Epithelial outgrowth through mesenchymal rings drives lung alveologenesis

Bronchopulmonary dysplasia with pulmonary hypertension associates with semaphorin signaling loss and functionally decreased FOXF1 expression

Lung injury in preterm infants leads to structural and functional respiratory deficits, with a risk for bronchopulmonary dysplasia (BPD) that in its most severe form is accompanied by pulmonary hypertension (PH). To identify potential cellular and molecular drivers of BPD in humans, we performed single-cell RNA sequencing of preterm infant lungs with evolving BPD and BPD + PH compared to term infants. Examination of endothelial cells reveals a unique, aberrant capillary cell-state in BPD + PH defined by ANKRD1 expression. Within the alveolar parenchyma in infants with BPD/BPD + PH, predictive signaling analysis identifies surprising deficits in the semaphorin guidance-cue pathway, with decreased expression of pro-angiogenic transcription factor FOXF1. Loss of semaphorin signaling is replicated in a murine BPD model and in humans with causal FOXF1 mutations for alveolar capillary dysplasia (ACDMPV), suggesting a mechanistic link between developmental programs underlying BPD and ACDMPV and uncovering a critical role for semaphorin signaling in normal lung development.

Epithelial Dysfunction in Congenital Diaphragmatic Hernia: Mechanisms, Models and Emerging Therapies

Congenital diaphragmatic hernia (CDH) is a complex disorder whereby improper formation of the diaphragm allows herniation of the internal organs into the thoracic cavity, resulting in pulmonary hypoplasia among other complications. Although epithelial dysfunction is central to CDH pathology, relatively little attention has been paid to the underlying mechanisms orchestrating epithelial malfunction. Proinflammatory signaling downstream of impaired mechanotransduction due to in utero lung compression has been elucidated to drive epithelial cell phenotypes. This has been illustrated by a reduction in nuclear YAP and the upregulation of NF-kB in CDH models. In this review, we draw from recent findings using emerging technologies to examine epithelial cell mechanisms in CDH and discuss the role of compression as a central and, crucially, sufficient driver of CDH phenotypes. In recognition of the limitations of using genetic knockout models to recapitulate such a heterogenic and etiologically complicated disease, we discuss alternative models such as the established nitrofen rat model, air-liquid interface (ALI) cultures, organoids and ex vivo lung explants. Throughout, we acknowledge the importance of involving mechanical compression in the modeling of CDH in order to faithfully recapitulate the disease. Finally, we explore novel therapeutic strategies from stem cell and regenerative therapies to precision medicine and the importance of defining CDH endotypes in order to guide treatments.