CD151 expression marks atrial- and ventricular- differentiation from human induced pluripotent stem cells

Current differentiation protocols for human induced pluripotent stem cells (hiPSCs) produce heterogeneous cardiomyocytes (CMs). Although chamber-specific CM selection using cell surface antigens enhances biomedical applications, a cell surface marker that accurately distinguishes between hiPSC-derived atrial CMs (ACMs) and ventricular CMs (VCMs) has not yet been identified. We have developed an approach for obtaining functional hiPSC-ACMs and -VCMs based on CD151 expression. For ACM differentiation, we found that ACMs are enriched in the CD151low population and that CD151 expression is correlated with the expression of Notch4 and its ligands. Furthermore, Notch signaling inhibition followed by selecting the CD151low population during atrial differentiation leads to the highly efficient generation of ACMs as evidenced by gene expression and electrophysiology. In contrast, for VCM differentiation, VCMs exhibiting a ventricular-related gene signature and uniform action potentials are enriched in the CD151high population. Our findings enable the production of high-quality ACMs and VCMs appropriate for hiPSC-derived chamber-specific disease models and other applications.

Am80, a retinoic acid receptor agonist, activates the cardiomyocyte cell cycle and enhances engraftment in the heart

Human induced pluripotent stem cell-derived (hiPSC) cardiomyocytes are a promising source for regenerative therapy. To realize this therapy, however, their engraftment potential after their injection into the host heart should be improved. Here, we established an efficient method to analyze the cell cycle activity of hiPSC cardiomyocytes using a fluorescence ubiquitination-based cell cycle indicator (FUCCI) system. In vitro high-throughput screening using FUCCI identified a retinoic acid receptor (RAR) agonist, Am80, as an effective cell cycle activator in hiPSC cardiomyocytes. The transplantation of hiPSC cardiomyocytes treated with Am80 before the injection significantly enhanced the engraftment in damaged mouse heart for 6 months. Finally, we revealed that the activation of endogenous Wnt pathways through both RARA and RARB underlies the Am80-mediated cell cycle activation. Collectively, this study highlights an efficient method to activate cell cycle in hiPSC cardiomyocytes by Am80 as a means to increase the graft size after cell transplantation into a damaged heart.

Novel Calmodulin Variant p.E46K Associated With Severe Catecholaminergic Polymorphic Ventricular Tachycardia Produces Robust Arrhythmogenicity in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes

BACKGROUND

CaM (calmodulin) is a ubiquitously expressed, multifunctional Ca²⁺ sensor protein that regulates numerous proteins. Recently, CaM missense variants have been identified in patients with malignant inherited arrhythmias, such as long QT syndrome and catecholaminergic polymorphic ventricular tachycardia (CPVT). However, the exact mechanism of CaM-related CPVT in human cardiomyocytes remains unclear. In this study, we sought to investigate the arrhythmogenic mechanism of CPVT caused by a novel variant using human induced pluripotent stem cell (iPSC) models and biochemical assays.

METHODS

We generated iPSCs from a patient with CPVT bearing CALM2 p.E46K. As comparisons, we used 2 control lines including an isogenic line, and another iPSC line from a patient with long QT syndrome bearing CALM2 p.N98S (also reported in CPVT). Electrophysiological properties were investigated using iPSC-cardiomyocytes. We further examined the RyR2 (ryanodine receptor 2) and Ca²⁺ affinities of CaM using recombinant proteins.

RESULTS

We identified a novel de novo heterozygous variant, CALM2 p.E46K, in 2 unrelated patients with CPVT accompanied by neurodevelopmental disorders. The E46K-cardiomyocytes exhibited more frequent abnormal electrical excitations and Ca²⁺ waves than the other lines in association with increased Ca²⁺ leakage from the sarcoplasmic reticulum via RyR2. Furthermore, the [³H]ryanodine binding assay revealed that E46K-CaM facilitated RyR2 function especially by activating at low [Ca²⁺] levels. The real-time CaM-RyR2 binding analysis demonstrated that E46K-CaM had a 10-fold increased RyR2 binding affinity compared with wild-type CaM which may account for the dominant effect of the mutant CaM. Additionally, the E46K-CaM did not affect CaM-Ca²⁺ binding or L-type calcium channel function. Finally, antiarrhythmic agents, nadolol and flecainide, suppressed abnormal Ca²⁺ waves in E46K-cardiomyocytes.

CONCLUSIONS

We, for the first time, established a CaM-related CPVT iPSC-CM model which recapitulated severe arrhythmogenic features resulting from E46K-CaM dominantly binding and facilitating RyR2. In addition, the findings in iPSC-based drug testing will contribute to precision medicine.

Disrupted CaV1.2 selectivity causes overlapping long QT and Brugada syndrome phenotypes in the CACNA1C-E1115K iPS cell model

BACKGROUND

A missense mutation in the α1c subunit of voltage-gated L-type Ca²⁺ channel-coding CACNA1C-E1115K, located in the Ca²⁺ selectivity site, causes a variety of arrhythmogenic phenotypes.

OBJECTIVE

We aimed to investigate the electrophysiological features and pathophysiological mechanisms of CACNA1C-E1115K in patient-specific induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs).

METHODS

We generated iPSCs from a patient carrying heterozygous CACNA1C-E1115K with overlapping phenotypes of long QT syndrome, Brugada syndrome, and mild cardiac dysfunction. Electrophysiological properties were investigated using iPSC-CMs. We used iPSCs from a healthy individual and an isogenic iPSC line corrected using CRISPR-Cas9-mediated gene editing as controls. A mathematical E1115K-CM model was developed using a human ventricular cell model.

RESULTS

Patch-clamp analysis revealed that E1115K-iPSC-CMs exhibited reduced peak Ca²⁺ current density and impaired Ca²⁺ selectivity with an increased permeability to monovalent cations. Consequently, E1115K-iPSC-CMs showed decreased action potential plateau amplitude, longer action potential duration (APD), and a higher frequency of early afterdepolarization compared with controls. In optical recordings examining the antiarrhythmic drug effect, late Na⁺ channel current (I_NaL) inhibitors (mexiletine and GS-458967) shortened APDs specifically in E1115K-iPSC-CMs. The AP-clamp using a voltage command obtained from E1115K-iPSC-CMs with lower action potential plateau amplitude and longer APD confirmed the upregulation of I_NaL. An in silico study recapitulated the in vitro electrophysiological properties.

CONCLUSION

Our iPSC-based analysis in CACNA1C-E1115K with disrupted Ca_V1.2 selectivity demonstrated that the aberrant currents through the mutant channels carried by monovalent cations resulted in specific action potential changes, which increased endogenous I_NaL, thereby synergistically contributing to the arrhythmogenic phenotype.

Expression dynamics of HAND1/2 in in vitro human cardiomyocyte differentiation

Hand1 and Hand2 are transcriptional factors, and knockout mice of these genes show left and right ventricular hypoplasia, respectively. However, their function and expression in human cardiogenesis are not well studied. To delineate their expressions and assess their functions in human cardiomyocytes (CMs) in vitro, we established two triple-reporter human induced pluripotent stem cell lines that express HAND1^mCherry, HAND2^EGFP and either MYH6-driven iRFP670 or tagBFP constitutively and investigated their expression dynamics during cardiac differentiation. On day 5 of the differentiation, HAND1 expression marked cardiac progenitor cells. We profiled the CM subpopulations on day 20 with RNA sequencing and found that mCherry+ CMs showed higher proliferative ability than mCherry− CMs and identified a gene network of LEF1, HAND1, and HAND2 to regulate proliferation in CMs. Finally, we identified CD105 as a surface marker of highly proliferative CMs.

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Expression of HAND1 marks cardiovascular progenitor cells

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LEF1 is a key regulator of proliferating cardiomyocytes

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CD105 expression marks highly proliferative cardiomyocytes

Stroke, systemic embolism and bleeding rate in non-valvular atrial fibrillation patients without anticoagulation on the real world data in Japan

Background

Anticoagulant therapy is recommended in patients with non-valvular atrial fibrillation (NVAF) for those with CHADS2 ≥2. However, there have been significant number of subjects with CHADS2 ≥2 who receive no anticoagulation. Most of reported real world data have been collected mainly before wide spread use of DOAC. This study evaluated the clinical outcome of no anticoagulant drug therapy in NVAF.

Methods

This study is a non-interventional, observational, retrospective cohort study of NVAF patients in Mie-LIP Database, which is a regional clinical database joining 1 university hospital and 8 general hospitals in Mie prefecture in Japan. Patient enrolment was conducted from 1st Jan. 2016 to 31st Dec. 2018. The primary outcome events are ischemic stroke, systemic embolism, and bleeding events (bleeding to need a blood transfusion, intracranial bleeding, intraocular bleeding, and gastrointestinal bleeding).

Results

7001 patients were included in the current analysis, 2550 patients, 36.4% were treated without any anticoagulant drug therapy. Table 1 shows patients with no anticoagulant drug therapy, mean age was 75.4 years and 42.2% of patients were female. The most frequent comorbidities included hypertension (50.0%), diabetes mellitus (28.2%), heart failure (14.0%), ischemic stroke (12.7%), vascular disease (14.4%) respectively. The annual incidence of ischemic stroke, systemic embolism per 100 person-years is 3.7, and that in each CHADS2 group is 0: 1.4, 1: 1.4, 2: 3.2, 3–6: 8, respectively in Figure 1. The annual incidence of bleeding events is 1.5, and that in each CHADS2 group is 0: 0.7, 1: 1.0, 2: 1.2, 3–6: 2.9, respectively.

Conclusions

Approximately one-thirds of subjects have not received any anticoagulation in the modern DOAC in daily clinical practice in Japan. The rate of ischemic stroke and systemic embolism increased by CHADS2. Stroke or SEE rate was very low in subjects with CHADS2 ≤1, supporting no indication of anticoagulation in current guidelines. Regarding subjects with CHADS2>2, considering the higher risk of stroke, use of anticoagulant drug therapy is recommended.

Funding Acknowledgement

Type of funding source: None

Propranolol Attenuates Late Sodium Current in a Long QT Syndrome Type 3-Human Induced Pluripotent Stem Cell Model

Background

Long QT syndrome type 3 (LQT3) is caused by gain-of-function mutations in the SCN5A gene, which encodes the α subunit of the cardiac voltage-gated sodium channel. LQT3 patients present bradycardia and lethal arrhythmias during rest or sleep. Further, the efficacy of β-blockers, the drug used for their treatment, is uncertain. Recently, a large multicenter LQT3 cohort study demonstrated that β-blocker therapy reduced the risk of life-threatening cardiac events in female patients; however, the detailed mechanism of action remains unclear.

Objectives

This study aimed to establish LQT3-human induced pluripotent stem cells (hiPSCs) and to investigate the effect of propranolol in this model.

Method

An hiPSCs cell line was established from peripheral blood mononuclear cells of a boy with LQT3 carrying the SCN5A-N1774D mutation. He had suffered from repetitive torsades de pointes (TdPs) with QT prolongation since birth (QTc 680 ms), which were effectively treated with propranolol, as it suppressed lethal arrhythmias. Furthermore, hiPSCs were differentiated into cardiomyocytes (CMs), on which electrophysiological functional assays were performed using the patch-clamp method.

Results

N1774D-hiPSC-CMs exhibited significantly prolonged action potential durations (APDs) in comparison to those of the control cells (N1774D: 440 ± 37 ms vs. control: 272 ± 22 ms; at 1 Hz pacing; p < 0.01). Furthermore, N1774D-hiPSC-CMs presented gain-of-function features: a hyperpolarized shift of steady-state activation and increased late sodium current compared to those of the control cells. 5 μM propranolol shortened APDs and inhibited late sodium current in N1774D-hiPSC-CMs, but did not significantly affect in the control cells. In addition, even in the presence of intrapipette guanosine diphosphate βs (GDPβs), an inhibitor of G proteins, propranolol reduced late sodium current in N1774D cells. Therefore, these results suggested a unique inhibitory effect of propranolol on late sodium current unrelated to β-adrenergic receptor block in N1774D-hiPSC-CMs.

Conclusion

We successfully recapitulated the clinical phenotype of LQT3 using patient-derived hiPSC-CMs and determined that the mechanism, by which propranolol inhibited the late sodium current, was independent of β-adrenergic receptor signaling pathway.

The cooling mechanism of minuscule ribbed surfaces

One reason human beings wear stockings is to warm their legs. Ordinary textile materials are thermally insulative, which prevents body’s heat from dissipating. In contrary to this common sense, it was discovered that some knitted stockings made up of them permanently promote heat release and cool body. This non-intuitive phenomenon emerges when micro-size yarns are knitted to form wide spacing between neighboring yarns. However, the reason why they cool body was unclear because conventional principles of cooling garments cannot account for it. Here, in the basis of fluid-solid conjugate heat transfer analysis of natural convection, we have clarified the cooling mechanism originates from relative relationship between their geometric structure, a periodic alignment of minuscule ribs, and thermal boundary layer. Our novel finding revealed that sufficiently small ribs on the surface are exposed to steep temperature gradient within thermal boundary layer. Thereby, thermal conduction via ribs is enhanced complementarily as they are separated to guide cooler flow onto the surface. Our study provides a general insight into understanding permanent cooling mechanism on micro-size ribbed surfaces in contrast to conventional theory for heat sink, which is applicable not only to other clothes, but also to artificial devices or natural structures.

Targeted Disruption of HLA Genes via CRISPR-Cas9 Generates iPSCs with Enhanced Immune Compatibility

Induced pluripotent stem cells (iPSCs) have strong potential in regenerative medicine applications; however, immune rejection caused by HLA mismatching is a concern. B2M gene knockout and HLA-homozygous iPSC stocks can address this issue, but the former approach may induce NK cell activity and fail to present antigens, and it is challenging to recruit rare donors for the latter method. Here, we show two genome-editing strategies for making immunocompatible donor iPSCs. First, we generated HLA pseudo-homozygous iPSCs with allele-specific editing of HLA heterozygous iPSCs. Second, we generated HLA-C-retained iPSCs by disrupting both HLA-A and -B alleles to suppress the NK cell response while maintaining antigen presentation. HLA-C-retained iPSCs could evade T cells and NK cells in vitro and in vivo. We estimated that 12 lines of HLA-C-retained iPSCs combined with HLA-class II knockout are immunologically compatible with >90% of the world's population, greatly facilitating iPSC-based regenerative medicine applications.

Identification of patterns of factors preceding severe or life-threatening asthma exacerbations in a nationwide study

BACKGROUND

Reducing near-fatal asthma exacerbations is a critical problem in asthma management.

OBJECTIVES

To determine patterns of factors preceding asthma exacerbations in a real-world setting.

METHODS

In a nationwide prospective study of 190 patients who had experienced near-fatal asthma exacerbation, cluster analysis was performed using asthma symptoms over the 2-week period before admission.

RESULTS

Three distinct clusters of symptoms were defined employing the self-reporting of a visual analogue scale. Cluster A (42.1%): rapid worsening within 7.4 hours from moderate attack to admission, young to middle-aged patients with low Body mass index and tendency to depression who had stopped anti-asthma medications, smoked, and hypersensitive to environmental triggers and furred pets. Cluster B (40.0%): fairly rapid worsening within 48 hours, mostly middle-aged and older, relatively good inhaled corticosteroid (ICS) or ICS/long-acting beta-agonist (LABA) compliance, and low perception of dyspnea. Cluster C (17.9%): slow worsening over 10 days before admission, high perception of dyspnea, smokers, and chronic daily mild-moderate symptoms. There were no differences in overuse of short-acting beta-agonists, baseline asthma severity, or outcomes after admission for patients in these 3 clusters.

CONCLUSION

To reduce severe or life-threatening asthma exacerbation, personalized asthma management plans should be considered for each cluster. Improvement of ICS and ICS/LABA compliance and cessation of smoking are important in cluster A. To compensate for low perception of dyspnea, asthma monitoring of peak expiratory flow rate and/or exhaled nitric oxide would be useful for patients in cluster B. Avoidance of environmental triggers, increase usual therapy, or new anti-type 2 response-targeted therapies should be considered for cluster C.

Treatment with Bifemelane for Optic Nerve Damage following High Intraocular Pressure in Rat Eyes

This study found that pretreatment with 4-(o-benzylphenoxy)-N- methylbuty-lamine hydrochloride (bifemelane hydrochloride, Celeport) reduced ischemia-reperfusion injury in rat eyes. Bifemelane (25 mg/kg) was injected intraperitoneally 30 minutes before an ischemic insult, then acute ischemia of the retina and optic disc was induced by increasing intraocular pressure to 110 mmHg for 45 minutes. After one week, the axonal count of the optic nerve was investigated using electron microscopy. The control group consisted of vehicle-treated eyes which received normal saline. The axon count was 93.4 +/- 7.9 for the bifemelane treated group, and 79.2 +/- 6.4 for the controls. The axon count in the treated group was significantly higher. These results suggest that bifemelane, which prevents cerebral nerve cell damage from ischemia, can reduce ischemic retinal nerve cell injury.

A Heparin-coated Circuit Maintains Platelet Aggregability in Response to Shear Stress in an In Vitro Model of Cardiopulmonary Bypass

Alterations in platelet aggregability may play a role in the pathogenesis of qualitative platelet defects associated with cardiopulmonary bypass (CPB). We circulated fresh heparinized whole blood through tubing sets coated with heparin (C group, n = 10) and through non-coated sets (N group, n = 10) as a simulated CPB circuit. Shear stress (108 dyne/cm2)-induced platelet aggregation (hSIPA), plasma von Willebrand factor (vWF) activity and platelet glycoprotein (GP) Ib expression were measured, before, during, and after this in vitro set up of circulation. In the two groups, the extent of hSIPA significantly decreased during circulation and was partially restored after circulation. Decreases in the extent of hSIPA were significantly less with use of heparin-coated circuits. There was an equivalent reduction in plasma vWF activity, in the two groups. Expression of platelet surface GP Ib decreased significantly during circulation and recovered after circulation. Reduction of surface GP Ib expression during circulation was significantly less in the C group than that in the N group. Decrease in surface GP Ib expression correlated (r = 0.88 in either group) with the magnitude of hSIPA, in the two groups. The progressive removal of surface GP Ib was mainly attributed to redistribution of GP Ib from the membrane skeleton into the cytoskeleton. Our observations suggest that use of heparin-coated circuits partly blocks the reduction of hSIPA, as a result of a lesser degree of redistribution of GP Ib.

Myotonic dystrophy type 1 patient-derived iPSCs for the investigation of CTG repeat instability

Myotonic dystrophy type 1 (DM1) is an autosomal-dominant multi-system disease caused by expanded CTG repeats in dystrophia myotonica protein kinase (DMPK). The expanded CTG repeats are unstable and can increase the length of the gene with age, which worsens the symptoms. In order to establish a human stem cell system suitable for the investigation of repeat instability, DM1 patient-derived iPSCs were generated and differentiated into three cell types commonly affected in DM1, namely cardiomyocytes, neurons and myocytes. Then we precisely analysed the CTG repeat lengths in these cells. Our DM1-iPSCs showed a gradual lengthening of CTG repeats with unchanged repeat distribution in all cell lines depending on the passage numbers of undifferentiated cells. However, the average CTG repeat length did not change significantly after differentiation into different somatic cell types. We also evaluated the chromatin accessibility in DM1-iPSCs using ATAC-seq. The chromatin status in DM1 cardiomyocytes was closed at the DMPK locus as well as at SIX5 and its promoter region, whereas it was open in control, suggesting that the epigenetic modifications may be related to the CTG repeat expansion in DM1. These findings may help clarify the role of repeat instability in the CTG repeat expansion in DM1.

Single-channel Recordings of TREK-1 K+ Channels in Periodontal Ligament Fibroblasts

The periodontal ligament (PDL) works as a suspensory ligament when external mechanical stress is placed on the teeth. PDL fibroblasts, the principal cells in the PDL, are responsible for many PDL functions. We hypothesized that mechanosensitive ion channels are present in human PDL fibroblasts, which are capable of responding to mechanical stress during normal function of the tissue. Using patch-clamp techniques, we detected mechanosensitive TREK-1 K+ channels (a member of the two-pore-domain K+ channel family), whose single-channel conductance was 104 pS in symmetrical K+-rich solutions. The open probability of the channel was low in the quiescent state, but it was strongly increased by the induction of membrane stretch. Arachidonic acid also enhanced the channel activity. RT-PCR and immunocytochemical observations showed the expression of TREK-1 K+ channels in PDL fibroblasts. The results suggest that the activation of TREK-1 K+ channels by masticatory stress contributes to the hyperpolarization of PDL fibroblasts.

Epigenetic Variation between Human Induced Pluripotent Stem Cell Lines Is an Indicator of Differentiation Capacity

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.

Severe or life-threatening asthma exacerbation: patient heterogeneity identified by cluster analysis

BACKGROUND

Severe or life-threatening asthma exacerbation is one of the worst outcomes of asthma because of the risk of death. To date, few studies have explored the potential heterogeneity of this condition.

OBJECTIVES

To examine the clinical characteristics and heterogeneity of patients with severe or life-threatening asthma exacerbation.

METHODS

This was a multicentre, prospective study of patients with severe or life-threatening asthma exacerbation and pulse oxygen saturation < 90% who were admitted to 17 institutions across Japan. Cluster analysis was performed using variables from patient- and physician-orientated structured questionnaires.

RESULTS

Analysis of data from 175 patients with severe or life-threatening asthma exacerbation revealed five distinct clusters. Cluster 1 (n = 27) was younger-onset asthma with severe symptoms at baseline, including limitation of activities, a higher frequency of treatment with oral corticosteroids and short-acting beta-agonists, and a higher frequency of asthma hospitalizations in the past year. Cluster 2 (n = 35) was predominantly composed of elderly females, with the highest frequency of comorbid, chronic hyperplastic rhinosinusitis/nasal polyposis, and a long disease duration. Cluster 3 (n = 40) was allergic asthma without inhaled corticosteroid use at baseline. Patients in this cluster had a higher frequency of atopy, including allergic rhinitis and furred pet hypersensitivity, and a better prognosis during hospitalization compared with the other clusters. Cluster 4 (n = 34) was characterized by elderly males with concomitant chronic obstructive pulmonary disease (COPD). Although cluster 5 (n = 39) had very mild symptoms at baseline according to the patient questionnaires, 41% had previously been hospitalized for asthma.

CONCLUSIONS & CLINICAL RELEVANCE

This study demonstrated that significant heterogeneity exists among patients with severe or life-threatening asthma exacerbation. Differences were observed in the severity of asthma symptoms and use of inhaled corticosteroids at baseline, and the presence of comorbid COPD. These findings may contribute to a deeper understanding and better management of this patient population.

Sall1 transiently marks undifferentiated heart precursors and regulates their fate

Cardiac progenitor cells (CPCs) are a crucial source of cells in cardiac development and regeneration. However, reported CPCs are heterogeneous, and no gene has been identified to transiently mark undifferentiated CPCs throughout heart development. Here we show that Spalt-like gene 1 (Sall1), a zing-finger transcription factor, is expressed in undifferentiated CPCs giving rise to both left and right ventricles. Sall1 was transiently expressed in precardiac mesoderm contributing to the first heart field (left ventricle precursors) but not in the field itself. Similarly, Sall1 expression was maintained in the second heart field (outflow tract/right ventricle precursors) but not in cardiac cells. In vitro, high levels of Sall1 at mesodermal stages enhanced cardiomyogenesis, whereas its continued expression suppressed cardiac differentiation. Our study demonstrates that Sall1 marks CPCs in an undifferentiated state and regulates cardiac differentiation. These findings provide fundamental insights into CPC maintenance, which can be instrumental for CPC-based regenerative medicine.

Enhanced engraftment, proliferation, and therapeutic potential in heart using optimized human iPSC-derived cardiomyocytes

Human pluripotent stem cell-derived cardiomyocytes (CMs) are a promising tool for cardiac cell therapy. Although transplantation of induced pluripotent stem cell (iPSC)-derived CMs have been reported in several animal models, the treatment effect was limited, probably due to poor optimization of the injected cells. To optimize graft cells for cardiac reconstruction, we compared the engraftment efficiency of intramyocardially-injected undifferentiated-iPSCs, day 4 mesodermal cells, and day 8, day 20, and day 30 purified iPSC-CMs after initial differentiation by tracing the engraftment ratio (ER) using in vivo bioluminescence imaging. This analysis revealed the ER of day 20 CMs was significantly higher compared to other cells. Transplantation of day 20 CMs into the infarcted hearts of immunodeficient mice showed good engraftment, and echocardiography showed significant functional improvement by cell therapy. Moreover, the imaging signal and ratio of Ki67-positive CMs at 3 months post injection indicated engrafted CMs proliferated in the host heart. Although this graft growth reached a plateau at 3 months, histological analysis confirmed progressive maturation from 3 to 6 months. These results suggested that day 20 CMs had very high engraftment, proliferation, and therapeutic potential in host mouse hearts. They also demonstrate this model can be used to track the fate of transplanted cells over a long time.