213 - Neonatal Hyperoxia Exposure Exacerbates Acute Allergic Asthma and Results in a Pro-Inflammatory Alveolar Macrophage Phenotype.

Publication Number: 213.5691

Stephanie Tung, Harvard Medical School, Jamaica Plain, MA, United States; Van Thai Ha, Boston children's hospital, Boston, MA, United States; angeles Fernandez-Gonzalez, Boston Children's Hospital, Boston, MA, United States; Xian Lan Liu, Boston Children's Hospital, Boston, MA, United States; Jeong-Ki Kim, Boston Children's Hospital, Brookline, MA, United States; John A. Cortinas, Boston Children's Hospital, Boston, MA, United States; Esi Obeng, Boston Children's Hospital, Boston, MA, United States; Yuan Hao, Boston Children's Hospital, Boston, MA, United States; Alex Mitsialis, Harvard Medical School, Boston, MA, United States; Stella Kourembanas, Harvard Medical School and Boston Children's Hospital, Boston, MA, United States

Background: Bronchopulmonary dysplasia (BPD) is a major cause of morbidity in preterm infants, including long-term pulmonary complications (increased risk for respiratory viral infections and asthma). There is limited understanding of the pathogenesis of these complications, but it has been linked with immune dysfunction. We hypothesize that neonatal hyperoxia (HYRX) results in immune dysfunction that exacerbates asthma. Mesenchymal stromal cell extracellular vesicles (MSC-EVs) have demonstrated protection in preclinical models of neonatal disease including BPD but their long-term effects require further study.

Objective: Using a double hit murine model of HYRX followed by allergic asthma induced by house dust mite (HDM) to evaluate if HYRX results in long-term immunologic dysfunction and the effect of MSC-EVs.

Design/Methods: FVB mice were exposed to HYRX (75% oxygen) from PN0 to PN7 followed by normoxia recovery until PN14, after which they were treated with HDM intranasally for 2 weeks. MSC-EVs were injected intravenously on PN3, PN13, and PN18. Lungs were histologically evaluated for alveolar simplification and inflammation. Animals underwent methacholine challenge test to assess asthma severity. Bronchoalveolar lavage fluid and lung tissue were harvested to measure cytokines and cellular content.

Results: HYRX HDM exhibited an amplified TH2 cytokine response (IL-4 and IL-13; p=0.0117, p=0.0004), which was attenuated by MSC-EVs (p=0.0013, p=0.0045). This was accompanied by increased activated CD4+ T cell infiltration (p=0.0022), more specifically CD4+ tissue resident memory cells (p < 0.0001) responsible for producing these cytokines, mitigated by MSC-EVs (p=0.0251, p=0.0358). HYRX HDM also demonstrated increased IL-6+ and TNFα+ alveolar macrophages (AMFs) compared to asthma controls (p=0.0181), that was abrogated by MSC-EVs (p=0.0054). HYRX HDM resulted in exaggerated airway hyper-responsiveness (AHR) (Rrs, p< 0.0001, Rn, p< 0.0001) compared to asthma which was mitigated by MSC-EVs (Rrs, p=0.034, Rn, p=0.041). AMFs were depleted in HYRX HDM and asthma controls and demonstrated an alternated phenotype (SiglecFlo, CD11chi, and CD11b+). PN14 AMFs after HYRX revealed an altered phenotype (SiglecFlo and CD11chi) and transcriptomic profile with upregulation of NFκB and TNFα pathways, also exhibited pro-inflammatory function ex vivo.

Conclusion(s): HYRX exacerbates the airway inflammation and AHR of asthma and MSC-EVs can attenuate these effects. HYRX modulates the phenotype, transcriptome, and functionality of AMFs suggestive of long-term immune dysregulation, which has long-term consequences for future lung challenges.

HYRX Exacerbates Airway Inflammation and Hyper-Responsiveness of Asthma, Attenuated by MSC-EVs
Figure 1. HYRX Exacerbates Airway Inflammation and Hyper-Responsiveness of Asthma, Attenuated by MSC-EVs. (A) HYRX amplified TH2 cytokine response (IL-4 and IL-13; p=0.0117, p=0.0004) in asthma (HDM), abrogated by early MSC-EVs (p=0.0013, p=0.0045). (B) HYRX exaggerated airway hyper-responsiveness in asthma (HDM) as measured by airway resistance (Rn) (p < 0.0001) in response to a methacholine challenge on PN28, mitigated by early and late MSC-EVs (p=0.041). Data representative of at least 3 independent experiments (n = 10-18 mice per group). Two-way ANOVA and Tukey’s multiple comparisons test were used for analysis. *p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001.

HYRX Modulates The Phenotype & Transcriptomic Profile of Alveolar Macrophages
Figure 2. HYRX Modulates The Phenotype & Transcriptomic Profile of Alveolar Macrophages. (A) PN14 AMFs after HYRX exposure results in an altered phenotype characterized by SiglecFlo, CD11chi and CD11b+. (B) PN14 AMFs after HYRX exposure also demonstrated an altered transcriptomic profile with notable upregulation of NFκB and TNFα pathways.