Post-myocardial infarct inflammation and the potential role of cell therapy

Novel fabrication of bioengineered injectable chitosan hydrogel loaded with conductive nanoparticles to improve therapeutic potential of mesenchymal stem cells in functional recovery after ischemic myocardial infarction

In recent decades, myocardial regeneration through stem cell transplantation and tissue engineering has been viewed as a promising technique for treating myocardial infarction. As a result, the researcher attempts to see whether co-culturing modified mesenchymal stem cells with Au@Ch-SF macro-hydrogel and H9C2 may help with tissue regeneration and cardiac function recovery. The gold nanoparticles (Au) incorporated into the chitosan-silk fibroin hydrogel (Au@Ch-SF) were validated using spectral and microscopic examinations. The most essential elements of hydrogel groups were investigated in detail, including weight loss, mechanical strength, and drug release rate. Initially, the cardioblast cells (H9C2 cells) was incubated with Au@Ch-SF macro-hydrogel, followed by mesenchymal stem cells (2 × 10⁵) were transplanted into the Au@Ch-SF macro-hydrogel+H9C2 culture at the ratio of 2:1. Further, cardiac phenotype development, cytokines expression and tissue regenerative performance of modified mesenchymal stem cells treatment were studied through various in vitro and in vivo analyses. The Au@Ch-SF macro-hydrogel gelation time was much faster than that of Ch and Ch-SF hydrogels, showing that Ch and SF exhibited greater intermolecular interactions. The obtained Au@Ch-SF macro-hydrogel has no toxicity on mesenchymal stem cells (MS) or cardiac myoblast (H9C2) cells, according to the biocompatibility investigation. MS cells co-cultured with Au@Ch-SF macro-hydrogel and H9C2 cells also stimulated cardiomyocyte fiber restoration, which has been confirmed in myocardial infarction rats using -MHC and Cx43 myocardial indicators. We developed a novel method of co-cultured therapy using MS cells, Au@Ch-SF macro-hydrogel, and H9C2 cells which could promote the regenerative activities in myocardial ischemia cells. These study findings show that co-cultured MS therapy might be effective for the treatment of myocardial injury.

Intrapericardial Administration of Secretomes from Menstrual Blood-Derived Mesenchymal Stromal Cells: Effects on Immune-Related Genes in a Porcine Model of Myocardial Infarction

Acute myocardial infarction (AMI) is a manifestation of ischemic heart disease where the immune system plays an important role in the re-establishment of homeostasis. We hypothesize that the anti-inflammatory activity of secretomes from menstrual blood-derived mesenchymal stromal cells (S-MenSCs) and IFNγ/TNFα-primed MenSCs (S-MenSCs*) may be considered a therapeutic option for the treatment of AMI. To assess this hypothesis, we have evaluated the effect of S-MenSCs and S-MenSCs* on cardiac function parameters and the involvement of immune-related genes using a porcine model of AMI. Twelve pigs were randomly divided into three biogroups: AMI/Placebo, AMI/S-MenSCs, and AMI/S-MenSCs*. AMI models were generated using a closed chest coronary occlusion-reperfusion procedure and, after 72 h, the different treatments were intrapericardially administered. Cardiac function parameters were monitored by magnetic resonance imaging before and 7 days post-therapy. Transcriptomic analyses in the infarcted tissue identified 571 transcripts associated with the Gene Ontology term Immune response, of which 57 were differentially expressed when different biogroups were compared. Moreover, a prediction of the interactions between differentially expressed genes (DEGs) and miRNAs from secretomes revealed that some DEGs in the infarction area, such as STAT3, IGFR1, or BCL6 could be targeted by previously identified miRNAs in secretomes from MenSCs. In conclusion, the intrapericardial administration of secretome early after infarction has a significant impact on the expression of immune-related genes in the infarcted myocardium. This confirms the immunomodulatory potential of intrapericardially delivered secretomes and opens new therapeutic perspectives in myocardial infarction treatment.

Cardiovascular tissue engineering and regeneration: A plead for further knowledge convergence

Cardiovascular tissue engineering and regeneration strive to provide long-term, effective solutions for a growing group of patients in need of myocardial repair, vascular (access) grafts, heart valves, and regeneration of organ microcirculation. In the past two decades, ongoing convergence of disciplines and multidisciplinary collaborations between cardiothoracic surgeons, cardiologists, bioengineers, material scientists, and cell biologists have resulted in better understanding of the problems at hand and novel regenerative approaches. As a side effect, however, the field has become strongly organized and differentiated around topical areas at risk of reinvention of technologies and repetition of approaches and across the areas. A better integration of knowledge and technologies from the individual topical areas and regenerative approaches and technologies may pave the way towards faster and more effective treatments to cure the cardiovascular system. This review summarizes the evolution of research and regenerative approaches in the areas of myocardial regeneration, heart valve and vascular tissue engineering, and regeneration of microcirculations and discusses previous and potential future integration of these individual areas and developed technologies for improved clinical impact. Finally, it provides a perspective on the further integration of research organization, knowledge implementation, and valorization as a contributor to advancing cardiovascular tissue engineering and regenerative medicine.

Cardiac protection by pirfenidone after myocardial infarction: a bioinformatic analysis

Left ventricular (LV) remodeling after myocardial infarction (MI) is promoted by an intense fibrotic response, which could be targeted by the anti-fibrotic drug pirfenidone. We explored the relationship between protein modulation by pirfenidone and post-MI remodeling, based on molecular information and transcriptomic data from a swine model of MI. We identified 6 causative motives of post-MI remodeling (cardiomyocyte cell death, impaired myocyte contractility, extracellular matrix remodeling and fibrosis, hypertrophy, renin–angiotensin–aldosterone system activation, and inflammation), 4 pirfenidone targets and 21 bioflags (indirect effectors). Pirfenidone had a more widespread action than gold-standard drugs, encompassing all 6 motives, with prominent effects on p38γ-MAPK12, the TGFβ1-SMAD2/3 pathway and other effector proteins such as matrix metalloproteases 2 and 14, PDGFA/B, and IGF1. A bioinformatic approach allowed to identify several possible mechanisms of action of pirfenidone with beneficial effects in the post-MI LV remodeling, and suggests additional effects over guideline-recommended therapies.

Engineering Microsphere-Loaded Non-mulberry Silk-Based 3D Bioprinted Vascularized Cardiac Patches with Oxygen-Releasing and Immunomodulatory Potential

A hostile myocardial microenvironment post ischemic injury (myocardial infarction) plays a decisive role in determining the fate of tissue-engineered approaches. Therefore, engineering hybrid 3D printed platforms that can modulate the MI microenvironment for improving implant acceptance has surfaced as a critical requirement for reconstructing an infarcted heart. Here, we have employed a non-mulberry silk-based conductive bioink comprising carbon nanotubes (CNTs) to bioprint functional 3D vascularized anisotropic cardiac constructs. Immunofluorescence staining, polymerase chain reaction-based gene expression studies, and electrophysiological studies showed that the inclusion of CNTs in the bioink played a significant role in upregulating matured cardiac biomarkers, sarcomere formation, and beating rate while promoting cardiomyocyte viability. These constructs were then microinjected with calcium peroxide and IL-10-loaded gelatin methacryloyl microspheres. Measurements of oxygen concentration revealed that these microspheres upheld the oxygen availability for maintaining cellular viability for at least 5 days in a hypoxic environment. Also, the ability of microinjected IL-10 microspheres to modulate the macrophages to anti-inflammatory M2 phenotype in vitro was uncovered using immunofluorescent staining and gene expression studies. Furthermore, in vivo subcutaneous implantation of microsphere-injected 3D constructs provided insights toward the extended time frame that was achieved for dealing with the hostile microenvironment for promoting host neovascularization and implant acceptance.

Long Noncoding RNAs in Myocardial Ischemia-Reperfusion Injury

Following an acute myocardial infarction, reperfusion therapy is currently the most effective way to save the ischemic myocardium; however, restoring blood flow may lead to a myocardial ischemia-reperfusion injury (MIRI). Recent studies have confirmed that long-chain noncoding RNAs (LncRNAs) play important roles in the pathophysiology of MIRIs. These LncRNA-mediated roles include cardiomyocyte apoptosis, autophagy, necrosis, oxidative stress, inflammation, mitochondrial dysfunction, and calcium overload, which are regulated through the expression of target genes. Thus, LncRNAs may be used as clinical diagnostic markers and therapeutic targets to treat or prevent MIRI. This review evaluates the research on LncRNAs involved in MIRIs and provides new ideas for preventing and treating this type of injury.

The optimization conditions of establishing an H9c2 cardiomyocyte hypoxia/reoxygenation injury model based on an AnaeroPack System

Ischemia-reperfusion (I/R) injury is a major cause of cardiomyocyte apoptosis after vascular recanalization, which was mimicked by a hypoxia/reoxygenation (H/R) injury model of cardiomyocytes in vitro. In this study, we explored an optimal H/R duration procedure using the AnaeroPack System. To study the H/R procedure, cardiomyocytes were exposed to the AnaeroPack System with sugar and serum-free medium, followed by reoxygenation under normal conditions. Cell injury was detected through lactate dehydrogenase (LDH) and cardiac troponin (c-Tn) release, morphological changes, cell apoptosis, and expression of apoptosis-related proteins. The results showed that the damage to H9c2 cells increased with prolonged hypoxia time, as demonstrated by increased apoptosis rate, LDH and c-Tn release, HIF-1α expression, as well as decreased expression of Bcl-2. Furthermore, hypoxia for 10 h and reoxygenation for 6 h exhibited the highest apoptosis rate and damage and cytokine release; in addition, cells were deformed, small, and visibly round. After 12 h of hypoxia, the majority of the cells were dead. Taken together, this study showed that subjecting H9c2 cells to the AnaeroPack System for 10 h and reoxygenation for 6 h can achieve a practicable and repeatable H/R injury model.

Chitosan Hydrogel Enhances the Therapeutic Efficacy of Bone Marrow-Derived Mesenchymal Stem Cells for Myocardial Infarction by Alleviating Vascular Endothelial Cell Pyroptosis

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Myocardial infarction (MI) is one of the higher mortality rates, and current treatment can only delay the progression of the disease. Experiments have shown that cell therapy could improve cardiac function and mesenchymal stem cells (MSCs)-based therapies provide a great promising approach in the treatment of MI. However, low cell survival and engraftment restricts the successful application of MSCs for treating MI. Here, we explored whether co-transplantation of a chitosan (CS) thermosensitive hydrogel with bone marrow-derived MSCs (BMSCs) could optimize and maximize the therapeutic of BMSCs in a mouse model of MI. The fate of transplanted BMSCs was monitored by bioluminescence imaging, and the recovery of cardiac function was detected by echocardiogram. Our results proved that CS hydrogel enhanced the BMSCs' survival and the recovery of cardiac function by protecting the vascular endothelial cells. Further studies revealed that the increased number of vascular endothelial cells was due to the fact that transplanted BMSCs inhibited the inflammatory response and alleviated the pyroptosis of vascular endothelial cells. In conclusions, CS hydrogel improved the engraftment of transplanted BMSCs, ameliorated inflammatory responses, and further promoted functional recovery of heart by alleviating vascular endothelial cell pyroptosis.

Characterization of the Angiogenic Potential of Human Regulatory Macrophages (Mreg) after Ischemia/Reperfusion Injury In Vitro

Ischemia/reperfusion- (I/R-) induced organ damage represents one of the main causes of death worldwide, and new strategies to reduce I/R injury are urgently needed. We have shown that programmable cells of monocytic origin (PCMO) respond to I/R with the release of angiogenic mediators and that transplantation of PCMO results in increased neovascularization. Human regulatory macrophages (Mreg), which are also of monocytic origin, have been successfully employed in clinical transplantation studies due to their immunomodulatory properties. Here, we investigated whether Mreg also possess angiogenic potential in vitro and could represent a treatment option for I/R-associated illnesses. Mreg were differentiated using peripheral blood monocytes from different donors (N = 14) by incubation with M-CSF and human AB serum and stimulation with INF-gamma. Mreg cultures were subjected to 3 h of hypoxia and 24 h of reoxygenation (resembling I/R) or the respective nonischemic control. Cellular resilience, expression of pluripotency markers, secretion of angiogenic proteins, and influence on endothelial tube formation as a surrogate marker for angiogenesis were investigated. Mreg showed resilience against I/R that did not lead to increased cell damage. Mreg express DHRS9 as well as IDO and display a moderate to low expression pattern of several pluripotency genes (e.g., NANOG, OCT-4, and SOX2). I/R resulted in an upregulation of IDO (p < 0.001) while C-MYC and KLF4 were downregulated (p < 0.001 and p < 0.05). Proteome profiling revealed the secretion of numerous angiogenic proteins by Mreg of which several were strongly upregulated by I/R (e.g., MIP-1alpha, 19.9-fold; GM-CSF, 19.2-fold; PTX3, 5.8-fold; IL-1β, 5.2-fold; and MCP-1, 4.7-fold). The angiogenic potential of supernatants from Mreg subjected to I/R remains inconclusive. While Mreg supernatants from 3 donors induced tube formation, 2 supernatants were not effective. We suggest that Mreg may prove beneficial as a cell therapy-based treatment option for I/R-associated illnesses. However, donor characteristics seem to crucially influence the effectiveness of Mreg treatment.

Identification of very early inflammatory markers in a porcine myocardial infarction model

BACKGROUND

Acute myocardial infarction (AMI) is one of the most deleterious conditions leading to cardiovascular diseases and mortality. The importance of an early and accurate diagnosis assures immediate medical treatments, which are fundamental to reduce mortality and improve prognoses. AMI is associated to an inflammatory response which includes the increase of circulating inflammatory cytokines, chemokines and immune cell activation. This study aimed to identify which are the very early immune-related biomarkers that may be used as predictors of myocardial infarction severity. In order to mimic the pathophysiological events involved in human myocardial infarction, a temporary occlusion (90 min) of the mid-left anterior descending coronary artery was performed in a swine animal model.

RESULTS

Lymphocyte subsets analysis in peripheral blood revealed significant alterations in CD4+/CD8+ ratio and naïve and effector/memory T cell percentages at 1 h post-myocardial infarction. Changes in TH1/TH2-related cytokine, monocyte and neutrophil markers gene expression were observed in peripheral blood lymphocytes, as well. Additionally, significant correlations between cardiac parameters (cardiac enzymes, left ventricular ejection fraction and % infarct) and blood-derived parameters (cytokine expression and lymphocyte subset distribution) were found.

CONCLUSIONS

Peripheral blood lymphocyte alterations are easily and swiftly detectable, so they may be good biomarkers for a very early prognosis and to predict myocardial infarction severity.

NAD+ Deficiency Is a Common Central Pathological Factor of a Number of Diseases and Aging: Mechanisms and Therapeutic Implications

Increasing evidence has indicated critical roles of nicotinamide adenine dinucleotide, oxidized form (NAD⁺) in various biological functions. NAD⁺ deficiency has been found in models of a number of diseases such as cerebral ischemia, myocardial ischemia, and diabetes, and in models of aging. Applications of NAD⁺ or other approaches that can restore NAD⁺ levels are highly protective in these models of diseases and aging. NAD⁺ produces its beneficial effects by targeting at multiple pathological pathways, including attenuating mitochondrial alterations, DNA damage, and oxidative stress, by modulating such enzymes as sirtuins, glyceraldehyde-3-phosphate dehydrogenase, and AP endonuclease. These findings have suggested great therapeutic and nutritional potential of NAD⁺ for diseases and senescence. Recent Advances: Approaches that can restore NAD⁺ levels are highly protective in the models of such diseases as glaucoma. The NAD⁺ deficiency in the diseases and aging results from not only poly(ADP-ribose) polymerase-1 (PARP-1) activation but also decreased nicotinamide phosphoribosyltransferase (Nampt) activity and increased CD38 activity. Significant biological effects of extracellular NAD⁺ have been found. Increasing evidence has suggested that NAD⁺ deficiency is a common central pathological factor in a number of diseases and aging. Critical Issues and Future Directions: Future studies are required for solidly establishing the concept that "NAD⁺ deficiency is a common central pathological factor in a number of disease and aging." It is also necessary to further investigate the mechanisms underlying the NAD⁺ deficiency in the diseases and aging. Preclinical and clinical studies should be conducted to determine the therapeutic potential of NAD⁺ for the diseases and aging.

Macrophage Migration Inhibitory Factor (MIF) Expression Increases during Myocardial Infarction and Supports Pro-Inflammatory Signaling in Cardiac Fibroblasts

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine known to play a major role in inflammatory diseases such as myocardial infarction (MI), where its expression increases. Cardio-protective functions of MIF during ischemia have been reported. Recently, the structurally related MIF-2 was identified and similar effects are assumed. We wanted to further investigate the role of MIF and MIF-2 on inflammatory processes during MI. Therefore, we subjected mice to experimentally induced MI by coronary occlusion for one and five days. During the acute phase of MI, the gene expression of Mif was upregulated in the infarct zone, whereas Mif-2 was downregulated, suggesting a minor role of MIF-2. Simulating ischemic conditions or mechanical stress in vitro, we demonstrated that Mif expression was induced in resident cardiac cells. To investigate possible auto-/paracrine effects, cardiomyocytes and cardiac fibroblasts were individually treated with recombinant murine MIF, which in turn induced Mif expression and the expression of pro-inflammatory genes in cardiac fibroblasts. Cardiomyocytes did not respond to recombinant MIF with pro-inflammatory gene expression. While MIF stimulation alone did not change the expression of pro-fibrotic genes in cardiac fibroblasts, ischemia reduced their expression. Mimicking the increased MIF levels during MI, we exposed cardiac fibroblasts to simulated ischemia in the presence of MIF, which led to further reduced expression of pro-fibrotic genes. The presented data show that MIF was expressed by resident cardiac cells during MI. In vitro, Mif expression was induced by different external stimuli in cardiomyocytes and cardiac fibroblasts. Addition of recombinant MIF protein increased the expression of pro-inflammatory genes in cardiac fibroblasts including Mif expression itself. Thereby, cardiac fibroblasts may amplify Mif expression during ischemia promoting cardiomyocyte survival.

The Janus face of HMGB1 in heart disease: a necessary update

High mobility group box 1 (HMGB1) is a ubiquitous nuclear protein involved in transcription regulation, DNA replication and repair and nucleosome assembly. HMGB1 is passively released by necrotic tissues or actively secreted by stressed cells. Extracellular HMGB1 acts as a damage-associated molecular pattern (DAMPs) molecule and gives rise to several redox forms that by binding to different receptors and interactors promote a variety of cellular responses, including tissue inflammation or regeneration. Inhibition of extracellular HMGB1 in experimental models of myocardial ischemia/reperfusion injury, myocarditis, cardiomyopathies induced by mechanical stress, diabetes, bacterial infection or chemotherapeutic drugs reduces inflammation and is protective. In contrast, administration of HMGB1 after myocardial infarction induced by permanent coronary artery ligation ameliorates cardiac performance by promoting tissue regeneration. HMGB1 decreases contractility and induces hypertrophy and apoptosis in cardiomyocytes, stimulates cardiac fibroblast activities, and promotes cardiac stem cell proliferation and differentiation. Interestingly, maintenance of appropriate nuclear HMGB1 levels protects cardiomyocytes from apoptosis by preventing DNA oxidative stress, and mice with HMGB1cardiomyocyte-specific overexpression are partially protected from cardiac damage. Finally, higher levels of circulating HMGB1 are associated to human heart diseases. Hence, during cardiac injury, HMGB1 elicits both harmful and beneficial responses that may in part depend on the generation and stability of the diverse redox forms, whose specific functions in this context remain mostly unexplored. This review summarizes recent findings on HMGB1 biology and heart dysfunctions and discusses the therapeutic potential of modulating its expression, localization, and oxidative-dependent activities.

In Vitro Macrophage Assay Predicts the In Vivo Anti-inflammatory Potential of Exosomes from Human Mesenchymal Stromal Cells

Extracellular vesicles (EVs) play key roles in cell biology and may provide new clinical diagnostics and therapies. However, it has proven difficult to develop protocols for their purification and characterization. One of the major barriers in the field has been a lack of convenient assays for their bioactivity. Developing assays has not been a trivial matter, because of the heterogeneity of EVs, the multiple activities they demonstrate, and the uncertainty about their modes of action. Therefore, it is likely that multiple assays for their activities are needed. One important assay will be for the anti-inflammatory activity observed in mice after administration of the small EVs commonly referred to as exosomes. We developed an assay for the anti-inflammatory activity of exosomes with a line of mouse macrophages. The assay makes it possible to rank different preparations of exosomes by their anti-inflammatory activity, and their ranking predicts their efficacy in suppressing LPS-stimulated inflammation in mice. The assay is convenient for comparing multiple samples and, therefore, should be useful in developing protocols for the purification and characterization of anti-inflammatory exosomes.

Sirt3 attenuates post-infarction cardiac injury via inhibiting mitochondrial fission and normalization of AMPK-Drp1 pathways

Mitochondrial damage is involved in the pathogenesis of post-infarction cardiac injury. However, the upstream regulators of mitochondrial damage have not yet been identified. The aim of our study is to explore the role of Sirt3 in post-infarction cardiac injury with a particular focus on mitochondrial fission and AMPK-Drp1 pathways. Our results indicated that Sirt3 was downregulated in the progression of post-infarction cardiac injury. Overexpression of Sirt3 attenuated cardiac fibrosis, sustained myocardial function, inhibited the inflammatory response, and reduced cardiomyocyte death. Functional studies illustrated that chronic post-infarction cardiac injury was characterized by increased mitochondrial fission, which triggered mitochondrial oxidative stress, metabolic disorders, mitochondrial potential reduction and caspase-9 apoptosis in cardiomyocytes. However, Sirt3 overexpression attenuated mitochondrial fission and thus preserved mitochondrial homeostasis and cardiomyocyte viability. Furthermore, our results confirmed that Sirt3 repressed mitochondrial fission via normalizing AMPK-Drp1 pathways. Inhibition of AMPK activity re-activated Drp1 and thus abrogated the inhibitory effect of Sirt3 on mitochondrial fission. Altogether, our results indicate that Sirt3 enhancement could be an effective approach to retard the development of post-infarction cardiac injury via disrupting mitochondrial fission and normalizing the AMPK-Drp1 axis.

New Paradigms in Cell Therapy: Repeated Dosing, Intravenous Delivery, Immunomodulatory Actions, and New Cell Types

Perhaps the most important advance in the field of cell therapy for heart disease has been the recognition that all stem/progenitor cells (both adult and embryonic) fail to engraft in the heart to a significant extent and thus work via paracrine mechanisms. This fundamental advance has led to 4 new paradigms that are discussed in this review and that may importantly shape, or even revolutionize, the future of the field: (1) repeated cell therapy, (2) intravenous cell therapy, (3) immunomodulatory actions of cell therapy, and (4) new cell types. Because virtually all of our current knowledge of cell therapy is predicated on the effects of a single cell dose, the idea that the full therapeutic effects of a cell product require repeated doses is disruptive and has far-reaching implications. For example, inadequate dosing (single-dose protocols) may be responsible, at least in part, for the borderline or disappointing results obtained to date in clinical trials; furthermore, future studies (both preclinical and clinical) may need to incorporate repeated cell administrations. Another disruptive idea, supported by emerging preclinical and clinical evidence, is that intravenously injected cells can produce beneficial effects on the heart, presumably via release of paracrine factors in extracardiac organs or endocrine factors into the systemic circulation. Intravenous administration would obviate the need for direct delivery of cells to the heart, making cell therapy simpler, cheaper, safer, more scalable, and more broadly available, even on an outpatient basis. Although the mechanism of action of cell therapy remains elusive, there is compelling in vitro evidence that transplanted cells modulate the function of various immune cell types via release of paracrine factors, such as extracellular vesicles, although in vivo evidence is still limited. Investigation of the new paradigms reviewed herein should be a top priority because it may profoundly transform cell therapy and finally make it a reality.

A Tumor Necrosis Factor-α and Hypoxia-Induced Secretome Therapy for Myocardial Repair

BACKGROUND

Poor viability and retention of transplanted bone marrow mesenchymal stem cells (BM-MSC) remains an obstacle in promoting healing after myocardial infarction (MI). This study aimed to understand the migratory, angiogenic, and cardioprotective effects induced by tumor necrosis factor (TNF)-α and hypoxia through rat BM-MSC (rBM-MSC) paracrine secretions, collectively referred to as secretome, after MI.

METHODS

Secretome from rBM-MSC cultures treated with various combinations of H9c2 cardiomyoblast-conditioned medium, TNF-α, and hypoxia was initially collected. Immunocytochemistry, Western blot analyses, and transwell cell migration assays were conducted. In vivo, echocardiography was performed on rats with induced MI after their treatment with TNF-α and hypoxia-induced secretome.

RESULTS

Immunocytochemistry confirmed the presence of TNF receptors 1 and 2 on rBM-MSCs. Western blot analyses of rBM-MSCs treated with TNF-α and hypoxia showed an overall increasing trend in the expression of antiinflammatory proteins and angiogenic and migratory cytokines (transforming growth factor-β, fibroblast growth factor-2, angiopoietin-2, vascular endothelial growth factor-1). In addition, the TNF-α and hypoxia-induced secretome significantly increased the in vitro rBM-MSCs migration. In the rat MI model, the rats treated with the TNF-α and hypoxia-induced secretome had a significantly higher left ventricular fractional shortening than the control group.

CONCLUSIONS

Our data suggest that after MI, rBM-MSCs secrete paracrine factors in response to TNF-α and hypoxia that work together to manipulate the microenvironment and decrease inflammation. In addition, these signaling factors trigger angiogenic and migratory effects at the site of the infarct to promote myocardial healing and improve the cardiac function.

Discrepant Results of Experimental Human Mesenchymal Stromal Cell Therapy after Myocardial Infarction: Are Animal Models Robust Enough?

Background

Human mesenchymal stromal cells (MSCs) have been reported to preserve cardiac function in myocardial infarction (MI) models. Previously, we found a beneficial effect of intramyocardial injection of unstimulated human MSCs (uMSCs) on cardiac function after permanent coronary artery ligation. In the present study we aimed to extend this research by investigating the effect of intramyocardial injection of human MSCs pre-stimulated with the pro-inflammatory cytokine interferon-gamma (iMSCs), since pro-inflammatory priming has shown additional salutary effects in multiple experimental disease models.

Methods

MI was induced in NOD/Scid mice by permanent ligation of the left anterior descending coronary artery. Animals received intramyocardial injection of uMSCs, iMSCs or PBS. Sham-operated animals were used to determine baseline characteristics. Cardiac performance was assessed after 2 and 14 days using 7-Tesla magnetic resonance imaging and pressure-volume loop measurements. Histology and q-PCR were used to confirm MSC engraftment in the heart.

Results

Both uMSC and iMSC therapy had no significant beneficial effect on cardiac function or remodelling in contrast to our previous studies.

Conclusions

Animal models for cardiac MSC therapy appear less robust than initially envisioned.