SDF-1 induces directional chemotaxis of BMSCs at the intervertebral fusion site and promotes osteogenic differentiation by regulating Wnt/β-catenin in the bone marrow chimera spinal intervertebral fusion mouse model

Clinical observations show that the current spinal fusion with internal fixation has a nonfusion rate of 5%–35%; however, methods to promote spinal fusion are limited. This study aimed to investigate the role of SDF-1-induced directional chemotaxis of BMSCs in bone marrow chimera spinal intervertebral fusion mouse model. BMSCs were isolated from bone marrow and identified by detecting CD44/CD34 positive cells. BMSCs (GFP-BMSCs) were labeled with GFP for tracking in vivo. Mice were inoculated with GFP-BMSCs to construct bone marrow chimera spinal intervertebral fusion model, which were divided into BM-SIF model, BM-SIF+SDF-1, BM-SIF+SDF-1-Anta group. The callus area of intervertebral fusion site was detected by radiology. HE staining was used to detect trabeculae formation. Expressions of osteogenic molecules and fibroblast markers were detected by RT-PCR and Western blotting. GFP-BMSCs showed obvious osteogenic and adipogenic differentiation ability, according to oil-red O and alizarin-red staining. Bone marrow chimera spinal intervertebral fusion mouse model was successfully established, with efficient localization of GFP-BMSCs at intervertebral fusion site. SDF-1 significantly promoted bone trabeculae formation in callus at intervertebral fusion site. SDF-1 significantly increased osteogenic molecules transcription/expression in callus at intervertebral bone graft fusion site of mice; however, SDF-1-Anta (AMD3100) significantly decreased osteogenic molecules transcrition/expression, compared to those of mice from the BM-SIF model group (p < 0.05). SDF-1 markedly induced and SDF-1-Anta significantly decreased fibroblast proliferations in the callus at the intervertebral fusion site of mice, compared to those of mice from the BM-SIF model group (p < 0.05). SDF-1 enhanced expression of Wnt10b and β-catenin in callus at intervertebral fusion site of mice compared to mice of the BM-SIF model group (p < 0.05). In conclusion, SDF-1 induced directional chemotaxis of BMSCs to the intervertebral fusion site and promoted osteogenic differentiation in bone marrow chimera spinal intervertebral fusion mice by regulating Wnt/β-catenin pathway and modulating the proliferation of BMSCs.