Restored perfusion and reduced inflammation in the infarcted heart after grafting stem cells with a hyaluronan-based scaffold

The aim of this study is to investigate the blood perfusion and the inflammatory response of the myocardial infarct area after transplanting a hyaluronan-based scaffold (HYAFF\uae11) with bone marrow mesenchymal stem cells (MSCs). Nine-week-old female pigs were subjected to a permanent left anterior descending coronary artery ligation for 4 weeks. According to the kind of the graft, the swine subjected to myocardial infarction were divided into the HYAFF\uae11, MSCs, HYAFF\uae11/MSCs and untreated groups. The animals were killed 8 weeks after coronary ligation. Scar perfusion, evaluated by Contrast Enhanced Ultrasound echography, was doubled in the HYAFF\uae11/MSCs group and was comparable with the perfusion of the healthy, non-infarcted hearts. The inflammation score of the MSCs and HYAFF\uae11/MSCs groups was near null, revealing the role of the grafted MSCs in attenuating the cell infiltration, but not the foreign reaction strictly localized around the fibres of the scaffold. Apart from the inflammatory response, the native tissue positively interacted with the HYAFF\uae11/MSCs construct modifying the extracellular matrix with a reduced presence of collagene and increased amount of proteoglycans. The border-zone cardiomyocytes also reacted favourably to the graft as a lower degree of cellular damage was found. This study demonstrates that the transplantation in the myocardial infarct area of autologous MSCs supported by a hyaluronan-based scaffold restores blood perfusion and almost completely abolishes the inflammatory process following an infarction. These beneficial effects are superior to those obtained after grafting only the scaffold or MSCs, suggesting that a synergic action was achieved using the cell-integrated polymer construct

Stem Cells as a therapy for myocardial infarction in animal models

Advances in stem cell biology have challenged the notion that infarcted myocardium is irreparable. The pluripotent ability of stem cells to differentiate into specialized cell lines began to garner intense interest within cardiology when it was shown in animal models that intramyocardial injection of bone marrow stem cells (MSCs), or the mobilization of bone marrow stem cells with spontaneous homing to myocardium, could improve cardiac function and survival after induced myocardial infarction (MI) [1, 2]. Furthermore, the existence of stem cells in myocardium has been identified in animal heart [3, 4], and intense research is under way in an attempt to clarify their potential clinical application for patients with myocardial infarction. To date, in order to identify the best one, different kinds of stem cells have been studied; these have been derived from embryo or adult tissues (i.e. bone marrow, heart, peripheral blood etc.). Currently, three different biologic therapies for cardiovascular diseases are under investigation: cell therapy, gene therapy and the more recent “tissue-engineering” therapy . During my Ph.D. course, first I focalised my study on the isolation and characterization of Cardiac Stem Cells (CSCs) in wild-type and transgenic mice and for this purpose I attended, for more than one year, the Cardiovascular Research Institute of the New York Medical College, in Valhalla (NY, USA) under the direction of Doctor Piero Anversa. During this period I learnt different Immunohistochemical and Biomolecular techniques, useful for investigating the regenerative potential of stem cells. Then, during the next two years, I studied the new approach of cardiac regenerative medicine based on “tissue-engineering” in order to investigate a new strategy to regenerate the infracted myocardium. Tissue-engineering is a promising approach that makes possible the creation of new functional tissue to replace lost or failing tissue. This new discipline combines isolated functioning cells and biodegradable 3-dimensional (3D) polymeric scaffolds. The scaffold temporarily provides the biomechanical support for the cells until they produce their own extracellular matrix. Because tissue-engineering constructs contain living cells, they may have the potential for growth and cellular self-repair and remodeling. In the present study, I examined whether the tissue-engineering strategy within hyaluron-based scaffolds would result in the formation of alternative cardiac tissue that could replace the scar and improve cardiac function after MI in syngeneic heterotopic rat hearts. Rat hearts were explanted, subjected to left coronary descending artery occlusion, and then grafted into the abdomen (aorta-aorta anastomosis) of receiving syngeneic rat. After 2 weeks, a pouch of 3 mm2 was made in the thickness of the ventricular wall at the level of the post-infarction scar. The hyaluronic scaffold, previously engineered for 3 weeks with rat MSCs, was introduced into the pouch and the myocardial edges sutured with few stitches. Two weeks later we evaluated the cardiac function by M-Mode echocardiography and the myocardial morphology by microscope analysis. We chose bone marrow-derived mensenchymal stem cells (MSCs) because they have shown great signaling and regenerative properties when delivered to heart tissue following a myocardial infarction (MI). However, while the object of cell transplantation is to improve ventricular function, cardiac cell transplantation has had limited success because of poor graft viability and low cell retention, that’s why we decided to combine MSCs with a biopolimeric scaffold. At the end of the experiments we observed that the hyaluronan fibres had not been substantially degraded 2 weeks after heart-transplantation. Most MSCs had migrated to the surrounding infarcted area where they were especially found close to small-sized vessels. Scar tissue was moderated in the engrafted region and the thickness of the corresponding ventricular wall was comparable to that of the non-infarcted remote area. Also, the left ventricular shortening fraction, evaluated by M-Mode echocardiography, was found a little bit increased when compared to that measured just before construct transplantation. Therefore, this study suggests that post-infarction myocardial remodelling can be favourably affected by the grafting of MSCs delivered through a hyaluron-based scaffol

Comparison between stem cells harvested from wet and dry lipoaspirates

Adipose-derived stem cells (ASC) are usually isolated from lipoaspirates, but it is not known if the anesthetic solution injected into adipose tissue affects cell yield and functions. Two different samples were drawn from the abdominal region of female subjects. In the first, a physiological solution containing lidocaine/adrenaline was injected (wet liposuction, WL), while in the contralateral area, the sample was collected without injecting any solution (dry liposuction, DL). The aspirates were processed to investigate the yield of the stromal-vascular fraction (SVF) cells and ASC frequency, growth rate, apoptosis, and differentiation potential. The solid dried mass of fresh WL isolates was lower than that of DL isolates (p<0.01) due to the presence, in the former, of a liquid solution. As a consequence, the amount of WL-SVF cells was 18.7% lower than those obtained from DL (p < 0.01); this difference was also observed under culture conditions. In addition, the number of colony-forming unit-fibroblasts (CFU-Fs) obtained from 1 7 10(3) SVF cells was 25.5% lower in WL-aspirates than DL-aspirates (p < 0.05) owing, at least in part, to the observed presence of ASC in the liquid solution of the WL isolates. After WL and DL, no differences were observed in ASC growth rate, apoptosis, or differentiation potential toward adipogenic, osteogenic, and endothelial cell lineages. In conclusion, WL yields about 40% fewer ASC than DL due to the combined effect of tissue dilution and the reduced frequency of ASC in the SVF. The main biological features of ASC are suitable for cell-based therapies

Localization of mesenchymal stem cells grafted with a hyaluronan-based scaffold in the infarcted heart

BACKGROUND: Permanence of grafted stem cells in the infarcted myocardial area has been suggested to be favored by tissue engineering strategies, including the application of a scaffold as a cell support. However, an estimation of how many cells remain localized in the site of transplantation has never been done. The aim of this work was to investigate the localization of mesenchymal stem cells (MSCs) grafted with a well cell-adhesive polymer in the scar region of the infarcted heart. MATERIALS AND METHODS: Rat MSCs were engineered in a hyaluronan-based scaffold (HYAFF(\uae)11) for 3 wk. The hearts of donor rats were also explanted, subjected to coronary artery ligation, and grafted into the abdomen of syngeneic rats. Two wk after coronary ligation a small dish of the HYAFF(\uae)11/MSC construct was introduced into a pouch created in the ventricular wall of the infarct area and left for 2 wk. RESULTS: Under ex vivo conditions, MSCs tightly adhered to the hyaluronan fibers and secreted abundant extracellular matrix. In contrast, HYAFF(\uae)11 was not more surrounded by the engrafted MSCs 2 wk after construct transplantation. Most MSCs migrated near the border zone of the infarcted area close to the coronary vessels. Moreover, the infarcted region of the heart was enriched in capillaries and the degree of fibrosis was attenuated. CONCLUSIONS: Two wk after transplantation most MSCs grafted in the infarcted myocardium with HYAFF(\uae)11 had left the scaffold and moved to the border zone. Nevertheless, this treatment increased the myocardial vascularization and reduced the degree of fibrosis in the scar area