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

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. 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. 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

Abstract 128: Pim1 kinase Overexpression Enhances ckit+ Cardiac Stem Cells Cardioreparative Ability After Intramyocardial Delivery

Background: Pim-1 kinase plays an important role in cell division, survival and commitment towards myocardial lineage. We hypothesized that Pim-1 overexpression in ckit+ cardiac stem cell (CSCs) enhances cardioreparative effects. Methods: Immunosuppressed Yorkshire swine (n=31) received human ckit+ CSCs (n=9), Pim1 modified human ckit+ CSCs (n=9) or PBS (n=13) two weeks after myocardial infarction. Cardiac MRI and PV loops were obtained before and after cell administration. Results: At 8 weeks post transplantation, scar mass (Fig. 1A), viable tissue (Fig. 1B), ejection fraction (Fig. 1C) and stroke work (Fig. 1D) was significantly improved in Pim-1 modified ckit+ CSC compared to control ckit+, while both cell groups showed partial recovery compared to placebo (two way ANOVA, p<0.05). Both cell types similarly reduced preload (end diastolic pressure; Fig. 1E) and afterload (Arterial elastance; Fig 1F) compared to placebo, while only administration of Pim-1 CPCs improved regional contractility at both the infarct (Fig. 1G) and border zones (Fig. 1H). Collectively, mechanoenergetic recoupling was superior in the Pim-1 group compared to ckit+ controls (Cardiac Efficiency; Fig. 1I). Conclusions: Cardioreparative potential of CSCs delivered by intramyocardial injection to infarcted porcine hearts is significantly enhanced by overexpress Pim1, supporting translational development of Pim-1 as a validated genetic modification of CSCs for incorporation into clinical trials

Abstract 214: Reduction of Scar Tissue after GHRH-A Treatment in a Swine Model of Sub-acute Ischemic Cardiomyopathy

Background: Growth hormone-releasing hormone receptor agonists (GHRH-A) stimulate cardiac repair following myocardial infarction (MI) through the activation of the GHRH signaling pathway within the heart. We tested the hypothesis that the administration of GHRH-A prevents ventricular remodeling in a swine sub-acute MI model. Methods: Twelve female Yorkshire swine (25-30 Kg) underwent transient occlusion of the LAD 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 MRI, pressure volume loops and measures of endothelial function were obtained at multiple time points. Infarct-, border- and remote- (non-infarcted) zones were assessed by immunohistochemistry for the growth hormone-releasing hormone receptor (GHRHR). Results: Four-weeks of GHRH-A treatment resulted in reduced scar mass (GHRH-A group: –21.9±6.42%; p=0.02; placebo group: 10.9±5.88%; p=0.25; Two-way ANOVA; p=0.003), and reduced scar size (percent of left ventricle mass) (GHRH-A group: –38.38±4.63; p=0.0002; placebo group: –14.56± 6.92; p=0.16; Two-way ANOVA; p=0.02). Moreover, peripheral endothelial function was significantly increased compared to baseline values in the GHRH-A group (paired t-test; p=0.006) but not in the placebo group (p=0.99). 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 to the placebo group. These data support the concept of direct post-infarction activation of cardiac signal transduction, and of enhancing this activation with systemic treatment by GHRH. Conclusions: Daily subcutaneous administration of GHRH-A is feasible and safe in female swine. Furthermore, GHRH-A therapy significantly reduced infarct size and increased endothelial function, suggesting that a local activation of the GHRH pathway leads to the regenerative process and preservation of peripheral endothelial function

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

Abstract 140: Effect of Transendocardial Autologous Cardiac Stem Cells and Bone Marrow Mesenchymal Stem Cells to Reduce Infarct Size and Restore Cardiac Function in a Heart Failure Swine Model

Background: A cell combination of human mesenchymal stem cells (MSCs) and c-kit+ cardiac stem cells (CSCs) improves left ventricular (LV) performance to a greater degree than MSCs alone in post myocardial infarction swine. To advance the development of cell combination therapy, we administered autologous swine cells, and tested the hypothesis that transendocardial autologous CSCs/MSCs produces greater improvement of performance than MSCs in a rigorous model of heart failure due to post infarct LV remodeling. Methods: Gottingen mini-swine (n=28) underwent LAD coronary artery occlusion followed by reperfusion, and allowed to undergo LV remodeling for 90 days. Autologous MSCs were amplified from bone marrow and CSCs from right ventricular biopsies in each swine, and injections of either CSC/MSC combo (1M/200M, n=7), MSCs (200M, n=7), or placebo (Plasmalyte, n=6) were injected to the infarct-border zone via the NOGA system. Cardiac MRI and pressure volume loops were obtained before and after therapy. Results: Both cell groups had substantially reduced scar size (Combo –37.2.9± 5.4% vs MSCs –38.8±7.5% vs placebo −7.2±6.3, P=0.0001) and increased viable tissue (Combo +30.9±7% vs MSCs +41.8±10.5% vs placebo +7.7±4.5, P<0.0001) relative to placebo. Ejection Fraction (EF) improved only in the Combo group (Combo +7.0±2.8 vs MSCs +3.4±1.3 vs placebo +1.2±1.6 EF units, P=0.04). Accompanying this EF restoration was a substantial improvement in the Combo group in stroke volume (Combo +47.2±11.1% vs MSCs +32.6±12.0% vs placebo +10.8±4.5, P<0.0001), cardiac output (Combo +35.9±7.6% vs MSCs 41.9±26.5% vs placebo −16.4±6.6%, P=0.01) and diastolic strain rate (Combo +18.9±8.6% vs MSCs 14.0±8.8% vs placebo −14.9±9.5%, P=0.03). Conclusions: Combination cell therapy and MSCs alone dramatically reduce scar size in a swine model of chronic ischemic cardiomyopathy. In contrast, combination therapy has much greater impact on functional recovery, increasing EF to [near normal] levels. These findings illustrate that interactions between ckit+ CSCs and MSCs result in substantial enhancement in cardiac performance, establish the safety of autologous cell combination strategies, and support the development of an advanced second generation cell therapeutic product

Growth hormone-releasing hormone agonists ameliorate chronic kidney disease-induced heart failure with preserved ejection fraction

Therapies for heart failure with preserved ejection fraction (HFpEF) are lacking. Growth hormone-releasing hormone agonists (GHRH-As) have salutary effects in ischemic and nonischemic heart failure animal models. Accordingly, we hypothesized that GHRH-A treatment ameliorates chronic kidney disease (CKD)-induced HFpEF in a large-animal model. Female Yorkshire pigs ( = 16) underwent 5/6 nephrectomy via renal artery embolization and 12 wk later were randomized to receive daily subcutaneous injections of GHRH-A (MR-409; = 8; 30 µg/kg) or placebo ( = 8) for 4 to 6 wk. Renal and cardiac structure and function were serially assessed postembolization. Animals with 5/6 nephrectomy exhibited CKD (elevated blood urea nitrogen [BUN] and creatinine) and faithfully recapitulated the hemodynamic features of HFpEF. HFpEF was demonstrated at 12 wk by maintenance of ejection fraction associated with increased left ventricular mass, relative wall thickness, end-diastolic pressure (EDP), end-diastolic pressure/end-diastolic volume (EDP/EDV) ratio, and tau, the time constant of isovolumic diastolic relaxation. After 4 to 6 wk of treatment, the GHRH-A group exhibited normalization of EDP ( = 0.03), reduced EDP/EDV ratio ( = 0.018), and a reduction in myocardial pro-brain natriuretic peptide protein abundance. GHRH-A increased cardiomyocyte [Ca ] transient amplitude ( = 0.009). Improvement of the diastolic function was also evidenced by increased abundance of titin isoforms and their ratio ( = 0.0022). GHRH-A exerted a beneficial effect on diastolic function in a CKD large-animal model as demonstrated by improving hemodynamic, structural, and molecular characteristics of HFpEF. These findings have important therapeutic implications for the HFpEF syndrome

Transendocardial Mesenchymal Stem Cells and Mononuclear Bone Marrow Cells for Ischemic Cardiomyopathy

IMPORTANCE: Whether culture expanded mesenchymal stem cells or whole bone marrow mononuclear cells are safe and effective in chronic ischemic cardiomyopathy (ICM) remains controversial. OBJECTIVE: To demonstrate the safety of transendocardial stem cell injection with autologous mesenchymal stem cells (MSCs) and whole bone marrow mononuclear cells (BMCs) in patients with ischemic cardiomyopathy. DESIGN, SETTING AND PATIENTS: A phase 1 and 2 randomized blinded placebo-controlled study involving 65 patients with ischemic cardiomyopathy and left ventricular (LV) ejection fraction less than50%(September 1, 2009-July 12, 2013). The study compared injection of MSCs (N=19) and placebo (N=11) or BMCs (N=19) with placebo (N=10) with 1-year of follow up. INTERVENTIONS: Injections into 10 LV sites with an infusion catheter. MAIN OUTCOMES AND MEASURES: Treatment-emergent 30 day serious adverse event rate defined as composite of death, myocardial infarction, stroke, hospitalization for worsening heart failure, perforation, tamponade or sustained ventricular arrhythmias. RESULTS: No patient had a treatment-emergent serious adverse events at day 30. The 1-year incidence of serious adverse events was 31.6% (95% CI, 12.6%-56.6%) for MSCs, 31.6% (95% CI, 12.6%-56.6%) for BMCs, and 38.1% (95% CI, 18.1%-61.6%) for placebo. Over 1-year the Minnesota Living with Heart Failure (MLHF) score improved with MSCs (repeated measures ANOVA P= .02) and BMCs (P= .005) but not placebo (P= .38), and 6-minute walk distance increased with MSCs only (repeated measures model P= .03). Infarct size as a percentage of LV Mass was reduced by MSCs (-18.9%; 95% CI, -30.4 to -7.4; within-group P= .004) but not by BMCs (-7.0%; 95% CI, -15.7%-1.7%; within-group P= .11) or placebo (-5.2; 95% CI, -16.8%-6.5%; within-group P=.36). Regional myocardial function as peak Eulerian circumferential strain at the site of injection improved with MSCs (-4.9; 95% CI, -13.3-3.5; within-group repeated measures P=.03) but not BMCs (-2.1; 95% CI -5.5-1.3; P=.21) or placebo (-0.03; 95% CI, -1.9-1.9; P=.14). Left ventricular chamber volume and ejection fraction did not change. CONCLUSIONS AND RELEVANCE: Transendocardial stem cell injection with MSCs or BMCs appeared to be safe for patients with chronic ischemic cardiomyopathy and LV dysfunction. Although the sample size and multiple comparisons preclude a definitive statement about safety and clinical effect, these results provide the basis for larger studies to provide definitive evidence about safety and to assess efficacy of this new therapeutic approach