BACKGROUND: SSh as a Hedgehog signal protein can promote bone development, growth and remodeling.OBJECTIVE: To investigate the effect of bone marrow mesenchymal stem cells (BMSCs) combined with Shh modified nano-hydroxyapatite/collagen (nHAC) in the repair of femoral defects in rats.METHODS: Forty-eight Sprague-Dawley rats were randomly divided into four groups, and the model of femoral defects was established in these rats. At 14 days after modeling, experimental group was implanted with the BMSCs/Shh modified nHAC, scaffold group was implanted with simple nHAC, cell scaffold group was implanted with BMSCs/nHAC,and blank control group was without any implantation. At 3, 6, 9, 12 weeks after repair, X-ray examination, bone density measurement and bone biopsy in bone defect area were performed.RESULTS AND CONCLUSION: (1) X-ray examination: The Lane-Sandhu X-ray score and bone mineral density value in the experimental group at different time points after operation were significantly higher than those in the other three groups (P < 0.05). (2) Hematoxylin-eosin staining: 12 weeks after repair, a small amount of bone tissues but no bone marrow formed in the scaffold group; a small amount of bone tissues with absence of bone marrow formed in the cell scaffold group, and the residual scaffold was visible; in the experimental group, the scaffold was completely absorbed,and mature bone and medullary cavity formed with presence of bone marrow. (3) Scanning electron microscope observation: 12 weeks after repair, irregular arrangement of bone fibers and a large number of bone fossae were observed in the scaffold group; the cell scaffold group showed a large number of osteoblasts, but bone fibers still arranged irregularly; in the presence of the Haversian system, a large number of regularly arranged bone trabeculae were detective in the experimental group. These results elucidate that the Shh modified nHAC/BMSCs complex can promote the repair of bone defects.

BACKGROUND: Polylactic acid copolymer bone scaffold has excellent biodegradability, and it is easy to be shaped and can promote the formation and growth of bone tissue and blood vessel.OBJECTIVE: To observe the effects of adipose-derived stem cells(ADSCs)/poly(lactic-co-glycolic acid) (PLGA) complex on the biomechanical properties after fracture healing in osteoporotic bone.METHODS: Sixty Sprague-Dawley rats were randomly divided into four groups: blank control group received no treatment; the bilateral tibial fracture model was made after 3 months of bilateral ovarian resection in model group; the bilateral tibial fracture model was made and ADSCs were implanted into the bone after 3 months of bilateral ovarian resection in cell therapy group; the bilateral tibial fracture model was made and the PLGA/ADSCs complex was implanted after 3 months of bilateral ovarian resection in combined treatment group.The bone mineral density, callus thickness, biomechanical parameters and the microstructure of the trabecular bone were detected.RESULTS AND CONCLUSION: (1) The bone density: The bone density of the model group was significantly lower than that of the blank control group (P < 0.05); the bone mineral density of the cell therapy group and the combined treatment group was higher than that of the model group (P < 0.05), but lower than that of the control group (P < 0.05); and the bone mineral density of the combination treatment group was higher than that of the cell therapy group (P < 0.05). (2)Thickness of the callus: The thickness of the callus in the cell therapy group and combined treatment group was higher than that of the model group and blank control group (P < 0.05); moreover, the thickness of the callus in the combined treatment group was higher than that of the cell therapy group (P < 0.05). (3) Biomechanical test: The failure load, stress and shear strength, elastic modulus were decreased in the model group compared with the blank control group (P < 0.05), while the shear strain increased (P < 0.05). Compared with the model group, the failure load, ultimate stress, shear strength, elastic modulus were increased in the cell therapy group and combined treatment group (P < 0.05), and the shear strain was decreased (P < 0.05). Moreover, the combined treatment group showed more changes in these biomechanical parameters (P < 0.05). (4) The trabecular bone microstructure: The model group presented with trabecular derangement, spacing increases, and even fracture and lacuna. After ADSCs or ADSCs/PLGA transplantation,the trabecular bones increased in number, thickness, and spacing, and the number of lacunae reduced. In conclusion,ADSCs combined with PLGA in the treatment of osteoporotic fracture can significantly improve the biomechanical parameters of bone tissue after healing.