β‐ENaC associated with cilia indicates the distribution of absorptive epithelial cells in the lumen of small airways
Bibliographic record
Abstract
Airway surface liquid (ASL) is crucial for optimal clearance of mucus, pathogens and debris from the pulmonary bronchial tree and is managed by a balance between secretory and absorptive activities along the luminal airway surfaces. Immunohistochemically, we recently demonstrated that in small airways, about half of the lining epithelium consists of cells with a secretory phenotype that are confined to the contraluminal regions (pleats) of the plicated luminal epithelium (1). However, the distribution/location of absorptive airway epithelial cells has not been demonstrated. The epithelial sodium channel (ENaC) is responsible for Na(+) absorption across the apical membranes of many salt absorbing epithelia including airways. Herein, we hypothesized that localization of β‐ENaC subunits would define the distribution of absorptive cells in airway epithelia. We obtained small pieces of peripheral porcine lung tissue of approximately 0.5 cm 3 and pieces of trachea of approximately 0.5 cm 2 that were dissected and immediately snap‐frozen at −80°C. Serial tissue sections (7 μm thick) containing cross‐sections of small airways, with a diameter between 0.5 and 1 mm, were used for immunohistochemistry. We used antibodies directed to b‐subunit of ENaC (courtesy C. Fuller), as well antibodies directed to β‐Tubulin and the tight junction protein, ZO1. Western blot analysis demonstrated ENaC expression in cell extracts derived from isolated small airways and trachea. Confocal microscopy of immunostained sections of airway tissue defined the distribution of β‐ENaC subunits in the apical regions of a sub‐set of cells in the small airways and trachea. In small airways, strong staining for β‐subunit was generally restricted to ciliated cells in the region around the tips of folds in the luminal epithelium well separated from the sub‐sets of secretory cells in base of the epithelial pleats where staining was generally absent or faint, but strong for the secretory marker, NKCC1, seen previously (1). In trachea, β‐ENaC subunit staining was mainly observed at the surface of the stratified ciliated epithelium, and absent in regions where submucosal glands were present. Importantly, we observed that β‐subunit of ENaC appeared to co‐localize with the distribution β‐tubulin, a biomarker for cilia. These findings suggest that small airway epithelium contains a subset of epithelial cells with absorptive phenotype, recognized by the high expression of β‐subunit of ENaC. Support or Funding Information Supported by the Cystic Fibrosis Foundation‐MCCC, CFRI and the Nancy Olmsted Trust for Pediatric Respiratory Medicine
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".