Mitigation of Stress-induced Structural Remodeling and Functional Deficiency in iPSC-CMs with PLN R9C Mutation by Promoting Autophagy

Background

Phospholamban (PLN) is a key regulator of cardiac function connecting adrenergic signaling and calcium homeostasis. The R9C mutation of PLN is known to cause early onset dilated cardiomyopathy (DCM) and premature death, yet the detailed mechanisms underlie the pathologic remodeling process are not well defined in human cardiomyocytes. The aim of this study is to unravel the role of PLN R9C in DCM and identify potential therapeutic targets.

Methods

PLN R9C knock-in (KI) and patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) were generated and comprehensively examined for their expression profile, contractile function, and cellular signaling under both baseline conditions and following functional challenges.

Results

PLN R9C KI iPSC-CMs exhibited near-normal morphology and calcium handling, slightly increased contractility, and an attenuated response to β-adrenergic activation compared to wild-type (WT) cells. However, treatment with a maturation medium (MM) has induced fundamentally different remodeling in the two groups: while it improved the structural integrity and functional performance of WT cells, the same treatment result in sarcomere disarrangement, calcium handling deficiency, and further disrupted adrenergic signaling in PLN R9C KI cells. To understand the mechanism, transcriptomic analysis showed the enrichment of protein homeostasis signaling pathways specifically in PLN R9C KI cells in response to the MM treatment and increased contractile demands. Further studies also indicated elevated ROS levels, interrupted autophagic flux, and increased pentamer PLN aggregation in functionally challenged KI cells. These results were further confirmed in patient-specific iPSC-CM models, suggesting that functional stresses exacerbate the deficiencies in PLN R9C cells through disrupting protein homeostasis. Indeed, treating stressed patient cells with autophagy-accelerating reagents, such as metformin and rapamycin, has restored autophagic flux, mitigated sarcomere disarrangement, and partially rescued β-adrenergic signaling and cardiac function.

Conclusions

PLN R9C leads to a mild increase of calcium recycling and contractility. Functional challenges further enhanced contractile and proteostasis stress, leading to autophagic overload, structural remodeling, and functional deficiencies in PLN R9C cardiomyocytes. Activation of autophagy signaling partially rescues these effects, revealing a potential therapeutic target for DCM patients with the PLN R9C mutation.

Graphic abstracts

A graphic abstract is available for this article.

Artificial intelligence predictive analytics in heart failure: results of the pilot phase of a pragmatic randomized clinical trial

OBJECTIVES

We conducted an implementation planning process during the pilot phase of a pragmatic trial, which tests an intervention guided by artificial intelligence (AI) analytics sourced from noninvasive monitoring data in heart failure patients (LINK-HF2).

MATERIALS AND METHODS

A mixed-method analysis was conducted at 2 pilot sites. Interviews were conducted with 12 of 27 enrolled patients and with 13 participating clinicians. iPARIHS constructs were used for interview construction to identify workflow, communication patterns, and clinician's beliefs. Interviews were transcribed and analyzed using inductive coding protocols to identify key themes. Behavioral response data from the AI-generated notifications were collected.

RESULTS

Clinicians responded to notifications within 24 hours in 95% of instances, with 26.7% resulting in clinical action. Four implementation themes emerged: (1) High anticipatory expectations for reliable patient communications, reduced patient burden, and less proactive provider monitoring. (2) The AI notifications required a differential and tailored balance of trust and action advice related to role. (3) Clinic experience with other home-based programs influenced utilization. (4) Responding to notifications involved significant effort, including electronic health record (EHR) review, patient contact, and consultation with other clinicians.

DISCUSSION

Clinician's use of AI data is a function of beliefs regarding the trustworthiness and usefulness of the data, the degree of autonomy in professional roles, and the cognitive effort involved.

CONCLUSION

The implementation planning analysis guided development of strategies that addressed communication technology, patient education, and EHR integration to reduce clinician and patient burden in the subsequent main randomized phase of the trial. Our results provide important insights into the unique implications of implementing AI analytics into clinical workflow.

Generation of induced pluripotent stem cell line from a patient suffering from arterial calcification due to deficiency of CD73 (ACDC)

Arterial calcification due to deficiency of CD73 (ACDC) is an adult onset, rare genetic vascular disorder signified by calcium deposition in lower extremity arteries and joints of hands and feet. Mutations in NT5E gene has been shown to be responsible for the inactivation of enzyme CD73 causing calcium buildup. Here, we report a iPSC line generated from a patient showing signs of ACDC and carrying a missense mutation in NT5E (c.1126A→G,p.T376A) gene. This iPSC line shows normal morphology, pluripotency, karyotype, and capability to differentiate into three germ layers, making it useful for disease modeling and investigating pathological mechanisms of ACDC.

Generation of two induced pluripotent stem cell lines from hereditary amyloidosis patients with polyneuropathy carrying heterozygous transthyretin (TTR) mutation

Hereditary transthyretin amyloidosis with polyneuropathy (ATTR-PN) results from specific TTR gene mutations. In this study, we generated two induced pluripotent stem cell (iPSC) lines derived from ATTR-PN patients with heterozygous TTR gene mutations (Ala97Ser and Phe64Leu). These iPSC lines exhibited normal morphology, karyotype, high pluripotency marker expression, and differentiation into cells representing all germ layers. The generation of these iPSC lines serve as a valuable tool for investigating the mechanisms of ATTR-PN across various cell types and facilitating patient-specific in vitro amyloidosis modeling.

Almanac - Retrieval-Augmented Language Models for Clinical Medicine

BACKGROUND

Large language models (LLMs) have recently shown impressive zero-shot capabilities, whereby they can use auxiliary data, without the availability of task-specific training examples, to complete a variety of natural language tasks, such as summarization, dialogue generation, and question answering. However, despite many promising applications of LLMs in clinical medicine, adoption of these models has been limited by their tendency to generate incorrect and sometimes even harmful statements.

METHODS

We tasked a panel of eight board-certified clinicians and two health care practitioners with evaluating Almanac, an LLM framework augmented with retrieval capabilities from curated medical resources for medical guideline and treatment recommendations. The panel compared responses from Almanac and standard LLMs (ChatGPT-4, Bing, and Bard) versus a novel data set of 314 clinical questions spanning nine medical specialties.

RESULTS

Almanac showed a significant improvement in performance compared with the standard LLMs across axes of factuality, completeness, user preference, and adversarial safety.

CONCLUSIONS

Our results show the potential for LLMs with access to domain-specific corpora to be effective in clinical decision-making. The findings also underscore the importance of carefully testing LLMs before deployment to mitigate their shortcomings. (Funded by the National Institutes of Health, National Heart, Lung, and Blood Institute.).

Uptake of Sodium-Glucose Cotransporter-2 Inhibitors in Hospitalized Patients With Heart Failure: Insights From the Veterans Affairs Healthcare System

BACKGROUND

The use of sodium-glucose cotransporter-2 inhibitors (SGLT2is) in Veterans Affairs (VA) patients hospitalized with heart failure (HF) has not been reported previously.

METHODS

VA electronic health record data were used to identify patients hospitalized for HF (primary or secondary diagnosis) from 01/2019-11/2022. Patients with SGLT2i allergy, advanced/end-stage chronic kidney disease (CKD) or advanced HF therapies were excluded. We identified factors associated with discharge SGLT2i prescriptions for patients hospitalized due to HF in 2022. We also compared SGLT2i and angiotensin receptor-neprilysin inhibitor (ARNI) prescription rates. Hospital-level variations in SGLT2i prescriptions were assessed via the median odds ratio.

RESULTS

A total of 69,680 patients were hospitalized due to HF; 10.3% were prescribed SGLT2i at discharge (4.4% newly prescribed, 5.9% continued preadmission therapy). SGLT2i prescription increased over time and was higher in patients with HFrEF and primary HF. Among 15,762 patients hospitalized in 2022, SGLT2i prescription was more likely in patients with diabetes (adjusted odds ratio [aOR] 2.27; 95% confidence interval [CI]: 2.09-2.47) and ischemic heart disease (aOR 1.14; 95% CI: 1.03-1.26). Patients with increased age (aOR 0.77 per 10 years; 95% CI: 0.73-0.80) and lower systolic blood pressure (aOR 0.94 per 10 mmHg; 95% CI: 0.92-0.96) were less likely to be prescribed SGLT2i, and SGLT2i prescription was not more likely in patients with CKD (aOR 1.07; 95% CI 0.98-1.16). The adjusted median odds ratio suggested a 1.8-fold variation in the likelihood that similar patients at 2 random VA sites were prescribed SGLT2i (range 0-21.0%). In patients with EF ≤ 40%, 30.9% were prescribed SGLT2i while 26.9% were prescribed ARNI (P < 0.01).

CONCLUSION

One-tenth of VA patients hospitalized for HF were prescribed SGLT2i at discharge. Opportunities exist to reduce variation in SGLT2i prescription rates across hospitals and to promote its use in patients with CKD and older age.

Generation of two induced pluripotent stem cell lines from patients with cardiac amyloidosis carrying heterozygous transthyretin (TTR) mutation

Specific mutations in the TTR gene are responsible for the development of variant (hereditary) ATTR amyloidosis. Here, we generated two human induced pluripotent stem cell (iPSC) lines from patients diagnosed with Transthyretin Cardiac Amyloidosis (ATTR-CM) carrying heterozygous mutation in the TTR gene (i.e., p.Val30Met). The patient-derived iPSC lines showed expression of high levels of pluripotency markers, trilineage differentiation capacity, and normal karyotype. The generation of these iPSC lines represents a great tool for modeling patient-specific amyloidosis in vitro, allowing the investigation of the pathological mechanisms related to the disease in different cell types and tissues.

Generation of two induced pluripotent stem cell lines from dilated cardiomyopathy patients carrying heterozygous FLNC mutations

Dilated cardiomyopathy (DCM) is a heterogeneous cardiac disorder characterized by left ventricular dilatation and dysfunction. Mutations in dozens of cardiac genes have been connected to the development of DCM including the filamin C gene (FLNC). We generated two induced pluripotent stem cell (iPSCs) lines from DCM patients carrying single missense heterozygote FLNC mutations (c.6689G > A and c.3745G > A). Both lines expressed high levels of pluripotency markers, differentiated into derivatives of the three germ layers and possessed normal karyotypes. The derived iPSC lines can serve as powerful tools to model DCM in vitro and as a platform for therapeutic development.

Cardiovascular effects of immunosuppression agents

Immunosuppressive medications are widely used to treat patients with neoplasms, autoimmune conditions and solid organ transplants. Key drug classes, namely calcineurin inhibitors, mammalian target of rapamycin (mTOR) inhibitors, and purine synthesis inhibitors, have direct effects on the structure and function of the heart and vascular system. In the heart, immunosuppressive agents modulate cardiac hypertrophy, mitochondrial function, and arrhythmia risk, while in vasculature, they influence vessel remodeling, circulating lipids, and blood pressure. The aim of this review is to present the preclinical and clinical literature examining the cardiovascular effects of immunosuppressive agents, with a specific focus on cyclosporine, tacrolimus, sirolimus, everolimus, mycophenolate, and azathioprine.

Abstract P2115: Differential Cardiac Remodeling Profile Of Immunosuppression Drugs

Introduction: Heart transplantation provides lifesaving therapy for patients with end-stage heart failure. The longevity of the therapy is limited by Cardiac Graft Dysfunction (CGD), which is an acquired cardiomyopathy affecting transplanted hearts associated with diastolic and/or systolic dysfunction. Some clinical risk factors for CGD have been identified, but none of them are easily modifiable. An unexplored potential contributor to CGD is the choice of immunosuppression agent used despite multiple clinical reports suggesting reduced adverse cardiac remodeling with mammalian target of rapamycin (mTOR) inhibitors compared to calcineurin inhibitors (CNI). This study examines mechanisms of differential cardiac remodeling effects of CNI versus mTOR inhibitors in a human cellular cardiac model.

Methods/Results: We utilized 3D cardiac spheres composed of induced pluripotent stem cell-derived cardiomyocytes, cardiac fibroblasts, and endothelial cells (cardiac organoids). Cardiac organoids were treated with 5 days of vehicle, tacrolimus (CNI), or sirolimus (mTOR inhibitor). We did not observe a significant difference in surrogates of systolic or diastolic function in treated cardiac organoids. We pursued single cell-RNA sequencing of drug-treated cardiac organoids and identified gene expression changes consistent with increased extracellular matrix deposition and fibroblast activity in response to CNI treatment. In addition, CNI-treated cardiac organoids cellular composition was notable for increased proportion of fibroblasts and less cardiomyocytes compared to mTOR inhibitor-treated cardiac organoids. To validate gene expression changes observed, we treated cardiac fibroblasts with drugs and observed an increase in collagen production in response to CNI treatment and a reduction in fibroblast number and collagen production in response to mTOR inhibitor treatment. Furthermore, we observed increased ATP production in CNI-treated cardiac fibroblasts, but a reduction in mTOR-treated counterparts.

Conclusion: We identify reduced extracellular matrix deposition and cardiac fibroblast proliferation in response to mTOR inhibitor as a potential mechanism for the more favorable remodeling profile observed clinically.

Heterozygous LMNA mutation-carrying iPSC lines from three cardiac laminopathy patients

LMNA-related dilated cardiomyopathy (LMNA-DCM) is caused by pathogenic variants in the LMNA gene and is characterized by left ventricular chamber enlargement, reduced systolic function, and arrhythmia. Here, we generated three human induced pluripotent stem cell (iPSC) lines from peripheral blood mononuclear cells (PBMCs) of three DCM patients carrying the same single heterozygous mutation, c.398 G > A, in LMNA. All lines exhibited normal iPSC morphology, expressed high levels of pluripotency markers, showed normal karyotypes, and could differentiate into the three germ layers. These patient-specific iPSC lines can serve as invaluable tools to model in vitro pathological mechanisms of LMNA-DCM.

Generation of two induced pluripotent stem cell lines from Brugada syndrome affected patients carrying SCN5A mutations

SCN5A gene loss-of-function mutations are commonly associated with Brugada syndrome, which represents a risk of lethal arrhythmias and sudden cardiac death. The present report describes the generation of two human induced pluripotent stem cell (iPSC) lines reprogrammed from two Brugada syndrome affected patients carrying SCN5A mutations, c.53506 G>A and c.2102 C>T, respectively. Pluripotency markers, karyotype stability, and differentiation capability into derivatives of the three germ layers were assessed and described in the present report. These lines can be used as a reliable cell model for Brugada syndrome investigations and characterization of leading cellular mechanisms.

Counter-Irrigation as a Novel Technique versus the Standard Technique in Percutaneous Nephrolithotomy: A Prospective Randomized Trial

OBJECTIVE

This study aimed to evaluate the efficacy of our counter-irrigation technique versus the standard technique in percutaneous nephrolithotomy (PCNL) by assessment of the stone-free rate after the procedures and its safety in terms of comparing the intraoperative time, Hb deficit, blood transfusion, length of hospital stay, auxiliary procedures, and perioperative complications with that of the standard one.

METHODS

This prospective randomized trial was conducted on patients with renal stone 2-3 cm in diameter without contraindications to PCNL. The patients were randomized into group A in which the counter-irrigation technique has been performed and group B who were managed by the standard technique. The preoperative characteristics including demographic data and stone parameters were compared between both groups. The primary outcome was the stone-free rate assessed by noncontrast spiral CT after 3 months. The secondary outcome included intraoperative time, Hb deficit, blood transfusion, hospital stay, auxiliary procedure required, and rate of complications.

RESULTS

Forty-eight patients were included in this study. Overall, no significant difference was observed between both groups regarding preoperative characteristics, Hb deficit, and complication rate. Operative time was significantly shorter in group B (p = 0.001). None of our patients required blood transfusion. The stone-free rates at 3 months were significantly better in group A (95% for group A and 70% for group B, p = 0.04).

CONCLUSIONS

Our results indicate that our counter-irrigation technique has lower stone migration with subsequent significantly better stone-free rate versus the standard technique. We can recommend this technique as a potentially valid option for cases with large stone burden when the access to the upper calyx is feasible to minimize significant residual fragments.

Coronary Artery Vasospasm Requiring Cardiac Autotransplantation Yet Controlled With Tobacco

Coronary artery vasospasm is typically managed through avoidance of triggers and with symptomatic treatments with calcium channel blockers and long-acting nitrates. Here, we report a rare case of medically refractory coronary artery vasospasm associated with genetic predispositions that initially required cardiac autotransplantation followed paradoxically by nicotine for long-term symptomatic control. (Level of Difficulty: Intermediate.)

Unfolded Protein Response as a Compensatory Mechanism and Potential Therapeutic Target in PLN R14del Cardiomyopathy

BACKGROUND

Phospholamban (PLN) is a critical regulator of calcium cycling and contractility in the heart. The loss of arginine at position 14 in PLN (R14del) is associated with dilated cardiomyopathy with a high prevalence of ventricular arrhythmias. How the R14 deletion causes dilated cardiomyopathy is poorly understood, and there are no disease-specific therapies.

METHODS

We used single-cell RNA sequencing to uncover PLN R14del disease mechanisms in human induced pluripotent stem cells (hiPSC-CMs). We used both 2-dimensional and 3-dimensional functional contractility assays to evaluate the impact of modulating disease-relevant pathways in PLN R14del hiPSC-CMs.

RESULTS

Modeling of the PLN R14del cardiomyopathy with isogenic pairs of hiPSC-CMs recapitulated the contractile deficit associated with the disease in vitro. Single-cell RNA sequencing revealed the induction of the unfolded protein response (UPR) pathway in PLN R14del compared with isogenic control hiPSC-CMs. The activation of UPR was also evident in the hearts from PLN R14del patients. Silencing of each of the 3 main UPR signaling branches (IRE1, ATF6, or PERK) by siRNA exacerbated the contractile dysfunction of PLN R14del hiPSC-CMs. We explored the therapeutic potential of activating the UPR with a small molecule activator, BiP (binding immunoglobulin protein) inducer X. PLN R14del hiPSC-CMs treated with BiP protein inducer X showed a dose-dependent amelioration of the contractility deficit in both 2-dimensional cultures and 3-dimensional engineered heart tissues without affecting calcium homeostasis.

CONCLUSIONS

Together, these findings suggest that the UPR exerts a protective effect in the setting of PLN R14del cardiomyopathy and that modulation of the UPR might be exploited therapeutically.

Generation of three induced pluripotent stem cell lines from hypertrophic cardiomyopathy patients carrying MYH7 mutations

MYH7 heterozygous mutations are common genetic causes of hypertrophic cardiomyopathy (HCM). HCM is characterized by hypertrophy of the left ventricle and diastolic dysfunction. We generated three human induced pluripotent stem cell (iPSC) lines from three HCM patients each carrying a single heterozygous mutation in MYH7, c.2167C > T, c.4066G > A, and c.5135G > A, respectively. All lines expressed high levels of pluripotent markers, had normal karyotype, and possessed capability of differentiation into derivatives of the three germ layers, which can serve as valuable tools for modeling HCM in vitro and investigating the pathological mechanisms related to MYH7 mutations.

Clinical trial in a dish using iPSCs shows lovastatin improves endothelial dysfunction and cellular cross-talk in LMNA cardiomyopathy

Mutations in LMNA, the gene that encodes lamin A and C, causes LMNA-related dilated cardiomyopathy (DCM) or cardiolaminopathy. LMNA is expressed in endothelial cells (ECs); however, little is known about the EC-specific phenotype of LMNA-related DCM. Here, we studied a family affected by DCM due to a frameshift variant in LMNA Human induced pluripotent stem cell (iPSC)-derived ECs were generated from patients with LMNA-related DCM and phenotypically characterized. Patients with LMNA-related DCM exhibited clinical endothelial dysfunction, and their iPSC-ECs showed decreased functionality as seen by impaired angiogenesis and nitric oxide (NO) production. Moreover, genome-edited isogenic iPSC lines recapitulated the EC disease phenotype in which LMNA-corrected iPSC-ECs showed restoration of EC function. Simultaneous profiling of chromatin accessibility and gene expression dynamics by combining assay for transposase-accessible chromatin using sequencing (ATAC-seq) and RNA sequencing (RNA-seq) as well as loss-of-function studies identified Krüppel-like factor 2 (KLF2) as a potential transcription factor responsible for the EC dysfunction. Gain-of-function studies showed that treatment of LMNA iPSC-ECs with KLF2 agonists, including lovastatin, rescued the EC dysfunction. Patients with LMNA-related DCM treated with lovastatin showed improvements in clinical endothelial dysfunction as indicated by increased reactive hyperemia index. Furthermore, iPSC-derived cardiomyocytes (iPSC-CMs) from patients exhibiting the DCM phenotype showed improvement in CM function when cocultured with iPSC-ECs and lovastatin. These results suggest that impaired cross-talk between ECs and CMs can contribute to the pathogenesis of LMNA-related DCM, and statin may be an effective therapy for vascular dysfunction in patients with cardiolaminopathy.

Sirolimus Adverse Event Profile in a Non-Clinical Trial Cohort of Heart Transplantation Patients

Background

Sirolimus has been used increasingly in heart transplantation for its ability to reduce acute rejection, prevent the progression of cardiac allograft vasculopathy (CAV), and preserve renal function. We sought to assess the adverse reactions associated with the use of sirolimus compared to mycophenolate mofetil (MMF).

Material/Methods

We retrospectively reviewed the charts of 221 adult heart transplant patients who received either sirolimus or MMF as part of their immunosuppression from June 1, 2001 to April 1, 2005. Patients were assigned to 2 groups based upon immunosuppression use. The prevalence and types of complications were recorded in each group.

Results

Sirolimus was received by 109 patients and 112 patients received MMF during the study period. Seventy-seven patients (71%) in the sirolimus group experienced adverse reactions compared to 45 patients (40%) in the MMF group (P<0.01). Compared to MMF, the use of sirolimus was associated with a higher prevalence of elevated triglyceride levels, lower-extremity edema, and oral ulcerations. Sirolimus was discontinued due to adverse reactions in 22% of patients, whereas no patients in the MMF group experienced adverse effects requiring drug discontinuation.

Conclusions

Compared to MMF, sirolimus use is associated with a higher prevalence of adverse reactions requiring drug discontinuation, but most patients were able to stay on therapy despite adverse effects.

Modelling diastolic dysfunction in induced pluripotent stem cell-derived cardiomyocytes from hypertrophic cardiomyopathy patients

AIMS

Diastolic dysfunction (DD) is common among hypertrophic cardiomyopathy (HCM) patients, causing major morbidity and mortality. However, its cellular mechanisms are not fully understood, and presently there is no effective treatment. Patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) hold great potential for investigating the mechanisms underlying DD in HCM and as a platform for drug discovery.

METHODS AND RESULTS

In the present study, beating iPSC-CMs were generated from healthy controls and HCM patients with DD. Micropatterned iPSC-CMs from HCM patients showed impaired diastolic function, as evidenced by prolonged relaxation time, decreased relaxation rate, and shortened diastolic sarcomere length. Ratiometric Ca2+ imaging indicated elevated diastolic [Ca2+]i and abnormal Ca2+ handling in HCM iPSC-CMs, which were exacerbated by β-adrenergic challenge. Combining Ca2+ imaging and traction force microscopy, we observed enhanced myofilament Ca2+ sensitivity (measured as dF/Δ[Ca2+]i) in HCM iPSC-CMs. These results were confirmed with genome-edited isogenic iPSC lines that carry HCM mutations, indicating that cytosolic diastolic Ca2+ overload, slowed [Ca2+]i recycling, and increased myofilament Ca2+ sensitivity, collectively impairing the relaxation of HCM iPSC-CMs. Treatment with partial blockade of Ca2+ or late Na+ current reset diastolic Ca2+ homeostasis, restored diastolic function, and improved long-term survival, suggesting that disturbed Ca2+ signalling is an important cellular pathological mechanism of DD. Further investigation showed increased expression of L-type Ca2+channel (LTCC) and transient receptor potential cation channels (TRPC) in HCM iPSC-CMs compared with control iPSC-CMs, which likely contributed to diastolic [Ca2+]i overload.

CONCLUSION

In summary, this study recapitulated DD in HCM at the single-cell level, and revealed novel cellular mechanisms and potential therapeutic targets of DD using iPSC-CMs.

HIF1α Regulates Early Metabolic Changes due to Activation of Innate Immunity in Nuclear Reprogramming

Innate immune signaling has recently been shown to play an important role in nuclear reprogramming, by altering the epigenetic landscape and thereby facilitating transcription. However, the mechanisms that link innate immune activation and metabolic regulation in pluripotent stem cells remain poorly defined, particularly with regard to key molecular components. In this study, we show that hypoxia-inducible factor 1α (HIF1α), a central regulator of adaptation to limiting oxygen tension, is an unexpected but crucial regulator of innate immune-mediated nuclear reprogramming. HIF1α is dramatically upregulated as a consequence of Toll-like receptor 3 (TLR3) signaling and is necessary for efficient induction of pluripotency and transdifferentiation. Bioenergetics studies reveal that HIF1α regulates the reconfiguration of innate immune-mediated reprogramming through its well-established role in throwing a glycolytic switch. We believe that results from these studies can help us better understand the influence of immune signaling in tissue regeneration and lead to new therapeutic strategies.

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HIF1α is dramatically upregulated as a consequence of TLR3 signaling

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HIF1α is necessary for efficient induction of pluripotency and transdifferentiation

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HIF1α regulates innate immune-mediated reprogramming by inducing a glycolytic switch

Activation of PDGF pathway links LMNA mutation to dilated cardiomyopathy

Lamin A/C (LMNA) is one of the most frequently mutated genes associated with dilated cardiomyopathy (DCM). DCM related to mutations in LMNA is a common inherited cardiomyopathy that is associated with systolic dysfunction and cardiac arrhythmias. Here we modelled the LMNA-related DCM in vitro using patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). Electrophysiological studies showed that the mutant iPSC-CMs displayed aberrant calcium homeostasis that led to arrhythmias at the single-cell level. Mechanistically, we show that the platelet-derived growth factor (PDGF) signalling pathway is activated in mutant iPSC-CMs compared to isogenic control iPSC-CMs. Conversely, pharmacological and molecular inhibition of the PDGF signalling pathway ameliorated the arrhythmic phenotypes of mutant iPSC-CMs in vitro. Taken together, our findings suggest that the activation of the PDGF pathway contributes to the pathogenesis of LMNA-related DCM and point to PDGF receptor-β (PDGFRB) as a potential therapeutic target.

Targeted and Selective Treatment of Pluripotent Stem Cell-derived Teratomas Using External Beam Radiation in a Small-animal Model

The growing number of victims of "stem cell tourism," the unregulated transplantation of stem cells worldwide, has raised concerns about the safety of stem cell transplantation. Although the transplantation of differentiated rather than undifferentiated cells is common practice, teratomas can still arise from the presence of residual undifferentiated stem cells at the time of transplant or from spontaneous mutations in differentiated cells. Because stem cell therapies are often delivered into anatomically sensitive sites, even small tumors can be clinically devastating, resulting in blindness, paralysis, cognitive abnormalities, and cardiovascular dysfunction. Surgical access to these sites may also be limited, leaving patients with few therapeutic options. Controlling stem cell misbehavior is, therefore, critical for the clinical translation of stem cell therapy. External beam radiation offers an effective means of delivering targeted therapy to decrease the teratoma burden while minimizing injury to surrounding organs. Additionally, this method avoids genetic manipulation or viral transduction of stem cells-which are associated with additional clinical safety and efficacy concerns. Here, we describe a protocol to create pluripotent stem cell-derived teratomas in mice and to apply external beam radiation therapy to selectively ablate these tumors in vivo.

Abstract 243: Modeling of Diastolic Dysfunction in Induced Pluripotent Stem Cell-derived Cardiomyocytes From Hypertrophic Cardiomyopathy Patients

Aims: Diastolic dysfunction (DD) is common among hypertrophic cardiomyopathy (HCM) patients, causing major morbidity and mortality. Yet its cellular mechanisms are not fully understood, and presently, there is no effective treatment. Patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) hold great potential for investigating the mechanisms underlying DD and as a platform for drug discovery.

Methods and results: In the present study, beating iPSC-CMs were generated from healthy recruits and HCM patients with evident DD. Micropatterned iPSC-CMs from HCM patients showed impaired diastolic function, as evidenced by prolonged relaxation time, retarded relaxation rate, and shortened diastolic sarcomere length. Ratiometric Ca 2+ imaging indicated elevated diastolic [Ca 2+ ] i and abnormal Ca 2+ handling in HCM iPSC-CMs, which were exacerbated by β-adrenergic challenge. Combining Ca 2+ imaging and traction force microscopy (TFM), we observed enhanced myofilament Ca 2+ sensitivity (measured as dF/Δ[Ca 2+ ] i ) in HCM iPSC-CMs. These results indicated that cytosolic diastolic Ca 2+ overload, slowed [Ca 2+ ] i decline and increased myofilament Ca 2+ sensitivity, collectively impair the relaxation of HCM cells. Treating HCM iPSC-CMs with partial blockade of Ca 2+ or late Na + current reset diastolic Ca 2+ homeostasis, restored diastolic function and improved long-term survival, suggesting disturbed Ca 2+ signaling is an important cellular pathological mechanism of DD. Further investigation showed increased expression of L-type calcium channel (LTCC) and transient receptor potential channels (TRPCs) in HCM iPSC-CMs, which likely contribute to diastolic [Ca 2+ ] i overload.

Conclusion: In summary, this study recapitulated DD at the single cell level, and revealed novel mechanisms and potential therapeutic targets of DD using HCM iPSC-CMs.

Abstract 209: Downregulation of KLF2 in the Endothelium Contributes to the Pathogenesis in LMNA-related Dilated Cardiomyopathy

Background: Mutations in the gene that encodes the nuclear envelope proteins lamin A and C (LMNA) accounts for 6% of all cases of Dilated Cardiomyopathy (DCM). However, the molecular mechanisms that underlie “cardiolaminopathy” remain elusive, and it is unknown why mutations in this ubiquitously expressed gene have such a disproportionate effect on the heart.

Hypothesis: Despite the fact that LMNA is abundantly expressed in endothelial cells (ECs) and mutations in LMNA are known to induce EC dysfunction, little is known about the EC-specific phenotype of LMNA-related DCM. As EC dysfunction has been known to contribute to DCM, we hypothesize that EC dysfunction due to LMNA mutation has a significant impact on the pathogenesis and disease progression of DCM.

Results: Intriguingly, our preliminary data showed that iPSC-ECs derived from patients (n=5) harboring the LMNA-mutation exhibit decrease functionality as seen by impaired angiogenesis and decreased NO production (control iPSC-ECs vs LMNA iPSC-ECs; p<0.05). Similarly, genome editing of isogenic iPSC lines enabled us to recapitulate the EC disease phenotype further allowing us to dissect the effects of LMNA mutations on EC function. LMNA corrected iPSC-ECs (via use of CRISPR/Cas9 genome editing tool to correct the single mutated copy in heterozygous patient’s iPSCs) showed restoration of EC function. Whole genome RNA-sequencing identified Krüppel-like Factor 2 (KLF2) as a potential transcript responsible for EC dysfunction in LMNA-mutated patients. Importantly, treatment of LMNA-mutated ECs with KLF2 agonists showed rescue of EC dysfunction. Furthermore, iPSC-derived cardiomyocytes (iPSC-CMs) from LMNA-mutated patients that exhibited DCM phenotype, showed improvement in CM physiology when co-cultured with iPSC-ECs treated with KLF2 agonists.

Conclusion: This study is a first step towards understanding the molecular mechanisms of cardiolaminopathy by modeling endothelial dysfunction using patient-specific iPSCs. Moreover, our results suggest that improving EC function in cardiolaminopathy patients could have a significant impact on the pathogenesis of DCM. Results from this work could potentially lead to new strategies that could improve the management of DCM patients.

Genome Editing of Induced Pluripotent Stem Cells to Decipher Cardiac Channelopathy Variant

BACKGROUND

The long QT syndrome (LQTS) is an arrhythmogenic disorder of QT interval prolongation that predisposes patients to life-threatening ventricular arrhythmias such as Torsades de pointes and sudden cardiac death. Clinical genetic testing has emerged as the standard of care to identify genetic variants in patients suspected of having LQTS. However, these results are often confounded by the discovery of variants of uncertain significance (VUS), for which there is insufficient evidence of pathogenicity.

OBJECTIVES

The purpose of this study was to demonstrate that genome editing of patient-specific induced pluripotent stem cells (iPSCs) can be a valuable approach to delineate the pathogenicity of VUS in cardiac channelopathy.

METHODS

Peripheral blood mononuclear cells were isolated from a carrier with a novel missense variant (T983I) in the KCNH2 (LQT2) gene and an unrelated healthy control subject. iPSCs were generated using an integration-free Sendai virus and differentiated to iPSC-derived cardiomyocytes (CMs).

RESULTS

Whole-cell patch clamp recordings revealed significant prolongation of the action potential duration (APD) and reduced rapidly activating delayed rectifier K+ current (IKr) density in VUS iPSC-CMs compared with healthy control iPSC-CMs. ICA-105574, a potent IKr activator, enhanced IKr magnitude and restored normal action potential duration in VUS iPSC-CMs. Notably, VUS iPSC-CMs exhibited greater propensity to proarrhythmia than healthy control cells in response to high-risk torsadogenic drugs (dofetilide, ibutilide, and azimilide), suggesting a compromised repolarization reserve. Finally, the selective correction of the causal variant in iPSC-CMs using CRISPR/Cas9 gene editing (isogenic control) normalized the aberrant cellular phenotype, whereas the introduction of the homozygous variant in healthy control cells recapitulated hallmark features of the LQTS disorder.

CONCLUSIONS

The results suggest that the KCNH2T983I VUS may be classified as potentially pathogenic.

Abstract 6: Restoration of Impaired Diastolic Function in Hypertrophic Cardiomyopathy Induced Pluripotent Stem Cell-derived Cardiomyocytes by Re-balancing the Calcium Homeostasis

Background: Diastolic dysfunction is commonly seen in hypertrophic cardiomyopathy (HCM). However, the cellular mechanism is not fully understood, and no effective treatment so far has been developed. We hypothesize here that HCM patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) can recapitulate the cellular mechanism, and provide us a platform for mechanistic study and for drug screening of diastolic dysfunctions in HCM.

Methods and Results: We generated beating iPSC-CMs from healthy individuals and HCM patients carrying familial mutations (MYH7 R663H (n=2 lines) and MYBPC3 R943ter (n=2 lines)). Sarcomere shortening measurement in patterned iPSC-CMs with live cell confocal imaging showed significantly prolonged diastolic phase and slower relaxation velocity in HCM iPSC-CMs compared to WT cells. To elucidate the cellular mechanism, Fura-2 AM ratiometric calcium imaging showed marked elevation of resting calcium level and increased abnormal calcium handlings in HCM iPSC-CMs, which were exaggerated by β-adrenergic activation with isoproterenol. By applying calcium transient and contractile force simultaneous recording, we defined a “risk index of diastolic dysfunction” (measured as transient-contraction gain factor), which was significantly increased in HCM iPSC-CMs. Thus, both elevated basal calcium level and increased calcium sensitivity of myofilament contribute to the abnormal diastolic function in HCM iPSC-CMs. Gene expression profiling of HCM and WT iPSC-CMs indicated that increased calcium channels may underlie the increased basal calcium concentration in HCM cells. Indeed, partially blocking the calcium influx by calcium blockers reset the basal calcium level, attenuated calcium mishandling, and restored the diastolic function in HCM iPSC-CMs. Moreover, re-balancing calcium homeostasis significantly improved long-term survival rate of HCM iPSC-CMs at both basal level and under β-adrenergic stress.

Conclusion: The iPSC-CM models carrying patient-specific HCM mutations recapitulated diastolic dysfunction on single cell level. Future studies using these platform may reveal additional novel cellular mechanisms and therapeutic targets of diastolic dysfunction in HCM disease.

Abstract 442: Modeling Endothelial Dysfunction in LMNA-Related Dilated Cardiomyopathy

Background: Mutations in the gene that encodes the nuclear envelope proteins lamin A and C (LMNA) accounts for 6% of all cases of DCM. However, the molecular mechanisms that underlie “cardiolaminopathy” remain elusive, and it is unknown why mutations in this ubiquitously expressed gene have such a disproportionate effect on the heart.

Hypothesis: Despite the fact that LMNA is abundantly expressed in endothelial cells (ECs) and mutations in LMNA are known to induce EC dysfunction, little is known about the EC-specific phenotype of LMNA-related DCM. As EC dysfunction has been known to contribute to DCM, we hypothesize that EC dysfunction due to LMNA mutation has a significant impact on the pathogenesis and disease progression of DCM.

Results: Intriguingly, our preliminary data showed that iPSC-ECs derived from patients (n=5) harboring the LMNA-mutation exhibit decrease functionality as seen by impaired angiogenesis and decreased NO production (control iPSC-ECs vs LMNA iPSC-ECs; p<0.05). Similarly, genome editing of isogenic iPSC lines enabled us to recapitulate the EC disease phenotype further allowing us to dissect the effects of LMNA mutations on EC function. LMNA corrected iPSC-ECs (via use of CRISPR/Cas9 genome editing tool to correct the single mutated copy in heterozygous patient’s iPSCs) showed restoration of EC function. Whole genome RNA-sequencing identified Krüppel-like Factor 2 (KLF2) as a potential transcript responsible for EC dysfunction in LMNA-mutated patients. Importantly, treatment of LMNA-mutated ECs with KLF2 agonists showed rescue of EC dysfunction. Furthermore, iPSC-derived cardiomyocytes (iPSC-CMs) from LMNA-mutated patients that exhibited DCM phenotype, showed improvement in CM physiology when co-cultured with iPSC-ECs treated with KLF2 agonists.

Conclusion: This study is a first step towards understanding the molecular mechanisms of cardiolaminopathy by modeling endothelial dysfunction using patient-specific iPSCs. Moreover, our results suggest that improving EC function in cardiolaminopathy patients could have a significant impact on the pathogenesis of DCM. Results from this work could potentially lead to new strategies that could improve the management of DCM patients.

Patient-Specific and Genome-Edited Induced Pluripotent Stem Cell-Derived Cardiomyocytes Elucidate Single-Cell Phenotype of Brugada Syndrome

BACKGROUND

Brugada syndrome (BrS), a disorder associated with characteristic electrocardiogram precordial ST-segment elevation, predisposes afflicted patients to ventricular fibrillation and sudden cardiac death. Despite marked achievements in outlining the organ level pathophysiology of the disorder, the understanding of human cellular phenotype has lagged due to a lack of adequate human cellular models of the disorder.

OBJECTIVES

The objective of this study was to examine single cell mechanism of Brugada syndrome using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs).

METHODS

This study recruited 2 patients with type 1 BrS carrying 2 different sodium voltage-gated channel alpha subunit 5 variants as well as 2 healthy control subjects. We generated iPSCs from their skin fibroblasts by using integration-free Sendai virus. We used directed differentiation to create purified populations of iPSC-CMs.

RESULTS

BrS iPSC-CMs showed reductions in inward sodium current density and reduced maximal upstroke velocity of action potential compared with healthy control iPSC-CMs. Furthermore, BrS iPSC-CMs demonstrated increased burden of triggered activity, abnormal calcium (Ca²⁺) transients, and beating interval variation. Correction of the causative variant by genome editing was performed, and resultant iPSC-CMs showed resolution of triggered activity and abnormal Ca²⁺ transients. Gene expression profiling of iPSC-CMs showed clustering of BrS compared with control subjects. Furthermore, BrS iPSC-CM gene expression correlated with gene expression from BrS human cardiac tissue gene expression.

CONCLUSIONS

Patient-specific iPSC-CMs were able to recapitulate single-cell phenotype features of BrS, including blunted inward sodium current, increased triggered activity, and abnormal Ca²⁺ handling. This novel human cellular model creates future opportunities to further elucidate the cellular disease mechanism and identify novel therapeutic targets.

Simultaneous ramp right heart catheterization and echocardiography in a ReliantHeart left ventricular assist device

Many clinicians caring for patients with continuous flow left ventricular assist devices (CF-LVAD) use ramp right heart catheterization (RHC) studies to optimize pump speed and also to troubleshoot CF-LVAD malfunction. An investigational device, the ReliantHeart Heart Assist 5 (Houston, TX), provides the added benefit of an ultrasonic flow probe on the outflow graft that directly measures flow through the CF-LVAD. We performed a simultaneous ramp RHC and echocardiogram on a patient who received the above CF-LVAD to optimize pump parameters and investigate elevated flow through the CF-LVAD as measured by the flow probe. We found that the patient’s hemodynamics were optimized at their baseline pump speed, and that the measured cardiac output via the Fick principle was lower than that measured by the flow probe. Right heart catheterization may be useful to investigate discrepancies between flow measured by a CF-LVAD and a patient’s clinical presentation, particularly in investigational devices where little clinical experience exists. More data is needed to elucidate the correlation between the flow measured by an ultrasonic probe and cardiac output as measured by RHC.

Finding the rhythm of sudden cardiac death: new opportunities using induced pluripotent stem cell-derived cardiomyocytes

Sudden cardiac death is a common cause of death in patients with structural heart disease, genetic mutations, or acquired disorders affecting cardiac ion channels. A wide range of platforms exist to model and study disorders associated with sudden cardiac death. Human clinical studies are cumbersome and are thwarted by the extent of investigation that can be performed on human subjects. Animal models are limited by their degree of homology to human cardiac electrophysiology, including ion channel expression. Most commonly used cellular models are cellular transfection models, which are able to mimic the expression of a single-ion channel offering incomplete insight into changes of the action potential profile. Induced pluripotent stem cell-derived cardiomyocytes resemble, but are not identical, adult human cardiomyocytes and provide a new platform for studying arrhythmic disorders leading to sudden cardiac death. A variety of platforms exist to phenotype cellular models, including conventional and automated patch clamp, multielectrode array, and computational modeling. Induced pluripotent stem cell-derived cardiomyocytes have been used to study long QT syndrome, catecholaminergic polymorphic ventricular tachycardia, hypertrophic cardiomyopathy, and other hereditary cardiac disorders. Although induced pluripotent stem cell-derived cardiomyocytes are distinct from adult cardiomyocytes, they provide a robust platform to advance the science and clinical care of sudden cardiac death.

A Rapid, High-Quality, Cost-Effective, Comprehensive and Expandable Targeted Next-Generation Sequencing Assay for Inherited Heart Diseases

RATIONALE

Thousands of mutations across >50 genes have been implicated in inherited cardiomyopathies. However, options for sequencing this rapidly evolving gene set are limited because many sequencing services and off-the-shelf kits suffer from slow turnaround, inefficient capture of genomic DNA, and high cost. Furthermore, customization of these assays to cover emerging targets that suit individual needs is often expensive and time consuming.

OBJECTIVE

We sought to develop a custom high throughput, clinical-grade next-generation sequencing assay for detecting cardiac disease gene mutations with improved accuracy, flexibility, turnaround, and cost.

METHODS AND RESULTS

We used double-stranded probes (complementary long padlock probes), an inexpensive and customizable capture technology, to efficiently capture and amplify the entire coding region and flanking intronic and regulatory sequences of 88 genes and 40 microRNAs associated with inherited cardiomyopathies, congenital heart disease, and cardiac development. Multiplexing 11 samples per sequencing run resulted in a mean base pair coverage of 420, of which 97% had >20× coverage and >99% were concordant with known heterozygous single nucleotide polymorphisms. The assay correctly detected germline variants in 24 individuals and revealed several polymorphic regions in miR-499. Total run time was 3 days at an approximate cost of $100 per sample.

CONCLUSIONS

Accurate, high-throughput detection of mutations across numerous cardiac genes is achievable with complementary long padlock probe technology. Moreover, this format allows facile insertion of additional probes as more cardiomyopathy and congenital heart disease genes are discovered, giving researchers a powerful new tool for DNA mutation detection and discovery.

Modeling inherited cardiac disorders

Advances in the understanding and treatment of cardiac disorders have been thwarted by the inability to study beating human cardiac cells in vitro. Induced pluripotent stem cells (iPSCs) bypass this hurdle by enabling the creation of patient-specific iPSC-derived cardiomyocytes (iPSC-CMs). These cells provide a unique platform to study cardiac diseases in vitro, especially hereditary cardiac conditions. To date, iPSC-CMs have been used to successfully model arrhythmic disorders, showing excellent recapitulation of cardiac channel function and electrophysiologic features of long QT syndrome types 1, 2, 3, and 8, and catecholaminergic polymorphic ventricular tachycardia (CPVT). Similarly, iPSC-CM models of dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM) have shown robust correlation of predicted morphologic, contractile, and electrical phenotypes. In addition, iPSC-CMs have shown some features of the respective phenotypes for arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C), LEOPARD syndrome, Pompe's disease, and Friedriech's ataxia. In this review, we examine the progress of utilizing iPSC-CMs as a model for cardiac conditions and analyze the potential for the platform in furthering the biology and treatment of cardiac disorders.  

Cardiac stem cell biology: glimpse of the past, present, and future

Cardiac regeneration strategies and de novo generation of cardiomyocytes have long been significant areas of research interest in cardiovascular medicine. In this review, we outline a variety of common cell sources and methods used to regenerate cardiomyocytes and highlight the important role that key Circulation Research articles have played in this flourishing field.

Drug screening using a library of human induced pluripotent stem cell-derived cardiomyocytes reveals disease-specific patterns of cardiotoxicity

BACKGROUND

Cardiotoxicity is a leading cause for drug attrition during pharmaceutical development and has resulted in numerous preventable patient deaths. Incidents of adverse cardiac drug reactions are more common in patients with preexisting heart disease than the general population. Here we generated a library of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from patients with various hereditary cardiac disorders to model differences in cardiac drug toxicity susceptibility for patients of different genetic backgrounds.

METHODS AND RESULTS

Action potential duration and drug-induced arrhythmia were measured at the single cell level in hiPSC-CMs derived from healthy subjects and patients with hereditary long QT syndrome, familial hypertrophic cardiomyopathy, and familial dilated cardiomyopathy. Disease phenotypes were verified in long QT syndrome, hypertrophic cardiomyopathy, and dilated cardiomyopathy hiPSC-CMs by immunostaining and single cell patch clamp. Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) and the human ether-a-go-go-related gene expressing human embryonic kidney cells were used as controls. Single cell PCR confirmed expression of all cardiac ion channels in patient-specific hiPSC-CMs as well as hESC-CMs, but not in human embryonic kidney cells. Disease-specific hiPSC-CMs demonstrated increased susceptibility to known cardiotoxic drugs as measured by action potential duration and quantification of drug-induced arrhythmias such as early afterdepolarizations and delayed afterdepolarizations.

CONCLUSIONS

We have recapitulated drug-induced cardiotoxicity profiles for healthy subjects, long QT syndrome, hypertrophic cardiomyopathy, and dilated cardiomyopathy patients at the single cell level for the first time. Our data indicate that healthy and diseased individuals exhibit different susceptibilities to cardiotoxic drugs and that use of disease-specific hiPSC-CMs may predict adverse drug responses more accurately than the standard human ether-a-go-go-related gene test or healthy control hiPSC-CM/hESC-CM screening assays.

Multiplexed protein and gene profiling of circulating tumor cells (CTCs) in metastatic castration-resistant prostate cancer (mCRPC) using automated immunofluorescence and fluorescence in situ hybridization

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Background: Clinically, CTCs are used primarily in longitudinal monitoring of metastatic disease progression. However, the analysis of specific CTC biomarkers has the potential to optimize patient management by identifying those likely to respond to specific targeted agents. Often, mCRPC is driven by dysregulation of the androgen receptor (AR) and phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) oncogenic pathways such that blockade of one pathway stimulates the other. These functional deficits in the AR and PI3K/AKT pathways are associated with fusion of the TMPRSS2 and ERG genes and with loss of PTEN protein, respectively. Therefore, we sought to characterize CTCs for the simultaneous presence of both these biomarkers using immunofluorescence (IF) and fluorescence in situ hybridization (FISH). Methods: Nucleated peripheral blood cells from mCRPC patients were attached to slides and examined using CTC technology (Epic Sciences). Cytokeratin-positive/CD45-negative cells with an intact nucleus and a malignancy-consistent morphology were identified as CTCs, and their exact positions on the slides were recorded. The slides were then subjected to multiplex Quantum Dot IF and FISH procedures with anti-AR, -ERG, and -PTEN antibodies and 5’ERG, 3’ERG, PTEN, and Cen10 probes, respectively, on an automated slide-staining platform (Ventana Medical Systems, Inc.). The IF and FISH signals were visualized by spectral imaging (Ventana). Results: The automated IF/FISH staining procedure facilitated multiplex characterization of individual CTCs from patient samples for the protein biomarker targets AR, ERG, and PTEN and the genomic biomarker targets 5’ERG, 3’ERG, PTEN, and Cen10. Conclusions: This method for high-sensitivity, multiplex molecular characterization of critical CTC biomarkers in mCRPC patients might aid oncologists in identifying and stratifying those patients likely to respond to combination therapy with targeted PI3K/AKT inhibitors and anti-androgens/Cyp17 inhibitors. Patient trials examining the clinical utility of this assay in mCRPC are currently underway.

Natural history of early repolarization in the inferior leads

AIMS

Though early repolarization (ER) in the inferior leads has been associated with increased cardiovascular risk, its natural history is uncertain. We aimed to study the serial electrocardiographic behavior of inferior ER and understand factors associated with that behavior.

METHODS

We selected electrocardiograms (ECGs) from patients with the greatest amplitude of ER in AVF from ECGs of 29,281 ambulatory patients recorded between 1987 and 1999 at the Palo Alto Veterans Affairs Hospital. Starting from the highest amplitude, we reviewed the ECGs and medical records from the first 85%. From this convenience sample, 36 were excluded for abnormal patterns similar to ER. The remaining 257 patients were searched for another ECG at least 5 months later, of whom, 136 satisfied this criteria. These ECGs were paired for comparison and coded by four interpreters.

RESULTS

The average time between the first and second ECGs was 10 years. Of the 136 subjects, 47% retained ER while 53% no longer fulfilled the amplitude criteria. While no significant differences were found in initial heart rate (HR) or time interval between ECGs, those who lost the ER pattern had a greater difference in HR between the ECGs. There was no significant difference in the incidence of cardiovascular events or deaths.

CONCLUSIONS

In conclusion, the ECG pattern of ER was lost over 10 years in over half of the cohort. The loss of ER was partially explained by changes in HR, but not higher incidence of cardiovascular events or death, suggesting the entity is a benign finding.

Prognostic implications of Q waves and T-wave inversion associated with early repolarization

OBJECTIVE

To evaluate the prevalence of early polarization (ER) in a stable population and to evaluate the prognostic significance of the association or absence of Q waves or T-wave inversion (TWI).

PATIENTS AND METHODS

In this retrospective study performed at the university-affiliated Palo Alto Veterans Affairs Health Care Center from March 1, 1987, through December 31, 1999, we evaluated outpatient electrocardiograms. Vital status and cause of death were determined in all patients, with a mean ± SD follow-up of 7.6±3.8 years.

RESULTS

Of the 29,281 patients, 87% were men and 13% were African American. Inferior or lateral ER was present in 664 patients (2.3%): in inferior leads in 185 (0.6%), in lateral leads in 479 (1.6%) , and in both inferior and lateral leads in 163 (0.6%). Only when Q waves or TWI accompanied ER was there an increased risk of cardiovascular death (Cox proportional hazards regression model, 5.0; 95% confidence interval, 3.4-7.2; P<.001).

CONCLUSION

Common patterns of ER without concomitant Q waves or TWI are not associated with increased risk of cardiovascular death; however, when either occurs with ER, there is a hazard ratio of 5.0. These findings confirm that ER is a benign entity; however, the presence of Q waves or TWI with ER is predictive of increased cardiovascular death.

Embryonic stem cell biology: insights from molecular imaging

Embryonic stem (ES) cells have therapeutic potential in disorders of cellular loss such as myocardial infarction, type I diabetes and neurodegenerative disorders. ES cell biology in living subjects was largely poorly understood until incorporation of molecular imaging into the field. Reporter gene imaging works by integrating a reporter gene into ES cells and using a reporter probe to induce a signal detectable by normal imaging modalities. Reporter gene imaging allows for longitudinal tracking of ES cells within the same host for a prolonged period of time. This has advantages over postmortem immunohistochemistry and traditional imaging modalities. The advantages include expression of reporter gene is limited to viable cells, expression is conserved between generations of dividing cells, and expression can be linked to a specific population of cells. These advantages were especially useful in studying a dynamic cell population such as ES cells and proved useful in elucidating the biology of ES cells. Reporter gene imaging identified poor integration of differentiated ES cells transplanted into host tissue as well as delayed donor cell death as reasons for poor long-term survival in vivo. This imaging technology also confirmed that ES cells indeed have immunogenic properties that factor into cell survival and differentiation. Finally, reporter gene imaging improved our understanding of the neoplastic risk of undifferentiated ES cells in forming teratomas. Despite such advances, much remains to be understood about ES cell biology to translate this technology to the bedside, and reporter gene imaging will certainly play a key role in formulating this understanding.