CCR2 macrophage response determines the functional outcome following cardiomyocyte transplantation

BACKGROUND

The immune response is a crucial factor for mediating the benefit of cardiac cell therapies. Our previous research showed that cardiomyocyte transplantation alters the cardiac immune response and, when combined with short-term pharmacological CCR2 inhibition, resulted in diminished functional benefit. However, the specific role of innate immune cells, especially CCR2 macrophages on the outcome of cardiomyocyte transplantation, is unclear.

METHODS

We compared the cellular, molecular, and functional outcome following cardiomyocyte transplantation in wildtype and T cell- and B cell-deficient Rag2del mice. The cardiac inflammatory response was assessed using flow cytometry. Gene expression profile was assessed using single-cell and bulk RNA sequencing. Cardiac function and morphology were determined using magnetic resonance tomography and immunohistochemistry respectively.

RESULTS

Compared to wildtype mice, Rag2del mice show an increased innate immune response at steady state and disparate macrophage response after MI. Subsequent single-cell analyses after MI showed differences in macrophage development and a lower prevalence of CCR2 expressing macrophages. Cardiomyocyte transplantation increased NK cells and monocytes, while reducing CCR2-MHC-IIlo macrophages. Consequently, it led to increased mRNA levels of genes involved in extracellular remodelling, poor graft survival, and no functional improvement. Using machine learning-based feature selection, Mfge8 and Ccl7 were identified as the primary targets underlying these effects in the heart.

CONCLUSIONS

Our results demonstrate that the improved functional outcome following cardiomyocyte transplantation is dependent on a specific CCR2 macrophage response. This work highlights the need to study the role of the immune response for cardiomyocyte cell therapy for successful clinical translation.

New Approaches in Heart Research: Prevention Instead of Cardiomyoplasty?

Cardiovascular diseases are the leading cause of death in industrialized nations. Due to the high number of patients and expensive treatments, according to the Federal Statistical Office (2017) in Germany, cardiovascular diseases account for around 15% of total health costs. Advanced coronary artery disease is mainly the result of chronic disorders such as high blood pressure, diabetes, and dyslipidemia. In the modern obesogenic environment, many people are at greater risk of being overweight or obese. The hemodynamic load on the heart is influenced by extreme obesity, which often leads to myocardial infarction (MI), cardiac arrhythmias, and heart failure. In addition, obesity leads to a chronic inflammatory state and negatively affects the wound-healing process. It has been known for many years that lifestyle interventions such as exercise, healthy nutrition, and smoking cessation drastically reduce cardiovascular risk and have a preventive effect against disorders in the healing process. However, little is known about the underlying mechanisms, and there is significantly less high-quality evidence compared to pharmacological intervention studies. Due to the immense potential of prevention in heart research, the cardiologic societies are calling for research work to be intensified, from basic understanding to clinical application. The topicality and high relevance of this research area are also evident from the fact that in March 2018, a one-week conference on this topic with contributions from top international scientists took place as part of the renowned "Keystone Symposia" ("New Insights into the Biology of Exercise"). Consistent with the link between obesity, exercise, and cardiovascular disease, this review attempts to draw lessons from stem-cell transplantation and preventive exercise. The application of state-of-the-art techniques for transcriptome analysis has opened new avenues for tailoring targeted interventions to very individual risk factors.

The Effects of Hypoxic Preconditioned Murine Mesenchymal Stem Cells on Post-Infarct Arrhythmias in the Mouse Model

Ventricular arrhythmias associated with myocardial infarction (MI) have a significant impact on mortality in patients following heart attack. Therefore, targeted reduction of arrhythmia represents a therapeutic approach for the prevention and treatment of severe events after infarction. Recent research transplanting mesenchymal stem cells (MSC) showed their potential in MI therapy. Our study aimed to investigate the effects of MSC injection on post-infarction arrhythmia. We used our murine double infarction model, which we previously established, to more closely mimic the clinical situation and intramyocardially injected hypoxic pre-conditioned murine MSC to the infarction border. Thereafter, various types of arrhythmias were recorded and analyzed. We observed a homogenous distribution of all types of arrhythmias after the first infarction, without any significant differences between the groups. Yet, MSC therapy after double infarction led to a highly significant reduction in simple and complex arrhythmias. Moreover, RNA-sequencing of samples from stem cell treated mice after re-infarction demonstrated a significant decline in most arrhythmias with reduced inflammatory pathways. Additionally, following stem-cell therapy we found numerous highly expressed genes to be either linked to lowering the risk of heart failure, cardiomyopathy or sudden cardiac death. Moreover, genes known to be associated with arrhythmogenesis and key mutations underlying arrhythmias were downregulated. In summary, our stem-cell therapy led to a reduction in cardiac arrhythmias after MI and showed a downregulation of already established inflammatory pathways. Furthermore, our study reveals gene regulation pathways that have a potentially direct influence on arrhythmogenesis after myocardial infarction.

Hematopoietic stem-cell senescence and myocardial repair - Coronary artery disease genotype/phenotype analysis of post-MI myocardial regeneration response induced by CABG/CD133+ bone marrow hematopoietic stem cell treatment in RCT PERFECT Phase 3

Background

Bone marrow stem cell clonal dysfunction by somatic mutation is suspected to affect post-infarction myocardial regeneration after coronary bypass surgery (CABG).

Methods

Transcriptome and variant expression analysis was studied in the phase 3 PERFECT trial post myocardial infarction CABG and CD133⁺ bone marrow derived hematopoetic stem cells showing difference in left ventricular ejection fraction (∆LVEF) myocardial regeneration Responders (n=14; ∆LVEF +16% day 180/0) and Non-responders (n=9; ∆LVEF -1.1% day 180/0). Subsequently, the findings have been validated in an independent patient cohort (n=14) as well as in two preclinical mouse models investigating SH2B3/LNK antisense or knockout deficient conditions.

Findings

1. Clinical: R differed from NR in a total of 161 genes in differential expression (n=23, q<0•05) and 872 genes in coexpression analysis (n=23, q<0•05). Machine Learning clustering analysis revealed distinct RvsNR preoperative gene-expression signatures in peripheral blood acorrelated to SH2B3 (p<0.05). Mutation analysis revealed increased specific variants in RvsNR. (R: 48 genes; NR: 224 genes). 2. Preclinical:SH2B3/LNK-silenced hematopoietic stem cell (HSC) clones displayed significant overgrowth of myeloid and immune cells in bone marrow, peripheral blood, and tissue at day 160 after competitive bone-marrow transplantation into mice. SH2B3/LNK^−/− mice demonstrated enhanced cardiac repair through augmenting the kinetics of bone marrow-derived endothelial progenitor cells, increased capillary density in ischemic myocardium, and reduced left ventricular fibrosis with preserved cardiac function. 3. Validation: Evaluation analysis in 14 additional patients revealed 85% RvsNR (12/14 patients) prediction accuracy for the identified biomarker signature.

Interpretation

Myocardial repair is affected by HSC gene response and somatic mutation. Machine Learning can be utilized to identify and predict pathological HSC response.

Funding

German Ministry of Research and Education (BMBF): Reference and Translation Center for Cardiac Stem Cell Therapy - FKZ0312138A and FKZ031L0106C, German Ministry of Research and Education (BMBF): Collaborative research center - DFG:SFB738 and Center of Excellence - DFG:EC-REBIRTH), European Social Fonds: ESF/IV-WM-B34-0011/08, ESF/IV-WM-B34-0030/10, and Miltenyi Biotec GmbH, Bergisch-Gladbach, Germany. Japanese Ministry of Health : Health and Labour Sciences Research Grant (H14-trans-001, H17-trans-002)

Trial registration

ClinicalTrials.gov NCT00950274

Dose-Independent Therapeutic Benefit of Bone Marrow Stem Cell Transplantation after MI in Mice

Several cell populations derived from bone marrow (BM) have been shown to possess cardiac regenerative potential. Among these are freshly isolated CD133⁺ hematopoietic as well as culture-expanded mesenchymal stem cells. Alternatively, by purifying CD271⁺ cells from BM, mesenchymal progenitors can be enriched without an ex vivo cultivation. With regard to the limited available number of freshly isolated BM-derived stem cells, the effect of the dosage on the therapeutic efficiency is of particular interest. Therefore, in the present pre-clinical study, we investigated human BM-derived CD133⁺ and CD271⁺ stem cells for their cardiac regenerative potential three weeks post-myocardial infarction (MI) in a dose-dependent manner. The improvement of the hemodynamic function as well as cardiac remodeling showed no therapeutic difference after the transplantation of both 100,000 and 500,000 stem cells. Therefore, beneficial stem cell transplantation post-MI is widely independent of the cell dose and detrimental stem cell amplification in vitro can likely be avoided.

Vimentin-Induced Cardiac Mesenchymal Stem Cells Proliferate in the Acute Ischemic Myocardium

In-depth knowledge of the mechanisms induced by early postischemic cardiac endogenous mesenchymal stem cells (MSCs) in the acutely ischemic heart could advance our understanding of cardiac regeneration. Herein, we aimed to identify, isolate, and initially characterize the origin, kinetics and fate of cardiac MSCs. This was facilitated by in vivo genetic cell fate mapping through green fluorescent protein (GFP) expression under the control of vimentin induction after acute myocardial infarction (MI). Following permanent ligation of the left anterior descending coronary artery in CreER+ mTom/mGFP+ mice, vimentin/GFP+ cells revealed ischemia-responsive activation, survival, and local enrichment inside the peri-infarction border zone. Fluorescence-activated cell sorting (FACS)-isolated vimentin/GFP+ cells could be strongly expanded in vitro with clonogenic precursor formation and revealed MSC-typical cell morphology. Flow-cytometric analyses demonstrated an increase in cardiac vimentin/GFP+ cells in the ischemic heart, from a 0.6% cardiac mononuclear cell (MNC) fraction at 24 h to 1.6% at 72 h following MI. Sca-1+CD45- cells within the vimentin/GFP+ subtype of this MNC fraction increased from 35.2% at 24 h to 74.6% at 72 h after MI. The cardiac postischemic vimentin/GFP+ MNC subtype showed multipotent adipogenic, chondrogenic, and osteogenic differentiation potential, which is distinctive for MSCs. In conclusion, we demonstrated a seemingly proliferative first response of vimentin- induced cardiac endogenous MSCs in the acutely ischemic heart. Genetically, GFP-targeted in vivo cell tracking, isolation, and in vitro expansion of this cardiac MSC subtype could help to clarify their reparative status in inflammation, fibrogenesis, cell turnover, tissue homeostasis, and myocardial regeneration.

Intramyocardial angiogenetic stem cells and epicardial erythropoietin save the acute ischemic heart

Ischemic heart failure is the leading cause of mortality worldwide. An early boost of intracardiac regenerative key mechanisms and angiogenetic niche signaling in cardiac mesenchymal stem cells (MSCs) could improve myocardial infarction (MI) healing. Epicardial erythropoietin (EPO; 300 U kg^-1) was compared with intraperitoneal and intramyocardial EPO treatments after acute MI in rats (n=156). Real-time PCR and confocal microscopy revealed that epicardial EPO treatment enhanced levels of intracardiac regenerative key indicators (SDF-1, CXCR4, CD34, Bcl-2, cyclin D1, Cdc2 and MMP2), induced transforming growth factor β (TGF-β)/WNT signaling in intramyocardial MSC niches through the direct activation of AKT and upregulation of upstream signals FOS and Fzd7, and augmented intracardiac mesenchymal proliferation 24 h after MI. Cardiac catheterization and tissue analysis showed superior cardiac functions, beneficial remodeling and increased capillary density 6 weeks after MI. Concomitant fluorescence-activated cell sorting, co-cultures with neonatal cardiomyocytes, angiogenesis assays, ELISA, western blotting and RAMAN spectroscopy demonstrated that EPO could promote cardiomyogenic differentiation that was specific of tissue origin and enhance paracrine angiogenetic activity in cardiac CD45^-CD44⁺DDR2⁺ MSCs. Epicardial EPO delivery might be the optimal route for efficient upregulation of regenerative key signals after acute MI. Early EPO-mediated stimulation of mesenchymal proliferation, synergistic angiogenesis with cardiac MSCs and direct induction of TGF-β/WNT signaling in intramyocardial cardiac MSCs could initiate an accelerated healing process that enhances cardiac recovery.

Cardiac Mesenchymal Stem Cells Proliferate Early in the Ischemic Heart

BACKGROUND/PURPOSE

Cardiac mesenchymal stem cells (MSCs) could stimulate cell-specific regenerative mechanisms after myocardial infarction (MI) depending on spatial origin, distribution, and niche regulation. We aimed at identifying and isolating tissue-specific cardiac MSCs that could contribute to regeneration.

METHODS

Following permanent ligation of the left anterior descending coronary artery in rats (n = 16), early cardiac tissues and cardiac mononuclear cells (MNCs) were analyzed by immunohistology, confocal laser scanning microscopy, and flow cytometry, respectively. Early postischemic specific MSCs were purified by fluorescence-activated cell sorting, cultivated under standardized culture conditions, and tested for multipotent differentiation in functional identification kits.

RESULTS

Cardiac MSC niches were detected intramyocardially in cell clusters after MI and characterized by positive expression for vimentin, CD29, CD44, CD90, CD105, PDGFRα, and DDR2. Following myocardial ischemia, proliferation was induced early and proliferation density was approximately 11% in intramyocardial MSC clusters of the peri-infarction border zone. Cluster sizes increased by 157 and 64% in the peri-infarction and noninfarcted areas of infarcted hearts compared with noninfarcted hearts 24 h following MI, respectively. Coincidentally, flow cytometry analyses illustrated postischemic moderate enrichments of CD45-CD44+ and CD45-DDR2+ cardiac MNCs. We enabled isolation of early postischemic culturable cardiac CD45-CD44+DDR2+ MSCs that demonstrated typical clonogenicity with colony-forming unit-fibroblast formation as well as adipogenic, chondrogenic, and osteogenic differentiation.

CONCLUSIONS

MI triggered early proliferation in specific cardiac MSC niches that were organized in intramyocardial clusters. Following targeted isolation, early postischemic cardiac CD45-CD44+DDR2+ MSCs exhibited typical characteristics with multipotent differentiation capacity and clonogenic expansion.

Intramyocardial fate and effect of iron nanoparticles co-injected with MACS® purified stem cell products

BACKGROUND

Magnetic activated cell sorting (MACS^®) is routinely used to isolate stem cell subpopulations intended for the treatment of cardiovascular diseases. In strong contrast, studies examining the amount, effect and intramyocardial distribution of iron nanoparticles used for magnetic cell labelling are missing, although iron excess can cause functional disorders in the heart.

METHODS AND RESULTS

CD133⁺ haematopoietic and CD271⁺ mesenchymal stem cells were purified from bone marrow using automatically and manually MACS^® based systems. Flow cytometric measurements demonstrated a rapid loss of MACS^® MicroBeads from cells under culture conditions, while storage under hypothermic conditions decelerated their detachment. Moreover, an average loading of ∼11 fg iron/cell caused by magnetic labelling was determined in magnetic particle spectroscopy. Importantly, hemodynamic measurements as well as histological examinations using a myocardial ischemia/reperfusion mouse model showed no influence of MACS^® MicroBeads on cardiac regeneration, while the transplantation of stem cells caused a significant improvement. Furthermore, immunostainings demonstrated the clearance of co-injected iron nanoparticles from stem cells and the surrounding heart tissue within 48 h post transplantation.

CONCLUSIONS

Our results indicate that iron amounts typically co-injected with MACS^® purified stem cells do not harm cardiac functions and are cleared from heart tissue within a few hours. Therefore, we conclude that MACS^® MicroBeads exhibit a good compatibility in the cardiac environment.

GMP-conformant on-site manufacturing of a CD133+ stem cell product for cardiovascular regeneration

Background

CD133⁺ stem cells represent a promising subpopulation for innovative cell-based therapies in cardiovascular regeneration. Several clinical trials have shown remarkable beneficial effects following their intramyocardial transplantation. Yet, the purification of CD133⁺ stem cells is typically performed in centralized clean room facilities using semi-automatic manufacturing processes based on magnetic cell sorting (MACS®). However, this requires time-consuming and cost-intensive logistics.

Methods

CD133⁺ stem cells were purified from patient-derived sternal bone marrow using the recently developed automatic CliniMACS Prodigy® BM-133 System (Prodigy). The entire manufacturing process, as well as the subsequent quality control of the final cell product (CP), were realized on-site and in compliance with EU guidelines for Good Manufacturing Practice. The biological activity of automatically isolated CD133⁺ cells was evaluated and compared to manually isolated CD133⁺ cells via functional assays as well as immunofluorescence microscopy. In addition, the regenerative potential of purified stem cells was assessed 3 weeks after transplantation in immunodeficient mice which had been subjected to experimental myocardial infarction.

Results

We established for the first time an on-site manufacturing procedure for stem CPs intended for the treatment of ischemic heart diseases using an automatized system. On average, 0.88 × 10⁶ viable CD133⁺ cells with a mean log₁₀ depletion of 3.23 ± 0.19 of non-target cells were isolated. Furthermore, we demonstrated that these automatically isolated cells bear proliferation and differentiation capacities comparable to manually isolated cells in vitro. Moreover, the automatically generated CP shows equal cardiac regeneration potential in vivo.

Conclusions

Our results indicate that the Prodigy is a powerful system for automatic manufacturing of a CD133⁺ CP within few hours. Compared to conventional manufacturing processes, future clinical application of this system offers multiple benefits including stable CP quality and on-site purification under reduced clean room requirements. This will allow saving of time, reduced logistics and diminished costs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0467-0) contains supplementary material, which is available to authorized users.

Exploiting AT2R to Improve CD117 Stem Cell Function In Vitro and In Vivo--Perspectives for Cardiac Stem Cell Therapy

BACKGROUND/AIMS

CD117(+) stem cell (SC) based therapy is considered an alternative therapeutic option for terminal heart disease. However, controversies exist on the effects of CD117(+) SC implantation. In particular, the link between CD117(+) SC function and angiotensin-II-type-2 receptor (AT2R) after MI is continuously discussed. We therefore asked whether 1) AT2R stimulation influences CD117(+) SC properties in vitro and, 2) which effects can be ascribed to AT2R stimulation in vivo.

METHODS

We approached AT2R stimulation with Angiotensin II while simultaneously blocking its opponent receptor AT1 with Losartan. CD117 effects were dissected using a 2D-Matrigel assay and HL-1 co-culture in vitro. A model of myocardial infarction, in which we implanted EGFP(+) CD117 SC, was further applied.

RESULTS

While we found indications for AT2R driven vasculogenesis in vitro, co-culture experiments revealed that CD117(+) SC improve vitality of cardiomyocytes independently of AT2R function. Likewise, untreated CD117(+) SC had a positive effect on cardiac function and acted cardioprotective in vivo.

CONCLUSIONS

Therefore, our data show that transient AT2R stimulation does not significantly add to the beneficial actions of CD117(+) SC in vivo. Yet, exploiting AT2R driven vasculogenis via an optimized AT2R stimulation protocol may become a promising tool for cardiac SC therapy.

The CD4(+) AT2R(+) T cell subpopulation improves post-infarction remodelling and restores cardiac function

Myocardial infarction (MI) is a major condition causing heart failure (HF). After MI, the renin angiotensin system (RAS) and its signalling octapeptide angiotensin II (Ang II) interferes with cardiac injury/repair via the AT1 and AT2 receptors (AT1R, AT2R). Our study aimed at deciphering the mechanisms underlying the link between RAS and cellular components of the immune response relying on a rodent model of HF as well as HF patients. Flow cytometric analyses showed an increase in the expression of CD4(+) AT2R(+) cells in the rat heart and spleen post-infarction, but a reduction in the peripheral blood. The latter was also observed in HF patients. The frequency of rat CD4(+) AT2R(+) T cells in circulating blood, post-infarcted heart and spleen represented 3.8 ± 0.4%, 23.2 ± 2.7% and 22.6 ± 2.6% of the CD4(+) cells. CD4(+) AT2R(+) T cells within blood CD4(+) T cells were reduced from 2.6 ± 0.2% in healthy controls to 1.7 ± 0.4% in patients. Moreover, we characterized CD4(+) AT2R(+) T cells which expressed regulatory FoxP3, secreted interleukin-10 and other inflammatory-related cytokines. Furthermore, intramyocardial injection of MI-induced splenic CD4(+) AT2R(+) T cells into recipient rats with MI led to reduced infarct size and improved cardiac performance. We defined CD4(+) AT2R(+) cells as a T cell subset improving heart function post-MI corresponding with reduced infarction size in a rat MI-model. Our results indicate CD4(+) AT2R(+) cells as a promising population for regenerative therapy, via myocardial transplantation, pharmacological AT2R activation or a combination thereof.

Patterning human stem cells and endothelial cells with laser printing for cardiac regeneration

Recent study showed that mesenchymal stem cells (MSC) could inhibit apoptosis of endothelial cells in hypoxic condition, increase their survival, and stimulate the angiogenesis process. In this project we applied Laser-Induced-Forward-Transfer (LIFT) cell printing technique and prepared a cardiac patch seeded with human umbilical vein endothelial cells (HUVEC) and human MSC (hMSC) in a defined pattern for cardiac regeneration. We seeded HUVEC and hMSC in a defined pattern on a Polyester urethane urea (PEUU) cardiac patch. On control patches an equal amount of cells was randomly seeded without LIFT. Patches were cultivated in vitro or transplanted in vivo to the infarcted zone of rat hearts after LAD-ligation. Cardiac performance was measured by left ventricular catheterization 8 weeks post infarction. Thereafter hearts were perfused with fluorescein tomato lectin for the assessment of functional blood vessels and stored for histology analyses. We demonstrated that LIFT-derived cell seeding pattern definitely modified growth characteristics of co-cultured HUVEC and hMSC leading to increased vessel formation and found significant functional improvement of infarcted hearts following transplantation of a LIFT-tissue engineered cardiac patch. Further, we could show enhanced capillary density and integration of human cells into the functionally connected vessels of murine vascular system. LIFT-based Tissue Engineering of cardiac patches for the treatment of myocardial infarction might improve wound healing and functional preservation.

Laser printing of skin cells and human stem cells

Laser printing based on laser-induced forward transfer (LIFT) is a new biofabrication technique for the arrangement of biological materials or living cells in well-defined patterns. In the current study, skin cell lines (fibroblasts/keratinocytes) and human mesenchymal stem cells (hMSC) were chosen for laser printing experiments due to their high potential in regeneration of human skin and new application possibilities of stem cell therapy. To evaluate the influence of LIFT on the cells, their survival rate, their proliferation and apoptotic activity, and the DNA damages and modifications of their cell surface markers were assessed and statistically evaluated over several days. The cells survived the transfer procedure with a rate of 98%  +/- 1% standard error of the mean (skin cells) and 90%  +/- 10% (hMSC), respectively. All used cell types maintain their ability to proliferate after LIFT. Further, skin cells and hMSC did not show an increase of apoptosis or DNA fragmentation. In addition, the hMSC keep their phenotype as proven by fluorescence activated cell sorting (FACS) analysis. This study demonstrates LIFT as a suitable technique for unharmed computer-controlled positioning of different cell types and a promising tool for future applications in the ex vivo generation of tissue replacements.

Cell origin of human mesenchymal stem cells determines a different healing performance in cardiac regeneration

The possible different therapeutic efficacy of human mesenchymal stem cells (hMSC) derived from umbilical cord blood (CB), adipose tissue (AT) or bone marrow (BM) for the treatment of myocardial infarction (MI) remains unexplored. This study was to assess the regenerative potential of hMSC from different origins and to evaluate the role of CD105 in cardiac regeneration. Male SCID mice underwent LAD-ligation and received the respective cell type (400.000/per animal) intramyocardially. Six weeks post infarction, cardiac catheterization showed significant preservation of left ventricular functions in BM and CD105(+)-CB treated groups compared to CB and nontreated MI group (MI-C). Cell survival analyzed by quantitative real time PCR for human GAPDH and capillary density measured by immunostaining showed consistent results. Furthermore, cardiac remodeling can be significantly attenuated by BM-hMSC compared to MI-C. Under hypoxic conditions in vitro, remarkably increased extracellular acidification and apoptosis has been detected from CB-hMSC compared to BM and CD105 purified CB-derived hMSC. Our findings suggests that hMSC originating from different sources showed a different healing performance in cardiac regeneration and CD105(+) hMSC exhibited a favorable survival pattern in infarcted hearts, which translates into a more robust preservation of cardiac function.