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We previously showed that the repair of bone defects is regulated by neural and vascular signals. In the present study, we examined the effect of topically appliedβ-nerve growth factor (β-NGF) on neurogenesis and angiogenesis in critical-sized bone defects iflled with collagen bone substi-tute. We created two symmetrical defects, 2.5 mm in diameter, on either side of the parietal bone of the skull, and filled them with bone substitute. Subcutaneously implanted osmotic pumps were used to infuse 10 μgβ-NGF in PBS (β-NGF + PBS) into the right-hand side defect, and PBS into the left (control) defect, over the 7 days following surgery. Immunohistochemical staining and hematoxylin-eosin staining were carried out at 3, 7, 14, 21 and 28 days postoperatively. On day 7, expression of β III-tubulin was lower on theβ-NGF + PBS side than on the control side, and that of neuroiflament 160 was greater. On day 14,β III-tubulin and protein gene product 9.5 were greater on theβ-NGF + PBS side than on the control side. Vascular endothelial growth factor expression was greater on the experimental side than the control side at 7 days, and vascular endothelial growth factor receptor 2 expression was elevated on days 14 and 21, but lower than control levels on day 28. However, no difference in the number of blood vessels was observed between sides. Our results indicate that topical application ofβ-NGF promoted neu-rogenesis, and may modulate angiogenesis by promoting nerve regeneration in collagen bone substitute-iflled defects.
