359 - Extracellular Matrix Gene Expression is Dysregulated in the Preterm Lamb Model of Bronchopulmonary Dysplasia-Pulmonary Hypertension

Publication Number: 1343.359

Yasmine White, University of Utah School of Medicine, Salt Lake City, UT, United States; Mar Janna Dahl, University of Utah School of Medicine, Salt Lake City, UT, United States; Matthew Douglass, University of Utah School of Medicine, Salt Lake City, UT, United States; Jeffrey Fineman, University of California, San Francisco, School of Medicine, San Francisco, CA, United States; Emin Maltepe, UCSF Benioff Children's Hospital San Francisco, San Francisco, CA, United States; Kevin Watt, University of Utah, Salt Lake City, UT, United States; Kurt H. Albertine, University of Utah, Salt Lakr City, UT, United States

Background: Bronchopulmonary dysplasia-pulmonary hypertension (BPD-PH) is a devastating complication of prematurity that is associated with increased morbidity and mortality. BPD-PH occurs when premature birth interrupts normal lung development, which is then compounded by postnatal mechanical ventilation and oxidative stress that cause additional lung injury and lead to pulmonary vascular remodeling. No targeted therapies exist to halt the progression of BPD-PH. Understanding the molecular pathways contributing to the development of BPD-PH in large-animal models is critical to developing novel therapeutic strategies.

Objective: To determine how premature birth and prolonged mechanical ventilation affect extracellular matrix gene expression and deposition in the preterm lamb model of BPD-PH.

Design/Methods: Time-dated ewes received antenatal steroids prior to Cesarian section lamb delivery at 125 days gestation. Lambs were intubated, resuscitated using forced oscillation ventilation technique, administered caffeine and surfactant, and then assigned to 21 days of chronic mechanical ventilation (MV) or extubated to 21 days of noninvasive respiratory support (control). Lung tissue was collected on day 21 and used for bulk RNA sequencing, Masson's trichrome and Van Gieson staining, and protein extraction quantification of collagen I and collagen III by Western blot.

Results: 449 differentially expressed genes were identified by RNAseq (Figure 1). Gene set enrichment analysis identified three significantly enriched pathways: extracellular matrix (ECM) organization, extracellular structure organization, and external encapsulating structure organization (adjusted p-value 0.033). Masson's trichrome staining suggested increased collagen staining in mechanically ventilated lambs (80% vs 67% of tissue area, p=0.10).

Conclusion(s): Lung ECM gene expression is dysregulated in the preterm lamb model of BPD-PH, consistent with limited data available from human studies. Pathways leading to increased ECM deposition represent novel targets for BPD-PH therapies.

Figure 1: Differential gene expression in lung tissue from lambs with BPD-PH.
A) Principal component analysis of normalized RNA-seq gene expression data. B) Heat map of 449 differentially expressed genes. C) Gene set enrichment analysis showing significantly upregulated pathways.