Figure 2.

Varying the composition (HA vs. TCP) and size of CaP particles (micro vs. nano) modulates Mφ polarization, and the corresponding effect of Mφ conditioned medium on MSC osteogenesis. Tricalcium phosphate microparticle (mTCP) was identified as the lead formulation, which promotes M2 Mφ polarization and enhances MSC-based bone formation in the presence of conditioned medium from Mφ. (A) Schematics of experimental design. (B-C) Normalized gene expression of Mφ M1 (B) and M2 markers (C); (D-E) Quantification of TNF-α (D) and IL-10 (E) secreted by Mφ at 18 hr using ELISA. (F) Schematic of conditioned medium (CM) treatment on MSC osteogenesis and bone formation. (G) MSC osteogenic gene expression was evaluated at day 7 after encapsulation in CaP-μRB scaffolds with or without treatment of conditioned medium (CM) from Mφ cultured in the same CaP-μRB formulation. (H, I) Representative OCN staining (H), and OCN area quantification with or without Mφ CM treatment (I). Scale bar: 100 μm. Data are represented as mean ± S.D. (n = 3~4/group). *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. ns indicates not significant. & indicates comparison of mTCP with other groups, &P < 0.0001.