Damage And Remodeling Study Of Nasal Epithelium In Radiation-induced Chronic Rhinosinusitis

Background and objectivesNasopharyngeal carcinoma(NPC)is one of the most common cancers in the head and neck region,and radiotherapy(RT)is the mainstay for its treatment.Radiation-induced chronic rhinosinusitis(CRSr)often arises as one of the most common side effects of RT in NPC patients,and seriously affects the quality of life of NPC patients due to the lack of effective treatment.Previous studies have found that the structure and function of nasal epithelium in patients with CRSr usually suffer extensive damage,and some patients can be secondary to irreversible epithelial remodeling such as squamous metaplasia(SM).The mechanism of epithelial damage and remodeling of CRSr is not fully clear,so it is impossible to develop an effective and precise treatment.This study aims to explore the damage and remodeling mechanisms of nasal epithelium in CRSr at mRNA and protein levels,so as to provide new ideas and theoretical basis for the pathogenesis of CRSr and lay the foundation for the further development of stem cell-mediated nasal epithelial regeneration therapy.MethodsThis study was divided into two parts.1.The biopsy samples of inferior turbinate(IT)and middle turbinate(MT)from 39 patients with CRSr and IT biopsies from 26 healthy controls were collected.Optical microscopy and transmission electron microscopy(TEM)were used to evaluate the morphology and ultrastructure of nasal epithelium.RT-qPCR and immunofluorescence staining were used to evaluate and compare the expression of ciliary structure markers,ciliary formation markers and goblet cell markers in nasal epithelium of the two groups.2.Inferior turbinate biopsies were collected from 28 healthy controls,33 patients with chronic sinusitis without nasal polyps(CRSsNP)and 36 patients with CRSr.The remodeling of nasal epithelium was evaluated by optical microscopy,and the differentiation and proliferation of stem cells in nasal epithelium were evaluated and compared among groups by immunofluorescence staining and RT-qPCR.Results1.The nasal epithelium of CRSr patients showed epithelial shedding,loose arrangement,increased intercellular spaces,and decreased cilia intensity.Compared with healthy controls,the mRNA expression levels of ciliary structural markers(Tubulin,DNAH5 and RSPH4A),ciliogenesis markers(FOXJ1 and CP110),and goblet cell markers(MUC5AC and MUC5B)in the nasal epithelium of CRSr patients were all significantly decreased.The protein expression levels of Tubulin(ciliary structural marker),FOXJ1(ciliogenesis marker)and MUC5AC(goblet cell marker)were also significantly downregulated.In addition,there was no significant relationship between the down-regulation of nasal epithelium related markers and duration of radiotherapy in CRSr patients.2.Compared with healthy controls and CRSsNP patients,the incidence of squamous metaplasia(SM)and the number of p63+krt5+basal cells in nasal epithelium of CRSr patients increased,accompanied by the decrease of ciliated cells and goblet cells.The number of Ki67+cells in CRSr patients and CRSsNP patients were significantly higher than that in the control group.The ratio of Ki67+cells/p63+krt5+cells in CRSr patients was significantly lower than that in CRSsNP patients.In CRSr patients,the number of p63+krt5+basal cells in SM epithelium were higher than that in non-SM epithelium,and the ratio of p63+cells/krt5+cells in SM epithelium was significantly decreased.ConclusionRT can lead to long-term damage of nasal epithelial structure and function,which is the main reason of persistent clinical symptoms of CRSr.SM is more likely to occur in the radiation-induced nasal epithelium.The abnormal proliferation of p63+krt5+basal cells is an important histological feature of SM.The abnormal proliferation of basal cells may be an important pathological mechanism of SM in nasal epithelium of CRSr patients.