Identification of Lung Innervating Sensory Neurons and Their Target Specificity

Known as the gas exchange organ, the lung is also critical for responding to the aerosol environment in part through interaction with the nervous system. The diversity and specificity of lung innervating neurons remains poorly understood. Here, we interrogated the cell body location, molecular signature and projection pattern of lung innervating sensory neurons. Retrograde tracing from the lung coupled with whole tissue clearing highlighted neurons primarily in the vagal ganglia. Centrally, they project specifically to the nucleus of the solitary tract in the brainstem. Peripherally, they enter the lung alongside branching airways. Labeling of nociceptor Trpv1+ versus peptidergic Tac1+ vagal neurons showed shared and distinct terminal morphology and targeting to airway smooth muscles, vasculature including lymphatics, and alveoli. Notably, a small population of vagal neurons that are Calb1+ preferentially innervate pulmonary neuroendocrine cells, a demonstrated airway sensor population. This atlas of lung innervating neurons serves as a foundation for understanding their function in lung.

Cell-autonomous immune gene expression is repressed in pulmonary neuroendocrine cells and small cell lung cancer

Small cell lung cancer (SCLC) is classified as a high-grade neuroendocrine (NE) tumor, but a subset of SCLC has been termed “variant” due to the loss of NE characteristics. In this study, we computed NE scores for patient-derived SCLC cell lines and xenografts, as well as human tumors. We aligned NE properties with transcription factor-defined molecular subtypes. Then we investigated the different immune phenotypes associated with high and low NE scores. We found repression of immune response genes as a shared feature between classic SCLC and pulmonary neuroendocrine cells of the healthy lung. With loss of NE fate, variant SCLC tumors regain cell-autonomous immune gene expression and exhibit higher tumor-immune interactions. Pan-cancer analysis revealed this NE lineage-specific immune phenotype in other cancers. Additionally, we observed MHC I re-expression in SCLC upon development of chemoresistance. These findings may help guide the design of treatment regimens in SCLC.

COEXISTENCE OF PULMONARY FIBROSIS AND PROLIFERATION OF PULMONARY NEUROENDOCRINE CELLS FORMING TUMORLET

Tumorlet is a disease rarely diagnosed in clinical practice. It is characterized by pulmonary neuroendocrine cell (PNEC) proliferation which invades the bronchiolar basement membrane and forms nodules with a diameter smaller than 5 mm. Case report: 72-year-old female patient was suffered for many years from progressive dyspnea and coughing with evidence of pulmonary fibrosis on high resolution computed tomography (HRCT). As a result of a lung biopsy, based on immunohistochemical tests, a 2 mm cluster of neuroendocrine cells (NEC) was found and it was diagnosed as tumorlet. Due to a long-term, insidious progress of the disease, as well as sex and age of the patient, the case emphasizes that differential diagnosis should include tumorlet as well as diffuse idiopathic neuroendocrine cell hyperplasia (DIPNECH) as a more extensive manifestation of neuroendocrine cell proliferation in the respiratory tract.

Pulmonary neuroendocrine cells: physiology, tissue homeostasis and disease

ABSTRACTMammalian lungs have the ability to recognize external environments by sensing different compounds in inhaled air. Pulmonary neuroendocrine cells (PNECs) are rare, multi-functional epithelial cells currently garnering attention as intrapulmonary sensors; PNECs can detect hypoxic conditions through chemoreception. Because PNEC overactivation has been reported in patients suffering from respiratory diseases – such as asthma, chronic obstructive pulmonary disease, bronchopulmonary dysplasia and other congenital diseases – an improved understanding of the fundamental characteristics of PNECs is becoming crucial in pulmonary biology and pathology. During the past decade, murine genetics and disease models revealed the involvement of PNECs in lung ventilation dynamics, mechanosensing and the type 2 immune responses. Single-cell RNA sequencing further unveiled heterogeneous gene expression profiles in the PNEC population and revealed that a small number of PNECs undergo reprogramming during regeneration. Aberrant large clusters of PNECs have been observed in neuroendocrine tumors, including small-cell lung cancer (SCLC). Modern innovation of imaging analyses has enabled the discovery of dynamic migratory behaviors of PNECs during airway development, perhaps relating to SCLC malignancy. This Review summarizes the findings from research on PNECs, along with novel knowledge about their function. In addition, it thoroughly addresses the relevant questions concerning the molecular pathology of pulmonary diseases and related therapeutic approaches.