Mechanisms of differentiation of mesenchymal stem cells and their functional roles in diseases

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To clarify the differential mechanisms of mesenchymal cells, the following experiments were performed using undifferentiated mesenchymal stem cell lines (MT-9, TSD-B9). MT-9 is a cell line isolated from a rat malignant fibrous histiocytoma having pluripotential differentiation, and TSD-B9 is a cell line derived from a rat malignant teratoma, of which the origin is gonadal germ cells capable of differentiating towards endodermal, mesodermal and ectodermal tissues.1.Osteoblastic differentiation : The addition of a supplement for osteoblastic differentiation, including BMP-2, to these cell lines increased calcified areas, demonstrable by von Kossa stain, and showed an elevated alkaline phosphatase in supernatants ; these are indicators of osteoblastic differentiation.2.Lipoblastic differentiation : The addition of a supplement for lipoblastic differentiation, including indomethacin, dexamethasone and insulin, to these cell lines increased the number of cells having oil red O-stainable lipids in the cytoplasm. The stain is useful for detection of lipoblastic cells.3.Myofibroblastic differentiation : The treatment with TGF-β1, a fibrogenic factor in fibrotic diseases, increased the number of cells immuno-reacting to α-smooth muscle actin (α-SMA) ; the increase was demonstrated by the western blotting. α-SMA-expressing cells are regarded as myofibroblasts.5.These studies partly clarified the mechanisms of mesenchymal differentiation, and these cell lines would prove useful for investigating the mechanisms.6.Furthermore, a new cell line was established from a rat malignant fibrous histiocytoma arising in the subcutis, showing histiocytic nature, and another cell line was isolated from a rat malignant schwannoma generating from the uterine cervix. These cell lines would become also beneficial tools for studies on mesenchymal differentiation.