Adult marrow-derived Mesenchymal Stem Cells (MSCs) are capable of dividing and their progeny are further capable of differentiating into one of several mesenchymal phenotypes such as osteoblasts, chondrocytes, myocytes, marrow stromal cells, tendon-ligament fibroblasts, and adipocytes. In addition, these MSCs secrete a variety of cytokines and growth factors that have both paracrine and autocrine activities. These secreted bioactive factors suppress the local immune system, inhibit fibrosis (scar formation) and apoptosis, enhance angiogenesis, and stimulate mitosis and differentiation of tissue-intrinsic reparative or stem cells. These effects, which are referred to as trophic effects, are distinct from the direct differentiation of MSCs into repair tissue. Several studies which tested the use of MSCs in models of infarct (injured heart), stroke (brain), or meniscus regeneration models are reviewed within the context of MSC-mediated trophic effects in tissue repair.

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Mesenchymal stem cells as trophic mediators.

Mesenchymal stem/stromal cells (MSCs) comprise a heterogeneous population of cells with multilineage differentiation potential, the ability to modulate oxidative stress, and secrete various cytokines and growth factors that can have immunomodulatory, angiogenic, anti-inflammatory and anti-apoptotic effects. Recent data indicate that these paracrine factors may play a key role in MSC-mediated effects in modulating various acute and chronic pathological conditions. MSCs are found in virtually all organs of the body. Bone marrow-derived MSCs (BM-MSCs) were discovered first, and the bone marrow was considered the main source of MSCs for clinical application. Subsequently, MSCs have been isolated from various other sources with the adipose tissue, serving as one of the alternatives to bone marrow. Adipose tissue-derived MSCs (ASCs) can be more easily isolated; this approach is safer, and also, considerably larger amounts of ASCs can be obtained compared with the bone marrow. ASCs and BM-MSCs share many biological characteristics; however, there are some differences in their immunophenotype, differentiation potential, transcriptome, proteome, and immunomodulatory activity. Some of these differences may represent specific features of BM-MSCs and ASCs, while others are suggestive of the inherent heterogeneity of both BM-MSC and ASC populations. Still other differences may simply be related to different isolation and culture protocols. Most importantly, despite the minor differences between these MSC populations, ASCs seem to be as effective as BM-MSCs in clinical application, and, in some cases, may be better suited than BM-MSCs. In this review, we will examine in detail the ontology, biology, preclinical, and clinical application of BM-MSCs versus ASCs.

Same or Not the Same? Comparison of Adipose Tissue-Derived Versus Bone Marrow-Derived Mesenchymal Stem and Stromal Cells

Human embryonic stem cells (hESCs) can differentiate into cardiomyocytes, but the efficiency of this process is low We routinely induce cardiomyocyte differentiation of the HES-2 cell line by coculture with a visceral endoderm-like cell line, END-2, in the presence of 20% fetal calf serum (FCS) In this study, we demonstrate a striking inverse relationship between cardiomyocyte differentiation and the concentration of FCS during HES-2-END-2 coculture The number of beating areas in the cocultures was increased 24-fold in the absence of FCS compared with the presence of 20% FCS An additional 40% increase in the number of beating areas was observed when ascorbic acid was added to serum-free cocultures The increase in serum-free cocultures was accompanied by increased mRNA and protein expression of cardiac markers and of Isl1, a marker of cardiac progenitor cells The number of beating areas increased up to 12 days after initiation of coculture of HES-2 with END-2 cells However, the number of alpha-actinin-positive cardiomyocytes per beating area did not differ significantly between serum-free cocultures (503 +/- 179; mean +/- standard error of the mean) and 20% FCS cocultures (312 +/- 227) The stimulating effect of serum-free coculture on cardiomyocyte differentiation was observed not only in HES-2 but also in the HES-3 and HES-4 cell lines To produce sufficient cardiomyocytes for cell replacement therapy in the future, upscaling cardiomyocyte formation from hESCs is essential The present data provide a step in this direction and represent an improved in vitro model, without interfering factors in serum, for testing other factors that might promote cardiomyocyte differentiation

https://stemcellsjournals.onlinelibrary.wiley.com/doi/pdf/10.1634/stemcells.2004-0184

Increased cardiomyocyte differentiation from human embryonic stem cells in serum-free cultures.

Despite substantial clinical advances over the past 65 years, cardiovascular disease remains the leading cause of death in America The past 15 years has witnessed major basic and translational interest in the use of stem and precursor cells as a therapeutic agent for chronically injured organs Among the cell types under investigation, adult mesenchymal stem cells are widely studied, and in early stage, clinical studies show promise for repair and regeneration of cardiac tissues The ability of mesenchymal stem cells to differentiate into mesoderm- and nonmesoderm-derived tissues, their immunomodulatory effects, their availability, and their key role in maintaining and replenishing endogenous stem cell niches have rendered them one of the most heavily investigated and clinically tested type of stem cell Accumulating data from preclinical and early phase clinical trials document their safety when delivered as either autologous or allogeneic forms in a range of cardiovascular diseases, but also importantly define parameters of clinical efficacy that justify further investigation in larger clinical trials Here, we review the biology of mesenchymal stem cells, their interaction with endogenous molecular and cellular pathways, and their modulation of immune responses Additionally, we discuss factors that enhance their proliferative and regenerative ability and factors that may hinder their effectiveness in the clinical setting

Use of Mesenchymal Stem Cells for Therapy of Cardiac Disease

Mesenchymal stem cells (MSCs) are adult stem cells that hold great promise in the field of regenerative medicine. They can be isolated from almost any tissue of the body and display, after expansion, very similar properties and minor differences, probably due to their microenvironment of origin. Expansion in vitro can be obtained in cytokine-free, serum-enriched media, as well as in serum-free, basic fibroblast growth factor-enriched media. A detailed immunophenotypic analysis is required to test the purity of the preparation, but no unique distinguishing marker has been described as yet. Functional assays, that is, differentiation studies in vitro, are needed to prove multilineage differentiation of expanded cells, and demonstration of pluripotency is necessary to identify most immature precursors. MSCs show powerful immunomodulative properties toward most of the cells of the immune system: this strengthens the theoretical rationale for their use also in an allogeneic setting across the major histocompatibility complex (MHC) immunological barriers. Systemic intravenous injection and local use have been tried: after systemic injection, MSCs show a high degree of chemotaxis based on pro-inflammatory cytokines, and localize at inflamed and neoplastic tissues; local regeneration has been improved using synthetic, as well as organic scaffolds. On the other hand, inadequate heterotopic in vivo differentiation and neoplastic transformation are potential risks of this form of cell therapy, even if evidence of this sort has been collected only from studies in mice, and generally after prolonged in vitro expansion. This review tries to provide a detailed technical overview of the methods used for human bone-marrow (BM)-derived and adipose-tissue (AT)-derived MSC isolation, in vitro expansion, and characterization for tissue repair. We chose to use BM-MSCs as a model to describe techniques that have been used for MSC isolation and expansion from very different sources, and AT-MSCs as an example of a reliable and increasingly common alternative source.

Human Bone Marrow and Adipose Tissue Mesenchymal Stem Cells: A User's Guide

Ex vivo differentiation of human adult bone marrow stem cells into cardiomyocyte-like cells.

Telocytes (TCs) with exceptionally long cellular processes of telopodes have been described in human epicardium to act as structural supporting cells in the heart. We examined myocardial chamber-specific TCs identified in atrial and ventricular fibroblast culture using immunocytochemistry and studied their electrophysiological property by whole-cell patch clamp. Atrial and ventricular TCs with extended telopodes and alternating podoms and podomers that expressed CD34, c-Kit and PDGFR-β were identified. These cells expressed large conductance Ca2+-activated K+ current (BKCa) and inwardly rectifying K+ current (IKir), but not transient outward K+ current (Ito) and ATP-sensitive potassium current (KATP). The active channels were functionally competent with demonstrated modulatory response to H2S and transforming growth factor (TGF)-β1 whereby H2S significantly inhibited the stimulatory effect of TGF-β1 on current density of both BKCa and IKir. Furthermore, H2S attenuated TGF-β1-stimulated KCa1.1/Kv1.1 (encode BKCa) and Kir2.1 (encode IKir) expression in TCs. Our results show that functionally competent K+ channels are present in human atrial and ventricular TCs and their modulation may have significant implications in myocardial physiopathology.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/jcmm.12240

Electrophysiology of human cardiac atrial and ventricular telocytes

Cardiac fibroblasts are crucial in pathophysiology of the myocardium whereby their aberrant proliferation has significant impact on cardiac function. Hydrogen sulphide (H2S) is a gaseous modulator of potassium channels on cardiomyocytes and has been reported to attenuate cardiac fibrosis. Yet, the mechanism of H2S in modulating proliferation of cardiac fibroblasts remains poorly understood. We hypothesized that H2S inhibits proliferative response of atrial fibroblasts through modulation of potassium channels. Biophysical property of potassium channels in human atrial fibroblasts was examined by whole-cell patch clamp technique and their cellular proliferation in response to H2S was assessed by BrdU assay. Large conductance Ca(2+)-activated K(+) current (BK(Ca)), transient outward K(+) current (I(to)) and inwardly rectifying K(+) current (IK(ir)) were found in human atrial fibroblasts. Current density of BK(Ca) (IC50 = 69.4 μM; n = 6), I(to) (IC50 = 55.1 μM; n = 6) and IK(ir) (IC50 = 78.9 μM; n = 6) was significantly decreased (P < 0.05) by acute exposure to NaHS (a H2S donor) in atrial fibroblasts. Furthermore, NaHS (100-500 μM) inhibited fibroblast proliferation induced by transforming growth factor-β1 (TGF-β1; 1 ng/ml), Ang II (100 nM) or 20% FBS. Pre-conditioning of fibroblasts with NaHS decreased basal expression of Kv4.3 (encode I(to)), but not KCa1.1 (encode BK(Ca)) and Kir2.1 (encode IK(ir)). Furthermore, H2S significantly attenuated TGF-β1-stimulated Kv4.3 and α-smooth muscle actin expression, which coincided with its inhibition of TGF-β-induced myofibroblast transformation. Our results show that H2S attenuates atrial fibroblast proliferation via suppression of K(+) channel activity and moderates their differentiation towards myofibroblasts.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/jcmm.12114

Hydrogen sulphide suppresses human atrial fibroblast proliferation and transformation to myofibroblasts.

https://www.annalsthoracicsurgery.org/article/S0003-4975(10)02421-5/pdf

Infected Coronary Artery Pseudoaneurysm After Repeated Percutaneous Coronary Intervention

Aortic saddle embolus often presents with acute lower limb ischaemia or neurological deficits.1 ,2 Other unusual presentations may occasionally be encountered.

A 60-year-old woman with a history of an old anterior myocardial infarction presented to the emergency department with acute pulmonary oedema. The ECG showed non-specific ST abnormalities with slightly raised cardiac enzymes. An urgent coronary angiogram was performed to rule out cardiac …

https://heartasia.bmj.com/content/heartasia/6/1/10.full.pdf

Yeow Leng Chua

Papers

Ex vivo differentiation of human adult bone marrow stem cells into cardiomyocyte-like cells.

Electrophysiology of human cardiac atrial and ventricular telocytes

Hydrogen sulphide suppresses human atrial fibroblast proliferation and transformation to myofibroblasts.

Infected Coronary Artery Pseudoaneurysm After Repeated Percutaneous Coronary Intervention

An unusual presentation of aortic saddle embolus