by both known and (as yet) unknown challenges, pursuit of myocardial regenerative medicine mediated by adult stem cell therapy has gathered momentum fueled by tantalizing clues and visionary goals. This concise review takes a somewhat different perspective than our initial treatise, taking stock of the business sector that has become an integral part of the field while concurrently updating state of affairs in cutting edge research. Looking retrospectively at advancement over the years as all reviews eventually must, the fundamental lesson to be learned is best explained by Jonatan Mårtensson: "Success will never be a big step in the future. Success is a small step taken just now."

Mesenchymal stromal cells overexpressing vascular endothelial growth factor in ovine myocardial infarction

Mesenchymal stromal cells (MSCs) are cardioprotective in acute myocardial infarction (AMI). Besides, we have shown that intramyocardial injection of plasmid-VEGF(165) (pVEGF) in ovine AMI reduces infarct size and improves left ventricular (LV) function. We thus hypothesized that MSCs overexpressing VEGF(165) (MSCs-pVEGF) would afford greater cardioprotection than non-modified MSCs or pVEGF alone. Sheep underwent an anteroapical AMI and, 1 week later, received intramyocardial MSCs-pVEGF in the infarct border. One month post treatment, infarct size (magnetic resonance) decreased by 31% vs pre-treatment. Of note, myocardial salvage occurred predominantly at the subendocardium, the myocardial region displaying the largest contribution to systolic performance. Consistently, LV ejection fraction recovered to almost its baseline value because of marked decrease in end-systolic volume. None of these effects were observed in sheep receiving non-transfected MSCs or pVEGF. Although myocardial retention of MSCs decreased steeply over time, the treatment induced significant capillary and arteriolar proliferation, which reduced subendocardial fibrosis. We conclude that in ovine AMI, allogeneic VEGF-overexpressing MSCs induce subendocardial myocardium salvage through microvascular proliferation, reducing infarct size and improving LV function more than non-transfected MSCs or the naked plasmid. Importantly, the use of a plasmid rather than a virus allows for repeated treatments, likely needed in ischemic heart disease.

Hepatocyte growth factor gene-modified bone marrow-derived mesenchymal stem cells transplantation promotes angiogenesis in a rat model of hindlimb ischemia

Angiogenic gene therapy and cell-based therapy for peripheral arterial disease(PAD) have been studied intensively currently. This study aimed to investigate whether combining mesenchymal stem cells(MSCs) transplantation with ex vivo human hepatocyte growth factor(HGF) gene transfer was more therapeutically efficient than the MSCs therapy alone in a rat model of hindlimb ischemia. One week after establishing hindlimb ischemia models, Sprague-Dawley(SD) rats were randomized to receive HGF gene-modified MSCs transplantation(HGF-MSC group), untreated MSCs transplantation (MSC group), or PBS injection(PBS group), respectively. Three weeks after injection, angiogenesis was significantly induced by both MSCs and HGF-MSCs transplantation, and capillary density was the highest in the HGF-MSC group. The number of transplanted cell-derived endothelial cells was greater in HGF-MSC group than in MSC group after one week treatment. The expression of angiogenic cytokines such as HGF and VEGF in local ischemic muscles was more abundant in HGF-MSC group than in the other two groups. In vitro, the conditioned media obtained from HGF-MSCs cultures exerted proproliferative and promigratory effects on endothelial cells. It is concluded that HGF gene-modified MSCs transplantation therapy may induce more potent angiogenesis than the MSCs therapy alone. Engraftment of MSCs combined with angiogenic gene delivery may be a promising therapeutic strategy for the treatment of severe PAD.

Effects of recombinant adenovirus hepatocyte growth factor gene on myocardial remodeling in spontaneously hypertensive rats

BACKGROUND AND OBJECTIVES

Myocardial hypertrophy and fibrosis are important determinants of congestive heart failure. Previous work has shown that hepatocyte growth factor (HGF) can reduce acute myocardial injury and tissue fibrosis. This study was designed to examine the effects of HGF on myocardial remodeling following sustained hypertension.

METHODS AND RESULTS

There were 4 experimental groups (n = 6) that included spontaneously hypertensive rats (SHRs) injected with 0.1 mL of adenovirus (Ad)-null into the left ventricular (LV) free wall, SHR injected with 0.1 mL of Ad-HGF gene (5 × 10(9) pfu/mL), and SHR injected with 0.1 mL of normal saline, and Wistar Kyoto rats injected with 0.1 mL of Ad-null served as control. At 4 weeks after injection, rats were sacrificed, and HGF expression, myocardial fibrosis, and LV function were determined. We observed that HGF protein expression was reduced in the hearts of SHR (P < .05 vs normal control) and it was markedly increased in SHR injected with Ad-HGF (P < .01 vs SHR injected with Ad-null). Myocardial fibrosis, collagen I, LV mass index (LVMI), and LV end-diastolic pressure (LVEDP) were increased and -dP/dtmax was decreased in SHR injected with Ad-null or normal saline (P < .01 vs normal control). Upregulation of myocardial HGF expression in SHR significantly suppressed myocardial fibrosis, collagen I content, LVMI, LVEDP, and increased -dP/dtmax (all P < .05 vs SHR-Ad-null, n = 6).

CONCLUSIONS

These findings indicate that HGF expression is attenuated in hypertrophic and fibrotic myocardium of SHR. The forced increase in HGF exerts a salutary effect on myocardial fibrosis, collagen I expression, and hemodynamic parameters.

MSCs transfected with hepatocyte growth factor or vascular endothelial growth factor improve cardiac function in the infarcted porcine heart by increasing angiogenesis and reducing fibrosis

BACKGROUND

Cell transplantation and gene therapy have been demonstrated to have beneficial effects after a myocardial infarction (MI). Here, we used a large animal model of MI to investigate the beneficial effects of mesenchymal stem cells (MSCs) transfected with hepatocyte growth factor (HGF) or vascular endothelial growth factor (VEGF) genes.

METHODS

A porcine MI model was created by balloon occlusion of the distal left anterior descending artery for 90 min followed by reperfusion. At 1 week after MI, the pigs were infused via the coronary vein with saline (n=8), MSCs + AdNull(n=8), MSC+VEGF(n=10), or MSC+HGF(n=10). Cardiac function and myocardial perfusion were evaluated by using echocardiography and gated cardiac perfusion imaging before and 4 weeks after transplantation. Morphometric and histological analyses were performed.

RESULTS

All cell-implanted groups had better cardiac function than the saline control group. There were further functional improvements in the MSC+HGF group, accompanied by smaller infarct sizes, increased cell survival, and less collagen deposition. Blood vessel densities in the damaged area and cardiac perfusion were significantly greater in the MSC+AdNull group than in the saline control group, and further increased in the MSC+VEGF/HGF groups. Tissue fibrosis was significantly less extensive in the MSC and MSC+VEGF groups than in the saline control group and was most reduced in the MSC+HGF group.

CONCLUSION

MSCs (alone or transfected with VEGF/HGF) delivered into the infarcted porcine heart via the coronary vein improved cardiac function and perfusion, probably by increasing angiogenesis and reducing fibrosis. MSC+HGF was superior to MSC+VEGF, possibly owing to its enhanced antifibrotic effect.

Effect of bone marrow mesenchymal stem cells on experimental pulmonary arterial hypertension

The aim of the present study was to investigate the effect of bone marrow mesenchymal stem cell (BMSC) transp1antation on lung and heart damage in a rat model of monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH). The animals were randomly divided into 3 groups: control, PAH and BMSC implantation groups. Structural changes in the pulmonary vascular wall, such as the pulmonary artery lumen area (VA) and vascular area (TAA) were measured by hematoxylin and eosin (H&E) staining, and the hemodynamics were detected by echocardiography. Two weeks post-operation, our results demonstrated that sublingual vein injection of BMSCs significantly attenuated the pulmonary vascular structural and hemodynamic changes caused by pulmonary arterial hypertension. The mechanism may be executed via paracrine effects.

Mesenchymal stem cell prevention of vascular remodeling in high flow-induced pulmonary hypertension through a paracrine mechanism

Pulmonary arterial hypertension (PAH) is characterized by functional and structural changes in the pulmonary vasculature, and despite the drug treatment that made significant progress, the prognosis of patients with advanced PH remains extremely poor. In the present study, we investigated the early effect of bone marrow mesenchymal stem cells (BMSCs) on experimental high blood flow-induced PAH model rats and discussed the mechanism. BMSCs were isolated, cultured from bone marrow of Sprague-Dawley (SD) rat. The animal model of PAH was created by surgical methods to produce a left-to-right shunt. Following the successful establishment of the PAH model, rats were randomly assigned to three groups (n=20 in each group): sham group (control), PAH group, and BMSC group (received a sublingual vein injection of 1-5 × 10(6) BMSCs). Two weeks after the administration, BMSCs significantly reduced the vascular remodeling, improved the hemodynamic data, and deceased the right ventricle weight ratio to left ventricular plus septal weight (RV/LV+S) (P<0.05). Real-time reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry analysis results indicated that the inflammation factors such as interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α) were reduced (P<0.05); the expression of matrix metallo proteinase-9 (MMP-9) was lower (P<0.05); vascular endothelial growth factor (VEGF) was higher in BMSC group than those in PAH group (P<0.05).

CONCLUSION

Sublingual vein injection of BMSCs for 2 weeks, significantly improved the lung and heart injury caused by left-to-right shunt-induced PAH; decreased pulmonary vascular remodeling and inflammation; and enhanced angiogenesis.

Implantation of mesenchymal stem cells improves right ventricular impairments caused by experimental pulmonary hypertension

INTRODUCTION

Pulmonary hypertension (PH) is a rapidly progressive and fatal disease. In recent years, despite drug treatment made significant progress, the prognosis of patients with advanced PH remains extremely poor. The authors implanted bone marrow-derived mesenchymal stem cells (BMSCs) intravenously into the PH model rats and observed the effect of MSCs on right ventricular (RV) impairments.

METHODS

BMSCs were isolated, cultured from bone marrow of rats and stained with the cross-linkable membrane dye in vitro. One week after, a PH model was induced by subcutaneous injection of monocrotaline, the animals were randomly divided into 4 groups (n = 20 in each group): I, control; II, MSCs implantation; III, PH and IV, PH + MSCs implantation. Two weeks after MSCs implantation, the authors observed the MSC survival and transformation by immunofluorescence microscopy. On the other hand, RV hypertrophy and the elevation of systolic pressure were detected by echocardiography.

RESULT

Three weeks after monocrotaline injection, RV systolic pressure, mean right ventricular pressure and mean pulmonary arterial pressure were significantly elevated in group III than in group I and II (P < 0.05) but significantly lower in group IV than in group III (P < 0.05). These results showed that implantation of MSCs could improve RV impairments caused by experimental PH. Histochemical results confirmed that transplanted MSCs were still alive after 2 weeks and part of the cells could differentiate into pulmonary vascular endothelial cells.

CONCLUSION

Intravenous implantation of MSCs could significantly reduce or even reverse the progression of MCT-induced PH, improve cardiac function and hemodynamics.

Mesenchymal stem cells for cardiac regeneration: translation to bedside reality

Cardiovascular disease (CVD) is the leading cause of death worldwide. According to the World Health Organization (WHO), an estimate of 17.3 million people died from CVDs in 2008 and by 2030, the number of deaths is estimated to reach almost 23.6 million. Despite the development of a variety of treatment options, heart failure management has failed to inhibit myocardial scar formation and replace the lost cardiomyocyte mass with new functional contractile cells. This shortage is complicated by the limited ability of the heart for self-regeneration. Accordingly, novel management approaches have been introduced into the field of cardiovascular research, leading to the evolution of gene- and cell-based therapies. Stem cell-based therapy (aka, cardiomyoplasty) is a rapidly growing alternative for regenerating the damaged myocardium and attenuating ischemic heart disease. However, the optimal cell type to achieve this goal has not been established yet, even after a decade of cardiovascular stem cell research. Mesenchymal stem cells (MSCs) in particular have been extensively investigated as a potential therapeutic approach for cardiac regeneration, due to their distinctive characteristics. In this paper, we focus on the therapeutic applications of MSCs and their transition from the experimental benchside to the clinical bedside.

Aging might increase myocardial ischemia / reperfusion-induced apoptosis in humans and rats

Previous studies indicated aging results in the significant cardiac function decreasing and myocardial apoptosis increasing in normal humans or rats. Additionally, animal experiments demonstrated aging increased myocardial ischemia / reperfusion (MI/R)-induced apoptosis. However, whether more myocardial apoptosis happen in the old acute myocardial infarction (AMI) patients is unclear. Reperfusion injury-induced apoptosis is an important cause of heart failure. This study determined the effect of aging upon myocardial apoptosis and cardiac function in patients suffering AMI. All enrolled AMI patients received percutaneous coronary intervention therapy. Volunteers and AMI patients were assigned to four groups: adult (age <65, n = 24) volunteers, elderly (age ≥65, n = 21) volunteers, adult (age <65, n = 29) AMI patients, and elderly (age ≥65, n = 36) AMI patients. Blood samples were obtained from all study participants. Plasma apoptotic markers (soluble form of Fas, tumor necrosis factor alpha, and interleukin 6) levels were determined. Cardiac function was evaluated with echocardiogram and Killip class. Due to lack of a direct apoptotic assay method in live human subjects, an additional animal experiment was performed. Both young (2 months) and old (24 months) rats were subjected to 30-min myocardial ischemia and 3 (for TUNEL/caspase activity apoptotic assay) or 24-h (for cardiac function determination) reperfusion. Compared to adult patients, the elderly patients manifested decreased cardiac function and increased plasma apoptotic marker levels significantly. The animal experiment results (cardiac function and plasma apoptotic markers assays) were consistent with the human result data. Animal TUNEL staining and caspase activity measurement revealed a higher myocardial apoptotic ratio in the older rat group. Aging exacerbated MI/R injury in humans and rats. Differential myocardial apoptosis may play a vital role in mediating the observed effects.

Empowering adult stem cells for myocardial regeneration

Treatment strategies for heart failure remain a high priority for ongoing research due to the profound unmet need in clinical disease coupled with lack of significant translational progress. The underlying issue is the same whether the cause is acute damage, chronic stress from disease, or aging: progressive loss of functional cardiomyocytes and diminished hemodynamic output. To stave off cardiomyocyte losses, a number of strategic approaches have been embraced in recent years involving both molecular and cellular approaches to augment myocardial structure and performance. Resultant excitement surrounding regenerative medicine in the heart has been tempered by realizations that reparative processes in the heart are insufficient to restore damaged myocardium to normal functional capacity and that cellular cardiomyoplasty is hampered by poor survival, proliferation, engraftment, and differentiation of the donated population. To overcome these limitations, a combination of molecular and cellular approaches must be adopted involving use of genetic engineering to enhance resistance to cell death and increase regenerative capacity. This review highlights biological properties of approached to potentiate stem cell-mediated regeneration to promote enhanced myocardial regeneration, persistence of donated cells, and long-lasting tissue repair. Optimizing cell delivery and harnessing the power of survival signaling cascades for ex vivo genetic modification of stem cells before reintroduction into the patient will be critical to enhance the efficacy of cellular cardiomyoplasty. Once this goal is achieved, then cell-based therapy has great promise for treatment of heart failure to combat the loss of cardiac structure and function associated with acute damage, chronic disease, or aging.

Repair mechanisms of bone marrow mesenchymal stem cells in myocardial infarction

The prognosis of patients with myocardial infarction (MI) and resultant chronic heart failure remains extremely poor despite advances in optimal medical therapy and interventional procedures. Animal experiments and clinical trials using adult stem cell therapy following MI have shown a global improvement of myocardial function. Bone marrow-derived mesenchymal stem cells (MSCs) hold promise for cardiac repair following MI, due to their multilineage, self-renewal and proliferation potential. In addition, MSCs can be easily isolated, expanded in culture, and have immunoprivileged properties to the host tissue. Experimental studies and clinical trials have revealed that MSCs not only differentiate into cardiomyocytes and vascular cells, but also secrete amounts of growth factors and cytokines which may mediate endogenous regeneration via activation of resident cardiac stem cells and other stem cells, as well as induce neovascularization, anti-inflammation, anti-apoptosis, anti-remodelling and cardiac contractility in a paracrine manner. It has also been postulated that the anti-arrhythmic and cardiac nerve sprouting potential of MSCs may contribute to their beneficial effects in cardiac repair. Most molecular and cellular mechanisms involved in the MSC-based therapy after MI are still unclear at present. This article reviews the potential repair mechanisms of MSCs in the setting of MI.

An improved transplantation strategy for mouse mesenchymal stem cells in an acute myocardial infarction model

To develop an effective therapeutic strategy for cardiac regeneration using bone marrow mesenchymal stem cells (BM-MSCs), the primary mouse BM-MSCs (1^st BM-MSCs) and 5^th passage BM-MSCs from β-galactosidase transgenic mice were respectively intramyocardially transplanted into the acute myocardial infarction (AMI) model of wild type mice. At the 6^th week, animals/tissues from the 1^st BM-MSCs group, the 5^th passage BM-MSCs group, control group were examined. Our results revealed that, compared to the 5^th passage BM-MSCs, the 1^st BM-MSCs had better therapeutic effects in the mouse MI model. The 1^st BM-MSCs maintained greater differentiation potentials towards cardiomocytes or vascular endothelial cells in vitro. This is indicated by higher expressions of cardiomyocyte and vascular endothelial cell mature markers in vitro. Furthermore, we identified that 24 proteins were down-regulated and 3 proteins were up-regulated in the 5^th BM-MSCs in comparison to the 1^st BM-MSCs, using mass spectrometry following two-dimensional electrophoresis. Our data suggest that transplantation of the 1^st BM-MSCs may be an effective therapeutic strategy for cardiac tissue regeneration following AMI, and altered protein expression profiles between the 1^st BM-MSCs and 5^th passage BM-MSCs may account for the difference in their maintenance of stemness and their therapeutic effects following AMI.

Novel therapy for myocardial infarction: can HGF/Met be beneficial?

Myocardial infarction (MI) is a leading cause of hospitalization worldwide. A recently developed strategy to improve the management of MI is based on the use of growth factors which are able to enhance the intrinsic capacity of the heart to repair itself or regenerate after damage. Among others, hepatocyte growth factor (HGF) has been proposed as a modulator of cardiac repair of damage due to the pleiotropic effects elicited by Met receptor stimulation. In this review we describe the mechanistic basis for autocrine and paracrine protection of HGF in the injured heart. We also analyse the role of HGF/Met in stem cell maintenance and in stem cell therapies for MI. Finally, we summarize the most significant results on the use of HGF in experimental models of heart injury and discuss the potential of the molecule for treating ischaemic heart disease in humans.

Hepatocyte growth factor modification promotes the amelioration effects of human umbilical cord mesenchymal stem cells on rat acute kidney injury

Human umbilical cord-derived mesenchymal stem cells (hucMSCs) are particularly attractive cells for cellular and gene therapy in acute kidney injury (AKI). Adenovirus-mediated gene therapy has been limited by immune reaction and target genes selection. However, in the present study, we investigated the therapeutic effects of hepatocyte growth factor modified hucMSCs (HGF-hucMSCs) in ischemia/reperfusion-induced AKI rat models. In vivo animal models were generated by subjecting to 60 min of bilateral renal injury by clamping the renal pedicles and then introduced HGF-hucMSCs via the left carotid artery. Our results revealed that serum creatinine and urea nitrogen levels decreased to the baseline more quickly in HGF-hucMSCs-treated group than that in hucMSCs- or green fluorescent protein-hucMSCs-treated groups at 72 h after injury. The percent of proliferating cell nuclear antigen-positive cells in HGF-hucMSCs-treated group was higher than that in the hucMSCs or green fluorescent protein-hucMSCs-treated groups. Moreover, injured renal tissues treated with HGF-hucMSCs also exhibited less hyperemia and renal tubule cast during the recovery process. Immunohistochemistry and living body imaging confirmed that HGF-hucMSCs localize to areas of renal injury. Real-time polymerase chain reaction result showed that HGF-hucMSCs also inhibited caspase-3 and interleukin-1β mRNA expression in injured renal tissues. Western blot also showed HGF-hucMSCs-treated groups had lower expression of interleukin-1β. Terminal deoxynucleotidyl transferase biotin-deoxyuridine triphosphate (dUTP) nick end labeling method indicated that HGF-hucMSCs-treated group had the least apoptosis cells. In conclusion, our findings suggest that HGF modification promotes the amelioration of ischemia/reperfusion-induced rat renal injury via antiapoptotic and antiinflammatory mechanisms; thus, providing a novel therapeutic application for hucMSCs in AKI.

Hepatocyte growth factor/Met gene transfer in cardiac stem cells--potential for cardiac repair

The adult heart has been recently recognized as a self-renewing organ that contains a pool of committed resident cardiac stem cells (CSCs) and cardiac progenitor cells (CPCs). These adult CSCs and CPCs can be induced by cytokines and growth factors to migrate, differentiate, and proliferate in situ and potentially replace lost cardiomyocytes. Ligand-receptor systems, such as the tyrosine kinase receptor mesenchymal-epithelial transition factor (Met) and its ligand hepatocyte growth factor (HGF), are potential candidates for boosting migration, engraftment and commitment of CSCs. Here, we discuss the possible application of HGF/Met gene therapy to enhance the ability of CSCs to promote myocardial regeneration.

Non-viral gene therapy for myocardial engineering

Despite significant advances in surgical and pharmacological techniques, myocardial infarction (MI) remains the main cause of morbidity in the developed world because no remedy has been found for the regeneration of infarcted myocardium. Once the blood supply to the area in question is interrupted, the inflammatory cascade, among other mechanisms, results in the damaged tissue becoming a scar. The goals of cardiac gene therapy are essentially to minimize damage, to promote regeneration, or some combination thereof. While the vector is, in theory, less important than the gene being delivered, the choice of vector can have a significant impact. Viral therapies can have very high transfection efficiencies, but disadvantages include immunogenicity, retroviral-mediated insertional mutagenesis, and the expense and difficulty of manufacture. For these reasons, researchers have focused on non-viral gene therapy as an alternative. In this review, naked plasmid delivery, or the delivery of complexed plasmids, and cell-mediated gene delivery to the myocardium will be reviewed. Pre-clinical and clinical trials in the cardiac tissue will form the core of the discussion. While unmodified stem cells are sometimes considered therapeutic vectors on the basis of paracrine mechanisms of action basic understanding is limited. Thus, only genetically modified cells will be discussed as cell-mediated gene therapy.

Modification of mesenchymal stem cells for cardiac regeneration

IMPORTANCE OF THE FIELD

Mesenchymal stem cells (MSCs) have the greatest potential for use in cell-based therapy of human heart diseases, especially in myocardial infarcts. The therapeutic potential of MSCs in myocardial repair is based on the ability of MSCs to directly differentiate into cardiac tissue and on the paracrine actions of factors released from MSCs. However, the major obstacle in the clinical application of MSC-based therapy is the poor viability of the transplanted cells due to harsh microenvironments like ischemia, inflammation and/or anoikis in the infarcted myocardium. Recently, various approaches have been implemented in an effort to improve the survival of implanted MSCs through ex vivo manipulation of MSCs.

AREAS COVERED IN THIS REVIEW

Major obstacles in MSC-based therapy are discussed, along with recent advances for enhancing therapeutic potential of engrafted MSCs from the past decade.

WHAT THE READER WILL GAIN

This review focuses primarily on ex vivo manipulation of MSCs before transplantation, which includes pretreatment, preconditioning and genetic modification of MSCs, and future directions.

TAKE HOME MESSAGE

Modification of MSCs before transplantation has developed into a promising option for enhancing the beneficial effects of MSC-based therapy for cardiac repair after myocardial infarction.

Tissue-engineered pro-angiogenic fibroblast scaffold improves myocardial perfusion and function and limits ventricular remodeling after infarction

OBJECTIVE

Microvascular malperfusion after myocardial infarction leads to infarct expansion, adverse remodeling, and functional impairment. Native reparative mechanisms exist but are inadequate to vascularize ischemic myocardium. We hypothesized that a 3-dimensional human fibroblast culture (3DFC) functions as a sustained source of angiogenic cytokines, thereby augmenting native angiogenesis and limiting adverse effects of myocardial ischemia.

METHODS

Lewis rats underwent ligation of the left anterior descending coronary artery to induce heart failure; experimental animals received a 3DFC scaffold to the ischemic region. Border-zone tissue was analyzed for the presence of human fibroblast surface protein, vascular endothelial growth factor, and hepatocyte growth factor. Cardiac function was assessed with echocardiography and pressure-volume conductance. Hearts underwent immunohistochemical analysis of angiogenesis by co-localization of platelet endothelial cell adhesion molecule and alpha smooth muscle actin and by digital analysis of ventricular geometry. Microvascular angiography was performed with fluorescein-labeled lectin to assess perfusion.

RESULTS

Immunoblotting confirmed the presence of human fibroblast surface protein in rats receiving 3DFC, indicating survival of transplanted cells. Increased expression of vascular endothelial growth factor and hepatocyte growth factor in experimental rats confirmed elution by the 3DFC. Microvasculature expressing platelet endothelial cell adhesion molecule/alpha smooth muscle actin was increased in infarct and border-zone regions of rats receiving 3DFC. Microvascular perfusion was also improved in infarct and border-zone regions in these rats. Rats receiving 3DFC had increased wall thickness, smaller infarct area, and smaller infarct fraction. Echocardiography and pressure-volume measurements showed that cardiac function was preserved in these rats.

CONCLUSIONS

Application of a bioengineered 3DFC augments native angiogenesis through delivery of angiogenic cytokines to ischemic myocardium. This yields improved microvascular perfusion, limits infarct progression and adverse remodeling, and improves ventricular function.

Relative roles of direct regeneration versus paracrine effects of human cardiosphere-derived cells transplanted into infarcted mice

RATIONALE

Multiple biological mechanisms contribute to the efficacy of cardiac cell therapy. Most prominent among these are direct heart muscle and blood vessel regeneration from transplanted cells, as opposed to paracrine enhancement of tissue preservation and/or recruitment of endogenous repair.

OBJECTIVE

Human cardiac progenitor cells, cultured as cardiospheres (CSps) or as CSp-derived cells (CDCs), have been shown to be capable of direct cardiac regeneration in vivo. Here we characterized paracrine effects in CDC transplantation and investigated their relative importance versus direct differentiation of surviving transplanted cells.

METHODS AND RESULTS

In vitro, many growth factors were found in media conditioned by human adult CSps and CDCs; CDC-conditioned media exerted antiapoptotic effects on neonatal rat ventricular myocytes, and proangiogenic effects on human umbilical vein endothelial cells. In vivo, human CDCs secreted vascular endothelial growth factor, hepatocyte growth factor, and insulin-like growth factor 1 when transplanted into the same SCID mouse model of acute myocardial infarction where they were previously shown to improve function and to produce tissue regeneration. Injection of CDCs in the peri-infarct zone increased the expression of Akt, decreased apoptotic rate and caspase 3 level, and increased capillary density, indicating overall higher tissue resilience. Based on the number of human-specific cells relative to overall increases in capillary density and myocardial viability, direct differentiation quantitatively accounted for 20% to 50% of the observed effects.

CONCLUSIONS

Together with their spontaneous commitment to cardiac and angiogenic differentiation, transplanted CDCs serve as "role models," recruiting endogenous regeneration and improving tissue resistance to ischemic stress. The contribution of the role model effect rivals or exceeds that of direct regeneration.

CXCR4 expression determines functional activity of bone marrow-derived mononuclear cells for therapeutic neovascularization in acute ischemia

OBJECTIVE

Bone marrow-derived mononuclear cells (BMCs) improve the functional recovery after ischemia. However, BMCs comprise a heterogeneous mixture of cells, and it is not known which cell types are responsible for the induction of neovascularization after cell therapy. Because cell recruitment is critically dependent on the expression of the SDF-1-receptor CXCR4, we examined whether the expression of CXCR4 may identify a therapeutically active population of BMCs.

METHODS AND RESULTS

Human CXCR4(+) and CXCR4(-) BMCs were sorted by magnetic beads. CXCR4(+) BMCs showed a significantly higher invasion capacity under basal conditions and after SDF-1 stimulation. Hematopoietic or mesenchymal colony-forming capacity did not differ between CXCR4(+) and CXCR4(-) BMCs. Injection of CXCR4(+) BMCs in mice after induction of hindlimb ischemia significantly improved the recovery of perfusion compared to injection of CXCR4(-) BMCs. Likewise, capillary density was significantly increased in CXCR4(+) BMC-treated mice. Because part of the beneficial effects of cell therapy were attributed to the release of paracrine effectors, we analyzed BMC supernatants for secreted factors. Importantly, supernatants of CXCR4(+) BMCs were enriched in the proangiogenic cytokines HGF and PDGF-BB.

CONCLUSIONS

CXCR4(+) BMCs exhibit an increased therapeutic potential for blood flow recovery after acute ischemia. Mechanistically, their higher migratory capacity and their increased release of paracrine factors may contribute to enhanced tissue repair.

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.

Inhibition of humoral response to allogeneic porcine mesenchymal stem cell with 12 days of tacrolimus

BACKGROUND

In vivo studies have highlighted allogeneic mesenchymal stem-cell (MSC) immunogenicity. We investigated in vitro MSC-immunosuppressive drugs interaction and further tested in vivo the humoral response to intracardiac allogeneic MSC transplantation in a mini-swine model receiving a short course of immunosuppression.

METHODS

For in vitro experiments, long-term culture MSCs were used. Immunosuppressive drugs tested were mycophenolate mofetil, cyclosporin, tacrolimus (TAC), sirolimus (SIR), and everolimus. Cell proliferation/viability was assessed on day 7. For each drug, the C50 was determined, and the agonistic effect between immunosuppressive drugs and MSCs on alloreactivity was measured in proliferation assay of MSC-peripheral blood mononuclear cell cultures. For in vivo experiments, one-haplotype swine leukocyte antigen class I and II mismatch (n=11) were used. Allogeneic MSCs were transplanted into ischemic myocardium. TAC was administered 12 days. Donor-specific antibody response was assessed by flow cytometry and complement-mediated cytotoxicity assay.

RESULTS

All drugs except TAC significantly decreased cell proliferation (from 17% to 62%). In MSC-peripheral blood mononuclear cell co-culture assay, MSCs' immunomodulatory properties were maintained when TAC or SIR were used. In vivo experiments showed that only 2 of 11 animals under TAC developed donor-specific antibodies. Importantly, sera from those two animals did not elicit a complement-mediated cytotoxic response.

CONCLUSIONS

Immunosuppressive drugs significantly affect proliferation and viability of MSCs, but neither TAC nor SIR had a detrimental impact on MSCs' immunomodulatory properties. In this large-animal model, addition of short course of immunosuppression seems to overcome the immune response to intracardiac allogeneic MSCs, which was recently demonstrated to occur in the absence of immunosuppression.

Role of paracrine factors in stem and progenitor cell mediated cardiac repair and tissue fibrosis

A new era has begun in the treatment of ischemic disease and heart failure. With the discovery that stem cells from diverse organs and tissues, including bone marrow, adipose tissue, umbilical cord blood, and vessel wall, have the potential to improve cardiac function beyond that of conventional pharmacological therapy comes a new field of research aiming at understanding the precise mechanisms of stem cell-mediated cardiac repair. Not only will it be important to determine the most efficacious cell population for cardiac repair, but also whether overlapping, common mechanisms exist. Increasing evidence suggests that one mechanism of action by which cells provide tissue protection and repair may involve paracrine factors, including cytokines and growth factors, released from transplanted stem cells into the surrounding tissue. These paracrine factors have the potential to directly modify the healing process in the heart, including neovascularization, cardiac myocyte apoptosis, inflammation, fibrosis, contractility, bioenergetics, and endogenous repair.

Mesenchymal stem cell transplantation attenuates cardiac fibrosis associated with isoproterenol-induced global heart failure

We aimed to examine the ability of transplanted mesenchymal stem cells (MSCs) to attenuate cardiac fibrosis caused by global heart failure, and investigate the mechanisms that are possibly mediating this effect. Global heart failure was induced in Wistar rats by isoproterenol injection. Four weeks later, MSCs were transplanted by intramyocardial injection, while control groups were treated by injection of cell culture medium alone. Four weeks after transplantation, heart function was assessed, and histologic and molecular analyses conducted. Compared with the medium-treated group, MSC transplantation significantly decreased the expression of collagens I and III, and matrix metalloproteinase 2 and 9, but heart function was improved in MSC-treated animals. In addition, expression of antifibrotic factor, hepatocyte growth factor (HGF), was detected in cultured MSCs, suggesting a possible mechanism underlying antifibrotic effects. Importantly, HGF expression levels were higher in MSC-treated hearts, compared with medium-treated hearts. Therefore, we could conclude that MSC transplantation can attenuate myocardial fibrosis in a rat model of global heart failure, and this may be at least partially mediated by paracrine signaling from MSCs via antifibrotic factors such as HGF.

Quantitative MR measurements of regional and global left ventricular function and strain after intramyocardial transfer of VM202 into infarcted swine myocardium

Previous studies have shown the beneficial effects of the hepatocyte growth factor (HGF) gene on myocardial perfusion and infarction size but not on the regional strain in relationship to global left ventricular function. A noninvasive magnetic resonance (MR) study was performed to determine the effect of a new HGF gene, VM202, expressing two isoforms of HGF, on regional and global left ventricular function. Pigs (8/group) were divided into three groups: 1) controls without infarction; 2) reperfused, infarcted controls; and 3) infarcted, treated (1 h after reperfusion) with VM202 injected at eight sites. Cine, tagging, and delayed enhancement MR images were acquired at 3 and 50 +/- 3 days after infarction. At 50 days, ejection fraction in infarcted, treated animals increased (38 +/- 1% to 47 +/- 2%, P < 0.01) to the level of controls without infarction (52 +/- 1%, P = 0.16) but decreased in infarcted controls (41 +/- 1% to 37 +/- 1%, P < 0.05). Two-dimensional strain improved in remote, peri-infarcted, and infarcted myocardium. Furthermore, the infarction size was smaller in infarcted, treated animals (7.0 +/- 0.5%) compared with infarcted controls (13.2 +/- 1.6%, P < 0.05). Histopathology showed a lack of hypertrophy in myocytes in peri-infarcted and remote myocardium and the formation of islands/peninsulas of myocytes in infarcted, treated animals but not in infarcted controls. In conclusion, the plasmid HGF gene caused a near complete recovery of ejection fraction and improved the radial and circumferential strain of remote, peri-infarcted, and infarcted regions within 50 days. These beneficial effects may be explained by the combined effects of a speedy and significant infarct resorption and island/peninsulas of hypertrophied myocytes within the infarcted territory but not by compensatory hypertrophy. The combined use of cine and tagging MR imaging provides valuable information on the efficacy of gene therapy.