456 - Arrested alveolar organogenesis in a newborn mouse inflammation model: protection by the interleukin (IL)-1 receptor antagonist rytvela

Publication Number: 2444.456

David M.. Olson, University of Alberta Faculty of Medicine and Dentistry, Edmonton, AB, Canada; Yueyang Wang, Harbin Medical University, Harbin, Heilongjiang, China (People's Republic); Kazumasa Fuwa, Nihon University School of Medicine, Itabashi-ku, Tokyo, Japan; Carla Sosa Alvarado, University of Alberta, Edmonton, AB, Canada; Alishba Humayun, University of Alberta Faculty of Medicine and Dentistry, Edmonton, AB, Canada; Kelycia B. Leimert, University of Alberta Faculty of Medicine and Dentistry, Edmonton, AB, Canada; Sylvain Chemtob, CHU Sainte Justine, Montreal, PQ, Canada

Background: Inflammation is associated with preterm babies arising from maternal/fetal infection or from NICU exposures such as mechanical ventilation, infection, and supplemental oxygen. Elevated levels of interleukin (IL)-1b can be detected in these neonates who subsequently develop bronchopulmonary dysplasia. The treatments are limited to antibiotics and glucocorticoids, but they come with risks, and there are no reliable newborn rodent models with chronic inflammation for testing new treatments.

Objective: The objective was to develop a mouse newborn model of inflammation based on low dose administration of the bacterial mimic, lipopolysaccharide (LPS), that causes arrested lung development at postnatal day (PND)7 and test rytvela, an allosteric modulator of the IL-1 receptor, in mitigating lung disease.

Design/Methods: Pregnant CD-1 mice were administered (i.p.) saline (n=9) or LPS (4ug in 100 uL saline, n=27) on gestational days 16 & 17, and newborns were treated with saline or LPS (3mg/kg, i.p.) on PNDs 3 & 5. Rytvela (1mg/kg/12h) in 20 uL saline was administered over 48h to pups beginning on PND3. On PND7 pups were weighed and euthanized. Lungs were collected, frozen or fixed, and analyzed. The number and size of the lung alveoli were quantified after H&E staining using Image J and GraphPad Prism. Statistical analyses: 1- or 2-way ANOVA, p< 0.05.

Results: 48% of pups from LPS-treated dams were alive on PND1. They were significantly smaller than pups from saline-treated dams (1.56 +/-0.02g, n=82, vs. 1.77+/-0.02g, n=85, p< 0.05). 44% of pups alive on PND1 receiving LPS + saline died by P7, but rytvela administration to LPS-treated pups reduced mortality to 22% (p < 0.05). By PND7 all surviving pup whole body and lung weights were similar suggesting catchup growth. Pups from saline-treated dams with postnatal LPS+saline or rytvela (saline-LPS-saline or saline-LPS-rytvela) had no differences in their alveolar density (306+/-11 alveoli/mm^2, n=6, 316+/-10 alveoli/mm^2, n=6). But pups from LPS-LPS-saline treatment had reduced alveolar density (p < 0.001), but this was restored to normal with LPS-LPS-rytvela (260+/-8 alveoli/mm^2, n=5, vs. 299+/-9 alveoli/mm^2, n=6, p< 0.05). Rytvela treatment improved alveolarization by reducing the average alveolar size from 1187+/-50 um^2 in LPS-LSP-saline pups to 1001+/-28 um^2, n=6 (p < 0.05) in LPS-LPS-rytvela pups.

Conclusion(s): We have developed a novel pregnant and newborn mouse model of bacterial inflammation that arrests lung development. Treatment of the newborns with rytvela reverses the damage. Human clinical trials should begin as soon as possible.

Funding: CIHR, CSC, AI

Experimental model
Saline or LPS were administered to pregnant mouse dams on GD16 and 17 and again to newborn pups on PND3 and 5. Rytvela was administered from PND3 q12h for 48h. Lung tissues were collected on PND7.

Rytvela improves alveolar structure in neonatal mice subjected to maternal and postnatal LPS-induced inflammation
A. Alveolar density (alveoli/mm^2) at PND7 is reduced by maternal and neonatal LPS administration. Rytvela restores alveolar density (p < 0.05).
B. Average alveolar size (um^2) is increased due to LPS treatment. Rytvela restores alveolar size (p < 0.05)