Some of the protective effects of MSCs on infarct repair are mediated by macrophages, which are essential for early healing and repair. Thus, targeting macrophages could be a novel strategy to improve infarct healing and repair.

BackgroundIschemic cardiac damage is associated with upregulation of cardiac pro-inflammatory cytokines, as well as invasion of lymphocytes into the heart. Regulatory T cells (Tregs) are known to exert a suppressive effect on several immune cell types. We sought to determine whether the Treg pool is influenced by myocardial damage and whether Tregs transfer and deletion affect cardiac remodeling.Methods and ResultsThe number and functional suppressive activity of Tregs were assayed in mice subjected to experimental myocardial infarction. The numbers of splenocyte-derived Tregs in the ischemic mice were significantly higher after the injury than in the controls, and their suppressive properties were significantly compromised. Compared with PBS, adoptive Treg transfer to mice with experimental infarction reduced infarct size and improved LV remodeling and functional performance by echocardiography. Treg deletion with blocking anti-CD25 antibodies did not influence infarct size or echocardiographic features of cardiac remodeling.ConclusionTreg numbers are increased whereas their function is compromised in mice with that underwent experimental infarction. Transfer of exogeneous Tregs results in attenuation of myocardial remodeling whereas their ablation has no effect. Thus, Tregs may serve as interesting potential interventional targets for attenuating left ventricular remodeling.

BackgroundHuman mesenchymal stromal cells (hMSCs) from adipose cardiac tissue have attracted considerable interest in regard to cell‐based therapies. We aimed to test the hypothesis that hMSCs from the heart and epicardial fat would be better cells for infarct repair.Methods and ResultsWe isolated and grew hMSCs from patients with ischemic heart disease from 4 locations: epicardial fat, pericardial fat, subcutaneous fat, and the right atrium. Significantly, hMSCs from the right atrium and epicardial fat secreted the highest amounts of trophic and inflammatory cytokines, while hMSCs from pericardial and subcutaneous fat secreted the lowest. Relative expression of inflammation‐ and fibrosis‐related genes was considerably higher in hMSCs from the right atrium and epicardial fat than in subcutaneous fat hMSCs. To determine the functional effects of hMSCs, we allocated rats to hMSC transplantation 7 days after myocardial infarction. Atrial hMSCs induced greatest infarct vascularization as well as highest inflammation score 27 days after transplantation. Surprisingly, cardiac dysfunction was worst after transplantation of hMSCs from atrium and epicardial fat and minimal after transplantation of hMSCs from subcutaneous fat. These findings were confirmed by using hMSC transplantation in immunocompromised mice after myocardial infarction. Notably, there was a correlation between tumor necrosis factor‐α secretion from hMSCs and posttransplantation left ventricular remodeling and dysfunction.ConclusionsBecause of their proinflammatory properties, hMSCs from the right atrium and epicardial fat of cardiac patients could impair heart function after myocardial infarction. Our findings might be relevant to autologous mesenchymal stromal cell therapy and development and progression of ischemic heart disease.

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Ligand-receptor mediated targeting may affect differently the performance of supramolecular drug carriers depending on the nature of the nanocarrier. In this study, we compare the selectivity, safety and activity of doxorubicin (Dox) entrapped in liposomes versus Dox conjugated to polymeric nanocarriers in the presence or absence of a folic acid (FA)-targeting ligand to cancer cells that overexpress the folate receptor (FR). Two pullulan (Pull)-based conjugates of Dox were synthesized, (FA-PEG)-Pull-(Cyst-Dox) and (NH2-PEG)-Pull-(Cyst-Dox). The other delivery systems are Dox loaded PEGylated liposomes (PLD, Doxil®) and the FR-targeted version (PLD-FA) obtained by ligand post-insertion into the commercial formulation. Both receptor-targeted drug delivery systems (DDS) were shown to interact in vitro specifically with cells via the folate ligand. Treatment of FR-overexpressing human cervical carcinoma KB tumor-bearing mice with three-weekly injections resulted in slightly enhanced anticancer activity of PLD-FA compared to PLD and no activity for both pullulan-based conjugates. When the DDS were administered intravenously every other day, the folated-Pull conjugate and the non-folated-Pull conjugate displayed similar and low antitumor activity as free Dox. At this dosing regimen, the liposome-based formulations displayed enhanced antitumor activity with an advantage to the non-folated liposome. However, both liposomal formulations suffered from toxicity that was reversible following treatment discontinuation. Using a daily dosing schedule, with higher cumulative dose, the folated-Pull conjugate strongly inhibited tumor growth while free Dox was toxic at this regimen. For polymeric constructs, increasing dose intensity and cumulative dose strongly affects the therapeutic index and reveals a major therapeutic advantage for the FR-targeted formulation. All DDS were able to abrogate doxorubicin-induced cardiotoxicity. This study constitutes the first side-by-side comparison of two receptor-targeted ligand-bearing systems, polymer therapeutics versus nanoparticulate systems, evaluated in the same mouse tumor model at several dosing regimens.

Ischaemic damage is associated with up-regulation of pro-inflammatory cytokines, as well as invasion of leucocytes and lymphocytes to the injured muscle. Regulatory T cells (Tregs) exert suppressive effects on several immune and nonimmune cellular elements. We hypothesized that adoptive Treg cell transfer and depletion will influence re-establishment of flow in the hindlimb ischaemia model, and that this effect would be mediated by the cytokine interleukin (IL)-10. Methods and results To study the functional role of Tregs in hindlimb ischaemia, we either adoptively transferred Tregs or functionally blocked Tregs by antibodies to CD25. Initially, we showed that the number and function of Tregs is altered after the induction of ischaemia. Treg ablation resulted in reduced blood flow by laser Doppler at Day 7 that became more robust at Day 14. Adoptive Treg transfer led to a significant improvement of flow in the ligated limb. Treg-mediated improvement in flow was abolished by employing blocking anti-IL-10 antibodies. Conclusions These results show that Tregs play an important role in processes that control flow re-establishment after inducible hindlimb ischaemia, and that IL-10 plays a requisite role mediating these effects.

Background Myocarditis is a life-threatening heart disease characterized by myocardial inflammation, necrosis and chronic fibrosis. While mast cell inhibition has been suggested to prevents fibrosis in rat myocarditis, little is known about its effectiveness in attenuating cardiac remodeling and dysfunction in myocarditis. Thus, we sought to test the hypothesis that mast cell inhibition will attenuate the inflammatory reaction and associated left ventricular (LV) remodeling and dysfunction after fulminant autoimmune myocarditis. Methods and Results To induce experimental autoimmune myocarditis, we immunized 30 rats with porcine cardiac myosin twice at a 7-day interval. On day 8 animals were randomized into treatment either with an intraperitoneal (IP) injection of 25mg/kg of cromolyn sodium (n=13), or an equivalent volume (~0.5ml IP) of normal saline (n=11). All animals were scanned by serial echocardiography studies before treatment (baseline echocardiogram) and after 20 days of cromolyn sodium (28 days after immunization). Furthermore, serial cardiac magnetic resonance was performed in a subgroup of 12 animals. After 20 days of treatment (28 days from first immunization), hearts were harvested for histopathological analysis. By echocardiography, cromolyn sodium prevented LV dilatation and attenuated LV dysfunction, compared with controls. Postmortem analysis of hearts showed that cromolyn sodium reduced myocardial fibrosis, as well as the number and size of cardiac mast cells in the inflamed myocardium, compared with controls. Conclusions Our study suggests that mast cell inhibition with cromolyn sodium attenuates adverse LV remodeling and dysfunction in myocarditis. This mechanism-based therapy is clinically relevant and could improve the outcome of patients at risk for inflammatory cardiomyopathy and heart failure.

AimsThe aim of this study was to assess the use of a 3 T clinical cardiac magnetic resonance (CMR) scanner to detect injury to the heart in experimental autoimmune myocarditis (EAM). Methods and resultsThe use of 3 T CMR for the detection of cardiac injury was assessed in EAM (n ¼ 55) and control (n ¼ 10) male Lewis rats. Animals were evaluated with serial CMR imaging studies, using a 3 T scanner, and with 2D echocardiography before, and at 2 and 5 weeks after EAM induction. By CMR, regional wall motion abnormalities were noted in seven out of eight rats with myocarditis 5 weeks after induction. Subsequently, the rats developed significant left ventricular (LV) dilatation, wall thickening, and pericardial effusion. Average LV systolic and diastolic volumes increased from 131 + 10 to 257 + 20 mL (P ¼ 0.0008), and from 309 + 14 to 412 + 24 mL (P , 0.0001), and ejection fraction markedly deteriorated (from 58 + 2 to 37 + 5%; P ¼ 0.0003). Areas of fibrosis were located by late gadolinium enhancement (LGE) CMR at the subepicardium, mainly within the anterior, lateral, and inferior walls. The extent and location of LGE were highly correlated (r ¼ 0.94; P , 0.0001) with areas of myocardial fibrosis by histopathology, with 85% sensitivity and 86% specificity. ConclusionA clinical 3 T CMR scanner enables accurate detection, quantification, and monitoring of experimental myocarditis in rats, and could be used for translational research to study the pathophysiology of the disease and evaluate novel therapies.--