Altered alveolar cell signature in pre- and post-natal Trisomy 21 lung

Abstract

Rationale: Pulmonary and cardiovascular disorders result in 75% of the mortality observed in individuals with Down Syndrome (DS). However, little is known about the pulmonary anomalies observed in DS, as they are often considered a secondary condition to congenital heart defects. However, we and others have demonstrated that lungs from patients with trisomy 21 (T21) may present alveolar abnormalities, such as pulmonary alveolar hypoplasia, regardless of congenital heart disease. Therefore, the etiology of alveolar defects in T21 lungs remains elusive. The aim of our study is to define the molecular and cellular defects underlying alveolar defects in T21 developing lungs. Methods: Single cell RNA sequencing data was generated from 5 T21 and 4 non-T21 human fetal lungs (18 weeks gestation). T21 and non-T21 human fetal lung tissues (aged 18 to 22 weeks gestation), and postnatal human lung tissues from 2 months to 6 years old were processed to compare and determine the localization and expression of alveolar cells and their markers by RT-qPCR, fluorescence in situ hybridization (FISH) and immunofluorescent staining (IF). Results: Our single cell data showed an increase in the proportion of mature fetal AT2 cells in T21 as compared to non-T21 samples, whereas a decrease was observed in the intermediate and progenitor cell populations. When comparing fetal T21 to non-T21 samples, RT-qPCR results demonstrated significantly increased expression of both alveolar type II markers (SFTPD, ABCA3, SCGB3A2, LAMP3) and the alveolar type I marker AGER. Furthermore, FISH showed a significant increase in SFTPC and SFTPB in fetal T21 lungs. Conversely, when comparing postnatal T21 to non-T21 samples, RT-qPCR results demonstrated reduced expression of alveolar type II markers (SFTPB, SFTPD, ABCA3, SCGB3A2, LAMP3) and alveolar type I markers (HOPX, AGER, PODOPLANIN). Our IF staining in postnatal T21 vs non-T21 showed a significant increase in the number KRT8 and KRT8+/SFTPC+ cells, markers of an intermediate progenitor cell population, accompanied by a decrease in proliferating AT2 cells (SFTPC+/Ki67+). Conclusion: While our single cell data, RT-qPCR, FISH and IF results show an accelerated maturation during T21 lung fetal pre-alveolar development, postnatal T21 lungs display a decrease in mature AT2 cell numbers. This could likely be due to an accelerated maturation early on in development, that suppresses proper proliferation necessary to expand the pool of AT2 cells to a normal range. This suppression seems to persist into the postnatal period. 3R21HL165411-02S1. NIH/NHLBI Offce of The Director, National Institutes of Health (OD) R01HL155104 (SD). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.