Statins improve endothelial function via suppression of epigenetic-driven EndMT

The pleiotropic benefits of statins in cardiovascular diseases that are independent of their lipid-lowering effects have been well documented, but the underlying mechanisms remain elusive. Here we show that simvastatin significantly improves human induced pluripotent stem cell-derived endothelial cell functions in both baseline and diabetic conditions by reducing chromatin accessibility at transcriptional enhanced associate domain elements and ultimately at endothelial-to-mesenchymal transition (EndMT)-regulating genes in a yes-associated protein (YAP)-dependent manner. Inhibition of geranylgeranyltransferase (GGTase) I, a mevalonate pathway intermediate, repressed YAP nuclear translocation and YAP activity via RhoA signaling antagonism. We further identified a previously undescribed SOX9 enhancer downstream of statin-YAP signaling that promotes the EndMT process. Thus, inhibition of any component of the GGTase-RhoA-YAP-SRY box transcription factor 9 (SOX9) signaling axis was shown to rescue EndMT-associated endothelial dysfunction both in vitro and in vivo, especially under diabetic conditions. Overall, our study reveals an epigenetic modulatory role for simvastatin in repressing EndMT to confer protection against endothelial dysfunction.

Generation of three induced pluripotent stem cell lines to model and investigate diseases affecting Hispanics

Hispanics are the fastest-growing minority group in the United States. There has been a burgeoning interest in understanding the reasons underlying health disparities among this population. To facilitate the modeling and investigation of diseases that differentially impact Hispanics, we generated three induced pluripotent stem cell (iPSC) lines from the peripheral blood mononuclear cells (PBMCs) of healthy Hispanic subjects. All three lines exhibited normal morphology and karyotypes, robust expression of pluripotency markers, and the capacity for trilineage differentiation. The derivatives of these lines will serve as valuable ethnic-appropriate cell sources for further mechanistic studies on diseases impacting Hispanics.

Angiogenic stem cell delivery platform to augment post-infarction neovasculature and reverse ventricular remodeling

Many cell-based therapies are challenged by the poor localization of introduced cells and the use of biomaterial scaffolds with questionable biocompatibility or bio-functionality. Endothelial progenitor cells (EPCs), a popular cell type used in cell-based therapies due to their robust angiogenic potential, are limited in their therapeutic capacity to develop into mature vasculature. Here, we demonstrate a joint delivery of human-derived endothelial progenitor cells (EPC) and smooth muscle cells (SMC) as a scaffold-free, bi-level cell sheet platform to improve ventricular remodeling and function in an athymic rat model of myocardial infarction. The transplanted bi-level cell sheet on the ischemic heart provides a biomimetic microenvironment and improved cell-cell communication, enhancing cell engraftment and angiogenesis, thereby improving ventricular remodeling. Notably, the increased density of vessel-like structures and upregulation of biological adhesion and vasculature developmental genes, such as Cxcl12 and Notch3, particularly in the ischemic border zone myocardium, were observed following cell sheet transplantation. We provide compelling evidence that this SMC-EPC bi-level cell sheet construct can be a promising therapy to repair ischemic cardiomyopathy.

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.

Abstract P3005: Cannabinoid Receptor 1 Antagonist Genistein Attenuates Marijuana-Induced Vascular Inflammation

Epidemiological studies reveal that marijuana increases the risk of cardiovascular disease (CVD); however, little is known about the mechanism. Δ 9 -tetrahydrocannabinol (Δ 9 -THC), the psychoactive component of marijuana, binds cannabinoid receptor 1 (CB1/CNR1) in the vasculature and is implicated in CVD. A UK Biobank analysis found that cannabis is an independent risk factor for CVD. We found that marijuana smoking activated inflammatory cytokines implicated in CVD. In silico virtual screening identified genistein, a soybean isoflavone, as a putative CB1 antagonist. Human-induced pluripotent stem cell-derived endothelial cells (hiPSC-ECs) were used to model Δ 9 -THC induced inflammation and oxidative stress via NF-κB signaling. Knockdown of the CB1 receptor with siRNA, CRISPR interference (CRISPRi), and genistein attenuate the effects of Δ 9 -THC. In mice, genistein blocked Δ 9 -THC-induced endothelial dysfunction in wire myograph, reduced atherosclerotic plaque, and had minimal penetration of the central nervous system (CNS). Genistein is a peripherally restricted CB1 antagonist that attenuates Δ 9 -THC-induced atherosclerosis.

Framework for patient-specific simulation of hemodynamics in heart failure with counterpulsation support

Despite being responsible for half of heart failure-related hospitalizations, heart failure with preserved ejection fraction (HFpEF) has limited evidence-based treatment options. Currently, a substantial clinical issue is that the disease etiology is very heterogenous with no patient-specific treatment options. Modeling can provide a framework for evaluating alternative treatment strategies. Counterpulsation strategies have the capacity to improve left ventricular diastolic filling by reducing systolic blood pressure and augmenting the diastolic pressure that drives coronary perfusion. Here, we propose a framework for testing the effectiveness of a soft robotic extra-aortic counterpulsation strategy using a patient-specific closed-loop hemodynamic lumped parameter model of a patient with HFpEF. The soft robotic device prototype was characterized experimentally in a physiologically pressurized (50–150 mmHg) soft silicone vessel and modeled as a combination of a pressure source and a capacitance. The patient-specific model was created using open-source software and validated against hemodynamics obtained by imaging of a patient (male, 87 years, HR = 60 bpm) with HFpEF. The impact of actuation timing on the flows and pressures as well as systolic function was analyzed. Good agreement between the patient-specific model and patient data was achieved with relative errors below 5% in all categories except for the diastolic aortic root pressure and the end systolic volume. The most effective reduction in systolic pressure compared to baseline (147 vs. 141 mmHg) was achieved when actuating 350 ms before systole. In this case, flow splits were preserved, and cardiac output was increased (5.17 vs. 5.34 L/min), resulting in increased blood flow to the coronaries (0.15 vs. 0.16 L/min). Both arterial elastance (0.77 vs. 0.74 mmHg/mL) and stroke work (11.8 vs. 10.6 kJ) were decreased compared to baseline, however left atrial pressure increased (11.2 vs. 11.5 mmHg). A higher actuation pressure is associated with higher systolic pressure reduction and slightly higher coronary flow. The soft robotic device prototype achieves reduced systolic pressure, reduced stroke work, slightly increased coronary perfusion, but increased left atrial pressures in HFpEF patients. In future work, the framework could include additional physiological mechanisms, a larger patient cohort with HFpEF, and testing against clinically used devices.

Cannabinoid receptor 1 antagonist genistein attenuates marijuana-induced vascular inflammation

Epidemiological studies reveal that marijuana increases the risk of cardiovascular disease (CVD); however, little is known about the mechanism. Δ⁹-tetrahydrocannabinol (Δ⁹-THC), the psychoactive component of marijuana, binds to cannabinoid receptor 1 (CB1/CNR1) in the vasculature and is implicated in CVD. A UK Biobank analysis found that cannabis was an risk factor for CVD. We found that marijuana smoking activated inflammatory cytokines implicated in CVD. In silico virtual screening identified genistein, a soybean isoflavone, as a putative CB1 antagonist. Human-induced pluripotent stem cell-derived endothelial cells were used to model Δ⁹-THC-induced inflammation and oxidative stress via NF-κB signaling. Knockdown of the CB1 receptor with siRNA, CRISPR interference, and genistein attenuated the effects of Δ⁹-THC. In mice, genistein blocked Δ⁹-THC-induced endothelial dysfunction in wire myograph, reduced atherosclerotic plaque, and had minimal penetration of the central nervous system. Genistein is a CB1 antagonist that attenuates Δ⁹-THC-induced atherosclerosis.

Preoperative Computed Tomography Angiography Reveals Leaflet-Specific Calcification and Excursion Patterns in Aortic Stenosis

BACKGROUND

Computed tomography-based evaluation of aortic stenosis (AS) by calcium scoring does not consider interleaflet differences in leaflet characteristics. Here, we sought to examine the functional implications of these differences.

METHODS

We retrospectively reviewed the computed tomography angiograms of 200 male patients with degenerative calcific AS undergoing transcatheter aortic valve replacement and 20 male patients with normal aortic valves. We compared the computed tomography angiography (CTA)-derived aortic valve leaflet calcification load (AVLCCTA), appearance, and systolic leaflet excursion (LEsys) of individual leaflets. We performed computer simulations of normal valves to investigate how interleaflet differences in LEsys affect aortic valve area. We used linear regression to identify predictors of leaflet-specific calcification in patients with AS.

RESULTS

In patients with AS, the noncoronary cusp (NCC) carried the greatest AVLCCTA (365.9 [237.3-595.4] Agatston unit), compared to the left coronary cusp (LCC, 278.5 [169.2-478.8] Agatston unit) and the right coronary cusp (RCC, 240.6 [137.3-439.0] Agatston unit; both P<0.001). However, LCC conferred the least LEsys (42.8° [38.8°-49.0°]) compared to NCC (44.8° [41.1°-49.78°], P=0.001) and RCC (47.7° [42.0°-52.3°], P<0.001) and was more often characterized as predominantly thickened (23.5%) compared to NCC (12.5%) and RCC (16.5%). Computer simulations of normal valves revealed greater reductions in aortic valve area following closures of NCC (-32.2 [-38.4 to -25.8]%) and RCC (-35.7 [-40.2 to -32.9]%) than LCC (-24.5 [-28.5 to -18.3]%; both P<0.001). By linear regression, the AVLCCTA of NCC and RCC, but not LCC, predicted LEsys (both P<0.001) in patients with AS. Both ostial occlusion and ostial height of the right coronary artery predicted AVLCCTA, RCC (P=0.005 and P=0.001).

CONCLUSIONS

In male patients, the AVLCCTA of NCC and RCC contribute more to AS than that of LCC. LCC's propensity for noncalcific leaflet thickening and worse LEsys, however, should not be underestimated when using calcium scores to assess AS severity.

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.)

A protocol for transdifferentiation of human cardiac fibroblasts into endothelial cells via activation of innate immunity

Endothelial cells (ECs) have emerged as key pathogenic players in cardiac disease due to their proximity with cardiomyocytes. Induced pluripotent stem cells (iPSCs) have been employed to generate ECs. However, it may be more clinically relevant to transdifferentiate fibroblasts into ECs directly without introducing pluripotent or virally driven transcription factors. Here, we present a protocol that describes the direct conversion of human cardiac fibroblasts into ECs by leveraging the innate immune system. Our protocol produces bona fide human ECs with 95%-98% purity by first passage. For complete details on the use and execution of this protocol, please refer to Liu et al. (2020) and Sayed et al. (2015).

The Smoking Paradox: A Twist in the Tale of Vasospastic Angina

Cigarette smoking is undoubtedly the single most important risk factor and trigger for vasospastic angina, a condition also known as Prinzmetal angina secondary to coronary artery vasospasm. Even decades before vasospastic angina was first described by Dr. Myron Prinzmetal and his colleagues in 1959, there had been suspected connections between smoking and coronary artery vasospasm in what was alluded to then as "tobacco angina." The intimate relationship between smoking and vasospastic angina has since been extensively researched and validated through decades of epidemiological and clinical studies. The fact that smoking would aggravate vasospastic angina comes with very little surprise, as it has been shown to adversely impact many of the disease processes thought to underlie vasospastic angina, including autonomic dysfunction, endothelial dysfunction, smooth muscle hyperactivity, and genetic susceptibility. While avoidance of smoking is the first logical step in managing smokers with vasospastic angina, there have been reported cases of vasospastic angina paradoxically triggered by smoking cessation or relieved with smoking resumption or nicotine replacement therapy. Thus, there appears to be patient-specific factors that could significantly alter the close connection between smoking and vasospastic angina, warranting further mechanistic investigations. In this review, we will examine this complicated relationship between smoking and vasospastic angina from multiple perspectives (historical, mechanistic, and clinical) and call attention to the "smoking paradox," which, with further elucidation, may provide additional insight into the complex mechanisms of VSA and potentially new strategies to treat medically refractory VSA, at least in selected individuals.

Abstract 325: The Regulation of Endothelial Function Through Hmgcr/mevalonate Pathway Mediated Yap Activity

Background: Cardiovascular diseases (CVD) are the leading cause of death in the United States. Statins, a class of hydroxy-methylglutaryl-coenzyme A reductase (HMGCR) inhibitors, have been proven to be effectively prevent and treat CVD by improving vascular functions independent of their cholesterol-lowering effect. However, the molecular mechanisms by which statins improve cardiovascular functions remain elusive. In this study, we used human induced pluripotent stem cells-derived endothelial cells (hiPSC-ECs) to explore the protective role of statins in the vascular system.

Methods and Results: hiPSCs were generated from 3 healthy individuals and differentiated into endothelial cells using two different iPSC clones and two batches (4 biological replicates for each individual). hiPSC-ECs of each individual were treated with simvastatin or a vehicle control. The RNA-sequencing analysis was performed on 12 control and 12 statin-treated hiPSC-ECs. A total number of 2,580 differentially expressed genes (DEGs) were found in simvastatin-treated hiPSC-ECs. Gene enrichment analysis revealed that statin-upregulated DEGs were highly enriched in angiogenesis and anti-inflammation pathways. Interestingly, statin-downregulated DEGs were significantly enriched in epigenetic regulation and nucleosome assembly pathways, suggesting an epigenetic regulatory role of stains in vascular gene expression. To test this hypothesis, we further performed the Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq) analysis on vehicle or simvastatin treated hiPSC-ECs. Transcription factor (TF) binding motif analyses of ATAC-seq peaks using HOMER revealed that YAP/TEAD binding was the most significantly downregulated TF after statin treatment. Furthermore, we observed that statin can improve endothelial functions (e.g., angiogenesis and nitric oxide production) after the YAP activity was inhibited. The ChIP-seq analysis showed that statin downregulated the expression levels of genes associated with the endothelial-to-mesenchymal transition (EndoMT) by attenuating the binding capacity of YAP. As such, simvastatin effectively rescued diabetic vascular dysfunction mainly through inhibiting EndoMT.

Conclusion: We found that statins can improve endothelial functions through attenuating the chromatin accessibility of EndoMT-related genes, a process tightly regulated by the activity of YAP. These findings will provide novel insights into the protective mechanisms of statins in the cardiovascular system beyond their cholesterol-lowering effects.

1098 Altered Actigraphic Behavioral Activity Rhythm In Depression

Introduction

Disturbances in sleep and behavioral activity rhythms (BAR) are frequently observed in individuals with depression. However, it remains unclear how activity variability across the 24-hour period is specifically associated with this disorder. The present study aimed to examine actigraphy-measured sleep and BAR in depression.

Methods

As part of a larger study, fourteen patients with DSM-5 major depressive episode (27.8±7.7 years, 69.2% female) and 13 healthy controls (21.8±1.2 years, 76.5% female) were evaluated with 7-14 days of wrist-actigraphy. Actigraphy-derived sleep parameters included total sleep time (TST), sleep onset latency (SOL), wake after sleep onset (WASO), and sleep efficiency (SE). Minute-by-minute activity counts were aggregated into hour-by-hour bins; hourly mean activity levels were then generated to depict 24-hour activity patterns (i.e., BAR). Factorial (GroupxTime) mixed models were conducted to examine whether BAR differed between patients with MDD and controls. Generalized Additive Models (GAM), by fitting smoothed nonlinear curves to log-transformed aggregated activity, were performed as exploratory analyses to characterize onset (UP slope) and offset (DOWN slope) of BAR.

Results

Compared to healthy controls, patients with MDD exhibited greater actigraphic TST (p=.026); no other between-group differences were detected for the remaining sleep parameters. Significant between-group differences were observed for mean activity during wakefulness (p&lt;.001). Mixed models assessing hour-by-hour daily activity revealed a significant GroupxTime interaction (p=.001) with significant main effects of group (p=.017) and time (p&lt;.001); patients with MDD had lower activity from 6 to 9 pm (ps&lt;.005). Exploratory GAMs results showed an attenuated DOWN slope in patients with MDD (p=.014), indicating a slower decrease in activity during the evening.

Conclusion

Altered BAR, characterized by an overall dampened activity pattern that was most prominent during the evening, was associated with depression. Furthermore, patients with MDD took longer to wind down in the evening. Future studies are needed to explore the potential benefits of adjunctive interventions addressing both BAR along with sleep in mitigating symptoms of depression.

Support

Research supported by National Institutes of Health R01 MH102392.

0422 Apocalypse Tau: The Relationship Between Inflammaging and Local Sleep Disruption in Older Adults is Mediated by Tau Burden

Introduction

Chronic inflammation in aging is independently associated with tau burden and sleep disruption, though the mechanism linking inflammation with sleep disruption remains unknown. Recent evidence associates tau burden with deficits in local expression of sleep spindles and slow wave activity (SWA). Here we test the hypothesis that age-related central inflammation disrupts local sleep by influencing tau pathology.

Methods

Cognitively asymptomatic older adults from the Wisconsin Alzheimer’s Disease Research Center underwent overnight polysomnography with high-density electroencephalography (hdEEG; 256 channels) at the University of Wisconsin-Madison (n=33, 61.9±6.7 years, 23 female). EEG data were subjected to multitaper spectral analysis (0.5-40Hz) to yield topographic maps of SWA (SWA1:0.5-1Hz, SWA2:1-4.5Hz) and spindle (sigma1:11-13Hz; sigma2:13-16Hz) power during NREM sleep. Cerebrospinal fluid assay-based measurements of YKL-40 (indicating glial activation), phosphorylated tau (Ptau), and total tau (Ttau), were correlated with SWA and sigma topographical power employing Holm-Bonferroni correction. Multiple linear regression models were implemented controlling for age, apnea-hypopnea index (AHI), and sex at significant derivations. Finally, Sobel testing was employed to assess whether tau burden mediated YKL-40-sleep associations.

Results

Age was associated with YKL-40 (r=0.53, p=0.002), and YKL-40 was associated with both Ptau (r=0.66, p&lt;0.001) and Ttau (r=0.68, p&lt;0.001). Correlations between sigma2 activity and both Ptau and Ttau were detected at 14 derivations, 12 of which remained significant after controlling for age, sex, and AHI. YKL-40 was associated with sigma2 power (r=-0.39, p=0.025) across derivations expressing peak significance with tau. Sobel mediation analyses indicated that both Ptau (t=-2.15, p=0.031) and Ttau (t=-2.36, p=0.018) mediated the relationship between YKL-40 and sigma2 activity at these derivations. SWA was not associated with Ttau, Ptau, or YKL-40.

Conclusion

These results suggest that age-related increases in central glial activation may disrupt local expression of fast spindles by increasing tau burden, highlighting a potential role for chronic inflammation in sleep deficits observed in aging and Alzheimer’s disease.

Support

Supported by R56 AG052698, P50AG033514

0335 Frontal Expression of NREM Sleep Oscillations are Associated with Executive Function in Children and Adolescents

Introduction

The prefrontal cortex, an area known for executive functioning (including inhibition and self-monitoring) develops during childhood and adolescents, with a pattern of posterior to anterior brain development. Slow-wave activity (SWA) in NREM sleep, tracks brain development with high SWA power migrating from occipital to frontal region as brain maturation occurs. This pilot study aimed to examine whether slow wave topography is correlated with executive function in youth.

Methods

Seventeen healthy children and adolescents (ages 11-17; 10 females) underwent overnight polysomnography (PSG) with high-density electroencephalography (hdEEG). Behavior Rating Inventory of Executive Function (BRIEF) was administered to assess executive function. SWA (SWA1: 0.5-1 Hz; SWA2: 1-4.5 Hz) and spindle (slow sigma: 11-13 Hz; fast sigma: 13-16 Hz) activity was analyzed with spectral analysis using Welch’s method. BRIEF subscales of inhibition and monitor were correlated with SWA and sigma power across all derivations, with Holm-Bonferroni correction (126 channels). Significant derivations were then controlled for sex and self-reported Tanner stage using multiple regression

Results

BRIEF-Inhibition scale (i.e., ability to repress impulsivity) and SWA1 in anterior frontal derivations were negatively correlated (R2=0.58, p=0.047 corrected). BRIEF-Monitor scale (i.e., self-perception of one’s own behavior and interpersonal awareness) was negatively correlated with fast sigma in anterior frontal derivations (R2=0.65, p=0.013 corrected). These associations were significant after controlling for sex and Tanner stage.

Conclusion

These results support the hypothesis that NREM sleep oscillations are associated with executive function and reflect changes in neuroplasticity related to “back-to-front” brain maturation. Future longitudinal studies should combine multi-modal neuroimaging of brain structure and local sleep with comprehensive assessments of executive function to evaluate the possible link between local sleep and development of higher-order cognition in frontal brain regions in youth.

Support

NCATS grant #UL1TR001414 & PERC Systems Biology Fund

0325 Better Aerobic Fitness is Associated with Distinct Sleep Characteristics in Children and Adolescents - A Pilot Study

Introduction

Aerobic fitness facilitates brain synaptic plasticity, which influences global and local sleep expression. While it is known that sleep patterns/behavior and non-rapid eye movement (NREM) sleep slow wave activity (SWA) tracks brain maturation, little is known about how aerobic fitness and sleep interact during growth and development in children and adolescents. The aim of this pilot study was to characterize relationships among aerobic fitness, measures of global/local sleep expression, and habitual sleep patterns in children and adolescents. We hypothesized that greater aerobic fitness would be associated with better sleep quality, indicated by increased SWA.

Methods

Twenty healthy youth (11-17 years-old, 11 female) were evaluated during summer vacation (no school schedule constraints). Aerobic fitness (VO2peak) was measured using ramp-type progressive cycle ergometry, habitual sleep (i.e., sleep-time consistency and circadian activity patterns) was assessed with 7-day actigraphy, and ad lib sleep was evaluated during overnight polysomnography (PSG) with high-density electroencephalography (hdEEG; 128 channels). Spectral analysis was implemented to quantify SWA (0.5-4.5Hz). Data were analyzed using linear regression analyses and exploratory independent samples t-tests.

Results

Negative correlations were observed between VO2peak and sleep measures including sleep-time consistency (partial r=-0.53, p=0.045) and timing/acrophase of the circadian activity rhythm (partial r=-0.64, p=0.01) while controlling for sex and age. Additionally, after accounting for Tanner stage and sex, data demonstrated significant effects in SWA at frontal derivations (p=0.024) between low and high fitness levels at topographically specific and meaningful EEG derivations, e.g. over frontal cortex.

Conclusion

These results suggest that children and adolescents with greater fitness have less variability in sleep-times (improved sleep consistency), tend to have a more advanced circadian activity phase (i.e., go to sleep earlier), and express greater frontal SWA, supporting the hypothesis that fitness is associated with improved local and global sleep quality. Future research with larger samples is necessary to further evaluate these relationships, and to determine if interventions that improve fitness also improve sleep and related brain plasticity.

Support

NCATS grant #UL1TR001414 & PERC Systems Biology Fund

0425 Severity of Insomnia Symptoms Differ by Cognitive Status in Adults with Down Syndrome

Introduction

Sleep is disturbed in Down syndrome (DS), with sleep apnea and insomnia prevalent throughout life. Sleep disturbance increases dementia risk and is more prevalent in dementia in non-DS populations. However, relationships between sleep and clinical status in DS remains unclear. We examined informant-reported sleep in adults with DS, with or without a consensus diagnosis of dementia, and related the severity of sleep disturbances to measures of adaptive behavior.

Methods

Insomnia (selected from Children’s Sleep Habits Questionnaire), daytime sleepiness (modified ESS), sleep apnea risk (modified STOP-BANG), and adaptive behavior (Vineland Adaptive Behavior Scales; VABS-3) questionnaires were collected from informants for 47 DS adults (52.1±6.6 years) enrolled in a Alzheimer’s disease biomarker study. Participants’ clinical statuses were categorized as cognitively unaffected (clinically significant impairment absent; n=38, 51.0±6.2 years), or as having definite dementia (clinically significant decline present; n=9, 56.6±6.4 years) using a standard consensus diagnosis procedure. Age was compared between groups using an independent samples t-test. ANCOVA was used to compare insomnia, daytime sleepiness, sleep apnea risk, and adaptive behavior measures across groups, while controlling for age. Partial correlation analyses examined associations between sleep measures and VABS-3 measures while controlling for clinical status.

Results

Participants categorized as definite dementia were older (t=-2.381, p=0.022). ANCOVA determined that insomnia symptoms, but not daytime sleepiness or apnea risk, were more severe in definite dementia participants (F=5.567, p=0.023), even when controlling for age. VABS-3 subscale scores differed by clinical status (all save play and leisure scores p&lt;0.017). Partial correlation analyses adjusting for clinical status indicated that insomnia symptom severity worsened with lower adaptive functioning (e.g., daily living skills—coping r=-0.41, p=0.007; socialization r=-0.33, p=0.024) regardless of clinical status.

Conclusion

These findings indicate that insomnia may be related to functional impairment and dementia in DS adults, and raises the possibility that insomnia treatments may influence dementia course and clinical symptomatology in DS.

Support

NIH U01AG051412

0329 Poor Prenatal Sleep and Postpartum Depression are Associated with Infant Sleep Problems

Introduction

Childhood sleep problems are associated with increased risk of psychiatric conditions later in life. Sleep disturbances are prevalent during pregnancy and associated with postpartum depression and persistent sleep disturbance. Although maternal sleep and mood likely contribute to infant sleep problems, relationships between these factors are understudied. The present study examined associations of prenatal maternal sleep and postpartum depression with infant sleep patterns.

Methods

The sample included 235 women (29.2±5.8 years old), who were enrolled in a longitudinal study beginning in the first trimester of pregnancy. Maternal sleep and mood were assessed with the Pittsburgh Sleep Quality Index, the Center for Epidemiologic Studies Depression Scale, and the Edinburgh Postnatal Depression Scale during 3 prenatal and 2 postpartum visits. Infant sleep patterns were assessed with the Brief Infant Sleep Questionnaire at 2-, 6-, and 12-months. Mixed model repeated measure analyses were conducted to examine changes in maternal and infant sleep across time. Partial correlation adjusted for age, depression, and postpartum maternal sleep was performed to estimate the association between prenatal maternal sleep and infant sleep. ANCOVAs controlling for age were conducted to assess the effect of postpartum depression on infant sleep.

Results

Maternal sleep quality deteriorated during the third trimester and 2-months postpartum, and improved at 6-months postpartum (ps&lt; .001). Infant sleep became more consolidated with age, with decreased nocturnal awakenings (frequency and duration) and increased nighttime sleep duration (ps&lt; .001). Poorer prenatal maternal sleep was associated with shorter infant sleep duration at 6 months (r=-0.33, p&lt;.001). Mothers with persistent postpartum depression reported their child as having longer daytime sleep compared to their counterparts (F=3.55, p&lt;.05).

Conclusion

Prenatal sleep problems and persistent postpartum depression are associated with poorer infant sleep. Our findings suggest that screening and preventive interventions for sleep problems during pregnancy may have beneficial impact on infant sleep.

Support

Research supported by National Institutes of Health MH-96889.

Pathway-specific reporter genes to study stem cell biology

Little is known on the phenotypic characteristics of stem cells (SCs) after they are transplanted to the myocardium, in part due to lack of noninvasive platforms to study SCs directly in the living subject. Reporter gene imaging has played a valuable role in the noninvasive assessment of cell fate in vivo. In this study, we validated a pathway-specific reporter gene that can be used to noninvasively image the phenotype of SCs transplanted to the myocardium. Rat mesenchymal SCs (MSCs) were studied for phenotypic evidence of myogenic characteristics under in vitro conditions. After markers of myogenic characteristics were identified, we constructed a reporter gene sensor, comprising the firefly luciferase (Fluc) reporter gene driven by the troponin T (TnT) promoter (cardio MSCs had threefold expression in polymerase chain reaction compared to control MSCs) using a two-step signal amplification strategy. MSCs transfected with TnT-Fluc were studied and validated under in vitro conditions, showing a strong signal after MSCs acquired myogenic characteristics. Lastly, we observed that cardio MSCs had higher expression of the reporter sensor compared to control cells (0.005 ± 0.0005 vs 0.0025 ± 0.0008 Tnt-Fluc/ubiquitin-Fluc, P < .05), and that this novel sensor can detect the change in the phenotype of MSCs directly in the living subject. Pathway-specific reporter gene imaging allows assessment of changes in the phenotype of MSCs after delivery to the ischemic myocardium, providing important information on the phenotype of these cells. Imaging sensors like the one described here are critical to better understanding of the changes that SCs undergo after transplantation.

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

Abstract 402: Adiponectin Receptor 3 is Associated With Endothelial Nitric Oxide Synthase Dysfunction and Predicts Insulin Resistance in South Asians

Type 2 diabetes (T2DM) is a global epidemic affecting over 400 million people and causes significant morbidity and mortality. T2DM has a strong association with cardiovascular disease (CVD), the number one cause of death globally with 17.5 million deaths per year. A precursor of T2DM, insulin resistance is central to the development of T2DM and is a risk factor for CVD. Insulin resistance is difficult to diagnose and individuals are often untreated prior to the onset of T2DM or CVD. South Asians are more likely to have insulin resistance, diabetes and cardiovascular disease when compared to age matched European cohorts. The molecular mechanisms of why South Asians are predisposed to insulin resistance and consequently cardiovascular disease were investigated using induced pluripotent stem cells (iPSCs) derived endothelial cells (iPSC-EC). Endothelial cells line blood vessels of the cardiovascular system. Unlike previous models, iPSC-EC are unique because they contain the individual's genetic information and the environmental influences retained in epigenetic marks are removed via reprogramming and differentiation. iPSC-ECs from insulin resistant South Asians show evidence of impaired insulin signaling as evidenced by decreased Akt phosphorylation, and paradoxically overexpression of eNOS and adiponectin receptor 3. In the cellular milieu of prediabetes, insulin resistance iPSC-ECs show impaired tubule formation and nitric oxide release. When adiponectin receptor 3 expression is suppressed using siRNA, eNOS expression decreases and expression of components of the insulin signaling cascade are improved to levels observed in control iPSC-ECs. Multiple linear regression modeling of clinical characteristics and gene and cellular phenotype was used to develop a scoring system that predicts a patient’s risk of developing insulin resistance and hence subsequently diabetes and cardiovascular complications. To our knowledge, this is the first iPSC-derived endothelial cell risk calculator with the potential to identify South Asian patients at risk for developing insulin resistance and cardiovascular disease before disease onset, which would allow for the early implementation of interventions that prevent morbidity and mortality.

Abstract 497: Studying Cardiovascular Effects of Marijuana on Healthy Individuals Using Human Derived Induced Pluripotent Stem Cells

Marijuana is the most widely used illicit drug worldwide. Epidemiological studies indicate that marijuana increases the risk of coronary artery disease (CAD). Adverse cerebrovascular and peripheral vascular effects are also associated with marijuana use. In addition, three synthetic cannabis drugs have been approved by the FDA for treating chemotherapy-induced nausea and vomiting, which also show cardiovascular side effects. Thus, both medical and recreational marijuana have adverse cardiovascular side effects. Cannabinoid CB1 receptor signaling is involved in a variety of pathophysiological processes and selective CB1 antagonists show therapeutic potential. However, the current repertoire of CB1 antagonists has psychiatric side effects and limited application. Therefore, developing new CB1 antagonists are an unmet and growing clinical need with marijuana use on the rise. Here we found compound JW-1, an isoflavone abundantly presenting in soybeans, partially docked into the CB1 receptor and inhibited CB1 activity, suggesting that compound JW-1 was a novel CB1 antagonist. Human endothelial cells were more sensitive to Δ 9 -tetrahydrocannabinol (Δ 9 -THC) than cardiomyocytes and cardiac fibroblasts. To determine the mechanism of Δ 9 -THC pathological effects on the vasculature, we generated human induced pluripotent stem cell-derived endothelial cells (hiPSC-ECs) from 5 healthy individuals. CB1 receptor was expressed in all hiPSC-ECs, whilst CB2 expression was low. Δ 9 -THC induced inflammation and oxidative stress via NF-κB signaling activated in hiPSC-ECs. Knockdown of CB1 receptor with siRNA, abrogation of receptor expression with CRISPRi and compound JW-1 treatment could rescue the effect of Δ 9 -THC. Furthermore, compound JW-1 blocked Δ 9 -THC-induced endothelial dysfunction in mice models. Our investigations reveal that Δ 9 -THC causes endothelial dysfunction via the CB1 receptor. Compound JW-1 is a novel CB1 antagonist that can be used for preventing Δ 9 -THC-induced side effects.

Marked Vascular Dysfunction in a Case of Peripartum Cardiomyopathy

Peripartum cardiomyopathy (PPCM) is a rare form of congestive heart failure characterized by left ventricular dysfunction that develops towards the end of pregnancy or during the early postpartum phase. Even though the majority of PPCM patients show partial or complete recovery of their heart functions, the mortality rate of PPCM remains high. Previous research has suggested that vascular dysfunction triggered by late-gestational hormones and potent anti-angiogenic factors play key roles in the pathogenesis of PPCM; however, the exact mechanisms remain elusive due to limited patient tissues for characterization. Here, we report a case of PPCM where the coronary vessels from the patient's explanted heart showed marked vascular dysfunction with impaired nitric oxide response. Importantly, these vessels exhibited deficient adenosine-mediated vasorelaxation when subjected to myograph studies, suggesting impaired Kv7 ion channels. Results from this work may lead to new therapeutic strategies for improving Kv7 function in PPCM patients.

Large-Scale Single-Cell RNA-Seq Reveals Molecular Signatures of Heterogeneous Populations of Human Induced Pluripotent Stem Cell-Derived Endothelial Cells

RATIONALE

Human-induced pluripotent stem cell-derived endothelial cells (iPSC-ECs) have risen as a useful tool in cardiovascular research, offering a wide gamut of translational and clinical applications. However, inefficiency of the currently available iPSC-EC differentiation protocol and underlying heterogeneity of derived iPSC-ECs remain as major limitations of iPSC-EC technology.

OBJECTIVE

Here, we performed droplet-based single-cell RNA sequencing (scRNA-seq) of the human iPSCs after iPSC-EC differentiation. Droplet-based scRNA-seq enables analysis of thousands of cells in parallel, allowing comprehensive analysis of transcriptional heterogeneity.

METHODS AND RESULTS

Bona fide iPSC-EC cluster was identified by scRNA-seq, which expressed high levels of endothelial-specific genes. iPSC-ECs, sorted by CD144 antibody-conjugated magnetic sorting, exhibited standard endothelial morphology and function including tube formation, response to inflammatory signals, and production of NO. Nonendothelial cell populations resulting from the differentiation protocol were identified, which included immature cardiomyocytes, hepatic-like cells, and vascular smooth muscle cells. Furthermore, scRNA-seq analysis of purified iPSC-ECs revealed transcriptional heterogeneity with 4 major subpopulations, marked by robust enrichment of CLDN5, APLNR, GJA5, and ESM1 genes, respectively.

CONCLUSIONS

Massively parallel, droplet-based scRNA-seq allowed meticulous analysis of thousands of human iPSCs subjected to iPSC-EC differentiation. Results showed inefficiency of the differentiation technique, which can be improved with further studies based on identification of molecular signatures that inhibit expansion of nonendothelial cell types. Subtypes of bona fide human iPSC-ECs were also identified, allowing us to sort for iPSC-ECs with specific biological function and identity.

Reduced carboxylesterase 1 is associated with endothelial injury in methamphetamine-induced pulmonary arterial hypertension

Pulmonary arterial hypertension is a complication of methamphetamine use (METH-PAH), but the pathogenic mechanisms are unknown. Given that cytochrome P450 2D6 (CYP2D6) and carboxylesterase 1 (CES1) are involved in metabolism of METH and other amphetamine-like compounds, we postulated that loss of function variants could contribute to METH-PAH. Although no difference in CYP2D6 expression was seen by lung immunofluorescence, CES1 expression was significantly reduced in endothelium of METH-PAH microvessels. Mass spectrometry analysis showed that healthy pulmonary microvascular endothelial cells (PMVECs) have the capacity to both internalize and metabolize METH. Furthermore, whole exome sequencing data from 18 METH-PAH patients revealed that 94.4% of METH-PAH patients were heterozygous carriers of a single nucleotide variant (SNV; rs115629050) predicted to reduce CES1 activity. PMVECs transfected with this CES1 variant demonstrated significantly higher rates of METH-induced apoptosis. METH exposure results in increased formation of reactive oxygen species (ROS) and a compensatory autophagy response. Compared with healthy cells, CES1-deficient PMVECs lack a robust autophagy response despite higher ROS, which correlates with increased apoptosis. We propose that reduced CES1 expression/activity could promote development of METH-PAH by increasing PMVEC apoptosis and small vessel loss.

Reprogramming and transdifferentiation for cardiovascular development and regenerative medicine: where do we stand?

Heart disease remains a leading cause of mortality and a major worldwide healthcare burden. Recent advances in stem cell biology have made it feasible to derive large quantities of cardiomyocytes for disease modeling, drug development, and regenerative medicine. The discoveries of reprogramming and transdifferentiation as novel biological processes have significantly contributed to this paradigm. This review surveys the means by which reprogramming and transdifferentiation can be employed to generate induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) and induced cardiomyocytes (iCMs). The application of these patient-specific cardiomyocytes for both in vitro disease modeling and in vivo therapies for various cardiovascular diseases will also be discussed. We propose that, with additional refinement, human disease-specific cardiomyocytes will allow us to significantly advance the understanding of cardiovascular disease mechanisms and accelerate the development of novel therapeutic options.

Induced pluripotent stem cells: at the heart of cardiovascular precision medicine

The advent of human induced pluripotent stem cell (hiPSC) technology has revitalized the efforts in the past decade to realize more fully the potential of human embryonic stem cells for scientific research. Adding to the possibility of generating an unlimited amount of any cell type of interest, hiPSC technology now enables the derivation of cells with patient-specific phenotypes. Given the introduction and implementation of the large-scale Precision Medicine Initiative, hiPSC technology will undoubtedly have a vital role in the advancement of cardiovascular research and medicine. In this Review, we summarize the progress that has been made in the field of hiPSC technology, with particular emphasis on cardiovascular disease modelling and drug development. The growing roles of hiPSC technology in the practice of precision medicine will also be discussed.

A titratable two-step transcriptional amplification strategy for targeted gene therapy based on ligand-induced intramolecular folding of a mutant human estrogen receptor

PURPOSE

The efficacy and safety of cardiac gene therapy depend critically on the level and the distribution of therapeutic gene expression following vector administration. We aimed to develop a titratable two-step transcriptional amplification (tTSTA) vector strategy, which allows modulation of transcriptionally targeted gene expression in the myocardium.

PROCEDURES

We constructed a tTSTA plasmid vector (pcTnT-tTSTA-fluc), which uses the cardiac troponin T (cTnT) promoter to drive the expression of the recombinant transcriptional activator GAL4-mER(LBD)-VP2, whose ability to transactivate the downstream firefly luciferase reporter gene (fluc) depends on the binding of its mutant estrogen receptor (ER(G521T)) ligand binding domain (LBD) to an ER ligand such as raloxifene. Mice underwent either intramyocardial or hydrodynamic tail vein (HTV) injection of pcTnT-tTSTA-fluc, followed by differential modulation of fluc expression with varying doses of intraperitoneal raloxifene prior to bioluminescence imaging to assess the kinetics of myocardial or hepatic fluc expression.

RESULTS

Intramyocardial injection of pcTnT-tTSTA-fluc followed by titration with intraperitoneal raloxifene led to up to tenfold induction of myocardial fluc expression. HTV injection of pcTnT-tTSTA-fluc led to negligible long-term hepatic fluc expression, regardless of the raloxifene dose given.

CONCLUSIONS

The tTSTA vector strategy can effectively modulate transgene expression in a tissue-specific manner. Further refinement of this strategy should help maximize the benefit-to-risk ratio of cardiac gene therapy.

Noninvasive imaging of hypoxia-inducible factor-1α gene therapy for myocardial ischemia

Hypoxia-inducible factor-1 alpha (HIF-1α) gene therapy holds great promise for the treatment of myocardial ischemia. Both preclinical and clinical evaluations of this therapy are underway and can benefit from a vector strategy that allows noninvasive assessment of HIF-1α expression as an objective measure of gene delivery. We have developed a novel bidirectional plasmid vector (pcTnT-HIF-1α-VP2-TSTA-fluc), which employs the cardiac troponin T (cTnT) promoter in conjunction with a two-step transcriptional amplification (TSTA) system to drive the linked expression of a recombinant HIF-1α gene (HIF-1α-VP2) and the firefly luciferase gene (fluc). The firefly luciferase (FLuc) activity serves as a surrogate for HIF-1α-VP2 expression, and can be noninvasively assessed in mice using bioluminescence imaging after vector delivery. Transfection of cultured HL-1 cardiomyocytes with pcTnT-HIF-1α-VP2-TSTA-fluc led to a strong correlation between FLuc and HIF-1α-dependent vascular endothelial growth factor expression (r(2)=0.88). Intramyocardial delivery of pcTnT-HIF-1α-VP2-TSTA-fluc into infarcted mouse myocardium led to persistent HIF-1α-VP2 expression for 4 weeks, even though it improved neither CD31+ microvessel density nor echocardiographically determined left ventricular systolic function. These results lend support to recent findings of suboptimal efficacy associated with plasmid-mediated HIF-1α therapy. The imaging techniques developed herein should be useful for further optimizing HIF-1α-VP2 therapy in preclinical models of myocardial ischemia.

Noninvasive monitoring of oxidative stress in transplanted mesenchymal stromal cells

OBJECTIVES

The goal of this study was to validate a pathway-specific reporter gene that could be used to noninvasively image the oxidative status of progenitor cells.

BACKGROUND

In cell therapy studies, reporter gene imaging plays a valuable role in the assessment of cell fate in living subjects. After myocardial injury, noxious stimuli in the host tissue confer oxidative stress to transplanted cells that may influence their survival and reparative function.

METHODS

Rat mesenchymal stromal cells (MSCs) were studied for phenotypic evidence of increased oxidative stress under in vitro stress. On the basis of their up-regulation of the pro-oxidant enzyme p67(phox) subunit of nicotinamide adenine dinucleotide phosphate (NAD[P]H oxidase p67(phox)), an oxidative stress sensor was constructed, comprising the firefly luciferase (Fluc) reporter gene driven by the NAD(P)H p67(phox) promoter. MSCs cotransfected with NAD(P)H p67(phox)-Fluc and a cell viability reporter gene (cytomegalovirus-Renilla luciferase) were studied under in vitro and in vivo pro-oxidant conditions.

RESULTS

After in vitro validation of the sensor during low-serum culture, transfected MSCs were transplanted into a rat model of myocardial ischemia/reperfusion (IR) and monitored by using bioluminescence imaging. Compared with sham controls (no IR), cardiac Fluc intensity was significantly higher in IR rats (3.5-fold at 6 h, 2.6-fold at 24 h, 5.4-fold at 48 h; p < 0.01), indicating increased cellular oxidative stress. This finding was corroborated by ex vivo luminometry after correcting for Renilla luciferase activity as a measure of viable MSC number (Fluc:Renilla luciferase ratio 0.011 ± 0.003 for sham vs. 0.026 ± 0.004 for IR at 48 h; p < 0.05). Furthermore, in IR animals that received MSCs preconditioned with an antioxidant agent (tempol), Fluc signal was strongly attenuated, substantiating the specificity of the oxidative stress sensor.

CONCLUSIONS

Pathway-specific reporter gene imaging allows assessment of changes in the oxidative status of MSCs after delivery to ischemic myocardium, providing a template to monitor key biological interactions between transplanted cells and their host environment in living subjects.

Molecular imaging: the key to advancing cardiac stem cell therapy

Cardiac stem cell therapy continues to hold promise for the treatment of ischemic heart disease despite the fact that early promising pre-clinical findings have yet to be translated into consistent clinical success. The latest human studies have collectively identified a pressing need to better understand stem cell behavior in humans and called for more incorporation of noninvasive imaging techniques into the design and evaluation of human stem cell therapy trials. This review discusses the various molecular imaging techniques validated to date for studying stem cells in living subjects, with a particular emphasis on their utilities in assessing the acute retention and the long-term survival of transplanted stem cells. These imaging techniques will be essential for advancing cardiac stem cell therapy by providing the means to both guide ongoing optimization and predict treatment response in humans.

Longitudinal, noninvasive imaging of T-cell effector function and proliferation in living subjects

Adoptive immunotherapy is evolving to assume an increasing role in treating cancer. Most imaging studies in adoptive immunotherapy to date have focused primarily on locating tumor-specific T cells rather than understanding their effector functions. In this study, we report the development of a noninvasive imaging strategy to monitor T-cell activation in living subjects by linking a reporter gene to the Granzyme B promoter (pGB), whose transcriptional activity is known to increase during T-cell activation. Because pGB is relatively weak and does not lead to sufficient reporter gene expression for noninvasive imaging, we specifically employed 2 signal amplification strategies, namely the Two Step Transcription Amplification (TSTA) strategy and the cytomegalovirus enhancer (CMVe) strategy, to maximize firefly luciferase reporter gene expression. Although both amplification strategies were capable of increasing pGB activity in activated primary murine splenocytes, only the level of bioluminescence activity achieved with the CMVe strategy was adequate for noninvasive imaging in mice. Using T cells transduced with a reporter vector containing the hybrid pGB-CMVe promoter, we were able to optically image T-cell effector function longitudinally in response to tumor antigens in living mice. This methodology has the potential to accelerate the study of adoptive immunotherapy in preclinical cancer models.

Indirect imaging of cardiac-specific transgene expression using a bidirectional two-step transcriptional amplification strategy

Transcriptional targeting for cardiac gene therapy is limited by the relatively weak activity of most cardiac-specific promoters. We have developed a bidirectional plasmid vector, which uses a two-step transcriptional amplification (TSTA) strategy to enhance the expression of two optical reporter genes, firefly luciferase (fluc) and Renilla luciferase (hrluc), driven by the cardiac troponin T (cTnT) promoter. The vector was characterized in vitro and in living mice using luminometry and bioluminescence imaging to assess its ability to mediate strong, correlated reporter gene expression in a cardiac cell line and the myocardium, while minimizing expression in non-cardiac cell lines and the liver. In vitro, the TSTA system significantly enhanced cTnT-mediated reporter gene expression with moderate preservation of cardiac specificity. After intramyocardial and hydrodynamic tail vein delivery of an hrluc-enhanced variant of the vector, long-term fluc expression was observed in the heart, but not in the liver. In both the cardiac cell line and the myocardium, fluc expression correlated well with hrluc expression. These results show the vector's ability to effectively amplify and couple transgene expression in a cardiac-specific manner. Further replacement of either reporter gene with a therapeutic gene should allow non-invasive imaging of targeted gene therapy in living subjects.

Antioxidants improve early survival of cardiomyoblasts after transplantation to the myocardium

PURPOSE

We tested the hypothesis that modulation of the microenvironment (using antioxidants) will increase stem cell survival in hypoxia and after transplantation to the myocardium.

PROCEDURES

Rat cardiomyoblasts were stably transfected with a reporter gene (firefly luciferase) for bioluminescence imaging (BLI). First, we examined the role of oxidative stress in cells under hypoxic conditions. Subsequently, stem cells were transplanted to the myocardium of rats using high-resolution ultrasound, and their survival was monitored daily using BLI.

RESULTS

Under hypoxia, oxidative stress was increased together with decreased cell survival compared to control cells, both of which were preserved by antioxidants. In living subjects, oxidative stress blockade increased early cell survival after transplantation to the myocardium, compared to untreated cells/animals.

CONCLUSION

Modulation of the local microenvironment (with antioxidants) improves stem cell survival. Increased understanding of the interaction between stem cells and their microenvironment will be critical to advance the field of regenerative medicine.

Visualizing implanted tumors in mice with magnetic resonance imaging using magnetotactic bacteria

PURPOSE

To determine if magnetotactic bacteria can target tumors in mice and provide positive contrast for visualization using magnetic resonance imaging.

EXPERIMENTAL DESIGN

The ability of the magnetotactic bacterium, Magnetospirillum magneticum AMB-1 (referred to from here as AMB-1), to confer positive magnetic resonance imaging contrast was determined in vitro and in vivo. For the latter studies, AMB-1 were injected either i.t. or i.v. Bacterial growth conditions were manipulated to produce small (approximately 25-nm diameter) magnetite particles, which were observed using transmission electron microscopy. Tumor targeting was confirmed using 64Cu-labeled bacteria and positron emission tomography and by determination of viable cell counts recovered from different organs and the tumor.

RESULTS

We show that AMB-1 bacteria with small magnetite particles generate T1-weighted positive contrast, enhancing in vivo visualization by magnetic resonance imaging. Following i.v. injection of 64Cu-labeled AMB-1, positron emission tomography imaging revealed increasing colonization of tumors and decreasing infection of organs after 4 hours. Viable cell counts showed that, by day 6, the bacteria had colonized tumors but were cleared completely from other organs. Magnetic resonance imaging showed a 1.22-fold (P = 0.003) increased positive contrast in tumors on day 2 and a 1.39-fold increase (P = 0.0007) on day 6.

CONCLUSION

Magnetotactic bacteria can produce positive magnetic resonance imaging contrast and colonize mouse tumor xenografts, providing a potential tool for improved magnetic resonance imaging visualization in preclinical and translational studies to track cancer.

Noninvasive evaluation of immunosuppressive drug efficacy on acute donor cell survival

PURPOSE

The therapeutic benefits of cell transplantation may depend on the survival of sufficient numbers of grafted cells. We evaluate four potent immunosuppressive medications aimed at preventing acute donor cell death.

PROCEDURES AND RESULTS

Embryonic rat H9c2 myoblasts were stably transduced to express firefly luciferase reporter gene (H9c2-Fluc). H9c2-Fluc cells (3x10(6)) were injected into thigh muscles of Sprague-Dawley rats (N=30) treated with cyclosporine, dexamethasone, mycophenolate mofetil, tacrolimus, or saline from day -3 to day +14. Longitudinal optical bioluminescence imaging was performed over two weeks. Fluc activity was 40.0+/-12.1% (dexamethasone), 30.5+/-12.5% (tacrolimus), and 21.5+/-3.5% (mycophenolate) vs. 12.0+/-5.0% (control) and 8.3+/-5.0% (cyclosporine) at day 4 (P<0.05). However, by day 14, cell signals had decreased drastically to <10% for all groups despite drug therapy.

CONCLUSION

This study demonstrates the ability of optical molecular imaging for tracking cell survival noninvasively and raises important questions with regard to the overall efficacy of immunosuppressives for prolonging transplanted cell survival.

Imaging gene expression in human mesenchymal stem cells: from small to large animals

PURPOSE

To evaluate the feasibility of reporter gene imaging in implanted human mesenchymal stem cells (MSCs) in porcine myocardium by using clinical positron emission tomography (PET)-computed tomography (CT) scanning.

MATERIALS AND METHODS

Animal protocols were approved by the Institutional Administrative Panel on Laboratory Animal Care. Transduction of human MSCs by using different doses of adenovirus that contained a cytomegalovirus (CMV) promoter driving the mutant herpes simplex virus type 1 thymidine kinase reporter gene (Ad-CMV-HSV1-sr39tk) was characterized in a cell culture. A total of 2.25 x 10(6) transduced (n = 5) and control nontransduced (n = 5) human MSCs were injected into the myocardium of 10 rats, and reporter gene expression in human MSCs was visualized with micro-PET by using the radiotracer 9-(4-[fluorine 18]-fluoro-3-hydroxymethylbutyl)-guanine (FHBG). Different numbers of transduced human MSCs suspended in either phosphate-buffered saline (PBS) (n = 4) or matrigel (n = 5) were injected into the myocardium of nine swine, and gene expression was visualized with a clinical PET-CT. For analysis of cell culture experiments, linear regression analyses combined with a t test were performed. To test differences in radiotracer uptake between injected and remote myocardium in both rats and swine, one-sided paired Wilcoxon tests were performed. In swine experiments, a linear regression of radiotracer uptake ratio on the number of injected transduced human MSCs was performed.

RESULTS

In cell culture, there was a viral dose-dependent increase of gene expression and FHBG accumulation in human MSCs. Human MSC viability was 96.7% (multiplicity of infection, 250). Cardiac FHBG uptake in rats was significantly elevated (P < .0001) after human MSC injection (0.0054% injected dose [ID]/g +/- 0.0007 [standard deviation]) compared with that in the remote myocardium (0.0003% ID/g +/- 0.0001). In swine, myocardial radiotracer uptake was not elevated after injection of up to 100 x 10(6) human MSCs (PBS group). In the matrigel group, signal-to-background ratio increased to 1.87 after injection of 100 x 10(6) human MSCs and positively correlated (R(2) = 0.97, P < .001) with the number of administered human MSCs.

CONCLUSION

Reporter gene imaging in human MSCs can be translated to large animals. The study highlights the importance of co-administering a "scaffold" for increasing intramyocardial retention of human MSCs.

In vivo serial evaluation of superparamagnetic iron-oxide labeled stem cells by off-resonance positive contrast

MRI is emerging as a diagnostic modality to track iron-oxide-labeled stem cells. This study investigates whether an off-resonance (OR) pulse sequence designed to generate positive contrast at 1.5T can assess the location, quantity, and viability of delivered stem cells in vivo. Using mouse embryonic stem cell transfected with luciferase reporter gene (luc-mESC), multimodality validation of OR signal was conducted to determine whether engraftment parameters of superparamagnetic iron-oxide labeled luc-mESC (SPIO-luc-mESC) could be determined after cell transplantation into the mouse hindlimb. A significant increase in signal- and contrast-to-noise of the SPIO-luc-mESC was achieved with the OR technique when compared to a gradient recalled echo (GRE) sequence. A significant correlation between the quantity of SPIO-luc-mESC and OR signal was observed immediately after transplantation (R(2) = 0.74, P < 0.05). The assessment of transplanted cell viability by bioluminescence imaging (BLI) showed a significant increase of luciferase activities by day 16, while the MRI signal showed no difference. No significant correlation between BLI and MRI signals of cell viability was observed. In conclusion, using an OR sequence the precise localization and quantitation of SPIO-labeled stem cells in both space and time were possible. However, the OR sequence did not allow evaluation of cell viability.

Comparison of optical bioluminescence reporter gene and superparamagnetic iron oxide MR contrast agent as cell markers for noninvasive imaging of cardiac cell transplantation

PURPOSE

In this study, we compared firefly luciferase (Fluc) reporter gene and superparamagnetic iron oxide (Feridex) as cell markers for longitudinal monitoring of cardiomyoblast graft survival using optical bioluminescence imaging (BLI) and magnetic resonance imaging (MRI), respectively.

PROCEDURES

Rats (n = 31) underwent an intramyocardial injection of cardiomyoblasts (2 x 10(6)) labeled with Fluc, Feridex, or no marker (control) or an injection of Feridex alone (75 microg). Afterward, rats were serially imaged with BLI or MRI and killed at different time points for histological analysis.

RESULTS

BLI revealed a drastically different cell survival kinetics (half-life = 2.65 days over 6 days) than that revealed by MRI (half-life = 16.8 days over 80 days). Injection of Feridex alone led to prolonged tissue retention of Feridex (> or =16 days) and persistent MR signal (> or =42 days).

CONCLUSIONS

Fluc BLI reporter gene imaging is a more accurate gauge of transplanted cell survival as compared to MRI of Feridex-labeled cells.

Imaging of VEGF receptor in a rat myocardial infarction model using PET

Myocardial infarction (MI) leads to left ventricular (LV) remodeling, which leads to the activation of growth factors such as vascular endothelial growth factor (VEGF). However, the kinetics of a growth factor's receptor expression, such as VEGF, in the living subject has not yet been described. We have developed a PET tracer (64Cu-DOTA-VEGF121 [DOTA is 1,4,7,10-tetraazadodecane-N,N',N'',N'''-tetraacetic acid]) to image VEGF receptor (VEGFR) expression after MI in the living subject.

METHODS

In Sprague-Dawley rats, MI was induced by ligation of the left coronary artery and confirmed by ultrasound (n = 8). To image and study the kinetics of VEGFRs, 64Cu-DOTA-VEGF121 PET scans were performed before MI induction (baseline) and on days 3, 10, 17, and 24 after MI. Sham-operated animals served as controls (n = 3).

RESULTS

Myocardial origin of the 64Cu-DOTA-VEGF121 signal was confirmed by CT coregistration and autoradiography. VEGFR specificity of the 64Cu-DOTA-VEGF121 probe was confirmed by in vivo use of a 64Cu-DOTA-VEGFmutant. Baseline myocardial uptake of 64Cu-DOTA-VEGF121 was minimal (0.30 +/- 0.07 %ID/g [percentage injected dose per gram of tissue]); it increased significantly after MI (day 3, 0.97 +/- 0.05 %ID/g; P < 0.05 vs. baseline) and remained elevated for 2 wk (up to day 17 after MI), after which time it returned to baseline levels.

CONCLUSION

We demonstrate the feasibility of imaging VEGFRs in the myocardium. In summary, we imaged and described the kinetics of 64Cu-DOTA-VEGF121 uptake in a rat model of MI. Studies such as the one presented here will likely play a major role when studying pathophysiology and assessing therapies in different animal models of disease and, potentially, in patients.