Objective      To investigate the distribution and significance of mammalian target of rapamycin (mTOR) during the differentiation of rat bone marrow mesenchymal stem cells (MSCs) into neurons.       Methods        Rat MSCs were cu

ltured by conventional method in vitro

and were induced by β-mercaptoethanol (β-ME) to differentiate into neurons. The MSCs were divided into a MSCs blank control group

a dimethyl sulfoxide (DMSO) negative control group

a β-ME induction group

different concentrations of rapamycin intervention groups

and different concentrations of rapamycin intervention + β-ME induction groups. Immunofluorescence and laser confocal microscopy were used to observe the intracellular distribution of mTOR before and after induction. Western blotting was used to detect the expression of neuron-related proteins and mTOR before and after induction.       Results      (1) Before β-ME induction

mTOR were mainly distributed in the cell nucleus like spots

and a small amount was distributed in the cytoplasm. After β-ME induction

the nuclear fluorescence signal reduced

and mTOR translocated into the cytoplasm. After rapamycin treatment

mTOR translocation to the cytoplasm became more obvious along with the increase of rapamycin concentration (10 to 30 μmol/L). When the concentration of rapamycin was more than 50 μmol/L

the morphology of MSCs became round

some cells detached

and the cell death rate was significantly increased (

P

0.05). (2) MSCs were induced by β-ME to differentiate into neurons and the expression of Tau and MAP-2 increased significantly. After rapamycin treatment

the expression of Tau and MAP-2 gradually increased along with the increase of rapamycin concentration (10 to 20 μmol/L). When the concentration reached 30 μmol/L

the expression of Tau and MAP-2 was down-regulated (

P

0.05). (3) Western blotting results suggested that the total expression of mTOR was the same before and after β-ME induction. The expression of phospho-mTOR

phospho-p70S6K and phospho-4EBP1 was significantly decreased after β-ME induction (

P

0.05)

and the decrease became more significant after rapamycin treatment (

P

0.05).       Conclusion      During the induction of MSCs differentiation into neurons

mTOR transloc

ated into cytoplasm from cell nucleus

and the expression of mTOR declines. mTOR may play an important role in regulating MSCs differentiation into neurons.