Temporal and spatial expression pattern of VEGF and VEGF receptor in the posterior spinal fusion with allograft

The role of VEGF and its receptor in spinal fusion with allograft was elucidated by immunohistochemistry method. The allograft was implanted on L5 and L6 transverse process bilaterally in rabbit spinal fusion model. After harvesting at week 3, 5 and 7, the samples were prepared for sectioning and then performed immunohistochemistry of VEGF and VEGFR-2. During spinal fusion at week 3, expression of VEGF was found in osteoblast near the mineralisation front and cartilaginous tissue of spinal processes. Later at week 5, The VEGF expressed moderately in osteoblast and mesenchymal stem cells between intertransverse processes fusion bed. The active bone formation was observed and the spinal processes grew closer. In the complete spinal fusion at week 7, VEGF was expressed less in osteoblast. The expression of VEGF receptor-2 at fusion bed was very week and found in blood vessel cells among week 3 and week 5 but not at week 7. The expression of VEGF in the early stage of spinal fusion was clearly demonstrated, especially for the neovascularisation in the spinal fusion process. Application of exogenous VEGF may further enhance the spinal fusion and is worth further investigation.