Pulp stem cells with hepatocyte growth factor overexpression exhibit dual effects in rheumatoid arthritis

Background To investigate the therapeutic effect of human dental pulp stem cells (DPSCs) transfected with adenovirus expressing hepatocyte growth factor (HGF) in a mouse model of collagen-induced arthritis (CIA). Methods DPSCs were modified with Ad-HGF to produce HGF-overexpressing DPSCs, DPSCs-HGF. In experimental mouse CIA model, DPSCs-HGF and DPSCs-Null (modified with Ad-Null) were engrafted via intravenously after disease onset, which was determined by the presence of joint swelling. The therapeutic effects on joints were evaluated at 49 days after collagen injection by histopathological analysis and microcomputed tomography imaging. The inflammatory cytokines were analyzed both in sera and joints via MILLIPLEX kit and immunohistochemical staining, respectively, and the regulatory T cells (Tregs) were analyzed in peripheral blood by using flow cytometry. Furthermore, primary fibroblast-like synoviocytes were isolated, colony formation analysis and FACS were performed to evaluate the effect of HGF on the proliferation and cell cycle of FLSs. Western blot assay was carried out to clarify the signal pathway of HGF-cMet. Results We found that without HGF modification, DPSC transfusion was helpful in controlling autoimmune status, local synovitis, and bone erosion after intravenous administration. However, HGF-modified DPSCs have dual role in rheumatoid arthritis (RA). In the early phase, HGF overexpression inhibited RA progression by its immunosuppressive effects, while in the late phase, HGF promoted synovitis by activating fibroblast-like synoviocytes to produce pathogenic IL-6, accelerating cell proliferation and inducing apoptosis resistance via phosphorylating the c-Met/Akt pathway. The overall effect of HGF modification attenuated the therapeutic effect of DPSCs. Conclusions Our study provides a comprehensive evaluation of the therapeutic effect of DPSCs in the mouse model and a primary answer to the divergence of whether HGF is harmful or helpful in RA.