Cardiac regenerative medicine

Current Status of Cardiac Regenerative Therapy Using Induced Pluripotent Stem Cells

Heart failure (HF) is a life-threatening disorder and is treated by drug therapies and surgical interventions such as heart transplantation and left ventricular assist device (LVAD). However, these treatments can lack effectiveness in the long term and are associated with issues such as donor shortage in heart transplantation, and infection, stroke, or gastrointestinal bleeding in LVADs. Therefore, alternative therapeutic strategies are still needed. In this respect, stem cell therapy has been introduced for the treatment of HF and numerous preclinical and clinical studies are employing a range of stem cell varieties. These stem cells, such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), have been shown to improve cardiac function and attenuate left ventricular remodeling. IPSCs, which have a capacity for unlimited proliferation and differentiation into cardiomyocytes, are a promising cell source for myocardial regeneration therapy. In this review, we discuss the following topics: (1) what are iPSCs; (2) the limitations and solutions for the translation of iPSC-CMs practically; and (3) the current therapeutic clinical trials.

Future stem cell analysis: progress and challenges towards state-of-the art approaches in automated cells analysis

Background and Aims

A microscopic image has been used in cell analysis for cell type identification and classification, cell counting and cell size measurement. Most previous research works are tedious, including detailed understanding and time-consuming. The scientists and researchers are seeking modern and automatic cell analysis approaches in line with the current in-demand technology.

Objectives

This article provides a brief overview of a general cell and specific stem cell analysis approaches from the history of cell discovery up to the state-of-the-art approaches.

Methodology

A content description of the literature study has been surveyed from specific manuscript databases using three review methods: manuscript identification, screening, and inclusion. This review methodology is based on Prism guidelines in searching for originality and novelty in studies concerning cell analysis.

Results

By analysing generic cell and specific stem cell analysis approaches, current technology offers tremendous potential in assisting medical experts in performing cell analysis using a method that is less laborious, cost-effective, and reduces error rates.

Conclusion

This review uncovers potential research gaps concerning generic cell and specific stem cell analysis. Thus, it could be a reference for developing automated cells analysis approaches using current technology such as artificial intelligence and deep learning.

Induced Pluripotent Stem Cell-Based Drug Screening by Use of Artificial Intelligence

Induced pluripotent stem cells (iPSCs) are terminally differentiated somatic cells that differentiate into various cell types. iPSCs are expected to be used for disease modeling and for developing novel treatments because differentiated cells from iPSCs can recapitulate the cellular pathology of patients with genetic mutations. However, a barrier to using iPSCs for comprehensive drug screening is the difficulty of evaluating their pathophysiology. Recently, the accuracy of image analysis has dramatically improved with the development of artificial intelligence (AI) technology. In the field of cell biology, it has become possible to estimate cell types and states by examining cellular morphology obtained from simple microscopic images. AI can evaluate disease-specific phenotypes of iPS-derived cells from label-free microscopic images; thus, AI can be utilized for disease-specific drug screening using iPSCs. In addition to image analysis, various AI-based methods can be applied to drug development, including phenotype prediction by analyzing genomic data and virtual screening by analyzing structural formulas and protein-protein interactions of compounds. In the future, combining AI methods may rapidly accelerate drug discovery using iPSCs. In this review, we explain the details of AI technology and the application of AI for iPSC-based drug screening.

The application of convolutional neural network to stem cell biology

Induced pluripotent stem cells (iPSC) are one the most prominent innovations of medical research in the last few decades. iPSCs can be easily generated from human somatic cells and have several potential uses in regenerative medicine, disease modeling, drug screening, and precision medicine. However, further innovation is still required to realize their full potential. Machine learning is an algorithm that learns from large datasets for pattern formation and classification. Deep learning, a form of machine learning, uses a multilayered neural network that mimics human neural circuit structure. Deep neural networks can automatically extract features from an image, although classical machine learning methods still require feature extraction by a human expert. Deep learning technology has developed recently; in particular, the accuracy of an image classification task by using a convolutional neural network (CNN) has exceeded that of humans since 2015. CNN is now used to address several tasks including medical issues. We believe that CNN would also have a great impact on the research of stem cell biology. iPSCs are utilized after their differentiation to specific cells, which are characterized by molecular techniques such as immunostaining or lineage tracing. Each cell shows a characteristic morphology; thus, a morphology-based identification system of cell type by CNN would be an alternative technique. The development of CNN enables the automation of identifying cell types from phase contrast microscope images without molecular labeling, which will be applied to several researches and medical science. Image classification is a strong field among deep learning tasks, and several medical tasks will be solved by deep learning-based programs in the future.

Comparative Proteomic Analysis Reveals the Upregulation of Ketogenesis in Cardiomyocytes Differentiated from Induced Pluripotent Stem Cells

Diverse metabolic pathways, such as the tricarboxylic acid cycle, pyruvate metabolism, and oxidative phosphorylation, regulate the differentiation of induced pluripotent stem cells (iPSCs) to cells of specific lineages and organs. Here, the protein dynamics during cardiac differentiation of human iPSCs into cardiomyocytes (CMs) are characterized. The differentiation is induced by N-(6-methyl-2-benzothiazolyl)-2-[(3,4,6,7-tetrahydro-4-oxo-3-phenylthieno[3,2-d]pyrimidin-2-yl)thio]-acetamide, a Wnt signaling inhibitor, and confirmed by the mRNA and protein expression of cTnT and MLC2A in CMs. For comparative proteomics, cells from three stages, namely, hiPSCs, cardiac progenitor cells, and CMs, are prepared using the three-plex tandem mass tag labeling approach. In total, 3970 proteins in triplicate analysis are identified. As the result, the upregulation of proteins associated with branched chain amino acid degradation and ketogenesis by the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis are observed. The levels of 3-hydroxymethyl-3-methylglutaryl-CoA lyase, 3-hydroxymethyl-3-methylglutaryl-CoA synthase 2, and 3-hydroxybutyrate dehydrogenase 1, involved in ketone body metabolism, are determined using western blotting, and the level of acetoacetate, the final product of ketogenesis, is higher in CMs. Taken together, these observations indicate that proteins required for the production of diverse energy sources are naturally self-expressed during cardiomyogenic differentiation. Furthermore, acetoacetate concentration might act as a regulator of this differentiation.

Automated Deep Learning-Based System to Identify Endothelial Cells Derived from Induced Pluripotent Stem Cells

Deep learning technology is rapidly advancing and is now used to solve complex problems. Here, we used deep learning in convolutional neural networks to establish an automated method to identify endothelial cells derived from induced pluripotent stem cells (iPSCs), without the need for immunostaining or lineage tracing. Networks were trained to predict whether phase-contrast images contain endothelial cells based on morphology only. Predictions were validated by comparison to immunofluorescence staining for CD31, a marker of endothelial cells. Method parameters were then automatically and iteratively optimized to increase prediction accuracy. We found that prediction accuracy was correlated with network depth and pixel size of images to be analyzed. Finally, K-fold cross-validation confirmed that optimized convolutional neural networks can identify endothelial cells with high performance, based only on morphology.

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Neural networks were trained to spot endothelial cells on phase-contrast images

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Performance was correlated with network depth and pixel size of training images

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Optimized networks identify endothelial cells with high accuracy

Stem cell-based therapy for ischemic heart disease

Despite great advances in therapy over the past decades, ischemic heart disease (IHD) remains the leading cause of death worldwide because the decrease in mortality after acute myocardial infarction (AMI) leads to a longer life span in patients with chronic postinfarct heart failure (HF). There are no existing medical treatments that can cure chronic HF and the only currently available therapeutic option for end-stage HF is heart transplantation. However, transplantation is limited by the shortage of donor organs and patients require lifelong immunosuppression. In the past 10 years, stem cell-based cardiac therapy has been proposed as a promising approach for the treatment of IHD. There is a variety of potential stem cell types for cardiac repair and regeneration, including bone marrow cells (BMCs), resident cardiac stem cells (CSCs) and induced pluripotent stem cells (iPSCs). Stem cell-based therapy may comprise cell transplantation or cardiac tissue engineering (CTE), which might be an attractive alternative to solve the problems of low retention and poor survival of transplanted cells. This review focuses on the characteristics of stem cells from various sources and discusses the strategies of stem cell-based therapy for the treatment of IHD.

Exercise tames the wild side of the Myc network: a hypothesis

We propose that the well-documented therapeutic actions of repeated physical activities over human lifespan are mediated by the rapidly turning over proto-oncogenic Myc (myelocytomatosis) network of transcription factors. This transcription factor network is unique in utilizing promoter and epigenomic (acetylation/deacetylation, methylation/demethylation) mechanisms for controlling genes that include those encoding intermediary metabolism (the primary source of acetyl groups), mitochondrial functions and biogenesis, and coupling their expression with regulation of cell growth and proliferation. We further propose that remote functioning of the network occurs because there are two arms of this network, which consists of driver cells (e.g., working myocytes) that metabolize carbohydrates, fats, proteins, and oxygen and produce redox-modulating metabolites such as H₂O₂, NAD⁺, and lactate. The exercise-induced products represent autocrine, paracrine, or endocrine signals for target recipient cells (e.g., aortic endothelium, hepatocytes, and pancreatic β-cells) in which the metabolic signals are coupled with genomic networks and interorgan signaling is activated. And finally, we propose that lactate, the major metabolite released from working muscles and transported into recipient cells, links the two arms of the signaling pathway. Recently discovered contributions of the Myc network in stem cell development and maintenance further suggest that regular physical activity may prevent age-related diseases such as cardiovascular pathologies, cancers, diabetes, and neurological functions through prevention of stem cell dysfunctions and depletion with aging. Hence, regular physical activities may attenuate the various deleterious effects of the Myc network on health, the wild side of the Myc-network, through modulating transcription of genes associated with glucose and energy metabolism and maintain a healthy human status.

Induced pluripotent stem cells in cardiovascular medicine

Induced pluripotent stem (iPS) cells are generated by reprogramming human somatic cells through the forced expression of several embryonic stem (ES) cell-specific transcription factors. The potential of iPS cells is having a significant impact on regenerative medicine, with the promise of infinite self-renewal, differentiation into multiple cell types, and no problems concerning ethics or immunological rejection. Human iPS cells are currently generated by transgene introduction principally through viral vectors, which integrate into host genomes, although the associated risk of tumorigenesis is driving research into nonintegration methods. Techniques for pluripotent stem cell differentiation and purification to yield cardiomyocytes are also advancing constantly. Although there remain some unsolved problems, cardiomyocyte transplantation may be a reality in the future. After those problems will be solved, applications of human iPS cells in human cardiovascular regenerative medicine will be envisaged for the future. Furthermore, iPS cell technology has generated new human disease models using disease-specific cells. This paper summarizes the progress of iPS cell technology in cardiovascular research.

Collagen scaffolds with or without the addition of RGD peptides support cardiomyogenesis after aggregation of mouse embryonic stem cells

Embryonic stem (ES) cell-based cardiac muscle repair using tissue-engineered scaffolds is an attractive prospective treatment option for patients suffering from heart disease. In this study, our aim was to characterize mouse ES cell-derived cardiomyocytes growing on collagen I/III scaffolds, modified with the adhesion peptides arginine-glycine-aspartic acid (RGD). Mouse ES-derived embryoid bodies (EBs) differentiated efficiently into beating cardiomyocytes on the collagen scaffolds. QPCR analysis and immunofluorescent staining showed that cardiomyocytes expressed cardiac muscle-related transcripts and proteins. Analysis of cardiomyocytes by electron microscopy identified muscle fiber bundles and Z bands, typical of ES-derived cardiomyocytes. No differences were detected between the collagen + RGD and collagen control scaffolds. ES cells that were not differentiated as EBs prior to seeding on the scaffold, did not differentiate into cardiomyocytes. These results indicate that a collagen I/III scaffold supports cardiac muscle development and function after EB formation, and that this scaffold appears suitable for future in vivo testing. The addition of the RGD domain to the collagen scaffold did not improve cardiomyocyte development or viability, indicating that RGD signaling to integrins was not a rate-limiting event for cardiomyogenesis from EBs seeded on a collagen scaffold.

Effects of mesenchymal stem cells on matrix metalloproteinase synthesis in cardiac fibroblasts

Mesenchymal stem cell (MSC) transplantation has been known to decrease matrix metalloproteinase (MMP) synthesis in myocardium after myocardial infarction (MI) and improve ventricular remodeling; however, the underlying mechanisms are unclear. This study investigated the effects of MSC on MMP synthesis in cardiac fibroblasts (CFs) through paracrine actions. CFs were cultured under hypoxic (0.5% pO(2)) conditions for 24 h before co-culture with MSCs or hypoxia-preconditioned MSCs (H-MSCs) in transwell plates. CFs and MSCs/H-MSCs shared a medium with or without erythropoietin (EPO) neutralizing antibody (EPOAb) or EPO-soluble receptor (EPOsR). The results showed that protein expression and activity of MMP-2 and membrane type 1-MMP, but not MMP-9, in CFs were significantly increased in response to hypoxia and decreased after co-culture with MSCs or H-MSCs. Hypoxia up-regulated phosphorylation of extracellular signal-regulated kinase (ERK)1/2 of CFs which was down-regulated after CFs' co-culture with MSCs. Tissue inhibitors of metalloproteinases-1 (TIMP-1) in CFs was decreased after hypoxia and increased when co-cultured with MSCs or H-MSCs. Exogenous EPOAb or EPOsR partially inhibited MSCs' effect on MMP-2 expression and activity in CFs. The present findings suggested that MSCs influence MMP/TIMP expression in CFs via the ERK1/2 pathway and EPO acts as a key factor in the paracrine actions of MSCs.

Phenotypic changes in cultured smooth muscle cells: limitation or opportunity for tissue engineering of hollow organs?

Smooth muscle cells (SMCs) are typically used as a cell source for the reconstruction of hollow organs by conventional tissue engineering techniques. However, the necessity for and advantage of the use of tissue-specific SMCs are unknown. The present study investigated the phenotypic changes that occur following isolation and in vitro expansion of rat SMC populations isolated from three different tissues: the aorta, oesophagus and urinary bladder. rSMCs were isolated by enzymatic dispersion and expanded by conventional cell culture techniques, yielding microscopically homogeneous populations. SMC phenotypes were monitored according to their expression of marker proteins during the first two passages. Two of the three SMC populations (rSMC-a and rSMC-e) showed a marked change in their marker protein profiles during the first two passages, which resulted in a homogeneous phenotype that was neither fully contractile nor fully synthetic. SMCs from the urinary bladder did not show such a shift. Differences between the three rSMC populations were observed with regard to proliferative activity and gene expression patterns, suggesting the retention of some tissue-specific cell characteristics. In summary, phenotypic changes in SMCs occur as a result of conventional cell isolation and expansion techniques, thus questioning the necessity for a tissue-specific cell source for regenerative medicine applications.

Engineering skeletal muscle tissue--new perspectives in vitro and in vivo

Muscle tissue engineering (TE) has not yet been clinically applied because of several problems. However, the field of skeletal muscle TE has been developing tremendously and new approaches and techniques have emerged. This review will highlight recent developments in the field of nanotechnology, especially electrospun nanofibre matrices, as well as potential cell sources for muscle TE. Important developments in cardiac muscle TE and clinical studies on Duchenne muscular dystrophy (DMD) will be included to show their implications on skeletal muscle TE.

Human cardiac explant-conditioned medium: soluble factors and cardiomyogenic effect on mesenchymal stem cells

The use of conditioned medium (CM) from human cardiac explants (HCEs) as a potential source of paracrine factors for adult stem cell signaling has never been evaluated. We hypothesized that HCEs might provide a source of soluble factors triggering the differentiation of mesenchymal stem cells (MSCs) into cardiomyocyte-like cells. By using two-dimensional electrophoresis (2-DE) gels/mass spectrometry and antibody macroarray assays, we found that HCEs release macromolecules, including cytokines, growth factors and myocardial and metabolism-related proteins into the culture medium. We identified a total of 20 proteins in the HCE-CM. However, as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 2-DE, these 20 proteins account for only a fraction of the total number of proteins present in the HCE-CM. We also found that CM increased the proliferation of bone marrow-derived-MSCs (BM-MSCs) in vitro. Unlike the other effects, this effect was most evident after 48 h of culture. Moreover, we examined the effect of HCE-CM on levels of mRNA and protein for specific cardiac markers. We showed that a surprisingly big fraction of BM-MSCs (3.4-5.0%) treated in vitro with HCE-CM became elongated and began to express cardiac markers, consistent with their possible differentiation into cardiomyocyte-like cells. Our in vitro model may be useful not only per se, but also for studies of the mechanisms of action of soluble factors involved in cell differentiation, paving the way for possible new protein-based treatments in the future.

Genetically manipulated progenitor cell sheet with diprotin A improves myocardial function and repair of infarcted hearts

We postulated that the combination of overexpression of CXCR4 in mesenchymal stem cells (MSC) with diprotin A would enhance MSC recruitment and penetration into ischemic myocardium, leading to an improvement in heart function after myocardial infarction (MI). Male rat MSC were genetically engineered with adenoviral vectors coexpressing CXCR4 and enhanced green fluorescent protein (EGFP) (MSC(CXCR4)), GFP alone (MSC(Null), control), or siRNA-targeted CXCR4 (MSC(siRNA)). Cell sheets were applied over the surface of infarcted left ventricle (LV) in female rats 7 days after ligation of the left anterior descending coronary artery (LAD) pretreated with either vehicle (VEH) or diprotin A (DIP). At 28 days after cell sheet implantation, echocardiography was performed. Hearts were harvested for histological analysis 7 days after LAD ligation or 28 days after cell sheet implantation. DPP-IV and stroma-derived factor-1α (SDF-1α) in the LV were analyzed. Efficacy of engraftment was determined by the presence of Y chromosome in nuclei (Y(ch+)). LV blood vessel density and apoptosis were also analyzed. Myocardial SDF-1α was elevated before placement of the cell sheet in the DIP group compared with vehicle group on day 7 after LAD. On day 28 after cell sheet transplantation, the number of Y(ch+) was increased in the MSC(CXCR4) + VEH group compared with the MSC(Null) + VEH group and further increased in the MSC(CXCR4) + DIP treated group. This enhanced response was associated with increased angiogenesis in both sides of epicardium and improvement of LV function. Combination of gene-manipulated MSC(CXCR4) patch with DIP pretreatment inhibits myocardial ischemia-induced apoptosis, promotes tissue angiogenesis, and enhances cell engraftment, leading to improved LV mechanical function after MI.

The cardiomyocyte lineage is critical for optimization of stem cell therapy in a mouse model of myocardial infarction

We recently described a murine embryonic stem cell (ESC) line engineered to express the activated Notch 4 receptor in a tetracycline (doxcycline; Dox) regulated fashion (tet-notch4 ESCs). Notch 4 induction in Flk1(+) hematopoietic and vascular progenitors from this line respecified them to a cardiovascular fate. We reasoned that these cells would be ideal for evaluating the contribution of the cardiomyocyte and vascular lineages to the functional improvement noted following stem cell transplantation in infarcted hearts. Flk-1(+) Tet-notch4 cells from d 3 embryoid bodies exposed to doxycycline (Dox(+)) were compared to uninduced (Dox(-)) Flk-1(+) cells. Mice underwent transplantation of 5 x 10(5) Dox(+) cells, Dox(-)cells, or an equal volume of serum-free medium after surgically induced myocardial infarction. The mean ejection fraction was 59 + or - 15, 46 + or - 17, and 39 + or - 13% in the Dox(+), Dox(-), and serum-free medium groups, respectively (P<0.05 for the differences among all 3 groups). Immunohistochemistry of hearts injected with Dox(+) grafts expressed myocardial and vascular markers, whereas grafts of Dox(-) cells expressed primarily vascular markers. We conclude that cardiovascular progenitors are more effective than vascular progenitors in improving function after myocardial infarction. The transplantation of appropriate cell types is critical for maximizing the benefit of cardiovascular cell therapy.-Adler, E. D., Chen, V. C., Bystrup, A., Kaplan, A. D., Giovannone, S., Briley-Saebo, K., Young, W., Kattman, S., Mani, V., Laflamme, M., Zhu, W.-Z., Fayad, Z., Keller, G. The cardiomyocyte lineage is critical for optimization of stem cell therapy in a mouse model of myocardial infarction.

Cell-based therapies for ischemic heart disease--"trick and treat"

Cell therapy is a promising approach to improve cardiac function in patients with ischemic heart disease. Beneficial effects of cell therapy have been shown in experimental studies and clinical trials. However, with current treatment strategies the therapeutic effect is limited. In the current article, critical aspects of cell therapy are discussed: cell type, the state of ischemic heart disease and the condition of cells at the time of treatment. Because treatment options of native cells by systemic pharmacotherapy are limited, we propose a concept of ex vivo preconditioning to overcome functional cell impairment and to enhance cell-based regenerative approaches.

Chemical and physical stimuli induce cardiomyocyte differentiation from stem cells

In this study we investigated cardiomyocyte differentiation of rat bone marrow-mesenchymal stem cells (BM-MSCs) by treating the stem cells with conditions mimicking that of myocardial infarction. The extract from infarcted rat myocardium contained the biochemical factors arising after infarction. The cardiac contraction and relaxation were simulated by applying 4% strain at 1 Hz to the stem cells. We found that the extract from infarcted myocardium or 4% strain each alone could induce cardiomyocyte differentiation of BM-MSCs, as shown by expression of cardiomyocyte-specific genes including alpha-actin, connexin 43, Nkx2.5, MEF2c, GATA4, alpha-MHC, and Troponin I. Furthermore, a combination of the extract and 4% strain had stronger effects on cardiomyocyte differentiation than what either treatment alone had. Our results suggest that this in vitro model system simulates the local cardiac environment cues after infarction and may be useful in identifying the biochemical and physical factors involved in cardiomyocyte differentiation.