['To test the hypothesis that psoralen induces rat mesenchymal stem cells (RMSCs) to differentiate towards male germ cells.', 'RMSCs were induced by psoralen at the final concentration of 3.0 µg/ml, and the morphological changes of the cells were detected microscopically and the cell proliferation changes were measured by MTT assay. The expressions of 7 representative marker genes of male germ cells, namely Oct-4, Stra8, RVLG, SCP3, TNP2, Itgb1, and Itga6, were investigated in the induced cells by real-time quantitative PCR.', 'RMSCs showed no obvious morphological changes after induction with 3.0 µg/ml psoralen for 72 h. Psoralen induction for 5 days did not significantly affect the proliferation of RMSCs; Psoralen induction for 72 h, however, significantly up-regulated the genes Oct-4, Stra8, SCP3, and Itgb1 (P<0.05) without affecting the expressions of the genes RVLG, TNP2, or Itga6 (P>0.05).'] Does [ Psoralen induce rat mesenchymal stem cell differentiation towards male germ cells in vitro ]?