Rayyan Hemetsberger

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 × 106 and 194.8 ± 60.4 × 106 stem cells, respectively, were delivered to the myocardium, and 1.30 ± 0.68 × 109 and 1.29 ± 0.41 × 109 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.

Optimization of drug-eluting balloon use for safety and efficacy: Evaluation of the 2nd generation paclitaxel-eluting DIOR-balloon in porcine coronary arteries

Objectives: The aim of this preclinical study was to optimize the use of drug‐eluting balloon (DEB) DIOR2nd generation by measurements of tissue and plasma paclitaxel concentrations in porcine coronary artery overstretch and prove efficacy in inhibition of neointimal growth without complementary use of stent. Background: The usually recommended DEB 60 sec inflation time causes prolonged ischemia and arterial injury. Methods: Tissue, plasma, and balloon surface concentrations of paclitaxel were measured in pigs 45 min and 12 hr after balloon inflation times of 15, 20, 30, 45, and 60 sec. Extent of neointimal hyperplasia was compared using DIOR2nd generation or noncoated balloon at two‐week follow‐up. Paclitaxel was replaced by fluorescent paclitaxel derivative in DEB and DES to demonstrate the distribution of the drug in arterial wall. Results: DIOR2nd generation DEB provided 29 ± 3 μM/L, 52 ± 6 μM/L, 196 ± 44 μM/L, 202 ± 36 μM/L, and 184 ± 59 μM/L paclitaxel to the vessel wall after 15, 20, 30, 45, and 60 sec of dilation, reaching plateau at 30 sec inflation time. Paclitaxel penetrated up to 2 mm tissue deepness. Measurable plasma paclitaxel level (45 ± 28 ng/mL) was found only after 60 sec balloon inflation time. At follow‐up, the dilated arterial segment neointimal area and maximal neointimal thickness were significantly smaller with DIOR vs. uncoated balloon use. Fluorescence images of DIOR showed a homogenous distribution of the drug on the vessel, in contrast with DES. Conclusion: Using the DIOR2nd generation DEB, a maximal balloon inflation time of 30–45 sec is optimal, reducing effectively the neointimal hyperplasia.

Attainment of local drug delivery with paclitaxel-eluting balloon in porcine coronary arteries.

ObjectiveOur purpose was to confirm the local drug delivery of a paclitaxel-eluting balloon by percutaneous intervention of single arterial segments or bifurcations of porcine coronary arteries. MethodsEight domestic pigs were subjected to 2×30 s Dior balloon dilatation of the mid left anterior descending, left circumflex and proximal right coronary arteries. Bifurcation intervention was performed in six arteries. The dilated, and the distal and proximal reference segments were prepared for tissue paclitaxel concentration measurement. Tissue samples were harvested at mean 1.5, 12, 24 and 48 h after balloon dilatation and plasma samples were taken at various time points. ResultsThe tissue paclitaxel concentration of the single dilated segment was at 1.5 h postdilatation 1.82±1.60 μmol/l, which decreased significantly to 0.73±0.27 (P=0.032), 0.62±0.34 and 0.44±0.31 μmol/l at 12, 24 and 48 h. The bifurcation intervention resulted in 5.10±1.80 μmol/l tissue paclitaxel amount in the main branch, which at 12 h had diminished to 1.41±1.23 μmol/l (P=0.004). The bifurcation side contained 7.00±4.80 μmol/l paclitaxel at 1.5 h postdilatation, which lowered to 2.72±0.40 μmol/l (P=0.034). The mean paclitaxel concentration of the reference segments decreased gradually from 0.84±0.99 to 0.34±0.36 μmol/l (P=0.09), 0.28±0.16 and 0.19±0.18 μmol/l tissue at 1.5, 12, 24 and 48 h postdilatation, respectively. No paclitaxel was found in the peripheral blood at any time point. ConclusionShort exposure of the coronary artery to paclitaxel with a coated balloon is sufficient for the attainment of an adequate tissue concentration of paclitaxel, which is known to be efficient in inhibiting neointimal growth.

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.

Differential effect of ischaemic preconditioning on mobilisation and recruitment of haematopoietic and mesenchymal stem cells in porcine myocardial ischaemia-reperfusion

Effects of ischaemic preconditioning (IP) on the mobilisation and recruitment of haematopoietic (HSCs) and mesenchymal stem (MSC) cells were determined in porcine coronary occlusion/reperfusion. Thirty-three pigs underwent percutaneous occlusion of the left anterior descending coronary artery (LAD) for 90 minutes (min), followed by 120 min reperfusion. IP was performed in 16 of the 33 pigs by two cycles of 5 min balloon occlusion/reperfusion prior to the 90 min occlusion (group IP vs. group C). Peripheral blood and myocardial tissue concentration of bone marrow origin HSCs (characterised by coexpression of CD31+, CD90+, CD45+) and MSCs (characterised by coexpression of CD44+, CD90+, CD45-) were measured by flow cytometry in the early phase of IP. Plasma/serum levels of stem cell mobilisation factors (stromal cell-derived factor-1a [SDF-1a], vascular endothelial growth factor [VEGF], tumour necrosis factor a[TNF-a] and interleukin-8 [IL-8]) were measured. IP led to a significant increase in circulating HSCs as compared with the group C (475 +/- 233 vs. 281 +/- 264 /ml, p=0.032) in the early phase of IP. In contrast, a rapid and prolonged decrease in level of circulating MSCs was observed in group IP as compared with group C (19 +/- 12 vs. 32 +/- 17 /ml, p=0.015). The recruitment of HSCs and MSCs in infarct and border zone was significantly greater in IP group, indicating a faster homing of MSCs as compared with the rate of mobilisation. Rapid increase in VEGF, TNF-a and IL-8 levels was induced by IP, which, however, was not correlated with the levels of circulating SCs. In conclusion, IP resulted in differential mobilisation and recruitment of HSCs and MSCs in the early phase of cardioprotection.

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.

Tracking the migration of cardially delivered therapeutic stem cells in vivo: state of the art

Cell-based therapy is a promising, novel therapeutic strategy for cardiovascular disease. The rapid transition of this approach from the benchside to clinical trials has left a gap in the understanding of the mechanisms of cell therapy. Monitoring of cell homing and the fate of cardially delivered stem cells is fundamental for clarification of the myocardial regenerative process. Noninvasive imaging techniques allow an in vivo evaluation of the survival, migration and differentiation of implanted stem cells over time, and by this means, can help to answer unresolved questions. The most promising in vivo tracking methods involve the direct, nonspecific labeling of cells including MRI, radionuclide imaging and the use of reporter-gene imaging. This review summarizes the most important results of animal and human studies in which the fate and biodistribution of cardially delivered stem cells are assessed through different in vivo tracking methods.

Protective effect of ischaemic preconditioning on ischaemia/reperfusion-induced microvascular obstruction determined by on-line measurements of coronary pressure and blood flow in pigs

We investigated the protective effect of ischaemic preconditioning (IP) on the maintenance of coronary patency using on-line measurements of coronary pressures and blood flow in a closed-chest reperfused acute myocardial infarction (MI) model in pigs. Catheter-based 90-min occlusion followed by 60-min reperfusion of the left anterior descending coronary artery (LAD) was performed in anesthetised pigs (MI group). IP was applied (IP group) through two cycles of 5-min occlusion and 5-min reperfusion of the LAD before MI induction. Coronary patency was determined by measurements of coronary wedge pressure, collateral fractional flow reserve (FFRcoll), collateral pressure index (CPI) and absolute coronary blood flow (CBF). Inducible and constitutive nitric oxide synthase (iNOS/cNOS) activities and expressions were determined in the myocardium. Plasma levels of myeloperoxidase (MPO, index of activated leukocytes) and mean platelet volume (MPV, index of activated platelets) were measured. IP resulted in significantly lower levels of MPO (0.52 ± 0.19 vs. 1.05 ± 0.24 U/l, p<0.001) and MPV (9.1 ± 0.6 vs. 9.6 ± 1.0 fl, p=0.04), higher FFRcoll (0.17 ± 0.05 vs. 0.04 ± 0.05, p<0.001), CPI (0.13 ± 0.05 vs. 0.02 ± 0.05, p<0.001) and CBF (70.7 ± 4.2 vs. 50.8 ± 4.8 m/min, p<0.001) post-reperfusion as compared with the MI group. IP resulted in significantly higher cNOS activity and eNOS expression. Significant negative correlation was found between MPO and measures of coronary patency (FFRcoll, CPI and CBF) and cNOS activity. Moreover, cNOS activity correlated significantly with FFRcoll, CPI and CBF. In conclusion, IP attenuates the release of MPO and platelet activation, thereby contributing to the maintenance of vessel patency at microvascular level after reperfusion of the infarct-related artery.

Imaging the migration of therapeutically delivered cardiac stem cells.

the initial results of human clinical studies demonstrated the safety and potential benefit of autologous bone marrow cells in improving left ventricular function after acute myocardial infarction (AMI). However, a fundamental problem in developing stem cell (SC)–based therapies has been the

Implantation of paclitaxel-eluting stent impairs the vascular compliance of arteries in porcine coronary stenting model.

BACKGROUND The impaired compliance of large and medium-sized muscular arteries has been shown to correlate with the risk of adverse cardiovascular events. We assessed coronary artery distensibility using simultaneous intracoronary ultrasound and pressure wire measurements in porcine coronary arteries after implantation of paclitaxel-eluting (PES) and bare metal stents (BMS) and compared this with the histopathology of the arterial wall injury. METHODS PES and BMS were implanted into porcine left coronary arteries under general anesthesia. At 1-month follow-up (FUP) the endothelium-dependent and endothelium-independent vascular compliances were measured after intracoronary infusion of 10(-6)M acetylcholine for 2.5min, and intracoronary bolus of 100microg nitroglycerine, respectively. The arterial stiffness index, distensibility and reflexion index were calculated in stented arteries (n=25 PES and n=25 BMS), and correlated with histopathologic and histomorphometric changes of the vessel wall. RESULTS In spite of smaller neointimal area, the fibrin deposition, medial thickening, vascular wall inflammation scores and arterial remodeling index were elevated and endothelialization was impaired in arteries with PES. Arteries with PES exhibited significantly worse endothelium-dependent vascular compliance: the stiffness (p<0.001) and reflexion index (p<0.001) were significantly higher and the distensibility index (p<0.001) lower as compared with the arteries with BMS. The endothelium-independent vascular reaction was similarly impaired in arteries with PES, as the stiffness index (p<0.001) and the distensibility index (p<0.001) differed significantly between the PES and BMS groups. Incomplete endothelialization (r=0.617, p<0.001) was significantly associated with the endothelium-dependent increased vascular stiffness. The increased fibrin score (r=0.646, p<0.001), vessel wall inflammation (r=0.657, p<0.001) and medial thickening (r=0.672, p<0.001) correlated significantly with the endothelium-independent stiffness index. CONCLUSIONS Implantation of PES impairs the coronary artery wall structure and the endothelium-dependent and independent vessel wall dynamics more than does the implantation of BMS.