Neonatal hyperoxia induces activated pulmonary cellular states and sex-dependent transcriptomic changes in a model of experimental bronchopulmonary dysplasia

Hyperoxia disrupts lung development in mice and causes bronchopulmonary dysplasia (BPD) in neonates. To investigate sex-dependent molecular and cellular programming involved in hyperoxia, we surveyed the mouse lung using single cell RNA sequencing (scRNA-seq), and validated our findings in human neonatal lung cells in vitro. Hyperoxia-induced inflammation in alveolar type (AT) 2 cells gave rise to damage-associated transient progenitors (DATPs). It also induced a new subpopulation of AT1 cells with reduced expression of growth factors normally secreted by AT1 cells, but increased mitochondrial gene expression. Female alveolar epithelial cells had less EMT and pulmonary fibrosis signaling in hyperoxia. In the endothelium, expansion of Car4+ EC (Cap2) was seen in hyperoxia along with an emergent subpopulation of Cap2 with repressed VEGF signaling. This regenerative response was increased in females exposed to hyperoxia. Mesenchymal cells had inflammatory signatures in hyperoxia, with a new distal interstitial fibroblast subcluster characterized by repressed lipid biosynthesis and a transcriptomic signature resembling myofibroblasts. Hyperoxia-induced gene expression signatures in human neonatal fibroblasts and alveolar epithelial cells in vitro resembled mouse scRNA-seq data. These findings suggest that neonatal exposure to hyperoxia programs distinct sex-specific stem cell progenitor and cellular reparative responses that underpin lung remodeling in BPD.

The cellular dynamics of early and transitional human breast milk

Breast milk (BM) is a complex fluid containing factors essential for infant nutrition and immunity. Breastfeeding has been shown to be protective against infections and other immune-mediated diseases during the lactation period and beyond in later childhood. This suggests that BM also imprints the neonatal immune system and influences long-term health. BM also contains populations of maternal-derived cells. Which factors in BM that are important for neonatal health and how they change during lactation have not been well-defined. In this study, we used a single-cell transcriptomic approach to identify and define cell types of early and transitional milk. We collected BM samples from mothers of infants 2–5 days (early milk) and 8–12 days (transitional milk) after delivery. We applied single-cell RNA sequencing on over 154,000 BM-derived cells. We identified 25 transcriptionally distinct populations of cells in the BM. As expected, the most abundant cells in BM were mammary epithelial cells and macrophages. Monocytes, T cells, dendritic cells, and neutrophils were also present and had a higher frequency in week 2, suggesting that some immune cells may remain abundant in the early days of lactation and slowly decline as milk matures. We also detected a small number of stem and progenitor, natural killer and B cells in the BM at a higher frequency in week 1. This work provides an atlas of the cellular component in human milk at two timepoints of lactation. In addition to cell identity and frequencies, we have also uncovered unique molecular pathways that are activated in BM cells. This work will lay the foundation for future studies of how these cells influence neonatal health.

Supported by funding from Children's Mercy Kansas City

Novel mutation in TNPO3 causes congenital limb-girdle myopathy with slow progression

Objective

We report a second family with autosomal dominant transportinopathy presenting with congenital or early-onset myopathy and slow progression, causing proximal and less pronounced distal muscle weakness.

Methods

Patients had clinical examinations, muscle MRI, EMG, and muscle biopsy studies. The MYOcap gene panel was used to identify the gene defect in the family. Muscle biopsies were used for histopathologic and protein expression studies, and TNPO3 constructs were used to study the effect of the mutations in transfected cells.

Results

We identified a novel heterozygous mutation, c.2757delC, in the last part of the transportin-3 (TNPO3) gene in the affected family members. The mutation causes an almost identical frameshift affecting the stop codon and elongating the C-term protein product of the TNPO3 transcript, as was previously reported in the first large Spanish-Italian LGMD1F kindred. TNPO3 protein was increased in the patient muscle and accumulated in the subsarcolemmal and perinuclear areas. At least one of the cargo proteins, the splicing factor SRRM2 was normally located in the nucleus. Transiently transfected mutant TNPO3 constructs failed to localize to cytoplasmic annulate lamellae pore complexes in cells.

Conclusions

We report the clinical, molecular genetic, and histopathologic features of the second transportinopathy family. The variability of the clinical phenotype together with histopathologic findings suggests that several molecular pathways may be involved in the disease pathomechanism, such as nucleocytoplasmic shuttling, protein aggregation, and defective protein turnover.

Association of poly I:C RNA and plasmid DNA onto MnO nanorods mediated by PAMAM

In this study, manganese oxide (MnO) nanorods and its association with polyamidoamine dendrimer (PAMAM) and macromolecular RNA were analyzed. Because manganese is found naturally in cells and tissues and binds proteins and nucleic acids, nanomaterials derived from manganese, such as first generation MnO, may have potential as a biocompatible delivery agent for therapeutic or diagnostic biomedical applications. Nucleic acids have a powerful influence over cell processes, such as gene transcription and RNA processing; however, macromolecular RNA is particularly difficult to stabilize as a nanoparticle and to transport across cell membranes while maintaining structure and function. PAMAM is a cationic, branching dendrimer known to form strong complexes with nucleic acids and to protect them from degradation and is also considered to be a cell penetrating material. There is currently much interest in polyinosinic:polycytidylic RNA (poly I:C) because of its potent and specific immunogenic properties and as a solo or combination therapy. In order to address this potential, here, as a first step, we used PAMAM to attach poly I:C onto MnO nanorods. Morphology of the MnO nanorods was examined by field emission scanning electron microscopy (FESEM) and their composition by energy dispersive X-ray microanalysis (EDX). Evidence was generated for RNA:PAMAM:MnO nanorod binding by a gel shift assay using gel electrophoresis, a sedimentation assay using UV spectroscopy, and zeta potential shifts using dynamic laser light scattering. The data suggest that RNA was successfully attached to the MnO nanorods using PAMAM, and this suggestion was supported by direct visualization of the ternary complexes with FESEM characterizations. In order to confirm that the associations were biocompatible and taken up by cells, MTT assays were carried out to assess the metabolic activity of HeLa cells after incubation with the complexes and appropriate controls. Subsequently, we performed transfection assays using PAMAM:MnO complexes with pDNA encoding a green fluorescent protein reporter gene instead of RNA. The results suggest that the complexes had minimal impact on metabolic activity and were readily taken up by cells, and the fluorescent protein was expressed. From the evidence, we conclude that complexes of PAMAM:MnO interact with nucleic acids to form associations that are well-tolerated and readily taken up by cells.