Embryonic stem cells attenuate myocardial dysfunction and inflammation after surgical global ischemia via paracrine actions

Stem cell treatment may positively influence recovery and inflammation after shock by multiple mechanisms, including the paracrine release of protective growth factors. Embryonic stem cells (ESCs) are understudied and may have greater protective power than adult bone marrow stem cells (BMSCs). We hypothesized that ESC paracrine protective mechanisms in the heart (decreased injury by enhanced growth factor-mediated reduction of proinflammatory cytokines) would be superior to the paracrine protective mechanisms of the adult stem cell population in a model of surgically induced global ischemia. Adult Sprague-Dawley rat hearts were isolated and perfused via Langendorff model. Hearts were subjected to 25 min of warm global ischemia and 40 min of reperfusion and were randomly assigned into one of four groups: 1) vehicle treated; 2) BMSC or ESC preischemic treatment; 3) BMSC or ESC postischemic treatment; and 4) BMSC- or ESC-conditioned media treatment. Myocardial function was recorded, and hearts were analyzed for expression of tissue cytokines and growth factors (ELISA). Additionally, ESCs and BMSCs in culture were assessed for growth factor production (ELISA). ESC-treated hearts demonstrated significantly greater postischemic recovery of function (left ventricular developed pressure, end-diastolic pressure, and maximal positive and negative values of the first derivative of pressure) than BMSC-treated hearts or controls at end reperfusion. ESC-conditioned media (without cells) also conferred cardioprotection at end reperfusion. ESC-infused hearts demonstrated increased VEGF and IL-10 production compared with BMSC hearts. ESC hearts also exhibited decreased proinflammatory cytokine expression compared with MSC hearts. Moreover, ESCs in cell culture demonstrated greater pluripotency than MSCs. ESC paracrine protective mechanisms in surgical ischemia are superior to those of adult stem cells.     

Neonatal stem cells exhibit specific characteristics in function, proliferation, and cellular signaling that distinguish them from their adult counterparts

Stem cells may be a novel treatment modality for organ ischemia, possibly through beneficial paracrine mechanisms. Stem cells from older hosts have been shown to exhibit decreased function during stress. We therefore hypothesized that 1) neonatal bone marrow mesenchymal stem cells (nBMSCs) would produce different levels of IL-6, VEGF, and IGF-1 compared with adults (aBMSCs) when stimulated with TNF or LPS; 2) differences in cytokines would be due to distinct cellular characteristics, such as proliferation or pluripotent potential; and 3) differences in cytokines would be associated with differences in p38 MAPK and ERK signaling within nBMSCs. BMSCs were isolated from adult and neonatal mice. Cells were exposed to TNF or LPS with or without p38 or ERK inhibition. Growth factors were measured via ELISA, proliferation via daily cell counts, cell surface markers via flow cytometry, and pluripotent potential via alkaline phosphatase activity. nBMSCs produced lower levels of IL-6 and VEGF, but higher levels of IGF-1 under basal conditions, as well as after stimulation with TNF, but not LPS. Neonatal and adult BMSCs had similar pluripotent potentials and cell surface markers, but nBMSCs proliferated faster. Furthermore, p38 and ERK appeared to play a more substantial role in nBMSC cytokine and growth factor production. Neonatal stem cells may aid in decreasing the local inflammatory response during ischemia, and could possibly be expanded more rapidly than adult cells prior to therapeutic use.     

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.     

TNFR1 signaling resistance associated with female stem cell cytokine production is independent of TNFR2-mediated pathways

End-organ ischemia is a common source of patient morbidity and mortality. Stem cell therapy represents a novel treatment modality for ischemic diseases and may aid injured tissues through the release of beneficial paracrine mediators. Female bone marrow mesenchymal stem cells (MSCs) have demonstrated a relative resistance to detrimental TNF receptor 1 (TNFR1) signaling and are thought to be superior to male stem cells in limiting inflammation. However, it is not known whether sex differences exist in TNF receptor 2 (TNFR2)-ablated MSCs. Therefore, we hypothesized that 1) sex differences would be observed in wild-type (WT) and TNFR2-ablated MSC cytokine signaling, and 2) the production of IL-6, VEGF, and IGF-1 in males, but not females, would be mediated through TNFR2. MSCs were harvested from male and female WT and TNFR2 knockout (TNFR2KO) mice and were subsequently exposed to TNF (50 ng/ml) or LPS (100 ng/ml). After 24 h, supernatants were collected and measured for cytokines. TNF and LPS stimulated WT stem cells to produce cytokines, but sex differences were only seen in IL-6 and IGF-1 after TNF stimulation. Ablation of TNFR2 increased VEGF and IGF-1 production in males compared with wild-type, but no difference was observed in females. Female MSCs from TNFR2KOs produced significantly lower levels of VEGF and IGF-1 compared with male TNFR2KOs. The absence of TNFR2 signaling appears to play a greater role in male MSC cytokine production. As a result, male, but not female stem cell cytokine production may be mediated through TNFR2 signaling cascades.     

Adropin-based dual treatment enhances the therapeutic potential of mesenchymal stem cells in rat myocardial infarction

Both weak survival ability of stem cells and hostile microenvironment are dual dilemma for cell therapy. Adropin, a bioactive substance, has been demonstrated to be cytoprotective. We therefore hypothesized that adropin may produce dual protective effects on the therapeutic potential of stem cells in myocardial infarction by employing an adropin-based dual treatment of promoting stem cell survival in vitro and modifying microenvironment in vivo. In the current study, adropin (25 ng/ml) in vitro reduced hydrogen peroxide-induced apoptosis in rat bone marrow mesenchymal stem cells (MSCs) and improved MSCs survival with increased phosphorylation of Akt and extracellular regulated protein kinases (ERK) l/2. Adropin-induced cytoprotection was blocked by the inhibitors of Akt and ERK1/2. The left main coronary artery of rats was ligated for 3 or 28 days to induce myocardial infarction. Bromodeoxyuridine (BrdU)-labeled MSCs, which were in vitro pretreated with adropin, were in vivo intramyocardially injected after ischemia, following an intravenous injection of 0.2 mg/kg adropin (dual treatment). Compared with MSCs transplantation alone, the dual treatment with adropin reported a higher level of interleukin-10, a lower level of tumor necrosis factor-α and interleukin-1β in plasma at day 3, and higher left ventricular ejection fraction and expression of paracrine factors at day 28, with less myocardial fibrosis and higher capillary density, and produced more surviving BrdU-positive cells at day 3 and 28. In conclusion, our data evidence that adropin-based dual treatment may enhance the therapeutic potential of MSCs to repair myocardium through paracrine mechanism via the pro-survival pathways.Subject terms: Cell death, Heart stem cells     

TGF-alpha increases human mesenchymal stem cell-secreted VEGF by MEK- and PI3-K- but not JNK- or ERK-dependent mechanisms

Transforming growth factor-alpha (TGF-alpha) may be an important mediator of wound healing and the injury response. Human bone marrow mesenchymal stem cells (MSCs) release VEGF as a potentially beneficial paracrine response; however, it remains unknown whether TGF-alpha stimulates the production of VEGF from MSCs and, if so, by which mechanisms. We hypothesized that TGF-alpha would increase human MSC VEGF production by MAP kinase kinase (MAPKK/MEK), phosphatidylinositol 3-kinase (PI3-K)-, ERK, and JNK-dependent mechanisms. To study this, MSCs were cultured and divided into the following groups: 1) with vehicle; 2) with various stimulants alone: TGF-alpha, TNF-alpha, or TGF-alpha+TNF-alpha; 3) with individual kinase inhibitors alone (two different inhibitors for each of the following kinases: MEK, PI3-K, ERK, or JNK); and 4) with the above stimulants and each of the eight inhibitors. After 24-h incubation, a TGF-alpha dose-response curve demonstrated that low-dose TGF-alpha (500 pg/ml) suppressed MSC production of VEGF compared with vehicle (502 +/- 16 pg/10(5) cells/ml to 332 +/- 9 pg/10(5) cells/ml), while high-dose TGF-alpha (250 ng/ml) significantly increased MSC VEGF production (603 +/- 24 pg/10(5) cells/ml). High-dose TGF-alpha also increased TNF-alpha-stimulated release of VEGF from MSCs. MSCs exposed to TGF-alpha and/or TNF-alpha also demonstrated increased activation of PI3-K, JNK, and ERK. The TGF-alpha-stimulated production of VEGF by MSCs and the additive effect of TNF-alpha and TGF-alpha on VEGF production were abolished by MEK and PI3-K inhibition, but not ERK or JNK inhibition. Our data suggest that TGF-alpha increases VEGF production in MSCs via MEK- and PI3-K- but not ERK- or JNK-dependent mechanisms.     

Mesenchymal stem cells secretome: The cornerstone of cell-free regenerative medicine

Mesenchymal stem cells (MSCs) are the most frequently used stem cells in clinical trials due to their easy isolation from various adult tissues, their ability of homing to injury sites and their potential to differentiate into multiple cell types. However, the realization that the beneficial effect of MSCs relies mainly on their paracrine action, rather than on their engraftment in the recipient tissue and subsequent differentiation, has opened the way to cell-free therapeutic strategies in regenerative medicine. All the soluble factors and vesicles secreted by MSCs are commonly known as secretome. MSCs secretome has a key role in cell-to-cell communication and has been proven to be an active mediator of immune-modulation and regeneration both in vitro and in vivo. Moreover, the use of secretome has key advantages over cell-based therapies, such as a lower immunogenicity and easy production, handling and storage. Importantly, MSCs can be modulated to alter their secretome composition to better suit specific therapeutic goals, thus, opening a large number of possibilities. Altogether these advantages now place MSCs secretome at the center of an important number of investigations in different clinical contexts, enabling rapid scientific progress in this field.     

Reduction of myocardial infarct size by human mesenchymal stem cell conditioned medium

Although paracrine effects of mesenchymal stem cells (MSCs) have been suggested previously, cardioprotection by human MSC secretions has never been demonstrated. Human MSC-conditioned medium (CM) was collected by following a clinically compliant protocol. In a porcine model of ischemia and reperfusion injury, intravenous and intracoronary MSC-CM treatment significantly reduced myocardial nuclear oxidative stress as determined by immunostaining for 8-hydroxy-2′-deoxyguanosine. In addition, expression levels of phospho-SMAD2 and active caspase 3 were diminished following CM treatment, suggesting that TGF-β signaling and apoptosis were reduced. This was associated with a 60% reduction in infarct size and marked improvement of systolic and diastolic cardiac performance as assessed with echocardiography and pressure volume loops. Fractionation studies revealed that only the fraction of the CM containing products > 1000 kDa (100–220 nm) provided cardioprotection in a mouse model of ischemia and reperfusion injury. This indicates that the responsible paracrine factor of human MSCs is likely a large complex rather than a single small molecule. These data identify human MSC-CM as a promising therapeutic option to reduce myocardial infarct size in patients with acute MI and suggest that the use of stem cell secretions could extend the applicability of stem cells for therapeutic purposes.     

Deleterious effects of endogenous and exogenous testosterone on mesenchymal stem cell VEGF production

Modulating the paracrine effects of bone marrow mesenchymal stem cells (BMSCs) may be important for the treatment of ischemic myocardial tissue. In this regard, endogenous estrogen may enhance BMSC vascular endothelial growth factor (VEGF) production. However, little information exists regarding the effect of testosterone on stem cell function. We hypothesized that 1) endogenous or exogenous estrogen will enhance stem cell production of VEGF and 2) endogenous or exogenous testosterone will inhibit BMSC VEGF production. BMSCs were collected from adult male, female, castrated male, and ovariectomized female rats. One hundred thousand cells were incubated with testosterone (1, 10, or 100 nM) or estrogen (0.15, 1.5, or 15 nM) for 48 h. Cell supernatants were collected, and VEGF was measured by ELISA. BMSCs harvested from castrated males, normal females, and ovariectomized females produced more VEGF compared with normal males. Castration was associated with the highest level (1,018 +/- 98.26 pg/ml) of VEGF production by BMSCs, which was significantly more than that produced by BMSCs harvested from normal male and normal female animals. Exogenous testosterone significantly reduced VEGF production in BMSCs harvested from ovariectomized females in a dose-dependent manner. Exogenous estrogen did not alter BMSC VEGF production. These findings suggest that testosterone may work on BMSCs to decrease protective growth factor production and that effective removal of testosterone's deleterious effects via castration may prove to be beneficial in terms of protective factor production. By manipulating the mechanisms that BMSCs use to produce growth factors, we may be able to engineer stem cells to produce maximum growth factors during therapeutic use.     

Mesenchymal stem cell-derived interleukin-6 and vascular endothelial growth factor promote breast cancer cell migration

Several different cytokines and growth factors secreted by mesenchymal stem cells (MSCs) have been hypothesized to play a role in breast cancer progression. By using a small panel of breast cancer cell lines (MCF‐7, T47D, and SK‐Br‐3 cells), we analyzed the role of interleukin‐6 (IL‐6) and vascular endothelial growth factor A (VEGF) in the cross‐talk between MSCs and breast cancer cells. We performed migration assays in which breast cancer cells were allowed to migrate in response to conditioned medium from MSCs (MSCs‐CM), in absence or in presence of the anti‐VEGF antibody bevacizumab or an anti‐IL‐6 antibody, alone or in combination. We found that anti‐VEGF and anti‐IL‐6 antibodies inhibited the migration of breast cancer cells and that the combination had an higher inhibitory effect. We next evaluated the effects of recombinant VEGF and IL‐6 proteins on breast cancer cell growth and migration. IL‐6 and VEGF had not significant effects on the proliferation of breast carcinoma cells. In contrast, both VEGF and IL‐6 significantly increased the ability to migrate of MCF‐7, T47D and SK‐Br‐3 cells, with the combination showing a greater effect as compared with treatment with a single protein. The combination of VEGF and IL‐6 produced in breast cancer cells a more significant and more persistent activation of MAPK, AKT, and p38MAPK intracellular signaling pathways. These results suggest that MSC‐secreted IL‐6 and VEGF may act as paracrine factors to sustain breast cancer cell migration. J. Cell. Biochem. 113: 3363–3370, 2012. © 2012 Wiley Periodicals, Inc.     

Adenoviral expression of vascular endothelial growth factor splice variants differentially regulate bone marrow-derived mesenchymal stem cells

Bone marrow-derived mesenchymal stem cells (MSCs) are being explored for clinical applications, and genetic engineering represents a useful strategy for boosting the therapeutic potency of MSCs. Vascular endothelial growth factor (VEGF)-based gene therapy protocols have been used to treat tissue ischemia, and a combined VEGF/MSC therapeutics is appealing due to their synergistic paracrine actions. However, multiple VEGF splice variants exhibit differences in their mitogenicity, chemotactic efficacy, receptor interaction, and tissue distribution, and the differential regulatory effects of multiple VEGF isoforms on the function of MSCs have not been characterized. We expressed three rat VEGF-A splice variants VEGF120, 164, and 188 in MSCs using adenoviral vectors, and analyzed their effects on MSC proliferation, differentiation, survival, and trophic factor production. The three VEGF splice variants exert common and differential effects on MSCs. All three expressed VEGFs are potent in promoting MSC proliferation. VEGF120 and 188 are more effective in amplifying expression of multiple growth factor and cytokine genes. VEGF164 on the other hand is more potent in promoting expression of genes associated with MSC remodeling and endothelial differentiation. The longer isoform VEGF188, which is preferentially retained by proteoglycans, facilitates bone morphogenetic protein-7 (BMP7)-mediated MSC osteogenesis. Under serum starvation condition, virally expressed VEGF188 preferentially enhances serum withdrawal-mediated cell death involving nitric oxide production. This work indicates that seeking the best possible match of an optimal VEGF isoform to a given disease setting can generate maximum therapeutic benefits and minimize unwanted side effects in combined stem cell and gene therapy.     

Mesenchymal stem cell therapy: A promising cell‐based therapy for treatment of myocardial infarction

For decades, mesenchymal stem (MSCs) cells have been used for cardiovascular diseases as regenerative therapy. This review is an attempt to summarize the types of MSCs involved in myocardial infarction (MI) therapy, as well as its possible mechanisms effects, especially the paracrine one in MI focusing on the studies (human and animal) conducted within the last 10 years. Recently, reports showed that MSC therapy could have infarct‐limiting effects after MI in both experimental and clinical trials. In this context, various types of MSCs can help cardiac regeneration by either revitalizing the cardiac stem cells or revascularizing the arteries and veins of the heart. Furthermore, MSCs could produce paracrine growth factors that increase the survival of nearby cardiomyocytes, as well as increase angiogenesis through recruitment of stem cell from bone marrow or inducing vessel growth from existing capillaries. Recent research suggests that the paracrine effects of MSCs could be mediated by extracellular vesicles including exosomes. Exosomal microRNAs (miRNAs) released by MSCs are promising therapeutic hotspot target for MI. This could be attributed to the role of miRNA in cardiac biology, including cardiac regeneration, stem cell differentiation, apoptosis, neovascularization, cardiac contractility and cardiac remodeling. Furthermore, gene‐modified MSCs could be a recent promising therapy for MI to enhance the paracrine effects of MSCs, including better homing and effective cell targeted tissue regeneration. Although MSC therapy has achieved considerable attention and progress, there are critical challenges that remains to be overcome to achieve the most effective successful cell‐based therapy in MI.     

The similar effect of transplantation of marrow-derived mesenchymal stem cells with or without prior differentiation induction in experimental myocardial infarction

Marrow-derived mesenchymal stem cells (MSCs) have been heralded as a source of great promise for the regeneration of the infarcted heart. There is no clear data indicating whether or not in vitro differentiation of MSCs into major myocardial cells can increase the beneficial effects of MSCs. The aim of this study is to address this issue. To induce MSCs to transdifferentiate into cardiomyocyte-like and endothelial-like cells, 5-azacytidine and vascular endothelial growth factor (VEGF) were used, respectively. Myocardial infarction in rabbits was generated by ligating the left anterior descending coronary artery. Animals were divided into three experimental groups: I, control group; II, undifferentiated mesenchymal stem cell transplantation group; III, differentiated mesenchymal stem cell transplantation group; which respectively received peri-infarct injections of culture media, autologous undifferentiated MSCs and autologous differentiated MSCs. General pathology, immunohistochemistry, electron microscopy and echocardiography were performed in order to search for myocardial regeneration and improvement of cardiac function. In Groups II and III, implanted cells transdifferentiate into myocardial cells within 28 days post injection in a similar manner, and well-developed ultra structures formed within transplanted cells. Improvements in left ventricular function and reductions in infarcted area were observed in both cell-transplanted groups to the same degree. Vascular density was similar in Groups II and III and significantly higher in these groups compared with the control group. There is no need for prior differentiation induction of marrow-derived MSCs before transplantation and peri-infarct implantation of MSCs can efficiently regenerate the infarcted myocardium and improve cardiac function.     

Paracrine effect of CXCR4‐overexpressing mesenchymal stem cells on ischemic heart injury

It has been reported that CXCR4‐overexpressing mesenchymal stem cells (MSC^CX4) can repair heart tissue post myocardial infarction. This study aims to investigate the MSCCX4‐derived paracrine cardio‐protective signaling in the presence of myocardial infarction. Mesenchymal stem cells (MSCs) were divided into 3 groups: MSC only, MSC^CX4, and CXCR4 gene‐specific siRNA‐transduced MSC. Mesenchymal stem cells were exposed to hypoxia, and then MSCs‐conditioned culture medium was incubated with neonatal and adult cardiomyocytes, respectively. Cell proliferation–regulating genes were assessed by real‐time polymerase chain reaction (RT‐PCR). In vitro: The number of cardiomyocytes undergoing DNA synthesis, cytokinesis, and mitosis was increased to a greater extent in MSC^CX4 medium‐treated group than control group, while this proproliferative effect was reduced in CXCR4 gene‐specific siRNA‐transduced MSC–treated cells. Accordingly, the maximal enhancement of vascular endothelial growth factor, cyclin 2, and transforming growth factor‐β2 was observed in hypoxia‐exposed MSC^CX4. In vivo: MSCs were labeled with enhanced green fluorescent protein (EGFP) and engrafted into injured myocardium in rats. The number of EGFP and CD31 positive cells in the MSC^CX4 group was significantly increased than other 2 groups, associated with the reduced left ventricular (LV) fibrosis, the increased LV free wall thickness, the enhanced angiogenesis, and the improved contractile function. CXCR4 overexpression can mobilize MSCs into ischemic area, whereby these cells can promoted angiogenesis and alleviate LV remodeling via paracrine signaling mechanism.     

Bronchioalveolar stem cells increase after mesenchymal stromal cell treatment in a mouse model of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) remains a major complication of prematurity resulting in significant morbidity and mortality. The pathology of BPD is multifactorial and leads to alveolar simplification and distal lung injury. Previous studies have shown a beneficial effect of systemic treatment with bone marrow-derived mesenchymal stromal cells (MSCs) and MSC-conditioned media (MSC-CM) leading to amelioration of the lung parenchymal and vascular injury in vivo in the hyperoxia murine model of BPD. It is possible that the beneficial response from the MSCs is at least in part due to activation of endogenous lung epithelial stem cells. Bronchioalveolar stem cells (BASCs) are an adult lung stem cell population capable of self-renewal and differentiation in culture, and BASCs proliferate in response to bronchiolar and alveolar lung injury in vivo. Systemic treatment of neonatal hyperoxia-exposed mice with MSCs or MSC-CM led to a significant increase in BASCs compared with untreated controls. Treatment of BASCs with MSC-CM in culture showed an increase in growth efficiency, indicating a direct effect of MSCs on BASCs. Lineage tracing data in bleomycin-treated adult mice showed that Clara cell secretory protein-expressing cells including BASCs are capable of contributing to alveolar repair after lung injury. MSCs and MSC-derived factors may stimulate BASCs to play a role in the repair of alveolar lung injury found in BPD and in the restoration of distal lung cell epithelia. This work highlights the potential important role of endogenous lung stem cells in the repair of chronic lung diseases.     

Paracrine action of HO-1-modified mesenchymal stem cells mediates cardiac protection and functional improvement

The aim has been to determine whether the supernatants of mesenchymal stem cells (MSCs) transfected with adenovirus carrying human heme oxygenase-1 (hHO-1) gene protect cardiomyocytes from ischemic injury. We have found that hHO-1 infected MSCs (hHO-1-MSCs) increased expression of hHO-1 protein. Apoptosis of cultured hHO-1-MSCs exposed to hypoxia was suppressed. Several cytokines, including HGF, bFGF, TGF-beta, VEGF and IL-1beta, were produced by hHO-1-MSCs, some being significantly enhanced under hypoxia stimulation. Meanwhile, those cytokines reduced caspase-3 level and activity in cultured adult rat ventricular cardiomyocytes (ARVCs) exposed to hypoxia. Supernatants obtained from hHO-1-MSCs improved left ventricular function, limited myocardial infarct size, increased microvessel density, and inhibited apoptosis of cardiomyocytes in rat myocardial infarction. It can be concluded hHO-1-modified MSCs prevent myocardial cell injury via secretion of paracrine-acting mediators.     

Sca-1+ cardiac stem cells mediate acute cardioprotection via paracrine factor SDF-1 following myocardial ischemia/reperfusion

Background

Cardiac stem cells (CSCs) promote myocardial recovery following ischemia through their regenerative properties. However, little is known regarding the implication of paracrine action by CSCs in the setting of myocardial ischemia/reperfusion (I/R) injury although it is well documented that non-cardiac stem cells mediate cardioprotection via the production of paracrine protective factors. Here, we studied whether CSCs could initiate acute protection following global myocardial I/R via paracrine effect and what component from CSCs is critical to this protection.

Methodology/Principal Findings

A murine model of global myocardial I/R was utilized to investigate paracrine effect of Sca-1+ CSCs on cardiac function. Intracoronary delivery of CSCs or CSC conditioned medium (CSC CM) prior to ischemia significantly improved myocardial function following I/R. siRNA targeting of VEGF in CSCs did not affect CSC-preserved myocardial function in response to I/R injury. However, differentiation of CSCs to cardiomyocytes (DCSCs) abolished this protection. Through direct comparison of the protein expression profiles of CSCs and DCSCs, SDF-1 was identified as one of the dominant paracrine factors secreted by CSCs. Blockade of the SDF-1 receptor by AMD3100 or downregulated SDF-1 expression in CSCs by specific SDF-1 siRNA dramatically impaired CSC-induced improvement in cardiac function and increased myocardial damage following I/R. Of note, CSC treatment increased myocardial STAT3 activation after I/R, whereas downregulation of SDF-1 action by blockade of the SDF-1 receptor or SDF-1 siRNA transfection abolished CSC-induced STAT3 activation. In addition, inhibition of STAT3 activation attenuated CSC-mediated cardioprotection following I/R. Finally, post-ischemic infusion of CSC CM was shown to significantly protect I/R-caused myocardial dysfunction.

Conclusions/Significance

This study suggests that CSCs acutely improve post-ischemic myocardial function through paracrine factor SDF-1 and up-regulated myocardial STAT3 activation.     

Erratum to: Mechanistic insight of platelet apoptosis leading to non-surgical bleeding among heart failure patients supported by continuous-flow left ventricular assist devices

Cardiosphere-derived cells (CDCs) and bone marrow mesenchymal stem cells (MSCs) are popularly used in stem cell therapy for myocardial regeneration. The cell type that survives and maintains stem cell characteristics in the adverse microenvironment following ischemia–reperfusion injury is presumed to be ideal for transplantation. The study was therefore aimed at identifying the cell type with relatively greater resistance to ischemia–reperfusion injury. CDCs were isolated from the right atrial appendage and MSCs from bone marrow of patients who underwent coronary artery bypass graft surgery. Ischemia–reperfusion injury was simulated in vitro by subjecting the cells to hypoxia (0.5% O₂) followed by reintroduction of oxygen (HR injury). Greater resistance of CDCs to HR injury was apparent from the decreased expression of senescence markers and lower proportion of apoptotic cells (one-sixth of that in MSCs). HR injury retarded cell cycle progression in MSCs. Consequent to HR injury, cell migration and secretion of stromal-derived growth factor were stimulated, significantly in CDCs. The differentiation to myocyte lineage and angiogenesis assessed by tube formation ability was better for CDCs. Release of vascular endothelial growth factor was relatively more in CDCs and was further stimulated by HR injury. Differentiation to osteogenic and angiogenic lineage was stimulated by HR injury in MSCs. Compared to MSCs, CDCs appear to be the cell of choice for promoting myocardial regeneration by virtue of its survival capacity in the event of ischemic insult along with higher proliferation rate, migration efficiency, release of growth factors with paracrine effects and differentiation to cardiac lineage.