Effect of SHP2 knockdown on the proliferation and osteogenic differentiation of human periodontal ligament stem cells under inflammatory environment

The purpose of this study was to clarify the regulatory effect and mechanism of Src homology-2 domain containing protein tyrosine phosphatase-2 (SHP2) on human periodontal ligament stem cell (hPDLSC) proliferation and osteogenic differentiation under inflammatory environment and to provide a new target for the treatment of periodontitis.

SHP2 was knocked down in hPDLSCs, and the transfection efficiency of SHP2 was detected by RT–qPCR and Western blot. An in vitro inflammatory environment was created using tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). The effect of SHP2 knockdown on hPDLSC viability under normal and inflammatory conditions was detected by CCK-8, and the osteogenic capacity of hPDLSCs under normal and inflammatory conditions was detected by ALP staining, ALP activity, ARS staining, RT–qPCR and Western blot. The mechanism by which SHP2 knockdown affected the MAPK pathway and its downstream NF-κB pathway under inflammatory conditions was assessed by Western blot.

Green fluorescence was observed after transfection for 72 h, and the titer of SHP2 shRNA recombinant lentivirus was 2.9×10⁸ TU/mL. SHP2 expression was significantly downregulated in lentivirus-transfected cells, as demonstrated by Western blot and RT–qPCR (P<0.001). SHP2 knockdown inhibited hPDLSC proliferation to a certain extent and increased the expression of early osteogenic markers under normal conditions, including increased ALP activity and increased ALP and COL-1 expression (P<0.05). However, SHP2 knockdown exerted no effect on mineralized nodule formation. In the TNF-α- and IL-1β-induced inflammatory environment, SHP2 knockdown exerted no effect on hPDLSC proliferation (P>0.05). Osteogenic markers were upregulated (P<0.05), and mineralized nodules were significantly increased (P<0.05) after SHP2 knockdown. Western blot analysis showed that p65 phosphorylation and IκB-α degradation were reduced in SHP2-knockdown hPDLSCs in the inflammatory environment. Moreover, SHP2 knockdown significantly inhibited the expression of p-p38 and p-JNK MAPK, which represent pathways upstream of the NF-κB pathway (P<0.05).

SHP2 knockdown did not affect cell viability but promoted the osteogenic potential of hPDLSCs by inhibiting the MAPK/NF-κB-mediated signaling pathway under inflammatory environment.