Immunomodulatory ECM-like Microspheres for Accelerated Bone Regeneration in Diabetes Mellitus

Bone repair and regeneration process is markedly impaired in diabetes mellitus (DM) that affects hundreds of millions of people worldwide. As a chronic inflammatory disease, DM creates a proinflammatory microenvironment in defective sites. Most of the studies on DM-associated bone regeneration, however, neglect the importance of immunomodulation under the DM condition and adopt the same approaches to normal bone healing, leading to limited bone healing. In this study, we developed a unique bioinspired injectable microsphere as an osteoimmunomodulatory biomaterial that modulates macrophages to create a prohealing microenvironment under the DM condition. The microsphere was self-assembled with heparin-modified gelatin nanofibers, and interleukin 4 (IL4) was incorporated into the nanofibrous heparin-modified gelatin microsphere (NHG-MS). IL4 has binding domains with heparin, and the binding of IL4 to heparin stabilizes this cytokine, protects it from denaturation and degradation, and subsequently prolongs its sustained release to modulate macrophage polarization. The IL4-loaded NHG-MS switched the proinflammatory M1 macrophage into a prohealing M2 phenotype, recovered the M2/M1 ratio to a normal level, efficiently resolved the inflammation, and ultimately enhanced osteoblastic differentiation and bone regeneration. The development of osteoimmunomodulatory biomaterials that harness the power of macrophages for immunomodulation, therefore, is a novel and promising strategy to enhance bone regeneration under DM condition

Additional file 3: Figure S2. of Intermittent parathyroid hormone (PTH) promotes cementogenesis and alleviates the catabolic effects of mechanical strain in cementoblasts

Bands of Fig. 4 (western blot analysis). (TIF 1478 kb

Additional file 4: Figure S3. of Intermittent parathyroid hormone (PTH) promotes cementogenesis and alleviates the catabolic effects of mechanical strain in cementoblasts

Bands of Fig. 7 (western blot analysis). (TIF 3040 kb

Additional file 2: Table S1. of Intermittent parathyroid hormone (PTH) promotes cementogenesis and alleviates the catabolic effects of mechanical strain in cementoblasts

Densitometry for the bands (western blot analysis) of 0, 1, 2 and 3 cycles of intermittent PTH and the corresponding control groups in Fig. 1a-b. Table S2. Densitometry for the bands (western blot analysis) of the control group, the strain group and the strain + PTH group in Fig. 1c-d. Table S3. Quantitative analysis of ALP activity. Data indicated the levels of the control group, 1, 2 and 3 cycles of intermittent PTH groups respectively in Fig. 3b. Table S4. Data of quantitative calcium assay of the control group and 3 cycles of intermittent PTH group in Fig. 3d. Table S5. Data indicating the mRNA levels of BSP, OCN, COL1 and Osx of 0, 1, 2 and 3 cycles of intermittent PTH and the corresponding groups in Fig. 4a-d. Table S6. Densitometry for the bands (western blot analysis) of the control group and 3 cycles of intermittent PTH in Fig. 4e-i. Table S7. Data indicating the mRNA levels of BSP, ALP, OCN, OPN, Runx2 and Osx of the control group and the strain group after 18 h of mechanical strain treatment in Fig. 6a-f. Table S8. Densitometry for the bands (western blot analysis) of the control group, the strain group and the strain + PTH group in Fig. 7a-g. Data were presented as mean ± SD. (DOCX 21 kb