RESUMO
PURPOSE: For regenerative and cellular therapies of the urinary tract system, autologous bladder smooth muscle cells (SMCs) have several limitations, including constricted in vitro proliferation capacity and, more importantly, inability to be used in malignant conditions. The use of in vitro (pre-)differentiated multipotential adult progenitor cells may help to overcome the shortcomings associated with primary cells. METHODS: By mimicking environmental conditions of the bladder wall, we investigated in vitro effects of growth factor applications and epithelial-mesenchymal interactions on smooth muscle gene expression and on the morphological appearance of adherent bone marrow stromal cells (BMSCs). RESULTS: Transcription growth factor beta-1 (TGFbeta-1) upregulated the transcription of myogenic gene desmin and smooth muscle actin-gamma2 in cultured BMSCs. Stimulatory effects were significantly increased by coculture with urothelial cells. Prolonged stimulation times and epigenetic modifications further enhanced transcription levels, indicating a dose-response relationship. Immunocytochemical staining of in vitro-differentiated BMSCs revealed expression of myogenic protein alpha-smooth muscle actin and desmin, and changes in morphological appearance from a fusiform convex shape to a laminar flattened shape with filamentous inclusions similar to the appearance of bladder SMCs. In contrast to the TGFbeta-1 action, application of vascular endothelial growth factor (VEGF) did not affect the cells. CONCLUSIONS: The combined application of TGFbeta-1 and epithelial-mesenchymal interactions promoted in vitro outgrowth of cells with a smooth muscle-like phenotype from a selected adherent murine bone marrow-derived cell population.