Adult BM stem cells regenerate mouse myocardium

Adipose tissue progenitor cells directly interact with endothelial cells to induce vascular network formation

Adipose stromal cells (ASCs) express markers and functional properties of pericytes in vitro and, in combination with endothelial cells (ECs), are able to establish multilayer functional vessels in vivo. However, the factors that coordinate EC-ASC communications to promote migration of these cells toward one another, and their heterotypic assembly into vascular structures are not well defined. To understand the mechanisms of EC-ASC interaction, we developed an in vitro model of coculturing ECs with ASCs in a system containing serum but no additional exogenous cytokines or extracellular matrix (ECM) proteins. We demonstrated that ASCs have a profound potential to stimulate morphogenesis of ECs into branching networks of cord structures. The vascular networks developed in 6 days and were stable for at least 3 weeks. This process was associated with an increase in ECM protein production by ASCs and ECs, alpha-smooth muscle actin expression by ASCs, and increased CD31/platelet endothelial cell adhesion molecule-1 (PECAM-1) surface presentation by ECs. The vascular network formation (VNF) was dependent on matrix metalloproteinase activity and cell communications through vascular endothelial growth factor, hepatocyte growth factor, and platelet-derived growth factor-BB pathways. ASCs exhibited significantly higher potential to stimulate VNF than smooth muscle cells and fibroblasts. Media conditioned by ASCs promoted VNF by ECs cultured on smooth muscle cells and fibroblasts, but could not replace the presence of ASCs in coculture. The presence of ASCs in EC-fibroblast cocultures in a low fraction efficiently stimulated VNF. These findings demonstrate that the vasculogenesis-promoting potential of ASCs depends on interaction with ECs involving contact and likely bi-directional interaction, resulting in modulated secretion of cytokines and ECM proteins.

Therapeutic potential of adipose-derived stem cells in vascular growth and tissue repair

PURPOSE OF REVIEW

Adipose-derived stem cells (ASCs) are readily available from autologous adipose tissue and have been demonstrated to provide significant potential for tissue rescue from, or repair of, damage in multiple animal models. These include models of myocardial infarction, heart failure, hind limb ischemia, and inflammatory conditions. Early clinical studies have now extended testing of the effects of ASC into patients. This review highlights some of the key reports underlining the potential of ASCs, focusing particularly on diseases involving the cardiovascular system, vascular growth, and tissue repair.

RECENT FINDINGS

Clinical applications of ASCs have begun to show early safety results and promising possibility of efficacy in patients with a range of diseases, including acute myocardial infarction, peripheral vascular disease, and soft and bony tissue defects including cranial bone loss, Crohn's-related fistula, and skin wounds. These effects are importantly based on the secretion of trophic and survival factors by these cells and by their participations in the growth and remodeling of blood vessels. These results suggest that ASCs could be a valuable therapeutic option in vascular growth and tissue repair in various clinical settings.

SUMMARY

ASCs may ultimately represent a valuable therapeutic option in tissue rescue and repair based on their ready availability, proangiogenesis and antiapoptotic factor secretion, immunomodulatory effects, and capacity for multilineage differentiation and ready expansion.

Cardiomyogenic stem and progenitor cell plasticity and the dissection of cardiopoiesis

Cell-based therapies hold promise of repairing an injured heart, and the description of stem and progenitor cells with cardiomyogenic potential is critical to its realization. At the vanguard of these efforts are analyses of embryonic stem cells, which clearly have the capacity to generate large numbers of cardiomyocytes in vitro. Through the use of this model system, a number of signaling mechanisms have been worked out that describes at least partially the process of cardiopoiesis. Studies on adult stem and on progenitor cells with cardiomyogenic potential are still in their infancy, and much less is known about the molecular signals that are required to induce the differentiation to cardiomyocytes. It is also unclear whether the pathways are similar or different between embryonic and adult cell-induced cardiomyogenesis, partly because of the continued controversies that surround the stem cell theory of cardiac self-renewal. Irrespective of any perceived or actual limitations, the study of stem and progenitor cells has provided important insights into the process of cardiomyogenesis, and it is likely that future research in this area will turn the promise of repairing an injured heart into a reality.

Immuno-inflammatory regulation effect of mesenchymal stem cell transplantation in a rat model of myocardial infarction

BACKGROUND

Mesenchymal stem cells (MSC) have recently been shown to possess immunomodulatory properties in vitro and in vivo. The present study aimed to investigate the regulatory effect of MSC transplantation on the immuno-inflammatory response in myocardial infarction (MI).

METHODS

MI was induced in Sprague-Dawley rats by left anterior descending coronary artery ligation, and the animals were randomly assigned into the following three groups: sham ( n=8); phosphate-buffered saline (PBS) injected (MI+PBS, n=8); and MSC transplantation (MI+MSC, n=8). BrdU-labeled MSC or PBS was transplanted into peri-infarct myocardium by direct myocardial injection. At 1 and 28 days post-transplantation, cardiac function was evaluated by echocardiography. Transplanted cells were investigated through immunohistochemistry. Lymphocyte cytotoxic activity was evaluated with the crystal violet method. The activity of NF-kappaB and protein expression of tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6 and IL-10 in myocardium were assessed by immunohistochemistry and Western blot.

RESULTS

Echocardiographic examination revealed that the MSC transplantation prevented left ventricular dilation and dysfunction at 28 days after the operation. BrdU-stained cells were found living in host heart 4 weeks after transplantation. MSC transplantation attenuated the cytotoxic activity of spleen lymphocytes. Transplantation of MSC inhibited the activity of NF-kappaB, attenuated the protein production of TNF-alpha and IL-6, and increased the expression of IL-10 in peri-infarct myocardium.

DISCUSSION

MSC transplantation modulated the immuno-inflammatory response in MI. The immuno-inflammatory regulatory effect of MSC transplantation might partly account for the cardiac protection in myocardial infarction.

Parathyroid hormone treatment after myocardial infarction promotes cardiac repair by enhanced neovascularization and cell survival

AIMS

An ongoing concept is that stem cells have the potential to regenerate the injured myocardium. In addition to direct vasorelaxing effects on the vasculature, which are mediated by an increased cAMP production leading to a decreased calcium influx in smooth muscle cells, parathyroid hormone (PTH) was recently shown to facilitate stem cell mobilization. Therefore, we analysed in a murine model of experimental myocardial infarction (MI) the influence of PTH treatment on survival, functional parameters, stem cell migration, and expression of vascular endothelial growth factor A (VEGF-A).

METHODS AND RESULTS

Mice (C57BL/6) were treated with PTH (80 microg/kg/d) for up to 14 days after coronary artery ligation. Functional and immunohistochemical analyses were performed at days 6 and 30 after MI. Stem cells and VEGF expression in the myocardium were analysed by FACS and qRT-PCR at day 2 after MI. PTH-treated animals revealed a significant improvement of post-MI survival and myocardial function that was related to a subsequent reduction of left ventricular wall thinning and scar extension. Infarcted hearts of PTH-treated mice revealed increased numbers of CD45(+)/CD34(+) progenitor cells as well as an upregulation of VEGF-A mRNA associated with increased neovascularization and cell survival.

CONCLUSIONS

PTH application after MI increases migration of angiogenic CD45(+)/CD34(+) progenitor cells to the ischaemic heart, which may attenuate ischaemic cardiomyopathy. As PTH is already used in patients with osteoporosis, our findings may have a direct impact on the initiation of clinical studies in patients with ischaemic heart disease.

The bone marrow--cardiac axis of myocardial regeneration

Congestive heart failure remains the leading cause of morbidity and mortality in the developed world. Current therapies do not address the underlying pathophysiology of this disease, namely, the progressive loss of functional cardiomyocytes. The notion of repairing or regenerating lost myocardium via cell-based therapies remains highly appealing. The recent identification of adult stem cells, including both cardiac stem/progenitor cells and bone marrow stem cells, has triggered an explosive interest in using these cells for physiologically relevant cardiomyogenesis. Enthusiasm for cardiac regeneration via cell therapy has further been fueled by the many encouraging reports in both animals and human studies. Further intensive research in basic science and clinical arenas are needed to make this next great frontier in cardiovascular regenerative medicine a reality. In this review, we focus on the role of bone marrow-derived stem cells and cardiac stem/progenitor cells in cardiomyocyte homeostasis and myocardial repair and regeneration, as well as provide a brief overview of current clinical trials using cell-based therapeutic approaches in patients with heart disease.

Human embryonic stem cell-derived cardiomyocytes: inducing strategies

Cell-based therapy is emerging as an innovative approach for the treatment of degenerative diseases, and stem cells appear to be an ideal source of cells for this. In cardiology, in particular, human embryonic stem cell (hESC)-derived cardiomyocytes theoretically fulfill most, if not all, of the properties of an ideal donor cell, but several critical obstacles need to be overcome. Many research projects are focusing on set-up strategies for directing hESC differentiation toward the cardiac lineage. It is one of the main difficulties in the search to provide a valuable source of cells to effect regeneration of myocardial tissue in patients with severe heart failure. To date, there are no easy and efficient protocols for the induction of hESC differentiation toward the cardiac lineage. Discovering new molecules or tools capable of doing this is imperative.

Bone Marrow Cells and Myocardial Regeneration

Hematopoietic stem cell (HSC) plasticity and its clinical application have been studied profoundly in the past few years. Recent investigations indicate that HSC and other bone marrow stem cells can develop into other tissues. Because of the high morbidity and mortality of myocardial infarction and other heart disorders, myocardial regeneration is a good example of the clinical application of HSC plasticity in regenerative medicine. Preclinical studies in animals suggest that the use of this kind of treatment can reconstruct heart blood vessels, muscle, and function. Some clinical study results have been reported in the past 2 years. In 2003, reports of myocardial regeneration treatment increased significantly. Other studies include observations on the cell surface markers of transplanted cells and treatment efficacy. Some investigations, such as HSC testing, have focused on clinical applications using HSC plasticity and bone marrow transplantation to treat different types of disorders. In this review, we focus on the clinical application of bone marrow cells for myocardial regeneration.