Demineralized Bone Scaffolds with Tunable Matrix Stiffness for Efficient Bone Integration

As a biophysical cue, matrix stiffness can decide the stem cell fate. However, most methods to construct three-dimensional (3D) scaffolds may change the 3D microstructure while altering their mechanical properties. In this study, demineralized bone matrix scaffolds with different compressive modulus (66.06 +/- 27.83 MPa (high), 26.90 +/- 13.16 MPa (medium), and 0.67 +/- 0.14 MPa (low)) were constructed by controlling the decalcification duration (1 h, 12 h, and 5 days), respectively. The pore size and porosity have no significant difference between the scaffolds before and after decalcification. Cell experiments indicated that the low scaffolds could promote the osteogenic differentiation of bone marrow mesenchymal stem cells (MSCs) in vitro. Rat subcutaneous implantation experiments further demonstrated that the low scaffolds could efficiently improve the cell infiltration, deposition of collagen fibers, and positive osteocalcin and osteopontin expression of endogenous cells as well as angiogenesis. Finally, rabbit femoral condylar defect experiments proved that the low scaffolds could significantly promote the bone repair and integration and stromal cell derived factor-1 alpha/CXC chemokine receptor signal pathway was essential for the stiffness-mediated bone repair. These investigations provided a novel method for fabricating 3D bone grafts with different stiffness, which is also of great significance for studying the effect of stiffness on the biological behavior of MSCs in three dimensions.