Bone marrow cells for cardiac regeneration and repair: current status and issues

Perspective and challenges of mesenchymal stem cells for cardiovascular regeneration

Mesenchymal stem cells (MSCs) exhibit multipotent differentiation potential and can be derived from embryonic, neonatal and adult differentiation stage III tissue sources. While increasing preclinical studies and clinical trials have indicated that MSC-based therapy is a promising strategy for cardiovascular regeneration, there are major challenges to overcome before this stem-cell technology can be widely applied in clinical settings. In this review, the following important issues will be addressed. First, optimal sources of MSC derivation suitable for myocardial repair are not determined. Second, assessments for preclinical and clinical studies of MSCs require more scientific data analysis. Third, mechanisms of MSC-based therapy for cardiovascular regeneration have not been fully understood yet. Finally, the potential benefit-risk ratio of MSC therapy needs to be evaluated systematically. Additionally, future development of MSC therapy will be discussed.

Incorporation of bone marrow cells in pancreatic pseudoislets improves posttransplant vascularization and endocrine function

Failure of revascularization is known to be the major reason for the poor outcome of pancreatic islet transplantation. In this study, we analyzed whether pseudoislets composed of islet cells and bone marrow cells can improve vascularization and function of islet transplants. Pancreatic islets isolated from Syrian golden hamsters were dispersed into single cells for the generation of pseudoislets containing 4×10³ cells. To create bone marrow cell-enriched pseudoislets 2×10³ islet cells were co-cultured with 2×10³ bone marrow cells. Pseudoislets and bone marrow cell-enriched pseudoislets were transplanted syngeneically into skinfold chambers to study graft vascularization by intravital fluorescence microscopy. Native islet transplants served as controls. Bone marrow cell-enriched pseudoislets showed a significantly improved vascularization compared to native islets and pseudoislets. Moreover, bone marrow cell-enriched pseudoislets but not pseudoislets normalized blood glucose levels after transplantation of 1000 islet equivalents under the kidney capsule of streptozotocin-induced diabetic animals, although the bone marrow cell-enriched pseudoislets contained only 50% of islet cells compared to pseudoislets and native islets. Fluorescence microscopy of bone marrow cell-enriched pseudoislets composed of bone marrow cells from GFP-expressing mice showed a distinct fraction of cells expressing both GFP and insulin, indicating a differentiation of bone marrow-derived cells to an insulin-producing cell-type. Thus, enrichment of pseudoislets by bone marrow cells enhances vascularization after transplantation and increases the amount of insulin-producing tissue. Accordingly, bone marrow cell-enriched pseudoislets may represent a novel approach to increase the success rate of islet transplantation.

A novel approach to transplanting bone marrow stem cells to repair human myocardial infarction: delivery via a noninfarct-relative artery

Bone marrow stem cells are able to repair infarcted human myocardium following intracoronary transplantation via the infarct-relative artery. However, traditional reperfusion strategies fail to open the artery in some patients, making effective delivery impossible. Our previous study demonstrated a safe and efficient approach to delivering bone marrow stem cells via a noninfarcted artery in an animal myocardial infarction model. The objective of the present study was to evaluate the safety and feasibility of autologous bone marrow mesenchymal stem cell transplantation via such an approach in patients with acute myocardial infarction (AMI). Sixteen patients with anterior AMI who had successfully undergone percutaneous coronary intervention (PCI) were enrolled in this pilot, randomized study. Three weeks after PCI, cultured bone marrow mesenchymal stem cells were injected into the myocardium via either the infarct-relative artery (left anterior descending branch artery, LAD) or a noninfarct-relative artery (right coronary artery, RCA). The safety and feasibility of the cell infusion were evaluated during the procedure and during 6 months of follow-up. In addition, 2D echocardiography, technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) and 18F-deoxyglucose single photon emission computed tomography were employed to examine cardiac function, myocardial perfusion, and viable cardiomyocytes, respectively, at day 4 after PCI and 6 months after the cell infusion. There were no arrhythmia and any other side-effects, including infections, allergic reactions or adverse clinical events, during, immediately after, or 6 months after cell transplantation. Cardiac function and myocardial perfusion had improved 6 months after PCI/bone marrow stem cells transplantation. Viable cardiomyocytes metabolism was detected in the infarcted areas in both groups after the cell infusion, as demonstrated by 18F-deoxyglucose. Intracoronary infusion of autologous bone marrow mesenchymal stem cells via a noninfarct-relative artery appears safe and feasible in the treatment of patients with AMI.

Bone marrow-derived stem/progenitor cells: their use in clinical studies for the treatment of myocardial infarction

Over the last six years, several centres around the world have started clinical trials to investigate the utilisation of bone marrow-derived cells for myocardial infarction. Different types and numbers of cells have been used assuming they possess a potential to originate new endothelial cells and/or cardiomyocytes to repair/regenerate the ailed heart. Despite diversity in number, clinical status of subjects, route of cell administration, and criteria to evaluate efficacy, the main conclusion drawn from these clinical studies was that such therapies were safe. However, attempts to unify efficacy data have yielded no clear answers, so far. This review offers an in-depth and critical analysis of these trials and intends to evaluate from the cellular biology and clinical cardiology viewpoints, the significant information that has been published since 2002, as well as that emerging from ongoing clinical trials. Emphasis will be placed on cellular types, research designs and methods to evaluate efficacy of each particular treatment modality.