Masato Kanda

Implantation of cardiac progenitor cells using self-assembling peptide improves cardiac function after myocardial infarction.

Implantation of various types of cells into the heart has been reported to be effective for heart failure, however, it is unknown what kinds of cells are most suitable for myocardial repair. To examine which types of cells are most effective, we injected cell-Puramatrix™ (PM) complex into the border area and overlaid the cell-PM patch on the myocardial infarction (MI) area. We compared cardiac morphology and function at 2 weeks after transplantation. Among clonal stem cell antigen-1 positive cardiac progenitors with PM (cSca-1/PM), bone marrow mononuclear cells with PM (BM/PM), skeletal myoblasts with PM (SM/PM), adipose tissue-derived mesenchymal cells with PM (AMC/PM), PM alone (PM), and non-treated MI group (MI), the infarct area of cSca-1/PM was smaller than that of BM/PM, SM/PM, PM and MI. cSca-1/PM and AMC/PM attenuated ventricular enlargement and restored cardiac function in comparison with MI. Capillary density in the infarct area of cSca-1/PM was higher than that of other five groups. The percentage of TUNEL positive cardiomyocytes in the infarct area of cSca-1/PM was lower than that of MI and PM. cSca-1 secreted VEGF and some of them differentiated into cardiomyocytes and vascular smooth muscle cells. These results suggest that transplantation of cSca-1/PM most effectively prevents cardiac remodeling and dysfunction through angiogenesis, inhibition of apoptosis and myocardial regeneration.

Regeneration of the Cardiac Conduction System by Adipose Tissue-Derived Stem Cells

BACKGROUND Adipose tissue is one of the sources of mesenchymal stem cells, which have the potential to differentiate into various types of cells, including myocytes. Whether brown adipose tissue (BAT)-derived cells might differentiate into the cardiac pacemaking-conducting cells, and have the potential to regenerate the cardiac conduction system (CCS), is investigated in this study. METHODSANDRESULTS BAT was isolated from the interscapular area of mice and enzymatically digested before culture. Round or fusiform cells showed spontaneous beating at 4-7 days after culturing of BAT-derived cells. Reverse transcriptase-polymerase chain reaction analysis and immunocytochemical analysis revealed that BAT-derived cells expressed several cardiomyocytes, the CCS and pacemaker (PM) cell marker genes and proteins. Patch-clamp techniques revealed that spontaneous electrical activity and the shape of the action potential showed properties of cardiac PM cells. Next, a complete atrioventricular (AV) block was created in mice and green fluorescent protein-positive (GFP (+)) BAT-derived cells were injected intramyocardially around the AV node. At 1 week after transplantation, 50% of BAT-derived cells injected mice showed a sinus rhythm or a 2:1 AV block. Immunohistochemical analysis revealed that injected GFP (+) cells were engrafted and some GFP (+) cells co-expressed several cardiac PM cell marker proteins. CONCLUSIONS BAT-derived cells differentiate into the CCS and PM-like cells in vitro and in vivo, and may become a useful cell source for arrhythmia therapy.

Anti‐Inflammatory Peptides From Cardiac Progenitors Ameliorate Dysfunction After Myocardial Infarction

Background Cardiac cell therapy has been proposed as one of the new strategies against myocardial infarction. Although several reports showed improvement of the function of ischemic heart, the effects of cell therapy vary among the studies and the mechanisms of the beneficial effects are still unknown. Previously, we reported that clonal stem cell antigen‐1–positive cardiac progenitor cells exerted a therapeutic effect when transplanted into the ischemic heart. Our aims were to identify the cardiac progenitor‐specific paracrine factor and to elucidate the mechanism of its beneficial effect. Methods and Results By using an antibody array, we found that soluble junctional adhesion molecule‐A (JAM‐A) was abundantly secreted from cardiac progenitor cells. Pretreatment of neutrophils with conditioned medium from cultured cardiac progenitor cells or soluble JAM‐A inhibited transendothelial migration and reduced motility of neutrophils. These inhibitory effects were attenuated by anti–JAM‐A neutralizing antibody. Injection of cardiac progenitor cells into infarct heart attenuated neutrophil infiltration and expression of inflammatory cytokines. Injection of soluble JAM‐A–expressing, but not of JAM‐A siRNA–expressing, cardiac progenitor cells into the infarct heart prevented cardiac remodeling and reduced fibrosis area. Conclusions Soluble JAM‐A secreted from cardiac progenitor cells reduces infiltration of neutrophils after myocardial infarction and ameliorates tissue damage through prevention of excess inflammation. Our finding may lead to a new therapy for cardiovascular disease by using the anti‐inflammatory effect of JAM‐A.

Neonatal Rat Heart Response to Pressure Overload

H eart failure is caused by myocyte loss secondary to necrosis and/or apoptosis due to injury or excess workload, and is further complicated by adverse remodeling. Recently, there is increasing evidence refuting the traditional notion that the heart has no capacity to replace cardiomyocytes (CMs). Therefore, the generation of new CMs within the cardiac milieu to replace the injured myocardium is considered one of the main therapeutic strategies for patients with heart failure and limited treatment options. The heart tissue of some teleosts and amphibians has high regenerative potential. However, the innate regenerative ability of the adult mammalian heart is not adequately efficient to replace all damaged CMs; therefore, researchers are in search of the cues that induce regeneration of the myocardium. During the embryonic and fetal periods, mammalian CMs retain growth plasticity under several environmental factors. Postnatal circulatory changes (from low pressure under embryonic circulation, to high pressure under postnatal circulation) usually alter the growth pattern of the heart muscle from cell division to cell enlargement. Recently, several reports have suggested that the neonatal heart regenerates CMs via CM proliferation after apex dissection. This suggests that significant tissue injury may be an environmental cue to enhance CM proliferation; however, conflicting data exist. Furthermore, studies are lacking regarding the proliferation dynamics of neonatal CMs under pathological and exaggerated pressure loads.