A characterization and targeting of the infarct border zone in a swine model of myocardial infarction

3D bioprinted aged human post-infarct myocardium tissue model

Background and Aims

Fibrotic tissue formed after myocardial infarction (MI) can be as detrimental as MI itself. However, current in vitro cardiac fibrosis models fail to recapitulate the complexities of post-MI tissue. Moreover, although MI and subsequent fibrosis is most prominent in the aged population, the field suffers from inadequate aged tissue models. Herein, an aged human post-MI tissue model, representing the native microenvironment weeks after initial infarction, is engineered using three-dimensional bioprinting via creation of individual bioinks to specifically mimic three distinct regions: remote, border, and scar.

Methods

The aged post-MI tissue model is engineered through combination of gelatin methacryloyl, methacrylated hyaluronic acid, aged type I collagen, and photoinitiator at variable concentrations with different cell types, including aged human induced pluripotent stem cell-derived cardiomyocytes, endothelial cells, cardiac fibroblasts, and cardiac myofibroblasts, by introducing a methodology which utilizes three printheads of the bioprinter to model aged myocardium. Then, using cell-specific proteins, the cell types that comprised each region are confirmed using immunofluorescence. Next, the beating characteristics are analyzed. Finally, the engineered aged post-MI tissue model is used as a benchtop platform to assess the therapeutic effects of stem cell-derived extracellular vesicles on the scar region.

Results

As a result, high viability (>74%) was observed in each region of the printed model. Constructs demonstrated functional behavior, exhibiting a beating velocity of 6.7 μm/s and a frequency of 0.3 Hz. Finally, the effectiveness of hiPSC-EV and MSC-EV treatment was assessed. While hiPSC-EV treatment showed no significant changes, MSC-EV treatment notably increased cardiomyocyte beating velocity, frequency, and confluency, suggesting a regenerative potential.

Conclusion

In conclusion, we envision that our approach of modeling post-MI aged myocardium utilizing three printheads of the bioprinter may be utilized for various applications in aged cardiac microenvironment modeling and testing novel therapeutics.

Assessment of Myocardial Diastolic Dysfunction as a Result of Myocardial Infarction and Extracellular Matrix Regulation Disorders in the Context of Mesenchymal Stem Cell Therapy

The decline in cardiac contractility due to damage or loss of cardiomyocytes is intensified by changes in the extracellular matrix leading to heart remodeling. An excessive matrix response in the ischemic cardiomyopathy may contribute to the elevated fibrotic compartment and diastolic dysfunction. Fibroproliferation is a defense response aimed at quickly closing the damaged area and maintaining tissue integrity. Balance in this process is of paramount importance, as the reduced post-infarction response causes scar thinning and more pronounced left ventricular remodeling, while excessive fibrosis leads to impairment of heart function. Under normal conditions, migration of progenitor cells to the lesion site occurs. These cells have the potential to differentiate into myocytes in vitro, but the changed micro-environment in the heart after infarction does not allow such differentiation. Stem cell transplantation affects the extracellular matrix remodeling and thus may facilitate the improvement of left ventricular function. Studies show that mesenchymal stem cell therapy after infarct reduces fibrosis. However, the authors did not specify whether they meant the reduction of scarring as a result of regeneration or changes in the matrix. Research is also necessary to rule out long-term negative effects of post-acute infarct stem cell therapy.

Myocardial infarct border demarcation by dual-wavelength photoacoustic spectral analysis

Myocardial infarction (MI) is a major cause of morbidity and mortality worldwide. Modern therapeutic strategies targeting the infarct border area have been shown to benefit overall cardiac function after MI. However, there is no non-invasive diagnostic technique to precisely demarcate the MI boundary till to now. In this study, the feasibility of demarcating the MI border using dual-wavelength photoacoustic spectral analysis (DWPASA) was investigated. To quantify specific molecular characteristics before and after MI, "the ratio of the areas of the power spectral densities (R APSD)" was computed from the DWPASA results. Compared to the normal tissue, MI tissue was shown to contain more collagen, resulting in higher R APSD values (p < 0.001). Cross-sectional MI lengths and the MI area border demarcated in two dimensions by DWPASA were in substantial agreement with Masson staining (ICC = 0.76, p < 0.001, IoU = 0.72). R APSD has been proved that can be used as an indicator of disease evolution to distinguish normal and pathological tissues. These findings indicate that the DWPASA method may offer a new diagnostic solution for determining MI borders.

Modulating mitochondrial dynamics attenuates cardiac ischemia-reperfusion injury in prediabetic rats

Mitochondria are extraordinarily dynamic organelles that have a variety of morphologies, the status of which are controlled by the opposing processes of fission and fusion. Our recent study shows that inhibition of excessive mitochondrial fission by Drp1 inhibitor (Mdivi-1) leads to a reduction in infarct size and left ventricular (LV) dysfunction following cardiac ischemia-reperfusion (I/R) injury in high fat-fed induced pre-diabetic rats. In the present study, we investigated the cardioprotective effects of a mitochondrial fusion promoter (M1) and a combined treatment (M1 and Mdivi-1) in pre-diabetic rats. Wistar rats were given a high-fat diet for 12 weeks to induce prediabetes. The rats then subjected to 30 min-coronary occlusions followed by reperfusion for 120 min. These rats were intravenously administered M1 (2 mg/kg) or M1 (2 mg/kg) combined with Mdivi-1 (1.2 mg/kg) prior to ischemia, during ischemia or at the onset of reperfusion. We showed that administration of M1 alone or in combination with Mdivi-1 prior to ischemia, during ischemia or at the onset of reperfusion all significantly attenuated cardiac mitochondrial ROS production, membrane depolarization, swelling and dynamic imbalance, leading to reduced arrhythmias and infarct size, resulting in improved LV function in pre-diabetic rats. In conclusion, the promotion of mitochondrial fusion at any time-points during cardiac I/R injury attenuated cardiac mitochondrial dysfunction and dynamic imbalance, leading to decreased infarct size and improved LV function in pre-diabetic rats.

Endocardial Gene Delivery Using NOGA Catheter System

NOGA/MyoStar system uses low magnetic fields and endomyocardial electrical parameters, allowing precise endomyocardial injections of therapeutic agents to ischemic yet viable myocardium which is most likely to respond to the treatment. Preclinical and clinical studies have shown that NOGA/MyoStar guided intramyocardial injections are safe, feasible and a minimally invasive way to deliver gene therapy to the heart. Here we describe how to perform electroanatomical mapping and injections to hibernating myocardium in the preclinical studies.

Cyclin D2 Overexpression Enhances the Efficacy of Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Myocardial Repair in a Swine Model of Myocardial Infarction

BACKGROUND

Human induced pluripotent stem cells with normal (wild-type) or upregulated (overexpressed) levels of CCND2 (cyclin D2) expression were differentiated into cardiomyocytes (CCND2^WTCMs or CCND2^OECMs, respectively) and injected into infarcted pig hearts.

METHODS

Acute myocardial infarction was induced by a 60-minute occlusion of the left anterior descending coronary artery. Immediately after reperfusion, CCND2^WTCMs or CCND2^OECMs (3×10⁷ cells each) or an equivalent volume of the delivery vehicle was injected around the infarct border zone area.

RESULTS

The number of the engrafted CCND2^OECMs exceeded that of the engrafted CCND2^WTCMs from 6- to 8-fold, rising from 1 week to 4 weeks after implantation. In contrast to the treatment with the CCND2^WTCMs or the delivery vehicle, the administration of CCND2^OECM was associated with significantly improved left ventricular function, as revealed by magnetic resonance imaging. This correlated with reduction of infarct size, fibrosis, ventricular hypertrophy, and cardiomyocyte apoptosis, and increase of vascular density and arterial density, as per histologic analysis of the treated hearts. Expression of cell proliferation markers (eg, Ki67, phosphorylated histone 3, and Aurora B kinase) was also significantly upregulated in the recipient cardiomyocytes from the CCND2^OECM-treated than from the CCND2^WTCM-treated pigs. The cell proliferation rate and the hypoxia tolerance measured in cultured human induced pluripotent stem cell cardiomyocytes were significantly greater after treatment with exosomes isolated from the CCND2^OECMs (CCND2^OEExos) than from the CCND2^WTCMs (CCND2^WTExos). As demonstrated by our study, CCND2^OEExos can also promote the proliferation activity of postnatal rat and adult mouse cardiomyocytes. A bulk miRNA sequencing analysis of CCND2^OEExos versus CCND2^WTExos identified 206 and 91 miRNAs that were significantly upregulated and downregulated, respectively. Gene ontology enrichment analysis identified significant differences in the expression profiles of miRNAs from various functional categories and pathways, including miRNAs implicated in cell-cycle checkpoints (G2/M and G1/S transitions), or the mechanism of cytokinesis.

CONCLUSIONS

We demonstrated that enhanced potency of CCND2^OECMs promoted myocyte proliferation in both grafts and recipient tissue in a large mammal acute myocardial infarction model. These results suggest that CCND2^OECMs transplantation may be a potential therapeutic strategy for the repair of infarcted hearts.

Interaction of the Joining Region in Junctophilin-2 With the L-Type Ca2+ Channel Is Pivotal for Cardiac Dyad Assembly and Intracellular Ca2+ Dynamics

RATIONALE

Ca2+-induced Ca2+ release (CICR) in normal hearts requires close approximation of L-type calcium channels (LTCCs) within the transverse tubules (T-tubules) and RyR (ryanodine receptors) within the junctional sarcoplasmic reticulum. CICR is disrupted in cardiac hypertrophy and heart failure, which is associated with loss of T-tubules and disruption of cardiac dyads. In these conditions, LTCCs are redistributed from the T-tubules to disrupt CICR. The molecular mechanism responsible for LTCCs recruitment to and from the T-tubules is not well known. JPH (junctophilin) 2 enables close association between T-tubules and the junctional sarcoplasmic reticulum to ensure efficient CICR. JPH2 has a so-called joining region that is located near domains that interact with T-tubular plasma membrane, where LTCCs are housed. The idea that this joining region directly interacts with LTCCs and contributes to LTCC recruitment to T-tubules is unknown.

OBJECTIVE

To determine if the joining region in JPH2 recruits LTCCs to T-tubules through direct molecular interaction in cardiomyocytes to enable efficient CICR.

METHODS AND RESULTS

Modified abundance of JPH2 and redistribution of LTCC were studied in left ventricular hypertrophy in vivo and in cultured adult feline and rat ventricular myocytes. Protein-protein interaction studies showed that the joining region in JPH2 interacts with LTCC-α1C subunit and causes LTCCs distribution to the dyads, where they colocalize with RyRs. A JPH2 with induced mutations in the joining region (mutPG1JPH2) caused T-tubule remodeling and dyad loss, showing that an interaction between LTCC and JPH2 is crucial for T-tubule stabilization. mutPG1JPH2 caused asynchronous Ca2+-release with impaired excitation-contraction coupling after β-adrenergic stimulation. The disturbed Ca2+ regulation in mutPG1JPH2 overexpressing myocytes caused calcium/calmodulin-dependent kinase II activation and altered myocyte bioenergetics.

CONCLUSIONS

The interaction between LTCC and the joining region in JPH2 facilitates dyad assembly and maintains normal CICR in cardiomyocytes.

The study of border zone formation in ischemic heart using electro-chemical coupled computational model

Myocardial infarction (MI) is the most common cause of a heart failure, which occurs due to myocardial ischemia leading to left ventricular (LV) remodeling. LV remodeling particularly occurs at the ischemic area and the region surrounds it, known as the border zone. The role of the border zone in initiating LV remodeling process urges the investigation on the correlation between early border zone changes and remodeling outcome. Thus, this study aims to simulate a preliminary conceptual work of the border zone formation and evolution during onset of MI and its effect towards early LV remodeling processes by incorporating the oxygen concentration effect on the electrophysiology of an idealized three-dimensional LV through electro-chemical coupled mathematical model. The simulation result shows that the region of border zone, represented by the distribution of electrical conductivities, keeps expanding over time. Based on this result, the border zone is also proposed to consist of three sub-regions, namely mildly, moderately, and seriously impaired conductivity regions, which each region categorized depending on its electrical conductivities. This division could be used as a biomarker for classification of reversible and irreversible myocardial injury and will help to identify the different risks for the survival of patient. Larger ischemic size and complete occlusion of the coronary artery can be associated with an increased risk of developing irreversible injury, in particular if the reperfusion treatment is delayed. Increased irreversible injury area can be related with cardiovascular events and will further deteriorate the LV function over time.

Secretome Analysis of Cardiomyocytes Identifies PCSK6 (Proprotein Convertase Subtilisin/Kexin Type 6) as a Novel Player in Cardiac Remodeling After Myocardial Infarction

BACKGROUND

Acute occlusion of a coronary artery results in swift tissue necrosis. Bordering areas of the infarcted myocardium can also experience impaired blood supply and reduced oxygen delivery, leading to altered metabolic and mechanical processes. Although transcriptional changes in hypoxic cardiomyocytes are well studied, little is known about the proteins that are actively secreted from these cells.

METHODS

We established a novel secretome analysis of cardiomyocytes by combining stable isotope labeling and click chemistry with subsequent mass spectrometry analysis. Further functional validation experiments included ELISA measurement of human samples, murine left anterior descending coronary artery ligation, and adeno-associated virus 9-mediated in vivo overexpression in mice.

RESULTS

The presented approach is feasible for analysis of the secretome of primary cardiomyocytes without serum starvation. A total of 1026 proteins were identified to be secreted within 24 hours, indicating a 5-fold increase in detection compared with former approaches. Among them, a variety of proteins have not yet been explored in the context of cardiovascular pathologies. One of the secreted factors most strongly upregulated upon hypoxia was PCSK6 (proprotein convertase subtilisin/kexin type 6). Validation experiments revealed an increase of PCSK6 on mRNA and protein level in hypoxic cardiomyocytes. PCSK6 expression was elevated in hearts of mice after 3 days of ligation of the left anterior descending artery, a finding confirmed by immunohistochemistry. ELISA measurements in human serum also indicate distinct kinetics for PCSK6 in patients with acute myocardial infarction, with a peak on postinfarction day 3. Transfer of PCSK6-depleted cardiomyocyte secretome resulted in decreased expression of collagen I and III in fibroblasts compared with control treated cells, and small interfering RNA-mediated knockdown of PCSK6 in cardiomyocytes impacted transforming growth factor-β activation and SMAD3 (mothers against decapentaplegic homolog 3) translocation in fibroblasts. An adeno-associated virus 9-mediated, cardiomyocyte-specific overexpression of PCSK6 in mice resulted in increased collagen expression and cardiac fibrosis, as well as decreased left ventricular function, after myocardial infarction.

CONCLUSIONS

A novel mass spectrometry-based approach allows investigation of the secretome of primary cardiomyocytes. Analysis of hypoxia-induced secretion led to the identification of PCSK6 as being crucially involved in cardiac remodeling after acute myocardial infarction.

Scar Formation with Decreased Cardiac Function Following Ischemia/Reperfusion Injury in 1 Month Old Swine

Studies in mice show a brief neonatal period of cardiac regeneration with minimal scar formation, but less is known about reparative mechanisms in large mammals. A transient cardiac injury approach (ischemia/reperfusion, IR) was used in weaned postnatal day (P)30 pigs to assess regenerative repair in young large mammals at a stage when cardiomyocyte (CM) mitotic activity is still detected. Female and male P30 pigs were subjected to cardiac ischemia (1 h) by occlusion of the left anterior descending artery followed by reperfusion, or to a sham operation. Following IR, myocardial damage occurred, with cardiac ejection fraction significantly decreased 2 h post-ischemia. No improvement or worsening of cardiac function to the 4 week study end-point was observed. Histology demonstrated CM cell cycling, detectable by phospho-histone H3 staining, at 2 months of age in multinucleated CMs in both sham-operated and IR pigs. Inflammation and regional scar formation in the epicardial region proximal to injury were observed 4 weeks post-IR. Thus, pigs subjected to cardiac IR at P30 show myocardial damage with a prolonged decrease in cardiac function, formation of a regional scar, and increased inflammation, but do not regenerate myocardium even in the presence of CM mitotic activity.

Myocardial viability of the peri-infarct region measured by T1 mapping post manganese-enhanced MRI correlates with LV dysfunction

BACKGROUND

Manganese-enhanced MRI (MEMRI) detects viable cardiomyocytes based on the intracellular manganese uptake via L-type calcium-channels. This study aimed to quantify myocardial viability based on manganese uptake by viable myocardium in the infarct core (IC), peri-infarct region (PIR) and remote myocardium (RM) using T1 mapping before and after MEMRI and assess their association with cardiac function and arrhythmogenesis.

METHODS

Fifteen female swine had a 60-minute balloon ischemia-reperfusion injury in the LAD. MRI (Signa 3T, GE Healthcare) and electrophysiological study (EPS) were performed 4 weeks later. MEMRI and delayed gadolinium-enhanced MRI (DEMRI) were acquired on LV short axis. The DEMRI positive total infarct area was subdivided into the regions of MEMRI-negative non-viable IC and MEMRI-positive viable PIR. T1 mapping was performed to evaluate native T1, post-MEMRI T1, and delta R1 (R1_post-R1_pre, where R1 equals 1/T1) of each territory. Their correlation with LV function and EPS data was assessed.

RESULTS

PIR was characterized by intermediate native T1 (1530.5 ± 75.2 ms) compared to IC (1634.7 ± 88.4 ms, p = 0.001) and RM (1406.4 ± 37.9 ms, p < 0.0001). Lower post-MEMRI T1 of PIR (1136.3 ± 99.6 ms) than IC (1262.6 ± 126.8 ms, p = 0.005) and higher delta R1 (0.23 ± 0.08 s^-1) of PIR than IC (0.18 ± 0.09 s^-1, p = 0.04) indicated higher myocardial manganese uptake of PIR compared to IC. Post-MEMRI T1 (r = -0.57, p = 0.02) and delta R1 (r = 0.51, p = 0.04) of PIR correlated significantly with LVEF.

CONCLUSIONS

PIR is characterized by higher manganese uptake compared to the infarct core. In the subacute phase post-IR, PIR viability measured by post-MEMRI T1 correlates with cardiac function.

Protein Kinase C Inhibition With Ruboxistaurin Increases Contractility and Reduces Heart Size in a Swine Model of Heart Failure With Reduced Ejection Fraction

Inotropic support is often required to stabilize the hemodynamics of patients with acute decompensated heart failure; while efficacious, it has a history of leading to lethal arrhythmias and/or exacerbating contractile and energetic insufficiencies. Novel therapeutics that can improve contractility independent of beta-adrenergic and protein kinase A-regulated signaling, should be therapeutically beneficial. This study demonstrates that acute protein kinase C-α/β inhibition, with ruboxistaurin at 3 months' post-myocardial infarction, significantly increases contractility and reduces the end-diastolic/end-systolic volumes, documenting beneficial remodeling. These data suggest that ruboxistaurin represents a potential novel therapeutic for heart failure patients, as a moderate inotrope or therapeutic, which leads to beneficial ventricular remodeling.

Cortical Bone Stem Cell Therapy Preserves Cardiac Structure and Function After Myocardial Infarction

RATIONALE

Cortical bone stem cells (CBSCs) have been shown to reduce ventricular remodeling and improve cardiac function in a murine myocardial infarction (MI) model. These effects were superior to other stem cell types that have been used in recent early-stage clinical trials. However, CBSC efficacy has not been tested in a preclinical large animal model using approaches that could be applied to patients.

OBJECTIVE

To determine whether post-MI transendocardial injection of allogeneic CBSCs reduces pathological structural and functional remodeling and prevents the development of heart failure in a swine MI model.

METHODS AND RESULTS

Female Göttingen swine underwent left anterior descending coronary artery occlusion, followed by reperfusion (ischemia-reperfusion MI). Animals received, in a randomized, blinded manner, 1:1 ratio, CBSCs (n=9; 2×10⁷ cells total) or placebo (vehicle; n=9) through NOGA-guided transendocardial injections. 5-ethynyl-2'deoxyuridine (EdU)-a thymidine analog-containing minipumps were inserted at the time of MI induction. At 72 hours (n=8), initial injury and cell retention were assessed. At 3 months post-MI, cardiac structure and function were evaluated by serial echocardiography and terminal invasive hemodynamics. CBSCs were present in the MI border zone and proliferating at 72 hours post-MI but had no effect on initial cardiac injury or structure. At 3 months, CBSC-treated hearts had significantly reduced scar size, smaller myocytes, and increased myocyte nuclear density. Noninvasive echocardiographic measurements showed that left ventricular volumes and ejection fraction were significantly more preserved in CBSC-treated hearts, and invasive hemodynamic measurements documented improved cardiac structure and functional reserve. The number of EdU⁺ cardiac myocytes was increased in CBSC- versus vehicle- treated animals.

CONCLUSIONS

CBSC administration into the MI border zone reduces pathological cardiac structural and functional remodeling and improves left ventricular functional reserve. These effects reduce those processes that can lead to heart failure with reduced ejection fraction.

Nuquantus: Machine learning software for the characterization and quantification of cell nuclei in complex immunofluorescent tissue images

Determination of fundamental mechanisms of disease often hinges on histopathology visualization and quantitative image analysis. Currently, the analysis of multi-channel fluorescence tissue images is primarily achieved by manual measurements of tissue cellular content and sub-cellular compartments. Since the current manual methodology for image analysis is a tedious and subjective approach, there is clearly a need for an automated analytical technique to process large-scale image datasets. Here, we introduce Nuquantus (Nuclei quantification utility software) - a novel machine learning-based analytical method, which identifies, quantifies and classifies nuclei based on cells of interest in composite fluorescent tissue images, in which cell borders are not visible. Nuquantus is an adaptive framework that learns the morphological attributes of intact tissue in the presence of anatomical variability and pathological processes. Nuquantus allowed us to robustly perform quantitative image analysis on remodeling cardiac tissue after myocardial infarction. Nuquantus reliably classifies cardiomyocyte versus non-cardiomyocyte nuclei and detects cell proliferation, as well as cell death in different cell classes. Broadly, Nuquantus provides innovative computerized methodology to analyze complex tissue images that significantly facilitates image analysis and minimizes human bias.

Rationale and design of the Percutaneous Stem Cell Injection Delivery Effects on Neomyogenesis in Dilated Cardiomyopathy (the POSEIDON-DCM study): a phase I/II, randomized pilot study of the comparative safety and efficacy of transendocardial injection of autologous mesenchymal stem cell vs. allogeneic mesenchymal stem cells in patients with non-ischemic dilated cardiomyopathy

While accumulating clinical trials have focused on the impact of cell therapy in patients with acute myocardial infarction (MI) and ischemic cardiomyopathy, there are fewer efforts to examine cell-based therapy in patients with non-ischemic cardiomyopathy (NICM). We hypothesized that cell therapy could have a similar impact in NICM. The POSEIDON-DCM trial is a phase I/II trial designed to address autologous vs. allogeneic bone marrow-derived mesenchymal stem cells (MSCs) in patients with NICM. In this study, cells will be administered transendocardially with the NOGA injection-catheter system to patients (n = 36) randomly allocated to two treatment groups: group 1 (n = 18 auto-human mesenchymal stem cells (hMSC)) and group 2 (n = 18 allo-hMSCs). The primary and secondary objectives are, respectively, to demonstrate the safety and efficacy of allo-hMSCS vs. auto-hMSCs in patients with NICM. This study will establish safety of transendocardial injection of stem cells (TESI), compare phenotypic outcomes, and offer promising advances in the field of cell-based therapy in patients with NICM.

Multimodality infarct identification for optimal image-guided intramyocardial cell injections

BACKGROUND

Intramyocardial cell injections in the context of cardiac regenerative therapy can currently be performed using electromechanical mapping (EMM) provided by the NOGA®XP catheter injection system. The gold standard technique to determine infarct size and location, however, is late gadolinium enhanced magnetic resonance imaging (LGE-MRI). In this article we describe a practical and accurate technique to co-register LGE-MRI and NOGA®XP datasets during the injection procedures to ultimately perform image-guided injections to the border zone of the infarct determined by LGE-MRI.

MATERIALS AND METHODS

LGE-MRI and EMM were obtained in three pigs with chronic myocardial infarction. MRI and EMM datasets were registered using the in-house developed 3D CartBox image registration toolbox consisting of three steps: 1) landmark registration, 2) surface registration, and 3) manual optimization. The apex and the coronary ostia were used as landmarks.

RESULTS

Image registration was successful in all datasets, and resulted in a mean registration error of 3.22 ± 1.86 mm between the MRI surface mesh and EMM points. Visual assessment revealed that the locations and the transmural extent of the infarctions measured by LGE-MRI only partly overlap with the infarct areas identified by the EMM parameters.

CONCLUSIONS

The 3D CartBox image registration toolbox enables registration of EMM on pre-procedurally acquired MRI during the catheter injection procedure. This allows the operator to perform real-time image-guided cell injections into the border zone of the infarct as assessed by LGE-MRI. The 3D CartBox thereby enables, for the first time, standardisation of the injection location for cardiac regenerative therapy.

Development of a closed-artery catheter-based myocardial infarction in pigs using sponge and lidocaine hydrochloride infusion to prevent irreversible ventricular fibrillation

The objectives of this study were to develop a robust, homogeneous, viable and inexpensive model of closed‐artery catheter‐based model of myocardial infarction (MI) in pigs without major cardiac dysfunction. Suitable animal models that mimic human cardiovascular conditions are of paramount importance to understand the effects of novel therapeutic strategies to improve tissue perfusion and prevent cardiac deterioration post‐MI. Pigs (N = 21, BW = 17 ± 1 kg) receiving continuous iv lidocaine hydrochloride were subjected to percutaneous intracoronary implant of foam sponge into the proximal left circumflex coronary artery. Intraprocedure mortality was 23.8%. ST segment elevation and increased serum Troponin T and CK‐MB were documented in all animals. Thirty days after occlusion, echocardiography (95% IC [9.3–12.4%]) and anatomopathological (95% CI [9.3–12.6%]) analyses confirmed a significant and reproducible MI. Taken together, we provide evidence for a suitable closed‐artery catheter‐based method to produce MI in pigs accompanied by tissue hypoperfusion and absence of overt heart failure.

We provide evidence that an inexpensive and easily available material can be used to produce a robust and homogenous percutaneous closed‐artery model of MI in pigs, when associated with lidocaine hydrochloride use. Thirty days after occlusion, anatomopathological (95% IC [9.3–12.6%]) analyses confirmed a significant and reproducible MI accompanied by hypoperfusion and absence of overt heart failure.

Bone-derived stem cells repair the heart after myocardial infarction through transdifferentiation and paracrine signaling mechanisms

RATIONALE

Autologous bone marrow-derived or cardiac-derived stem cell therapy for heart disease has demonstrated safety and efficacy in clinical trials, but functional improvements have been limited. Finding the optimal stem cell type best suited for cardiac regeneration is the key toward improving clinical outcomes.

OBJECTIVE

To determine the mechanism by which novel bone-derived stem cells support the injured heart.

METHODS AND RESULTS

Cortical bone-derived stem cells (CBSCs) and cardiac-derived stem cells were isolated from enhanced green fluorescent protein (EGFP+) transgenic mice and were shown to express c-kit and Sca-1 as well as 8 paracrine factors involved in cardioprotection, angiogenesis, and stem cell function. Wild-type C57BL/6 mice underwent sham operation (n=21) or myocardial infarction with injection of CBSCs (n=67), cardiac-derived stem cells (n=36), or saline (n=60). Cardiac function was monitored using echocardiography. Only 2/8 paracrine factors were detected in EGFP+ CBSCs in vivo (basic fibroblast growth factor and vascular endothelial growth factor), and this expression was associated with increased neovascularization of the infarct border zone. CBSC therapy improved survival, cardiac function, regional strain, attenuated remodeling, and decreased infarct size relative to cardiac-derived stem cells- or saline-treated myocardial infarction controls. By 6 weeks, EGFP+ cardiomyocytes, vascular smooth muscle, and endothelial cells could be identified in CBSC-treated, but not in cardiac-derived stem cells-treated, animals. EGFP+ CBSC-derived isolated myocytes were smaller and more frequently mononucleated, but were functionally indistinguishable from EGFP- myocytes.

CONCLUSIONS

CBSCs improve survival, cardiac function, and attenuate remodeling through the following 2 mechanisms: (1) secretion of proangiogenic factors that stimulate endogenous neovascularization, and (2) differentiation into functional adult myocytes and vascular cells.