Induced pluripotent stem cells (iPSCs) are reprogrammed cells that have features similar to embryonic stem cells, such as the capacity of self-renewal and differentiation into many types of cells, ...including cardiac myocytes. Although initially the reprogramming efficiency was low, several improvements in reprogramming methods have achieved robust and efficient generation of iPSCs without genomic insertion of transgenes. iPSCs display clonal variations in epigenetic and genomic profiles and cellular behavior in differentiation. iPSC-derived cardiac myocytes (iPSC cardiac myocytes) recapitulate phenotypic differences caused by genetic variations, making them attractive human disease models, and are useful for drug discovery and toxicology testing. In addition, iPSC cardiac myocytes can help with patient stratification in regard to drug responsiveness. Furthermore, they can be used as source cells for cardiac regeneration in animal models. Here, we review recent progress in iPSC technology and its applications to cardiac diseases.
It has been nearly 15 years since the discovery of human-induced pluripotent stem cells (iPSCs). During this time, differentiation methods to targeted cells have dramatically improved, and many types ...of cells in the human body can be currently generated at high efficiency. In the cardiovascular field, the ability to generate human cardiomyocytes in vitro with the same genetic background as patients has provided a great opportunity to investigate human cardiovascular diseases at the cellular level to clarify the molecular mechanisms underlying the diseases and discover potential therapeutics. Additionally, iPSC-derived cardiomyocytes have provided a powerful platform to study drug-induced cardiotoxicity and identify patients at high risk for the cardiotoxicity; thus, accelerating personalized precision medicine. Moreover, iPSC-derived cardiomyocytes can be sources for cardiac cell therapy. Here, we review these achievements and discuss potential improvements for the future application of iPSC technology in cardiovascular diseases.
Fatigue cracks initiate in the lower flange of rivet girder supports because of the stress caused by bridge member deterioration. There are cases where fatigue cracks cannot be immediately repaired ...because the procedure would be time consuming and costly. This research identifies some of the causes of the stress in the lower flange of rivet girder supports, having conducted loading tests on a rivet girder, and FEM analyses. On the basis these results, we began developing reinforcement methods for inhibiting fatigue crack growth in the lower flanges of rivet girder supports. Moreover, we are verifying the effect of these reinforcement methods through loading tests.
Abstract
One of the earliest maturation steps in cardiomyocytes (CMs) is the sarcomere protein isoform switch between TNNI1 and TNNI3 (fetal and neonatal/adult troponin I). Here, we generate human ...induced pluripotent stem cells (hiPSCs) carrying a TNNI1
EmGFP
and TNNI3
mCherry
double reporter to monitor and isolate mature sub-populations during cardiac differentiation. Extensive drug screening identifies two compounds, an estrogen-related receptor gamma (ERRγ) agonist and an S-phase kinase-associated protein 2 inhibitor, that enhances cardiac maturation and a significant change to TNNI3 expression. Expression, morphological, functional, and molecular analyses indicate that hiPSC-CMs treated with the ERRγ agonist show a larger cell size, longer sarcomere length, the presence of transverse tubules, and enhanced metabolic function and contractile and electrical properties. Here, we show that ERRγ-treated hiPSC-CMs have a mature cellular property consistent with neonatal CMs and are useful for disease modeling and regenerative medicine.
Variation in the differentiation capacity of induced pluripotent stem cells (iPSCs) to specific lineages is a significant concern for their use in clinical applications and disease modeling. To ...identify factors that affect differentiation capacity, we performed integration analyses between hematopoietic differentiation performance and molecular signatures such as gene expression, DNA methylation, and chromatin status, using 35 human iPSC lines and four ESC lines. Our analyses revealed that hematopoietic commitment of PSCs to hematopoietic precursors correlates with IGF2 expression level, which in turn depends on signaling-dependent chromatin accessibility at mesendodermal genes. Maturation capacity for conversion of PSC-derived hematopoietic precursors to mature blood associates with the amount and pattern of DNA methylation acquired during reprogramming. Our study therefore provides insight into the molecular features that determine the differential capacities seen among human iPSC lines and, through the predictive potential of this information, highlights a way to select optimal iPSCs for clinical applications.
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•Human PSC hematopoietic commitment capacity correlates with IGF2 expression•IGF2 expression depends on signaling-dependent chromatin accessibility•Maturation capacity is associated with reprogramming-related DNA methylation•Epigenetic features can help identify human PSC lines with differential capacities
Nishizawa et al. integrate analysis of differentiation outcome and molecular characterization to identify features of human iPSCs associated with high and low capacities for hematopoietic specification and maturation. Prospective use of this type of information could help in choosing iPSC lines best suited to different applications.
In this paper, a stress correction method for flow stress identification using notched round bar tensile test is proposed. Flow stress is evaluated in uniform elongation and local elongation until ...final fracture in a tensile test with circumference notched round bar tensile test specimens. Tensile load and change in the shape of the notch are measured by image analysis. In order to correct the average tensile stress to the flow stress, inverse analysis is applied to the tensile test. For the validation of the inverse analysis, numerical tensile tests are performed by FEM. As a result of applying the inverse analysis for the numerical tensile tests, the corrected flow stress completely reproduces the two types of reference flow stress curves which are determined by Swift’s and Voce’s law. On the other hand, the flow stress corrected by Bridgman’s method, which is a conventional stress correction method, overestimated these reference flow stress curves. In the case of the actual tensile test of low carbon steel SS400 (in JIS), the flow stress corrected by inverse analysis corresponds to Swift’s law determined in uniform elongation. As well as numerical tensile test results, the flow stress corrected by Bridgman’s method is higher than that of obtained by the inverse analysis.
Induced pluripotent stem cells (iPSCs) are reprogrammed cells that have features similar to embryonic stem cells, such as the capacity of self-renewal and differentiation into many types of cells, ...including cardiac myocytes. Although initially the reprogramming efficiency was low, several improvements in reprogramming methods have achieved robust and efficient generation of iPSCs without genomic insertion of transgenes. iPSCs display clonal variations in epigenetic and genomic profiles and cellular behavior in differentiation. iPSC-derived cardiac myocytes (iPSC cardiac myocytes) recapitulate phenotypic differences caused by genetic variations, making them attractive human disease models, and are useful for drug discovery and toxicology testing. In addition, iPSC cardiac myocytes can help with patient stratification in regard to drug responsiveness. Furthermore, they can be used as source cells for cardiac regeneration in animal models. Here, we review recent progress in iPSC technology and its applications to cardiac diseases.
Isolation of specific cell types, including pluripotent stem cell (PSC)-derived populations, is frequently accomplished using cell surface antigens expressed by the cells of interest. However, ...specific antigens for many cell types have not been identified, making their isolation difficult. Here, we describe an efficient method for purifying cells based on endogenous miRNA activity. We designed synthetic mRNAs encoding a fluorescent protein tagged with sequences targeted by miRNAs expressed by the cells of interest. These miRNA switches control their translation levels by sensing miRNA activities. Several miRNA switches (miR-1-, miR-208a-, and miR-499a-5p-switches) efficiently purified cardiomyocytes differentiated from human PSCs, and switches encoding the apoptosis inducer Bim enriched for cardiomyocytes without cell sorting. This approach is generally applicable, as miR-126-, miR-122-5p-, and miR-375-switches purified endothelial cells, hepatocytes, and insulin-producing cells differentiated from hPSCs, respectively. Thus, miRNA switches can purify cell populations for which other isolation strategies are unavailable.
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•Synthetic miRNA switches can purify target cell populations based on miRNA activity•miR-1-, -208a-, and -499a-5p-switches highly purify hPSC-derived cardiomyocytes•miR-Bim switches enrich for cardiomyocytes without the need for cell sorting•miRNA switches can isolate desired cell types without significant side effects
Miki et al. develop synthetic miRNA switches for isolating cell populations that are otherwise difficult to purify. Several miRNA-responsive switches precisely and efficiently isolate human pluripotent stem cell (hPSC)-derived cardiomyocytes, and miRNA switches can be programmed for purification of various cell types including hPSC-derived endothelial cells, hepatocytes, and insulin-producing cells.
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