Distribution of neuropeptide on the vascularization or neurotization of large tissue-engineered bone

Objective To investigate the osteogenesis effects in vivo on the construction of vascularization and neurotization of large tissue-engineered bone and approach the distribution of neuropeptide initially. Methods Thirty-six New Zeland rabbits were divided into 3 groups randomly and equally: tissueengineering group ( A), vascular bundle group ( B, femoral vascular bundle), sensory nerve tract group ( C, saphenous nerves). A segmental bone defects of 1.5 cm long were made at the right femur in each animal. After plate fixation, the defect was implanted respectively with the engineered bone prepared by the 3methods mentioned above. Four, 8 and 12 weeks postoperatively, gross observation, X-ray observation and HE staining were adopted to evaluate the engineered bone and the new bone formation was measured by image analysis. The distribution of neuropeptide Y (NPY) and calcitonin gene related peptide (CGRP) in the new bone was detected by immunohistochemistryand analyzed semiquantitativly. Results After implantation of vascular bundle and sensory nerve into the tissue-engineered bone, the reparative effect was obviously better than the control group. New bone formation was gradually increased ( F = 105. 735, P ＜0. 01 ). The percentage of newly formed trabeculae in bone defect area at the 12th week was (48.67 ±4.21 ) %, (75.13 ± 5.75 ) %, (73.44 ± 2. 99) % in groups A, B and C, respectively. The effect of sensory nerve tract or vascular bundle implantation in osteogenesis have statistical significance ( F = 290. 008,P＜0. 01 ). The factorial design ANOVA showed time, sensory nerve tract and vascular bundle implantation had interaction (F=3. 177, P ＜ 0. 05 ). The formation of new bone in group B was increased as compared with that in group A and group C at the 4th week, that in group C was increased as compared with that in group A, and that in group B and group C was increased as compared with that in group A at 8th and 12th week. No obvious difference was found between group C and group B at the 8th and 12th week,The expression levels of NPY and CGRP in group B and group C were obviously higher than in group A at the three time points ( F = 30. 509 and 16. 475, P ＜ 0. 01 ). Conclusion Implantation of sensory nerve tract or vascular bundle into tissue-engineered bone can improve osteogenesis. Sprouting and secretion of neuropeptide by the implanted sensory nerve or vascular bundle may be the two possible mechanisms. Key words: Tissue engineering;  Bone;  Neuropeptide Y;  Calcitonin gene related peptide