A Combination of Allogeneic Stem Cells Promotes Cardiac Regeneration.

BACKGROUND: The combination of autologous mesenchymal stem cells (MSCs) and cardiac stem cells (CSCs) synergistically reduces scar size and improves cardiac function in ischemic cardiomyopathy. Whereas allogeneic (allo-)MSCs are immunoevasive, the capacity of CSCs to similarly elude the immune system remains controversial, potentially limiting the success of allogeneic cell combination therapy (ACCT). OBJECTIVES: This study sought to test the hypothesis that ACCT synergistically promotes cardiac regeneration without provoking immunologic reactions. METHODS: Göttingen swine with experimental ischemic cardiomyopathy were randomized to receive transendocardial injections of allo-MSCs + allo-CSCs (ACCT: 200 million MSCs/1 million CSCs, n = 7), 200 million allo-MSCs (n = 8), 1 million allo-CSCs (n = 4), or placebo (Plasma-Lyte A, n = 6). Swine were assessed by cardiac magnetic resonance imaging and pressure volume catheterization. Immune response was tested by histologic analyses. RESULTS: Both ACCT and allo-MSCs reduced scar size by -11.1 ± 4.8% (p = 0.012) and -9.5 ± 4.8% (p = 0.047), respectively. Only ACCT, but not MSCs or CSCs, prevented ongoing negative remodeling by offsetting increases in chamber volumes. Importantly, ACCT exerted the greatest effect on systolic function, improving the end-systolic pressure-volume relation (+0.98 ± 0.41 mm Hg/ml; p = 0.016). The ACCT group had more phospho-histone H3+ (a marker of mitosis) cardiomyocytes (p = 0.04), and noncardiomyocytes (p = 0.0002) than did the placebo group in some regions of the heart. Inflammatory sites in ACCT and MSC-treated swine contained immunotolerant CD3+/CD25+/FoxP3+ regulatory T cells (p < 0.0001). Histologic analysis showed absent to low-grade inflammatory infiltrates without cardiomyocyte necrosis. CONCLUSIONS: ACCT demonstrates synergistic effects to enhance cardiac regeneration and left ventricular functional recovery in a swine model of chronic ischemic cardiomyopathy without adverse immunologic reaction. Clinical translation to humans is warranted.

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.

Rebuilding the Damaged Heart: Mesenchymal Stem Cells, Cell-Based Therapy, and Engineered Heart Tissue.

Mesenchymal stem cells (MSCs) are broadly distributed cells that retain postnatal capacity for self-renewal and multilineage differentiation. MSCs evade immune detection, secrete an array of anti-inflammatory and anti-fibrotic mediators, and very importantly activate resident precursors. These properties form the basis for the strategy of clinical application of cell-based therapeutics for inflammatory and fibrotic conditions. In cardiovascular medicine, administration of autologous or allogeneic MSCs in patients with ischemic and nonischemic cardiomyopathy holds significant promise. Numerous preclinical studies of ischemic and nonischemic cardiomyopathy employing MSC-based therapy have demonstrated that the properties of reducing fibrosis, stimulating angiogenesis, and cardiomyogenesis have led to improvements in the structure and function of remodeled ventricles. Further attempts have been made to augment MSCs' effects through genetic modification and cell preconditioning. Progression of MSC therapy to early clinical trials has supported their role in improving cardiac structure and function, functional capacity, and patient quality of life. Emerging data have supported larger clinical trials that have been either completed or are currently underway. Mechanistically, MSC therapy is thought to benefit the heart by stimulating innate anti-fibrotic and regenerative responses. The mechanisms of action involve paracrine signaling, cell-cell interactions, and fusion with resident cells. Trans-differentiation of MSCs to bona fide cardiomyocytes and coronary vessels is also thought to occur, although at a nonphysiological level. Recently, MSC-based tissue engineering for cardiovascular disease has been examined with quite encouraging results. This review discusses MSCs from their basic biological characteristics to their role as a promising therapeutic strategy for clinical cardiovascular disease.

Rationale and design of the allogeneiC human mesenchymal stem cells (hMSC) in patients with aging fRAilTy via intravenoUS delivery (CRATUS) study: A phase I/II, randomized, blinded and placebo controlled trial to evaluate the safety and potential efficacy of allogeneic human mesenchymal stem cell infusion in patients with aging frailty.

Frailty is a syndrome associated with reduced physiological reserves that increases an individual's vulnerability for developing increased morbidity and/or mortality. While most clinical trials have focused on exercise, nutrition, pharmacologic agents, or a multifactorial approach for the prevention and attenuation of frailty, none have studied the use of cell-based therapies. We hypothesize that the application of allogeneic human mesenchymal stem cells (allo-hMSCs) as a therapeutic agent for individuals with frailty is safe and efficacious. The CRATUS trial comprises an initial non-blinded phase I study, followed by a blinded, randomized phase I/II study (with an optional follow-up phase) that will address the safety and pre-specified beneficial effects in patients with the aging frailty syndrome. In the initial phase I protocol, allo-hMSCs will be administered in escalating doses via peripheral intravenous infusion (n=15) to patients allocated to three treatment groups: Group 1 (n=5, 20 million allo-hMSCs), Group 2 (n=5, 100 million allo-hMSCs), and Group 3 (n=5, 200 million allo-hMSCs). Subsequently, in the randomized phase, allo-hMSCs or matched placebo will be administered to patients (n=30) randomly allocated in a 1:1:1 ratio to one of two doses of MSCs versus placebo: Group A (n=10, 100 million allo-hMSCs), Group B (n=10, 200 million allo-hMSCs), and Group C (n=10, placebo). Primary and secondary objectives are, respectively, to demonstrate the safety and efficacy of allo-hMSCs administered in frail older individuals. This study will determine the safety of intravenous infusion of stem cells and compare phenotypic outcomes in patients with aging frailty.

Concise Review: Review and Perspective of Cell Dosage and Routes of Administration From Preclinical and Clinical Studies of Stem Cell Therapy for Heart Disease.

An important stage in the development of any new therapeutic agent is establishment of the optimal dosage and route of administration. This can be particularly challenging when the treatment is a biologic agent that might exert its therapeutic effects via complex or poorly understood mechanisms. Multiple preclinical and clinical studies have shown paradoxical results, with inconsistent findings regarding the relationship between the cell dose and clinical benefit. Such phenomena can, at least in part, be attributed to variations in cell dosing or concentration and the route of administration (ROA). Although clinical trials of cell-based therapy for cardiovascular disease began more than a decade ago, specification of the optimal dosage and ROA has not been established. The present review summarizes what has been learned regarding the optimal cell dosage and ROA from preclinical and clinical studies of stem cell therapy for heart disease and offers a perspective on future directions. Significance: Preclinical and clinical studies on cell-based therapy for cardiovascular disease have shown inconsistent results, in part because of variations in study-specific dosages and/or routes of administration (ROA). Future preclinical studies and smaller clinical trials implementing cell-dose and ROA comparisons are warranted before proceeding to pivotal trials.

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.

Growth hormone-releasing hormone agonists reduce myocardial infarct scar in swine with subacute ischemic cardiomyopathy.

BACKGROUND: Growth hormone-releasing hormone agonists (GHRH-As) stimulate cardiac repair following myocardial infarction (MI) in rats through the activation of the GHRH signaling pathway within the heart. We tested the hypothesis that the administration of GHRH-As prevents ventricular remodeling in a swine subacute MI model. METHODS AND RESULTS: Twelve female Yorkshire swine (25 to 30 kg) underwent transient occlusion of the left anterior descending coronary artery (MI). Two weeks post MI, swine were randomized to receive injections of either 30 µg/kg GHRH-A (MR-409) (GHRH-A group; n=6) or vehicle (placebo group; n=6). Cardiac magnetic resonance imaging and pressure-volume loops were obtained at multiple time points. Infarct, border, and remote (noninfarcted) zones were assessed for GHRH receptor by immunohistochemistry. Four weeks of GHRH-A treatment resulted in reduced scar mass (GHRH-A: -21.9 ± 6.42%; P=0.02; placebo: 10.9 ± 5.88%; P=0.25; 2-way ANOVA; P=0.003), and scar size (percentage of left ventricular mass) (GHRH-A: -38.38 ± 4.63; P=0.0002; placebo: -14.56 ± 6.92; P=0.16; 2-way ANOVA; P=0.02). This was accompanied by improved diastolic strain. Unlike in rats, this reduced infarct size in swine was not accompanied by improved cardiac function as measured by serial hemodynamic pressure-volume analysis. GHRH receptors were abundant in cardiac tissue, with a greater density in the border zone of the GHRH-A group compared with the placebo group. CONCLUSIONS: Daily subcutaneous administration of GHRH-A is feasible and safe in a large animal model of subacute ischemic cardiomyopathy. Furthermore, GHRH-A therapy significantly reduced infarct size and improved diastolic strain, suggesting a local activation of the GHRH pathway leading to the reparative process.

Local delivery of mitoxantrone for the treatment of malignant brain tumors in rats.

OBJECT: Mitoxantrone is a drug with potent in vitro activity against malignant brain tumor cell lines; however, its effectiveness as a systemic agent has been hampered by poor central nervous system penetration and dose-limiting myelosuppression. To avoid these problems, we incorporated mitoxantrone into biodegradable polymeric wafers to be used for intracranial implantation, a strategy that has been shown to be safe and successful in the treatment of malignant gliomas. The authors investigated the release kinetics, toxicity, distribution, and efficacy of mitoxantrone delivered from intracranially implanted biodegradable wafers in the treatment of 9L gliosarcoma in Fischer 344 rats. METHODS: Mitoxantrone released from the biodegradable wafer matrix reached therapeutic drug concentrations in the brain for at least 35 days. Only animals with implanted wafers of the highest drug loading dose (20% mitoxantrone by weight) showed signs of significant toxicity. In three separate efficacy experiments, animals treated with mitoxantrone-loaded biodegradable wafers had significantly improved survival compared with control animals. The combined median survival for each treatment group was the following: 0% mitoxantrone wafers, 19 days; 1%, 30 days, p < 0.0001; 5%, 34 days, p < 0.0001; and 10%, 50 days, p < 0.0001. CONCLUSIONS: These findings establish that mitoxantrone delivered from intracranially implanted biodegradable wafers is effective in the treatment of malignant gliomas in rodents and should be considered for future clinical application in humans.