Neuroendocrinology of the lung revealed by single-cell RNA sequencing

Evaluation and clinical significance of serum neurospecific enolase in children with pneumonia: a case-control study

BACKGROUND

Neurospecific Enolase (NSE), a multifunctional protein, is present in various tissues of the body and plays an important role in many disease processes, such as infection, inflammation, tumours, injury, and immunity. In recent years, the application of NSE in respiratory diseases has become increasingly widespread and a research hotspot.

OBJECTIVE

This study aims to explore the relationship between NSE and childhood pneumonia, providing assistance for the diagnosis and assessment of pneumonia.

METHODS

Using prospective research and case-control methods, We selected 129 children with pneumonia hospitalised in Weifang People's Hospital from September 2020 to April 2022 as the case group. Among them were 67 cases of Mycoplasma pneumoniae pneumonia (MP+), 62 cases of non-Mycoplasma pneumoniae pneumonia (MP -), and 21 cases of severe pneumonia. At the same time, 136 children who underwent outpatient health examinations were selected as the control group. The levels of NSE, ESR, CRP in cases group and NSE in control group were measured separately.

RESULT

The NSE levels in the MP + group were 17.86 (14.29-22.54) ng/mL, while those in the MP- group were 17.89 (14.10-21.66) ng/mL, both of which were higher than the control group's NSE levels of 13.26(12.18,14.44) ng/mL (H = 46.92, P = 0.000). There was no statistically significant difference in NSE levels between the MP + and MP - groups (P > 0.05). The NSE level in the severe pneumonia group was 27.38 (13.95-34.06) ng/mL, higher than that in the mild pneumonia group, which was 17.68 (14.27-21.04) ng/mL, (P = 0.024). The AUC values for diagnosing pneumonia are NSE0.714, CRP0.539, and ESR0.535, with NSE having the highest diagnostic value.

CONCLUSION

Serum NSE can serve as an inflammatory indicator for paediatric pneumonia, which has important clinical guidance significance for the diagnosis, condition evaluation, and prognosis of paediatric pneumonia.

The mucosal concept in chronic rhinosinusitis: Focus on the epithelial barrier

Chronic rhinosinusitis (CRS) is a common chronic nasal cavity and sinus disease affecting a growing number of individuals worldwide. Recent advances have shifted our understanding of CRS pathophysiology from a physical obstruction model of ventilation and drainage to a mucosal concept that recognizes the complexities of mucosal immunologic variations and cellular aberrations. A growing number of studies have demonstrated the alteration of the epithelial barrier during inflammatory states. Therefore, the current review has focused on the crucial role of epithelial cells within this mucosal framework in CRS, detailing the perturbed epithelial homeostasis, impaired epithelial cell barrier, dysregulated epithelial cell repair processes, and enhanced interactions between epithelial cells and immune cells. Notably, the utilization of novel technologies, such as single-cell transcriptomics, has revealed the novel functions of epithelial barriers, such as inflammatory memory and neuroendocrine functions. Therefore, this review also emphasizes the importance of epithelial inflammatory memory and the necessity of further investigations into neuroendocrine epithelial cells and neurogenic inflammation in CRS. We conclude by contemplating the prospective benefits of epithelial cell-oriented biological treatments, which are currently under investigation in rigorous randomized, double-blind clinical trials in patients with CRS with nasal polyps.

Investigating pulmonary neuroendocrine cells in human respiratory diseases with airway models

Despite accounting for only ∼0.5% of the lung epithelium, pulmonary neuroendocrine cells (PNECs) appear to play an outsized role in respiratory health and disease. Increased PNEC numbers have been reported in a variety of respiratory diseases, including chronic obstructive pulmonary disease and asthma. Moreover, PNECs are the primary cell of origin for lung neuroendocrine cancers, which account for 25% of aggressive lung cancers. Recent research has highlighted the crucial roles of PNECs in lung physiology, including in chemosensing, regeneration and immune regulation. Yet, little is known about the direct impact of PNECs on respiratory diseases. In this Review, we summarise the current associations of PNECs with lung pathologies, focusing on how new experimental disease models, such as organoids derived from human pluripotent stem cells or tissue stem cells, can help us to better understand the contribution of PNECs to respiratory diseases.

Sentinels of the airways

Epithelial cells in the larynx and trachea sense harmful cues and trigger protective reflexes.

Neuroendocrine cells initiate protective upper airway reflexes

Airway neuroendocrine (NE) cells have been proposed to serve as specialized sensory epithelial cells that modulate respiratory behavior by communicating with nearby nerve endings. However, their functional properties and physiological roles in the healthy lung, trachea, and larynx remain largely unknown. In this work, we show that murine NE cells in these compartments have distinct biophysical properties but share sensitivity to two commonly aspirated noxious stimuli, water and acid. Moreover, we found that tracheal and laryngeal NE cells protect the airways by releasing adenosine 5'-triphosphate (ATP) to activate purinoreceptive sensory neurons that initiate swallowing and expiratory reflexes. Our work uncovers the broad molecular and biophysical diversity of NE cells across the airways and reveals mechanisms by which these specialized excitable cells serve as sentinels for activating protective responses.

A vagal reflex evoked by airway closure

Airway integrity must be continuously maintained throughout life. Sensory neurons guard against airway obstruction and, on a moment-by-moment basis, enact vital reflexes to maintain respiratory function1,2. Decreased lung capacity is common and life-threatening across many respiratory diseases, and lung collapse can be acutely evoked by chest wall trauma, pneumothorax or airway compression. Here we characterize a neuronal reflex of the vagus nerve evoked by airway closure that leads to gasping. In vivo vagal ganglion imaging revealed dedicated sensory neurons that detect airway compression but not airway stretch. Vagal neurons expressing PVALB mediate airway closure responses and innervate clusters of lung epithelial cells called neuroepithelial bodies (NEBs). Stimulating NEBs or vagal PVALB neurons evoked gasping in the absence of airway threats, whereas ablating NEBs or vagal PVALB neurons eliminated gasping in response to airway closure. Single-cell RNA sequencing revealed that NEBs uniformly express the mechanoreceptor PIEZO2, and targeted knockout of Piezo2 in NEBs eliminated responses to airway closure. NEBs were dispensable for the Hering-Breuer inspiratory reflex, which indicated that discrete terminal structures detect airway closure and inflation. Similar to the involvement of Merkel cells in touch sensation3,4, NEBs are PIEZO2-expressing epithelial cells and, moreover, are crucial for an aspect of lung mechanosensation. These findings expand our understanding of neuronal diversity in the airways and reveal a dedicated vagal pathway that detects airway closure to help preserve respiratory function.

The Coding Logic of Interoception

Interoception, the ability to precisely and timely sense internal body signals, is critical for life. The interoceptive system monitors a large variety of mechanical, chemical, hormonal, and pathological cues using specialized organ cells, organ innervating neurons, and brain sensory neurons. It is important for maintaining body homeostasis, providing motivational drives, and regulating autonomic, cognitive, and behavioral functions. However, compared to external sensory systems, our knowledge about how diverse body signals are coded at a system level is quite limited. In this review, we focus on the unique features of interoceptive signals and the organization of the interoceptive system, with the goal of better understanding the coding logic of interoception.

The olfactory receptor Olfr78 promotes differentiation of enterochromaffin cells in the mouse colon

The gastrointestinal epithelium constitutes a chemosensory system for microbiota-derived metabolites such as short-chain fatty acids (SCFA). Here, we investigate the spatial distribution of Olfr78, one of the SCFA receptors, in the mouse intestine and study the transcriptome of colon enteroendocrine cells expressing Olfr78. The receptor is predominantly detected in the enterochromaffin and L subtypes in the proximal and distal colon, respectively. Using the Olfr78-GFP and VilCre/Olfr78flox transgenic mouse lines, we show that loss of epithelial Olfr78 results in impaired enterochromaffin cell differentiation, blocking cells in an undefined secretory lineage state. This is accompanied by a reduced defense response to bacteria in colon crypts and slight dysbiosis. Using organoid cultures, we further show that maintenance of enterochromaffin cells involves activation of the Olfr78 receptor via the SCFA ligand acetate. Taken together, our work provides evidence that Olfr78 contributes to colon homeostasis by promoting enterochromaffin cell differentiation.

Loss of microRNA-30a and sex-specific effects on the neonatal hyperoxic lung injury

BACKGROUND

Bronchopulmonary dysplasia (BPD) is characterized by an arrest in lung development and is a leading cause of morbidity in premature neonates. It has been well documented that BPD disproportionally affects males compared to females, but the molecular mechanisms behind this sex-dependent bias remain unclear. Female mice show greater preservation of alveolarization and angiogenesis when exposed to hyperoxia, accompanied by increased miR-30a expression. In this investigation, we tested the hypothesis that loss of miR-30a would result in male and female mice experiencing similar impairments in alveolarization and angiogenesis under hyperoxic conditions.

METHODS

Wild-type and miR-30a-/- neonatal mice were exposed to hyperoxia [95% FiO2, postnatal day [PND1-5] or room air before being euthanized on PND21. Alveolarization, pulmonary microvascular development, differences in lung transcriptome, and miR-30a expression were assessed in lungs from WT and miR-30a-/- mice of either sex. Blood transcriptomic signatures from preterm newborns (with and without BPD) were correlated with WT and miR-30a-/- male and female lung transcriptome data.

RESULTS

Significantly, the sex-specific differences observed in WT mice were abrogated in the miR-30a-/- mice upon exposure to hyperoxia. The loss of miR-30a expression eliminated the protective effect in females, suggesting that miR-30a plays an essential role in regulating alveolarization and angiogenesis. Transcriptome analysis by whole lung RNA-Seq revealed a significant response in the miR-30a-/- female hyperoxia-exposed lung, with enrichment of pathways related to cell cycle and neuroactive ligand-receptor interaction. Gene expression signature in the miR-30a-/- female lung associated with human BPD blood transcriptomes. Finally, we showed the spatial localization of miR-30a transcripts in the bronchiolar epithelium.

CONCLUSIONS

miR-30a could be one of the biological factors mediating the resilience of the female preterm lung to neonatal hyperoxic lung injury. A better understanding of the effects of miR-30a on pulmonary angiogenesis and alveolarization may lead to novel therapeutics for treating BPD.

A novel classifier combining G protein-coupled receptors and the tumor microenvironment is associated with survival status in glioblastoma

Background: Numerous studies have highlighted the crucial role of G protein-coupled receptors (GPCRs) in tumor microenvironment (TME) remodeling and their correlation with tumor progression. However, the association between GPCRs and the TME in glioblastoma (GBM) remains largely unexplored. Methods: In this study, we investigated the expression profile of GPCRs in GBM using integrated data from single-cell RNA sequencing and bulk sequencing. Surgical samples obtained from meningioma and GBM patients underwent single-cell RNA sequencing to examine GPCR levels and cell-cell interactions. Tumor microenvironment (TME) score is calculated by the infiltrated immune cells with CIBERSORT. Results: Our findings revealed a predominantly increased expression of GPCRs in GBM, and demonstrated that the classification of GPCRs and TME is an independent risk factor in GBM. Patients with high GPCR expression in the tumor tissue and low TME score exhibited the worst outcomes, suggesting a potentially aggressive tumor phenotype. On the other hand, patients with low GPCR expression in the tumor tissue and high TME score showed significantly better outcomes, indicating a potentially more favorable tumor microenvironment. Furthermore, the study found that T cells with high GPCR levels displayed extensive cell-cell connections with other tumor and immune cells in the single cell RNA analysis, indicating their potential involvement in immune escape. Conclusion: In conclusion, GPCRs in combination with TME classification can serve as prognostic markers for GBM. GPCRs play an essential role in tumor progression and the TME in GBM.

Chronic airway epithelial hypoxia exacerbates injury in muco-obstructive lung disease through mucus hyperconcentration

Unlike solid organs, human airway epithelia derive their oxygen from inspired air rather than the vasculature. Many pulmonary diseases are associated with intraluminal airway obstruction caused by aspirated foreign bodies, virus infection, tumors, or mucus plugs intrinsic to airway disease, including cystic fibrosis (CF). Consistent with requirements for luminal O2, airway epithelia surrounding mucus plugs in chronic obstructive pulmonary disease (COPD) lungs are hypoxic. Despite these observations, the effects of chronic hypoxia (CH) on airway epithelial host defense functions relevant to pulmonary disease have not been investigated. Molecular characterization of resected human lungs from individuals with a spectrum of muco-obstructive lung diseases (MOLDs) or COVID-19 identified molecular features of chronic hypoxia, including increased EGLN3 expression, in epithelia lining mucus-obstructed airways. In vitro experiments using cultured chronically hypoxic airway epithelia revealed conversion to a glycolytic metabolic state with maintenance of cellular architecture. Chronically hypoxic airway epithelia unexpectedly exhibited increased MUC5B mucin production and increased transepithelial Na+ and fluid absorption mediated by HIF1α/HIF2α-dependent up-regulation of β and γENaC (epithelial Na+ channel) subunit expression. The combination of increased Na+ absorption and MUC5B production generated hyperconcentrated mucus predicted to perpetuate obstruction. Single-cell and bulk RNA sequencing analyses of chronically hypoxic cultured airway epithelia revealed transcriptional changes involved in airway wall remodeling, destruction, and angiogenesis. These results were confirmed by RNA-in situ hybridization studies of lungs from individuals with MOLD. Our data suggest that chronic airway epithelial hypoxia may be central to the pathogenesis of persistent mucus accumulation in MOLDs and associated airway wall damage.

Development and verification of new monoclonal orthopedia homeobox (OTP) specific antibodies for pulmonary carcinoid diagnostics

Background

Orthopedia homeobox (OTP) has shown to be a useful prognostic marker to predict outcome in pulmonary carcinoids, which is also supported by the World Health Organization. However, the discontinuation of the initially used polyclonal antibody and absence of a reliable routinely applicable monoclonal OTP antibody hampers implementation in routine diagnostics. Here, new monoclonal antibodies directed against OTP were developed and verified on formalin-fixed paraffin-embedded tissue of pulmonary neuroendocrine tumors (NETs) for clinical diagnostics.

Methods

OTP specific monoclonal antibodies were produced from mice immunised with a recombinant human OTP protein fragment. Enzyme-linked immunosorbent assay (ELISA) positive hybridomas were evaluated using immunohistochemistry (IHC). Following epitope-mapping and isotyping, purified monoclonal antibodies were validated for IHC in formalin-fixed paraffin-embedded tissues, the optimal dilution was determined, and results were cross validated with the OTP polyclonal antibody (HPA039365, Atlas Antibodies). Staining protocols were optimized on two automated staining platforms and performance was harmonized using a tissue microarray (TMA).

Results

Two clones (CL11222 and CL11225) were selected for purified monoclonal antibody (mAb) production. Intratumor heterogeneity assessment revealed similar performance for both clones. While clone CL11225 displayed a unique epitope compared to those present in the polyclonal antibody, this clone performed most similar to the polyclonal antibody. Cross-platform assessment revealed an excellent agreement for clone CL11225 while clone CL11222 showed somewhat discordant results on Dako.

Conclusions

New monoclonal OTP specific antibodies have been developed and verified on different automated immunohistochemical staining platforms. The OTP specific monoclonal antibodies showed excellent agreement with the often-used polyclonal antibody allowing application in routine diagnostics.