Combination of Heel-strike like Mechanical Loading with Deproteinized Cancellous Bone Scaffold Implantation to Repair Segmental Bone Defects in Rabbits

Combination of optimized tissue engineering bone implantation with heel-strike like mechanical loading to repair segmental bone defect in New Zealand rabbits

In this study, effects of combining optimized tissue engineering bone (TEB) implantation with heel-strike like mechanical loading to repair segmental bone defect in New Zealand rabbits were investigated. Physiological characteristics of bone marrow mesenchymal stem cells (BMMSCs), compact bone cells (CBCs), and bone marrow and compact bone coculture cells (BMMSC-CBCs) were compared to select the optimal seed cells for optimized TEB construction. Rabbits with segmental bone defects were treated in different ways (cancellous bone scaffold for group A, cancellous bone scaffold and mechanical loading for group B, optimized TEB for group C, optimized TEB and mechanical loading for group D, n = 4), and the bone repair were compared. BMMSC-CBCs showed better proliferation capacity than CBCs (p < 0.01) and stronger osteogenic differentiation ability than BMMSCs (p < 0.05). Heel-strike like mechanical loading improved proliferation and osteogenic differentiation ability and expression levels of TGFβ1 as well as BMP2 of seed cells in vitro (p < 0.05). At week 12 post-operation, group D showed the best bone repair, followed by groups B and C, while group A finished last (p < 0.05). During week 4 to 12 post-operation, group D peaked in terms of expression levels of TGFβ1, BMP2, and OCN, followed by groups B and C, while group A finished last (p < 0.05). Thus, BMMSC-CBCs showed good proliferation and osteogenic differentiation ability, and they were thought to be better as seed cells than BMMSCs and CBCs. The optimized TEB implantation combined with heel-strike like mechanical loading had a synergistic effect on bone defect healing, and enhanced expression of TGFβ1 and BMP2 played an important role in this process.

Design of two natural deproteinized bovine bone scaffolds and evaluation of the effect of initial cell seeding density on repairing bone defects

Engineering functional bone using combinations of cells, scaffolds, and bioactive factors is a promising strategy for the bone-tissue regeneration, while challenge remains. Chemical methods deproteinizing natural bovine cancellous bone to remove immunogenic are poorly understood, and the cell seeding density to promote bone formation still needs to be clarified. In this study, 8.0 × 8.0 × 2.0 mm bovine cancellous bones were either treated with H₂ O₂ for 8 hr or pepsin for 24 hr and then inoculated with MC3T3-E1 osteoblasts with two cell densities (1 × 10⁶ cells/ml or 4 × 10⁶ cells/ml)separately. We compared the appearance of the bones treated by the two chemical deproteinizing methods, as well as the proliferation ability of the inoculating cell density at 1 × 10⁶ cells/ml. Moreover, scanning electron microscopy was done to analyze the growth of cells on the surface of the material, and an alkaline phosphatase assay was performed to assess osteogenic differentiation. We showed that both treated bones treatments are biocompatible, but bones treated with H₂ O₂ were more conducive to osteoblast differentiation and ALP secretion, especially when seeded at the higher cell density at 4 × 10⁶ cells/ml. We concluded that chemical deproteinized bovine cancellous bones met the basic bone graft material requirements. Cell seeding density is an important factor to promote the material's osteogenic ability, with H₂ O₂ -deproteinized bones exhibiting enhanced osteoblast differentiation.