Stem cell-based therapies in ischemic heart diseases: a focus on aspects of microcirculation and inflammation

AhR-STAT3-HO-1/COX-2 signalling pathway may restrict ferroptosis and improve hMSC accumulation and efficacy in mouse liver

BACKGROUND AND PURPOSE

The low efficacy of mesenchymal stem cells (MSCs) has restricted their application in the treatment of liver disease. Emerging evidence suggested that ferroptosis may provoke hepatocyte dysfunction and exacerbate damage to the liver microenvironment. Here, we have investigated the contribution of liver ferroptosis to the elimination and effectiveness of human MSC (hMSC). Furthermore, potential links between liver ferroptosis and aryl hydrocarbon receptors (AhR) were explored.

EXPERIMENTAL APPROACH

Two mouse models, iron supplement-induced hepatic ferroptosis and hepatic ischaemia/reperfusion (I/R) injury, were used to identify effects of ferroptosis on hMSC pharmacokinetics (PK)/pharmacodynamics (PD).

KEY RESULTS

AhR inhibition attenuated hepatic ferroptosis and improved survival of hMSCs. hMSC viability was decreased by iron supplementation or serum from I/R mice. The AhR antagonist CH223191 reversed iron overload and oxidative stress induced by ferroptosis and increased hMSC concentration and efficacy in mouse models. Effects of CH223191 were greater than those of deferoxamine, a conventional ferroptosis inhibitor. Transcriptomic results suggested that the AhR-signal transducer and activator of transcription 3 (STAT3)-haem oxygenase 1/COX-2 signalling pathway is critical to this process. These results were confirmed in a mouse model of hepatic I/R injury. In mice pre-treated with CH223191, hMSC exhibited more potent protective effects, linked to decreased hepatic ferroptosis.

CONCLUSION AND IMPLICATIONS

Our findings showed that ferroptosis was a critical factor in determining the fate of hMSCs. Inhibition of AhR decreased hepatic ferroptosis, thereby increasing survival and therapeutic effects of hMSCs in mouse models of liver disease.

Melatonin-pretreated human umbilical cord mesenchymal stem cells improved endometrium regeneration and fertility recovery through macrophage immunomodulation in rats with intrauterine adhesions†

Intrauterine adhesions (IUA) are a common gynecological problem. Stem cell therapy has been widely used in the treatment of IUA. However, due to the complex and harsh microenvironment of the uterine cavity, the effectiveness of such therapy is greatly inhibited. This study aimed to investigate whether melatonin pretreatment enhances the efficacy of human umbilical cord mesenchymal stem cells (HucMSCs) in IUA treatment in rats. First, we explored the effect of melatonin on the biological activity of HucMSCs in vitro through a macrophage co-culture system, Cell Counting Kit 8 (CCK-8), 5-Ethynyl-2'-deoxyuridine (EdU), flow cytometry, immunofluorescence staining, and qRT-PCR. Subsequently, we established the IUA rat model and tracked the distribution of HucMSCs in this model. In addition, we observed the number of M1 and M2 macrophages through immunofluorescence staining and detected the levels of inflammatory cytokines. Four weeks after cell transplantation, HE, Masson, and immunohistochemical staining were performed. In vitro experiments showed that melatonin pretreatment of HucMSCs promoted proliferation, reduced apoptosis, up-regulated the stemness gene, and regulated macrophage polarization. In vivo, melatonin pretreatment caused more HucMSCs to remain in the uterine cavity. Melatonin-pretreated HucMSCs recruited more macrophages, regulated macrophage polarization, and reduced inflammation. Melatonin-pretreated HucMSCs relieved fibrosis, increased endometrium thickness, and up-regulated CD34, vimentin, proliferating cell nuclear antigen (PCNA), and alpha small muscle antigen (α-SMA) expression. Fertility tests showed that melatonin-pretreated HucMSCs increased the number of embryos. In summary, pretreatment with melatonin was beneficial for HucMSC treatment because it enhanced the cell's ability to recruit macrophages and regulate macrophage polarization, which led to the regeneration of the endometrium and improved pregnancy outcomes.

Synergistic Therapeutic Potential of Dual 3D Mesenchymal Stem Cell Therapy in an Ischemic Hind Limb Mouse Model

Three-dimensional (3D) culture systems have been widely used to promote the viability and metabolic activity of mesenchymal stem cells (MSCs). The aim of this study was to explore the synergistic benefits of using dual 3D MSC culture systems to promote vascular regeneration and enhance therapeutic potential. We used various experimental assays, including dual 3D cultures of human adipose MSCs (hASCs), quantitative reverse transcription polymerase chain reaction (qRT-PCR), in vitro cell migration, Matrigel tube network formation, Matrigel plug assay, therapeutic assays using an ischemic hind limb mouse model, and immunohistochemical analysis. Our qRT-PCR results revealed that fibroblast growth factor 2 (FGF-2), granulocyte chemotactic protein-2 (GCP-2), and vascular endothelial growth factor-A (VEGF-A) were highly upregulated in conventional 3D-cultured hASCs (ASC-3D) than in two-dimensional (2D)-cultured hASCs. Hepatocyte growth factor (HGF), insulin-like growth factor-1 (IGF-1), and stromal-cell-derived factor-1 (SDF-1) showed higher expression levels in cytokine-cocktail-based, 3D-cultured hASCs (ASC-3Dc). A conditioned medium (CM) mixture of dual 3D ASCs (D-3D; ASC-3D + ASC-3Dc) resulted in higher migration and Matrigel tube formation than the CM of single 3D ASCs (S-3D; ASC-3D). Matrigel plugs containing D-3D contained more red blood cells than those containing S-3D. D-3D transplantation into ischemic mouse hind limbs prevented limb loss and augmented blood perfusion when compared to S-3D transplantation. Transplanted D-3D also revealed a high capillary density and angiogenic cytokine levels and transdifferentiated into endothelial-like cells in the hind limb muscle. These findings highlight the benefits of using the dual 3D culture system to optimize stem-cell-based therapeutic strategies, thereby advancing the therapeutic strategy for ischemic vascular disease and tissue regeneration.

Pleiotrophin attenuates the senescence of dental pulp stem cells

OBJECTIVES

Pleiotrophin (PTN), a secreted extracellular matrix-associated protein, plays an important role in regulating the osteo/dentinogenic differentiation potential of dental pulp stem cells (DPSCs). Our previous study has demonstrated that PTN expression in young DPSCs was is 10-fold higher than that in aged DPSCs. However, the role of PTN on the in maintaining the stemness of senescent DPSCs remains unclear. The present study aimed to investigate the effect of PTN on senescent DPSCs in vitro.

MATERIALS AND METHODS

Dental pulp stem cells were isolated from human third molars. PTN was knocked down using short hairpin RNAs to study the role of PTN on the senescence of DPSCs. DPSCs with aging performance were obtained by a replicative senescence cell model was obtained by the long-term culture of DPSCs to the 15th passage in vitro (P15). We then investigated the effect of PTN on senescent DPSCs (P15 DPSCs). Real-time RT-PCR, western blotting, alizarin red staining, quantitative calcium analysis, SA-β-Gal staining, CFSE, and cell-counting kit-8 (CCK8) assays were used to study cellular senescence and function.

RESULTS

The depletion of PTN increased the ratio of SA-β-gal-positive cells, upregulated the expression of p16, and down-regulated the expression of TERT and p-p38. Furthermore, 50 pg/ml of PTN recombinant protein rescued these changes the altered ratio of SA-β-gal-positive cells, decreased the expression of p16, enhanced TERT and p-p38 expression, as well as telomere activity, caused by PTN depletion and long-term culture. The15th passage cells displayed typical aging characteristic, including high ratio of SA-β-gal-positive cells, increased aging-related gene expression, decreased proliferation rate, high level of Cyclin D expression, and impaired osteo/dentinogenic differentiation potential. However, 50 pg/ml of PTN recombinant protein could partially reverse these alteration rescue these changes.

CONCLUSIONS

The present study demonstrated that PTN could protect DPSCs from senescence by improving the proliferation and osteo/dentinogenic differentiation ability, probably through the p38 MAPK pathway.

Metformin protects against pericyte apoptosis and promotes neurogenesis through suppressing JNK p38 MAPK signalling activation in ischemia/reperfusion injury

Metformin (MET) has been the subject of many classic studies in possessing antiapoptotic, anti-inflammatory, antioxidation activities and antiviral. Recently investigators have examined the anti-apoptosis effects of MET in acute myocardial infarction and Intracerebral hemorrhage, but very little is currently known about how it regulates ischemic stroke-induced pericytes apoptosis and neural stem cells (NSCs) proliferation. The present research explored the potential neuroprotective mechanisms of MET using transient middle cerebral artery occlusion(tMCAO) mice. The experimental work presented that tMCAO mice treated by metformin had better neurologic outcomes on days 1, 3, and 7 after operation, and alleviated blood-brain barrier (BBB) destruction, brain water content and infarct volume on 72 h after surgery. The data showed that MET alleviated BBB disruption by reducing PDGFRβ/ matrix metalloproteinase-9 (MMP9) positive cells, relieving zonula occludens-1 (ZO-1) drop away and increasing pericyte coverage through remarkably reducing the percentage of PDGFRβ/caspase-3 positive cells. In addition, MET induced antiapoptotic activity followed by downregulating cleaved caspase-3 and Bax expression. Moreover, JNK signaling pathway has been proved to be pivotal in mediating apoptosis in cerebral ischemia/reperfusion (I/R) injury. The results of this research illustrated that MET treatment downregulated the levels of phosphorylated JNK and P38 in vivo, however the use of JNK activator anisomycin (ANI) could reverse the neuroprotection effect of MET, demonstrating that the JNK pathway is associated with the anti-apoptosis mechanisms of MET. Finally, metformin remarkably increased the percentage of BrdU/DCX-positive cells in subventricular zone (SVZ) and up-regulated BDNF、VEGF and NGF expression after ischemia/reperfusion(I/R) injury on day 7. Our data illustrated that metformin provides an effective therapy for I/R injury.

Optimal Delivery Route of Mesenchymal Stem Cells for Cardiac Repair: The Path to Good Clinical Practice

Research has shown that mesenchymal stem cells (MSCs) could be a promising therapy for treating progressive heart disease. However, translation into clinics efficiently and successfully has proven to be much more complicated. Many questions remain for optimizing treatment. Application method influences destiny of MSCs and afterwards impacts results of procedure, yet there is no general agreement about most suitable method of MSC delivery in the clinical setting. Herein, we explain principle of most-frequent MSCs delivery techniques in cardiology. This chapter summarizes crucial translational obstacles of clinical employment of MSCs for cardiac repair when analysed trough a prism of latest research centred on different techniques of MSCs application.

ASC and SVF Cells Synergistically Induce Neovascularization in Ischemic Hindlimb Following Cotransplantation

Previously, we reported the angio-vasculogenic properties of human stromal vascular fraction (SVF) and adipose tissue-derived mesenchymal stem cells (ASCs). In this study, we investigated whether the combination of ASCs and SVF cells exhibited synergistic angiogenic properties. We conducted quantitative (q)RT-PCR, Matrigel plug, tube formation assays, and in vivo therapeutic assays using an ischemic hind limb mouse model. Immunohistochemical analysis was also conducted. qRT-PCR results revealed that FGF-2 was highly upregulated in ASCs compared with SVF, while PDGF-b and VEGF-A were highly upregulated in SVF. Conditioned medium from mixed cultures of ASCs and SVF (A+S) cells showed higher Matrigel tube formation and endothelial cell proliferation in vitro. A+S cell transplantation into ischemic mouse hind limbs strongly prevented limb loss and augmented blood perfusion compared with SVF cell transplantation. Transplanted A+S cells also showed high capillary density, cell proliferation, angiogenic cytokines, and anti-apoptotic potential in vivo compared with transplanted SVF. Our data indicate that A+S cell transplantation results in synergistic angiogenic therapeutic effects. Accordingly, A+S cell injection could be an alternative therapeutic strategy for treating ischemic diseases.

Kidney extracellular matrix hydrogel enhances therapeutic potential of adipose-derived mesenchymal stem cells for renal ischemia reperfusion injury

Stem cell-based therapy has been suggested as a promising option for the treatment of renal ischemia-reperfusion injury (IRI). However, how to efficiently deliver stem cells remains a challenge. In the present study, we firstly proposed the utilization of kidney extracellular matrix hydrogel (ECMH) as an injectable scaffold for delivering adipose-derived mesenchymal stem cells (ad-MSCs) into ischemic kidneys. A modified strategy of decellularization and gelation was introduced to prepare the ECMH, by which the bioactive ingredients were retained as much as possible. Bioluminescence living imaging and immunofluorescence revealed that ECMH could significantly elevate the retention and survival rate of transplanted ad-MSCs in damaged kidneys and reduce their escape rate to other organs, which consequently resulted to the enhanced therapeutic effect of ad-MSCs on renal IRI. Further, in vitro evidence demonstrated that ECMH could remarkably reduce the oxidative stress and apoptosis, promote the proliferation, secretion, and epithelial differentiation of ad-MSCs, as well as facilitate cell migration while acting as a sustained-release scaffold. This study establishes an effective approach to enhance the therapeutic potential of ad-MSCs for renal IRI. Our findings suggest that ECMH derived from organs or tissues would be a promising injectable scaffold for stem cell-based therapy. STATEMENT OF SIGNIFICANCE: It remains a challenge to efficiently deliver stem cells to target tissues, which may limit the clinical application of stem cell-based therapy. In this study, we developed a modified strategy of decellularization and gelation to prepare the kidney extracellular matrix hydrogel (ECMH). In vivo and in vitro evidence indicated that the kidney ECMH could improve the retention and survival rate, as well as multiple biological functions of adipose-derived mesenchymal stem cells, thereby contributing to the histological and functional recovery of injured kidneys induced by ischemia-reperfusion. Our findings highlight the use of organs or tissues derived ECMH as a promising stem cell delivery scaffold for tissue repair.

Mesenchymal Stem Cells: A New Generation of Therapeutic Agents as Vehicles in Gene Therapy

In recent years, mesenchymal stem cells (MSCs) as a new tool for therapeutic gene delivery in clinics have attracted much attention. Their advantages cover longer lifespan, better isolation, and higher transfection efficiency and proliferation rate. MSCs are the preferred approach for cell-based therapies because of their in vitro self-renewal capacity, migrating especially to tumor tissues, as well as anti-inflammatory and immunomodulatory properties. Therefore, they have considerable efficiency in genetic engineering for future clinical applications in cancer gene therapy and other diseases. For improving therapeutic efficiency, targeted therapy of cancers can be achieved through the sustained release of therapeutic agents and functional gene expression induction to the intended tissues. The development of a new vector in gene therapy can improve the durability of a transgene expression. Also, the safety of the vector, if administered systemically, may resolve several problems, such as durability of expression and the host immune response. Currently, MSCs are prominent candidates as cell vehicles for both preclinical and clinical trials due to the secretion of therapeutic agents in several cancers. In the present study, we discuss the status of gene therapy in both viral and non-viral vectors along with their limitations. Throughout this study, the use of several nano-carriers for gene therapy is also investigated. Finally, we critically discuss the promising advantages of MSCs in targeted gene delivery, tumor inhibition and their utilization as the gene carriers in clinical situations.

Exendin-4 protects the hearts of rats from ischaemia/reperfusion injury by boosting antioxidant levels and inhibition of JNK/p66 Shc/NADPH axis

Exendin-4, a glucagon-like peptide-1 receptor agonist, was shown to protect against cardiac ischaemia/reperfusion (I/R) injury by suppressing oxidative stress. p⁶⁶ Shc, a pro-oxidant and an apoptotic protein, is activated in the infarcted left ventricles (LVs) after induction of I/R. This study investigated if the cardiac protective effect of Exendin-4 against I/R injury in rats involves inhibition of p⁶⁶ Shc and to determine the underlying mechanisms behind this. Adult male rats (n = 12/group) were divided into four groups as a sham, a sham + Exendin-4, an I/R, and an I/R + Exendin-4. Exendin-4 was administered to rats 7 days before the induction of I/R. Ischaemia was induced by ligating the left anterior descending (LAD) coronary artery for 40 minutes followed by reperfusion for 10 minutes. The infarct myocardium was used for further analysis. Exendin-4 significantly reduced infarct area (by 62%), preserved LV function and lowered serum levels of LDH and CK-MB in I/R-induced rats. Also, it significantly reduced LV levels of ROS and MDA and protein levels of cytochrome-c and cleaved caspase-3 but significantly increased levels of glutathione (GSH) and manganese superoxide dismutase (MnSOD) in LVs of I/R rats indicating antioxidant and anti-apoptotic effects. Furthermore, it inhibited JNK and p⁶⁶ Shc activation and downregulated protein levels of p⁶⁶ Shc and NADPH oxidase with no effect on protein levels/activity of p53 and PKCβII. Of note, Exendin-4 also increased GSH and MnSOD in LVs of control rats. In conclusion, Exendin-4 cardioprotective effect in I/R hearts is mediated mainly by antioxidant effect and inhibition of JNK/P⁶⁶ Shc/NADPH oxidase.

Recombinant Klotho Protects Human Periodontal Ligament Stem Cells by Regulating Mitochondrial Function and the Antioxidant System during H2O2-Induced Oxidative Stress

Human periodontal ligament stem cells (hPDLSCs) are a favourable source for tissue engineering, but oxidative stress conditions during cell culture and transplantation could affect stem cell viability and stemness, leading to failed regeneration. The aim of this study was to evaluate the antioxidant and protective effects of Klotho, an antiageing protein, against cell damage and the loss of osteogenesis in hPDLSCs in H₂O₂-induced oxidative environments. H₂O₂ was used as an exogenous reactive oxygen species (ROS) to induce oxidative stress. Recombinant human Klotho protein was administered before H₂O₂ treatment. Multitechniques were used to assess antioxidant activity, cell damage, and osteogenic ability of hPDLSCs in oxidative stress and the effects of Klotho on hPDLSCs. Mitochondrial function was analyzed by an electron microscopy scan of cellular structure, mitochondrial DNA copy number, and cellular oxygen consumption rate (OCR). Furthermore, we explored the pathway by which Klotho may function to regulate the antioxidant system. We found that pretreatment with recombinant human Klotho protein could enhance SOD activity and reduce intracellular oxidative stress levels. Klotho reduced H₂O₂-induced cellular damage and eventually maintained the osteogenic differentiation potential of hPDLSCs. Notably, Klotho promoted mitochondrial function and activated antioxidants by negatively regulating the PI3K/AKT/FoxO1 pathway. The findings suggest that Klotho protein enhanced the antioxidative ability of hPDLSCs and protected stem cell viability and stemness from H₂O₂-induced oxidative stress by restoring mitochondrial functions and the antioxidant system.

Enhancement of Functionality and Therapeutic Efficacy of Cell-Based Therapy Using Mesenchymal Stem Cells for Cardiovascular Disease

Cardiovascular disease usually triggers coronary heart disease, stroke, and ischemic diseases, thus promoting the development of functional failure. Mesenchymal stem cells (MSCs) are cells that can be isolated from various human tissues, with multipotent and immunomodulatory characteristics to help damaged tissue repair and avoidance of immune responses. Much research has proved the feasibility, safety, and efficiency of MSC-based therapy for cardiovascular disease. Despite the fact that the precise mechanism of MSCs remains unclear, their therapeutic capability to treat ischemic diseases has been tested in phase I/II clinical trials. MSCs have the potential to become an effective therapeutic strategy for the treatment of ischemic and non-ischemic cardiovascular disorders. The molecular mechanism underlying the efficacy of MSCs in promoting engraftment and accelerating the functional recovery of injury sites is still unclear. It is hypothesized that the mechanisms of paracrine effects for the cardiac repair, optimization of the niche for cell survival, and cardiac remodeling by inflammatory control are involved in the interaction between MSCs and the damaged myocardial environment. This review focuses on recent experimental and clinical findings related to cardiovascular disease. We focus on MSCs, highlighting their roles in cardiovascular disease repair, differentiation, and MSC niche, and discuss their therapeutic efficacy and the current status of MSC-based cardiovascular disease therapies.

Pioglitazone Protects Mesenchymal Stem Cells against P-Cresol-Induced Mitochondrial Dysfunction via Up-Regulation of PINK-1

Mesenchymal stem cells (MSC) could be a candidate for cell-based therapy in chronic kidney disease (CKD); however, the uremic toxin in patients with CKD restricts the therapeutic efficacy of MSCs. To address this problem, we explored the effect of pioglitazone as a measure against exposure to the uremic toxin P-cresol (PC) in MSCs. Under PC exposure conditions, apoptosis of MSCs was induced, as well as PC-induced dysfunction of mitochondria by augmentation of mitofusion, reduction of mitophagy, and inactivation of mitochondrial complexes I and IV. Treatment of MSCs with pioglitazone significantly inhibited PC-induced apoptosis. Pioglitazone also prevented PC-induced mitofusion and increased mitophagy against PC exposure through up-regulation of phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK-1). Furthermore, pioglitazone protected against PC-induced mitochondrial dysfunction by increasing the cytochrome c oxidase subunit 4 (COX4) level and activating complexes I and IV, resulting in enhancement of proliferation. In particular, activation of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) regulated the pioglitazone-mediated up-regulation of PINK-1. These results indicate that pioglitazone protects MSCs against PC-induced accumulated mitochondrial dysfunction via the NF-κB–PINK-1 axis under P-cresol exposure conditions. Our study suggests that pioglitazone-treated MSCs could be a candidate for MSC-based therapy in patients with CKD.

c-Jun N-Terminal Kinases (JNKs) in Myocardial and Cerebral Ischemia/Reperfusion Injury

In this article, we review the literature regarding the role of c-Jun N-terminal kinases (JNKs) in cerebral and myocardial ischemia/reperfusion injury. Numerous studies demonstrate that JNK-mediated signaling pathways play an essential role in cerebral and myocardial ischemia/reperfusion injury. JNK-associated mechanisms are involved in preconditioning and post-conditioning of the heart and the brain. The literature and our own studies suggest that JNK inhibitors may exert cardioprotective and neuroprotective properties. The effects of modulating the JNK-depending pathways in the brain and the heart are reviewed. Cardioprotective and neuroprotective mechanisms of JNK inhibitors are discussed in detail including synthetic small molecule inhibitors (AS601245, SP600125, IQ-1S, and SR-3306), ion channel inhibitor GsMTx4, JNK-interacting proteins, inhibitors of mixed-lineage kinase (MLK) and MLK-interacting proteins, inhibitors of glutamate receptors, nitric oxide (NO) donors, and anesthetics. The role of JNKs in ischemia/reperfusion injury of the heart in diabetes mellitus is discussed in the context of comorbidities. According to reviewed literature, JNKs represent promising therapeutic targets for protection of the brain and the heart against ischemic stroke and myocardial infarction, respectively. However, different members of the JNK family exert diverse physiological properties which may not allow for systemic administration of non-specific JNK inhibitors for therapeutic purposes. Currently available candidate JNK inhibitors with high therapeutic potential are identified. The further search for selective JNK3 inhibitors remains an important task.

Stem Cell Therapies in Cardiovascular Disease

Despite considerable advances in medicine, cardiovascular disease is still rising, with ischemic heart disease being the leading cause of death and disability worldwide. Thus extensive efforts are continuing to establish effective therapeutic modalities that would improve both quality of life and survival in this patient population. Novel therapies are being investigated not only to protect the myocardium against ischemia-reperfusion injury but also to regenerate the heart. Stem cell therapy, such as potential use of human mesenchymal stem cells and induced pluripotent stem cells and their exosomes, will make it possible not only to address molecular mechanisms of cardiac conditioning, but also to develop new therapies for ischemic heart disease. Despite the studies and progress made over the last 15 years on the use of stem cell therapy for cardiovascular disease, the efforts are still in their infancy. Even though the expectations have been high, the findings indicate that most of the clinical trials generally have been small and the results inconclusive. Because of many negative findings, there is certain pessimism that cardiac cell therapy is likely to yield any meaningful results over the next decade or so. Similar to other new technologies, early failures are not unusual and they may be followed by impressive success. Nevertheless, there has been considerable attention to safety by the clinical investigators because the adverse events of stem cell therapy have been impressively rare. In summary, although regenerative biology might not help the cardiovascular patient in the near term, it is destined to do so over the next several decades.

Alignment of inducible vascular progenitor cells on a micro-bundle scaffold improves cardiac repair following myocardial infarction

Ischemic heart disease is still the leading cause of death even with the advancement of pharmaceutical therapies and surgical procedures. Early vascularization in the ischemic heart is critical for a better outcome. Although stem cell therapy has great potential for cardiovascular regeneration, the ideal cell type and delivery method of cells have not been resolved. We tested a new approach of stem cell therapy by delivery of induced vascular progenitor cells (iVPCs) grown on polymer micro-bundle scaffolds in a rat model of myocardial infarction. iVPCs partially reprogrammed from vascular endothelial cells (ECs) had potent angiogenic potential and were able to simultaneously differentiate into vascular smooth muscle cells (SMCs) and ECs in 2D culture. Under hypoxic conditions, iVPCs also secreted angiogenic cytokines such as vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) as measured by enzyme-linked immunosorbent assay (ELISA). A longitudinal micro-scaffold made from poly(lactic-co-glycolic acid) was sufficient for the growth and delivery of iVPCs. Co-cultured ECs and SMCs aligned well on the micro-bundle scaffold similarly as in the vessels. 3D cell/polymer micro-bundles formed by iVPCs and micro-scaffolds were transplanted into the ischemic myocardium in a rat model of myocardial infarction (MI) with ligation of the left anterior descending artery. Our in vivo data showed that iVPCs on the micro-bundle scaffold had higher survival, and better retention and engraftment in the myocardium than free iVPCs. iVPCs on the micro-bundles promoted better cardiomyocyte survival than free iVPCs. Moreover, iVPCs and iVPC/polymer micro-bundles treatment improved cardiac function (ejection fraction and fractional shortening, endocardial systolic volume) measured by echocardiography, increased vessel density, and decreased infarction size [endocardial and epicardial infarct (scar) length] better than untreated controls at 8 weeks after MI. We conclude that iVPCs grown on a polymer micro-bundle scaffold are new promising approach for cell-based therapy designed for cardiovascular regeneration in ischemic heart disease.

Potentiation of biological effects of mesenchymal stem cells in ischemic conditions by melatonin via upregulation of cellular prion protein expression

Mesenchymal stem cells (MSCs) are promising candidates for stem cell-based therapy in ischemic diseases. However, ischemic injury induces pathophysiological conditions, such as oxidative stress and inflammation, which diminish therapeutic efficacy of MSC-based therapy by reducing survival and functionality of transplanted MSCs. To overcome this problem, we explored the effects of melatonin on the proliferation, resistance to oxidative stress, and immunomodulatory properties of MSCs. Treatment with melatonin enhanced MSC proliferation and self-renewal via upregulation of cellular prion protein (PrP^C ) expression. Melatonin diminished the extent of MSC apoptosis in oxidative stress conditions by regulating the levels of apoptosis-associated proteins, such as BCL-2, BAX, PARP-1, and caspase-3, in a PrP^C -dependent manner. In addition, melatonin regulated the immunomodulatory effects of MSCs via the PrP^C -IDO axis. In a murine hind-limb ischemia model, melatonin-stimulated MSCs improved the blood flow perfusion, limb salvage, and vessel regeneration by lowering the extent of apoptosis of affected local cells and transplanted MSCs as well as by reducing infiltration of macrophages. These melatonin-mediated therapeutic effects were inhibited by silencing of PrP^C expression. Our findings for the first time indicate that melatonin promotes MSC functionality and enhances MSC-mediated neovascularization in ischemic tissues through the upregulation of PrP^C expression. In conclusion, melatonin-treated MSCs could provide a therapeutic strategy for vessel regeneration in ischemic disease, and the targeting of PrP^C levels may prove instrumental for MSC-based therapies.

Cardiosphere-Derived Cells Facilitate Heart Repair by Modulating M1/M2 Macrophage Polarization and Neutrophil Recruitment

Cardiosphere-derived cells (CDCs), one of the promising stem cell sources for myocardial repair, have been tested in clinical trials and resulted in beneficial effects; however, the relevant mechanisms are not fully understood. In this study, we examined the hypothesis that CDCs favor heart repair by switching the macrophages from a pro-inflammatory phenotype (M1) into a regulatory anti-inflammatory phenotype (M2). Macrophages from mice were cultured with CDCs-conditioned medium or with fibroblasts-conditioned medium as a control. Immunostaining showed that CDCs-conditioned medium significantly enhanced the expression of CD206 (a marker for M2 macrophages), but decreased the expression of CD86 (a marker for M1 macrophages) 3 days after culture. For animal studies, we used an acute myocardial infarction model of mice. We injected CDCs, fibroblasts, or saline only into the border zone of infarction. Then we collected the heart tissues for histological analysis 5 and 14 days after treatment. Compared with control animals, CDCs treatment significantly decreased M1 macrophages and neutrophils but increased M2 macrophages in the infarcted heart. Furthermore, CDCs-treated mice had reduced infarct size and fewer apoptotic cells compared to the controls. Our data suggest that CDCs facilitate heart repair by modulating M1/M2 macrophage polarization and neutrophil recruitment, which may provide a new insight into the mechanisms of stem cell-based myocardial repair.

Ultrasound-targeted microbubble destruction enhances delayed BMC delivery and attenuates post-infarction cardiac remodelling by inducing engraftment signals

Delayed administration of bone marrow cells (BMCs) at 2-4 weeks after successful reperfusion in patients with acute myocardial infarction (MI) does not improve cardiac function. The reduction in engraftment signals observed following this time interval might impair the effects of delayed BMC treatment. In the present study, we aimed to determine whether ultrasound-targeted microbubble destruction (UTMD) treatment could increase engraftment signals, enhance the delivery of delayed BMCs and subsequently attenuate post-infarction cardiac remodelling. A myocardial ischaemia/reperfusion (I/R) model was induced in Wistar rats via left coronary ligation for 45 min followed by reperfusion. Western blotting revealed that engraftment signals peaked at 7 days post-I/R and were dramatically lower at 14 days post-I/R. The lower engraftment signals at 14 days post-I/R could be triggered by UTMD treatment at a mechanical index of 1.0-1.9. The troponin I levels in the 1.9 mechanical index group were higher than in the other groups. Simultaneous haematoxylin and eosin staining and fluorescence revealed that the number of engrafted BMCs in the ischaemic zone was greater in the group treated with both UTMD and delayed BMC transplantation than in the control groups (P<0.05). Both UTMD and delayed BMC transplantation improved cardiac function and decreased cardiac fibrosis at 4 weeks after treatment, as compared with control groups (both P<0.05). Histopathology demonstrated that UTMD combined with delayed BMC transplantation increased capillary density, myocardial cell proliferation and c-kit⁺ cell proliferation. These findings indicated that UTMD treatment could induce engraftment signals and enhance homing of delayed BMCs to ischaemic myocardium, attenuating post-infarction cardiac remodelling by promoting neovascularization, cardiomyogenesis and expansion of cardiac c-kit⁺ cells.

Melatonin facilitates adipose-derived mesenchymal stem cells to repair the murine infarcted heart via the SIRT1 signaling pathway

Mesenchymal stem cells (MSCs)-based therapy provides a promising therapy for the ischemic heart disease (IHD). However, engrafted MSCs are subjected to acute cell death in the ischemic microenvironment, characterized by excessive inflammation and oxidative stress in the host's infarcted myocardium. Melatonin, an indole, which is produced by many organs including pineal gland, has been shown to protect bone marrow MSCs against apoptosis although the mechanism of action remains elusive. Using a murine model of myocardial infarction (MI), this study was designed to evaluate the impact of melatonin on adipose-derived mesenchymal stem cells (AD-MSCs)-based therapy for MI and the underlying mechanism involved with a focus on silent information regulator 1(SIRT1) signaling. Our results demonstrated that melatonin promoted functional survival of AD-MSCs in infarcted heart and provoked a synergetic effect with AD-MSCs to restore heart function. This in vivo effect of melatonin was associated with alleviated inflammation, apoptosis, and oxidative stress in infarcted heart. In vitro studies revealed that melatonin exert cytoprotective effects on AD-MSCs against hypoxia/serum deprivation (H/SD) injury via attenuating inflammation, apoptosis, and oxidative stress. Mechanistically, melatonin enhanced SIRT1 signaling, which was accompanied with the increased expression of anti-apoptotic protein Bcl2, and decreased the expression of Ac-FoxO1, Ac-p53, Ac-NF-ΚB, and Bax. Taken together, our findings indicated that melatonin facilitated AD-MSCs-based therapy in MI, possibly through promoting survival of AD-MSCs via SIRT1 signaling. Our data support the promise of melatonin as a novel strategy to improve MSC-based therapy for IHD, possibly through SIRT1 signaling evocation.

Stem cells as cellular vehicles for gene therapy against glioblastoma

Glioblastoma (GBM) is the most common and deadliest primary tumor in adults, with current treatments having limited specific and efficient delivery of therapeutic drugs to tumor sites or cells. Therefore, the development of alternative treatment options is urgently needed. Stem cells are considered as ideal cellular vehicles for gene therapy against glioblastoma. In this paper, we reviewed the recent studies investigating the use of different types of stem cells as cellular vehicles and the gene of interests against the glioblastoma, as well as the future directions of the application of cellular vehicles mediated therapy for glioblastoma.

Activation of liver X receptor improves viability of adipose-derived mesenchymal stem cells to attenuate myocardial ischemia injury through TLR4/NF-κB and Keap-1/Nrf-2 signaling pathways

AIMS

Clinical application of cellular therapy for cardiac regeneration is significantly hampered by the low retention of engrafted cells, mainly attributable to the poor microenvironment dominated by inflammation and oxidative stress in the host's infarcted myocardium. This study aims at investigating whether liver X receptor (LXR) agonist T0901317 will improve survival of adipose-derived mesenchymal stem cells (AD-MSCs) after transplantation into infarcted hearts.

RESULTS

Noninvasive in vivo bioluminescence imaging and histological staining showed that LXR agonist T0901317 improved the retention and survival of intramyocardially injected AD-MSCs. Moreover, combined therapy of LXR agonist and AD-MSCs inhibited host cardiomyocyte apoptosis, reduced fibrosis, and improved cardiac function, while it concomitantly decreased inflammatory cytokines (e.g., tumor necrosis factor-α and interleukin-6) and increased growth factor (e.g., vascular endothelial growth factor and basic fibroblast growth factor) expression in infarct myocardium. To reveal possible mechanisms, AD-MSCs were subjected to hypoxia/serum deprivation (H/SD) injury to simulate ischemic conditions in vivo. The LXR agonist (10(-7) mM) improved AD-MSC survival under H/SD condition. Western blot revealed that the LXR agonist reduced TLR4, TRAF-6, and MyD88 protein expression, inhibited IκBα phosphorylation and NF-κB-p65 nuclear translocation, which resulted in accelerated Keap-1 protein degradation, enhanced Nrf-2 nuclear translocation, and increased HO-1 protein expression.

INNOVATION AND CONCLUSION

LXR agonist can enhance the functional survival of transplanted AD-MSCs in infarcted myocardium, at least partially, via modulation of the TLR4/NF-κB and Keap-1/Nrf-2 signaling pathways. Moreover, combined therapy of LXR agonist and AD-MSCs has a synergetic effect on cardiac repair and functional improvement after infarction.

Ultrastructural features of ischemic tissue following application of a bio-membrane based progenitor cardiomyocyte patch for myocardial infarction repair

Background and Objective

Implantation of cell-sheets into damaged regions of the heart after myocardial infarction (MI) has been shown to improve heart function. However, the tissue morphology following application of induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CM) has not been studied in detail at the level afforded by electron microscopy. We hypothesized that increasing the number of CM derived from iPSC would increase the effectiveness of cell-sheets used to treat ischemic cardiomyopathy. We report here on the ultrastructural features after application of a bio-membrane ‘cell patch’.

Methods

iPSC-derived progenitor cells were transduced using lentivirus vectors with or without NCX1 promoter. iPSC-CM sheets were transplanted over the transmural MI region in a mouse model of regional ischemic cardiomyopathy. Mice were divided into four groups, 1) Sham; 2) MI; 3) MI + iPSC without NCX1 treated cells (MI + iPSC^Null) and 4) MI + iPSC receiving NCX1 promoter treated cells (MI + iPSC^NCX1). Echocardiography was performed 4 weeks after cell patch application, followed by histological and transmission electron microscopy (TEM) analysis.

Results

Large numbers of transplanted CM were observed with significant improvements in left ventricular performance and remodeling in group 4 as compared with group 3. No teratoma formation was detected in any of the treatment groups.

Conclusion

Manipulation of iPSC yields large numbers of iPSC-CM and favorable morphological and ultrastructural tissue changes. These changes have the potential to enhance current methods used for restoration of cardiac function after MI.

Effect of stem cell application on Asherman syndrome, an experimental rat model

PURPOSE

We evaluate the effect of stem cells to induce endometrial proliferation and angiogenesis on Asherman Syndrome (AS).

METHODS

The experimental study was performed in stemcell research laboratory. Forty Wistar-Albino rats were divided according to groups. In group1 (n = 10) to establish the model; trichloroacetic acid was injected to right uterine horn. Two weeks later, intrauterine synechia was confirmed. In group2 (n = 10), 2 weeks later, 2 × 106 mesenchymal stem cells (MSC) were injected into right uterine horn followed by three intraperitoneal injections of MSCs. In group3 (n = 10), daily oral estrogen was initiated on the second week. In group4 (n = 10), MSC injections and oral estrogen was given together. The amount of fibrosis, vascularisation, inflammation and immunohistochemical staining with vascular endothelial growth factor (VEGF), proliferating cell nuclear antigen (PCNA) and Ki-67 were evaluated in the uterine tissues.

RESULTS

In all treatment groups; fibrosis decreased but vascularisation and immunhistohemical stainings increased in the experimental side. The amount of fibrosis, vascularisation, Ki-67 and PCNA scores were similar between group2 and 3. In group4, comparing to group2, less fibrosis but more Ki-67, PCNA and VEGF staining was observed.

CONCLUSION

Stem cells, when added to estrogen, are a highly effective alternative to induce regeneration of endometrium in Asherman Syndrome therapy.

Novel insights into the mechanism of cell-based therapy after chronic myocardial infarction

Cell transplantation therapy is considered a novel and promising strategy in regenerative medicine. Recent studies point out that paracrine effects and inflammation induced by transplanted cells are key factors for the improvement of myocardial function. The present study aims at differentiating paracrine effects from inflammatory reactions after cell transplantation. Therefore, in vitro induced apoptotic bodies were transplanted after myocardial infarction in a rat model. Eight weeks after transplantation, the functional results showed no improvement in left ventricular function. Histological analysis revealed no significant differences in the amount of infiltrated cells and collagen content did not differ among the four groups, which sustains the functional data. Surprisingly, angiogenesis increased in groups with apoptotic bodies derived from HUVEC and endothelial progenitor cells, but not from fibroblasts. A complex genetic analysis of apoptotic bodies indicated that miRNAs could be responsible for these changes. Our study demonstrates that inflammatory reaction is critical for scar remodelling and improvement of the heart function after late cell therapy, while neoangiogenesis alone is not sufficient to improve heart function.

Exercise is the real polypill

The concept of a "polypill" is receiving growing attention to prevent cardiovascular disease. Yet similar if not overall higher benefits are achievable with regular exercise, a drug-free intervention for which our genome has been haped over evolution. Compared with drugs, exercise is available at low cost and relatively free of adverse effects. We summarize epidemiological evidence on the preventive/therapeutic benefits of exercise and on the main biological mediators involved.

Enhanced stem cell migration mediated by VCAM-1/VLA-4 interaction improves cardiac function in virus-induced dilated cardiomyopathy

Endogenous circulation of bone marrow-derived cells (BMCs) was observed in patients with dilated cardiomyopathy (DCM) who showed cardiac upregulation of Vascular Cell Adhesion Protein-1 (VCAM-1). However, the underlying pathophysiology is currently unknown. Thus, we aimed to analyze circulation, migration and G-CSF-based mobilization of BMCs in a murine model of virus-induced DCM. Mice with coxsackievirus B3 (CVB3) induced DCM and healthy controls were analyzed regarding their myocardial homing factors by PCR. To determine cardiac VCAM-1 expression ELISA and immunohistochemistry were applied. Flow cytometry was performed to analyze BMCs. Cardiac diameters and function were evaluated by echocardiography before and 4 weeks after G-CSF treatment. In murine CVB3-induced DCM an increase of BMCs in peripheral blood and a decrease of BMCs in bone marrow was observed. We found an enhanced migration of Very Late Antigen-4 (VLA-4⁺) BMCs to the diseased heart overexpressing VCAM-1 and higher numbers of CD45⁻CD34⁻Sca-1⁺ and CD45⁻CD34⁻c-kit⁺ cells. Mobilization of BMCs by G-CSF boosted migration along the VCAM-1/VLA-4 axis and reduced apoptosis of cardiomyocytes. Significant improvement of cardiac function was detected by echocardiography in G-CSF-treated mice. Blocking VCAM-1 by a neutralizing antibody reduced the G-CSF-dependent effects on stem cell migration and cardiac function. This is the first study showing that in virus-induced DCM VCAM-1/VLA-4 interaction is crucial for recruitment of circulating BMCs leading to beneficial anti-apoptotic effects resulting in improved cardiac function after G-CSF-induced mobilization.

Adaptive inflammatory microenvironment for cell-based regeneration in ischemic cardiovascular disease

Cell-based therapy has emerged to be a promising strategy for alleviating the heavy burden of ischemic cardiovascular disease for nearly two decades, despite a variety of pending questions about its availability and efficacy. One question is whether and how the cells behave for regeneration in vivo, which could be limited or potentiated by the inflammatory microenvironment following myocardial infarction or critical limb ischemia. To this end, we hypothesize that the "adaptive inflammatory microenvironment" is pertinent to the cell-based regeneration, and make a brief comment on it based upon recent evidence.

Restored perfusion and reduced inflammation in the infarcted heart after grafting stem cells with a hyaluronan-based scaffold

The aim of this study is to investigate the blood perfusion and the inflammatory response of the myocardial infarct area after transplanting a hyaluronan-based scaffold (HYAFF(®) 11) with bone marrow mesenchymal stem cells (MSCs). Nine-week-old female pigs were subjected to a permanent left anterior descending coronary artery ligation for 4 weeks. According to the kind of the graft, the swine subjected to myocardial infarction were divided into the HYAFF(®) 11, MSCs, HYAFF(®) 11/MSCs and untreated groups. The animals were killed 8 weeks after coronary ligation. Scar perfusion, evaluated by Contrast Enhanced Ultrasound echography, was doubled in the HYAFF(®) 11/MSCs group and was comparable with the perfusion of the healthy, non-infarcted hearts. The inflammation score of the MSCs and HYAFF(®) 11/MSCs groups was near null, revealing the role of the grafted MSCs in attenuating the cell infiltration, but not the foreign reaction strictly localized around the fibres of the scaffold. Apart from the inflammatory response, the native tissue positively interacted with the HYAFF(®) 11/MSCs construct modifying the extracellular matrix with a reduced presence of collagene and increased amount of proteoglycans. The border-zone cardiomyocytes also reacted favourably to the graft as a lower degree of cellular damage was found. This study demonstrates that the transplantation in the myocardial infarct area of autologous MSCs supported by a hyaluronan-based scaffold restores blood perfusion and almost completely abolishes the inflammatory process following an infarction. These beneficial effects are superior to those obtained after grafting only the scaffold or MSCs, suggesting that a synergic action was achieved using the cell-integrated polymer construct.

Doxorubicin induces senescence and impairs function of human cardiac progenitor cells

The increasing population of cancer survivors faces considerable morbidity and mortality due to late effects of the antineoplastic therapy. Cardiotoxicity is a major limiting factor of therapy with doxorubicin (DOXO), the most effective anthracycline, and is characterized by a dilated cardiomyopathy that can develop even years after treatment. Studies in animals have proposed the cardiac progenitor cells (CPCs) as the cellular target responsible for DOXO-induced cardiomyopathy but the relevance of these observations to clinical settings is unknown. In this study, the analysis of the DOXO-induced cardiomyopathic human hearts showed that the majority of human CPCs (hCPCs) was senescent. In isolated hCPCs, DOXO triggered DNA damage response leading to apoptosis early after exposure, and telomere shortening and senescence at later time interval. Functional properties of hCPCs, such as migration and differentiation, were also negatively affected. Importantly, the differentiated progeny of DOXO-treated hCPCs prematurely expressed the senescence marker p16(INK4a). In conclusion, DOXO exposure severely affects the population of hCPCs and permanently impairs their function. Premature senescence of hCPCs and their progeny can be responsible for the decline in the regenerative capacity of the heart and may represent the cellular basis of DOXO-induced cardiomyopathy in humans.

Isolation and characterization of CD276+/HLA-E+ human subendocardial mesenchymal stem cells from chronic heart failure patients: analysis of differentiative potential and immunomodulatory markers expression

Mesenchymal stem cells (MSCs) are virtually present in all postnatal organs as well as in perinatal tissues. MSCs can be differentiated toward several mature cytotypes and interestingly hold potentially relevant immunomodulatory features. Myocardial infarction results in severe tissue damage, cardiomyocyte loss, and eventually heart failure. Cellular cardiomyoplasty represents a promising approach for myocardial repair. Clinical trials using MSCs are underway for a number of heart diseases, even if their outcomes are hampered by low long-term improvements and the possible presence of complications related to cellular therapy administration. Therefore, elucidating the presence and role of MSCs that reside in the post-infarct human heart should provide essential alternatives for therapy. In the current article we show a novel method to reproducibly isolate and culture MSCs from the subendocardial zone of human left ventricle from patients undergoing heart transplant for post-infarct chronic heart failure (HSE-MSCs, human subendocardial mesenchymal stem cells). By using both immunocytochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR), we demonstrated that these cells do express key MSCs markers and do express heart-specific transcription factors in their undifferentiated state, while lacking strictly cardiomyocyte-specific proteins. Moreover, these cells do express immunomodulatory molecules that should disclose their further potential in immune modulation processes in the post-infarct microenvironment. Another novel datum of potentially relevant interest is the expression of cardiac myosin heavy chain at nucclear level in HSE-MSCs. Standard MSCs trilineage differentiation experiments were also performed. The present paper adds new data on the basic biological features of heart-resident MSCs that populate the organ following myocardial infarction. The use of heart-derived MSCs to promote in-organ repair or as a cellular source for cardiomyoplasty is a fascinating and challenging task, which deserves further research efforts.

Cardiac primitive cells become committed to a cardiac fate in adult human heart with chronic ischemic disease but fail to acquire mature phenotype: genetic and phenotypic study

Adult human heart hosts a population of cardiac primitive CD117-positive cells (CPCs), which are responsible for physiological tissue homeostasis and regeneration. While the bona fide stem cells express telomerase, their progenies are no longer able to preserve telomeric DNA; hence the balance between their proliferation and differentiation has to be tightly controlled in order to prevent cellular senescence and apoptosis of CPCs before their maturation can be accomplished. We have examined at cellular and molecular level the proliferation, apoptosis and commitment of CPCs isolated from normal (CPC-N) and age-matched pathological adult human hearts (CPC-P) with ischemic heart disease. In the CPC-P, genes related to early stages of developmental processes, nervous system development and neurogenesis, skeletal development, bone and cartilage development were downregulated, while those involved in mesenchymal cell differentiation and heart development were upregulated, together with the transcriptional activation of TGFβ/BMP signaling pathway. In the pathological heart, asymmetric division was the prevalent type of cardiac stem cell division. The population of CPC-P consisted mainly of progenitors of cardiac cell lineages and less precursors; these cells proliferated more, but were also more susceptible to apoptosis with respect to CPC-N. These results indicate that CPCs fail to reach terminal differentiation and functional competence in pathological conditions. Adverse effects of underlying pathology, which disrupts cardiac tissue structure and composition, and cellular senescence, resulting from cardiac stem cell activation in telomere dysfunctional environment, can be responsible for such outcome.

Stem cell compartmentalization in diabetes and high cardiovascular risk reveals the role of DPP-4 in diabetic stem cell mobilopathy

Bone marrow (BM) derived stem and progenitor cells contribute to cardiovascular homeostasis and are affected by cardiovascular risk factors. We devised a clinical data-driven approach to test candidate stem cell mobilizing mechanisms in pre-clinical models. We found that PB and BM CD34+ cell counts were directly correlated, and that most circulating CD34+ cells were viable, non-proliferating and derived from the BM. Thus, we analyzed PB and BM CD34+ cell levels as a two-compartment model in 72 patients with or without cardiovascular disease. Self-organizing maps showed that disturbed compartmentalization of CD34+ cells was associated with aging and cardiovascular risk factors especially diabetes. High activity of DPP-4, a regulator of the mobilizing chemokine SDF-1α, was associated with altered stem cell compartmentalization. For validation of these findings, we assessed the role of DPP-4 in the BM mobilization response of diabetic rats. Diabetes differentially affected DPP-4 activity in PB and BM and impaired stem/progenitor cell mobilization after ischemia or G-CSF administration. DPP-4 activity in the BM was required for the mobilizing effect of G-CSF, while in PB it blunted ischemia-induced mobilization. Indeed, DPP-4 deficiency restored ischemia (but not G-CSF)-induced stem cell mobilization and improved vascular recovery in diabetic animals. In conclusion, the analysis of stem cell compartmentalization in humans led us to discover mechanisms of BM unresponsiveness in diabetes determined by tissue-specific DPP-4 dysregulation.

Cardiac progenitors derived from reprogrammed mesenchymal stem cells contribute to angiomyogenic repair of the infarcted heart

The strategy to reprogram somatic stem cells to pluripotency status has provided an alternative source of surrogate ES cells (ESC). We report efficient reprogramming of multipotent bone marrow (BM) mesenchymal stem cells (MSC) to pluripotent status and the resultant MSC derived iPS cells (MiPS) and their derived progenitors effectively repaired the infarcted heart. MSC from young, male, Oct4-GFP transgenic mice were reprogrammed by retroviral transduction with Oct4, Sox2, Klf4, and c-Myc stemness factors. MiPS thus generated displayed characteristics of mouse ESC including morphology, surface antigens, gene and miR expression profiles. MiPS also formed spontaneously beating cardiac progenitors which expressed cardiac specific transcription factors and protein markers including Gata4, Mef2c, Nkx2.5, myosin heavy chain, troponin-I, and troponin-T, and showed ultra structural characteristics typical of cardiomyocytes. Intramyocardial delivery of MiPS (group-2) and their derivative cardiac-like cells (MiPS-CP; group-3) in a mouse model of acute myocardial infarction showed extensive survival and engraftment at 4 weeks with resultant attenuation of infarct size (p < 0.001 vs. DMEM injected control; n = 4). Engraftment of MiPS-CP was without cardiac tumorigenesis as compared to 21 % in MiPS transplanted animals. Furthermore, angiogenesis was improved in groups-2 and 3 (p < 0.001 vs. control). Transthoracic echocardiography revealed significantly preserved indices of cardiac contractility (ejection fraction p < 0.001 and fractional shortening p < 0.001 vs. control; n = 7). MSC were successfully reprogrammed into MiPS that displayed ESC-like characteristics and differentiated into spontaneously beating cardiomyocytes. Cardiac progenitors derived from MiPS repopulated the infarcted heart without tumorigenesis and improved global cardiac function.

'Shovel-Ready' applications of stem cell advances for pediatric heart disease

PURPOSE OF REVIEW

The past decade has seen remarkable advances in the field of stem cell biology. Many new technologies and applications are passing the translational phase and likely will soon be relevant for the clinical pediatric cardiologist.

RECENT FINDINGS

This review will focus on two advances in basic science that are now translating into clinical trials. The first advance is the recognition, characterization, and recent therapeutic application of resident cardiac progenitor cells (CPCs). Early results of adult trials and scattered case reports in pediatric patients support expanding CPC-based trials for end-stage heart failure in pediatric patients. The relative abundance of CPCs in the neonate and young child offers greater potential benefits in heart failure treatment than has been realized to date. The second advance is the technology of induced pluripotent stem cells (iPSCs), which reprograms differentiated somatic cells to an undifferentiated embryonic-like state. When iPSCs are differentiated into cardiomyocytes, they model a patient's specific disease, test pharmaceuticals, and potentially provide an autologous source for cell-based therapy.

SUMMARY

The therapeutic recruitment and/or replacement of CPCs has potential for enhancing cardiac repair and regeneration in children with heart failure. Use of iPSCs to model heart disease holds great potential to gain new insights into diagnosis, pathophysiology, and disease-specific management for genetic-based cardiovascular diseases that are prevalent in pediatric patients.

Secretome of apoptotic peripheral blood cells (APOSEC) attenuates microvascular obstruction in a porcine closed chest reperfused acute myocardial infarction model: role of platelet aggregation and vasodilation

Although epicardial blood flow can be restored by an early intervention in most cases, a lack of adequate reperfusion at the microvascular level is often a limiting prognostic factor of acute myocardial infarction (AMI). Our group has recently found that paracrine factors secreted from apoptotic peripheral blood mononuclear cells (APOSEC) attenuate the extent of myocardial injury. The aim of this study was to determine the influence of APOSEC on microvascular obstruction (MVO) in a porcine AMI model. A single dose of APOSEC was intravenously injected in a closed chest reperfused infarction model. MVO was determined by magnetic resonance imaging and cardiac catheterization. Role of platelet function and vasodilation were monitored by means of ELISA, flow cytometry, aggregometry, western blot and myographic experiments in vitro and in vivo. Treatment of AMI with APOSEC resulted in a significant reduction of MVO. Platelet activation markers were reduced in plasma samples obtained during AMI, suggesting an anti-aggregatory capacity of APOSEC. This finding was confirmed by in vitro tests showing that activation and aggregation of both porcine and human platelets were significantly impaired by co-incubation with APOSEC, paralleled by vasodilator-stimulated phosphoprotein (VASP)-mediated inhibition of platelets. In addition, APOSEC evidenced a significant vasodilatory capacity on coronary arteries via p-eNOS and iNOS activation. Our data give first evidence that APOSEC reduces the extent of MVO during AMI, and suggest that modulation of platelet activation and vasodilation in the initial phase after myocardial infarction contributes to the improved long-term outcome in APOSEC treated animals.

Mesenchymal stem cells neither fully acquire the electrophysiological properties of mature cardiomyocytes nor promote ventricular arrhythmias in infarcted rats

Electrophysiological properties of implanted mesenchymal stem cells (MSCs) in infarcted hearts remain unclear, and their proarrhythmic effect is still controversial. The intent of this study was to investigate electrophysiological properties and proarrhythmic effects of MSCs in infarcted hearts. Rats were randomly divided into a myocardial infarction (MI) group, a MI-DMEM group (received DMEM medium injection) and MI-MSCs group (received MSCs injection). Survival analysis showed that the majority of engrafted MSCs died at day 9 after transplantation. Engrafted MSCs expressed cardiac markers (MYH, cTnI, Cx43), cardiac ion channel genes (Kv1.4, Kv4.2 and Kir2.1) and potassium currents (I (to), I (K1) and I (KDR)), but did not express Nav1.5, Cav1.2, Na(+) current and Ca(2+) current during their survival. When induced by Ca(2+), implanted MSCs exhibited no contraction ability after being isolated from the heart. Following 8-week electrocardiography monitoring, the cumulative occurrence of ventricular arrhythmias (VAs) was not different among the three groups. However, the prolonged QRS duration in infarcted rats without VAs was significantly decreased in the MI-MSCs group compared with the other two groups. The inducibility of VAs in the MI-MSCs group was much lower than that in the MI and MI-DMEM groups (41.20 vs. 86.67 % and 92.86 %; P < 0.0125). The ventricular effective refractory period in MI-MSCs group was prolonged in comparison with that in the MI and MI-DMEM groups (56.0 ± 8.8 vs. 47.7 ± 8.8 ms and 45.7 ± 6.2 ms; P < 0.01). These results demonstrate that MSCs do not acquire the electrophysiological properties of mature cardiomyocytes during the survival period in the infarcted hearts. However, they can alleviate the electrical vulnerability and do not promote ventricular arrhythmias.

Live monitoring of small vessels during development and disease using the flt-1 promoter element

Vessel formation is of critical importance for organ function in the normal and diseased state. In particular, the labeling and quantitation of small vessels prove to be technically challenging using current approaches. We have, therefore, established a transgenic embryonic stem (ES) cell line and a transgenic mouse model where the vascular endothelial growth factor receptor VEGFR-1 (flt-1) promoter drives the expression of the live reporter eGFP. Fluorescence microscopy and immunostainings revealed endothelial-specific eGFP labeling of vascular networks. The expression pattern recapitulates that of the endogenous flt-1 gene, because small and large vessels are labeled by eGFP during embryonic development; after birth, the expression becomes more restricted to small vessels. We have explored this in the cardiovascular system more in detail and found that all small vessels and capillaries within the heart are strongly eGFP+. In addition, myocardial injuries have been induced in transgenic mice and prominent vascular remodeling, and an increase in endothelial cell area within the peri-infarct area could be observed underscoring the utility of this mouse model. Thus, the transgenic flt-1/eGFP models are powerful tools to investigate and quantify vascularization in vivo and to probe the effect of different compounds on vessel formation in vitro.

S100A8/A9 aggravates post-ischemic heart failure through activation of RAGE-dependent NF-κB signaling

The extracellular heterodimeric protein S100A8/A9 activates the innate immune system through activation of the receptor of advanced glycation end products (RAGE) and Toll-like receptors. As activation of RAGE has recently been associated with sustained myocardial inflammation and heart failure (HF) we studied the role of S100A8/A9 in the development of post-ischemic HF. Hypoxia led to sustained induction of S100A8/A9 accompanied by increased nuclear factor (NF-)κB binding activity and increased expression of pro-inflammatory cytokines in cardiac fibroblasts and macrophages. Knockdown of either S100A8/A9 or RAGE rescued the induction of pro-inflammatory cytokines and NF-κB activation after hypoxia. In a murine model of post-ischemic HF both cardiac RNA and protein levels of S100A8/A9 were elevated as soon as 30 min after hypoxia with sustained activation up to 28 days after ischemic injury. Treatment with recombinant S100A8/A9 resulted in reduced cardiac performance following ischemia/reperfusion. Chimera experiments after bone marrow transplantation demonstrated the importance of RAGE expression on immune cells for their recruitment to the injured myocardium aggravating post-ischemic heart failure. Signaling studies in isolated ventricles indicated that MAP kinases JNK, ERK1/2 as well as NF-κB mediate signals downstream of S100A8/A9-RAGE in post-ischemic heart failure. Interestingly, cardiac performance was not affected by administration of S100A8/A9 in RAGE(-/-)-mice, which demonstrated significantly improved cardiac recovery compared to WT-mice. Our study provides evidence that sustained activation of S100A8/A9 critically contributes to the development of post-ischemic HF driving the progressive course of HF through activation of RAGE.

Secretome of apoptotic peripheral blood cells (APOSEC) confers cytoprotection to cardiomyocytes and inhibits tissue remodelling after acute myocardial infarction: a preclinical study

Heart failure following acute myocardial infarction (AMI) is a major cause of morbidity and mortality. Our previous observation that injection of apoptotic peripheral blood mononuclear cell (PBMC) suspensions was able to restore long-term cardiac function in a rat AMI model prompted us to study the effect of soluble factors derived from apoptotic PBMC on ventricular remodelling after AMI. Cell culture supernatants derived from irradiated apoptotic peripheral blood mononuclear cells (APOSEC) were collected and injected as a single dose intravenously after myocardial infarction in an experimental AMI rat model and in a porcine closed chest reperfused AMI model. Magnetic resonance imaging (MRI) and echocardiography were used to quantitate cardiac function. Analysis of soluble factors present in APOSEC was performed by enzyme-linked immunosorbent assay (ELISA) and activation of signalling cascades in human cardiomyocytes by APOSEC in vitro was studied by immunoblot analysis. Intravenous administration of a single dose of APOSEC resulted in a reduction of scar tissue formation in both AMI models. In the porcine reperfused AMI model, APOSEC led to higher values of ejection fraction (57.0 vs. 40.5%, p < 0.01), a better cardiac output (4.0 vs. 2.4 l/min, p < 0.001) and a reduced extent of infarction size (12.6 vs. 6.9%, p < 0.02) as determined by MRI. Exposure of primary human cardiac myocytes with APOSEC in vitro triggered the activation of pro-survival signalling-cascades (AKT, Erk1/2, CREB, c-Jun), increased anti-apoptotic gene products (Bcl-2, BAG1) and protected them from starvation-induced cell death. Intravenous infusion of culture supernatant of apoptotic PBMC attenuates myocardial remodelling in experimental AMI models. This effect is probably due to the activation of pro-survival signalling cascades in the affected cardiomyocytes.

Identification of telocytes in skeletal muscle interstitium: implication for muscle regeneration

Skeletal muscle interstitium is crucial for regulation of blood flow, passage of substances from capillaries to myocytes and muscle regeneration. We show here, probably, for the first time, the presence of telocytes (TCs), a peculiar type of interstitial (stromal) cells, in rat, mouse and human skeletal muscle. TC features include (as already described in other tissues) a small cell body and very long and thin cell prolongations-telopodes (Tps) with moniliform appearance, dichotomous branching and 3D-network distribution. Transmission electron microscopy (TEM) revealed close vicinity of Tps with nerve endings, capillaries, satellite cells and myocytes, suggesting a TC role in intercellular signalling (via shed vesicles or exosomes). In situ immunolabelling showed that skeletal muscle TCs express c-kit, caveolin-1 and secrete VEGF. The same phenotypic profile was demonstrated in cell cultures. These markers and TEM data differentiate TCs from both satellite cells (e.g. TCs are Pax7 negative) and fibroblasts (which are c-kit negative). We also described non-satellite (resident) progenitor cell niche. In culture, TCs (but not satellite cells) emerge from muscle explants and form networks suggesting a key role in muscle regeneration and repair, at least after trauma.

Mesenchymal stromal cells mediate a switch to alternatively activated monocytes/macrophages after acute myocardial infarction

Given the established anti-inflammatory properties of mesenchymal stromal cells (MSCs), we investigated their effect on inflammatory cell infiltration of ischemic cardiac tissue and cardiac function. We employed two types of MSCs, human bone marrow-derived (BM) MSCs and human umbilical cord perivascular cells in an experimental acute myocardial infarction (MI) model with the immune-deficient NOD/SCID gamma null mouse. Cells were infused 48 h after induction of MI and mice assessed 24 h later (72 h after MI) for bone marrow (BM), circulating and cardiac tissue-infiltrating monocytes/macrophages. We showed that in the presence of either MSC type, overall macrophage/monocyte levels were reduced, including pro-inflammatory M1-type macrophages, while the proportion of alternatively activated M2-type macrophages was significantly increased in the circulation and heart but not the BM. Moreover, we found decreased expression of IL-1β and IL-6, increased IL-10 expression and fewer apoptotic cardiomyocytes without changes in angiogenesis in the infarct area. Fractional shortening was enhanced 2 weeks after cell infusion but was similar to medium controls 16 weeks after MI. In vitro studies showed that BM MSCs increased the frequency of alternatively activated monocytes/macrophages, in part by MSC-mediated secretion of IL-10. Our data suggest a new mechanism for MSC-mediated enhancement of cardiac function, possibly via an IL-10 mediated switch from infiltration of pro-inflammatory to anti-inflammatory macrophages at the infarct site. Additional studies are warranted confirming the role of IL-10 and augmenting the anti-inflammatory effects of MSCs in cardiac regeneration.

Interferon-gamma induced adipose tissue inflammation is linked to endothelial dysfunction in type 2 diabetic mice

Interferon-gamma (IFNγ) has previously been associated with immuno-mediated inflammation in diet-induced obesity and type 1 diabetes. This study sought to define the role of IFNγ-induced adipose tissue inflammation in endothelial dysfunction in type 2 diabetes. We examined mesenteric adipose tissue (MAT) inflammation, and endothelial function of small mesenteric artery (SMA) in control mice (m Lepr(db)), diabetic mice (Lepr(db)), m Lepr(db) treated with IFNγ, and Lepr(db) treated with anti-IFNγ or anti-monocyte chemoattractant protein-1 (anti-MCP-1). mRNA and protein expression of IFNγ and MCP-1 were increased in MAT of Lepr(db), accompanied by increased T-lymphocyte and macrophage infiltration. Anti-IFNγ reduced MAT inflammatory cell infiltration and inflammatory cytokine expression in Lepr(db), while IFNγ treatment showed the opposite effects in m Lepr(db). Acetylcholine (ACh)-induced vasorelaxation of SMA was impaired in Lepr(db) versus m Lepr(db), but sodium nitroprusside (SNP)-induced vasorelaxation was comparable. Both anti-IFNγ and anti-MCP-1 improved endothelial function of Lepr(db), while IFNγ treatment impaired endothelial function of m Lepr(db). Superoxide production was higher in both MAT and SMA of Lepr(db) mice, and anti-IFNγ reduced MAT and SMA superoxide production. Macrophage accumulation in the adventitia of SMA, and mRNA expression of MCP-1 in SMA were increased in Lepr(db) and IFNγ-treated m Lepr(db), but reduced in anti-IFNγ treated Lepr(db). These findings suggest IFNγ has a key role in the regulation of visceral adipose tissue inflammatory response and endothelial dysfunction in type 2 diabetes.

Perfusion defect size predicts engraftment but not early retention of intra-myocardially injected cardiosphere-derived cells after acute myocardial infarction

Therapeutic cell retention and engraftment are critical for myocardial regeneration. Underlying mechanisms, including the role of tissue perfusion, are not well understood. In Wistar Kyoto rats, syngeneic cardiosphere-derived cells (CDCs) were injected intramyocardially, after experimental myocardial infarction. CDCs were labeled with [¹⁸F]-FDG (n = 7), for quantification of 1-h retention, or with sodium-iodide-symporter gene (NIS; n = 8), for detection of 24-h engraftment by reporter imaging. Perfusion was imaged simultaneously. Infarct size was 37 ± 9 and 38 ± 9% of LV in FDG and NIS groups. Cell signal was located in the infarct border zone in all animals. No significant relationship was observed between infarct size and 1-h CDC retention (r = −0.65; P = 0.11). However, infarct size correlated significantly with 24-h engraftment (r = 0.75; P = 0.03). Residual perfusion at the injection site was not related to cell retention/engraftment. Larger infarcts are associated with improved CDC engraftment. This observation encourages further investigation of microenvironmental conditions after ischemic damage and their role in therapeutic cell survival.