Insufficient development of vessels and alveoli in lungs of infants with trisomy 18-Features of pulmonary histopathological findings from lung biopsy.

The aim of this study was to evaluate the features of pulmonary histopathological changes in cases of trisomy 18 complicated with congenital heart disease and pulmonary arterial hypertension. Twenty-eight patients with trisomy 18 underwent open lung biopsy at the time of primary operation in our hospital between 2008 and 2019. We compared these histopathological findings with those from previously described groups without trisomy 18. Mean age at primary cardiac surgery was 37 days (range, 9-69 days). According to the Heath-Edwards (HE) classification, 1, 8, 12, and 5 patients were graded as 0, 1, 2, and 3, respectively, whereas 2 patients were not classifiable due to medial defects in the small pulmonary arteries (MD). Four (14.3%) and 13 (46.4%) patients presented with MD and hypoplasia of the small pulmonary arteries (HS). Fifteen (53.6%) and 21 (75.0%) patients presented with alveolar hypoplasia (AH) and alveolar wall thickening (AT). MD, HS, and AH in trisomy 18 were present frequently, differing significantly from previous reports. These findings might be associated with congenital inadequate development of vessels and alveoli in the lung, contributing to a high risk of PAH in trisomy 18.

Improvement in fetal pulmonary hypertension and maturity after reversal of ductal constriction: prospective cohort study.

OBJECTIVES: To test the hypotheses that estimated mean pulmonary arterial pressure (MPAP) decreases and pulmonary vascular maturation, assessed by the ratio of pulmonary arterial flow acceleration time to ejection time (AT/ET ratio), increases after reversal of fetal ductus arteriosus constriction by reducing maternal intake of the causal agent (prostaglandin inhibitors, such as polyphenol-rich foods or non-steroidal anti-inflammatory drugs), and that these effects are independent of gestational age, which are inferences not yet demonstrated in the clinical setting. METHODS: This was a prospective cohort study comparing Doppler echocardiographic ductal flow dynamics, MPAP and pulmonary arterial flow AT/ET ratio in third-trimester fetuses (≥ 28 weeks' gestation) with ductus arteriosus constriction, at the time of diagnosis and after 2 weeks of reduced maternal intake of prostaglandin inhibitors either by suspending the use of pharmacological agents with potential for prostaglandin inhibition or by restricting the consumption of polyphenol-rich foods. MPAP was estimated using the Dabestani equation (MPAP = 90 - (0.62 × AT)), and pulmonary vascular maturity was assessed using the AT/ET ratio, according to reported validation studies. Student's t-test was used for comparison of variables at diagnosis with those after reversal of ductal constriction. Change in MPAP and pulmonary AT/ET ratio between the two assessments was compared with the expected change in the same gestational period in normal fetuses based on reference curves of MPAP and pulmonary AT/ET ratio constructed in normal fetuses from healthy pregnant women at 19-37 weeks' gestation, encompassing the same gestational age range as the study group (28-37 weeks). RESULTS: Seventy pregnancies with fetal ductus arteriosus constriction were included in the study. After 2 weeks of reduced maternal intake of prostaglandin inhibitors, normalization of mean systolic (change from 1.86 ± 0.34 m/s at diagnosis to 1.38 ± 0.41 m/s; P < 0.001) and diastolic (change from 0.41 ± 0.11 m/s to 0.21 ± 0.065 m/s; P < 0.001) ductal velocities and of mean pulsatility index (change from 1.99 ± 0.20 to 2.55 ± 0.42; P < 0.001) was demonstrated. MPAP decreased between the assessments (change from 66.7 ± 6.90 mmHg at diagnosis to 54.5 ± 6.70 mmHg after 2 weeks; P < 0.001) and mean pulmonary AT/ET ratio increased (change from 0.20 ± 0.06 to 0.33 ± 0.07; P < 0.001). Change in MPAP between diagnosis and after 2 weeks of reduced maternal intake of prostaglandin inhibitors was -12.2 ± 0.30 mmHg, which was 5.3-times higher than that in 305 normal fetuses over 2 weeks during the same gestational period (-2.3 ± 0.19 mmHg) (P < 0.001), and change in pulmonary AT/ET ratio between the two assessments was 0.13 ± 0.08, which was 8.7-times higher than that in normal fetuses in the same gestational period (0.015 ± 0.08) (P < 0.001). CONCLUSIONS: Resolution of fetal ductal constriction is followed by a fall in MPAP and by an increase in pulmonary vascular maturity, to a significantly greater degree than is observed in normal fetuses in the same gestational-age period. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Arterial duct stent versus surgical shunt for patients with duct-dependent pulmonary circulation: a meta-analysis.

BACKGROUND: Both systemic-pulmonary shunt and arterial duct stent could be the palliation of duct-dependent pulmonary circulation. We aimed to compare the safety and efficacy of the two approaches. METHODS: The PubMed, EMBASE, and Cochrane Library databases were searched through December 2019 for studies comparing stent implantation and surgical shunt in duct-dependent pulmonary circulation. The baseline characteristics included ventricle physiology and cardiac anomaly. The main outcomes were hospital stay and total mortality. Additional outcomes included procedural complications, intensive care unit (ICU) stay, pulmonary artery growth at follow-up, and other indexes. A random- or fixed-effects model was used to summarize the estimates of the mean difference (MD)/risk ratio (RR) with 95% confidence intervals (CIs). RESULTS: In total, 757 patients with duct-dependent pulmonary circulation from six studies were included. Pooled estimates of hospital stay (MD, - 4.83; 95% CI - 7.92 to - 1.74; p < 0.05), total mortality (RR 0.44; 95% CI 0.28-0.70; p < 0.05), complications (RR 0.49; 95% CI 0.30-0.81; p < 0.05) and ICU stay (MD, - 4.00; 95% CI - 5.96 to - 2.04; p < 0.05) favored the stent group. Significant differences were found in the proportions of patients with a single ventricle (RR 0.82; 95% CI 0.68-0.98; p < 0.05) or a double ventricle (RR 1.23; 95% CI 1.07-1.41; p < 0.05) between the stent and shunt groups. Additionally, pulmonary artery growth showed no significant differences between the two groups. CONCLUSION: Arterial duct stent appears to have not inferior outcomes of procedural complications, mortality, hospital and ICU stay, and pulmonary artery growth in selected patients compared with a surgical shunt. TRIAL REGISTRATION: CRD42019147672.

Implication of EZH2 in the Pro-Proliferative and Apoptosis-Resistant Phenotype of Pulmonary Artery Smooth Muscle Cells in PAH: A Transcriptomic and Proteomic Approach.

Pulmonary arterial hypertension (PAH) is a progressive disorder characterized by a sustained elevation of pulmonary artery (PA) pressure, right ventricular failure, and premature death. Enhanced proliferation and resistance to apoptosis (as seen in cancer cells) of PA smooth muscle cells (PASMCs) is a major pathological hallmark contributing to pulmonary vascular remodeling in PAH, for which current therapies have only limited effects. Emerging evidence points toward a critical role for Enhancer of Zeste Homolog 2 (EZH2) in cancer cell proliferation and survival. However, its role in PAH remains largely unknown. The aim of this study was to determine whether EZH2 represents a new factor critically involved in the abnormal phenotype of PAH-PASMCs. We found that EZH2 is overexpressed in human lung tissues and isolated PASMCs from PAH patients compared to controls as well as in two animal models mimicking the disease. Through loss- and gain-of-function approaches, we showed that EZH2 promotes PAH-PASMC proliferation and survival. By combining quantitative transcriptomic and proteomic approaches in PAH-PASMCs subjected or not to EZH2 knockdown, we found that inhibition of EZH2 downregulates many factors involved in cell-cycle progression, including E2F targets, and contributes to maintain energy production. Notably, we found that EZH2 promotes expression of several nuclear-encoded components of the mitochondrial translation machinery and tricarboxylic acid cycle genes. Overall, this study provides evidence that, by overexpressing EZH2, PAH-PASMCs remove the physiological breaks that normally restrain their proliferation and susceptibility to apoptosis and suggests that EZH2 or downstream factors may serve as therapeutic targets to combat pulmonary vascular remodeling.

NLRC3 inhibits PDGF-induced PASMCs proliferation via PI3K-mTOR pathway.

Few studies about nucleotide-oligomerization domain-like receptor subfamily C3 (NLRC3) in PASMCs have been conducted. This research aimed to investigate the role of NLRC3 on platelet-derived growth factor (PDGF)-induced proliferation of pulmonary artery smooth muscle cells (PASMCs) and its underlying mechanism. We found that the proliferation of PASMCs stimulated with PDGF decreased when phosphoinositide 3-kinase (PI3K) or mammalian target of rapamycin (mTOR) inhibitors pretreatment. Overexpression of NLRC3 inhibited the proliferation of PASMCs and the phosphorylation of PI3K and mTOR while knocking down NLRC3 reversed this effect. Targeted to PI3K or mTOR can also reverse the effect of NLRC3. Activation of PI3K increased the phosphorylation of mTOR while inhibition of PI3K reduced it. Our data suggest that PDGF can induce abnormal proliferation of PASMCs, and NLRC3 suppresses activation of the PI3K-mTOR signaling thus inhibits PASMCs proliferation. These findings unveiled the effect of NLRC3 as an inhibitor of the PI3K-mTOR pathway mediating protection against PASMCs proliferation.

Image-based scaling laws for somatic growth and pulmonary artery morphometry from infancy to adulthood.

Pulmonary artery (PA) morphometry has been extensively explored in adults, with particular focus on intra-acinar arteries. However, scaling law relationships for length and diameter of extensive preacinar PAs by age have not been previously reported for in vivo human data. To understand preacinar PA growth spanning children to adults, we performed morphometric analyses of all PAs visible in the computed tomography (CT) and magnetic resonance (MR) images from a healthy subject cohort [n = 16; age: 1-51 yr; body surface area (BSA): 0.49-2.01 m2]. Subject-specific anatomic PA models were constructed from CT and MR images, and morphometric information-diameter, length, tortuosity, bifurcation angle, and connectivity-was extracted and sorted into diameter-defined Strahler orders. Validation of Murray's law, describing optimal scaling exponents of radii for branching vessels, was performed to determine how closely PAs conform to this classical relationship. Using regression analyses of vessel diameters and lengths against orders and patient metrics (BSA, age, height), we found that diameters increased exponentially with order and allometrically with patient metrics. Length increased allometrically with patient metrics, albeit weakly. The average tortuosity index of all vessels was 0.026 ± 0.024, average bifurcation angle was 28.2 ± 15.1°, and average Murray's law exponent was 2.92 ± 1.07. We report a set of scaling laws for vessel diameter and length, along with other morphometric information. These provide an initial understanding of healthy structural preacinar PA development with age, which can be used for computational modeling studies and comparison with diseased PA anatomy.NEW & NOTEWORTHY Pulmonary artery (PA) morphometry studies to date have focused primarily on large arteries and intra-acinar arteries in either adults or children, neglecting preacinar arteries in both populations. Our study is the first to quantify in vivo preacinar PA morphometry changes spanning infants to adults. For preacinar arteries > 1 mm in diameter, we identify scaling laws for vessel diameters and lengths with patient metrics of growth and establish a healthy PA morphometry baseline for most preacinar PAs.

Pulmonary artery and lung parenchymal growth following early versus delayed stent interventions in a swine pulmonary artery stenosis model.

OBJECTIVES: Compare lung parenchymal and pulmonary artery (PA) growth and hemodynamics following early and delayed PA stent interventions for treatment of unilateral branch PA stenosis (PAS) in swine. BACKGROUND: How the pulmonary circulation remodels in response to different durations of hypoperfusion and how much growth and function can be recovered with catheter directed interventions at differing time periods of lung development is not understood. METHODS: A total of 18 swine were assigned to four groups: Sham (n = 4), untreated left PAS (LPAS) (n = 4), early intervention (EI) (n = 5), and delayed intervention (DI) (n = 5). EI had left pulmonary artery (LPA) stenting at 5 weeks (6 kg) with redilation at 10 weeks. DI had stenting at 10 weeks. All underwent right heart catheterization, computed tomography, magnetic resonance imaging, and histology at 20 weeks (55 kg). RESULTS: EI decreased the extent of histologic changes in the left lung as DI had marked alveolar septal and bronchovascular abnormalities (p = .05 and p < .05 vs. sham) that were less prevalent in EI. EI also increased left lung volumes and alveolar counts compared to DI. EI and DI equally restored LPA pulsatility, R heart pressures, and distal LPA growth. EI and DI improved, but did not normalize LPA stenosis diameter (LPA/DAo ratio: Sham 1.27 ± 0.11 mm/mm, DI 0.88 ± 0.10 mm/mm, EI 1.01 ± 0.09 mm/mm) and pulmonary blood flow distributions (LPA-flow%: Sham 52 ± 5%, LPAS 7 ± 2%, DI 44 ± 3%, EI 40 ± 2%). CONCLUSION: In this surgically created PAS model, EI was associated with improved lung parenchymal development compared to DI. Longer durations of L lung hypoperfusion did not detrimentally affect PA growth and R heart hemodynamics. Functional and anatomical discrepancies persist despite successful stent interventions that warrant additional investigation.

Short to medium term outcomes of right ventricular outflow tract stenting as initial palliation for symptomatic infants with complete atrioventricular septal defect with associated tetralogy of Fallot.

OBJECTIVES: To assess the impact of right ventricular outflow tract (RVOT) stenting as the primary palliation in infants with complete atrioventricular septal defect with associated tetralogy of Fallot (cAVSD/TOF). BACKGROUND: Historically, palliation of symptomatic patients with cAVSD/TOF has been achieved through surgical systemic to pulmonary artery shunting. More recently RVOT stenting has evolved as an acceptable alternative in patients with tetralogy of Fallot. METHODS: Retrospective review of all patients with cAVSD/TOF who underwent RVOT stenting as palliation over a 13-year period from two large tertiary referral centers. RESULTS: Twenty-six patients underwent RVOT stenting at a median age of 57 days (interquartile range [IQR] 25.5-106.5). Median weight for stent deployment was 3.7 kg (IQR 2.91-5.5 kg). RVOT stenting improved oxygen saturations from a median of 72% (IQR 70-76%) to 90% (IQR 84-92%), p < .001. There was a significant increase in the median Z-score for both branch pulmonary arteries at median follow-up of 255 days (IQR 60-455). Eight patients required RVOT stent balloon dilatations and 8 patients required re-stenting for progressive desaturation. The median duration between reinterventions was 122 days (IQR 53-294 days). Four patients died during the follow-up period. No deaths resulted from the initial intervention. To date, definitive surgical intervention was achieved in 19 patients (biventricular repair n = 15) at a median age of 369 days (IQR 223-546 days). CONCLUSION: RVOT stenting in cAVSD/TOF is a safe and effective palliative procedure in symptomatic infants, promoting pulmonary artery growth and improving oxygen saturations.

Evaluation of the Growth of Central Pulmonary Arteries Following Patent Ductus Arteriosus Stenting in Patients with Duct Dependent Pulmonary Circulation.

Pulmonary arteries' (PAs) growth can be promoted by stenting of patent ductus arteriosus (PDA). This may result in better angle between the PDA and the PAs, allowing improved growth. In this study, we sought to evaluate the effect of PDA stenting on the growth of the pulmonary arteries by comparing their dimensions pre-stenting to their dimensions in the pre-second stage operations in patients with congenital heart diseases-duct-dependent pulmonary (CHD-DDP) circulation. Between January 2015 and December 2016, 58 neonates with CHD-DDP circulation underwent transcatheter PDA stenting and had evaluation of PAs growth before the second stage. Various parameters [Pre-branching right and left pulmonary artery (RPA, LPA) diameters, their Z scores, LPA/RPA ratio, McGoon's ratio and Nakata index] were recorded and compared pre-stenting and pre-second stage. The evaluation was done using catheterization or multislice computed tomography (MSCT). PDA stenting was successful in 49 patients out of 58 (84.5%) patients with an age of 13.5 ± 10.4 days and a weight of 2.9 ± 0.5 kg. Twenty-two (44.9%) patients had complex CHD-DDP, 14 (28.6%) patients had PA/IVS and 13 (26.5%) patients had PA/VSD. Pre-second stage RPA, LPA diameters and their Z scores increased significantly (RPA increased from 0.36 ± 0.05 cm to 0.60 ± 0.11 cm, P < 0.001, RPA Z-score increased from - 1.29 ± 0.91 to 0.81 ± 0.18, P < 0.001; LPA increased from 0.34 ± 0.06 cm to 0.58 ± 0.10 cm, P < 0.001, LPA Z-score increased from - 1.17 ± 0.86 to 0.97 ± 0.48, P < 0.001). McGoon's ratio increased significantly from 1.20 ± 0.11 to 1.61 ± 0.15 (P < 0.001). Nakata index increased from 105.94 ± 33.53 to 183.48 ± 40.58 mm2/m2 (P < 0.001). However, LPA/RPA ratio did not change (0.96 ± 0.05 and 0.98 ± 0.16, P = 0.288). PDA stenting is effective in promoting the global and the individual pulmonary artery growth in congenital heart diseases with duct-dependent pulmonary circulation. In this study, we presented our experience with this approach in 2 tertiary care centers in the DELTA region of Egypt. PDA stenting, generally, showed symmetric growth of the pulmonary arteries with comparable results to the international figures.

Pulmonary hemodynamic and right ventricular responses to brief and prolonged exercise in middle-aged endurance athletes.

Right ventricular (RV) function is closely coupled to pulmonary arterial (PA) hemodynamics and is believed to decline with prolonged exercise. A linear pressure-flow relationship is thought to exist between PA pressures and increasing exercise intensity in athletes, yet a paucity of directly measured pulmonary hemodynamic data exists supporting this contention. We sought to describe the PA pressure, PA wedge pressure (PAWP), and RV functional responses to brief and prolonged exercise in endurance-trained athletes. Twenty-one healthy athletes (54 ± 5 yr) underwent right heart catheterization to assess pulmonary hemodynamics during graded, submaximal exercise. Measurements were made at rest and during three stages of steady-state, semiupright cycle ergometry at heart rates of 100 beats/min (EX1), 130 beats/min (EX2), and 150 beats/min (EX3). Five athletes completed an additional 34 min at 130 beats/min for a total exercise time of 60 min [prolonged exercise (PLG)]. PA pressures and PAWP increased significantly at EX1 without a further rise at EX2, EX3, or PLG. PAWP adjusted for absolute work rate demonstrated a significant decline as exercise intensity increased from EX1 to EX2. The resistance compliance time constant decreased at EX1 without further changes at EX2, EX3, and prolonged exercise. RV function did not decline during PLG. After an initial rise in PA pressure and PAWP during early, nonsteady-state exercise, values remained constant despite increases in exercise intensity and duration. These data indicate that in healthy, middle-aged endurance-trained athletes, the PA and pulmonary venous/left atrial compartments rapidly accommodate high conduit flows produced during intensive and prolonged exercise while maintaining RV function. NEW & NOTEWORTHY The right ventricular (RV)-pulmonary arterial (PA) circulatory unit has not been well studied during prolonged exercise, and this study provides an ecological approach that reflects a typical bout of endurance training integrating a transition from rest to exercise with successive increases in intensity, progressing to steady-state, sustained exercise. We demonstrated a remarkably constant response of the PA and PA wedge pressure during incremental, steady-state exercise and that no changes occur in pulmonary pressures throughout prolonged exercise, concomitant to a preservation of RV performance.

Utility of the Medtronic microvascular plug™ as a transcatheter implantable and explantable pulmonary artery flow restrictor in a swine model.

BACKGROUND: A surgical pulmonary artery band (PAB) is used to control excessive pulmonary blood flow for certain congenital heart diseases. Previous attempts have been made to develop a transcatheter, implantable pulmonary flow restrictor (PFR) without great success. We modified a microvascular plug (MVP) to be used as a PFR. The objectives of this study were to demonstrate feasibility of transcatheter implantation and retrieval of the modified MVP as a PFR, and compare PA growth while using the PFR versus PAB. METHODS AND RESULTS: The PFR was implanted in eight newborn piglets in bilateral branch pulmonary arteries (PAs). Immediately post-PFR implantation, the right ventricular systolic pressure increased from a median of 20-51 mmHg. Transcatheter retrieval of PFR was 100% successful at 3, 6, and 9 weeks and 50% at 12-weeks post-implant. A left PAB was placed via thoracotomy in four other newborn piglets. Debanding was performed 6-weeks later via balloon angioplasty. On follow-up, the proximal left PA diameters in the PFR and the PAB groups were similar (median 8 vs. 7.1 mm; p = 0.11); albeit the surgical band sites required repeat balloon angioplasty secondary to recurrent stenosis. By histopathology, there was grade II vessel injury in two pigs immediately post-retrieval of PFR that healed by 12 weeks. CONCLUSIONS: Transcatheter implantation and retrieval of the MVP as a PFR is feasible. PA growth is comparable to surgical PAB, which is likely to require reinterventions. The use of the MVP as a PFR in humans has to be trialed before recommending its routine use.

Postnatal delayed growth impacts cognition but rescues programmed impaired pulmonary vascular development in an IUGR rat model.

BACKGROUND AND AIMS: Intrauterine growth restriction (IUGR) is a state of slower fetal growth usually followed by a catch-up growth. Postnatal catch-up growth in IUGR models increases the incidence of pulmonary arterial hypertension in adulthood. Here, we hypothesize that the adverse pulmonary vascular consequences of IUGR may be improved by slowing down postnatal growth velocity. Meanwhile, cognitive function was also studied. METHODS AND RESULTS: We established an IUGR rat model by restricting maternal food throughout gestation. After birth, pups were fed a regular or restricted diet during lactation by changing litter size. Thus, there were three experimental groups according to the dam/offspring diet: C/C (gold standard), IUGR with catch-up growth (R/C) and IUGR with delayed growth (R/D). In adulthood (14 weeks of age), we assessed pulmonary vascular development by hemodynamic measurement and immunohistochemistry. Our results showed that adult R/C offspring developed an elevated mean pulmonary arterial pressure (mPAP) and pulmonary arteriolar remodeling accompanied with decreased eNOS mRNA and protein expressions compared to C/C or R/D offspring. This suggested that delayed postnatal growth improved pulmonary circulation compared to postnatal catch-up growth. Conversely, adult R/D offspring performed poorly in cognition. Behavior test and electrophysiology results exhibited a reduced synaptic plasticity. Furthermore, decreased mRNA expression levels of the memory-related gene zif268 and transcription factor recruitment factor p300 in the hippocampus region were also observed in R/D group. CONCLUSION: These findings indicate that delayed postnatal growth results in cognitive impairment, but it reverses elevations in mPAP induced by postnatal catch-up growth following IUGR.

The efficiency of systemic-to-pulmonary shunts in older children with hypoplastic pulmonary arteries.

BACKGROUND: To investigate the effects of systemic-to-pulmonary shunts (SPSs) in older children with hypoplastic pulmonary arteries and the factors affecting the development of the pulmonary arteries. METHODS: Eighty-six children (older than 3 years) who received SPSs were retrospectively analyzed. The perioperative parameters, the postoperative diameter of the pulmonary artery were collected, and the factors influencing the growth of the pulmonary arteries after an initial palliative shunt operation were analyzed. RESULTS: Two patients died postoperatively (2.33%), and the pulse oxygen saturation (SpO2 ) increased from 71.70 ± 6.75% preoperatively to 85.20 ± 11.07% at discharge. During the follow-up period of 56 (10-99) months, 37 patients (43.02%) underwent subsequent procedures, and in the remaining patients, the McGoon ratio was increased from 0.96 ± 0.48 at the surgery to 1.30 ± 0.31 at the final assessment (P < 0.05). Univariate analysis indicated that age younger than 5 years old (P < 0.05), pulmonary artery forward flow (P < 0.05) and a diagnosis of tetralogy of Fallot (P < 0.05) played positive roles in the growth of the pulmonary artery after surgery, while children with a McGoon ratio less than 0.6 showed poor development of the pulmonary arteries (P < 0.05). Multivariate analysis showed that age younger than 5 years old (P < 0.05) and pulmonary artery forward flow (P < 0.05) were positive effectors on the growth of the pulmonary artery. CONCLUSIONS: Older children with cyanotic congenital heart disease benefited from a systemic-pulmonary shunt and showed increased postoperative oxygen saturation and development of the pulmonary arteries. Age younger than 5 years and pulmonary artery antegrade flow were the positive factors influencing the growth of the pulmonary arteries postoperatively.

Consequences of an early catheter-based intervention on pulmonary artery growth and right ventricular myocardial function in a pig model of pulmonary artery stenosis.

OBJECTIVE: To determine the consequences of an early catheter-based intervention on pulmonary artery (PA) growth and right ventricular (RV) myocardial function in an animal model of branch PA stenosis. BACKGROUND: Acute results and safety profiles of deliberate stent fracture within the pulmonary vasculature have been demonstrated. The long-term impact of early stent intervention and deliberate stent fracture on PA growth and myocardial function is not understood. METHODS: Implantation of small diameter stents was performed in a pig model of left PA stenosis at 6 weeks (10 kg) followed by dilations at 10 (35 kg) and 18 weeks (65 kg) with intent to fracture and implant large diameter stents. Hemodynamics, RV contractility, and 2D/3D angiography were performed with each intervention. The heart and pulmonary vasculature were histologically assessed. RESULTS: Stent fracture occurred in 9/12 and implantation of large diameter stents was successful in 10/12 animals with no PA aneurysms or dissections. The final stented PA segment and distal left PA branch origins equaled the corresponding PA diameters of sham controls. Growth of left PA immediately beyond the stent was limited and there was diffuse fibro-intimal proliferation within the distal left and right PA. RV contractility was diminished in the intervention group and the response to dobutamine occurred uniquely via increases in heart rate. CONCLUSIONS: Early stent intervention in this surgically created PA stenosis model was associated with improved growth of the distal PA vasculature but additional investigation of PA vessel physiology and impact on the developing heart are needed.

Disruption of miR-29 Leads to Aberrant Differentiation of Smooth Muscle Cells Selectively Associated with Distal Lung Vasculature.

Differentiation of lung vascular smooth muscle cells (vSMCs) is tightly regulated during development or in response to challenges in a vessel specific manner. Aberrant vSMCs specifically associated with distal pulmonary arteries have been implicated in the pathogenesis of respiratory diseases, such as pulmonary arterial hypertension (PAH), a progressive and fatal disease, with no effective treatment. Therefore, it is highly relevant to understand the underlying mechanisms of lung vSMC differentiation. miRNAs are known to play critical roles in vSMC maturation and function of systemic vessels; however, little is known regarding the role of miRNAs in lung vSMCs. Here, we report that miR-29 family members are the most abundant miRNAs in adult mouse lungs. Moreover, high levels of miR-29 expression are selectively associated with vSMCs of distal vessels in both mouse and human lungs. Furthermore, we have shown that disruption of miR-29 in vivo leads to immature/synthetic vSMC phenotype specifically associated with distal lung vasculature, at least partially due to the derepression of KLF4, components of the PDGF pathway and ECM-related genes associated with synthetic phenotype. Moreover, we found that expression of FBXO32 in vSMCs is significantly upregulated in the distal vasculature of miR-29 null lungs. This indicates a potential important role of miR-29 in smooth muscle cell function by regulating FBXO32 and SMC protein degradation. These results are strongly supported by findings of a cell autonomous role of endogenous miR-29 in promoting SMC differentiation in vitro. Together, our findings suggested a vessel specific role of miR-29 in vSMC differentiation and function by targeting several key negative regulators.

Reintervention Burden and Vessel Growth After Surgical Reimplantation of a Pulmonary Artery During Childhood.

Children requiring reimplantation of a branch pulmonary artery (PA) are at risk for postoperative stenosis and impaired growth of the reimplanted PA. Outcomes and risk factors for reintervention and impaired growth are incompletely described. We reviewed data on patients who underwent reimplantation of a branch PA between 1/1/99 and 5/1/15 at a single center. The primary outcome was reintervention to treat postoperative stenosis. The secondary outcome was "catch-up" growth (faster diameter growth of the affected PA compared with the unaffected PA from the preoperative to follow-up measurements.). Twenty-six patients were identified with a total follow-up of 102.2 patient-years (median 2.5 years). Diagnoses included LPA sling (n = 12) and isolated PA of ductal origin with (n = 7) or without (n = 7) tetralogy of Fallot (ToF). All had primary repair of the anomalous PA. Seventeen (65%) had reintervention with median time to first reintervention of 69 (range 1-1005) days and median of 1.5 (range 1-6) reinterventions. 94% of reinterventions were transcatheter (53% balloon and 41% stent angioplasty). Patients with reintervention were younger (hazard ratio 0.75 per log-day, p = 0.02) and lower weight (hazard ratio 0.18 per log-kg, p = 0.02) at initial repair. Of the 18 with PA growth data, 8 (44%) had catch-up growth. There were no identified differences between those who did and did not demonstrate catch-up growth. Despite a practice of primary reimplantation and aggressive postoperative reintervention, these results suggest that changes in strategy are needed or that there are intrinsic patient factors that have more influence on longer-term reimplanted PA growth.

A method for evaluating the murine pulmonary vasculature using micro-computed tomography.

BACKGROUND: Significant mortality and morbidity are associated with alterations in the pulmonary vasculature. While techniques have been described for quantitative morphometry of whole-lung arterial trees in larger animals, no methods have been described in mice. We report a method for the quantitative assessment of murine pulmonary arterial vasculature using high-resolution computed tomography scanning. METHODS: Mice were harvested at 2 weeks, 4 weeks, and 3 months of age. The pulmonary artery vascular tree was pressure perfused to maximal dilation with a radio-opaque casting material with viscosity and pressure set to prevent capillary transit and venous filling. The lungs were fixed and scanned on a specimen computed tomography scanner at 8-µm resolution, and the vessels were segmented. Vessels were grouped into categories based on lumen diameter and branch generation. RESULTS: Robust high-resolution segmentation was achieved, permitting detailed quantitation of pulmonary vascular morphometrics. As expected, postnatal lung development was associated with progressive increase in small-vessel number and arterial branching complexity. CONCLUSIONS: These methods for quantitative analysis of the pulmonary vasculature in postnatal and adult mice provide a useful tool for the evaluation of mouse models of disease that affect the pulmonary vasculature.

Cysteine-rich 61 (Cyr61) upregulated in pulmonary arterial hypertension promotes the proliferation of pulmonary artery smooth muscle cells.

Background: We aimed to evaluate the expression of cysteine rich 61 (Cyr61) in patients with pulmonary arterial hypertension (PAH) as well as monocrotaline (MCT) induced PAH rat, and further investigate the effects and potential mechanisms of Cyr61 on the proliferation of pulmonary arterial smooth muscle cells (PASMCs). Methods and Results: Plasma samples were collected from 20 patients with idiopathic PAH, 20 connective tissue disease (CTD) associated PAH, 29 age-, gender- and disease matched CTD without PAH patients, and 28 healthy controls. ELISA was used to detect the level of Cyr61 in plasma. MCT-induced PAH (MCT-PAH) rat model was established by a single subcutaneous injection of MCT (60mg·kg-1). Lung tissues and pulmonary arteries of rats were collected, while the PASMCs were dissected and cultivated for in vitro experiments. Expression of Cyr61 in the lung tissues, pulmonary arteries and PASMCs were tested by immunohistochemical staining, western blot and quantitative real-time polymerase chain reaction. PASMCs from PAH rats were stimulated by exogenous recombinant Cyr61 protein and knocked down by small interfering RNA. Cell Counting Kit-8 assay was used to identify cell proliferation and the expression of p-AKT and AKT were analysed by western blot. The results showed plasma level of Cyr61 in PAH patients, especially CTD-PAH patients, were significant higher than that of CTD without PAH patients and healthy controls. Compared with wild rats, Cyr61 was overexpressed in the lung tissue, pulmonary arterial and PASMCs in PAH rats. Exogenous recombinant Cyr61 protein promoted the proliferation of PASMCs in a dose-dependent manner. While the expression of Cyr61 in PASMCs was inhibited by specific siRNA, cell proliferation was restrained and the expression of p-AKT declined. Conclusion: Plasma Cyr61 concentration in PAH patients was highly increased. Cyr61 could promote PASMCs proliferation via AKT pathway, indicating that Cyr61 may play a role in the pathogenesis of PAH.

Fate of Duct-Dependent, Discontinuous Pulmonary Arteries After Arterial Duct Stenting.

Significant and balanced PA growth following arterial duct (AD) stenting has already been consistently reported in literature. However, to date, no data are available about the role of this approach as palliation of congenital heart disease with a duct-dependent discontinuous pulmonary artery (dPA). The aim of this study was to evaluate the fate of a dPA of ductal origin following trans-catheter AD stabilization. Angiographic PA evaluation was performed in seven patients submitted to neonatal AD stenting as palliative recruitment of dPA. Five patients showed discontinuity of one PA, while two patients had both PAs served by bilateral ducts. PA growth was evaluated as per the Nakata index, McGoon ratio as well as dPA (n = 9) versus heart-dependent PA (hPA; n = 5) size and z-score changes. AD stabilization was performed using coronary stents dilated to 3.2 ± 0.3 mm (median 3.4), with significant increase of O2 saturation (from 83 ± 11 to 95 ± 5%, p < 0.02). Control angiography was performed 5.1 ± 2.8 months (median 6 months) after duct stenting, showing significant growth of the dPA (from 3.7 ± 1.0 to 7.6 ± 2.7 mm, p < 0.001; z-score from -0.7 ± 1.4 to 1.7 ± 2.2, p < 0.01). A trend toward better growth of the dPA as compared with the hPA was found (117 ± 87 vs. 54 ± 34%, p = NS). The final vessel size was still significantly different between the groups (dPA 7.6 ± 2.7 vs. hPA 11.9 ± 3.4 mm, p = 0.02), although the final z-score value did not significantly differ (dPA 1.7 ± 2.2 vs. hPA 3.8 ± 0.9 mm, p = NS). In conclusion, percutaneous AD stenting is effective in promoting a significant catch-up growth of duct-dependent dPA, being, therefore, advisable as a reliable alternative to surgical palliation.

Developmental acceleration of bradykinin-dependent relaxation by prenatal chronic hypoxia impedes normal development after birth.

Bradykinin-induced activation of the pulmonary endothelium triggers nitric oxide production and other signals that cause vasorelaxation, including stimulation of large-conductance Ca(2+)-activated K(+) (BKCa) channels in myocytes that hyperpolarize the plasma membrane and decrease intracellular Ca(2+). Intrauterine chronic hypoxia (CH) may reduce vasorelaxation in the fetal-to-newborn transition and contribute to pulmonary hypertension of the newborn. Thus we examined the effects of maturation and CH on the role of BKCa channels during bradykinin-induced vasorelaxation by examining endothelial Ca(2+) signals, wire myography, and Western immunoblots on pulmonary arteries isolated from near-term fetal (∼ 140 days gestation) and newborn, 10- to 20-day-old, sheep that lived in normoxia at 700 m or in CH at high altitude (3,801 m) for >100 days. CH enhanced bradykinin-induced relaxation of fetal vessels but decreased relaxation in newborns. Endothelial Ca(2+) responses decreased with maturation but increased with CH. Bradykinin-dependent relaxation was sensitive to 100 µM nitro-L-arginine methyl ester or 10 µM 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, supporting roles for endothelial nitric oxide synthase and soluble guanylate cyclase activation. Indomethacin blocked relaxation in CH vessels, suggesting upregulation of PLA2 pathways. BKCa channel inhibition with 1 mM tetraethylammonium reduced bradykinin-induced vasorelaxation in the normoxic newborn and fetal CH vessels. Maturation reduced whole cell BKCa channel α1-subunit expression but increased ß1-subunit expression. These results suggest that CH amplifies the contribution of BKCa channels to bradykinin-induced vasorelaxation in fetal sheep but stunts further development of this vasodilatory pathway in newborns. This involves complex changes in multiple components of the bradykinin-signaling axes.