LIPUS enhances SDF-1 expression in PDLSCs. (A) Effects of different intensities of LIPUS treatment on the mRNA expression and protein secretion of SDF-1, as measured by RT-qPCR and ELISA respectively. (B) Effects of AMD3100 antagonist on the mRNA expression and protein secretion of SDF-1, as measured by RT-qPCR and ELISA respectively. (C) mRNA expression of SDF-1 in different treatments. (D) SDF-1 secretion following blocking of SDF-1/CXCR4 signaling as demonstrated by ELISA. *P<0.05, **P<0.01, ***P<0.005 and ****P<0.001 vs. control group; ###P<0.005 and ####P<0.001 vs. LIPUS group. LIPUS, low-intensity pulsed ultrasound; SDF-1, stromal cell-derived factor-1; PDLSCs, periodontal ligament stem cells; RT-qPCR, reverse transcription-quantitative polymerase chain reaction; ns, not significant.