KLF5 modulates proliferation and osteogenic differentiation of human periodontal ligament cells subjected to cyclic tensile stress

PURPOSE: To investigate the expression of Kruppel-like factor 5 (KLF5) in human periodontal ligament cells (hPDLCs) under cyclic tensile stress (CTS) and its effect on proliferation and osteogenic differentiation of hPDLCs. METHODS: hPDLCs were primarily cultured in vitro by tissue explant and enzyme digestion method. RT-PCR and Western blot were used to detect mRNA and protein expression of KLF5 in hPDLCs stimulated by 10% CTS at a frequency of 0.5 Hz for 1, 4, 8, 12 and 24 h, respectively．KLF5 was then knocked-down in hPDLCs using siRNA (si-KLF5) and its mRNA expression was determined by RT-PCR. Meanwhile, basic fibroblast growth factor (FGF2) was overexpressed in KLF-5 silenced hPDLCs by using pcDNA3.1-FGF2. After stimulation with CTS for 8 h, the proliferation of hPDLCs was assayed by CCK-8 kit, alkaline phosphatase (ALP) activity was assayed by ALP kit, the mRNA expression of Runx2 and Osterix was examined by RT-PCR, and the protein expression of Runx2, Osterix, FGF2, GSK-3β, P-GSK-3β (ser 9), β-catenin was determined by Western blot. The data were analyzed using SPSS 22.0 software package. RESULTS: Stimulation with 10% CTS time-dependently induced mRNA and protein expression of KLF5 in hPDLCs. Transfection of si-KLF5 significantly reduced the proliferation of hPDLCs, decreased ALP activity and expression of Runx2 and Osterix in hPDLCs stimulated by 10% CTS. Simultaneously, CTS-induced activation of FGF2-GSK-3β/β-catenin signaling pathway was also inhibited by si-KLF5 transfection. However, overexpression of FGF2 can partly neutralized the inhibitiory effect of si-KLF5 on proliferation and osteogenic differentiation of hPDLCs subjected to 10% CTS. CONCLUSIONS: KLF5 promotes proliferation and osteogenesis differentiation of hPDLCs subjected to cyclic tensile stress through FGF2-GSK-3β/β-catenin signaling pathway.