Bronchopulmonary dysplasia (BPD) remains the most prevalent long-term morbidity of surviving extremely preterm infants and is associated with significant health care utilization in infancy and beyond. Recent advances in neonatal care have resulted in improved survival of extremely low birth weight (ELBW) infants; however, the incidence of BPD has not been substantially impacted by novel interventions in this vulnerable population. The multifactorial cause of BPD requires a multi-pronged approach for prevention and treatment. New approaches in assisted ventilation, optimal nutrition, and pharmacologic interventions are currently being evaluated. The focus of this review is the current state of the evidence for pharmacotherapy in BPD. Promising future approaches in need of further study will also be reviewed.

The failing heart is characterized by elevated levels of reactive oxygen species. We have developed an animal model of heart failure induced by chemogenetic production of oxidative stress in the heart using a recombinant adeno-associated virus (AAV9) expressing yeast D-amino acid oxidase (DAAO) targeted to cardiac myocytes. When DAAO-infected animals are fed the DAAO substrate D-alanine, the enzyme generates hydrogen peroxide (H2O2) in the cardiac myocytes, leading to dilated cardiomyopathy. However, the underyling mechanisms of oxidative stress induced heart failure remain incompletely understood. Therefore, we investigated the effects of chronic oxidative stress on the cardiac transcriptome and metabolome. Rats infected with recombinant cardiotropic AAV9 expressing DAAO or control AAV9 were treated for 7 weeks with D-alanine to stimulate chemogenetic H2O2 production by DAAO and generate dilated cardiomyopathy. After hemodynamic assessment, left and right ventricular tissues were processed for RNA sequencing and metabolomic profiling. DAAO induced dilated cardiomyopathy was characterized by marked changes in the cardiac transcriptome and metabolome both in the left and right ventricle. Downregulated transcripts related to energy metabolism and mitochondrial function, accompanied by striking alterations in metabolites involved in cardiac energetics redox homeostasis, and amino acid metabolism. Upregulated transcripts involved cytoskeletal organization and extracellular matrix. Finally, we noted increased metabolite levels of antioxidants glutathione and ascorbate. These findings provide evidence that chemogenetic generation of oxidative stress leads to a robust heart failure model with distinct transcriptomic and metabolomic signatures and set the basis for understanding the underlining pathophysiology of chronic oxidative stress in the heart.

Echocardiography is the gold standard non-invasive technique to diagnose pulmonary hypertension. It is also an important modality used to monitor disease progression and response to treatment in patients with pulmonary hypertension. Surprisingly, only few studies have been conducted to validate and standardize echocardiographic parameters in experimental animal models of pulmonary hypertension. We sought to define cut-off values for both invasive and non-invasive measures of pulmonary hemodynamics and right ventricular hypertrophy that would reliably diagnose pulmonary hypertension in three different rat models. The study was designed in two phases: (1) a derivation phase to establish the cut-off values for invasive measures of right ventricular systolic pressure, Fulton's index (right ventricular weight/left ventricle + septum weight), right ventricular to body weight ratio, and non-invasive echocardiographic measures of pulmonary arterial acceleration time, pulmonary arterial acceleration time to ejection time ratio and right ventricular wall thickness in diastole in the hypoxic and monocrotaline rat models of pulmonary hypertension and (2) a validation phase to test the performance of the cut-off values in predicting pulmonary hypertension in an independent cohort of rats with Sugen/hypoxia-induced pulmonary hypertension. Our study demonstrates that right ventricular systolic pressure ≥35.5 mmHg and Fulton's Index ≥0.34 are highly sensitive (>94%) and specific (>91%) cut-offs to distinguish animals with pulmonary hypertension from controls. When pulmonary arterial acceleration time/ejection time and right ventricular wall thickness in diastole were both measured, a result of either pulmonary arterial acceleration time/ejection time ≤0.25 or right ventricular wall thickness in diastole ≥1.03 mm detected right ventricular systolic pressure ≥35.5 mmHg or Fulton's Index ≥0.34 with a sensitivity of 88% and specificity of 100%. With properly validated non-invasive echocardiography measures of right ventricular performance in rats that accurately predict invasive measures of pulmonary hemodynamics, future studies can now utilize these markers to test the efficacy of different treatments with preclinical therapeutic modeling.

Pulmonary hypertension (PH) is associated with meta-inflammation related to obesity but the role of adipose tissue in PH pathogenesis is unknown. We hypothesized that adipose tissue-derived metabolic regulators are altered in human and experimental PH. We measured circulating levels of fatty acid binding protein 4 (FABP-4), fibroblast growth factor -21 (FGF-21), adiponectin, and the mRNA levels of FABP-4, FGF-21, and peroxisome proliferator-activated receptor γ (PPARγ) in lung tissue of patients with idiopathic PH and healthy controls. We also evaluated lung and adipose tissue expression of these mediators in the three most commonly used experimental rodent models of pulmonary hypertension. Circulating levels of FABP-4, FGF-21, and adiponectin were significantly elevated in PH patients compared to controls and the mRNA levels of these regulators and PPARγ were also significantly increased in human PH lungs and in the lungs of rats with experimental PH compared to controls. These findings were coupled with increased levels of adipose tissue mRNA of genes related to glucose uptake, glycolysis, tricarboxylic acid cycle, and fatty acid oxidation in experimental PH. Our results support that metabolic alterations in human PH are recapitulated in rodent models of the disease and suggest that adipose tissue may contribute to PH pathogenesis.

Introduction The goal of this study was to define the kinetics of glucose transport from maternal blood to placenta to fetus using real time imaging. Methods Positron emission tomography (PET) imaging of the glucose tracer [18F]fluorodeoxyglucose (FDG) was used to temporally and spatially define, in vivo, the kinetics of glucose transport from maternal blood into placentae and fetuses, in the late gestational gravid rat. Computed tomography (CT), with intravenous contrast, co-registered to the PET images allowed anatomic differentiation of placentae from fetal and maternal tissues. Results FDG was rapidly taken up by placentae and subsequently appeared in fetuses with minimal temporal lag. FDG standardized uptake values in placentae and fetuses approached that of maternal brain. In both anesthetized and awake dams, one quarter of the administered FDG ultimately was accrued in the collective fetuses and placentae. Accordingly, kinetic modeling demonstrated that the placentae had very high avidity for FDG, 2-fold greater than that of the fetus and maternal brain, when accounting for the fact that fetal FDG necessarily must first be taken up by placentae. Consistent with this, placental expression of glucose transporter 1 exceeded that of all other tissues. Discussion Fetal and placental tissues place a substantial glucose metabolic burden on the mother, owing to very high avidity of placentae for glucose coupled with the large relative mass of fetal and placental tissues. Conclusions The placenta has a tremendous capacity to uptake and transport glucose. PET/CT imaging is an ideal means to study metabolite transport kinetics in the fetoplacental unit.

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Pulmonary hypertension (PH) is a serious disease with pulmonary arterial fibrotic remodeling and limited responsiveness to vasodilators. Our data suggest that mild acidosis induced by carbonic anhydrase inhibition could ameliorate PH, but the vascular mechanisms are unclear. We tested the hypothesis that carbonic anhydrase inhibition ameliorates PH by improving pulmonary vascular reactivity and relaxation mechanisms. Male Sprague-Dawley rats were either control normoxic (Nx), or injected with Sugen5416 (20mg/kg, sc) and subjected to hypoxia (9%O2) (Su+Hx), or Su+Hx treated with acetazolamide (ACTZ, 100mg/kg/day, in drinking water). After measuring the hemodynamics, right ventricular hypertrophy was assessed by Fulton's Index; vascular function was measured in pulmonary artery, aorta and mesenteric arteries; and pulmonary arteriolar remodeling was assessed in lung sections. Right ventricular systolic pressure and Fulton's Index were increased in Su+Hx and reduced in Su+Hx+ACTZ rats. Pulmonary artery contraction to KCl and phenylephrine were reduced in Su+Hx and improved in Su+Hx+ACTZ. Acetylcholine (ACh)-induced relaxation and nitrate/nitrite production were reduced in pulmonary artery of Su+Hx and improved in Su+Hx+ACTZ. ACh relaxation was blocked by nitric oxide (NO) synthase and guanylate cyclase inhibitors, supporting a role of NO-cGMP. Sodium nitroprusside (SNP)-induced relaxation was reduced in pulmonary artery of Su+Hx, and ACTZ enhanced relaxation to SNP. Contraction/relaxation were not different in aorta or mesenteric arteries of all groups. Pulmonary arterioles showed wall thickening in Su+Hx that was ameliorated in Su+Hx+ACTZ. Thus, amelioration of pulmonary hemodynamics during carbonic anhydrase inhibition involves improved pulmonary artery reactivity and NO-mediated relaxation, and may enhance responsiveness to vasodilator therapies in PH.

Introduction: Lower oxygen saturation targets in preterm infants have been associated with decreased incidence of bronchopulmonary dysplasia (BPD) but increased risk of pulmonary hypertension (PH). Studies have shown that targets of <90% are associated with higher incidence of PH, however data on the optimal saturation target >90% are lacking. In this study, we compared the rate of BPD and PH in two cohorts with saturation targets of 94-98% and 92-97%. We hypothesized that BPD rate would be lower and PH rate would be unchanged at the lower saturation target. Methods: We performed a retrospective cohort study comparing PH and BPD rates among two cohorts of infants born at ≤32 weeks gestation at Brigham and Women’s Hospital: cohort 1 with saturation target of 94-98% (n = 129, July 2017-July 2018), cohort 2 with saturation target of 92-97% (n = 124, July 2018-July 2019). PH was defined by echocardiographic evidence of systolic septal flattening or right ventricular pressure ≥35 mmHg (estimated by tricuspid regurgitant jet velocity or shunt velocity) at gestational age (GA) ≥36 weeks. Comparisons between groups were carried out by Chi-square test, t-test, and multivariable logistic regression. Results: Subjects had a GA of 23-32 weeks; 46% were female. Groups did not differ with respect to GA, sex, or birth weight. There was no difference in rate of PH (2.4% vs. 4.2%, p = 0.12) or BPD (25% vs. 20%, p = 0.31) between cohort 1 and cohort 2. Other clinical parameters were not different between groups, including presence of patent ductus arteriosus, presence of atrial septal defect, use of diuretics, or use of steroids. After controlling for GA, birth weight, sex, and diagnosis of BPD using logistic regression, there was no difference in rate of PH between groups (p = 0.47), but there was a positive association of BPD with PH (OR 3.45; 95% CI, 1.18-10.09; p = 0.02). Conclusions: A lower oxygen saturation target was not associated with a higher rate of PH or lower rate of BPD in preterm infants. The overall rate of PH was much lower than rates previously reported at saturation targets <90%. Given our low incidence of PH, and the lack of a significant difference in rate of PH between groups, a saturation target of 92-97% may be safe while also minimizing need for supplemental oxygen in this population.