Inhibition of retinoic acid signaling induces aberrant pericyte coverage and differentiation resulting in vascular defects in congenital diaphragmatic hernia

Abstract

The mortality and morbidity of patients with congenital diaphragmatic hernia (CDH) is primarily caused by treatment-resistant, persistent pulmonary hypertension. Structural vascular changes, exemplified by extensive muscularization, are already present early in gestation, but the origin of these abnormalities is unknown. Understanding the origin of the vascular defects is important to improve treatment modalities. Here, we show that the distribution of pericytes is different and may thereby potentially initiate the vascular pathology in CDH. Transient inhibition of retinoic acid (RA) signaling early during pregnancy, the basis of the CDH mouse model, led to an increase in the number of pericytes, thereby affecting the angiogenic potential of pericytes in the fetuses. Pericytes of CDH lungs showed reduced proliferation and an increased ACTA2 expression, which indicates that these pericytes are more contractile than in control lung pericytes. This resulted in increased pericyte coverage of pulmonary vessels and reduced expansion of the capillary bed, the earliest pathological sign of the structural changes in CDH. Furthermore, the pericytes had reduced and altered collagen IV deposition in CDH, pointing to a loss of basal membrane integrity between pericytes and endothelial cells. Inhibition of RA signaling in vitro resulted in reduced migration of pericytes, reduced angiogenesis, and loss of collagen IV expression. Importantly, we confirmed our findings in lungs of human CDH patient samples. In summary, inhibition of RA signaling affects the lung pericyte population, leading to increased contractility, reduced pulmonary angiogenesis, and aberrant lung development, as observed in CDH.

Human induced pluripotent stem cell-derived lung organoids in an ex vivo model of the congenital diaphragmatic hernia fetal lung

“…CDH is a perplexing congenital lung anomaly whose exact cause remains unknown. 39 Although somatic mutations in GATA4 and FOG2, among others, have been implicated in less than 10% of CDH patients, 15,16,40 the etiology of CDH is heterogeneous and likely polygenic in the majority of cases. 12 Regardless, the downstream result of the near-term CDH fetal lung is progressive hypoplasia involving both proximal and distal airways as well as abnormalities within the adjacent mesenchyme and airway smooth muscle.…”

“…CDH is a perplexing congenital lung anomaly whose exact cause remains unknown 39 . Although somatic mutations in GATA4 and FOG2 , among others, have been implicated in less than 10% of CDH patients, 15,16,40 the etiology of CDH is heterogeneous and likely polygenic in the majority of cases 12 .…”

Recent advances in our understanding of the mechanisms of lung alveolarization and bronchopulmonary dysplasia

“…A recent systematic review of randomized trials supported vitamin A supplementation for the prevention of BPD (173), and a randomized controlled trial to evaluate the use of enteral vitamin A for reducing the severity of BPD has been proposed (479). Recent evidence has also been provided for a role for vitamin A signaling in vascular development, where inhibition of retinoic acid signaling induced aberrant pericyte coverage and differentiation, which was thought to contribute to the disease mechanisms operative in CDH (275). In contrast to vitamins A and D, studies on vitamin C have been restricted to calls for further studies on the utility of vitamin C supplementation during pregnancy to improve fetal lung development in smoking mothers (366,381).…”

Retinoic Acid: A Key Regulator of Lung Development

“…Simultaneously, RA acts autocrinally controlling endothelial cell proliferation and tube formation [108]. More recently, it has been demonstrated that RA signaling is involved in pericyte migration, angiogenesis, and collagen IV expression [141].…”