The potential of stem cells in the treatment of cardiovascular diseases

A 3D Mathematical Model of Coupled Stem Cell-Nutrient Dynamics in Myocardial Regeneration Therapy

Stem cell therapy is a promising treatment for the regeneration of myocardial tissue injured by an ischemic event. Mathematical modeling of myocardial regeneration via stem cell therapy is a challenging task, since the mechanisms underlying the processes involved in the treatment are not yet fully understood. Many aspects must be accounted for, such as the spread of stem cells and nutrients, chemoattraction, cell proliferation, stages of cell maturation, differentiation, angiogenesis, stochastic effects, just to name a few. In this paper we propose a 3D mathematical model with a free boundary that aims to provide a qualitative description of some main aspects of the stem cell regenerative therapy in a simplified scenario. The paper mainly focuses on the description of the shrinking of the necrotic core during treatment. The stem cell and nutrients dynamics are described through coupled reaction-diffusion problems. Proliferation, chemoattraction, tissue regeneration and nutrient consumption are included in the model.

Isolation Methods for Human CD34 Subsets Using Fluorescent and Magnetic Activated Cell Sorting: an In Vivo Comparative Study

INTRODUCTION

Acute myocardial infarction (AMI) and resulting cardiac damage and heart failure are leading causes of morbidity and mortality worldwide. Multiple studies have examined the utility of CD34⁺ cells for the treatment of acute and ischemic heart disease. However, the optimal strategy to enrich CD34 cells from clinical sources is not known. We examined the efficacy of fluorescence activated cell sorting (FACS) and magnetic beads cell sorting (MACS) methods for CD34 cell isolation from mobilized human mononuclear peripheral blood cells (mhPBMNCs).

METHODS

mhPBCs were processed following acquisition using FACS or MACS according to clinically established protocols. Cell viability, CD34 cell purity and characterization of surface marker expression were assessed using a flow cytometer. For in vivo characterization of cardiac repair, we conducted LAD ligation surgery on 8-10 weeks female NOD/SCID mice followed by intramyocardial transplantation of unselected mhPBMNCs, FACS or MACS enriched CD34⁺ cells.

RESULTS

Both MACS and FACS isolation methods achieved high purity rates, viability, and enrichment of CD34⁺ cells. In vivo studies following myocardial infarction demonstrated retention of CD34⁺ in the peri-infarct region for up to 30 days after transplantation. Retained CD34⁺ cells were associated with enhanced angiogenesis and reduced inflammation compared to unselected mhPBMNCs or PBS treatment arms. Cardiac scar and fibrosis as assessed by immunohistochemistry were reduced in FACS and MACS CD34⁺ treatment groups. Finally, reduced scar and augmented angiogenesis resulted in improved cardiac functional recovery, both on the global and regional function and remodeling assessments by echocardiography.

CONCLUSION

Cell based therapy using enriched CD34⁺ cells sorted by FACS or MACS result in better cardiac recovery after ischemic injury compared to unselected mhPBMNCs. Both enrichment techniques offer excellent recovery and purity and can be equally used for clinical applications.

Increased Myocardial Retention of Mesenchymal Stem Cells Post-MI by Pre-Conditioning Exercise Training

Stem cell (SC) therapy is a promising approach to improve post-myocardial infarction (MI) cardiac remodeling, but the proinflammatory microenvironment may lead to SC loss and, therefore, may have a negative impact on therapy. It appears that exercise training (ET) improves myocardial microenvironment for SC transplantation. Therefore, we tested the effect of ET on post-infarction retention of adipose-derived SCs (ADSCs) and its combined effects on the inflammatory microenvironment. Fischer-344 female rats were randomized to one of the following groups: Sham; sedentary coronary occlusion who did not receive ADSCs (sMI); sedentary coronary occlusion who received ADSCs; exercise coronary occlusion who received ADSCs. Rats were trained nine weeks prior to MI, followed by ADSCs transplantation. The MI led to left ventricle (LV) dilation and dysfunction, myocardial hypertrophy and fibrosis, and increased proinflammatory profile compared to Sham rats. Conversely, ADSCs transplanted rats exhibited, better morphological and functional LV parameters; inhibition of myocardial hypertrophy and fibrosis; and attenuation of proinflammatory cytokines (interleukins 1β and 10, tumor necrosis factor α, and transforming growth factor β) in the myocardium compared to sMI rats. Interestingly, ET enhanced the effect of ADSCs on interleukin 10 expression. There was a correlation between cytokine expression and myocardial ADSCs retention. The. ET enhanced the beneficial effects of ADSCs in infarcted myocardium, which was associated with higher ADSCs retention. These findings highlight the importance of ET in myocardial retention of ADSCs and attenuation of cardiac remodeling post-infarction. Cytokine analysis suggests improvement in ET-linked myocardial microenvironment based on its anti-inflammatory action.

The Impact of CRISPR/Cas9 Technology on Cardiac Research: From Disease Modelling to Therapeutic Approaches

Genome-editing technology has emerged as a powerful method that enables the generation of genetically modified cells and organisms necessary to elucidate gene function and mechanisms of human diseases. The clustered regularly interspaced short palindromic repeats- (CRISPR-) associated 9 (Cas9) system has rapidly become one of the most popular approaches for genome editing in basic biomedical research over recent years because of its simplicity and adaptability. CRISPR/Cas9 genome editing has been used to correct DNA mutations ranging from a single base pair to large deletions in both in vitro and in vivo model systems. CRISPR/Cas9 has been used to increase the understanding of many aspects of cardiovascular disorders, including lipid metabolism, electrophysiology and genetic inheritance. The CRISPR/Cas9 technology has been proven to be effective in creating gene knockout (KO) or knockin in human cells and is particularly useful for editing induced pluripotent stem cells (iPSCs). Despite these progresses, some biological, technical, and ethical issues are limiting the therapeutic potential of genome editing in cardiovascular diseases. This review will focus on various applications of CRISPR/Cas9 genome editing in the cardiovascular field, for both disease research and the prospect of in vivo genome-editing therapies in the future.

Insulin Cannot Induce Adipogenic Differentiation in Primary Cardiac Cultures

Cardiac tissue contains a heterogeneous population of cardiomyocytes and nonmyocyte population especially fibroblasts. Fibroblast differentiation into adipogenic lineage is important for fat accumulation around the heart which is important in cardiac pathology. The differentiation in fibroblast has been observed both spontaneously and due to increased insulin stimulation. The present study aims to observe the effect of insulin in adipogenic differentiation of cardiac cells present in primary murine cardiomyocyte cultures. Oil Red O (ORO) staining has been used for observing the lipid accumulations formed due to adipogenic differentiation in murine cardiomyocyte cultures. The accumulated lipids were quantified by ORO assay and normalized using protein estimation. The lipid accumulation in cardiac cultures did not increase in presence of insulin. However, addition of other growth factors like insulin-like growth factor 1 and epidermal growth factor promoted adipogenic differentiation even in the presence of insulin and other inhibitory molecules such as vitamins. Lipid accumulation also increased in cells grown in media without insulin after an initial exposure to insulin-containing growth media. The current study adds to the existing knowledge that the insulin by itself cannot induce adipogenic induction in the cardiac cultures. The data have significance in the understanding of cardiovascular health especially in diabetic patients.

Therapeutic use of stem cells for cardiovascular disease

Stem cell treatments are a desirable therapeutic option to regenerate myocardium and improve cardiac function after myocardial infarction. Several different types of cells have been explored, each with their own benefits and limitations. Induced pluripotent stem cells possess an embryonic-like state and therefore have a high proliferative capacity, but they also pose a risk of teratoma formation. Mesenchymal stem cells have been investigated from both bone marrow and adipose tissue. Their immunomodulatory characteristics may permit the use of allogeneic cells as universal donor cells in the future. Lastly, studies have consistently shown that cardiac stem cells are better able to express markers of cardiogenesis compared to other cell types, as well improve cardiac function. The ideal source of stem cells depends on multiple factors such as the ease of extraction/isolation, effectiveness of engraftment, ability to differentiate into cardiac lineages and effect on cardiac function. Although multiple studies highlight the benefits and limitations of each cell type and reinforce the successful potential use of these cells to regenerate damaged myocardium, more studies are needed to directly compare cells from various sources. It is interesting to note that research using stem cell therapies is also expanding to treat other cardiovascular diseases including non-ischemic cardiomyopathies.

Adipose-Derived Mesenchymal Stem Cells Ameliorate Lipid Metabolic Disturbance in Mice

: Adipose-derived mesenchymal stem cells (AD-MSCs) have been shown to ameliorate hyperglycemia in diabetic animals and individuals. However, little is known about whether AD-MSCs affect lipid metabolism. Here we have demonstrated for the first time that AD-MSC infusion can significantly suppress the increase in body weight and remarkably improve dyslipidemia in db/db obese mice and diet-induced obesity mice. Induction of white fat tissue "browning" and activation of adenosine monophosphate-activated protein kinase and its downstream hormone-sensitive lipase in adipose tissue contribute to the antiobesity and lipid-lowering effects. Thus, AD-MSC infusion holds great therapeutic potential for dyslipidemia and associated cardiovascular diseases.

SIGNIFICANCE

Mesenchymal stem cells (MSCs) are considered one of the most promising types of stem cells for translational application because of their rich tissue sources, multilineage differentiation capacity, and easy amplification in vitro and unique immunobiological properties. This study demonstrated that adipose-derived MSCs (AD-MSCs) infusion can significantly suppress the increase in body weight and remarkably improve dyslipidemia in obese mice. Induction of white fat tissue "browning" and activation of adenosine monophosphate-activated protein kinase and its downstream hormone-sensitive lipase in adipose tissue were demonstrated to contribute to the antiobesity and lipid-lowering effects. Thus, AD-MSC infusion holds great therapeutic potential for dyslipidemia.

Engineered Biomaterials to Enhance Stem Cell-Based Cardiac Tissue Engineering and Therapy

Cardiovascular disease is a leading cause of death worldwide. Since adult cardiac cells are limited in their proliferation, cardiac tissue with dead or damaged cardiac cells downstream of the occluded vessel does not regenerate after myocardial infarction. The cardiac tissue is then replaced with nonfunctional fibrotic scar tissue rather than new cardiac cells, which leaves the heart weak. The limited proliferation ability of host cardiac cells has motivated investigators to research the potential cardiac regenerative ability of stem cells. Considerable progress has been made in this endeavor. However, the optimum type of stem cells along with the most suitable matrix-material and cellular microenvironmental cues are yet to be identified or agreed upon. This review presents an overview of various types of biofunctional materials and biomaterial matrices, which in combination with stem cells, have shown promises for cardiac tissue replacement and reinforcement. Engineered biomaterials also have applications in cardiac tissue engineering, in which tissue constructs are developed in vitro by combining stem cells and biomaterial scaffolds for drug screening or eventual implantation. This review highlights the benefits of using biomaterials in conjunction with stem cells to repair damaged myocardium and give a brief description of the properties of these biomaterials that make them such valuable tools to the field.

Simple measurement of the apparent viscosity of a cell from only one picture: Application to cardiac stem cells

Mechanical deformability of cells is a key property that influences their ability to migrate and their contribution to tissue development and regeneration. We analyze here the possibility of characterizing the overall deformability of cells by their apparent viscosity, using a simplified method to estimate that parameter. The proposed method simplifies the quantitative analysis of micropipette-aspiration experiments. We have studied by this procedure the overall apparent viscosity of cardiac stem cells, which are considered a promising tool to regenerate damaged cardiac tissue. Comparison with the apparent viscosity of low-viscosity cells such as immune-system cells suggests that treatments to reduce the viscosity of these cells could enhance their ability to repair damaged cardiac tissue.