Prolonged denervation induces remodeling of nasal mucosa in rat model of posterior nasal neurectomy

Background: The posterior nasal nerve is the dominant source of the parasympathetic, sympathetic, and sensory fibers that innervate the nasal respiratory mucosa. Therefore, a posterior nasal neurectomy (PNN) induces denervation of the nasal mucosa and relieves the nasal symptoms of intractable rhinitis. PNN depletes nerve fibers, choline acetyltransferase, and neuropeptides in nasal respiratory mucosa, and reduces nasal secretion. However, the histological and symptomatic changes over an extended period after PNN remain unknown. Methods: Using a rat model of PNN via the transorbital approach, we investigated chronological changes of nasal morphology, innervation, and secretion over a 48-week postoperative period after PNN. Results: The respiratory nasal mucosa exhibited squamous metaplasia, lymphocyte and plasma cell infiltration, basement membrane thickening, loss of cilia, and hyperplasia of the mucus gland in thickened epithelium with increased connective tissue from 24 weeks after PNN. These changes resemble the characteristics of remodeling in chronic rhinosinusitis. DNA microarray and quantitative polymerase chain reaction analysis revealed that mucin 5ac, interleukin 13, and brain-derived neurotrophic factor messenger RNA (mRNA) were upregulated in PNN-treated mucosa compared to untreated mucosa. During this period, nerve fibers including sensory, sympathetic, and parasympathetic fibers gradually reinnervated the mucosa from 12 weeks after PNN. However, nasal secretion was decreased even at 48 weeks after PNN probably due to the prolonged absence of choline acetyltransferase. Conclusion: Prolonged denervation induces remodeling of the nasal mucosa. Although the depleted nerves were partially reinnervated a few months after PNN, nasal secretion was still suppressed, partly due to a sustained deficiency of acetylcholine synthesis.