Biochemical and functional characterization of skeletal muscle cells differentiated from tonsil-derived mesenchymal stem cells.

INTRODUCTION/AIMS: Human tonsils are a readily accessible source of stem cells for the potential treatment of skeletal muscle disorders. We reported previously that tonsil-derived mesenchymal stem cells (TMSCs) can differentiate into skeletal muscle cells (SKMCs), which renders TMSCs promising candidates for cell therapy for skeletal muscle disorders. However, the functional properties of the myocytes differentiated from mesenchymal stem cells have not been clearly evaluated. In this study we investigated whether myocytes differentiated from TMSCs (skeletal muscle cells derived from tonsil mesenchymal stem cells [TMSC-SKMCs]) exhibit the functional characteristics of SKMCs. METHODS: To test the insulin reactivity of TMSC-SKMCs, the expression of glucose transporter 4 (GLUT4) and phosphatidylinositol 3-kinase/Akt was analyzed after the cells were treated for 30 minutes with 100 nmol/L insulin in normal or high-glucose medium. We also examined whether these cells formed a neuromuscular junction (NMJ) when cocultured with motor neurons, and whether they were stimulated by electrical signals using whole-cell patch clamping. RESULTS: Skeletal muscle cells derived from tonsil mesenchymal stem cells expressed SKMC markers, such as MYOD, MYH3, MYH8, TNNI1, and TTN, at high levels, and exhibited a multinucleated cell morphology and a myotube-like shape. The expression of the acetylcholine receptor and GLUT4 was confirmed in TMSC-SKMCs. In addition, these cells exhibited insulin-mediated glucose uptake, NMJ formation, and transient changes in cell membrane action potential, all of which are representative functions of human SKMCs. DISCUSSION: Tonsil-derived mesenchymal stem cells can be functionally differentiated into SKMCs and may have potential for clinical application for the treatment of skeletal muscle disorders.

Density-Dependent Differentiation of Tonsil-Derived Mesenchymal Stem Cells into Parathyroid-Hormone-Releasing Cells.

Mesenchymal stem cells (MSCs) can differentiate into endoderm lineages, especially parathyroid-hormone (PTH)-releasing cells. We have previously reported that tonsil-derived MSC (T-MSC) can differentiate into PTH-releasing cells (T-MSC-PTHCs), which restored the parathyroid functions in parathyroidectomy (PTX) rats. In this study, we demonstrate quality optimization by standardizing the differentiation rate for a better clinical application of T-MSC-PTHCs to overcome donor-dependent variation of T-MSCs. Quantitation results of PTH mRNA copy number in the differentiated cells and the PTH concentration in the conditioned medium confirmed that the differentiation efficiency largely varied depending on the cells from each donor. In addition, the differentiation rate of the cells from all the donors greatly improved when differentiation was started at a high cell density (100% confluence). The large-scale expression profiling of T-MSC-PTHCs by RNA sequencing indicated that those genes involved in exiting the differentiation and the cell cycle were the major pathways for the differentiation of T-MSC-PTHCs. Furthermore, the implantation of the T-MSC-PTHCs, which were differentiated at a high cell density embedded in hyaluronic acid, resulted in a higher serum PTH in the PTX model. This standardized efficiency of differentiation into PTHC was achieved by initiating differentiation at a high cell density. Our findings provide a potential solution to overcome the limitations due to donor-dependent variation by establishing a standardized differentiation protocol for the clinical application of T-MSC therapy in treating hypoparathyroidism.

Differentiation of Motor Neuron-Like Cells from Tonsil-Derived Mesenchymal Stem Cells and Their Possible Application to Neuromuscular Junction Formation.

Human tonsil-derived mesenchymal stem cells (T-MSCs) are newly identified MSCs and present typical features of MSCs, including having the differentiation capacity into the three germ layers and excellent proliferation capacity. They are easily sourced and are useful for stem cell therapy in various disease states. We previously reported that T-MSCs could be differentiated into skeletal myocytes and Schwann-like cells; therefore, they are a promising candidate for cell therapies for neuromuscular disease. Motor neurons (MNs), which regulate spontaneous behavior, are affected by a wide range of MN diseases (MNDs) for which there are no effective remedies. We investigated the differentiation potential of MN-like cells derived from T-MSCs (T-MSC-MNCs) for application to therapy of MNDs. After the process of MN differentiation, the expression of MN-related markers, including Islet 1, HB9/HLXB9 (HB9), and choline acetyltransferase (ChAT), was increased when compared with undifferentiated T-MSCs. The secretion of acetylcholine to the conditioned medium was significantly increased after MN differentiation. We cocultured T-MSC-MNCs and human skeletal muscle cells, and confirmed the presence of the acetylcholine receptor clusters, which demonstrated the formation of neuromuscular junctions. The potential functional improvements afforded by these T-MSC-MNCs could be useful in the treatment of MNDs caused by genetic mutation, viral infection, or environmental problems.