Granulocyte colony-stimulating factor treatment enhances the efficacy of cellular cardiomyoplasty with transplantation of embryonic stem cell-derived cardiomyocytes in infarcted myocardium

Assessment of electromechanically stimulated bone marrow stem cells seeded acellular cardiac patch in a rat myocardial infarct model

In this study, we evaluated cardiomyogenic differentiation of electromechanically stimulated rat bone marrow-derived stem cells (rt-BMSCs) on an acellular bovine pericardium (aBP) and we looked at the functioning of this engineered patch in a rat myocardial infarct (MI) model. aBP was prepared using a detergent-based decellularization procedure followed by rt-BMSCs seeding, and electrical, mechanical, or electromechanical stimulations (3 millisecond pulses of 5 V cm^-1at 1 Hz, 5% stretching) to enhance cardiomyogenic differentiation. Furthermore, the electromechanically stimulated patch was applied to the MI region over 3 weeks. After this period, the retrieved patch and infarct region were evaluated for the presence of calcification, inflammatory reaction (CD68), patch to host tissue cell migration, and structural sarcomere protein expressions. In conjunction with any sign of calcification, a higher number of BrdU-labelled cells, and a low level of CD68 positive cells were observed in the infarct region under electromechanically stimulated conditions compared with static conditions. More importantly, MHC, SAC, Troponin T, and N-cad positive cells were observed in both infarct region, and retrieved engineered patch after 3 weeks. In a clear alignment with other results, our developed acellular patch promoted the expression of cardiomyogenic differentiation factors under electromechanical stimulation. Our engineered patch showed a successful integration with the host tissue followed by the cell migration to the infarct region.

Guidelines for experimental models of myocardial ischemia and infarction

Myocardial infarction is a prevalent major cardiovascular event that arises from myocardial ischemia with or without reperfusion, and basic and translational research is needed to better understand its underlying mechanisms and consequences for cardiac structure and function. Ischemia underlies a broad range of clinical scenarios ranging from angina to hibernation to permanent occlusion, and while reperfusion is mandatory for salvage from ischemic injury, reperfusion also inflicts injury on its own. In this consensus statement, we present recommendations for animal models of myocardial ischemia and infarction. With increasing awareness of the need for rigor and reproducibility in designing and performing scientific research to ensure validation of results, the goal of this review is to provide best practice information regarding myocardial ischemia-reperfusion and infarction models.

Listen to this article’s corresponding podcast at ajpheart.podbean.com/e/guidelines-for-experimental-models-of-myocardial-ischemia-and-infarction/.

Biomimetic electrical stimulation induces rat bone marrow mesenchymal stem cells to differentiate into cardiomyocyte-like cells via TGF-beta 1 in vitro

Electrical conductance is one of the factors of the microenvironment of cardiomyocytes, and electrical stimulation (ES) has been shown to modulate the differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) toward a cardiomyogenic fate. Transforming growth factor-beta 1 (TGF-β1) stimulates the cardiomyogenic marker expression in BMSCs. Herein, we promoted the differentiation of BMSCs into cardiomyocyte-like cells using ES to confirm if TGF-β1 mediates this event in vitro. ES increased protein levels of TGF-β1 in BMSCs, and this effect was better than that observed with 5-azacytidine (5-Aza). The effect of ES on promoting cardiomyogenic marker expression in BMSCs was enhanced by TGF-β1. Furthermore, the protein expression levels of Connexin43 (Cx43) and Alpha-actinin 2 (ACTN2) induced by ES in BMSCs were significantly decreased by pirfenidone. These results show that ES promotes cardiomyocyte-like cells differentiation in rat BMSCs and is possibly mediated by TGF-β1 in vitro.

Beneficial effects of schisandrin B on the cardiac function in mice model of myocardial infarction

The fruit of Schisandra chinensis has been used in the traditional Chinese medicine for thousands of years. Accumulating evidence suggests that Schisandrin B (Sch B) has cardioprotection effect on myocardial ischemia invitro. However, it is unclear whether Sch B has beneficial effects on continuous myocardial ischemia in vivo. The aim of the present study was to investigate whether Sch B could improve cardiac function and attenuate myocardial remodeling after myocardial infarction (MI) in mice. Mice model of MI was established by permanent ligation of the left anterior descending (LAD) coronary artery. Then the MI mice were randomly treated with Sch B or vehicle alone. After treatment for 3 weeks, Sch B could increase survival rate, improve heart function and decrease infarct size compared with vehicle. Moreover, Sch B could down-regulate some inflammatory cytokines, activate eNOS pathway, inhibit cell apoptosis, and enhance cell proliferation. Further in vitro study on H9c2 cells showed similar effects of Sch B on prevention of hypoxia-induced inflammation and cell apoptosis. Taken together, our results demonstrate that Sch B can reduce inflammation, inhibit apoptosis, and improve cardiac function after ischemic injury. It represents a potential novel therapeutic approach for treatment of ischemic heart disease.

Current status of induced pluripotent stem cells in cardiac tissue regeneration and engineering

Myocardial infarction (MI) is associated with damage to the myocardium which results in a great loss of functional cardiomyocytes. As one of the most terminally differentiated organs, the endogenous regenerative potentials of adult hearts are extremely limited and insufficient to compensate for the myocardial loss occurring after MI. Consequentially, exogenous regenerative strategies, especially cell replacement therapy, have emerged and attracted increasing more attention in the field of cardiac tissue regeneration. A renewable source of seeding cells is therefore one of the most important subject in the field. Induced pluripotent stem cells (iPSCs), embryonic stem cell (ESC)-like cells that are derived from somatic cells by reprogramming, represent a promising candidate due to their high potentials for self-renewal, proliferation, differentiation and more importantly, they provide an invaluable method of deriving patient-specific pluripotent stem cells. Therefore, iPSC-based cardiac tissue regeneration and engineering has been extensively investigated in recent years. This review will discuss the achievements and current status in this field, including development of iPSC derivation, in vitro strategies for cardiac generation from iPSCs, cardiac application of iPSCs, challenges confronted at present as well as perspective in the future.

Cardiac applications for human pluripotent stem cells

Human embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs) can self-renew indefinitely, while maintaining the capacity to differentiate into useful somatic cell types, including cardiomyocytes. As such, these stem cell types represent an essentially inexhaustible source of committed human cardiomyocytes of potential use in cell-based cardiac therapies, high-throughput screening and safety testing of new drugs, and modeling human heart development. These stem cell-derived cardiomyocytes have an unambiguous cardiac phenotype and proliferate robustly both in vitro and in vivo. Recent transplantation studies in preclinical models have provided exciting proof-of-principle for their use in infarct repair and in the formation of a "biological pacemaker". While these successes give reason for cautious optimism, major challenges remain to the successful application of hESCs (or hiPSCs) to cardiac repair, including the need for preparations of high cardiac purity, improved methods of delivery, and approaches to overcome immune rejection and other causes of graft cell death. In this review, we describe the phenotype of hESC- and hiPSC-derived cardiomyocytes, the state of preclinical transplantation studies with these cells, and potential approaches to overcome the aforementioned hurdles.

In vitro cardiomyogenic differentiation of adipose-derived stromal cells using transforming growth factor-beta1

Transplanting stem cells differentiated towards a cardiac lineage can regenerate cardiac muscle tissues to treat myocardial infarction. In this study, we tested the hypothesis that transforming growth factor-beta1 (TGF-beta1) induces cardiomyogenic differentiation of adipose- derived stromal cells (ADSCs) in vitro. Rat ADSCs were cultured with TGF-beta1 (10 ng ml(-1)) for 2 weeks in vitro. ADSCs cultured without TGF-beta1 served as a control. The mRNA expression of cardiac-specific gene was induced by TGF-beta1, while the control culture did not show cardiac-specific gene expression. Immunocytochemical analyses showed that a small fraction of ADSCs cultured with TGF-beta1 for 2 weeks stained positively for cardiac myosin heavy chain (MHC) and alpha-sarcomeric actin. Flow cytometric analyses showed that the proportion of cells expressing cardiac MHC increased with TGF-beta1. However, no mesenchymal differentiation (e.g., osteogenic and adipogenic differentiation) was detected other than cardiomyogenic differentiation. These results showed that TGF-beta1 induce ADSC cardiomyogenic differentiation in vitro, which could be useful for myocardial infarction stem cell therapy.

Mobilization of mesenchymal stem cells by granulocyte colony-stimulating factor in rats with acute myocardial infarction

PURPOSE

Intravenous delivery of mesenchymal stem cells (MSCs), a noninvasive strategy for myocardial repair after acute myocardial infarction (MI), is limited by the low percentage of MSCs migration to the heart. The purpose of this study was to test whether granulocyte colony-stimulating factor (G-CSF) would enhance the colonization of intravenously infused MSCs in damaged heart in a rat model of acute MI.

METHODS

After induction of anterior MI, Sprague-Dawley rats were randomized to receive: (1) saline (n=9); (2) MSCs (n=15); and (3) MSCs plus G-CSF (50 microg/kg/day for 5 consecutive days, n=13).

RESULTS

Flow cytometry revealed that G-CSF slightly increased surface CXCR4 expression on MSCs in vitro. After completion of G-CSF administration, MSCs showed a significantly lower colonization in bone marrow and a trend toward higher localization in the infarcted myocardium. At 3 months, vessel density in the infarct region of heart was significantly increased in MSCs group and trended to increase in MSCs+G-CSF group. However, echocardiographic and hemodynamic parameters, including left ventricular (LV) end-diastolic diameters, ejection fraction, and +/-dP/dtmax, were not statistically different. Morphological analysis showed that infarct size and collagen content were similar in the three groups. Immunohistochemistry revealed that the combined therapy accelerated endothelial recovery of the blood vessels in the ischemic myocardium. However, myocardial regeneration resulting from MSCs differentiation was not observed.

CONCLUSIONS

G-CSF enhanced the migration of systemically delivered MSCs from bone marrow to infarcted heart. However, the beneficial effect of this kind of migration is limited, as cardiac function did not improve.

Combined therapy with human cord blood cell transplantation and basic fibroblast growth factor delivery for treatment of myocardial infarction

BACKGROUND

Transplanting cord blood-derived cells has been shown to augment neovascularization in ischaemic tissue.

AIM

To test whether sustained delivery of basic fibroblast growth factor (bFGF) enhances the efficacy of angiogenic cord blood mononuclear cell (CBMNC) transplantation therapy in treating myocardial infarction.

METHODS

Three weeks after myocardial infarction, Sprague-Dawley rats were randomised to either injection of medium only (control), CBMNC transplantation, sustained bFGF delivery, or combined CBMNC transplantation and sustained bFGF delivery. Six weeks after treatment, tissue formation, neovascularization, and apoptotic activity in the infarct regions were evaluated by histology and immunohistochemistry. Left ventricular (LV) dimensions and function were evaluated by magnetic resonance imaging.

RESULTS

Combined bFGF delivery and CBMNC transplantation significantly enhanced neovascularization in the ischaemic myocardium, as compared with either therapy alone. The enhanced neovascularization was likely due to increased VEGF and bFGF expression. The combined therapy also exhibited a reduced infarct area and apoptosis in the ischaemic myocardium, as compared with either individual therapy. The combined therapy did not attenuate LV dilation or increase ejection fraction significantly over either individual therapy.

CONCLUSION

This study demonstrates that sustained bFGF delivery enhances the angiogenic efficacy of CBMNC transplantation in rat myocardial infarction models.

Stem Cells and the Regeneration of the Aging Cardiovascular System

It is well established that cardiovascular repair mechanisms become progressively impaired with age and that advanced age is itself a significant risk factor for cardiovascular disease. Although therapeutic developments have improved the prognosis for those with cardiovascular disease, mortality rates have nevertheless remained virtually unchanged in the last twenty years. Clearly, there is a need for alternative strategies for the treatment of cardiovascular disease. In recent years, the idea that the heart is capable of regeneration has raised the possibility that cell-based therapies may provide such an alternative to conventional treatments. Cells that have the potential to generate cardiomyocytes and vascular cells have been identified in both the adult heart and peripheral tissues, and in vivo experiments suggest that these cardiovascular stem cells and cardiovascular progenitor cells, including endothelial progenitor cells, are capable of replacing damaged myocardium and vascular tissues. Despite these findings, the endogenous actions of cardiovascular stem cells and cardiovascular progenitor cells appear to be insufficient to protect against cardiovascular disease in older individuals. Because recent evidence suggests that cardiovascular stem cells and cardiovascular progenitor cells are subject to age-associated changes that impair their function, these changes may contribute to the dysregulation of endogenous cardiovascular repair mechanisms in the aging heart and vasculature. Here we present the evidence for the impact of aging on cardiovascular stem cell/cardiovascular progenitor cell function and its potential importance in the increased severity of cardiovascular pathophysiology observed in the geriatric population.