Role of magnesium-doped calcium sulfate and ß-tricalcium phosphate composite ceramics in macrophage polarization and osteo-induction.

In the current study, we explored the role of Mg2+-doped CaSO4/ß-TCP composite biopolymer in regulating macrophage polarization and its relation with enhanced osteogenic differentiation of periodontal ligament stem cells. Furthermore, mechanism underling the regulation of macrophage polarization by CaSO4/ß-TCP was evaluated. Mg2+-doped CaSO4/ß-TCP composite was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Macrophage polarization was characterized using flow cytometry analysis. Macrophage morphometric analysis was conducted by FITC phalloidin staining. Western blot and qRT-PCR assays were used to assess gene expression levels and miRNAs, respectively. SEM morphology of CaSO4/ß-TCP ceramic revealed a particle size of 10-50 µm, and XRD spectrum showed that characteristic peak of samples was consistent with that of CaSO4 and ß-TCP. Results from flow cytometry evidenced significant upregulation of M2 macrophage markers after adding ceramic biopolymer, indicating the induction of inactivated M0 macrophage polarization to M2 macrophage. Macrophage morphometric analysis revealed development of lamellar pseudopodia on day 7 in CaSO4/ß-TCP group. Furthermore, flow cytometry revealed high positivity rate of 90.34% (CD44) and 89.36% (CD146). qRT-PCR results showed that the level of miR-21-5p was significantly decreased in M2 macrophages. Moreover, western blot analysis revealed upregulated expression levels of RUNX2, osterix (Osx), and osteopontin (OPN), and ELISA exhibited increase in cytokine levels (IL-1ß, IL-10, TGF-ß1, and BMP-2) in the presence of macrophages, indicating the osteogenic differentiation ability of periodontal ligament stem cells. The study evidenced the regulation of macrophage polarization by Mg2+-doped CaSO4/ß-TCP composite ceramic and its mediation through lncRNA PVT1/miR-21-5p/smad2 molecular axis.