106 - The IL-33/ST2-axis Contributes to Development of Bronchopulmonary Dysplasia-associated Pulmonary Hypertension

Poster Number: 106
Publication Number: 106.2136

Background: Pulmonary hypertension (PH) marks the most severe subset of the multifactorial lung disease of premature infants, bronchopulmonary dysplasia (BPD). While the underlying processes that produces PH in this context remain poorly understood, type 2 polarized immunity, of which signaling by IL-33 and its receptor (composed of ST2 and the IL-1R accessory protein) are major components, has been recently implicated in the development of BPD-PH.

Objective: We hypothesize that IL-33/ST2 signaling promotes the development of BPD-PH. We aimed to characterize how IL-33/ST2 signaling altered the lung transcriptome in BPD-PH.

Design/Methods: Neonatal Il33-/- (IL-33 KO), Il1rl1-/- (ST2 KO) and Il1racp-/- (IL-1Racp KO) or congenic B6.129 control mice were exposed to hyperoxia (FiO2 0.85) or normoxia (FiO2 0.21) from postnatal days 3-14 (Fig. 1a). We then generated an integrated transcriptomic landscape using a combination of bulk and single nuclei (sn) RNA-seq. We also quantified BPD-like lung injury and PH in these mice using histological morphometry, forced oscillometry (flexiVent) and echocardiography.

Results: PH, as quantified by right ventricular systolic pressure, increased in hyperoxia-exposed control animals but was reduced in all three KO mice strains (p < 0.005, two-way ANOVA, Fig. 1b). We also observed a similar improvement in lung alveolarization. Global gene expression was altered in hyperoxia exposed mice (Fig. 1c). This was partially reduced in hyperoxia-exposed IL-33 and ST2 KO mice, but most extensively in IL1Racp KO mice. The strongest differences in hyperoxia-exposed neonates were in type 2 inflammation-related genes in IL1Racp KO mice, where the expression of type 2 inflammation-related genes were ameliorated to the point they resembled normoxia exposed controls (Fig. 1d). SnRNAseq revealed 27 clusters from a subset of 10,000 high-quality single nuclei (Fig. 1e). We then focused on endothelial cells due to our interest in PH. We noted increased generalized capillary cells (gCap) in hyperoxia-exposed controls that was reduced in all KO strains. While differentially expressed genes between the different subsets of endothelial cells between normoxia and hyperoxia control animals resembled patterns seen in bulk RNAseq, we detected genotypic differences using snRNAseq.

Conclusion(s): IL-33/ST2 signaling is involved in the development and propagation of BPD-PH in the mouse model. Differences in capillary endothelial cell regeneration may have therapeutic implications for human disease.