Squamous and Respiratory Metaplasia After Olfactory Mucosal Resection.

Eri Mori,Nobuyoshi Otori,Kai Kanemoto,Hironobu Nishijima,Hiromi Kojima,Rumi Ueha,Hajime Shimmura,Kenji Kondo,Shotaro Funada,Tatsuya Yamasoba,Hirotaka Tanaka

doi:10.3389/fnins.2021.695653

Abstract

Resection of the olfactory mucosa (OM) is sometimes unavoidable during surgery; however, it is not known whether the OM can completely recover thereafter. The aim of this study was to uncover whether the OM fully recovers after mucosal resection and describe the process of OM regeneration. 8-week-old male Sprague–Dawley rats (n = 18) were subjected to OM resection at the nasal septum; six rats were euthanized for histological examination 0, 30, and 90 days after surgery. Immunohistochemistry was performed to identify olfactory receptor neuron (ORN) lineage cells [mature and immature ORNs and ORN progenitors, and olfactory ensheathing cells (OECs)], as well as dividing and apoptotic cells. Squamous and respiratory metaplasia and inflammatory cell infiltration were also assessed. On day 30 after resection, the mucosa had regenerated, and mainly contained thin nerve bundles, basal cells, and immature ORNs, with a few mature ORNs and OECs. On day 90, the repaired nasal mucosa had degenerated into stratified squamous or ciliated pseudostratified columnar epithelia, with reducing ORNs. The lamina propria contained numerous macrophages. Partial regeneration was observed within 1 month after OM resection, whereas subsequent degeneration into squamous and respiratory epithelia occurred within 3 months. Given the poor persistence of ORNs and OECs, OM resection is likely to result in olfactory impairment. Overall, surgeons should be cautious not to injure the OM during surgery.

Highlights

Degeneration and subsequent regeneration of the olfactory epithelium (OE) have been reported to be associated with various inciting causes including drug abuse (Sakamoto et al, 2007), cigarette smoking (Kim et al, 2011; Ueha et al, 2016a), and chemical exposure (Cancalon, 1982; Ueha et al, 2016b); these studies have demonstrated that the OE can regenerate as long as the basal cells are preserved
In the rat model used in this study, the full thickness of the olfactory mucosa (OM) was removed, including the lamina propria (LP), basal cells, olfactory nerve bundles, and olfactory ensheathing cells (OECs), and the bones of nasal septum (NS) were exposed
Our results demonstrated that full-thickness excision of the OM was followed by regeneration of the nasal mucosa in the short term, it led to degeneration over time

Summary

Introduction

Degeneration and subsequent regeneration of the olfactory epithelium (OE) have been reported to be associated with various inciting causes including drug abuse (Sakamoto et al, 2007), cigarette smoking (Kim et al, 2011; Ueha et al, 2016a), and chemical exposure (Cancalon, 1982; Ueha et al, 2016b); these studies have demonstrated that the OE can regenerate as long as the basal cells are preserved. Endoscopic sinus surgery is employed as a standard treatment for nasal sinus diseases such as chronic rhinosinusitis and nasal tumors and as a surgical approach to reach the skull base. It is well-known that complications and olfactory disruption occur after nasal surgery (Pfaar et al, 2004; Alobid et al, 2013). The removal of lesions in the olfactory cleft (OC) aims to open the pathway to the olfactory mucosa (OM), thereby maximizing olfactory functional outcomes (Jiang and Liang, 2020) This removal of lesions in the OC (Hurtt et al, 1988; Delank and Stoll, 1998) or the approach of OM removal remains controversial because of the risk of iatrogenic hyposmia or anosmia secondary to OM damage. To develop better surgical options, it is necessary to confirm whether the OM can fully recover after surgical disruption

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