218 - The acute effects of mechanical ventilation on type 1 pulmonary epithelial cell gene transcription

Publication Number: 218.6686

Danielle Callaway, University of Texas Southwestern Medical Center, Dallas, TX, United States; Su Zhou, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States; Chen Shen, University of Pennsylvania, Philadelphia, PA, United States; Yun Ying, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States; Michael Morley, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States; Edward Morrisey, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States

Background: Bronchopulmonary dysplasia (BPD) is a life-long lung disease of preterm infants that has few therapeutic options. One predictor of BPD development and severity is prolonged exposure to invasive mechanical ventilation (IMV). Prior studies from our lab have identified that type 1 pulmonary epithelial (AT1) cells, which make up 95% of the surface area of the lung and are important contributors to the extracellular matrix (ECM), are highly enriched in mechanosensitive genes that, when disrupted, impact AT1 cell identity and ECM gene transcription. This study aims to examine the acute effects of IMV in a neonatal mouse model specifically on AT1 cells to determine early drivers of developmental arrest that contribute to BPD.

Objective: To identify the effects of mechanical force during lung development on type 1 pulmonary epithelial cells.

Design/Methods: Neonatal mice (P6-8) were exposed to 2 hours of IMV (15 µl/g tidal volume), after which their lungs were collected for immunohistochemistry and compared to the non-ventilated controls (n=3 per group). In a separate arm, lungs from a P3 pup exposed to IMV and the control were collected for single-cell RNA sequencing (n=1 per group, sex-matched). The top 100 differentially expressed AT1 genes were identified and assessed with gene enrichment analyses.

Results: After 2 hours of IMV, there was no evidence of AT1 cell apoptosis, lineage reprogramming, or change in epithelial cell ratios. Mechanical force-related nuclear YAP and pSMAD2 were constitutively expressed in AT1 cells in both groups. Gene enrichment analysis of differentially expressed genes in AT1 cells from the scRNA-seq dataset revealed that upregulated genes were enriched for histone modification and chromatin modifying enzymes whereas downregulated genes were enriched for necrosis regulation and molecules associated with elastic fibers, an ECM constituent.

Conclusion(s): Neonatal mouse IMV is a useful injury model to further delineate the consequences of mechanical force on the developing lung, specifically as it pertains to AT1 cells. Although there are no acute consequences of mechanical force on AT1 cell reprogramming or apoptosis, further studies that examine the long-term developmental impact will need to be performed as even short-term exposure has consequences on the epigenetic regulation of these cells and ECM-related gene transcription. Further elucidation of these epigenetic changes in AT1 cells and how this contributes to intercellular communication and development of the ECM in the neonatal lung could provide clues to determine which infants will develop BPD and its associated comorbidities.

Abstract Overview
Schematic of abstract including mouse strains used as well as ventilator and age parameters for the study. For histology, 3 pups from the ventilated and non-ventilated control were extracted, stained, and imaged for various studies as listed. One mouse from each group was used for single-cell RNA sequencing and gene enrichment results for AT1 cells are described.