Newborns with congenital diaphragmatic hernia show hyperactive but inefficient mitochondria in endothelial cells

Congenital diaphragmatic hernia, or CDH, has long been framed as a problem of space: a hole in the diaphragm allows abdominal organs to crowd into the chest, and the lungs simply do not have room to grow. Yet a growing body of evidence suggests that the story is far more cellular than that. In a new study published in Pediatric Research, Emrick and colleagues report that endothelial cells taken from newborns with CDH carry a distinctive mitochondrial signature, one marked by metabolic activation, reduced bioenergetic efficiency, oxidative stress, and structural remodeling of the mitochondrial network itself. The finding adds a striking new dimension to the biology of a disease that, despite major advances in prenatal risk stratification, fetal intervention, neonatal intensive care, and extracorporeal support, still sees pulmonary hypoplasia and pulmonary hypertension determine much of its morbidity and mortality.

The research team worked with human umbilical vein endothelial cells, known as HUVECs, obtained from newborns with CDH and from healthy controls. Because these cells are collected at birth, they offer a rare window into the fetal biology of the disease, largely free of the confounders that complicate postnatal lung tissue studies, such as prolonged mechanical ventilation, oxygen exposure, vasoactive drug treatment, and critical illness. The investigators combined extracellular flux analysis, which measures oxygen consumption and glycolytic activity in living cells, with measurements of reactive oxygen species, mitochondrial membrane potential, mitochondrial DNA copy number, and mitochondrial morphology assessed by confocal microscopy.

The central observation is genuinely counterintuitive. Mitochondrial respiration in the CDH endothelial cells was not suppressed, as one might expect in a diseased tissue, but increased. Basal respiration, maximal respiration, and spare respiratory capacity were all elevated compared with controls. Yet this greater respiratory activity came at a cost: the cells showed increased proton leak across the inner mitochondrial membrane and reduced ATP coupling efficiency, meaning that a larger fraction of the energy stored in nutrients was dissipated as heat rather than captured in the cellular energy currency. Basal glycolytic activity was also increased, alongside elevated mitochondrial superoxide and cellular reactive oxygen species. Rather than the conventional metabolic switch from oxidative phosphorylation toward glycolysis, the CDH cells appeared to ramp up both pathways simultaneously while extracting energy from respiration less efficiently.

This distinction may matter biologically. Much of the conceptual framework for metabolic dysfunction in pulmonary hypertension comes from adult pulmonary arterial hypertension, where enhanced glycolysis and impaired oxidative phosphorylation are prominent features. The phenotype described by Emrick and colleagues is different in kind: oxidative respiratory capacity is preserved and even augmented, but at the price of increased leak, oxidative stress, and impaired coupling. The authors of the accompanying commentary suggest this may reflect the fundamentally different developmental setting of CDH. The pulmonary circulation in these infants does not transition from a previously normal mature state into vascular disease; it develops abnormally in utero, under conditions of compression, altered oxygen tension, and disturbed signaling.

Endothelial dysfunction in CDH is not a new concept, but the current study supplies a new metabolic explanation for it. In fetal sheep with experimental CDH, Acker and colleagues previously demonstrated markedly impaired pulmonary artery endothelial cell proliferation and tube formation, together with reduced populations of highly proliferative endothelial cells and increased superoxide production. More recently, Kool and colleagues identified reduced endothelial expression of the transcription factor KLF4 and disturbed endothelial–perivascular signaling in experimental CDH, reinforcing the idea that abnormal vascular development is established early and involves intrinsic endothelial programs rather than being purely a consequence of mechanical compression. The present human data complement these observations by suggesting that mitochondrial dysfunction and redox imbalance may be part of the cellular machinery underlying this abnormal endothelial phenotype.

The mitochondrial morphology findings are equally intriguing. Despite reduced MitoTracker Green fluorescence, a dye-based indicator of mitochondrial mass, mitochondrial DNA copy number was preserved, while confocal microscopy revealed a more branched and widely distributed mitochondrial network in the CDH cells. This pattern argues against a simple reduction in mitochondrial abundance and instead points to qualitative remodeling. Such remodeling could initially be adaptive: increased mitochondrial connectivity may help cells maintain ATP production and buffer local mitochondrial damage under sustained stress. However, persistent network remodeling in an environment of elevated reactive oxygen species production could eventually become maladaptive, perpetuating oxidative injury and impairing endothelial function over time.

Perhaps the most clinically interesting observation concerns the relationship between mitochondrial function and disease severity. Higher maximal respiration was associated with prolonged hospitalization and/or mortality, and showed a trend toward an association with lower prenatal observed-to-expected total fetal lung volume, a standard imaging-based measure of disease severity. These analyses are necessarily exploratory given the sample size, but they raise the possibility that the biological severity of CDH leaves a measurable metabolic imprint on endothelial cells already at birth. If confirmed in larger cohorts, such findings may eventually prove relevant not only mechanistically but also for phenotyping a disease in which pulmonary hypertension is remarkably heterogeneous and current management strategies acknowledge that one size does not fit all.

The results also fit into a broader shift in CDH research toward understanding intrinsic cellular and molecular defects across different lung compartments. Patient-derived airway basal cells have revealed persistent pro-inflammatory epithelial abnormalities in CDH, while recent analyses of human hypoplastic lungs demonstrated enrichment of pulmonary macrophages both before and after birth. Viewed together, these observations suggest that epithelial, immune, and vascular abnormalities may not represent isolated phenomena. Mitochondrial reactive oxygen species can modify inflammatory and redox-sensitive signaling pathways, while inflammatory mediators can themselves alter mitochondrial function. It is therefore tempting to speculate that metabolic stress, inflammation, and impaired developmental signaling form interconnected rather than independent disease pathways in the hypoplastic CDH lung, with mitochondria potentially serving as a common node linking them.

Two limitations deserve particular emphasis. First, HUVECs are not pulmonary microvascular endothelial cells. They offer an unusually valuable source of primary, patient-specific fetal endothelial cells, but the pulmonary endothelium develops within a highly specific mechanical, oxygen-dependent, and paracrine environment that umbilical vessels do not fully recapitulate. The current results should therefore be interpreted primarily as evidence of a systemic endothelial phenotype associated with CDH, with pulmonary relevance that remains to be demonstrated directly. Validation in human pulmonary vascular tissue, where feasible, and in complementary experimental models will be important next steps. Second, the study establishes an association rather than causality. Increased respiratory capacity may contribute to endothelial dysfunction, but it could equally represent an adaptive response to increased cellular stress or energy demand. The relatively small sample size also limits adjustment for disease severity, maternal comorbidities, and other potential confounders. The most informative next step may therefore be functional intervention: if normalization of mitochondrial reactive oxygen species, respiratory coupling, or mitochondrial dynamics can restore proliferation, migration, or angiogenic capacity in CDH endothelial cells, the argument for a mechanistic role of mitochondrial dysfunction would become considerably stronger.

The translational implications are attractive but should remain appropriately measured. Current treatment of CDH-associated pulmonary hypertension largely targets vascular tone after birth, and clinical responses remain variable. Emrick and colleagues instead identify a cellular metabolic phenotype that may have its origins much earlier in pulmonary development. This does not yet establish mitochondria as a therapeutic target, but it shifts attention toward the developmental biology that precedes postnatal pulmonary hypertension. Ultimately, the importance of this study lies less in proposing mitochondria as the single cause of CDH-associated vascular disease than in adding another layer to an increasingly integrated model of CDH pathogenesis, in which disturbed developmental signaling, abnormal cellular differentiation, inflammation, impaired angiogenesis, and vascular remodeling converge. By demonstrating a metabolically activated yet inefficient endothelial phenotype in primary human cells, the researchers provide a compelling new reason to reconsider the biological origins of vascular dysfunction in CDH, and a promising direction for the studies that must now follow.

Subject of Research: Mitochondrial dysfunction in endothelial cells from newborns with congenital diaphragmatic hernia

Article Title: Endothelial metabolism in CDH: mitochondrial dysfunction as a new piece of the puzzle

Article References: Wagner, R. (2026). Endothelial metabolism in CDH: mitochondrial dysfunction as a new piece of the puzzle. Pediatric Research. https://doi.org/10.1038/s41390-026-05569-1

Image Credits: AI Generated

DOI: 10.1038/s41390-026-05569-1

Keywords: congenital diaphragmatic hernia, endothelial cells, mitochondria, pulmonary hypertension, reactive oxygen species, oxidative phosphorylation, glycolysis, HUVECs, lung development, mitochondrial dynamics, pediatric research, bioenergetics