Cardiac repair--fact or fancy?

Nitric oxide-cyclic GMP signaling in stem cell differentiation

The nitric oxide-cyclic GMP (NO-cGMP) pathway mediates important physiological functions associated with various integrative body systems including the cardiovascular and nervous systems. Furthermore, NO regulates cell growth, survival, apoptosis, proliferation, and differentiation at the cellular level. To understand the significance of the NO-cGMP pathway in development and differentiation, studies have been conducted both in developing embryos and in stem cells. Manipulation of the NO-cGMP pathway, by employing activators and inhibitors as pharmacological probes, and genetic manipulation of NO signaling components have implicated the involvement of this pathway in the regulation of stem cell differentiation. This review focuses on some of the work pertaining to the role of NO-cGMP in the differentiation of stem cells into cells of various lineages, particularly into myocardial cells, and in stem cell-based therapy.

Beneficial effects of the extract from Corydalis yanhusuo in rats with heart failure following myocardial infarction

As indicated in ancient Chinese medical books, Corydalis yanhusuo has therapeutic effects on cardiovascular diseases. The analgesic effect of this plant has been fully elucidated, and I-tetrahydropalmatine has been shown to be the main active principle. The aim of this investigation was to evaluate its protective effects in a rat heart failure model. Rats were subjected to coronary artery ligation, and orally administered with ethanolic extract of Corydalis yanhusuo 50, 100, or 200 mg kg−1 daily, from the 7th day after surgery. We measured cardiac function, plasma atrial natriuretic peptide (ANP), relative heart and lung weights, infarct size and ventricular dilatation after treatment for 8 weeks. Administration with Corydalis yanhusuo led to a significant reduction in infarct size and improvement in cardiac function as demonstrated by lower left ventricular end diastolic pressure (LVEDP) and elevated ± dp/dtmax. We also found that Corydalis yanhusuo significantly reduced left ventricular (LV)/body weight ratio, lung/body weight ratio and significantly inhibited neurohormonal activation. Taken together, this study indicated that Corydalis yanhusuo exerted salutary effects on heart failure induced by myocardial infarction in rats.

Mesenchymal stromal cells can be derived from bone marrow CD133+ cells: implications for therapy

It is known that the bone marrow (BM) CD133(+) cells play an important role in the hematopoietic compartment, but this is not their only role. The cells indeed can take part in vascular reconstitution when they become endothelial cells (EC), in skeletal muscle fiber regeneration when there is a switch in muscle precursors, and to cardiomyocyte phenotypic conversion when differentiating in cardiomyocytes-like cells. While the role in hematopoiesis and vasculogenesis of the selected cells is well established, their ability to differentiate along multiple non-EC lineages has not yet been fully elucidated. The goal of this study is to assert whether human CD133(+)BM-derived cells are able to differentiate in vitro, besides to blood cells, cell lineages pertinent to the mesoderm germ layers. To this end, we isolated CD133(+) cells using a clinically approved methodology and compared their differentiation potential to that of hematopoietic progenitor cells (HPCs) and mesenchymal stem cells (MSCs) obtained from the same BM samples. In our culture conditions, CD133 expression was consistently decreased after passage 2, as well as the expression of the stemness markers c-kit and OCT4, whereas expression of Stage Specific Embryonic Antigen 4 (SSEA4) remained consistent in all different conditions. Expanded CD133 were also positive for HLA-ABC, but negative for HLA-DR, in accordance with what has been previously reported for MSCs. Moreover, CD133(+) cells from human BM demonstrated a wide range of differentiation potential, encompassing not only mesodermal but also ectodermal (neurogenic) cell lineages. CD133 antigen could be potentially used to select a cell population with similar characteristics as MSCs for therapeutic applications.

Cord blood cell therapy alters LV remodeling and cytokine expression but does not improve heart function after myocardial infarction in rats

OBJECTIVE

In this study the ability of unrestricted somatic stem cells (USSC) and mononuclear cord blood cells (MN-CBC) was tested to improve heart function and left ventricular (LV) remodeling after myocardial infarction (MI).

METHODS

The cells were delivered by i.v. or intramyocardial injections in rat models of MI by permanent coronary artery occlusion and by ischemia/reperfusion (I/R) injury. Heart function and remodeling was followed by recurrent echocardiography over 8 or 12 weeks after which catheterization was performed.

RESULTS

Although injected labeled cells could be observed within the myocardium for up to 6 d, there was no sign of cardiac regeneration 8 or 12 weeks after MI. However, the mRNA expression of components of the extracellular matrix was attenuated in the infarct scar 12 weeks after MI and cell injection. Additionally, the expression of interleukin (IL)-6 but not of IL-1 beta increased at the site of injury and the adjacent border-zone 12 weeks after I/R and USSC-injection. However, these effects did not translate into improved heart function or attenuated LV dilatation.

CONCLUSION

These data indicate that cord blood cell implantation after MI acts through paracrine mechanisms to modify remodeling rather than myocyte regeneration. The role of myofibroblasts and the optimal conditions of cell application need to be determined to translate these mechanisms into functional improvement.

Drugs, gene transfer, signaling factors: a bench to bedside approach to myocardial stem cell therapy

In the past few years, the dogma that the heart is a terminally differentiated organ has been challenged. Evidence from preclinical investigations emerged that there are cells, even in the heart itself, that may be able to restore impaired cardiac function after myocardial infarction. Although the exact mechanisms by which the infarcted heart can be repaired by stem cells are not yet fully defined, there is a new optimism among cardiologists that this treatment will prove successful in addressing the cause of heart failure after myocardial infarction-myocyte loss. Despite the promising preliminary data of human myocardial stem cell trials, scientists have also focused on the possibility of enhancing the underlying mechanisms of stem cell repair to gain healthier myocardial tissue. Attempts to induce neo-angiogenesis by transfecting stem cells with signaling factors (such as VEGF), to raise the number of endothelial progenitor cells with medical treatments (such as statins), to transfect stem cells with heat shock protein 70 (as a cardioprotective agent against ischemia) and to enhance the healing process after myocardial infarction with the use of various forms of stimulating factors (G-CSF, SCF, GM-CSF) have been made with notable results. In this article, we summarize the evidence from preclinical and clinical myocardial stem cell studies that have addressed the possibility of enhancing the regenerative capacity of cells used after myocardial infarction.