Objective: Vascular bundle and sensory nerve bundle implantation can promote the osteogenesis of tissue engineered bone. To investigate whether vascular bundle and sensory nerve bundle implantation will affect the expressions of neurokinin 1 receptor (NK1R) and vasoactive intestinal peptide type 1 receptor (VIPR1).
Methods: Fifty-four 5-month-old New Zealand rabbits were selected. Autologous bone marrow was aspirated from the posterior iliac spine of rabbits, and the bone marrow mesenchymal stem cells (BMSCs) were proliferated in vitro. At the 3rd passage, the BMSCs were cultured in the osteogenic culture medium for 7 days. The tissue engineered bone was prepared by the combined culture of these osteoblastic induced BMSCs and beta tricalcium phosphate scaffold material. A 1.5 cm segmental bone defect was created at the right femur of rabbits. After the plate fixation, defects were repaired with sensory nerve bundle plus tissue engineered bone (group A, n = 18), with vascular bundle plus tissue engineered bone (group B, n = 18), and tissue engineered bone only (group C, n = 18). X-ray examination was used to evaluate the degree of the ossification. The expression levels of NK1R and VIPR1 were measured by the immunohistochemistry analysis and the mRNA expression of NK1R and VIPR1 by real-time PCR at 4, 8, and 12 weeks after operation.
Results: The better osteogenesis could be observed in group A and group B than in group C at all time points. X-ray scores were significantly higher in group B than in groups A and C (P < 0.05) at 4 weeks, and in groups A and B than in group C (P < 0.05) at 8 and 12 weeks. The mRNA expressions of NK1R and VIPR1 were highest at 8 weeks in groups A and B and gradually decreased at 12 weeks (P < 0.05); the expressions were higher in groups A and B than that in group C (P < 0.05), and in group B than group A (P < 0.05). Immunohistochemistry analysis showed that the expressions of NK1R and VIPR1 were highest at 8 weeks in 3 groups, and the expressions were higher in groups A and B than in group C.
Conclusion: Implanting vascular bundles into the tissue engineered bone can significantly improve the expression levels of NK1R and VIPR1. It is an ideal method to reconstruct composite tissue engineered bone.