Airway hillocks are injury-resistant reservoirs of unique plastic stem cells.

Airway hillocks are stratified epithelial structures of unknown function1. Hillocks persist for months and have a unique population of basal stem cells that express genes associated with barrier function and cell adhesion. Hillock basal stem cells continually replenish overlying squamous barrier cells. They exhibit dramatically higher turnover than the abundant, largely quiescent classic pseudostratified airway epithelium. Hillocks resist a remarkably broad spectrum of injuries, including toxins, infection, acid and physical injury because hillock squamous cells shield underlying hillock basal stem cells from injury. Hillock basal stem cells are capable of massive clonal expansion that is sufficient to resurface denuded airway, and eventually regenerate normal airway epithelium with each of its six component cell types. Hillock basal stem cells preferentially stratify and keratinize in the setting of retinoic acid signalling inhibition, a known cause of squamous metaplasia2,3. Here we show that mouse hillock expansion is the cause of vitamin A deficiency-induced squamous metaplasia. Finally, we identify human hillocks whose basal stem cells generate functional squamous barrier structures in culture. The existence of hillocks reframes our understanding of airway epithelial regeneration. Furthermore, we show that hillocks are one origin of 'squamous metaplasia', which is long thought to be a precursor of lung cancer.

Spatiotemporal dynamics exhibited by horizontal basal cells reveal a pro-neurogenic pathway during injury-induced olfactory epithelium regeneration.

Horizontal basal cells (HBCs) mediate olfactory epithelium (OE) regeneration following severe tissue injury. The dynamism of the post-injury environment is well illustrated by in silico modeling of RNA sequencing data that demonstrate an evolving HBC transcriptome. Unfortunately, spatiotemporally dynamic processes occurring within HBCs in situ remain poorly understood. Here, we show that HBCs at 24 h post-OE injury spatially redistribute a constellation of proteins, which, in turn, helped to nominate Rac1 as a regulator of HBC differentiation during OE regeneration. Using our primary culture model to activate HBCs pharmacologically, we demonstrate that concurrent Rac1 inhibition attenuates HBC differentiation potential. This in vitro functional impairment manifested in vivo as decreased HBC differentiation into olfactory sensory neurons following HBC-specific Rac1 conditional knockout. Taken together, our data potentiate the design of hyposmia-alleviating therapies and highlight aspects of in situ HBC spatiotemporal dynamics that deserve further investigation.

Pronounced Olfactory Habituation with Age.

OBJECTIVES: Olfactory habituation is a transient decrease in olfactory sensitivity caused by prolonged odor exposure, aiding in the discernment of new olfactory stimuli against the background. We explored the impact of subclinical olfactory impairment on odor habituation using age as a proxy. METHODS: Before the actual experiment, the individual olfactory threshold for the rose-like odorant phenylethyl alcohol (PEA) was assessed separately for the left and right nostril using the "Sniffin' Sticks" test, and ratings for odor intensity and pleasantness were collected. After applying a nasal clip continuously delivering PEA odor to one nostril for 10 min and 2 h, respectively, threshold, intensity, and pleasantness were reassessed immediately after clip removal. RESULTS: In the group of 80 participants (younger adults-mean age 27.7 ± 4.5 years; older adults-mean age 61.5 ± 4.7 years), olfactory thresholds were already significantly elevated after just 10 min, and this habituation was even more pronounced after 2 h. This effect could be observed bilaterally even though significantly more distinct on the exposed side. Older participants generally exhibited a more pronounced habituation on the exposed side after 2 h compared to the younger participants. CONCLUSION: The results indicate that older people experience more notable habituation after extended exposure to odors. This is most likely due to the compromised olfactory function in age. Although older and younger subjects scored in the normosmic range when tested with standardized olfactory tests, the stress on the system after exposure to an odor clearly revealed the lower functionality of the aging sense of smell. LEVEL OF EVIDENCE: 3 Laryngoscope, 2024.

Monitoring mepolizumab treatment in chronic rhinosinusitis with nasal polyps (CRSwNP): Discontinue, change, continue therapy?

BACKGROUND: Chronic rhinosinusitis with nasal polyps (CRSwNP) is a multifactorial inflammatory disease of the mucous membranes of the nose and sinuses. Eosinophilic inflammation is described as a common endotype. The anti-IL-5 antibody mepolizumab was approved in November 2021 as an add-on therapy to intranasal glucocorticosteroids for the treatment of adults with severe chronic rhinosinusitis with nasal polyps when systemic glucocorticosteroids or surgery do not provide adequate disease control. While national and international recommendations exist for the use of mepolizumab in CRSwNP, it has not yet been adequately specified how this therapy should be monitored, what follow-up documentation is necessary, and when it should be discontinued if necessary. MATERIALS AND METHODS: A literature search was performed to analyze previous data on the treatment of CRSwNP with mepolizumab and to determine the available evidence by searching Medline, Pubmed, the national and international trial and guideline registries, and the Cochrane Library. Human studies published in the period up to and including 10/2022 were considered. RESULTS: Based on the international literature and previous experience by an expert panel, recommendations for follow-up, adherence to therapy intervals, and possible therapy breaks as well as discontinuation of therapy when using mepolizumab for the indication CRSwNP in the German healthcare system are given on the basis of a documentation sheet. CONCLUSION: Understanding the immunological basis of CRSwNP opens up new non-surgical therapeutic approaches with biologics for patients with severe, uncontrolled courses. Here, we provide recommendations for follow-up, adherence to therapy intervals, possible therapy pauses, or discontinuation of therapy when mepolizumab is used as add-on therapy with intranasal glucocorticosteroids to treat adult patients with severe CRSwNP that cannot be adequately controlled with systemic glucocorticosteroids and/or surgical intervention.

Effect of hypoglossal nerve stimulation on snoring: an evaluation using objective acoustic parameters.

STUDY OBJECTIVES: Hypoglossal nerve stimulation is an established therapy for sleep apnea syndrome. Whether or not this therapy on snoring and nighttime noise exposure is effective and how strong this effect may be has not been objectively investigated thus far and was the aim of this study. METHODS: In 15 participants (14 males; age: 30-72 years; mean: 51.7 years), polysomnography and acoustic measurements were performed before and after hypoglossal nerve stimulation. RESULTS: The therapy led to a significant improvement in sleep apnea (apnea-hypopnea index from 35.8 events/h to 11.2 events/h, P < .001). Acoustic parameters showed a highly significant reduction in the average sound pressure level (42.9 db[A] to 36.4 db[A], P < .001), averaged sound energy, A-weighted (LAeq; 33.1 db[A] to 28.7 db[A], P < .001), snoring index (1,068 to 506, P < .001), percentage snoring time (29.7-14.1%, P < .001), and psychoacoustic snore score, the latter being a measure of annoyance due to snoring (47.9 to 24.5, P < .001). CONCLUSIONS: This study was able to show for the first time by means of objective acoustic and psychoacoustic parameters that hypoglossal nerve stimulation can not only cause a significant improvement in sleep apnea but also has a positive effect on snoring and thus noise annoyance experienced by the bed partner. CLINICAL TRIAL REGISTRATION: Registry: German Clinical Trials Register; Name: Effect of Hypoglossal Nerve Stimulation on Snoring: An Evaluation Using Objective Acoustic Parameters; URL: https://drks.de/search/de/trial/DRKS00032354; Identifier: DRKS00032354. CITATION: Fischer R, Vielsmeier V, Kuehnel TS, et al. Effect of hypoglossal nerve stimulation on snoring: an evaluation using objective acoustic parameters. J Clin Sleep Med. 2024;20(3):363-370.

Targeting the microenvironment in the treatment of arteriovenous malformations.

Extracranial arteriovenous malformations (AVMs) are regarded as rare diseases and are prone to complications such as pain, bleeding, relentless growth, and high volume of shunted blood. Due to the high vascular pressure endothelial cells of AVMs are exposed to mechanical stress. To control symptoms and lesion growth pharmacological treatment strategies are urgently needed in addition to surgery and interventional radiology. AVM cells were isolated from three patients and exposed to cyclic mechanical stretching for 24 h. Thalidomide and bevacizumab, both VEGF inhibitors, were tested for their ability to prevent the formation of circular networks and proliferation of CD31+ endothelial AVM cells. Furthermore, the effect of thalidomide and bevacizumab on stretched endothelial AVM cells was evaluated. In response to mechanical stress, VEGF gene and protein expression increased in patient AVM endothelial cells. Thalidomide and bevacizumab reduced endothelial AVM cell proliferation. Bevacizumab inhibited circular network formation of endothelial AVM cells and lowered VEGF gene and protein expression, even though the cells were exposed to mechanical stress. With promising in vitro results, bevacizumab was used to treat three patients with unresectable AVMs or to prevent regrowth after incomplete resection. Bevacizumab controlled bleeding, pulsation, and pain over the follow up of eight months with no patient-reported side effects. Overall, mechanical stress increases VEGF expression in the microenvironment of AVM cells. The monoclonal VEGF antibody bevacizumab alleviates this effect, prevents circular network formation and proliferation of AVM endothelial cells in vitro. The clinical application of bevacizumab in AVM treatment demonstrates effective symptom control with no side effects.

[Persistent olfactory impairment after COVID-19-recommendations of the Working Group on Olfactology and Gustology of the German Society of Oto-rhino-laryngology, Head and Neck Surgery]. / Persistierende Riechminderung nach COVID-19 ­ Empfehlungen der Arbeitsgemeinschaft Olfaktologie und Gustologie der Deutschen Gesellschaft für Hals-Nasen-Ohren-Heilkunde, Kopf- und Hals-Chirurgie e. V.

This article does not intend to comprehensively review the existing literature on coronavirus disease 2019 (COVID-19)-associated smell disorders, but aims to summarize scientific evidence for otorhinolaryngological practice and provide recommendations for diagnosis and treatment of persistent smell disorders following COVID-19.

Topical Administration of Mometasone Is Not Helpful in Post-COVID-19 Olfactory Dysfunction.

Persistent olfactory dysfunction is a major concern post-COVID-19, affecting up to 5% of all patients. Different therapeutic options, including mometasone nasal spray, have been recommended, only some of which have been validated for post-COVID-19 olfactory dysfunction. In this study we psychophysically assessed the effect of intranasally applied mometasone furoate on the recovery of olfaction. The spray was applied with a long applicator so that the olfactory cleft could be reached effectively. After olfactory dysfunction had been confirmed psychophysically using Sniffin' Sticks, patients were randomly assigned to two different treatment arms: the study group (n = 40) underwent olfactory training and intranasal administration of mometasone furoate twice daily, whereas the control group (n = 46) performed olfactory training only. After a study duration of three months, psychophysical testing of olfaction was repeated using Sniffin' Sticks. We found no benefit of an additional topical administration of mometasone furoate compared to olfactory training alone. These results psychophysically confirm two previous studies which were based on patients' subjective self-ratings. Our findings are in contrast to current recommendations for the management of olfactory dysfunction post-COVID-19, which might have to be adapted accordingly.

Presurgical olfactory function as an indicator of the outcome of functional endoscopic sinus surgery in chronic rhinosinusitis with nasal polyps.

INTRODUCTION: Chronic rhinosinusitis with nasal polyps (CRSwNP) often leads to impaired olfactory function and reduced quality of life. When conservative treatments such as nasal irrigation and topical steroids fail, functional endoscopic sinus surgery (FESS) is often necessary, because it improves symptoms and enhances quality of life. MATERIALS AND METHODS: A total of 88 patients was included in this prospective study. All subjects underwent an extensive examination both presurgically and 4 months after operations including nasal endoscopy and psychophysical olfactory testing (Sniffin' Sticks). Moreover, disease-specific quality of life was assessed and presurgical CT scans were rated regarding the opacification of the paranasal sinuses. RESULTS: Presurgically psychophysical tests showed an overall olfactory dysfunction. Olfactory test results (TDI score) correlated with endoscopic (Lund-Kennedy and Lildtholdt score) and CT scores (Lund-Mackay and TOCS scores). Four months after surgery olfactory function was enhanced and quality of life significantly showed an overall improvement. However, the outcome was dependent on the extent of presurgical olfactory function: olfaction and quality of life improved most pronounced in anosmics compared to hyposmic and especially normosmic patients. CONCLUSIONS: This study confirmed that FESS in CRSwNP leads to a significant improvement of both olfaction and disease-specific quality of life. Moreover, preoperative psychophysical assessment of the extent of olfactory dysfunction can help to objectively assess possible risks and expected benefits of the surgery in terms of olfaction and quality of life.

Prevalence of acute olfactory dysfunction differs between variants of SARS-CoV-2-results from chemosensitive testing in wild type, VOC alpha (B.1.1.7) and VOC delta (B.1617.2).

BACKGROUND: Olfactory dysfunction is one of the leading symptoms of COVID-19. Previous data suggest a different prevalence between the wild type virus and its subsequent variants. Here, we report on a prospective study to psychophysically compare olfactory function in acute SARS-CoV-2 infection between wild type, VOC alpha and VOC delta. METHODS: SARS-CoV-2 was confirmed by reverse-transcription quantitative real-time PCR and virus variants were differentiated by high-sensitive next-generation sequencing. Home-quarantined were sent a validated and blinded smell identification test. A detailed instruction ensured correct self-administration. RESULTS: A total of 125 patients were included in study. Patients with the wild type of SARS-CoV-2 self-evaluated their olfactory function significant lower on the visual analog score compared patients with the VOCs alpha or delta (4.1 ± 1.5 vs. 6.8 ± 2.9 and 7.3 ± 0.9; p < 0.001). Likewise, a significant difference of the prevalence of psychophysically confirmed hyposmia (wild type: 73%; alpha: 41%; delta 48%; p < 0.01) and smell test score (48 ± 25% vs. 70 ± 23% and 67 ± 18%; p < 0.01) could be seen between wild type on one side and VOCs alpha and delta on the other side. CONCLUSION: In this study, both self-reports and psychophysical testing revealed a significant higher prevalence of olfactory impairment in the wild type of SARS-CoV-2 compared to the VOCs alpha and delta.

Epithelial immune regulation of inflammatory airway diseases: Chronic rhinosinusitis with nasal polyps (CRSwNP).

BACKGROUND: The epithelial immune regulation is an essential and protective feature of the barrier function of the mucous membranes of the airways. Damage to the epithelial barrier can result in chronic inflammatory diseases, such as chronic rhinosinusitis (CRS) or bronchial asthma. Thymic stromal lymphopoietin (TSLP) is a central regulator in the epithelial barrier function and is associated with type 2 (T2) and non-T2 inflammation. MATERIALS AND METHODS: The immunology of chronic rhinosinusitis with polyposis nasi (CRSwNP) was analyzed in a literature search, and the existing evidence was determined through searches in Medline, Pubmed as well as the national and international study and guideline registers and the Cochrane Library. Human studies or studies on human cells that were published between 2010 and 2020 and in which the immune mechanisms of TSLP in T2 and non-T2 inflammation were examined were considered. RESULTS: TSLP is an epithelial cytokine (alarmin) and a central regulator of the immune reaction, especially in the case of chronic airway inflammation. Induction of TSLP is implicated in the pathogenesis of many diseases like CRS and triggers a cascade of subsequent inflammatory reactions. CONCLUSION: Treatment with TSLP-blocking monoclonal antibodies could therefore open up interesting therapeutic options. The long-term safety and effectiveness of TSLP blockade has yet to be investigated.

Persisting olfactory dysfunction in post-COVID-19 is associated with gustatory impairment: Results from chemosensitive testing eight months after the acute infection.

Olfactory and gustatory disorders are prominent symptoms of acute COVID-19. Although both senses recover in many patients within weeks to months, persistency has been described in up to 60%. However up to now most reports on the course of chemosensitive disorders after COVID-19 are not based on psychophysical testing but only on subjective patients' ratings. In this study we assessed both olfaction and gustation using psychophysical tests eight months after COVID-19. Validated psychophysical testing revealed hyposmia in 18% and hypogeusia in even 32% of 303 included patients. This shows that olfactory and especially gustatory disorders have to be seen as important chronic symptoms post-COVID-19. The high prevalence of gustatory dysfunction indicates that gustatory function does not recover or might even deteriorate in the months following the acute infection.

Gustatory Function in Acute COVID-19 - Results From Home-Based Psychophysical Testing.

OBJECTIVE: Gustatory function during COVID-19 is self-reported by around 50% of patients. However, only a few studies assessed gustation using psychophysical testing during acute infection. The objective of this study is to test gustatory function on threshold tests in the very first days of COVID-19. METHODS: Psychophysical testing consisted of validated and blinded tests for olfaction (NHANES Pocket Smell Test) and gustation (Taste Strips Test). These test kits were sent to home-quarantined patients and self-administered using a detailed instruction sheet. RESULTS: A total of 51 patients were included in this study. Testing was performed 6.5 ± 2.7 days after sampling of respiratory swabs. At this time 37% of patients stated to currently experience a gustatory impairment. The mean Taste Strips score was 10.0 ± 3.4 with 28% scoring in the range of hypogeusia. Interestingly, no significant difference in the results of gustatory testing could be observed between the group with subjectively preserved gustation and the group with self-rated taste impairment. CONCLUSION: During the very first days of COVID-19, psychophysical gustatory testing revealed hypogeusia in 28%. This is far lower than patients' self-reports. Different from previous studies, we did not find clear evidence for an impairment of only certain taste qualities. LEVEL OF EVIDENCE: 3 Laryngoscope, 132:1082-1087, 2022.

The taste of the pandemic-contemporary review on the current state of research on gustation in coronavirus disease 2019 (COVID-19).

Subjectively perceived impairment of taste is a common and distinct symptom of coronavirus disease 2019 (COVID-19). Large meta-analyses identified this symptom in approximately 50% of cases. However, this high prevalence is not supported by blinded and validated psychophysical gustatory testing, which showed a much lower prevalence in up to 26% of patients. This discrepancy may be due to misinterpretation of impaired retronasal olfaction as gustatory dysfunction. In addition, we hypothesized that COVID-19-associated hyposmia is involved in the decrease of gustatory function, as found for hyposmia of different origin. This indirect mechanism would be based on the central-nervous mutual amplification between the chemical senses, which fails in COVID-19-associated olfactory loss. However, further research is necessary on how severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) may directly impair the gustatory pathway as well as its subjective perception.

A third hand to the surgeon: the use of an endoscope holding arm in endonasal sinus surgery and well beyond.

BACKGROUND: Extended endoscopic endonasal operations of the sinuses and the frontal skull base require a bimanual action of the surgeon in many cases. Thus, typically an assistant guides the endoscope and centers the field of view. In this study, we investigate in which cases an endoscope holding arm can be used alternatively. MATERIALS AND METHODS: The electromagnetic system ENDOFIXexo was used in different surgical interventions of the paranasal sinuses and beyond questioning ergonomics and geometrical limitations. The realized degrees of freedom were documented, and a topography of possible applications compiled. RESULTS: The presented system is limited by the anatomy of the anterior ethmoid and dynamic working conditions in the sagittal direction. Especially in extended interventions in the posterior ethmoid, in which parts of the nasal septum have been resected and a static position of the endoscope is desired the surgeon can greatly benefit from the robotic arm. Moreover, through the high flexibility of the endoscopic arm surgeries of the pharynx and larynx were performed, questioning the current gold standard of microscope-assisted surgical procedures. CONCLUSION: Under the impression of an urging staff shortage and due to its unlimited patience, the ENDOFIXexo arm seems promising. Taking into account the complex anatomy and the limited access, we especially see a favorable field of application in the surgery of the pituitary gland and skull base tumors.

Machine-Learning Points at Endoscopic, Quality of Life, and Olfactory Parameters as Outcome Criteria for Endoscopic Paranasal Sinus Surgery in Chronic Rhinosinusitis.

Chronic rhinosinusitis (CRS) is often treated by functional endoscopic paranasal sinus surgery, which improves endoscopic parameters and quality of life, while olfactory function was suggested as a further criterion of treatment success. In a prospective cohort study, 37 parameters from four categories were recorded from 60 men and 98 women before and four months after endoscopic sinus surgery, including endoscopic measures of nasal anatomy/pathology, assessments of olfactory function, quality of life, and socio-demographic or concomitant conditions. Parameters containing relevant information about changes associated with surgery were examined using unsupervised and supervised methods, including machine-learning techniques for feature selection. The analyzed cohort included 52 men and 38 women. Changes in the endoscopic Lildholdt score allowed separation of baseline from postoperative data with a cross-validated accuracy of 85%. Further relevant information included primary nasal symptoms from SNOT-20 assessments, and self-assessments of olfactory function. Overall improvement in these relevant parameters was observed in 95% of patients. A ranked list of criteria was developed as a proposal to assess the outcome of functional endoscopic sinus surgery in CRS patients with nasal polyposis. Three different facets were captured, including the Lildholdt score as an endoscopic measure and, in addition, disease-specific quality of life and subjectively perceived olfactory function.