Dental Pulp Mesenchymal Stem Cells Promote Polarization of M2 Macrophages and Accelerate Wound Healing by Secreting CCL2

Abstract

Background Mesenchymal stem cells (MSCs) are widely used in tissue engineering owing to their regenerative potential and immunomodulatory capacity. The crosstalk between MSCs and the host immune function plays a key role in the efficiency of tissue regeneration. However, the difference in immunological modulation and tissue regeneration function between MSCs from different sources remains unclear. Methods Human mesenchymal stem cells derived from bone marrow (BMMSCs), periodontal ligament (PDLSCs), adipose (ADSCs), and dental pulp (DPSCs) were obtained and induced to form cell sheets under the condition of 20 ug/ml vitamin C. The MSC cell sheets carried by hydroxyapatite/tricalciumphosphate (HA/TCP) particles were transplanted subcutaneously into C57BL6 mice for 8 weeks. Histological analyses were performed to detect the tissue regeneration potential and macrophages polarization in vivo. Then, THP-1 macrophages were co-cultured with MSCs and quantitative real-time polymerase chain reaction, immunofluorescent staining, western blotting, and enzyme-linked immunosorbent assay were used to investigate the function and mechanism of MSCs on macrophages in vitro. Finally, a wound healing model of the palatal mucosa was performed to confirm the effect of MSCs on macrophages and tissue healing efficiency. Results Compared to PDLSCs, BMMSCs, and ADSCs, DPSCs exhibited greater tissue regeneration potential, with greater tissue volume, higher Ki67 expression, and less apoptosis in the regenerated tissue of wild-type C57BL6 mice. In addition, DSPCs triggered more M2 macrophages in the regenerated tissue than other MSCs. Our data showed that DPSCs exhibited higher expression levels of C-C Motif Chemokine Ligand 2 (CCL2), and specific blocking of CCL2 by neutralising antibodies can significantly inhibit the DPSCs-induced polarization of M2 macrophages. Finally, DPSCs transplantation promoted wound healing of the palatal mucosa and M2 macrophages polarization in vivo, which could be significantly impaired by CCL2 neutralising antibody. Conclusions Our data indicate that DPSCs exert better tissue regeneration potential and immunoregulatory function by secreting CCL2. These results suggest that CCL2 application can enhance MSC-mediated tissue regeneration or wound healing.