Intravenous delivery of autologous mesenchymal stem cells limits infarct size and improves left ventricular function in the infarcted porcine heart

Ultrasound-mediated microbubble destruction enhances the efficacy of bone marrow mesenchymal stem cell transplantation and cardiac function

1. Application of ultrasound (US) to intravascular microbubble (MB) contrast agents causes small capillary ruptures. The purpose of the present study was to examine the effects of US-mediated MB destruction on bone marrow mesenchymal stem cell (BMSC) transplantation into the infarcted myocardium and to evaluate whether this approach could improve cardiac function. 2. Ultrasound was applied to the anterior chest of rabbits after intravenous injection of MB followed by infusion of BMSC. There were four groups investigated: (i) a control group, in which neither US nor MB were used prior to infusion of BMSC; (ii) one group subjected to US alone prior to infusion of BMSC; (iii) another group injected with MB prior to infusion of BMSC; and (iv) a group in which US was applied to MB prior to the infusion of BMSC. Cardiac function was evaluated by echocardiography 24 h and 4 weeks after cell transplantation. All rabbits were killed to enable histological and immunochemical examination. 3. Echocardiography 24 h after infusion of BMSC indicated no difference in cardiac function between any of the groups, as assessed by left ventricular ejection fraction (LVEF), left ventricular end-diastolic dimensions (LVDD), left ventricular systolic diameter (LVSD) and fractional shortening (FS%; all P > 0.05). However, 4 weeks after BMSC transplantation, there was a significant improvement in LVEF in the group subjected to US plus MB compared with the control, US alone and MB alone groups (59.5 +/- 3.5, 52.5 +/- 5.5, 52.8 +/- 5.2 and 51.1 +/- 3.5%, respectively; all P < 0.05). In addition, treatment with US plus MB significantly reduced LVDD and LVSD and increased capillary density in the infarcted area. 4. In conslusion, the results of the present study indicate that using US-mediated MB destruction prior to BMSC transplantation into the infarcted myocardium improves the effectiveness of cardiac cell therapy and cardiac function in rabbits.

Intravenous infusion of mesenchymal stem cells enhances regional perfusion and improves ventricular function in a porcine model of myocardial infarction

Transplantation of stem cells may improve regional perfusion and post-infarct ventricular function, but the optimal dose and efficacy of cell delivery via the intravenous route has not been determined. This study tested the hypothesis that intravenous infusion of bone marrow-derived mesenchymal stem cells (MSCs) enhances regional perfusion and improves ventricular function after myocardial infarction. In a closed-chest pig model, the LAD coronary artery was occluded for 75 min by angioplasty balloon inflation followed by 12 weeks of reperfusion. After 15 min of reperfusion, pigs randomly received 1 of 4 treatments: (1) Vehicle (Control, n = 10); (2) 1 x 10(6) MSCs/kg (1 mill, n = 7); (3) 3 x 10(6) MSCs/kg (3 mill, n = 8) and (4) 10 x 10(6) MSCs/kg (10 mill, n = 8). Angiogenesis was demonstrated by immunohistochemical staining, myocardial blood flow (steady state and vasodilator reserve) was measured using 15 microm neutron-activated microspheres, and cardiac function was determined by contrast left ventriculography (ejection fraction) and pressure-volume relationships. After 12 week of reperfusion, von Willebrand Factor-positive vessels and tissue vascular endothelial growth factor (VEGF) expression in the scar zone was significantly greater in all MSCs-treated animals relative to Control. Steady state myocardial blood flow in the scar tissue was comparable among groups. However, adenosine recruited vasodilator reserve in the scar zone induced by intracoronary adenosine was significantly higher in the MSC-treated animals compared to Control. Furthermore, preload-recruitable stroke work and systolic performance were significantly greater compared to Control. In conclusion, these data demonstrate that intravenous delivery of MSCs during early reperfusion augments vasculogenesis, enhances regional perfusion, and improves post-infarct ventricular function. The results suggest that intravenous infusion of MSCs is an effective modality for the treatment of ischemia/reperfusion induced myocardial injury.

Mesenchymal stem cell administration at coronary artery reperfusion in the rat by two delivery routes: a quantitative assessment

AIMS

Ideally, mesenchymal stem cells (MSC) home to and/or remain at the site of damaged myocardium when administered after myocardial infarction. However, MSC may not remain in the heart, but instead relocate to other areas. We investigated quantitatively the distribution of labeled rat MSC, given by two routes after coronary artery occlusion/reperfusion in rats.

MAIN METHODS

Rats were subjected to 45 min of coronary artery occlusion and 7 days of reperfusion. Before reperfusion rats received 2 x 10(6) MSC, labeled with europium, injected directly into the ischemic region of the heart (n = 9) or intravenously (n = 8). After 1 week tissues were analyzed for label content together with a standard curve of known quantities of labeled MSC.

KEY FINDINGS

In rats receiving cells injected directly into the myocardium, 15% of labeled cells were retained in the heart. When the cells were administered intravenously, no MSC were detected in the heart. The route of administration did not affect distribution to other organs, as the number of MSC in liver, spleen and lung was similar with both routes of delivery.

SIGNIFICANCE

Even with direct intramyocardial injection, only a small proportion of the cells are retained in the heart, instead traveling to other organs. With intravenous injection there was no evidence that cells "homed" to the damaged heart. Although cell delivery to the heart was significantly affected by the route of administration, the distribution of cells to other organs was similar with both routes of administration.

Cell therapy in congestive heart failure

Congestive heart failure (CHF) has emerged as a major worldwide epidemic and its main causes seem to be the aging of the population and the survival of patients with post-myocardial infarction. Cardiomyocyte dropout (necrosis and apoptosis) plays a critical role in the progress of CHF; thus treatment of CHF by exogenous cell implantation will be a promising medical approach. In the acute phase of cardiac damage cardiac stem cells (CSCs) within the heart divide symmetrically and/or asymmetrically in response to the change of heart homeostasis, and at the same time homing of bone marrow stem cells (BMCs) to injured area is thought to occur, which not only reconstitutes CSC population to normal levels but also repairs the heart by differentiation into cardiac tissue. So far, basic studies by using potential sources such as BMCs and CSCs to treat animal CHF have shown improved ventricular remodelling and heart function. Recently, however, a few of randomized, double-blind, placebo-controlled clinical trials demonstrated mixed results in heart failure with BMC therapy during acute myocardial infarction.

Porcine embryonic stem cells: Facts, challenges and hopes

Embryonic stem cells (ESCs) represent a promising tool for cell therapy, regenerative medicine and tissue repair. At the same time they constitute an invaluable model for basic investigations in developmental biology, nuclear reprogramming and differentiation process. ESCs are very unique due to their unlimited self-renewal ability and high plasticity that allow them to differentiate into all embryonic tissues. However, these properties have been so far only demonstrated in the mouse and, to a lesser extent, in man. Assessment of ESC capabilities in species different from the mouse is an ongoing topic of interest and is crucial in view of their potential use as experimental models in pre-clinical applications. The mouse model is not adequate when long-term effects of cell replacement need to be evaluated. The pig has been considered for a long time among the best models for pre-clinical development of therapeutic approaches and represents an innovative model due to its morphological and functional affinity with man; therefore, pig ESCs are attracting renewed interest. However, a number of open questions need to be addressed since no validated protocols for the derivation and maintenance of pig ESCs have yet been established. In the present paper data from the literature will be presented together with experimental evidence recently obtained in our laboratory. We will discuss aspects related to the timing of isolation, the initiation of primary cultures, the use of different culture conditions and cytokines. The identification of pluripotency-related molecular markers in the pig will also be examined. Finally, the ability to respond to specifically formulated medium with spontaneous as well as induced differentiation will be assessed.

Atrial-radiofrequency catheter ablation mediated targeting of mesenchymal stromal cells

Sinus node dysfunction and high-degree heart block are the major causes for electronic pacemaker implantation. Recently, genetically modified mesenchymal stromal cells (MSCs, also known as "mesenchymal stem cells") were demonstrated to generate pacemaker function in vivo. However, experimental approaches typically use open thoracotomy for direct cell injection into the myocardium. Future clinical implementation, however, essentially requires development of more gentle methods to precisely and efficiently apply specified stem cells at specific cardiac locations. In a "proof of concept" study, we performed selective power-controlled radiofrequency catheter ablation (RFCA) with eight ablation pulses (30 W, 60 seconds each) to induce heat-mediated lesions at the auricles of the cardiac right atrium of four healthy foxhounds. The next day, allogeneic MSCs (4.3 x 10(5) cells per kilogram of body weight) labeled with superparamagnetic iron oxide particles (SPIOs) were infused intravenously. Hearts were explanted 8 days later. High numbers of SPIO-labeled cells were identified in areas surrounding the RFCA-induced lesions by Prussian blue staining. Antibody staining revealed SPIO-labeled cells being positive for the typical MSC surface antigen CD44. In contrast, low levels of calprotectin, an antigen found on monocytes and macrophages, indicated negligible infiltration of monocytes in MSC-positive areas. Thus, RFCA allows targeting of MSCs to the cardiac right atrium, adjacent to the sinoatrial node, providing an opportunity to rescue or generate pacemaker function without open thoracotomy and direct injection of MSCs. This method presents a new strategy for cardiac stem cell application leading to an efficient guidance of MSCs into the myocardium. Disclosure of potential conflicts of interest is found at the end of this article.