A106-15 Impact of Antenatal Corticosteroids on the Developing Lung at Single-cell Resolution

Abstract Rationale Sexual dimorphism in disease pathophysiology may underlie the differences in response to therapy. The mechanisms behind sex-specific differences in therapeutic responses are understudied in preterm neonates. We recently highlighted such differences in response to antenatal and postnatal corticosteroids, among other drugs that are commonly used in the NICU. We hypothesized that antenatal corticosteroids would alter the lung transcriptomic landscape and that the male and female developing lungs would be differentially affected. We sought to determine the effects of antenatal dexamethasone (Dex) on the developing lungs at single-cell resolution. The goal was to identify the cell subpopulations affected by corticosteroids and determine whether responses are different in male and female lungs. Methods Pregnant dams were injected with saline or dexamethasone at embryonic day 16.5 and 17.5. Lungs from neonates were harvested at postnatal day 7 and male and female lungs were processed for snRNA-Seq. We used the unbiased Augur bioinformatics pipeline that utilizes a machine learning framework to prioritize cell types impacted by treatment accounting for sex as a biological variable. The area under the receiver operating characteristic curve (AUC) for comparisons is reported, providing an intuitive measure of cell-type prioritization. A higher AUC represents the cells most impacted by dexamethasone treatment. Once identified, differential expression and pathway analysis were performed to identify the transcriptional changes in the affected populations. Results Using snRNA-Seq in the postnatal lung after treatment, we were able to sequence 124,540 cells and identify a total of 32 cell populations (Figure 1A-B). Augur analysis revealed that pulmonary neuroendocrine cells (PNECs) and myeloid cells (neutrophils, proliferating macrophages, and interstitial macrophages) were most affected by antenatal dexamethasone treatment (Figure 1C-D). Sex-specific prioritization of cell populations showed that among the most affected were interstitial macrophages (IM) with larger changes seen in male lungs. (Figure 1E). We next performed differential expression and pathway analysis in IM and observed over 1,000 differentially expressed genes in male lungs in response to Dex compared to 47 in females. Pathways related to branching morphogenesis and transcriptional regulation were upregulated in females while inflammatory response, programmed cell death, and cell surface receptor signaling were upregulated in male IM (Figure 1F). Conclusion The fetal lung cells show differential susceptibility to the administration of maternal dexamethasone. The differential effects may underlie disease pathophysiology and eventual outcomes in male and female preterm neonates. Understanding these mechanisms may help guide sex-informed therapeutic strategies to improve outcomes in preterm infants. This abstract is funded by: R01HL144775