PITX2 gain-of-function mutation associated with atrial fibrillation alters mitochondrial activity in human iPSC atrial-like cardiomyocytes.

Atrial fibrillation (AF) is the most common cardiac arrhythmia worldwide; however, the underlying causes of AF initiation are still poorly understood, particularly because currently available models do not allow in distinguishing the initial causes from maladaptive remodeling that induces and perpetuates AF. Lately, the genetic background has been proven to be important in the AF onset. iPSC-derived cardiomyocytes, being patient- and mutation-specific, may help solve this diatribe by showing the initial cell-autonomous changes underlying the development of the disease. Transcription factor paired-like homeodomain 2 (PITX2) has been identified as a key regulator of atrial development/differentiation, and the PITX2 genomic locus has the highest association with paroxysmal AF. PITX2 influences mitochondrial activity, and alterations in either its expression or function have been widely associated with AF. In this work, we investigate the activity of mitochondria in iPSC-derived atrial cardiomyocytes (aCMs) obtained from a young patient (24 years old) with paroxysmal AF, carrying a gain-of-function mutation in PITX2 (rs138163892) and from its isogenic control (CTRL) in which the heterozygous point mutation has been reverted to WT. PITX2 aCMs show a higher mitochondrial content, increased mitochondrial activity, and superoxide production under basal conditions when compared to CTRL aCMs. However, increasing mitochondrial workload by FCCP or ß-adrenergic stimulation allows us to unmask mitochondrial defects in PITX2 aCMs, which are incapable of responding efficiently to the higher energy demand, determining ATP deficiency.

Human iPSC-Derived 3D Hepatic Organoids in a Miniaturized Dynamic Culture System.

The process of identifying and approving a new drug is a time-consuming and expensive procedure. One of the biggest issues to overcome is the risk of hepatotoxicity, which is one of the main reasons for drug withdrawal from the market. While animal models are the gold standard in preclinical drug testing, the translation of results into therapeutic intervention is often ambiguous due to interspecies differences in hepatic metabolism. The discovery of human induced pluripotent stem cells (hiPSCs) and their derivatives has opened new possibilities for drug testing. We used mesenchymal stem cells and hepatocytes both derived from hiPSCs, together with endothelial cells, to miniaturize the process of generating hepatic organoids. These organoids were then cultivated in vitro using both static and dynamic cultures. Additionally, we tested spheroids solely composed by induced hepatocytes. By miniaturizing the system, we demonstrated the possibility of maintaining the organoids, but not the spheroids, in culture for up to 1 week. This timeframe may be sufficient to carry out a hypothetical pharmacological test or screening. In conclusion, we propose that the hiPSC-derived liver organoid model could complement or, in the near future, replace the pharmacological and toxicological tests conducted on animals.

Generation of the induced pluripotent stem cell line UNIBSi017-A from an individual with cardiospondylocarpofacial syndrome and the MAP3K7 c.737-7A > G variant.

TAK1 is a serine threonine kinase that mediates signal transduction induced by TGFß and bone morphogenetic proteins, and controls a variety of cell functions by modulating the downstream activation of NF-kkB, JNK, and p38. Heterozygous variants in the coding MAP3K7 gene cause the cardiospondylocarpofacial syndrome, characterized by various abnormalities. Skin fibroblasts derived from a patient carrying the MAP3K7 c.737-7A>G heterozygous variant were reprogrammed using Sendai viral vector system carrying the Yamanaka factors. The generated induced pluripotent stem cells (iPSC) line retained the original genotype, expressed pluripotency markers, and differentiated into cells of the three germ layers.

EBF1 is expressed in pericytes and contributes to pericyte cell commitment.

Early B-cell factor-1 (EBF1) is a transcription factor with an important role in cell lineage specification and commitment during the early stage of cell maturation. Originally described during B-cell maturation, EBF1 was subsequently identified as a crucial molecule for proper cell fate commitment of mesenchymal stem cells into adipocytes, osteoblasts and muscle cells. In vessels, EBF1 expression and function have never been documented. Our data indicate that EBF1 is highly expressed in peri-endothelial cells in both tumor vessels and in physiological conditions. Immunohistochemistry, quantitative reverse transcription polymerase chain reaction (RT-qPCR) and fluorescence-activated cell sorting (FACS) analysis suggest that EBF1-expressing peri-endothelial cells represent bona fide pericytes and selectively express well-recognized markers employed in the identification of the pericyte phenotype (SMA, PDGFRß, CD146, NG2). This observation was also confirmed in vitro in human placenta-derived pericytes and in human brain vascular pericytes (HBVP). Of note, in accord with the key role of EBF1 in the cell lineage commitment of mesenchymal stem cells, EBF1-silenced HBVP cells showed a significant reduction in PDGFRß and CD146, but not CD90, a marker mostly associated with a prominent mesenchymal phenotype. Moreover, the expression levels of VEGF, angiopoietin-1, NG2 and TGF-ß, cytokines produced by pericytes during angiogenesis and linked to their differentiation and activation, were also significantly reduced. Overall, the data suggest a functional role of EBF1 in the cell fate commitment toward the pericyte phenotype.

A detailed characterization of the hyperpolarization-activated "funny" current (If) in human-induced pluripotent stem cell (iPSC)-derived cardiomyocytes with pacemaker activity.

Properties of the funny current (If) have been studied in several animal and cellular models, but so far little is known concerning its properties in human pacemaker cells. This work provides a detailed characterization of If in human-induced pluripotent stem cell (iPSC)-derived pacemaker cardiomyocytes (pCMs), at different time points. Patch-clamp analysis showed that If density did not change during differentiation; however, after day 30, it activates at more negative potential and with slower time constants. These changes are accompanied by a slowing in beating rate. If displayed the voltage-dependent block by caesium and reversed (Erev) at - 22 mV, compatibly with the 3:1 K+/Na+ permeability ratio. Lowering [Na+]o (30 mM) shifted the Erev to - 39 mV without affecting conductance. Increasing [K+]o (30 mM) shifted the Erev to - 15 mV with a fourfold increase in conductance. pCMs express mainly HCN4 and HCN1 together with the accessory subunits CAV3, KCR1, MiRP1, and SAP97 that contribute to the context-dependence of If. Autonomic agonists modulated the diastolic depolarization, and thus rate, of pCMs. The adrenergic agonist isoproterenol induced rate acceleration and a positive shift of If voltage-dependence (EC50 73.4 nM). The muscarinic agonists had opposite effects (Carbachol EC50, 11,6 nM). Carbachol effect was however small but it could be increased by pre-stimulation with isoproterenol, indicating low cAMP levels in pCMs. In conclusion, we demonstrated that pCMs display an If with the physiological properties expected by pacemaker cells and may thus represent a suitable model for studying human If-related sinus arrhythmias.

Simultaneously characterization of tumoral angiogenesis and vasculogenesis in stem cell-derived teratomas.

Tumor neovascularization may occur via both angiogenic and vasculogenic events. In order to investigate the vessel formation during tumor growth, we developed a novel experimental model that takes into account the differentiative and tumorigenic properties of Embryonic Stem cells (ESCs). Leukemia Inhibitory Factor-deprived murine ESCs were grafted on the top of the chick embryo chorionallantoic membrane (CAM) in ovo. Cell grafts progressively grew, forming a vascularized mass within 10 days. At this stage, the grafts are formed by cells with differentiative features representative of all three germ layers, thus originating teratomas, a germinal cell tumor. In addition, ESC supports neovascular events by recruiting host capillaries from surrounding tissue that infiltrates the tumor mass. Moreover, immunofluorescence studies demonstrate that perfused active blood vessels within the tumor are of both avian and murine origin because of the simultaneous occurrence of angiogenic and vasculogenic events. In conclusion, the chick embryo ESC/CAM-derived teratoma model may represent a useful approach to investigate both vasculogenic and angiogenic events during tumor growth and for the study of natural and synthetic modulators of the two processes.

Human iPSC modelling of a familial form of atrial fibrillation reveals a gain of function of If and ICaL in patient-derived cardiomyocytes.

AIMS: Atrial fibrillation (AF) is the most common type of cardiac arrhythmias, whose incidence is likely to increase with the aging of the population. It is considered a progressive condition, frequently observed as a complication of other cardiovascular disorders. However, recent genetic studies revealed the presence of several mutations and variants linked to AF, findings that define AF as a multifactorial disease. Due to the complex genetics and paucity of models, molecular mechanisms underlying the initiation of AF are still poorly understood. Here we investigate the pathophysiological mechanisms of a familial form of AF, with particular attention to the identification of putative triggering cellular mechanisms, using patient's derived cardiomyocytes (CMs) differentiated from induced pluripotent stem cells (iPSCs). METHODS AND RESULTS: Here we report the clinical case of three siblings with untreatable persistent AF whose whole-exome sequence analysis revealed several mutated genes. To understand the pathophysiology of this multifactorial form of AF we generated three iPSC clones from two of these patients and differentiated these cells towards the cardiac lineage. Electrophysiological characterization of patient-derived CMs (AF-CMs) revealed that they have higher beating rates compared to control (CTRL)-CMs. The analysis showed an increased contribution of the If and ICaL currents. No differences were observed in the repolarizing current IKr and in the sarcoplasmic reticulum calcium handling. Paced AF-CMs presented significantly prolonged action potentials and, under stressful conditions, generated both delayed after-depolarizations of bigger amplitude and more ectopic beats than CTRL cells. CONCLUSIONS: Our results demonstrate that the common genetic background of the patients induces functional alterations of If and ICaL currents leading to a cardiac substrate more prone to develop arrhythmias under demanding conditions. To our knowledge this is the first report that, using patient-derived CMs differentiated from iPSC, suggests a plausible cellular mechanism underlying this complex familial form of AF.

Generation and characterization of the human iPSC line IDISi001-A isolated from blood cells of a CADASIL patient carrying a NOTCH3 mutation.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common form of hereditary stroke disorder. It is caused by mutations in NOTCH3 that lead to progressive degeneration of the smooth muscle cells in blood vessels. There is currently no treatment for this disorder. We reprogrammed to pluripotency blood mononuclear cells isolated from a patient carrying a NOTCH3 mutation by using a commercially available non-integrating system. The success in the generation of this iPSC line (IDISi001-A) suggests that the NOTCH3 mutation did not limit cell reprogramming and offers an unprecedented opportunity for studying and modeling CADASIL pathology.

Generation of induced pluripotent stem cells (iPSC) from an atrial fibrillation patient carrying a KCNA5 p.D322H mutation.

Atrial fibrillation (AF) is the most common sustained arrhythmia associated with several cardiac risk factors, but increasing evidences indicated a genetic component. Indeed, genetic variations of the atrial specific KCNA5 gene have been identified in patients with early-onset lone AF. To investigate the molecular mechanisms underlying AF, we reprogrammed to pluripotency polymorphonucleated leukocytes isolated from the blood of a patient carrying a KCNA5 p.D322H mutation, using a commercially available non-integrating system. The generated iPSCs expressed pluripotency markers and differentiated toward cells belonging to the three embryonic germ layers. Moreover, the cells showed a normal karyotype and retained the p.D322H mutation.

Generation of induced pluripotent stem cells (iPSC) from an atrial fibrillation patient carrying a PITX2 p.M200V mutation.

Atrial fibrillation (AF) is the most common sustained arrhythmia associated with several cardiac risk factors, but increasing evidences indicated a genetic component. Indeed, genetic variations of the specific PITX2 gene have been identified in patients with early-onset AF. To investigate the molecular mechanisms underlying AF, we reprogrammed to pluripotency polymorphonucleated leukocytes isolated from the blood of a patient carrying a PITX2 p.M200V mutation, using a commercially available non-integrating expression system. The generated iPSCs expressed pluripotency markers and differentiated toward cells belonging to the three embryonic germ layers. Moreover, the cells showed a normal karyotype and retained the PITX2 p.M200V mutation.

Clinical potentials of human pluripotent stem cells.

Aging, injuries, and diseases can be considered as the result of malfunctioning or damaged cells. Regenerative medicine aims to restore tissue homeostasis by repairing or replacing cells, tissues, or damaged organs, by linking and combining different disciplines including engineering, technology, biology, and medicine. To pursue these goals, the discipline is taking advantage of pluripotent stem cells (PSCs), a peculiar type of cell possessing the ability to differentiate into every cell type of the body. Human PSCs can be isolated from the blastocysts and maintained in culture indefinitely, giving rise to the so-called embryonic stem cells (ESCs). However, since 2006, it is possible to restore in an adult cell a pluripotent ESC-like condition by forcing the expression of four transcription factors with the rejuvenating reprogramming technology invented by Yamanaka. Then the two types of PSC can be differentiated, using standardized protocols, towards the cell type necessary for the regeneration. Although the use of these derivatives for therapeutic transplantation is still in the preliminary phase of safety and efficacy studies, a lot of efforts are presently taking place to discover the biological mechanisms underlying genetic pathologies, by differentiating induced PSCs derived from patients, and new therapies by challenging PSC-derived cells in drug screening.

ELM: A New, Simple, and Economic Assay to Measure Motility of Lymphatic Endothelial Cells.

BACKGROUND: Relatively few attempts have been made to set up an assay that allows the measurement of lymphatic endothelial cells (LECs) motility. Nowadays, the most widely used methods involve adaptation of the Boyden chamber method or the wound scratch assay, both of them showing some limitations due to long and expensive setup and high variability. METHODS AND RESULTS: We propose a new, economic, and easy to setup LEC Motility (ELM) assay that will contribute to the study of lymphangiogenesis. The experimental setup consists of extending the coating of the flask with extracellular matrix (ECM) proteins also at the area opposite to the cap, where the LECs will be initially seeded at various densities. The day after, the flasks will be inclined at an angle of about 20° to cover the entire coated surface. Twenty-four hours later, flasks will be moved to the standard position, and the motility of the cells will be easily observed. Using the ELM assay, we were able to compare the motility rate of LECs isolated from different origins, or seeded on different substrates. CONCLUSION: We propose the use of a new method to evaluate the motility of LECs: the ELM assay. This cost-effective analysis has several advantages: It can be easily set up in any cell biology laboratory, can be carried out rapidly, and allows the monitoring of cellular motility for a long period.

Prediction of abdominal aortic aneurysm calcification by means of variation of high-sensitivity C-reactive protein.

OBJECTIVE: Abdominal aortic aneurysms are a major cause of death in developed countries, and thrombus and calcification of the aneurysm have been linked to increased complications. This study was conducted in order to identify the biochemical marker associated to the presence of intraluminal thrombus or calcification progression of the aneurysm. DESIGN: Several clinical laboratory parameters were measured in patients with abdominal aortic aneurysms, in particular those already demonstrated to be related to the pathology, such as lipoprotein (a), white blood cell count, fibrinogen and high-sensitivity C-reactive protein. Most of the patients were analysed for the presence of thrombus or aorta calcification using CT angiography. RESULTS: Unlike previous findings, we found no association between intraluminal thrombus formation and lipoprotein (a), but we evidenced that patients with lower grade of calcification tend to have higher plasma high-sensitivity C-reactive protein values compared with patients with a higher degree of calcification. Instead, no association was found with either white blood cell count or fibrinogen level. CONCLUSIONS: This study suggests that high-sensitivity C-reactive protein is a useful biomarker to assess the evolution of calcification and could be used in triaging patients to identify those who should undergo a rapid imaging, thus allowing prompt initiation of treatment or rule-out suspicious patients from non-essential imaging repetition.

Human derived cardiomyocytes: A decade of knowledge after the discovery of induced pluripotent stem cells.

Ten years ago Yamanaka's lab identified a way to reprogram terminally differentiated cells to a pluripotent state, similar to that of embryonic stem cell. This procedure opened the road for the generation of postmitotic human cells, that have completely lost the replication potential. The initial excitement waned when it was observed that the cells produced by this method are somehow immature and do not resemble the adult phenotype. In the absence of cellular markers that recognize the various maturation steps of induced pluripotent stem cell-derived human cardiomyocytes, we propose to follow their maturation looking at their electrophysiological profile. For this reason, we are first reviewing the most common methods of differentiation, from the preliminary complex procedures to the newly-identified two-step protocols and, second, we report the electrical characteristics of the cells, through electrophysiological analysis of ionic currents that give rise to the action potential. We are aware that each protocol leads to the generation of different cardiomyocyte precursors, thus suggesting the need for a wider standardization. The identification of the electrophysiological characteristics of the cells could help in identifying the type and the maturation stage of the obtained cardiomyocyte, thus compensating for the lack of specific markers. Developmental Dynamics 245:1145-1158, 2016. © 2016 Wiley Periodicals, Inc.

Using iPS Cells toward the Understanding of Parkinson's Disease.

Cellular reprogramming of somatic cells to human pluripotent stem cells (iPSC) represents an efficient tool for in vitro modeling of human brain diseases and provides an innovative opportunity in the identification of new therapeutic drugs. Patient-specific iPSC can be differentiated into disease-relevant cell types, including neurons, carrying the genetic background of the donor and enabling de novo generation of human models of genetically complex disorders. Parkinson's disease (PD) is the second most common age-related progressive neurodegenerative disease, which is mainly characterized by nigrostriatal dopaminergic (DA) neuron degeneration and synaptic dysfunction. Recently, the generation of disease-specific iPSC from patients suffering from PD has unveiled a recapitulation of disease-related cell phenotypes, such as abnormal α-synuclein accumulation and alterations in autophagy machinery. The use of patient-specific iPSC has a remarkable potential to uncover novel insights of the disease pathogenesis, which in turn will open new avenues for clinical intervention. This review explores the current Parkinson's disease iPSC-based models highlighting their role in the discovery of new drugs, as well as discussing the most challenging limitations iPSC-models face today.

Cardiac disease modeling using induced pluripotent stem cell-derived human cardiomyocytes.

Causative mutations and variants associated with cardiac diseases have been found in genes encoding cardiac ion channels, accessory proteins, cytoskeletal components, junctional proteins, and signaling molecules. In most cases the functional evaluation of the genetic alteration has been carried out by expressing the mutated proteins in in-vitro heterologous systems. While these studies have provided a wealth of functional details that have greatly enhanced the understanding of the pathological mechanisms, it has always been clear that heterologous expression of the mutant protein bears the intrinsic limitation of the lack of a proper intracellular environment and the lack of pathological remodeling. The results obtained from the application of the next generation sequencing technique to patients suffering from cardiac diseases have identified several loci, mostly in non-coding DNA regions, which still await functional analysis. The isolation and culture of human embryonic stem cells has initially provided a constant source of cells from which cardiomyocytes (CMs) can be obtained by differentiation. Furthermore, the possibility to reprogram cellular fate to a pluripotent state, has opened this process to the study of genetic diseases. Thus induced pluripotent stem cells (iPSCs) represent a completely new cellular model that overcomes the limitations of heterologous studies. Importantly, due to the possibility to keep spontaneously beating CMs in culture for several months, during which they show a certain degree of maturation/aging, this approach will also provide a system in which to address the effect of long-term expression of the mutated proteins or any other DNA mutation, in terms of electrophysiological remodeling. Moreover, since iPSC preserve the entire patients' genetic context, the system will help the physicians in identifying the most appropriate pharmacological intervention to correct the functional alteration. This article summarizes the current knowledge of cardiac genetic diseases modelled with iPSC.

Induced pluripotent stem cell-based studies of Parkinson's disease: challenges and promises.

A critical step in the development of effective therapeutics to treat Parkinson's disease (PD) is the identification of molecular pathogenic mechanisms underlying this chronically progressive neurodegenerative disease. However, while animal models have provided valuable information about the molecular basis of PD, the lack of faithful cellular and animal models that recapitulate human pathophysiology is delaying the development of new therapeutics. The reprogramming of somatic cells to induced pluripotent stem cells (iPSC) using delivery of defined combinations of transcription factors is a groundbreaking discovery that opens great opportunities for modeling human diseases, including PD, since iPSC can be generated from patients and differentiated into disease-relevant cell types, which would capture the patients' genetic complexity. Furthermore, human iPSC-derived neuronal models offer unprecedented access to early stages of the disease, allowing the investigation of the events that initiate the pathologic process in PD. Recently, human iPSC-derived neurons from patients with familial and sporadic PD have been generated and importantly they recapitulate some PD-related cell phenotypes, including abnormal α-synuclein accumulation in vitro, and alterations in the autophagy machinery. This review highlights the current PD iPSC-based models and discusses the potential future research directions of this field.

Ascorbic acid rescues cardiomyocyte development in Fgfr1(-/-) murine embryonic stem cells.

Fibroblast growth factor receptor 1 (Fgfr1) gene knockout impairs cardiomyocyte differentiation in murine embryonic stem cells (mESC). Here, various chemical compounds able to enhance cardiomyocyte differentiation in mESC [including dimethylsulfoxide, ascorbic acid (vitC), free radicals and reactive oxygen species] were tested for their ability to rescue the cardiomyogenic potential of Fgfr1(-/-) mESC. Among them, only the reduced form of vitC, l-ascorbic acid, was able to recover beating cell differentiation in Fgfr1(-/-) mESC. The appearance of contracting cells was paralleled by the expression of early and late cardiac gene markers, thus suggesting their identity as cardiomyocytes. In the attempt to elucidate the mechanism of action of vitC on Fgfr1(-/-) mESC, we analyzed several parameters related to the intracellular redox state, such as reactive oxygen species content, Nox4 expression, and superoxide dismutase activity. The results did not show any relationship between the antioxidant capacity of vitC and cardiomyocyte differentiation in Fgfr1(-/-) mESC. No correlation was found also for the ability of vitC to modulate the expression of pluripotency genes. Then, we tested the hypothesis that vitC was acting as a prolyl hydroxylase cofactor by maintaining iron in a reduced state. We first analyze hypoxia inducible factor (HIF)-1α mRNA and protein levels that were found to be slightly upregulated in Fgfr1(-/-) cells. We treated mESC with Fe(2+) or the HIF inhibitor CAY10585 during the first phases of the differentiation process and, similar to vitC, the two compounds were able to rescue cardiomyocyte formation in Fgfr1(-/-) mESC, thus implicating HIF-1α modulation in Fgfr1-dependent cardiomyogenesis.

Sphingosine-1-phosphate receptor-1 controls venous endothelial barrier integrity in zebrafish.

OBJECTIVE: Endothelial sphingosine-1-phosphate (S1P) receptor-1 (S1P(1)) affects different vascular functions, including blood vessel maturation and permeability. Here, we characterized the role of the zS1P(1) ortholog in vascular development in zebrafish. METHODS AND RESULTS: zS1P(1) is expressed in dorsal aorta and posterior cardinal vein of zebrafish embryos at 24 to 30 hours postfertilization. zS1P(1) downregulation by antisense morpholino oligonucleotide injection causes early pericardial edema, lack of blood circulation, alterations of posterior cardinal vein structure, and late generalized edema. Also, zS1P(1) morphants are characterized by downregulation of vascular endothelial cadherin (VE-cadherin) and Eph receptor EphB4a expression and by disorganization of zonula occludens 1 junctions in posterior cardinal vein endothelium, with no alterations of dorsal aorta endothelium. VE-cadherin knockdown results in similar vascular alterations, whereas VE-cadherin overexpression is sufficient to rescue venous vascular integrity defects and EphB4a downregulation in zS1P(1) morphants. Finally, S1P(1) small interfering RNA transfection and the S1P(1) antagonist (R)-3-amino-(3-hexylphenylamino)-4-oxobutylphosphonic acid (W146) cause EPHB4 receptor down-modulation in human umbilical vein endothelial cells and the assembly of zonula occludens 1 intercellular contacts is prevented by the EPHB4 antagonist TNYL-RAW peptide in these cells. CONCLUSIONS: The data demonstrate a nonredundant role of zS1P(1) in the regulation of venous endothelial barrier in zebrafish and identify a S1P(1)/VE-cadherin/EphB4a genetic pathway that controls venous vascular integrity.