BACKGROUND: Chemical induction has been shown to be effective at promoting the differentiation of bone marrow-derived mesenchymal stem cells (MSCs). However, these inductors have cytotoxicity side effects that may damage cells over time. Traditional Chinese medicines avoid this disadvantage while still producing effective induction.OBJECTIVE: To investigate the influence of Radix Astragali (Huangqi) on the differentiation of MSCs.DESIGN, TIME AND SETTING: In vitro study of traditional Chinese medicine in neural stem cell differentiation. The experiment was performed at the Central Laboratory of Hebei North University between April and June 2007.MATERIALS: Radix Astragafi solution (lot No. 060105; license No. Z53021585) was purchased from Daii Pharmaceutical Co., Ltd., China; rabbit anti-rat nestin, rabbit anti-rat neuron-specific enolase (NSE), mouse anti-rat microtubule-associated protein 2, and rabbit anti-rat glial fibrillary acidic protein were purchased from Wuhan Boster, China.METHODS: Whole bone marrow was isolated from the femur and tibia of 6-week-old male Wistar rats and subcultured. The fourth passage of MSCs were harvested and induced by different concentrations (50, 100, 200, 400 g/L) of Radix Astragali.MAIN OUTCOME MEASURES: Hematoxylin-eosin staining was used to observe MSC morphology after 24 hours of induction. Immunocytochemistry was employed to observe the expression of NSE (specific neuronal marker), nestin (marker of neural stem cell), glial fibrillary acidic protein and microtubule-associated protein 2 (markers of astrocytes).RESULTS: Following Radix Astragafi treatment, changes occurred in cell morphology including: cell body pyknosis; thin and long processes formed in some cells, with growth corresponding to drug concentration and induction time; and the formation of network-like connections between some cells.With increasing drug concentration and induction time, nestin expression was upregulated, and the number of positive cells increased; cells produced NSE, glial fibrillary acidic protein and microtubule-associated protein 2; nestin was expressed earlier than glial fibrillary acidic protein and microtubule-associated protein 2 expression. In addition, the number of NSE-positive cells was increased significantly more than glial fibrillary acidic protein-positive cells.CONCLUSION: Radix Astragafi promoted process formation in stem cells. It may induce the differentiation of MSCs into neural stem cells, and subsequently into neuronal- and glial-like cells.Radix Astragafi exhibits stronger inductive effect on neuronal differentiation than glial differentiation of MSCs.