306 IN VITRO CARDIOMYOGENIC AND NEUROGENIC DIFFERENTIATION OF MINIPIG BONE MARROW MESENCHYMAL STEM CELLS

Abstract

Differentiation of mesenchymal stem cells (MSC) into specialised cells in vitro before transplantation may improve the engraftment efficiency of the transplanted cells as well as the safety and efficacy of treatment. To understand the differentiation process and the functional identities of cells in an animal model, we examined the in vitro differentiation capacity of porcine MSC (3–6 passage) into cardiomyocyte-like and neuron-like cells. The MSC isolated from the bone marrow of postnatal miniature piglets [T-type, PWG Micro-pig (R), PWG Genetics, Korea] exhibited a typical fibroblast-like morphology and expressed the specific markers, such as CD29, CD44, and CD90. After 21 days of culture in induction media, MSC revealed the appropriate phenotype of osteocytes (von Kossa and Alizarin red), adipocytes (Oil red O), and chondrocytes (Alcian blue). Ther MSC were further induced into cardiomyogenic and neurogenic differentiation following the protocols described earlier (Tomita et al. 2002 J. Thorac. Cardiovasc. Surg. 123, 1132–1140) and (Woodbury et al. 2002 J. Neurosci. Res. 96, 908–917), respectively, with minor modifications. Expression of lineage-specific markers was evaluated by immunocytochemistry, and RT-PCR and quantitative PCR (RT-qPCR). For cardiomyogenic differentiation, MSC were stimulated with 10 μM 5-azacytidine for 24 h, 3 days, or 7 days, and the cells were maintained in culture for 21 days. Upon induction, MSC exhibited elongated and stick-like morphology with extended cytoplasmic processes, and toward the end of culture, cells formed aggregates and myotube-like structures. Immunostaining was positive for the markers of cardiomyocyte-like cells, such as α-smooth muscle actin, cardiac troponin T, desmin, and α-cardiac actin. The RT-PCR and RT-qPCR analysis showed the expression and a time dependent up-regulation of cardiac troponin T, desmin, α-cardiac actin, and β-myosin heavy chain genes. Following induction with neuronal-specific media for 3 days, above 80% of MSC acquired the morphology of neuron-like cells with bi- or multipolar cell processes forming a network-like structure. Induced cells with neuronal phenotype were positively stained for nestin, neuronal nuclei (NeuN), glial fibrillary acidic protein (GFAP), and neurofilament-M (NF-M). The expression of neural transcripts, such as nestin, GFAP, and NF-M, was further confirmed by RT-PCR and RT-qPCR. In conclusion, our results showed the potential of porcine MSC to differentiate in vitro into cardiomyocyte-like and neuron-like cells, thus offering a useful model for studying their functional and molecular properties before transplantation.