Cell therapy for human ischemic heart diseases: critical review and summary of the clinical experiences.

A decade ago, stem or progenitor cells held the promise of tissue regeneration in human myocardium, with the expectation that these therapies could rescue ischemic myocyte damage, enhance vascular density and rebuild injured myocardium. The accumulated evidence in 2014 indicates, however, that the therapeutic success of these cells is modest and the tissue regeneration involves much more complex processes than cell-related biologics. As the quest for the ideal cell or combination of cells continues, alternative cell types, such as resident cardiac cells, adipose-derived or phenotypic modified stem or progenitor cells have also been applied, with the objective of increasing both the number and the retention of the reparative cells in the myocardium. Two main delivery routes (intracoronary and percutaneous intramyocardial) of stem cells are currently used preferably for patients with recent acute myocardial infarction or ischemic cardiomyopathy. Other delivery modes, such as surgical or intravenous via peripheral veins or coronary sinus have also been utilized with less success. Due to the difficult recruitment of patients within conceivable timeframe into cardiac regenerative trials, meta-analyses of human cardiac cell-based studies have tried to gather sufficient number of subjects to present a statistical compelling statement, reporting modest success with a mean increase of 0.9-6.1% in left ventricular global ejection fraction. Additionally, nearly half of the long-term studies reported the disappearance of the initial benefit of this treatment. Beside further extensive efforts to increase the efficacy of currently available methods, pre-clinical experiments using new techniques such as tissue engineering or exploiting paracrine effect hold promise to regenerate injured human cardiac tissue.

Role of adult bone marrow stem cells in the repair of ischemic myocardium: current state of the art.

OBJECTIVE: To review the milestones in stem cell therapy for ischemic heart disease from early basic science to large clinical studies and new therapeutic approaches. MATERIALS AND METHODS: Basic research and clinical trials (systematic review) were used. The heart has the ability to regenerate through activation of resident cardiac stem cells or through recruitment of a stem cell population from other tissues, such as bone marrow. Although the underlying mechanism is yet to be made clear, numerous studies in animals have documented that transplantation of bone marrow-derived stem cells or circulating progenitor cells following acute myocardial infarction and ischemic cardiomyopathy is associated with a reduction in infarct scar size and improvements in left ventricular function and myocardial perfusion. RESULTS: Cell-based cardiac therapy has expanded considerably in recent years and is on its way to becoming an established cardiovascular therapy for patients with ischemic heart disease. There have been recent insights into the understanding of mechanisms involved in the mobilization and homing of the imported cells, as well as into the paracrine effect, growth factors, and bioactive molecules. Additional information has been obtained regarding new stem cell sources, cell-based gene therapy, cell-enhancement strategies, and tissue engineering, all of which should enhance the efficacy of human cardiac stem cell therapy. CONCLUSIONS: The recently published trials using bone marrow-origin stem cells in cardiac repair reported a modest but significant benefit from this therapy. Further clinical research should aim to optimize the cell types utilized and their delivery mode, and pinpoint optimal time of cell transplantation.

Matrix Metalloproteinase-2 Impairs Homing of Intracoronary Delivered Mesenchymal Stem Cells in a Porcine Reperfused Myocardial Infarction: Comparison With Intramyocardial Cell Delivery.

BACKGROUND: Intracoronary (IC) injection of mesenchymal stem cells (MSCs) results in a prompt decrease of absolute myocardial blood flow (AMF) with late and incomplete recovery of myocardial tissue perfusion. Here, we investigated the effect of decreased AMF on oxidative stress marker matrix metalloproteinase-2 (MMP-2) and its influence on the fate and homing and paracrine character of MSCs after IC or intramyocardial cell delivery in a closed-chest reperfused myocardial infarction (MI) model in pigs. METHODS: Porcine MSCs were transiently transfected with Ad-Luc and Ad-green fluorescent protein (GFP). One week after MI, the GFP-Luc-MSCs were injected either IC (group IC, 11.00 ± 1.07 × 106) or intramyocardially (group IM, 9.88 ± 1.44 × 106). AMF was measured before, immediately after, and 24 h post GFP-Luc-MSC delivery. In vitro bioluminescence signal was used to identify tissue samples containing GFP-Luc-MSCs. Myocardial tissue MMP-2 and CXCR4 receptor expression (index of homing signal) were measured in bioluminescence positive and negative infarcted and border, and non-ischemic myocardial areas 1-day post cell transfer. At 7-day follow-up, myocardial homing (cadherin, CXCR4, and stromal derived factor-1alpha) and angiogenic [fibroblast growth factor 2 (FGF2) and VEGF] were quantified by ELISA of homogenized myocardial tissues from the bioluminescence positive and negative infarcted and border, and non-ischemic myocardium. Biodistribution of the implanted cells was quantified by using Luciferase assay and confirmed by fluorescence immunochemistry. Global left ventricular ejection fraction (LVEF) was measured at baseline and 1-month post cell therapy using magnet resonance image. RESULTS: AMF decreased immediately after IC cell delivery, while no change in tissue perfusion was found in the IM group (42.6 ± 11.7 vs. 56.9 ± 16.7 ml/min, p = 0.018). IC delivery led to a significant increase in myocardial MMP-2 64 kD expression (448 ± 88 vs. 315 ± 54 intensity × mm2, p = 0.021), and decreased expression of CXCR4 (592 ± 50 vs. 714 ± 54 pg/tissue/ml, p = 0.006), with significant exponential decay between MMP-2 and CXCR4 (r = 0.679, p < 0.001). FGF2 and VEGF of the bioluminescence infarcted and border zone of homogenized tissues were significantly elevated in the IM goups as compared to IC group. LVEF increase was significantly higher in IM group (0.8 ± 8.4 vs 5.3 ± 5.2%, p = 0.046) at the 1-month follow up. CONCLUSION: Intracoronary stem cell delivery decreased AMF, with consequent increase in myocardial expression of MMP-2 and reduced CXCR4 expression with lower level of myocardial homing and angiogenic factor release as compared to IM cell delivery.

Design and rationale for the Myocardial Stem Cell Administration After Acute Myocardial Infarction (MYSTAR) Study: a multicenter, prospective, randomized, single-blind trial comparing early and late intracoronary or combined (percutaneous intramyocardial and intracoronary) administration of nonselected autologous bone marrow cells to patients after acute myocardial infarction.

BACKGROUND: Previous data suggest that bone marrow-derived stem cells (BM-SCs) decrease the infarct size and beneficially affect the postinfarction remodeling. METHODS: The Myocardial Stem Cell Administration After Acute Myocardial Infarction Study is a multicenter, prospective, randomized, single-blind clinical trial designed to compare the early and late intracoronary or combined (percutaneous intramyocardial and intracoronary) administration of BM-SCs to patients after acute myocardial infarction (AMI) with reopened infarct-related artery. The primary end points are the changes in resting myocardial perfusion defect size and left ventricular ejection fraction (gated single photon emission computed tomography [SPECT] scintigraphy) 3 months after BM-SCs therapy. The secondary end points relate to evaluation of (1) the safety and feasibility of the application modes, (2) the changes in left ventricular wall motion score index (transthoracic echocardiography), (3) myocardial voltage and segmental wall motion (NOGA mapping), (4) left ventricular end-diastolic and end-systolic volumes (contrast ventriculography), and (5) the clinical symptoms (Canadian Cardiovascular Society [CCS] anina score and New York Heart Association [NYHA] functional class) at follow-up. Three hundred sixty patients are randomly assigned into 1 of 4 groups: group A, early treatment (21-42 days after AMI) with intracoronary injection; group B, early treatment with combined application; group C, late treatment (3 months after AMI) with intracoronary delivery; and group D, late treatment with combined administration of BM-SCs. Besides the BM-SCs therapy, the standardized treatment of AMI is applied in all patients. CONCLUSIONS: The Myocardial Stem Cell Administration After Acute Myocardial Infarction Trial is the first randomized trial to investigate the effects of the combined (intramyocardial and intracoronary) and the intracoronary mode of delivery of BM-SCs therapy in the early and late periods after AMI.

Long-Term Outcome of Combined (Percutaneous Intramyocardial and Intracoronary) Application of Autologous Bone Marrow Mononuclear Cells Post Myocardial Infarction: The 5-Year MYSTAR Study.

OBJECTIVE: The long-term (5-year) outcome of early (3-6 weeks after acute myocardial infarction [AMI], BM-MNC Early group) and late (3-4 months after AMI, BM-MNC Late group) combined (percutaneous intramyocardial and intracoronary) delivery of autologous bone marrow mononuclear cells (BM-MNCs) was evaluated in patients with ejection fractions (EF) between 30-45% post-AMI. METHODS: Major adverse cardiac and cerebrovascular events (MACCE) and hospitalization were recorded. Left (LV) and right (RV) ventricular function were measured by transthoracic echocardiography. Cardiac magnetic resonance imaging (MRI) and myocardial single photon emission computed tomography was performed in a subgroup of patients. Pre-cell therapy myocardial voltage values of treated areas (assessed by NOGA mapping) were correlated with clinical outcome. RESULTS: Five-year MACCE incidences (7.4%. vs 24.1%) and the composite of all adverse events (11.1% vs 27.6%) were not different between the Early and Late treatment groups. The significant LV-EF increase at 1-year follow-up was preserved at the 5-year control (from baseline to 5-year: 5.3%, 95% CI:0.5-10.1, and 5.7%, 95% CI:1.7-9.6, p<0.05 in the Early and Late groups, respectively), with no significant changes between 1- and 5-year follow-ups. Similarly, RVEF increased significantly from baseline to the 5-year follow-up (Early group: 5.4%, 95% CI:1.0-9.6; and Late group: 8.4%, 95% CI:4.5-12.3). Lower baseline levels of myocardial viability of the treated cardiac area (6.3±2.4 vs 8.2±3.0 mV, p<0.05) were associated with incidence of MACCE. CONCLUSIONS: Percutaneous combined delivery of autologous BM-MNCs is feasible and safe after 5 years, and may result in sustained improvement of cardiac function at 5 years in patients with low EF post-AMI (Clinicaltrials.gov NCT01395212).

Delayed recovery of myocardial blood flow after intracoronary stem cell administration.

The aim of the present study was to investigate the changes in absolute myocardial blood flow (AMF) after intracoronary injections of mesenchymal SC (MSC) and compared to controls in closed-chest reperfused acute myocardial infarction (AMI) in pigs. Male MSCs, transiently transfected with Luciferase (Luc-MSC) were delivered (9.7 ± 1.2 x 10(6)) intracoronary in the open infarct-related artery one-week post-AMI in female pigs (group MSC), while saline was injected with the same injection rate in controls (group C). The AMF was measured immediately after, and 3, 12 and 24 h post-intracoronary Luc-MSC or saline injections. In vitro bioluminescence images and quantitative real-time TaqMan PCR measurements were performed to quantify the sex-mismatched MSCs. No difference between the groups was observed regarding the weight, heart rate, blood pressure and global ejection fraction 1-week post-AMI. The baseline AMF were similar in the groups (61.3 ± 15. vs 61.1 ± 12.0 ml/min). AMF was decreased significantly immediately after intracoronary MSC delivery (42.0 ± 12.4 vs 57.7 ± 15.7 ml/min p = 0.013), and remained low at 3 h (40.9 ± 13.4 vs 55.8 ± 4.9 ml/min, p = 0.004), 12 h (43.0 ± 3.7 vs 57.8 ± 5.4 ml/min, p = 0.001) with incomplete recovery at 24 h (47.2 ± 5.5 vs 62.1 ± 14.1 ml/min, p = 0.038) as compared to controls, respectively. In vitro bioluminescence displayed transfected Luc-MSCs along the proximal and mid part of the LAD, with limited number (295 ± 101 sry copied/million cardiac cells) of Y-chromosome-MSCs in the infarcted area. Intracoronary injection of SCs results in immediate decrease of AMF, with delayed recovery. The delivery of the SC into the injured myocardium might be hindered by the altered coronary pressure and flow conditions.

Effect of intramyocardial delivery of autologous bone marrow mononuclear stem cells on the regional myocardial perfusion. NOGA-guided subanalysis of the MYSTAR prospective randomised study.

The aim of the sub-study of the MYSTAR randomised trial was to analyse the changes in myocardial perfusion in NOGA-defined regions of interest (ROI) with intramyocardial injections of autologous bone marrow mononuclear cells (BM-MNC) using an elaborated transformation algorithm. Patients with recent first acute myocardial infarction (AMI) and left ventricular (LV) ejection fraction (EF) between 30-45% received BM-MNC by intramyocardial followed by intracoronary injection 68 +/- 34 days post-AMI (pooled data of MYSTAR). NOGA-guided endocardial mapping and 99m-Sestamibi-SPECT (single photon emission computer tomography) were performed at baseline and at three months follow-up (FUP). ROI was delineated as a best polygon by connecting of injection points of NOGA polar maps. ROIs were projected onto baseline and FUP polar maps of SPECT calculating the perfusion severity of ROI. Infarct size was decreased (from 27.2 +/- 10.7% to 24.1 +/- 11.5%, p<0.001), and global EF increased (from 38 +/- 6.1% to 41.5 +/- 8.4%, p<0.001) three months after BM-MNC delivery. Analysis of ROI resulted in a significant increase in unipolar voltage (index of myocardial viability) (from 7.9 +/- 3.0 mV to 9.9 +/- 2.7 mV at FUP, p<0.001) and local linear shortening (index of local wall motion disturbances) (from 11.0 +/- 3.9% to 12.7 +/- 3.4%, p=0.01). NOGA-guided analysis of the intramyocardially treated area revealed a significantly increased tracer uptake both at rest (from 56.7 +/- 16.1% to 62.9 +/- 14.2%, p=0.003) and at stress (from 59.3 +/- 14.2% to 62.3 +/- 14.9%, p=0.01). Patients exhibiting >or=5% improvement in perfusion defect severity received a significantly higher number of intramyocardial BM-MNC. In conclusion, combined cardiac BM-MNC delivery induces significant improvement in myocardial viability and perfusion in the intramyocardially injected area.

Hypoxia-inducible factor 1-alpha release after intracoronary versus intramyocardial stem cell therapy in myocardial infarction.

We have investigated the effect of stem cell delivery on the release of hypoxia-inducible factor 1 alpha (HIF-1alpha) in peripheral circulation and myocardium in experimental myocardial ischemia. Closed-chest, reperfused myocardial infarction (MI) was created in domestic pigs. Porcine mesenchymal stem cells (MSCs) were cultured and delivered (9.8 +/- 1.2 x 10(6)) either percutaneously NOGA-guided transendocardially (Group IM) or intracoronary (Group IC) 22 +/- 4 days post-MI. Pigs without MSC delivery served as sham control (Group S). Plasma HIF-1alpha was measured at baseline, immediately post- and at follow-up (FUP; 2 h or 24 h) post-MSC delivery by ELISA kit. Myocardial HIF-1alpha expression of infarcted, normal myocardium, or border zone was determined by Western blot. Plasma level of HIF-1alpha increased immediately post-MI (from 278 +/- 127 to 631 +/- 375 pg/ml, p < 0.05). Cardiac delivery of MSCs elevated the plasma levels of HIF-1alpha significantly (p < 0.05) in groups IC and IM immediately post-MSC delivery, and returned to baseline level at FUP, without difference between the groups IC and IM. The myocardial tissue HIF-1alpha expression in the infarcted area was higher in Group IM than in Group IC or S (1,963 +/- 586 vs. 1,307 +/- 392 vs. 271 +/- 110 activity per square millimeter, respectively, p < 0.05), while the border zone contained similarly lower level of HIF-1alpha, but still significantly higher as compared with Group S. Trend towards increase in myocardial expression of HIF-1alpha was measured in Group IM at 24 h, in contrast to Group IC. In conclusion, both stem cell delivery modes increase the systemic and myocardial level of HIF-1alpha. Intramyocardial delivery of MSC seems to trigger the release of angiogenic HIF-1alpha more effectively than does intracoronary delivery.

Combined delivery approach of bone marrow mononuclear stem cells early and late after myocardial infarction: the MYSTAR prospective, randomized study.

BACKGROUND: Combined intracoronary and intramyocardial administration might improve outcomes for bone-marrow-derived stem cell therapy for acute myocardial infarction (AMI). We compared the safety and feasibility of early and late delivery of stem cells with combined therapy approaches. METHODS: Patients with left ventricular ejection fraction less than 45% after AMI were randomly assigned stem cell delivery via intramyocardial injection and intracoronary infusion 3-6 weeks or 3-4 months after AMI. Primary end points were changes in infarct size and left ventricular ejection fraction 3 months after therapy. RESULTS: A total of 60 patients were treated. The mean changes in infarct size at 3 months were -3.5 +/- 5.1% (95% CI -5.5% to -1.5%, P = 0.001) in the early group and -3.9 +/- 5.6% (95% CI -6.1% to -1.6%, P = 0.002) in the late group, and changes in ejection fraction were 3.5 +/- 5.6% (95% CI 1.3-5.6%, P = 0.003) and 3.4 +/- 7.0% (95% CI 0.7-6.1%, P = 0.017), respectively. At 9-12 months after AMI, ejection fraction remained significantly higher than at baseline in both groups. In the early and late groups, a mean of 200.3 +/- 68.7 x 10(6) and 194.8 +/- 60.4 x 10(6) stem cells, respectively, were delivered to the myocardium, and 1.30 +/- 0.68 x 10(9) and 1.29 +/- 0.41 x 10(9) cells, respectively, were delivered into the artery. A high number of cells was required for significant improvements in the primary end points. CONCLUSIONS: Combined cardiac stem cell delivery induces a moderate but significant improvement in myocardial infarct size and left ventricular function.