Pulmonary Vascular Disease across the Life Span: A Call for Bridging Pediatric and Adult Cardiopulmonary Research and Care

Severity of preterm birth and the risk of pulmonary hypertension in childhood: A population-based cohort study in Sweden

BACKGROUND

Preterm birth (<37 completed gestational weeks) has been linked to pulmonary hypertension (PH), but the relationship to severity of preterm birth has not been studied.

OBJECTIVES

We investigated associations between extremely (<28 weeks), very (28-31 weeks), moderately (32-36 weeks) preterm birth, early-term birth (37-38 weeks) and later PH. Additionally, we explored associations between birthweight for gestational age and PH.

METHODS

This registry-based cohort study followed 3.1 million individuals born in Sweden (1987-2016) from 1 up to a maximum of 30 years of age. The outcome was diagnosis or death from PH in national health registers. Adjusted hazard ratios (HR) were estimated using Cox regression analysis. Unadjusted and confounder-adjusted incidence rate differences were also calculated.

RESULTS

Of 3,142,812 individuals, there were 543 cases of PH (1.2 per 100,000 person-years), 153 of which in individuals without malformations. Compared with individuals born at 39 weeks, adjusted HRs with 95% confidence interval (CI) for PH for extremely, moderately, and very preterm birth were 68.78 (95% CI 49.49, 95.57), 13.86 (95% CI 9.27, 20.72) and 3.42 (95% CI 2.46, 4.74), respectively, and for early-term birth 1.74 (1.31, 2.32). HRs were higher in subjects without malformations. There were 90 additional cases of PH per 100,000 person-years in the extremely preterm group (50 after excluding malformations). Very small for gestational age (below 2 SD from estimated birthweight for gestational age and sex) was also associated with increased risk of PH (adjusted HR 2.02, 95% CI 1.14, 3.57).

CONCLUSIONS

We found an inverse association between gestational age and later PH, but the incidence and absolute risks are low. The severity of preterm birth adds clinically relevant information to the assessment of cardiovascular risks in childhood.

Endothelial-to-mesenchymal transition: Pathogenesis and therapeutic targets for chronic pulmonary and vascular diseases

Endothelial-to-mesenchymal transition (EndoMT) is a process of transdifferentiation where endothelial cells gradually adopt the phenotypic characteristics of mesenchymal cells. This phenomenon was first discovered in embryonic heart development. The mechanisms underlying EndoMT are due to the activation of transforming growth factor-β, bone morphogenetic protein, Wingless/Integrated, or Notch signaling pathways. The EndoMT can be modulated by pathological processes, including inflammation, disturbed shear stress, vascular stiffness, and metabolic dysregulation. Recent studies have shown that EndoMT is implicated in the pathogenesis of chronic lung diseases, including pulmonary hypertension and lung fibrosis. Lung pathology of bronchopulmonary dysplasia can be mimicked in rodents exposed to hyperoxia as neonates. Although hyperoxic exposure reduces an endothelial cell marker platelet and endothelial cell adhesion molecule but increases a mesenchymal cell biomarker α-smooth muscle actin in vitro in human pulmonary endothelial cells, there is no direct evidence showing EndoMT in the development of bronchopulmonary dysplasia. Both pulmonary hypertension and lung fibrosis occur in long-term survivors with bronchopulmonary dysplasia. In this review, we discuss the EndoMT and its modulation by pathological processes. We then focus on the role of EndoMT in the pathogenesis of these chronic lung diseases, and discuss therapeutic approaches targeting the EndoMT using its negative regulators.