Poster 136: Co-Expression of Nerve Growth Factor and p75NGFR in the Inferior Alveolar Nerve After Mandibular Distraction Osteogenesis

Abstract

During mandibular distraction osteogenesis (DO), the inferior alveolar nerve (IAN) can be damaged during the distractor activation period but can recover during the consolidation period. It is well known that many neurotrophins play important roles for this nerve recovery. However, there are few reports on the mechanism of peripheral nerve recovery after DO. Previously, we observed the expression pattern of the nerve growth factor (NGF) and vascular endothelial growth factor (VEGF) in the IAN after mandibular DO. The aim of this study was to examine the expression pattern of p75NGFR (low-affinity receptor of NGF) and the detection of the autocrine growth activity in the IAN after mandibular DO. Unilateral mandibular distractions (0.5 mm each, twice per day for 10 days) were performed on eight mongrel dogs. Two animals were sacrificed at 7, 14, 28, and 56 days after the distraction. The distracted IAN and contralateral control nerve were then harvested. Immunohistochemical staining was processed to observe the p75NGFR expression, and double immunofluorescent staining was processed to detect the co-expression of NGF and p75NGFR. The level of p75NGFR expression were significantly higher at 7 and 14 days after the distraction compared with the control. At these periods, p75NGFR was moderately expressed in the Schwann cells and distracted myelin. The level of p75NGFR expression decreased and was almost undetectable 28 and 56 days after distraction, respectively. The double immunofluorescent images revealed the co-expression of NGF and p75NGFR in the distracted IAN at 7 and 14 days after the distraction. p75NGFR plays an important role in the remodeling of IAN, and a distracted IAN might have autocrine growth activity during the early consolidation period of mandibular DO.