2/27/2023 0 Comments Cell fragmentsThe dissociated MSCs obtained by traditional trypsinization were used as a control. Transplantation of the MSC sheet fragments to induce tissue regeneration and improve cardiac functions in a syngeneic rat model with infarcted myocardium was investigated. Cell morphology, endogenous ECM, intercellular junctions, and integrative adhesive agents of the MSC sheet fragments, before and after injection through a needle, were examined in vitro. Employing a similar cell-sheet culture system, construction of MSC sheet fragments was reported in the study. 13 Apparently, the physical size of a complete cell-sheet harvested from the coated TCPS dish is too bulky for intramuscular injection. In our recent study, a novel method, using a thermo-responsive hydrogel coated on TCPS dishes, was developed for harvesting living cell sheets. 11, 12 They demonstrated that monolayered MSCs attached onto the anterior wall of the scarred myocardium reversed wall thinning in the scar area and improved cardiac functions in rats with myocardial infarction. Cell sheet engineering has been developed as an alternative approach for tissue engineering by Okano's group. In the study, we hypothesized that the use of continuous cell sheets, with the preservation of endogenous ECM, intercellular junctions, and integrative adhesive agents, may be used to overcome the above-mentioned problems and is therefore beneficial for cell transplantation. 9, 10 These facts can be deleterious to cell-transplantation therapy. 8 Additionally, following injection of the dissociated cells, retention of the transplanted cells in the injected area remains a central issue. 7 However, the use of enzymes commonly dissociates the cultured cells and disrupts their micro-intercellular junctions, extracellular matrix (ECM), and integrative adhesive agents. Upon confluence, detachment of the cultured cells from TCPS dishes usually requires using a proteolytic enzyme such as trypsin or dispase. Prior to cell transplantation, a large scale of the desired cell types must be expanded in vitro on tissue culture polystyrene (TCPS) dishes. 1–3 Several studies performed on rodents and pigs suggested that bone marrow-derived mesenchymal stem cells (MSCs) own the potency to differentiate into a variety of lineages, including endothelial cells, vascular smooth muscle cells, and cardiomyocytes in the heart. 2–4 It was shown that cell transplantation via local intramuscular injection is a promising therapy for patients with myocardial infarction. 1 Recently, the identification of stem cells capable of contributing to tissue regeneration has raised the possibility that cell therapy could be employed for repair of damaged myocardium. Myocardial infarction leads to loss of tissue and impairment of cardiac performance. Myocardial infarction, Cell transplantation, Cell sheet, Tissue regeneration, Angiogenesis 1. Additionally, transplantation of the MSC sheet fragments stimulated a significant increase in vascular density ( P < 0.05) and enhanced the graft/host cell connection. The MSC sheet fragments were able to conform and align their inherent ECM along the interstices of the muscular tissues at the injection sites, while only a few cells were identified in the dissociated MSC group at 12 weeks postoperatively. The results obtained in the echocardiography and pressure measurements revealed a superior heart function in the MSC sheet fragment group compared with the dissociated MSC group ( P < 0.05). After injection, the MSC sheet fragments remained intact, while the complete cell sheets were torn into pieces. At retrieval, the hearts were fixed for histological evaluation. Echocardiography and pressure measurements were assessed postoperatively. There were four treatment groups (n ≥ 10): sham phosphate buffered saline dissociated MSCs and MSC sheet fragments. Thirty minutes after myocardial infarction, an intramyocardial injection was conducted with a needle directly into the peri-infarct areas. Experimental myocardial infarction was created in male syngeneic Lewis rats. Mesenchymal stem cell (MSC) sheet fragments with ECM were fabricated.
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