3D Scaffolds with Different Stiffness but the Same Microstructure for Bone Tissue Engineering

Abstract

A growing body of evidence has shown that extracellular matrix (ECM) stiffness can modulate stem cell adhesion, proliferation, migration, differentiation, and signaling. Stem cells can feel and respond sensitively to the mechanical microenvironment of the ECM. However, most studies have focused on classical two-dimensional (2D) or quasi-three-dimensional environments, which cannot represent the real situation in vivo. Furthermore, most of the current methods used to generate different mechanical properties invariably change the fundamental structural properties of the scaffolds (such as morphology, porosity, pore size, and pore interconnectivity). In this study, we have developed novel three-dimensional (3D) scaffolds with different degrees of stiffness but the same 3D microstructure that was maintained by using decellularized cancellous bone. Mixtures of collagen and hydroxyapatite [HA: Ca10(PO4)6(OH)2] with different proportions were coated on decellularized cancellous bone to vary the stiffness (local stiffness, 13.00 ± 5.55 kPa, 13.87 ± 1.51 kPa, and 37.7 ± 19.6 kPa; bulk stiffness, 6.74 ± 1.16 kPa, 8.82 ± 2.12 kPa, and 23.61 ± 8.06 kPa). Microcomputed tomography (μ-CT) assay proved that there was no statistically significant difference in the architecture of the scaffolds before or after coating. Cell viability, osteogenic differentiation, cell recruitment, and angiogenesis were determined to characterize the scaffolds and evaluate their biological responses in vitro and in vivo. The in vitro results indicate that the scaffolds developed in this study could sustain adhesion and growth of rat mesenchymal stem cells (MSCs) and promote their osteogenic differentiation. The in vivo results further demonstrated that these scaffolds could help to recruit MSCs from subcutaneous tissue, induce them to differentiate into osteoblasts, and provide the 3D environment for angiogenesis. These findings showed that the method we developed can build scaffolds with tunable mechanical properties almost without variation in 3D microstructure. These preparations not only can provide a cell-free scaffold with optimal matrix stiffness to enhance osteogenic differentiation, cell recruitment, and angiogenesis in bone tissue engineering but also have significant implications for studies on the effects of matrix stiffness on stem cell differentiation in 3D environments.

Matrix elasticity-modified scaffold loaded with SDF-1α improves the in situ regeneration of segmental bone defect in rabbit radius

“…Decellularized bone can avoid this mismatch and has natural porous microstructure and 3D interconnectivity, which are beneficial to migration and infiltration of endogenous stem cells. In our previous study 15 , novel 3D scaffolds with different matrix elastic modulus (6.74 ± 1.16 kPa, 8.82 ± 2.12 kPa, and 23.61 ± 8.06 kPa) but same microstructure have been successfully fabricated by coating decellularized bone with collagen (Col)/hydroxyapatite (HA) mixture in different collagen ratios. Our study has proved that the scaffold with optimal matrix elastic modulus (23.61 ± 8.06 kPa) can promote the osteogenic differentiation of MSCs in vitro and enhance the new bone formation in vivo .…”

From the Clinical Problem to the Basic Research—Co-Culture Models of Osteoblasts and Osteoclasts

“…An important parameter is the pore size. The average pore diameter of the decellularized cancellous bone is in a range of 389.3 ± 134.9 μm [92]. Several studies have shown that a pore size between 300 and 500 μM is necessary for the adhesion, differentiation and growth of osteoblasts [93,94].…”

Novel biomaterials to study neural stem cell mechanobiology and improve cell-replacement therapies

“…Although increased physical protection and the presence of an adherent substrate are likely at least partially responsible for the improved performance of scaffold-supported cellular transplants in this study, its findings indicate that maintaining the proper biomechanical context may be an important factor for successful cell- based therapy in the CNS. Indeed, other studies have demonstrated that the stiffness of 3D scaffolds can influence stem cell behavior [65, 66]. …”