Construction of engineered myocardial tissues in vitro with cardiomyocyte­like cells and a polylactic­co­glycolic acid polymer.

The aim of the present study was to explore the feasibility of the construction of engineered myocardial tissues in vitro with cardiomyocyte­like cells derived from bone marrow mesenchymal stem cells (BMMSCs) and a polylactic­co­glycolic acid (PLGA) polymer. The PLGA polymer was sheared into square pieces (10x10x1 mm), sterilized by Co60 irradiation, and hydrated in Dulbecco's modified Eagle's medium for 1 h. BMMSCs were isolated from the bone marrow of Sprague­Dawley rats and the third passage cells were induced by 5­azacytidine (5­aza). Following successful induction, the cells were trypsinized and suspended at a density of 1x109/ml. Then, the cell suspension was added to the PLGA scaffold and cultured for 14 days. The morphological changes of BMMSCs were observed using phase contrast microscopy. Immunofluorescence staining was used to identify the cardiomyocyte­like cells. Hematoxylin and eosin (H&E) and immunohistochemical staining were used to observe the morphology of the engineered myocardial tissues. The cell adhesion rates and scanning electron microscopy were used to observe the compatibility of the cardiomyocyte­like cells and PLGA. Transmission electron microscopy was used to view the ultrastructure of the engineered myocardial tissues. BMMSCs in primary culture presented round or short spindle cell morphologies. Following induction by 5­aza, the cells exhibited a long spindle shape and a parallel arrangement. Analysis of the cell adhesion rates demonstrated that the majority of the cardiomyocyte­like cells had adhered to the PLGA scaffolds at 24 h. H&E staining suggested that the cardiomyocyte­like cells with spindle nuclei were evenly distributed in the PLGA scaffold. Immunofluorescence staining revealed that the cardiomyocyte­like cells were positive for cardiac troponin I. Scanning electron microscopy demonstrated that the inoculated cells were well attached to the PLGA scaffold. Transmission electron microscopy indicated that the engineered myocardial tissues contained well­arranged myofilaments, desmosomes, gap junction and Z line­like structures. The present study successfully constructed engineered myocardial tissues in vitro with a PLGA polymer and cardiomyocyte­like cells derived from BMMSCs, which are likely to share various structural similarities with the original heart tissue.