Mesenchymal STRO-1/STRO-3+ precursor cells for the treatment of chronic heart failure with reduced ejection fraction

The heart is susceptible to proinflammatory and profibrotic responses after myocardial injury, leading to further worsening of cardiac dysfunction. Important developments in the management of heart failure with reduced ejection fraction have reduced morbidity and mortality; however, these therapies focus on optimizing cardiac function through hemodynamic and neurohormonal pathways and not by repairing the underlying cardiac injury. The potential of cell-based therapy to reverse cardiac injury has received substantial attention. Herein are examined the phase II and III studies of bone marrow-derived mesenchymal STRO-1+ or STRO-1/STRO-3+ precursor cells in patients with ischemic and nonischemic heart failure with reduced ejection fraction, addressing the safety and efficacy of cell-based therapy throughout multiple clinical trials, the optimal dose and the steps toward revolutionizing the treatment of heart failure.

Stem cell therapy for acute myocardial infarction: Mesenchymal Stem Cells and induced Pluripotent Stem Cells

INTRODUCTION

Acute myocardial infarction (AMI) remains a leading cause of death in the United States. The limited capacity of cardiomyocytes to regenerate and the restricted contractility of scar tissue after AMI are not addressed by current pharmacologic interventions. Mesenchymal stem/stromal cells (MSCs) have emerged as a promising therapeutic approach due to their low antigenicity, ease of harvesting, and efficacy and safety in preclinical and clinical studies, despite their low survival and engraftment rates. Other stem cell types, such as induced pluripotent stem cells (iPSCs) also show promise, and optimizing cardiac repair requires integrating emerging technologies and strategies.

AREAS COVERED

This review offers insights into advancing cell-based therapies for AMI, emphasizing meticulously planned trials with a standardized definition of AMI, for a bench-to-bedside approach. We critically evaluate fundamental studies and clinical trials to provide a comprehensive overview of the advances, limitations and prospects for cell-based therapy in AMI.

EXPERT OPINION

MSCs continue to show potential promise for treating AMI and its sequelae, but addressing their low survival and engraftment rates is crucial for clinical success. Integrating emerging technologies such as pluripotent stem cells and conducting well-designed trials will harness the full potential of cell-based therapy in AMI management. Collaborative efforts are vital to developing effective stem cell therapies for AMI patients.

Efficacy of a growth hormone-releasing hormone agonist in a murine model of cardiometabolic heart failure with preserved ejection fraction

Heart failure (HF) with preserved ejection fraction (HFpEF) represents a major unmet medical need owing to its diverse pathophysiology and lack of effective therapies. Potent synthetic, agonists (MR-356 and MR-409) of growth hormone-releasing hormone (GHRH) improve the phenotype of models of HF with reduced ejection fraction (HFrEF) and in cardiorenal models of HFpEF. Endogenous GHRH exhibits a broad range of regulatory influences in the cardiovascular (CV) system and aging and plays a role in several cardiometabolic conditions including obesity and diabetes. Whether agonists of GHRH can improve the phenotype of cardiometabolic HFpEF remains untested and unknown. Here we tested the hypothesis that MR-356 can mitigate/reverse the cardiometabolic HFpEF phenotype. C57BL6N mice received a high-fat diet (HFD) plus the nitric oxide synthase inhibitor (l-NAME) for 9 wk. After 5 wk of HFD + l-NAME regimen, animals were randomized to receive daily injections of MR-356 or placebo during a 4-wk period. Control animals received no HFD + l-NAME or agonist treatment. Our results showed the unique potential of MR-356 to treat several HFpEF-like features including cardiac hypertrophy, fibrosis, capillary rarefaction, and pulmonary congestion. MR-356 improved cardiac performance by improving diastolic function, global longitudinal strain (GLS), and exercise capacity. Importantly, the increased expression of cardiac pro-brain natriuretic peptide (pro-BNP), inducible nitric oxide synthase (iNOS), and vascular endothelial growth factor-A (VEGF-A) was restored to normal levels suggesting that MR-356 reduced myocardial stress associated with metabolic inflammation in HFpEF. Thus, agonists of GHRH may be an effective therapeutic strategy for the treatment of cardiometabolic HFpEF phenotype.NEW & NOTEWORTHY This randomized study used rigorous hemodynamic tools to test the efficacy of a synthetic GHRH agonist to improve cardiac performance in a cardiometabolic HFpEF. Daily injection of the GHRH agonist, MR-356, reduced the HFpEF-like effects as evidenced by improved diastolic dysfunction, reduced cardiac hypertrophy, fibrosis, and pulmonary congestion. Notably, end-diastolic pressure and end-diastolic pressure-volume relationship were reset to control levels. Moreover, treatment with MR-356 increased exercise capacity and reduced myocardial stress associated with metabolic inflammation in HFpEF.

Synthetic growth hormone-releasing hormone agonist ameliorates the myocardial pathophysiology characteristic of heart failure with preserved ejection fraction

AIMS

To test the hypothesis that the activation of the growth hormone-releasing hormone (GHRH) receptor signalling pathway within the myocardium both prevents and reverses diastolic dysfunction and pathophysiologic features consistent with heart failure with preserved ejection fraction (HFpEF). Impaired myocardial relaxation, fibrosis, and ventricular stiffness, among other multi-organ morbidities, characterize the phenotype underlying the HFpEF syndrome. Despite the rapidly increasing prevalence of HFpEF, few effective therapies have emerged. Synthetic agonists of the GHRH receptors reduce myocardial fibrosis, cardiomyocyte hypertrophy, and improve performance in animal models of ischaemic cardiomyopathy, independently of the growth hormone axis.

METHODS AND RESULTS

CD1 mice received 4- or 8-week continuous infusion of angiotensin-II (Ang-II) to generate a phenotype with several features consistent with HFpEF. Mice were administered either vehicle or a potent synthetic agonist of GHRH, MR-356 for 4-weeks beginning concurrently or 4-weeks following the initiation of Ang-II infusion. Ang-II-treated animals exhibited diastolic dysfunction, ventricular hypertrophy, interstitial fibrosis, and normal ejection fraction. Cardiomyocytes isolated from these animals exhibited incomplete relaxation, depressed contractile responses, altered myofibrillar protein phosphorylation, and disturbed calcium handling mechanisms (ex vivo). MR-356 both prevented and reversed the development of the pathological phenotype in vivo and ex vivo. Activation of the GHRH receptors increased cAMP and cGMP in cardiomyocytes isolated from control animals but only cAMP in cardiac fibroblasts, suggesting that GHRH-A exert differential effects on cardiomyocytes and fibroblasts.

CONCLUSION

These findings indicate that the GHRH receptor signalling pathway(s) represents a new molecular target to counteract dysfunctional cardiomyocyte relaxation by targeting myofilament phosphorylation and fibrosis. Accordingly, activation of GHRH receptors with potent, synthetic GHRH agonists may provide a novel therapeutic approach to management of the myocardial alterations associated with the HFpEF syndrome.

S-Nitrosoglutathione Reductase Deficiency Causes Aberrant Placental S-Nitrosylation and Preeclampsia

Background

Preeclampsia, a leading cause of maternal and fetal mortality and morbidity, is characterized by an increase in S‐nitrosylated proteins and reactive oxygen species, suggesting a pathophysiologic role for dysregulation in nitrosylation and nitrosative stress.

Methods and Results

Here, we show that mice lacking S‐nitrosoglutathione reductase (GSNOR^−⁄−), a denitrosylase regulating protein S‐nitrosylation, exhibit a preeclampsia phenotype, including hypertension, proteinuria, renal pathology, cardiac concentric hypertrophy, decreased placental vascularization, and fetal growth retardation. Reactive oxygen species, NO, and peroxynitrite levels are elevated. Importantly, mass spectrometry reveals elevated placental S‐nitrosylated amino acid residues in GSNOR^−⁄− mice. Ascorbate reverses the phenotype except for fetal weight, reduces the difference in the S‐nitrosoproteome, and identifies a unique set of S‐nitrosylated proteins in GSNOR^−⁄− mice. Importantly, human preeclamptic placentas exhibit decreased GSNOR activity and increased nitrosative stress.

Conclusions

Therefore, deficiency of GSNOR creates dysregulation of placental S‐nitrosylation and preeclampsia in mice, which can be rescued by ascorbate. Coupled with similar findings in human placentas, these findings offer valuable insights and therapeutic implications for preeclampsia.

OUP accepted manuscript

Background

Left ventricular hypertrophy and heart failure with preserved ejection fraction (HFpEF) are primary manifestations of the cardiorenal syndrome in patients with chronic kidney disease (CKD). Therapies that improve morbidity and mortality in HFpEF are lacking. Cell-based therapies promote cardiac repair in ischemic and non-ischemic cardiomyopathies. We hypothesized that cell-based therapy ameliorates CKD-induced HFpEF.

Methods and Results

Yorkshire pigs (n = 26) underwent 5/6 embolization-mediated nephrectomy. CKD was confirmed by increased creatinine and decreased glomerular filtration rate (GFR). Mean arterial pressure (MAP) was not different between groups from baseline to 4 weeks. HFpEF was evident at 4 weeks by increased LV mass, relative wall thickening, end-diastolic pressure, and end-diastolic pressure-volume relationship, with no change in ejection fraction (EF). Four weeks post-embolization, allogeneic (allo) bone marrow-derived mesenchymal stem cells (MSC; 1 × 10⁷ cells), allo-kidney-derived stem cells (KSC; 1 × 10⁷ cells), allo-cell combination therapy (ACCT; MSC + KSC; 1:1 ratio; total = 1 × 10⁷ cells), or placebo (Plasma-Lyte) was delivered via intra-renal artery. Eight weeks post-treatment, there was a significant increase in MAP in the placebo group (21.89 ± 6.05 mmHg) compared to the ACCT group. GFR significantly improved in the ACCT group. EF, relative wall thickness, and LV mass did not differ between groups at 12 weeks. EDPVR improved in the ACCT group, indicating decreased ventricular stiffness.

Conclusions

Intra-renal artery allogeneic cell therapy was safe in a CKD swine model manifesting the characteristics of HFpEF. The beneficial effect on renal function and ventricular compliance in the ACCT group supports further research of cell therapy for cardiorenal syndrome.

Mechanism of Action of Mesenchymal Stem Cells (MSCs): impact of delivery method

INTRODUCTION

Mesenchymal stromal cells (MSCs; AKA mesenchymal stem cells) stimulate healing and reduce inflammation. Promising therapeutic responses are seen in many late-phase clinical trials, but others have not satisfied their primary endpoints, making translation of MSCs into clinical practice difficult. These inconsistencies may be related to the route of MSC delivery, lack of product optimization, or varying background therapies received in clinical trials over time.

AREAS COVERED

Here we discuss the different routes of MSC delivery, highlighting the proposed mechanism(s) of therapeutic action as well as potential safety concerns. PubMed search criteria used: MSC plus: local administration; routes of administration; delivery methods; mechanism of action; therapy in different diseases.

EXPERT OPINION

Direct injection of MSCs using a controlled local delivery approach appears to have benefits in certain disease states, but further studies are required to make definitive conclusions regarding the superiority of one delivery method over another.

S-nitrosoglutathione reductase (GSNOR) deficiency accelerates cardiomyocyte differentiation of induced pluripotent stem cells

Introduction

Induced pluripotent stem cells (iPSCs) provide a model of cardiomyocyte (CM) maturation. Nitric oxide signaling promotes CM differentiation and maturation, although the mechanisms remain controversial.

Aim

The study tested the hypothesis that in the absence of S-nitrosoglutathione reductase (GSNOR), a denitrosylase regulating protein S-nitrosylation, the resultant increased S-nitrosylation accelerates the differentiation and maturation of iPSC-derived cardiomyocytes (CMs).

Methods and Results

iPSCs derived from mice lacking GSNOR (iPSC^GSNOR-/-) matured faster than wildtype iPSCs (iPSC^WT) and demonstrated transient increases in expression of murine Snail Family Transcriptional Repressor 1 gene (Snail), murine Snail Family Transcriptional Repressor 2 gene (Slug) and murine Twist Family BHLH Transcription Factor 1 gene (Twist), transcription factors that promote epithelial-to-mesenchymal transition (EMT) and that are regulated by Glycogen Synthase Kinase 3 Beta (GSK3β). Murine Glycogen Synthase Kinase 3 Beta (Gsk3β) gene exhibited much greater S-nitrosylation, but lower expression in iPSC^GSNOR-/-. S-nitrosoglutathione (GSNO)-treated iPSC^WT and human (h)iPSCs also demonstrated reduced expression of GSK3β. Nkx2.5 expression, a CM marker, was increased in iPSC^GSNOR-/- upon directed differentiation toward CMs on Day 4, whereas murine Brachyury (t), Isl1, and GATA Binding Protein (Gata4) mRNA were decreased, compared to iPSC^WT, suggesting that GSNOR deficiency promotes CM differentiation beginning immediately following cell adherence to the culture dish-transitioning from mesoderm to cardiac progenitor.

Conclusion

Together these findings suggest that increased S-nitrosylation of Gsk3β promotes CM differentiation and maturation from iPSCs. Manipulating the post-translational modification of GSK3β may provide an important translational target and offers new insight into understanding of CM differentiation from pluripotent stem cells.

One sentence summary

Deficiency of GSNOR or addition of GSNO accelerates early differentiation and maturation of iPSC-cardiomyocytes.

Neuregulin-1, in a Conducive Milieu with Wnt/BMP/Retinoic Acid, Prolongs the Epicardial-Mediated Cardiac Regeneration Capacity of Neonatal Heart Explants

Rationale: Cardiac sympathetic nerves are required for endogenous repair of the mammalian neonatal heart in vivo, but the underlying mechanism is unclear. Objective: We tested the hypothesis that a combination of cardiac developmental growth factors Wnt3a, BMP4 and Neuregulin (NRG-1), compensate for denervation and support cardiac regeneration in explanted neonatal mammalian hearts. Methods and Results: Hearts from 2-day old neonatal mice were harvested, lesioned at the apex and grown ex vivo for 21 days under defined conditions. Hearts grown in canonical cardiomyocyte culture media underwent complete coagulative necrosis, a process resembling ischemic cell death, by day 14. However, the addition of Wnt3a, BMP-4 and NRG-1, maintained cellular integrity and restored the endogenous regenerative program. None of these factors alone, or in any paired combination, were sufficient to induce regeneration in culture. rNRG-1 alone significantly reduced the accumulation of double strand DNA damage at Day 3; (-NRG-1: 60±12%; +NRG-1: 8±3%; P<0.01) and prevented coagulative necrosis at Day 14. Short-term addition of rWnt3a and rBMP-4 (day 0-3, NRG-1+) increased WT1 expression (a marker of epicardial cells) 7-fold, epicardial proliferation (78±17 cells vs. 21±9 cells; P<0.05), migration and recellularization (80±22 vs. zero cells; P<0.01; n=6) at the injury site on day 14. Conclusions: A novel explant culture system maintains three-dimensional neonatal mouse hearts and the mammalian neonatal cardiac regenerative program ex vivo. We identified that rNRG-1, plus short-term activation of Wnt- and BMP-signaling, promotes cardiac repair via epicardial cell activation, their proliferation and migration to the injury site, followed by putative cardiomyocyte recruitment. This novel technique will facilitate future studies of mammalian cardiac regeneration and may be useful in cardiac-specific drug testing.

The impact of patient sex on the response to intramyocardial mesenchymal stem cell administration in patients with non-ischaemic dilated cardiomyopathy

AIMS

Sex differences impact the occurrence, presentation, prognosis, and response to therapy in heart disease. Particularly, the phenotypic presentation of patients with non-ischaemic dilated cardiomyopathy (NIDCM) differs between men and women. However, whether the response to mesenchymal stem cell (MSC) therapy is influenced by sex remains unknown. We hypothesize that males and females with NIDCM respond similarly to MSC therapy.

METHODS AND RESULTS

Male (n = 24) and female (n = 10) patients from the POSEIDON-DCM trial who received MSCs via transendocardial injections were evaluated over 12 months. Endothelial function was measured at baseline and 3 months post-transendocardial stem cell injection (TESI). At baseline, ejection fraction (EF) was lower (P = 0.004) and end-diastolic volume (EDV; P = 0.0002) and end-systolic volume (ESV; P = 0.0002) were higher in males vs. females. In contrast, baseline demographic characteristics, Minnesota Living with Heart Failure Questionnaire (MLHFQ), and 6-min walk test (6MWT) were similar between groups. EF improved in males by 6.2 units (P = 0.04) and in females by 8.6 units (P = 0.04; males vs. females, P = 0.57). EDV and ESV were unchanged over time. The MLHFQ score, New York Heart Association (NYHA) class, endothelial progenitor cell-colony forming units, and serum tumour necrosis factor alpha improved similarly in both groups.

CONCLUSION

Despite major differences in phenotypic presentation of NIDCM in males and females, this study is the first of its kind to demonstrate that MSC therapy improves a variety of parameters in NIDCM irrespective of patient sex. These findings have important clinical and pathophysiologic implications regarding the impact of sex on responses to cell-based therapy for NIDCM.

Abstract 471: Combination of Allogeneic Mesenchymal and Kidney Stem Cells Ameliorates Chronic Kidney Disease Induced Heart Failure With Preserved Ejection Fraction

Background: Heart failure with preserved ejection fraction (HFpEF) is a heterogeneous condition involving multiple comorbidities. Phenotypic classification of HFpEF associated with chronic kidney disease (CKD) manifests worse outcomes, compared to other HFpEF phenotypes. Few treatments improve morbidity and mortality in HFpEF. Stem cell therapy promotes cardiac repair in ischemic and non-ischemic cardiomyopathies. We hypothesized that allogeneic stem cell treatment ameliorates HFpEF in a large animal model of CKD.

Methods: Yorkshire pigs (n=26) underwent 5/6 embolization-mediated nephrectomy and 4-weeks later received either: allogeneic mesenchymal stem cells (MSCs) (10х10 6 ), Kidney stem cells (KSC; 10х10 6 ), combination (ACCT; MSC+KSC; 1:1 ratio [5х10 6 each]), or placebo (n=6-7/ group). Cell therapy was delivered via the patent renal artery of the remnant kidney. RNAsec analysis compared placebo and ACCT groups.

Results: Mean arterial pressure increased significantly in the placebo- (21.89±6.05 mmHg, p<0.0001) compared to the ACCT-group (p=0.04) at 12 weeks. Glomerular filtration rate improved significantly in the ACCT group (p=0.002). RNAseq analysis revealed a significant decrease in genes normally increased during kidney transplant rejection (q<10 -6 , NES = -2.32) in ACCT. Consistent with these results, there was a downregulation of canonical drivers of tubular damage and regeneration, including SOX9 (-2.39 fold, p=0.0004) and apoptosis of kidney cell types (-24.89 fold, p=0.004), including podocytes (-2.065 fold, p=0.04) with ACCT. ACCT administration also downregulated genes related to oxidative stress (-4.6 fold, p<0.0001), fibrosis, inflammatory response (-4.760 fold, p=<0.05), and renin-angiotensin signaling (-3.162 fold, p=0.024), which are related to cardiac hypertrophy pathways (-7.23, fold, p<0.0001). EDPVR improved in with ACCT (p=0.003), indicating decreased ventricular stiffness. Ejection fraction, relative wall thickness, and left ventricular mass did not differ between groups at 12 weeks.

Conclusion: Intra-renal artery allogeneic cell therapy was safe. Beneficial effects were observed in the ACCT and MSC groups in the kidney and heart. These findings have important implications on the use of cell therapy for HFpEF and cardiorenal syndrome.

Clinical-based Cell Therapies for Heart Disease-Current and Future State

Patients have an ongoing unmet need for effective therapies that reverse the cellular and functional damage associated with heart damage and disease. The discovery that ~1%-2% of adult cardiomyocytes turn over per year provided the impetus for treatments that stimulate endogenous repair mechanisms that augment this rate. Preclinical and clinical studies provide evidence that cell-based therapy meets these therapeutic criteria. Recent and ongoing studies are focused on determining which cell type(s) works best for specific patient population(s) and the mechanism(s) by which these cells promote repair. Here we review clinical and preclinical stem cell studies and anticipate future directions of regenerative medicine for heart disease.

Mesenchymal Stem Cell Secretion of SDF-1α Modulates Endothelial Function in Dilated Cardiomyopathy

Background

Endothelial dysfunction contributes to the pathophysiology of dilated cardiomyopathy (DCM). Allogeneic but not autologous mesenchymal stem cells (MSCs) improve endothelial function in DCM patients. We hypothesized that these effects are modulated by release of stromal derived factor-1α (SDF-1α).

Methods

Plasma TNFα and endothelial progenitor cell-colony forming units (EPC-CFUs) were assessed at baseline and 3-months post-injection in a subset of POSEIDON-DCM patients that received autologous (n = 11) or allogeneic (n = 10) MSCs. SDF-1α secretion by MSCs, endothelial cell (EC) TNFα mRNA expression, and levels of reactive oxygen species (ROS) in response to SDF-1α were measured in vitro.

Results

As previously shown, DCM patients (n = 21) had reduced EPC-CFUs at baseline (3 ± 3), which were restored to normal by allogeneic MSCs 3-months post-treatment (Δ10 ± 4). DCM patients had elevated baseline plasma TNFα (n = 15, 22 ± 9.4 pg/mL). Allogeneic MSCs (n = 8) decreased, and autologous MSCs (n = 7) increased, plasma TNFα (−7.1 ± 3.1 vs. 22.2 ± 17.1 pg/mL, respectively; P = 0.0005). In culture, autologous MSCs (n = 11) secreted higher levels of SDF-1α than allogeneic MSCs (n = 6) [76.0 (63.7, 100.9) vs. 22.8 (7.2, 43.5) pg/mL, P = 0.0002]. SDF-1α and plasma TNFα negatively correlated with EPC-CFUs in both treatment groups (R = −0.7, P = 0.0004). ECs treated with 20 ng SDF-1α expressed lower levels of TNFα mRNA than cells treated with 100 ng (0.7 ± 0.2 vs. 2.1 ± 0.3, P = 0.0008). SDF-1α at low but not high concentration inhibited the generation of ROS.

Conclusion

MSC secretion of SDF-1α inversely correlates with EPC-CFU production in DCM patients and therefore may be a modulator of MSC therapeutic effect in this clinical setting.

Clinical Trial Registration

https://clinicaltrials.gov/ct2/show/NCT01392625, identifier NCT01392625.

Preclinical Studies of Stem Cell Therapy for Heart Disease

As part of the TACTICS (Transnational Alliance for Regenerative Therapies in Cardiovascular Syndromes) series to enhance regenerative medicine, here, we discuss the role of preclinical studies designed to advance stem cell therapies for cardiovascular disease. The quality of this research has improved over the past 10 to 15 years and overall indicates that cell therapy promotes cardiac repair. However, many issues remain, including inability to provide complete cardiac recovery. Recent studies question the need for intact cells suggesting that harnessing what the cells release is the solution. Our contribution describes important breakthroughs and current directions in a cell-based approach to alleviating cardiovascular disease.

Abstract 420: S-nitrosylation Promotes Cell Cycle, Cell Viability and Proliferation by Activating the Snail/Slug Pathway in miPSC-derived CM

Introduction: Epithelial-to-mesenchymal transition (EMT), is a crucial step in cardiac differentiation. Snail and Slug are increased and E-cadherin is decreased during EMT. Expression of Snail and Slug is reduced by GSK3β, a key regulator of the Wnt/β-catenin signaling pathway. S-nitrosylation (S-NO) of GSK3β inhibits its activity.

Objective: We hypothesized that in the absence of S-nitrosoglutathione reductase (GSNOR), the Snail/Slug pathway is activated in miPSC-derived cardiomyocytes.

Methods: We compared the initial growth and differentiation of iPSCs derived from GSNOR –/– (iPSC GSNOR-/- ) and wild type (WT [control], iPSC WT ) mice on days (D) 0-6 in cell culture. Cell morphology was assessed and MTT, BrdU and transwell invasion assays performed to determine cell proliferation, invasion and migration. EMT-related transcription factors and members of the GSK3β pathway were measured at D0-D6.

Results: During early differentiation, iPSC GSNOR-/- cells exhibited accelerated loss of pluripotency markers and, from D4, greater proliferation/differentiation, and apparent EMT compared to iPSC WT . MTT, BrdU and migration assays demonstrated that loss of GSNOR stimulated cell proliferation and migration. Slug and Snail were upregulated and E-Cadherin was downregulated in iPSC GSNOR-/- suggesting that increased NO levels reduced GSK3β activity in iPSC GSNOR-/- .

Conclusions: Our results suggest that the deletion of GSNOR affects early CM differentiation and promote EMT. These findings have important implications for regenerative medicine and provide new targets for iPSC-based therapy.

Intravascular Stem Cell Bioreactor for Prevention of Adverse Remodeling After Myocardial Infarction

Background Prevention of adverse remodeling after myocardial infarction (MI) is an important goal of stem cell therapy. Clinical trial results vary, however, and poor cell retention and survival after delivery likely limit the opportunity to exert beneficial effects. To overcome these limitations, we built an implantable intravascular bioreactor (IBR) designed to protect contained cells from washout, dilution, and immune attack while allowing sustained release of beneficial paracrine factors. Methods and Results IBRs were constructed using semipermeable membrane adhered to a clinical-grade catheter shaft. Mesenchymal stem cell (MSC) viability in and paracrine factor release from IBRs were assessed in vitro and IBR biocompatibility and immune protection confirmed in vivo. In a porcine anterior MI model, IBRs containing 25 million allogeneic MSCs (IBR-MSCs) were compared with IBRs containing media alone (IBR-Placebo; n=8 per group) with adverse remodeling assessed by magnetic resonance imaging. Four weeks after MI, IBR-MSCs had no significant change in end-diastolic volume (+0.33±4.32 mL; P=0.89), end-systolic volume (+2.14±4.13 mL; P=0.21), and left ventricular ejection fraction (-2.27±2.94; P=0.33) while IBR-Placebo had significant increases in end-diastolic volume (+10.37±3.84 mL; P=0.01) and ESV (+11.35±2.88 mL; P=0.01), and a significant decrease in left ventricular ejection fraction (-5.78±1.70; P=0.025). Eight weeks after MI, adherent pericarditis was present in 0 of 8 IBR-MSCs versus 4 of 8 IBR-Placebo (P=0.02), suggesting an anti-inflammatory effect. In a separate study, 25 million allogeneic pig MSCs directly injected in the peri-infarct zone 3 days after MI (n=6) showed no significant benefit in adverse remodeling at 4 weeks compared with IBR-MSCs. Conclusions MSCs deployed inside an implantable, removable, and potentially rechargeable bioreactor in a large animal model remain viable, are immunoprotected, and attenuate adverse remodeling 4 weeks after MI.

Mesenchymal Stem Cell Therapy for Aging Frailty

Chronic diseases and degenerative conditions are strongly linked with the geriatric syndrome of frailty and account for a disproportionate percentage of the health care budget. Frailty increases the risk of falls, hospitalization, institutionalization, disability, and death. By definition, frailty syndrome is characterized by declines in lean body mass, strength, endurance, balance, gait speed, activity and energy levels, and organ physiologic reserve. Collectively, these changes lead to the loss of homeostasis and capability to withstand stressors and resulting vulnerabilities. There is a strong link between frailty, inflammation, and the impaired ability to repair tissue injury due to decreases in endogenous stem cell production. Although exercise and nutritional supplementation provide benefit to frail patients, there are currently no specific therapies for frailty. Bone marrow-derived allogeneic mesenchymal stem cells (MSCs) provide therapeutic benefits in heart failure patients irrespective of age. MSCs contribute to cellular repair and tissue regeneration through their multilineage differentiation capacity, immunomodulatory, and anti-inflammatory effects, homing and migratory capacity to injury sites, and stimulatory effect on endogenous tissue progenitors. The advantages of using MSCs as a therapeutic strategy include standardization of isolation and culture expansion techniques and safety in allogeneic transplantation. Based on this evidence, we performed a randomized, double-blinded, dose-finding study in elderly, frail individuals and showed that intravenously delivered allogeneic MSCs are safe and produce significant improvements in physical performance measures and inflammatory biomarkers. We thus propose that frailty can be treated and the link between frailty and chronic inflammation offers a potential therapeutic target, addressable by cell therapy.

Abstract 215: Induced Pluripotent Stem Cell-Derived Cardiomyocyte Proliferation is Enhanced by Co-culture With Female Mesenchymal Stem Cells

Background: Myocardial ischemia remains a leading cause of morbidity and mortality worldwide. Bone marrow-derived adult mesenchymal stem cells (MSCs) improve cardiac structure and function post-MI likely mediated in large part by paracrine factors. There is emerging evidence that female MSCs have greater therapeutic efficacy than male MSCs.

Objective: We hypothesized that female MSCs promote cardiomyocyte differentiation, proliferation and contractility of induced pluripotent stem cells (iPSCs) better than male MSCs.

Methods & Results: Human (h) iPSCs were co-cultured with male or female murine MSCs during or after differentiation into beating cardiomyocytes. Female MSCs were significantly more potent at stimulating ISL-1 and NKX2-5 expression in hiPSC-derived cardiac precursors and cardiomyocytes. Exosomes from female MSCs had lower levels of miR-17, a miR that directly represses Isl1 . hiPSCs co-cultured with female MSCs, exhibited a 2-fold greater increase in proliferation compared to male MSCs. In addition, ß 2 -adrenergic receptor expression was up regulated 3.5-fold in hiPSCs incubated with female MSCs compared to 2.5-fold for male MSCs.

Conclusion: Our findings illustrate that there are significant differences between female and male MSCs in their ability to affect cardiomyogenesis of hiPSCs and suggest that this effect is mediated, at least in part, by reduced levels of miR-17. The observation that female MSCs have greater potential to improve cardiomyocyte proliferation and contractility has important implications for stem cell therapy.

Abstract 342: The Absence of S-nitrosoglutathione Reductase (GSNOR -/- ) Reduces Maturation of iPSC-derived Cardiomyocytes

Introduction: Induced pluripotent stem cells (iPSCs) are a potential source of cardiac regenerative therapy. However, incomplete structural and functional maturation of iPSC-derived cardiomyocytes (iPSC-CMs), including lack of T-tubules, immature sarcoplasmic reticulum (SR), and inefficient Ca 2+ -induced Ca 2+ release remain major limitations. We assessed the influence of nitric oxide (NO) on differentiation and maturation of iPSC-CMs.

Objective: We hypothesized that enhanced S-nitrosylation impairs SR calcium (Ca 2+ ) handling (storage and uptake) in iPSC-CMs.

Methods: iPSCs were derived from fibroblasts from wildtype mice and mice lacking S-nitrosoglutathione reductase (GSNOR -/- ), a denitrosylase that regulates protein S-nitrosylation. iPSCs were differentiated into CMs from embryoid bodies via the hanging-drop method. Analyses of cell morphology and structural changes, gene expression (cardiac markers), and functional tests (intracellular calcium transients) were performed at an early stage of cardiac development (day 21 of cell culture). The involvement of the SR Ca 2+ ATPase (SERCA2) in iPSC-CM contraction was tested by blocking Ca 2+ re-uptake with 1 μM Thapsigargin and SR Ca 2+ stores were estimated by addition of 20 mM caffeine. The role of the cardiac ryanodine receptor (RyR2) was assessed by blocking the channel with 10 μM ryanodine. The dependence of Ca 2+ transients on L-type Ca 2+ channels (LTCC) was demonstrated using 10 μM nifedipine, which eliminated [Ca 2+ ] i transients and cell contraction. Length of sarcomeres within the contractile apparatus was determined by staining cells with α-actinin.

Results: Sarcomeres were more organized in WT iPSC-CMs than in GSNOR -/- iPSC-CMs after 21 days in culture. The loss of GSNOR activity reduced SR Ca 2+ content and sarcomere organization in iPSC-CMs. While iPSC-CMs are relatively immature in terms of ultrastructure and Ca 2+ handling; GSNOR –/– iPSC-CMs were less able to recycle intracellular Ca 2+ .

Conclusions: Our results provide novel insights into NO-mediated gene regulation and cell proliferation and suggest that the absence of GSNOR affects CM differentiation. These findings have important implications for regenerative medicine and provide new targets for iPSC-based therapy.

Mesenchymal Stem Cell-Based Therapy for Cardiovascular Disease: Progress and Challenges

Administration of mesenchymal stem cells (MSCs) to diseased hearts improves cardiac function and reduces scar size. These effects occur via the stimulation of endogenous repair mechanisms, including regulation of immune responses, tissue perfusion, inhibition of fibrosis, and proliferation of resident cardiac cells, although rare events of transdifferentiation into cardiomyocytes and vascular components are also described in animal models. While these improvements demonstrate the potential of stem cell therapy, the goal of full cardiac recovery has yet to be realized in either preclinical or clinical studies. To reach this goal, novel cell-based therapeutic approaches are needed. Ongoing studies include cell combinations, incorporation of MSCs into biomaterials, or pre-conditioning or genetic manipulation of MSCs to boost their release of paracrine factors, such as exosomes, growth factors, microRNAs, etc. All of these approaches can augment therapeutic efficacy. Further study of the optimal route of administration, the correct dose, the best cell population(s), and timing for treatment are parameters that still need to be addressed in order to achieve the goal of complete cardiac regeneration. Despite significant progress, many challenges remain.

Simulated Microgravity Impairs Cardiac Autonomic Neurogenesis from Neural Crest Cells

Microgravity-induced alterations in the autonomic nervous system (ANS) contribute to derangements in both the mechanical and electrophysiological function of the cardiovascular system, leading to severe symptoms in humans following space travel. Because the ANS forms embryonically from neural crest (NC) progenitors, we hypothesized that microgravity can impair NC-derived cardiac structures. Accordingly, we conducted in vitro simulated microgravity experiments employing NC genetic lineage tracing in mice with cKit^CreERT2/+, Isl1nLacZ, and Wnt1-Cre reporter alleles. Inducible fate mapping in adult mouse hearts and pluripotent stem cells (iPSCs) demonstrated reduced cKit^CreERT2/+-mediated labeling of both NC-derived cardiomyocytes and autonomic neurons (P < 0.0005 vs. controls). Whole transcriptome analysis, suggested that this effect was associated with repressed cardiac NC- and upregulated mesoderm-related gene expression profiles, coupled with abnormal bone morphogenetic protein (BMP)/transforming growth factor beta (TGF-β) and Wnt/β-catenin signaling. To separate the manifestations of simulated microgravity on NC versus mesodermal-cardiac derivatives, we conducted Isl1nLacZ lineage analyses, which indicated an approximately 3-fold expansion (P < 0.05) in mesoderm-derived Isl-1⁺ pacemaker sinoatrial nodal cells; and an approximately 3-fold reduction (P < 0.05) in cardiac NC-derived ANS cells, including sympathetic nerves and Isl-1⁺ cardiac ganglia. Finally, NC-specific fate mapping with a Wnt1-Cre reporter iPSC model of murine NC development confirmed that simulated microgravity directly impacted the in vitro development of cardiac NC progenitors and their contribution to the sympathetic and parasympathetic innervation of the iPSC-derived myocardium. Altogether, these findings reveal an important role for gravity in the development of NCs and their postnatal derivatives, and have important therapeutic implications for human space exploration, providing insights into cellular and molecular mechanisms of microgravity-induced cardiomyopathies/channelopathies.

Abstract 238: S-nitrosoglutathione Reductase (GSNOR) Plays a Critical Role in Placental Vascularization Working Through the VEGF-NO Pathway

Introduction: Preeclampsia (PE), a leading cause of maternal and fetal mortality and morbidity, is characterized by increased levels of reactive oxygen species (ROS) and S-nitrosylated protein, and decreased levels of the antioxidant, ascorbate (Asc), which is required for the release of nitric oxide (NO) from nitrosylated proteins. Mice lacking S-nitrosoglutathione reductase (GSNOR –/– ), a denitrosylase that regulates protein S-nitrosylation, exhibit a PE-like phenotype including maternal hypertension, cardiac concentric hypertrophy and impaired placental vascularization. We hypothesized that impaired placental vascularization, one of the primary causes of preeclampsia is mediated by alteration in S-nitrosylation of the VEGF-NO pathway, and ascorbate treatment rescues this pathologic phenotype.

Methods: Pregnant GSNOR –/– and control (WT) mice (n=5-7) were studied at late pregnancy (day 17.5). Ascorbate was provided in drinking water beginning at day 0.5. Fetoplacental capillary density was determined from isolectin staining and reactive nitrosative stress determined from nitrotyrosine staining in placental sections. S-nitrosylation of VEGF was determined using SNO-Rac and eNOS levels by Western blot analysis.

Results: Fetoplacental capillary density was reduced 19% in GSNOR –/– fetuses compared to WT (P<0.001). GSNOR –/– placentas exhibited higher nitrotyrosine staining than WT placentas, indicating the presence of nitrosative stress. These increases were associated with reduced level of eNOS protein (P<0.05) and decreased S-nitrosylation of VEGF (P<0.05) in the GSNOR –/– placentas as compared to WT. Ascorbate treatment decreased nitrotyrosine staining, and increased fetoplacental capillary density ~10% (P<0.001), eNOS protein levels (P<0.05) and S-nitrosylation of VEGF (P<0.05) in the GSNOR –/– placentas as compared to WT.

Conclusion: These findings suggest that GSNOR plays an essential role in promoting placental vascularization in part working through the VEGF-NO pathway. Ascorbate treatment rescued the nitrosative stress and improved placental vascularization, suggesting that it can be used therapeutically to treat or prevent preeclampsia.

Abstract 215: Allogeneic MSCs Improve Endothelial Function in Patients with Dilated Cardiomyopathy via an SDF-1α-mediated Mechanism and the Suppression of Pathologic Cytokines

Endothelial dysfunction is central to the pathophysiology of heart failure, including dilated cardiomyopathy (DCM). Current drug therapies are unable to halt the progression of DCM, compelling the emergence of novel stem cell therapy approaches. Mesenchymal stem cells (MSCs) are pro-angiogenic, immunomodulatory, antifibrotic, and stimulate endogenous endothelial progenitor (EPC) proliferation and function, thus having the potential to ameliorate endothelial dysfunction. We demonstrated that patients with DCM who received allogeneic MSCs had a significant improvement in endothelial function 3-months post treatment, whereas patients who received autologous MSCs had no improvement. Therefore, we hypothesized that allogeneic MSCs preferentially improve endothelial function via a mechanism involving the suppression of pathologic levels of vascular endothelial growth factor (VEGF), stromal derived factor-1 alpha (SDF-1α), and tumor necrosis factor alpha (TNFα). Accordingly, patient serum VEGF and TNFα were measured at baseline and 3 months post MSC treatment. In vitro, MSC secretion of SDF-1α and TNFα was also measured. Our results show that patients with DCM had elevated levels of VEGF (n=21, 581.2±812.2 pg/mL) and TNFα (n=15, 22±9.4 pg/mL) at baseline, and that only allogeneic MSCs were able to restore these levels toward normal (VEGF: n=10, Δ-267.1±252.1, P=0.01; TNFα: n=8, Δ-7.1±3.1 pg/mL, P=0.0005). While there was no difference in TNFα secretion by autologous or allogeneic MSCs (0.01±0.14 vs. 0.4±0.6 pg/mL), autologous MSCs secreted significantly higher levels of SDF-1α compared to allogeneic MSCs (n=12, 79.3±16.7 vs. 14.2±9.4 pg/mL, P=0.0001). In vitro secreted SDF-1α and serum VEGF and TNFα levels correlated with EPC bioactivity (ΔSDF-1α to ΔEPC-CFUs, R=-0.9, P<0.0001; ΔVEGF to ΔEPC-CFUs, R=-0.7, P=0.001; ΔTNFα to ΔEPC-CFUs, R=-0.6, P=0.01). These findings reveal a novel mechanism by which allogeneic MSCs secrete physiologic levels of SDF-1α resulting in physiologic levels of VEGF signaling, reduced TNFα, increased EPC bioactivity, and improved endothelial function. These findings have important clinical and biological implications for the use of MSCs in patients with DCM.

Abstract 33: Combination of Allogeneic Mesenchymal and Kidney-derived Stem Cells Promotes Kidney Repair in a Swine Model of Chronic Kidney Disease

Background: Chronic kidney disease (CKD) has a high prevalence (~14% of the population) and is associated with a significantly increased risk of cardiovascular disease and a 15-fold higher rate of mortality than the general population. Current therapies slow disease progression but do not repair organ damage, leading to end-stage renal disease. Stem cell therapy has the potential to promote repair via neovascularization and antifibrotic effects. We tested the renal reparative capacity of allogeneic mesenchymal stem cells (MSCs) and kidney ckit+ stem cells (c-kit) in an established swine model of CKD.

Methods: Yorkshires pigs (n=27) underwent 5/6 nephrectomy via renal artery embolization and 4-weeks later received either: MSC (10х10 6 ), c-kit (10х10 6 ), combination (MSC+c-kit; 1:1 ratio [5х10 6 each]), or placebo (each n=5). Allogeneic cell therapy was delivered via the patent renal artery of the remnant kidney. Kidney functional parameters and renal MRI were measured at baseline, and at 4- and 12-weeks (euthanasia) post-embolization.

Results: The CKD model was validated from baseline to 4 weeks by an increased creatinine: (Δ1.1 ± 0.15 mg/dl; p<0.0001), BUN (Δ13.50 ± 2.99mg/dl; p=0.0003), and urine protein/creatinine ratio (Δ0.311mg/g; p=0.018), and decreased GFR (Δ49.82 ±6.41 ml/min; p=0.0002). Mean arterial pressure (MAP) was not different between groups from baseline to 4 weeks. After 12 weeks, there was a significant difference in MAP between groups (p=0.04), with an increase in the placebo group (19.97± 8.65 mmHg, p=0.08). BUN and creatinine levels improved in all of the groups from 4-12 weeks. GFR also improved in all the groups, but with the greatest effect in the combination group (76± 23.83ml/min; p= 0.03) from 4-12 weeks. Urine protein/creatinine ratio did not change in placebo but decreased in cell treated groups. There was no evidence of immune rejection as evaluated in a complete body necropsy.

Conclusion: Allogeneic MSCs and kidney-derived stem cells are safe in a CKD swine model. The combination of stem cells was shown to be more efficacious in improving kidney function. These novel findings have important implications for the advancement of cell therapy for CKD.

Abstract 398: Growth Hormone Releasing Hormone Agonist (GHRH-A) Restores Cardiac Function in a Rodent Model of Heart FailureWith Preserved Ejection Fraction (HFpEF)

Background: Roughly half of patients with heart failure (HF) have preserved EF (HFpEF) and this rate is increasing. The pathophysiology of HFpEF is unclear and treatment of HFpEF remains a critical unmet need.

Hypothesis: Growth hormone releasing hormone agonist (GHRH-A) restores cardiac function in a rodent model of HFpEF.

Methods: C57BL/6N mice (n=4-5) received angiotensin-II (Ang-II: 0.8 mg/kg/day) via mini-osmotic pump for 4 weeks with concurrent daily administration of GHRH-A (MR-356: 200 μg/kg) or vehicle (DMSO+propylene-glycol). Echocardiography was assessed at baseline and 4 weeks after Alzet pump placement. Hemodynamic studies were performed and the titin N2BA/N2B ratio measured.

Results: Ang-II administration increased end-diastolic pressure (EDP, p=0.0186) with no changes in EF (p=ns) or end-systolic pressure (ESP, p=ns) in comparison to control mice. Isovolumetric relaxation time (IVRT, p<0.05) and end-diastolic pressure-volume relationship (EDPVR, p=0.0229) were significantly increased in the Ang-II/vehicle group, consistent with increased ventricular stiffness and impaired relaxation. Importantly, GHRH-A treatment reset these parameters to normal conditions (table). HFpEF mice exhibited higher HW/BW ratios and lung weight. The titin N2BA/N2B ratio, which was increased (p<0.05) in the Ang-II group, was restored by GHRH-A treatment.

Conclusion: Chronic administration of Ang-II mediates structural and functional changes that mimic HFpEF. GHRH-A treatment improves diastolic dysfunction and impaired relaxation. Therefore, GHRH-A therapy may be beneficial in the treatment of HFpEF.

Abstract 35: Transendocardial Mesenchymal Stem Cell Injection Demonstrates Reverse Remodeling Effects of Global LV Volumes and Enhanced Lateral Papillary Muscle Shortening

Rationale: Secondary mitral regurgitation (MR) carries a poor prognosis despite improvements in surgical and transcatheter interventions. Mesenchymal stem cell (MSC) therapy for heart disease reduces infarct size and left ventricle (LV) dilatation, reverses remodeling, and improves regional contractility and functional capacity. However, it is unknown if the benefits of MSC therapy on LV structure and function apply to lateral papillary muscle shortening, an important predictor of secondary MR severity.

Hypothesis: Test the hypothesis that administration of MSCs promotes interpapillary muscle distance (IPMD) shortening.

Methods/Results: This retrospective analysis draws on results from autologous or allogeneic MSC injection therapies in a Göttingen swine model of chronic ischemic cardiomyopathy (ICM). MRI was used to measure end-diastolic volume (EDV), end-systolic volume (ESV), diastolic/systolic IPMD, and IPMD shortening. NOGA mapping and angiographic tracings of left ventriculography allowed for assessment of the effect of injection localized to papillary muscles (defined as injection within cardiac segments 4, 6, 10 and 12 in the 16-segment model). Three months after stem cell injection, EDV increased in both placebo- (12.2±3.6 mL; p=0.002) and MSC- (10.2±2.6 mL; p=0.03) treated swine. ESV increased only in placebo- (7.1±2.2 mL; p=0.003) but not MSC- treated swine. Systolic IPMD was maintained with MSC therapy (1.20±0.74 mm; p=0.33) but increased in placebo (1.83±0.60 mm; p=0.01). Systolic IPMD was preserved whether MSC injection was localized to papillary muscle (0.53±0.49 mm; p=0.44) or not (0.22±0.40 mm; p=0.24). Notably, IPMD shortening was significantly greater in MSC- (8.1±5.6%; p=0.02) but not placebo-injected (4.7±5.0%; p=0.69) swine. There were no between group differences in IPMD shortening (p=0.08).

Conclusion: This study is the first to show that transendocardial MSC injections significantly enhanced IPMD shortening and lateral interpapillary muscle contraction in a model of chronic ICM. This effect was independent of injection site.

Abstract 441: Role of Nitric Oxide and S-nitrosylation in Cardiomyogenesis by iPSCs

Introduction: The mechanism by which signaling pathways, such as Wnt and BMP interact and modulate each other’s function is crucial to our understanding of cardiomyogenesis and cardiomyocyte proliferation. Nitric oxide (NO) is a signaling molecule that can trigger cardiac differentiation of stem cells, suggesting a cardiogenic function of NO synthase(s) (NOS).

Hypothesis: NO modulates transcription factor function during pluripotency and differentiation toward a cardiac phenotype.

Methods: Induced pluripotent stem cells (iPSCs) were derived from fibroblasts from wildtype mice and mice lacking S-nitrosoglutathione reductase (GSNOR -/- ), a denitrosylase that regulates protein S-nitrosylation. iPSCs were differentiated into functional cardiomyocytes from embryoid bodies (EBs) via the hanging-drop method.

Results: During differentiation into cardiomyocytes, GSNOR -/- iPSC-derived cardiomyocytes exhibited reduced expression of mesoderm induction-related ( Brachyury ), cardiac mesoderm (Kdr , Isl-1 ) and cardiac progenitor genes ( Nkx2.5 , GATA4 ). Axin-1, an inducer of apoptosis and negative regulator of the Wnt signaling pathway and MAPK pathways, specifically p38, were increased on EB-Day (D)4. In contrast, SMAD1/5/8, members of the BMP canonical signaling pathway, were reduced beginning on EB-D8. Increased p38 is associated with reduced GATA4 expression and differentiation of human ES cells into cardiomyocytes. Decreased SMAD1/5/8 is likely at least in part responsible for the reduced expression of Nkx2.5.

Conclusions: Our findings support that the absence of GSNOR modulates Wnt/β-catenin and BMP signaling pathways during cardiogenesis, resulting in reduced expression of mesoderm, cardiac mesoderm and cardiac progenitor genes. These findings are expected to have important implications for regenerative medicine and can provide new targets for iPS cell-based therapy.

Abstract 137: Ghrhr is a Cell-surface Marker of Human Pluripotent Stem Cell-derived Cardiomyogenic Precursors

Introduction: A major roadblock for generating human pluripotent stem cell (hPSCs) derivatives highly enriched in cardiomyogenic precursors (CPCs), has been the lack of CPC-specific cell surface markers.

Hypothesis: Based on observations that adult CPCs are responsive to growth hormone-releasing hormone (GHRH) signaling, we hypothesized that the GHRH receptor (GHRHR) is a specific cell-surface marker for hPSC-derived CPCs.

Methods: We performed temporal analysis of GHRHR expression in an in-vitro model of human cardiogenesis using induced hPSCs (hiPSCs) and SOX10::GFP embryonic hPSCs (hESCs) ; and mouse ( in-vivo ) cardiogenesis in wild-type (WT), MEF2c-AHF-Cre, Wnt1-Cre2 and cKit-CreERT2/+ reporter mice.

Results: Gene expression and confocal immunofluorescence analyses during chemically-defined, stage-specific, cardiac lineage differentiation indicated that GHRHR is not expressed in undifferentiated hiPSCs or during specification into primitive streak-like Brachyury + or Mesp1 + precardiac cells; but is induced in cardiogenic mesoderm-like cells, at the stage of commitment into NKX2.5 + and/or ISL1 + CPCs ( p =0.001) and persists in Troponin-T + cardiomyocytes. Similarly, experiments modeling cardiac neural crest (CNC) with SOX10::GFP hESCs indicated that GHRHR is not expressed by GFP + CNCs but is induced following differentiation into NKX2.5 + and/or ISL1 + derivatives. Importantly, stimulation with 1μm recombinant GHRH during days 5-7 of hiPSCs differentiation increased NKX2.5 expression 2.5-fold, an effect that was abolished by exposure to 1μM Somatostatin, a GHRH antagonist ( p =0.0009). Last, in vivo analyses in WT , MEF2c-AHF-Cre, Wnt1-Cre2 and cKit-CreERT2/+ reporter embryonic and postnatal hearts corroborated that GHRHR specifically marks NKX2.5 + mesoderm- and CNC-lineage descendants in vivo, whereas GHRHR is not expressed by Wnt1-Cre2 and cKit-CreERT2/+ CNCs descendants that are Nkx2.5 – .

Conclusions: Together these findings indicate that GHRHR is universally expressed by NKX2.5 + /ISL1 + CPCs and cardiomyocytes of both mesoderm and CNC origin. Therefore, GHRHR appears to be a valuable cell-surface marker for the selection and enrichment of CPCs from hPSCs for biomedical and regenerative medicine applications.

Abstract 397: Chronic Infusion of Growth Hormone Releasing Hormone Prevents Heart Failure with Preserved Ejection Fraction Phenotype Development in Murine Cardiomyocytes by Reducing Myofilament Sensitivity to Calcium

Introduction: Heart failure with preserved ejection fraction (HFpEF) represents ~50% of heart failure cases and is characterized by impaired relaxation, ventricular stiffening and fibrosis. Growth hormone releasing hormone agonists (GHRH-A) reduce fibrosis in rat and swine models of ischemic myocardial injury. However, their effect on failing cardiomyocytes (CMs) is unknown. We hypothesized that activation of GHRH receptor signaling targets proteins associated with excitation-contraction coupling, reduces affinity of myofilaments for Ca 2+ and prevents the development of HFpEF.

Methods: CD1 mice, implanted with mini-osmotic pump (Alzet) to deliver angiotensin-II (Ang-II) for 4 weeks, received daily injections of GHRH-A (MR-356; n=8) or vehicle (n=8). CMs were isolated and Ca 2+ and sarcomere length recorded. Expression and phosphorylation of Ca 2+ handling and sarcomeric proteins were assessed. Unmanipulated CD1 mice (n=7) acted as normal controls.

Results: Ang-II-treated CMs exhibited reduced sarcomere length consistent with shorter cell length, indicating an inability to completely relax. These CMs also exhibited impaired contractility that correlated with reduced myosin binding protein C (cMyBPC) expression with no changes in phosphorylation. Response of [Ca 2+ ] transient amplitude to increasing pacing rate was depressed and Ca 2+ decay was delayed and associated with lower expression of SERCA2 and NCX1, increased SR Ca 2+ leak but no change in phospholamban phosphorylation (p-PLB) at Ser16. Slower sarcomere re-lengthening and reduced phospho-cTnI (p-cTnI) at Ser 23/24 were observed in HFpEF CMs. MR-356 treatment maintained resting sarcomere length as well as sarcomere shortening at control values, and completely abrogated Ang-II-induced delay in Ca 2+ decay and sarcomere relaxation. SR Ca 2+ leak was reduced. p-PLB was further enhanced by MR-356, and cMyBPC and p-cTnI were maintained at control levels.

Conclusion: Our findings demonstrate that chronic administration of Ang-II mediates functional changes in CMs consistent with HFpEF and suggest that activation of the GHRH receptor signaling pathways desensitizes myofilaments and prevents HFpEF-associated alterations in Ca 2+ handling and dysfunctional CM relaxation.

Pim1 Kinase Overexpression Enhances ckit+ Cardiac Stem Cell Cardiac Repair Following Myocardial Infarction in Swine

BACKGROUND

Pim1 kinase plays an important role in cell division, survival, and commitment of precursor cells towards a myocardial lineage, and overexpression of Pim1 in ckit⁺ cardiac stem cells (CSCs) enhances their cardioreparative properties.

OBJECTIVES

The authors sought to validate the effect of Pim1-modified CSCs in a translationally relevant large animal preclinical model of myocardial infarction (MI).

METHODS

Human cardiac stem cells (hCSCs, n = 10), hckit⁺ CSCs overexpressing Pim1 (Pim1⁺; n = 9), or placebo (n = 10) were delivered by intramyocardial injection to immunosuppressed Yorkshire swine (n = 29) 2 weeks after MI. Cardiac magnetic resonance and pressure volume loops were obtained before and after cell administration.

RESULTS

Whereas both hCSCs reduced MI size compared to placebo, Pim1⁺ cells produced a ∼3-fold greater decrease in scar mass at 8 weeks post-injection compared to hCSCs (-29.2 ± 2.7% vs. -8.4 ± 0.7%; p < 0.003). Pim1⁺ hCSCs also produced a 2-fold increase of viable mass compared to hCSCs at 8 weeks (113.7 ± 7.2% vs. 65.6 ± 6.8%; p <0.003), and a greater increase in regional contractility in both infarct and border zones (both p < 0.05). Both CSC types significantly increased ejection fraction at 4 weeks but this was only sustained in the Pim1⁺ group at 8 weeks compared to placebo. Both hCSC and Pim1⁺ hCSC treatment reduced afterload (p = 0.02 and p = 0.004, respectively). Mechanoenergetic recoupling was significantly greater in the Pim1⁺ hCSC group (p = 0.005).

CONCLUSIONS

Pim1 overexpression enhanced the effect of intramyocardial delivery of CSCs to infarcted porcine hearts. These findings provide a rationale for genetic modification of stem cells and consequent translation to clinical trials.

GSNOR Deficiency Enhances In Situ Skeletal Muscle Strength, Fatigue Resistance, and RyR1 S-Nitrosylation Without Impacting Mitochondrial Content and Activity

AIM

Nitric oxide (NO) plays important, but incompletely defined roles in skeletal muscle. NO exerts its regulatory effects partly though S-nitrosylation, which is balanced by denitrosylation by enzymes such as S-nitrosoglutathione reductase (GSNOR), whose functions in skeletal muscle remain to be fully deciphered.

RESULTS

GSNOR null (GSNOR^-/-) tibialis anterior (TA) muscles showed normal growth and were stronger and more fatigue resistant than controls in situ. However, GSNOR^-/- lumbrical muscles showed normal contractility and Ca²⁺ handling in vitro, suggesting important differences in GSNOR function between muscles or between in vitro and in situ environments. GSNOR^-/- TA muscles exhibited normal mitochondrial content, and capillary densities, but reduced type IIA fiber content. GSNOR inhibition did not impact mitochondrial respiratory complex I, III, or IV activities. These findings argue that enhanced GSNOR^-/- TA contractility is not driven by changes in mitochondrial content or activity, fiber type, or blood vessel density. However, loss of GSNOR led to RyR1 hypernitrosylation, which is believed to increase muscle force output under physiological conditions. cGMP synthesis by soluble guanylate cyclase (sGC) was decreased in resting GSNOR^-/- muscle and was more responsive to agonist (DETANO, BAY 41, and BAY 58) stimulation, suggesting that GSNOR modulates cGMP production in skeletal muscle.

INNOVATION

GSNOR may act as a "brake" on skeletal muscle contractile performance under physiological conditions by modulating nitrosylation/denitrosylation balance.

CONCLUSIONS

GSNOR may play important roles in skeletal muscle contractility, RyR1 S-nitrosylation, fiber type specification, and sGC activity. Antioxid. Redox Signal. 26, 165-181.

Route of Delivery Modulates the Efficacy of Mesenchymal Stem Cell Therapy for Myocardial Infarction: A Meta-Analysis of Preclinical Studies and Clinical Trials

RATIONALE

Accumulating data support a therapeutic role for mesenchymal stem cell (MSC) therapy; however, there is no consensus on the optimal route of delivery.

OBJECTIVE

We tested the hypothesis that the route of MSC delivery influences the reduction in infarct size and improvement in left ventricular ejection fraction (LVEF).

METHODS AND RESULTS

We performed a meta-analysis investigating the effect of MSC therapy in acute myocardial infarction (AMI) and chronic ischemic cardiomyopathy preclinical studies (58 studies; n=1165 mouse, rat, swine) which revealed a reduction in infarct size and improvement of LVEF in all animal models. Route of delivery was analyzed in AMI swine studies and clinical trials (6 clinical trials; n=334 patients). In AMI swine studies, transendocardial stem cell injection reduced infarct size (n=49, 9.4% reduction; 95% confidence interval, -15.9 to -3.0), whereas direct intramyocardial injection, intravenous infusion, and intracoronary infusion indicated no improvement. Similarly, transendocardial stem cell injection improved LVEF (n=65, 9.1% increase; 95% confidence interval, 3.7 to 14.5), as did direct intramyocardial injection and intravenous infusion, whereas intracoronary infusion demonstrated no improvement. In humans, changes of LVEF paralleled these results, with transendocardial stem cell injection improving LVEF (n=46, 7.0% increase; 95% confidence interval, 2.7 to 11.3), as did intravenous infusion, but again intracoronary infusion demonstrating no improvement.

CONCLUSIONS

MSC therapy improves cardiac function in animal models of both AMI and chronic ischemic cardiomyopathy. The route of delivery seems to play a role in modulating the efficacy of MSC therapy in AMI swine studies and clinical trials, suggesting the superiority of transendocardial stem cell injection because of its reduction in infarct size and improvement of LVEF, which has important implications for the design of future studies.

Stimulatory Effects of Mesenchymal Stem Cells on cKit+ Cardiac Stem Cells Are Mediated by SDF1/CXCR4 and SCF/cKit Signaling Pathways

RATIONALE

Culture-expanded cells originating from cardiac tissue that express the cell surface receptor cKit are undergoing clinical testing as a cell source for heart failure and congenital heart disease. Although accumulating data support that mesenchymal stem cells (MSCs) enhance the efficacy of cardiac cKit(+) cells (CSCs), the underlying mechanism for this synergistic effect remains incompletely understood.

OBJECTIVE

To test the hypothesis that MSCs stimulate endogenous CSCs to proliferate, migrate, and differentiate via the SDF1/CXCR4 and stem cell factor/cKit pathways.

METHODS AND RESULTS

Using genetic lineage-tracing approaches, we show that in the postnatal murine heart, cKit(+) cells proliferate, migrate, and form cardiomyocytes, but not endothelial cells. CSCs exhibit marked chemotactic and proliferative responses when cocultured with MSCs but not with cardiac stromal cells. Antagonism of the CXCR4 pathway with AMD3100 (an SDF1/CXCR4 antagonist) inhibited MSC-induced CSC chemotaxis but stimulated CSC cardiomyogenesis (P<0.0001). Furthermore, MSCs enhanced CSC proliferation via the stem cell factor/cKit and SDF1/CXCR4 pathways (P<0.0001).

CONCLUSIONS

Together these findings show that MSCs exhibit profound, yet differential, effects on CSC migration, proliferation, and differentiation and suggest a mechanism underlying the improved cardiac regeneration associated with combination therapy using CSCs and MSCs. These findings have important therapeutic implications for cell-based therapy strategies that use mixtures of CSCs and MSCs.

Abstract 56: Growth Hormone Releasing Hormone Improves Sarcomere Relaxation and Calcium Decline in Cardiomyocyte From a Mouse Model of Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is characterized by impaired relaxation, ventricular stiffening and fibrosis. Growth hormone releasing hormone (GHRH) agonists reduce fibrosis in rat and swine models of ischemic myocardial injury. However, their effect on cardiomyocytes is not known. We hypothesized that activation of GHRH receptor signaling improves impaired cardiomyocyte relaxation in a mouse model of HFpEF. C57BL6N mice (n=4-5) were implanted with a mini-osmotic pump to deliver angiotensin-II (Ang-II: 0.8 mg/kg/day) for 4 weeks and received daily injections of GHRH-Agonist (GHRH-A [MR-409]: 100 μg/kg) or vehicle (DMSO+propylene-glycol). Cardiomyocytes were isolated and calcium and sarcomere shortening assessed. Ang-II-treated cardiomyocytes exhibited reduced sarcomere length, indicating an inability to completely relax, despite lower resting calcium. These cardiomyocytes also exhibited impaired ability to contract with no changes in calcium transient amplitude, deficient relaxation and delayed calcium decay. MR-409 treatment restored resting calcium and resting sarcomere length; improved sarcomere shortening and completely abrogated Ang-II-induced delay in calcium decline and relaxation (see figure 1). Our findings demonstrate that chronic administration of Ang-II mediates structural and functional changes consistent with HFpEF and suggest that activation of the GHRH receptor signaling pathways prevents HFpEF-associated cardiomyocyte performance alterations.

Abstract 323: Loss of Gravity Impairs Cardiac Neural Crest Cell Lineage Development and Function

Introduction: A multitude of structural, haemodynamic and electromechanical cardiovascular disorders have been observed in humans following space-travel. These abnormalities are thought to emerge from transient alterations in autonomic nervous system (ANS). However, since the ANS is cardiac neural crest (CNC)-derived, whether microgravity-induced cardiomyopathies reflect CNC dysfunction, is unknown.

Hypothesis: Impairment of CNCs underlies microgravity-induced cardiomyopathies.

Methods: Myocardial explants from adult cKit CreERT2/+ ;IRG mice (n=5/group), as well as cKit CreERT2/+ ;IRG- derived (iPSC Kit-Cre ; n=6/group) and Wnt1-Cre;tdTomato -derived (iPSC Wnt1-Cre ; n=18/group) induced pluripotent stem cells, were cultured under static (SC) or simulated microgravity conditions (rotary cell-culture system; RCCS).

Results: CNC lineage-tracing in cardiac explants illustrated that, compared to SC, RCCS abolished the pool of cKit + CNCs in adult hearts, indicated by quantitation of cKit CreERT2 - mediated EGFP expression ( p <0.05). Cardiogenesis modeling experiments with iPSC Kit-Cre yielded fewer beating EBs ( p =0.0005), and ~10-fold reduction in EGFP + cardiomyocytes ( p =0.01), in RCCS vs . SC. Microarray analyses suggested that RCCS-mediated alterations in BMP and Wnt/β-catenin pathways, downregulated ANS and CNC-related gene programs, and enhanced vasculogenic differentiation without affecting the expression of cardiac mesoderm-related genes. Differences were verified by quantitative PCR. Modeling CNC development in iPSC Wnt1-Cre further confirmed an RCCS-mediated dramatic impairment in development and function of CNCs, indicated by quantitation of tdTomato expression in day-10 and day-21 beating embryoid bodies ( p <0.0001). Intriguingly, the effect of RCCS in CNCs could be only partially rescued upon transfer to SC.

Conclusions: Together these data indicate that microgravity negatively regulates the development and function of CNCs, thus partly explaining the cellular and molecular mechanisms of microgravity-induced cardiomyopathies. Moreover, these findings are expected to have important implications in space exploration, since they suggest an essential role for gravity in vertebrate development.

Abstract 74: Cardioprotective Effect of Growth Hormone Releasing Hormone in Mouse Model of Heart Failure with Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is characterized by impaired relaxation, ventricular stiffening and fibrosis. We previously showed that activation of GHRH receptor markedly reduces fibrosis in rat and swine models of ischemic myocardial injury. Therefore, we hypothesized that activation of GHRH receptor signaling can improve diastolic dysfunction in a mouse model of HFpEF.

C57BL6N mice (n=4-5) were implanted with a mini-osmotic pump to deliver angiotensin-II (Ang-II: 0.8 mg/kg/day) for 4 weeks and randomly assigned to receive daily injections of GHRH-Agonist (GHRH-A [MR-409]: 100 μg/kg) or vehicle (DMSO+propylene-glycol). Cardiac performance was assessed by serial echocardiography and hemodynamic analysis.

Chronic administration of Ang-II resulted in increased end-diastolic pressure (EDP, p=0.0186) with no changes in EF (p=ns) or end-systolic pressure (ESP, p=ns) in comparison to control mice. Isovolumetric relaxation time (IVRT, p<0.05) and end-diastolic pressure-volume relationship (EDPVR, p=0.0229) were markedly increased in the Ang-II group consistent with increased ventricular stiffness and poor myocardial relaxation. MR-409 treatment reset these parameters to normal levels (table 1).

Our findings demonstrate that chronic administration of Ang-II mediates structural and functional changes that mimic HFpEF. Importantly, MR-409 treatment reduces Ang-II-induced elevation of EDP, EDPVR and IVRT; thus preventing HFpEF–like effects, suggesting that activation of the GHRH receptor signaling pathways represents a potential new therapeutic approach for HFpEF.

Abstract 66: Ascorbate Prevents Hypertension, Proteinuria and Concentric Hypertrophy by Balancing the Nitroso-redox System in a Model of Preeclampsia, the S-nitrosoglutathione Reductase (gsnor) Deficient Mice

Introduction: Preeclampsia (PE), a leading cause of maternal and fetal mortality and morbidity, is characterized by increased levels of reactive oxygen species (ROS) and S-nitrosylated protein, and decreased levels of the antioxidant, ascorbate (Asc). Mice lacking S-nitrosoglutathione reductase (GSNOR –/– ), a denitrosylase that regulates protein S-nitrosylation, exhibit a PE-like phenotype including maternal hypertension, proteinuria, cardiac concentric hypertrophy and impaired placental vascularization. We hypothesize that the PE-like phenotype is mediated by nitroso-redox imbalance and nitrosative stress and can be rescued with ascorbate treatment.

Methods: Pregnant GSNOR –/– and control (WT) mice (n=5-7) were provided drinking water ± Asc beginning at day 0.5 of gestation (E0.5). We determined blood pressure using a Millar catheter, relative wall thickness (RWT) by echocardiography, and placental vascularization by isolectin staining. Cardiomyocytes (CM) were isolated at late stage pregnancy (E17.5) and fluorescent dyes used to determine levels of ROS (2’7’-dichlorofluorescein), nitric oxide (NO, diaminofluorescin) and peroxynitrite (dihydrorhodamine 123).

Results: Isolated CMs from pregnant GSNOR –/– hearts, exhibited elevated levels of ROS (2.48±0.39 vs. 1.58±0.18 ΔF/F 0 ), free NO (6.65±0.43 vs. 5.59±0.26 ΔF/F 0 ) and peroxynitrite (0.75±0.04 vs. 0.39±0.03 ΔF/F 0 ) compared to WT. These increases were prevented with Asc treatment (P<0.01), which completely rescued the PE phenotype in GSNOR –/– mothers, including hypertension (105±2 mmHg vs. 95± mmHg in Asc-treated, P<0.05), proteinuria (P<0.05) and RWT (0.56±0.04 vs. 0.45±0.03 in Asc-treated (P<0.05). Placental vascularization was also significantly improved with Asc treatment in GSNOR –/– mothers. Asc had no significant effect in WT mice.

Conclusion: Our findings indicate that nitroso-redox imbalance and nitrosative stress contributes to PE in mice. Asc treatment balanced the nitroso-redox system and rescued the pathological phenotypes in GSNOR –/– mice, suggesting that it can be used therapeutically to treat or prevent preeclampsia.

Synergistic Effects of Combined Cell Therapy for Chronic Ischemic Cardiomyopathy

BACKGROUND

Both bone marrow-derived mesenchymal stem cells (MSCs) and c-kit(+) cardiac stem cells (CSCs) improve left ventricular remodeling in porcine models and clinical trials. Using xenogeneic (human) cells in immunosuppressed animals with acute ischemic heart disease, we previously showed that these 2 cell types act synergistically.

OBJECTIVES

To more accurately model clinical applications for heart failure, this study tested whether the combination of autologous MSCs and CSCs produce greater improvement in cardiac performance than MSCs alone in a nonimmunosuppressed porcine model of chronic ischemic cardiomyopathy.

METHODS

Three months after ischemia/reperfusion injury, Göttingen swine received transendocardial injections with MSCs alone (n = 6) or in combination with cardiac-derived CSCs (n = 8), or placebo (vehicle; n = 6). Cardiac functional and anatomic parameters were assessed using cardiac magnetic resonance at baseline and before and after therapy.

RESULTS

Both groups of cell-treated animals exhibited significantly reduced scar size (MSCs -44.1 ± 6.8%; CSC/MSC -37.2 ± 5.4%; placebo -12.9 ± 4.2%; p < 0.0001), increased viable tissue, and improved wall motion relative to placebo 3 months post-injection. Ejection fraction (EF) improved (MSCs 2.9 ± 1.6 EF units; CSC/MSC 6.9 ± 2.8 EF units; placebo 2.5 ± 1.6 EF units; p = 0.0009), as did stroke volume, cardiac output, and diastolic strain only in the combination-treated animals, which also exhibited increased cardiomyocyte mitotic activity.

CONCLUSIONS

These findings illustrate that interactions between MSCs and CSCs enhance cardiac performance more than MSCs alone, establish the safety of autologous cell combination strategies, and support the development of second-generation cell therapeutic products.