The recent breakthrough in the generation of induced pluripotent stem (iPS) cells, which are almost indistinguishable from embryonic stem (ES) cells, facilitates the generation of murine disease- and ...human patient-specific stem cell lines. The aim of this study was to characterize the cardiac differentiation potential of a murine iPS cell clone in comparison to a well-established murine ES cell line.
With the use of a standard embryoid body-based differentiation protocol for ES cells, iPS cells as well as ES cells were differentiated for 24 days. Although the analyzed iPS cell clone showed a delayed and less efficient formation of beating embryoid bodies compared with the ES cell line, the differentiation resulted in an average of 55% of spontaneously contracting iPS cell embryoid bodies. Analyses on molecular, structural, and functional levels demonstrated that iPS cell-derived cardiomyocytes show typical features of ES cell-derived cardiomyocytes. Reverse transcription polymerase chain reaction analyses demonstrated expression of marker genes typical for mesoderm, cardiac mesoderm, and cardiomyocytes including Brachyury, mesoderm posterior factor 1 (Mesp1), friend of GATA2 (FOG-2), GATA-binding protein 4 (GATA4), NK2 transcription factor related, locus 5 (Nkx2.5), T-box 5 (Tbx5), T-box 20 (Tbx20), atrial natriuretic factor (ANF), myosin light chain 2 atrial transcripts (MLC2a), myosin light chain 2 ventricular transcripts (MLC2v), alpha-myosin heavy chain (alpha-MHC), and cardiac troponin T in differentiation cultures of iPS cells. Immunocytology confirmed expression of cardiomyocyte-typical proteins including sarcomeric alpha-actinin, titin, cardiac troponin T, MLC2v, and connexin 43. iPS cell cardiomyocytes displayed spontaneous rhythmic intracellular Ca(2+) fluctuations with amplitudes of Ca(2+) transients comparable to ES cell cardiomyocytes. Simultaneous Ca(2+) release within clusters of iPS cell-derived cardiomyocytes indicated functional coupling of the cells. Electrophysiological studies with multielectrode arrays demonstrated functionality and presence of the beta-adrenergic and muscarinic signaling cascade in these cells.
iPS cells differentiate into functional cardiomyocytes. In contrast to ES cells, iPS cells allow derivation of autologous functional cardiomyocytes for cellular cardiomyoplasty and myocardial tissue engineering.
Based on the fact that traumatic brain injury is associated with mitochondrial dysfunction we aimed at localization of mitochondrial defect and attempted to correct it by thiamine.
Interventional ...controlled experimental animal study was used. Adult male Sprague-Dawley rats were subjected to lateral fluid percussion traumatic brain injury. Thiamine was administered 1 h prior to trauma; cortex was extracted for analysis 4 h and 3 d after trauma.
Increased expression of inducible nitric oxide synthase (iNOS) and tumor necrosis factor receptor 1 (TNF-R1) by 4 h was accompanied by a decrease in mitochondrial respiration with glutamate but neither with pyruvate nor succinate. Assays of TCA cycle flux-limiting 2-oxoglutarate dehydrogenase complex (OGDHC) and functionally linked enzymes (glutamate dehydrogenase, glutamine synthetase, pyruvate dehydrogenase, malate dehydrogenase and malic enzyme) indicated that only OGDHC activity was decreased. Application of the OGDHC coenzyme precursor thiamine rescued the activity of OGDHC and restored mitochondrial respiration. These effects were not mediated by changes in the expression of the OGDHC sub-units (E1k and E3), suggesting post-translational mechanism of thiamine effects. By the third day after TBI, thiamine treatment also decreased expression of TNF-R1. Specific markers of unfolded protein response did not change in response to thiamine.
Our data point to OGDHC as a major site of damage in mitochondria upon traumatic brain injury, which is associated with neuroinflammation and can be corrected by thiamine. Further studies are required to evaluate the pathological impact of these findings in clinical settings.
•Traumatic brain injury impairs mitochondrial respiration.•2-Oxoglutarate dehydrogenase is a major site of damage in mitochondria.•Inactivation of 2-oxoglutarate dehydrogenase is associated with neuroinflammation.•Thiamine protects 2-oxoglutarate dehydrogenase and mitochondrial respiration.
Animal models and clinical studies suggest an influence of angiotensin II (AngII) on the pathogenesis of liver diseases via the renin–angiotensin system. AngII application increases portal blood ...pressure, reduces bile flow, and increases permeability of liver tight junctions. Establishing the subcellular localization of angiotensin II receptor type 1 (AT1R), the main AngII receptor, helps to understand the effects of AngII on the liver. We localized AT1R in situ in human and porcine liver and porcine gallbladder by immunohistochemistry. In order to do so, we characterized commercial anti-AT1R antibodies regarding their capability to recognize heterologous human AT1R in immunocytochemistry and on western blots, and to detect AT1R using overlap studies and AT1R-specific blocking peptides. In hepatocytes and canals of Hering, AT1R displayed a tram-track-like distribution, while in cholangiocytes AT1R appeared in a honeycomb-like pattern; i.e., in liver epithelia, AT1R showed an equivalent distribution to that in the apical junctional network, which seals bile canaliculi and bile ducts along the blood–bile barrier. In intrahepatic blood vessels, AT1R was most prominent in the tunica media. We confirmed AT1R localization in situ to the plasma membrane domain, particularly between tight and adherens junctions in both human and porcine hepatocytes, cholangiocytes, and gallbladder epithelial cells using different anti-AT1R antibodies. Localization of AT1R at the junctional complex could explain previously reported AngII effects and predestines AT1R as a transmitter of tight junction permeability.
Pluripotent embryonic stem cells (ESCs) maintain self-renewal while ensuring a rapid response to differentiation cues. The identification of genes maintaining ESC identity is important to develop ...these cells for their potential therapeutic use. Here we report a genome-scale RNAi screen for a global survey of genes affecting ESC identity via alteration of Oct4 expression. Factors with the strongest effect on Oct4 expression included components of the Paf1 complex, a protein complex associated with RNA polymerase II. Using a combination of proteomics, expression profiling, and chromatin immunoprecipitation, we demonstrate that the Paf1C binds to promoters of key pluripotency genes, where it is required to maintain a transcriptionally active chromatin structure. The Paf1C is developmentally regulated and blocks ESC differentiation upon overexpression, and the knockdown in ESCs causes expression changes similar to Oct4 or Nanog depletions. We propose that the Paf1C plays an important role in maintaining ESC identity.
Aims
Mechanochemical signalling drives organogenesis and is highly conserved in mammal evolution. Regaining recovery in myocardial jeopardy by inducing principles linking cardiovascular therapy and ...clinical outcome has been the dream of scientists for decades. Concepts involving embryonic pathways to regenerate adult failing hearts became popular in the early millennium. Since then, abundant data on stem cell research have been published, never reaching widespread application in heart failure therapy. Another conceptual access, using mechanotransduction in cardiac veins to limit myocardial decay, is pressure‐controlled intermittent coronary sinus occlusion (PICSO). Recently, we reported acute molecular signs and signals of PICSO activating regulatory miRNA and inducing cell proliferation mimicking cardiac development in adult failing hearts. According to a previously formulated hypothesis, ‘embryonic recall’, this study aimed to define molecular signals involved in endogenous heart repair during PICSO and study their relation to patient survival.
Methods and results
We previously reported a study on the acute molecular effects of PICSO in an observational non‐randomized study. Eight out of the thirty‐two patients with advanced heart failure undergoing cardiac resynchronization therapy (CRT) were treated with PICSO. Survival was monitored over 10 years, and coronary sinus blood samples were collected during intervention before and after 20 min and tested for miRNA signalling and proliferation when co‐cultured with cardiomyocytes. A numerically lower death rate post‐CRT and PICSO as compared with control CRT only, and a non‐significant reduction in all‐cause mortality risk of 42% was observed (37.5% vs. 54.0%, relative risk = 0.58, 95% confidence interval: 0.17–2.05; P = 0.402). Four miRNAs involved in cell cycle, proliferation, morphogenesis, embryonic development, and apoptosis significantly increased concomitantly in survivors and PICSO compared with a decrease in non‐survivors (hsa‐miR Let7b, P < 0.01; hsa‐miR‐ 421, P < 0.006; hsa‐miR 363‐3p, P < 0.03 and hsa‐miR 19b‐3p P < 0.01). In contrast, three miRNAs involved in proliferation and survival, determining cell fate, and recycling endosomes decreased in survivors and PICSO (hsa miR 101‐3p, P < 0.03; hsa‐miR 25‐3p, P < 002; hsa‐miR 30d‐5p P < 0.04). In vitro cellular proliferation increased in survivors and lowered in non‐survivors showing a pattern distinction, discriminating longevity according to up to 10‐year survival in heart failure patients.
Conclusions
This study proposes that generating regenerative signals observed during PICSO intervention relate to patient outcomes. Morphogenetic pathways induced by periods of flow reversal in cardiac veins in a domino‐like pattern transform embryonic into regenerative signals. Studies supporting the conversion of mechanochemical signals into regenerative molecules during PICSO are warranted to substantiate predictive power on patient longevity, opening new therapeutic avenues in otherwise untreatable heart failure.
Induced pluripotent stem (iPS) cells generated from accessible adult cells of patients with genetic diseases open unprecedented opportunities for exploring the pathophysiology of human diseases in ...vitro. Catecholaminergic polymorphic ventricular tachycardia type 1 (CPVT1) is an inherited cardiac disorder that is caused by mutations in the cardiac ryanodine receptor type 2 gene (RYR2) and is characterized by stress-induced ventricular arrhythmia that can lead to sudden cardiac death in young individuals. The aim of this study was to generate iPS cells from a patient with CPVT1 and determine whether iPS cell-derived cardiomyocytes carrying patient specific RYR2 mutation recapitulate the disease phenotype in vitro.
iPS cells were derived from dermal fibroblasts of healthy donors and a patient with CPVT1 carrying the novel heterozygous autosomal dominant mutation p.F2483I in the RYR2. Functional properties of iPS cell derived-cardiomyocytes were analyzed by using whole-cell current and voltage clamp and calcium imaging techniques.
Patch-clamp recordings revealed arrhythmias and delayed afterdepolarizations (DADs) after catecholaminergic stimulation of CPVT1-iPS cell-derived cardiomyocytes. Calcium imaging studies showed that, compared to healthy cardiomyocytes, CPVT1-cardiomyocytes exhibit higher amplitudes and longer durations of spontaneous Ca(2+) release events at basal state. In addition, in CPVT1-cardiomyocytes the Ca(2+)-induced Ca(2+)-release events continued after repolarization and were abolished by increasing the cytosolic cAMP levels with forskolin.
This study demonstrates the suitability of iPS cells in modeling RYR2-related cardiac disorders in vitro and opens new opportunities for investigating the disease mechanism in vitro, developing new drugs, predicting their toxicity, and optimizing current treatment strategies.
Endogenous cardiac regeneration has been focused for decades as a potential therapy for heart diseases with cell loss, and dimethyl sulfoxide (DMSO) has been proposed as a treatment for many ...diseases. In this study, we aimed to investigate the function of DMSO on fetal cardiomyocyte proliferation. By tracing BrdU+/α actinin+ cells or Ki67+/α actinin+ cells with immunohistochemical staining, we found that DMSO remarkably promoted fetal cardiomyocytes proliferation, and at the late developmental stage (LDS), such effects were more efficient than that at early developmental stage (EDS). Western blot data revealed a significant increase in STAT3 phosphorylation under DMSO treatments at LDS, while not at EDS. Consistently, STAT3 phosphorylation blocker STA21 could greatly reverse DMSO's function at LDS whereas hardly at EDS. Moreover, hearts at the EDS had less total STAT3 protein, but relatively much higher level of phosphorylated STAT3. This suggests that DMSO promote fetal cardiomyocytes proliferation, and STAT3 phosphorylation play a pivotal role in DMSO's function. With maturation, DMSO exerted a better ability to favor cardiomyocyte proliferation depending on STAT3 phosphorylation. Therefore, DMSO could serve as an effective, economic, and safe therapy for heart diseases with cell loss.
Early (E9.5-E11.5) embryonic heart cells beat spontaneously, even though the adult pacemaking mechanisms are not yet fully established. Here we show that in isolated murine early embryonic ...cardiomyocytes periodic oscillations of cytosolic Ca(2+) occur and that these induce contractions. The Ca(2+) oscillations originate from the sarcoplasmic reticulum and are dependent on the IP(3) and the ryanodine receptor. The Ca(2+) oscillations activate the Na(+)-Ca(2+) exchanger, giving rise to subthreshold depolarizations of the membrane potential and/or action potentials. Although early embryonic heart cells are voltage-independent Ca(2+) oscillators, the generation of action potentials provides synchronization of the electrical and mechanical signals. Thus, Ca(2+) oscillations pace early embryonic heart cells and the ensuing activation of the Na(+)-Ca(2+) exchanger evokes small membrane depolarizations or action potentials.
Developmental changes in force-generating capacity and Ca 2+ sensitivity of contraction in murine hearts were correlated with changes in myosin heavy chain (MHC) and troponin (Tn) isoform
expression, ...using Triton-skinned fibres. The maximum Ca 2+ -activated isometric force normalized to the cross-sectional area ( F CSA ) increased mainly during embryogenesis and continued to increase at a slower rate until adulthood. During prenatal development,
F CSA increased about 5-fold from embryonic day (E)10.5 to E19.5, while the amount of MHC normalized to the amount of total protein
remained constant (from E13.5 to E19.5). This suggests that the development of structural organization of the myofilaments
during the embryonic and the fetal period may play an important role for the improvement of force generation. There was an
overall decrease of 0.5 pCa units in the Ca 2+ sensitivity of force generation from E13.5 to the adult, of which the main decrease (0.3 pCa units) occurred within a short
time interval, between E19.5 and 7 days after birth (7 days pn). Densitometric analysis of SDS-PAGE and Western blots revealed
that the major switches between troponin T (TnT) isoforms occur before E16.5, whereas the transition points of slow skeletal
troponin I (ssTnI) to cardiac TnI (cTnI) and of β-MHC to α-MHC both occur around birth, in temporal correlation with the main
decrease in Ca 2+ sensitivity. To test whether the changes in Ca 2+ sensitivity are solely based on Tn, the native Tn complex was replaced in fibres from E19.5 and adult hearts with fast skeletal
Tn complex (fsTn) purified from rabbit skeletal muscle. The difference in pre-replacement values of pCa 50 (âlog(Ca 2+ m â1 )) required for half-maximum force development) between E19.5 (6.05 ± 0.01) and adult fibres (5.64 ± 0.04) was fully abolished
after replacement with the exogenous skeletal Tn complex (pCa 50 = 6.12 ± 0.05 for both stages). This suggests that the major developmental changes in Ca 2+ sensitivity of skinned murine myocardium originate primarily from the switch of ssTnI to cTnI.
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