BACKGROUND: Recent studies regarding neuronal differentiation of mesenchymal stem cells (MSCs) have primarily focused on induction methods and transplantation in vivo. However, knowledge about the intrinsic regulatory mechanisms underlying neuronal induction of MSCs remains limited and unclear.OBJECTIVE: To elucidate the role of JAK-STAT3 signaling pathway during neuronal differentiation of MSCs using a combination of the JAK-STAT3 signaling inhibitor AG490 and growth factors. DESIGN, TIME AND SETTING: Neural, molecular, biomedical, in vitro experiment was performed at the Laboratory of Pharmacology, School of Pharmacy, Nanjing Medical University between March and December 2008 .MATERIALS: An inhibitor of the JAK-STAT3 signaling pathway was purchased from Calbiochem, USA. Antibody kit for total and phosphorylated STAT3 was purchased from Cell Signaling, USA.METHODS: MSCs from passage 3 were assigned to non-induced, growth factor, and AG490 groups. MAIN OUTCOME MEASURE: The number of cells expressing neuron-specific enolase, microtubule-associated protein, and glial fibrillary acidic protein were determined by immunocytochemistry. Total and phosphorylated (Tyr705) expression levels of STAT3 protein were measured by Western blot analysis.RESULTS: MSCs were transdifferentiated into neuronal- and astrocyte-like phenotypes through the induction of epidermal growth factor, basic fibroblast growth factor, and brain-derived neurotrophic factor. In addition, the JAK-STAT3 signaling pathway was significantly activated during neural differentiation. Expression of phosphorylated (Tyr705) STAT3 was inhibited with AG490 (5 μmol/L) prior to neural induction with epidermal growth factor, basic fibroblast growth factor, and brain-derived neurotrophic factor; proportion of astrocyte-like cells was significantly reduced (P < 0.01), and the proportion of neuronal-like phenotypes was significantly increased (P < 0.01).CONCLUSION: JAK-STAT3 signaling pathway was shown to regulate neuronal induction of bone marrow MSCs. The proportion of MSC-induced neuronal-like cells was increased following treatment with the JAK-STAT3 signaling inhibitor AG490.