Pathogenesis and Physiologic Mechanisms of Neonatal Pulmonary Hypertension: Preclinical Studies

Neonatal pulmonary hypertension (PH) is a devastating disorder of the pulmonary vasculature characterized by elevated pulmonary vascular resistance and mean pulmonary arterial pressure. Occurring predominantly because of maldevelopment or maladaptation of the pulmonary vasculature, PH in neonates is associated with suboptimal short-term and long-term outcomes because its pathobiology is unclear in most circumstances, and it responds poorly to conventional pulmonary vasodilators. Understanding the pathogenesis and pathophysiology of neonatal PH can lead to novel strategies and precise therapies. The review is designed to achieve this goal by summarizing pulmonary vascular development and the pathogenesis and pathophysiology of PH associated with maladaptation, bronchopulmonary dysplasia, and congenital diaphragmatic hernia based on evidence predominantly from preclinical studies. We also discuss the pros and cons of and provide future directions for preclinical studies in neonatal PH.

c-Myc Drives inflammation of the maternal-fetal interface, and neonatal lung remodeling induced by intra-amniotic inflammation

Background: Intra-amniotic inflammation (IAI) is associated with increased risk of preterm birth and bronchopulmonary dysplasia (BPD), but the mechanisms by which IAI leads to preterm birth and BPD are poorly understood, and there are no effective therapies for preterm birth and BPD. The transcription factor c-Myc regulates various biological processes like cell growth, apoptosis, and inflammation. We hypothesized that c-Myc modulates inflammation at the maternal-fetal interface, and neonatal lung remodeling. The objectives of our study were 1) to determine the kinetics of c-Myc in the placenta, fetal membranes and neonatal lungs exposed to IAI, and 2) to determine the role of c-Myc in modulating inflammation at the maternal-fetal interface, and neonatal lung remodeling induced by IAI. Methods: Pregnant Sprague-Dawley rats were randomized into three groups: 1) Intra-amniotic saline injections only (control), 2) Intra-amniotic lipopolysaccharide (LPS) injections only, and 3) Intra-amniotic LPS injections with c-Myc inhibitor 10058-F4. c-Myc expression, markers of inflammation, angiogenesis, immunohistochemistry, and transcriptomic analyses were performed on placenta and fetal membranes, and neonatal lungs to determine kinetics of c-Myc expression in response to IAI, and effects of prenatal systemic c-Myc inhibition on lung remodeling at postnatal day 14. Results: c-Myc was upregulated in the placenta, fetal membranes, and neonatal lungs exposed to IAI. IAI caused neutrophil infiltration and neutrophil extracellular trap (NET) formation in the placenta and fetal membranes, and neonatal lung remodeling with pulmonary hypertension consistent with a BPD phenotype. Prenatal inhibition of c-Myc with 10058-F4 in IAI decreased neutrophil infiltration and NET formation, and improved neonatal lung remodeling induced by LPS, with improved alveolarization, increased angiogenesis, and decreased pulmonary vascular remodeling. Discussion: In a rat model of IAI, c-Myc regulates neutrophil recruitment and NET formation in the placenta and fetal membranes. c-Myc also participates in neonatal lung remodeling induced by IAI. Further studies are needed to investigate c-Myc as a potential therapeutic target for IAI and IAI-associated BPD.

Chorioamnionitis accelerates granule cell and oligodendrocyte maturation in the cerebellum of preterm nonhuman primates

BACKGROUND

Preterm birth is often associated with chorioamnionitis and leads to increased risk of neurodevelopmental disorders, such as autism. Preterm birth can lead to cerebellar underdevelopment, but the mechanisms of disrupted cerebellar development in preterm infants are not well understood. The cerebellum is consistently affected in people with autism spectrum disorders, showing reduction of Purkinje cells, decreased cerebellar grey matter, and altered connectivity.

METHODS

Preterm rhesus macaque fetuses were exposed to intra-amniotic LPS (1 mg, E. coli O55:B5) at 127 days (80%) gestation and delivered by c-section 5 days after injections. Maternal and fetal plasma were sampled for cytokine measurements. Chorio-decidua was analyzed for immune cell populations by flow cytometry. Fetal cerebellum was sampled for histology and molecular analysis by single-nuclei RNA-sequencing (snRNA-seq) on a 10× chromium platform. snRNA-seq data were analyzed for differences in cell populations, cell-type specific gene expression, and inferred cellular communications.

RESULTS

We leveraged snRNA-seq of the cerebellum in a clinically relevant rhesus macaque model of chorioamnionitis and preterm birth, to show that chorioamnionitis leads to Purkinje cell loss and disrupted maturation of granule cells and oligodendrocytes in the fetal cerebellum at late gestation. Purkinje cell loss is accompanied by decreased sonic hedgehog signaling from Purkinje cells to granule cells, which show an accelerated maturation, and to oligodendrocytes, which show accelerated maturation from pre-oligodendrocytes into myelinating oligodendrocytes.

CONCLUSION

These findings suggest a role of chorioamnionitis on disrupted cerebellar maturation associated with preterm birth and on the pathogenesis of neurodevelopmental disorders among preterm infants.

Protective role of CXCR7 activation in neonatal hyperoxia-induced systemic vascular remodeling and cardiovascular dysfunction in juvenile rats

Neonatal hyperoxia induces long-term systemic vascular stiffness and cardiovascular remodeling, but the mechanisms are unclear. Chemokine receptor 7 (CXCR7) represents a key regulator of vascular homeostasis and repair by modulating TGF-β1 signaling. This study investigated whether pharmacological CXCR7 agonism prevents neonatal hyperoxia-induced systemic vascular stiffness and cardiac dysfunction in juvenile rats. Newborn Sprague Dawley rat pups assigned to room air or hyperoxia (85% oxygen), received CXCR7 agonist, TC14012 or placebo for 3 weeks. These rat pups were maintained in room air until 6 weeks when aortic pulse wave velocity doppler, cardiac echocardiography, aortic and left ventricular (LV) fibrosis were assessed. Neonatal hyperoxia induced systemic vascular stiffness and cardiac dysfunction in 6-week-old rats. This was associated with decreased aortic and LV CXCR7 expression. Early treatment with TC14012, partially protected against neonatal hyperoxia-induced systemic vascular stiffness and improved LV dysfunction and fibrosis in juvenile rats by decreasing TGF-β1 expression. In vitro, hyperoxia-exposed human umbilical arterial endothelial cells and coronary artery endothelial cells had increased TGF-β1 levels. However, treatment with TC14012 significantly reduced the TGF-β1 levels. These results suggest that dysregulation of endothelial CXCR7 signaling may contribute to neonatal hyperoxia-induced systemic vascular stiffness and cardiac dysfunction.

Extracellular vesicles: pathogenic messengers and potential therapy for neonatal lung diseases

Extracellular vesicles (EVs) are a heterogeneous group of nano-sized membranous structures increasingly recognized as mediators of intercellular and inter-organ communication. EVs contain a cargo of proteins, lipids and nucleic acids, and their cargo composition is highly dependent on the biological function of the parental cells. Their cargo is protected from the extracellular environment by the phospholipid membrane, thus allowing for safe transport and delivery of their intact cargo to nearby or distant target cells, resulting in modification of the target cell's gene expression, signaling pathways and overall function. The highly selective, sophisticated network through which EVs facilitate cell signaling and modulate cellular processes make studying EVs a major focus of interest in understanding various biological functions and mechanisms of disease. Tracheal aspirate EV-miRNA profiling has been suggested as a potential biomarker for respiratory outcome in preterm infants and there is strong preclinical evidence showing that EVs released from stem cells protect the developing lung from the deleterious effects of hyperoxia and infection. This article will review the role of EVs as pathogenic messengers, biomarkers, and potential therapies for neonatal lung diseases.

Case report: Fatal lung hyperinflammation in a preterm newborn with SARS-CoV-2 infection

Vertical transmission of SARS-CoV-2 from mother to fetus is widely accepted. Whereas most infected neonates present with mild symptoms or are asymptomatic, respiratory distress syndrome (RDS) and abnormal lung images are significantly more frequent in COVID-19 positive neonates than in non-infected newborns. Fatality is rare and discordant meta-analyses of case reports and series relating perinatal maternal COVID-19 status to neonatal disease severity complicate their extrapolation as prognostic indicators. A larger database of detailed case reports from more extreme cases will be required to establish therapeutic guidelines and allow informed decision making. Here we report an unusual case of a 28 weeks' gestation infant with perinatally acquired SARS-CoV-2, who developed severe protracted respiratory failure. Despite intensive care from birth with first line anti-viral and anti-inflammatory therapy, respiratory failure persisted, and death ensued at 5 months. Lung histopathology showed severe diffuse bronchopneumonia, and heart and lung immunohistochemistry confirmed macrophage infiltration, platelet activation and neutrophil extracellular trap formation consistent with late multisystem inflammation. To our knowledge, this is the first report of SARS CoV-2 pulmonary hyperinflammation in a preterm newborn with fatal outcome.

OUP accepted manuscript

Bronchopulmonary dysplasia (BPD) is a life-threatening condition in preterm infants with few effective therapies. Mesenchymal stem or stromal cells (MSCs) are a promising therapeutic strategy for BPD. The ideal MSC source for BPD prevention is however unknown. The objective of this study was to compare the regenerative effects of MSC obtained from bone marrow (BM) and umbilical cord tissue (UCT) in an experimental BPD model. In vitro, UCT-MSC demonstrated greater proliferation and expression of anti-inflammatory cytokines as compared to BM-MSC. Lung epithelial cells incubated with UCT-MSC conditioned media (CM) had better-wound healing following scratch injury. UCT-MSC CM and BM-MSC CM had similar pro-angiogenic effects on hyperoxia-exposed pulmonary microvascular endothelial cells. In vivo, newborn rats exposed to normoxia or hyperoxia (85% O₂) from postnatal day (P) 1 to 21 were given intra-tracheal (IT) BM or UCT-MSC (1 × 10⁶ cells/50 μL), or placebo (PL) on P3. Hyperoxia PL-treated rats had marked alveolar simplification, reduced lung vascular density, pulmonary vascular remodeling, and lung inflammation. In contrast, administration of both BM-MSC and UCT-MSC significantly improved alveolar structure, lung angiogenesis, pulmonary vascular remodeling, and lung inflammation. UCT-MSC hyperoxia-exposed rats however had greater improvement in some morphometric measures of alveolarization and less lung macrophage infiltration as compared to the BM-MSC-treated group. Together, these findings suggest that BM-MSC and UCT-MSC have significant lung regenerative effects in experimental BPD but UCT-MSC suppresses lung macrophage infiltration and promotes lung epithelial cell healing to a greater degree.

Circulating extracellular vesicles activate the pyroptosis pathway in the brain following ventilation-induced lung injury

BACKGROUND

Mechanical ventilation of preterm newborns causes lung injury and is associated with poor neurodevelopmental outcomes. However, the mechanistic links between ventilation-induced lung injury (VILI) and brain injury is not well defined. Since circulating extracellular vesicles (EVs) are known to link distant organs by transferring their cargos, we hypothesized that EVs mediate inflammatory brain injury associated with VILI.

METHODS

Neonatal rats were mechanically ventilated with low (10 mL/kg) or high (25 mL/kg) tidal volume for 1 h on post-natal day 7 followed by recovery for 2 weeks. Exosomes were isolated from the plasma of these rats and adoptively transferred into normal newborn rats. We assessed the effect of mechanical ventilation or exosome transfer on brain inflammation and activation of the pyroptosis pathway by western blot and histology.

RESULTS

Injurious mechanical ventilation induced similar markers of inflammation and pyroptosis, such as increased IL-1β and activated caspase-1/gasdermin D (GSDMD) in both lung and brain, in addition to inducing microglial activation and cell death in the brain. Isolated EVs were enriched for the exosomal markers CD9 and CD81, suggesting enrichment for exosomes. EVs isolated from neonatal rats with VILI had increased caspase-1 but not GSDMD. Adoptive transfer of these EVs led to neuroinflammation with microglial activation and activation of caspase-1 and GSDMD in the brain similar to that observed in neonatal rats that were mechanically ventilated.

CONCLUSIONS

These findings suggest that circulating EVs can contribute to the brain injury and poor neurodevelopmental outcomes in preterm infants with VILI through activation of GSDMD.

Amniotic fluid-derived extracellular vesicles: characterization and therapeutic efficacy in an experimental model of bronchopulmonary dysplasia

BACKGROUND AIMS

Extracellular vesicles (EVs) are being tested for their use as novel therapeutics. However, the optimal source of EVs is currently under investigation. Amniotic fluid (AF) is a natural source of EVs that can be easily obtained for use in regenerative medicine, yet AF-EV characterization has not been fully explored.

METHODS

Here the authors demonstrate AF as a rich source of EVs and identify the microRNA and proteomic cargo. Bioinformatics analysis of this cargo revealed multiple pathway targets, including immunomodulatory, anti-inflammatory and free radical scavenging networks. The authors further demonstrated the therapeutic potential of this EV product as a novel preventative agent for bronchopulmonary dysplasia (BPD).

RESULTS

Intra-tracheal administration of AF-EVs preserved alveolar development, attenuated vascular remodeling and pulmonary hypertension, decreased lung pro-inflammatory cytokine expression and reduced macrophage infiltration in an experimental BPD model.

CONCLUSIONS

The authors' results suggest that AF is a viable biological fluid for EV harvest and that AF-EVs have strong therapeutic potential for pulmonary diseases, such as BPD, warranting further development to transition this novel EV product into the clinic.

Abstract P390: Gender And Strain Background Affect Cardiopulmonary Function In Col4a3 -/- Alport Mice

Background: Alport syndrome (AS) is a hereditary form of chronic kidney inflammation that results in renal failure (RF). Our group previously reported that Col4a3 -/- mice, a model of AS and RF, on 129J background exemplified multiple features of heart failure with preserved ejection fraction (HFpEF). This study investigates the effect of 3 different genetic backgrounds on cardiopulmonary function in Col4a3 -/- mice.

Methods: Male and female Col4a3 -/- (Alport) and WT mice on 3 different genetic backgrounds, 129x1/SvJ, C57Bl/6 and BALBC, were examined using echocardiography, whole body plethysmography (WBP) and pressure-volume (PV) loop analysis. Ttest was used for statistical analysis. Four groups per strain were used (n= 4 to 15 per group).

Results: Compared with their respective age-matched WT controls, both male and female 8-week-old Col4a3 -/- 129x1/SvJ mice demonstrated impaired systolic function (EF of 56% to 43.7%, p=0.0018 for females and 50.9% to 42% for males, p=0.044; SV, CO, p<0.05) and diastolic dysfunction (increased IVRT from 15.32ms to 21.72ms, p=0.0009 for females; 16.57ms to 26.21ms, p<0.0001 for males; increased MPI, P<0.05). Additionally, PV loop analysis showed an increased EDPVR and end diastolic pressure, prolonged time constant of LV relaxation, and decreased CO and SV (p<0.05). However for Col4a3 -/- BalbC (8-week-old) and Col4a3 -/- C57Bl/6 (20-week-old) strains, only females exhibited systolic (BalbC: EF% 51% to 45.66%, p=0.106 for females and 43.5% to 40.8% for males, p=0.508; B6: EF% 51.30% to 40.80% p=0.024 for females and 48.43% to 40.91%, p=0.3098 for males; SV, CO, p<0.05) and diastolic dysfunction (IVRT from 15.96ms to 24.91ms for Balb/C and 18.20ms to 25.63ms for B6, p<0.05). Male Col4a3 -/- BalbC had an increase in minimum pressure and end-systolic pressure, and an increased pressure at dV/dt-max. Male Col4a3 -/- C57Bl/6 mice had an increased ESPVR slope (p<0.05). All strains except BalbC males demonstrated alterations (p<0.05) in pulmonary function including decreased ventilation rate (MV, mL/min) and respiratory frequency (BPM), decreased peak expiratory flow, EF50, increased expiratory time, relaxation time, inspiratory time, and time of pause at end-of-expiration.

Conclusion: Both male and female Col4a3 -/- 129x1/SvJ mice demonstrated impaired cardiopulmonary viability. However, Col4a3 -/- mice on BalbC or C57Bl/6 strains had cardiopulmonary deficits only in females.

Abstract P420: Nano-Triciribine Reduces SARS2-CoV-2 Infection By Sequestering ACE2 And The Novel Host Factor LDLR

Background: People with previous CVD hospitalized for COVID-19 have elevated death rate. We reported that patients with diabetes and HF higher protein levels of the low density lipoprotein receptor (LDLR). We hypothesized that LDLR is a novel host factor for the SARS-CoV-2-Spike (S2S) protein that may be regulated by the Akt inhibitor Triciribine (TCN), a drug being tested in Phase III studies for breast cancer. We also hypothesized that nano-formulation of Triciribine (NanoTriciribine; NTCN) would enhance its efficacy and allow for intranasal delivery.

Methods: Interactions between the recombinant proteins Spike-RBD (receptor binding domain), ACE2, LDLR and its ectodomains (EGFA-EFFB, C2-C5 and C2) were analyzed by binding assays and co-IP in HepG2, HK2, and 293T cells. Viral entry assays were performed with 2 S2S pseudoviruses using 293T cells + hACE2 and TMPRSS2 or Furin protease. The effect of NTCN or the LXR agonist GW-3965 on viral uptake (pseudotyped VSVΔG-GFP*S2S or chimera VSV-S2S-eGFP virus) was assessed. Akt, pAkt, ACE2, and LDLR levels were determined in 293T+hACE2 by flow cytometry. Assays were done in triplicates and 1-way-ANOVA with Tukey’s correction was used for statistics.

Results: RBD protein binds modestly to the human LDLR (EC 50 :10μM) and its C2-C5 ectodomain (EC 50 :13.8μM). Co-IP revealed a novel and strong LDLR-ACE2 interaction in several human cell lines. LDLR overexpression in human cells increased the uptake of VSVΔG-GFP*S2S (FC=2.32;p<0.001) and chimera virus (FC=.33; p<.0001). NTCN and TCN each reduced pAkt/Akt ratio. 1μM TCN or NTCN reduced LDLR (7.2%;p<.01 & 15.6%;p<0.0001) and ACE2 (32%;p<0.05 & 44.7%;p<.01) cell surface expression, respectively. 1μM NTCN or GW-3965 reduced S2S viral entry by 64.2% (p<.0001) and 40.7% (p<.01), respectively, confirming a role for LDLR in S2S infection. In hACE2tg mice, chimera VSV-S2S caused significant lung infection as measured by qPCR, GFP expression in proximal and distal lung airway epithelial cells, and electron microscopy. Intranasal delivery of NTCN was well tolerated.

Conclusions: LDLR enhanced S2S viral entry supporting the elevated COVID-19 susceptibility seen in patients with heart disease. NTCN is a promising candidate for prophylactic treatment against COVID-19.

Neonatal hyperoxia exposure induces aortic biomechanical alterations and cardiac dysfunction in juvenile rats

Supplemental oxygen (O₂) therapy in preterm infants impairs lung development, but the impact of O₂ on long‐term systemic vascular structure and function has not been well‐explored. The present study tested the hypothesis that neonatal O₂ therapy induces long‐term structural and functional alterations in the systemic vasculature, resulting in vascular stiffness observed in children and young adults born preterm. Newborn Sprague‐Dawley rats were exposed to normoxia (21% O₂) or hyperoxia (85% O₂) for 1 and 3 weeks. A subgroup exposed to 3 weeks hyperoxia was recovered in normoxia for an additional 3 weeks. Aortic stiffness was assessed by pulse wave velocity (PWV) using Doppler ultrasound and pressure myography. Aorta remodeling was assessed by collagen deposition and expression. Left ventricular (LV) function was assessed by echocardiography. We found that neonatal hyperoxia exposure increased vascular stiffness at 3 weeks, which persisted after normoxic recovery at 6 weeks of age. These findings were accompanied by increased PWV, aortic remodeling, and altered LV function as evidenced by decreased ejection fraction, cardiac output, and stroke volume. Importantly, these functional changes were associated with increased collagen deposition in the aorta. Together, these findings demonstrate that neonatal hyperoxia induces early and sustained biomechanical alterations in the systemic vasculature and impairs LV function. Early identification of preterm infants who are at risk of developing systemic vascular dysfunction will be crucial in developing targeted prevention strategies that may improve the long‐term cardiovascular outcomes in this vulnerable population.

Soluble Klotho, a biomarker and therapeutic strategy to reduce bronchopulmonary dysplasia and pulmonary hypertension in preterm infants

Preterm infants with bronchopulmonary dysplasia (BPD) and pulmonary hypertension (PH) have accelerated lung aging and poor long-term outcomes. Klotho is an antiaging protein that modulates oxidative stress, angiogenesis and fibrosis. Here we test the hypothesis that decreased cord Klotho levels in preterm infants predict increased BPD-PH risk and early Klotho supplementation prevents BPD-like phenotype and PH in rodents exposed to neonatal hyperoxia. In experiment 1, Klotho levels were measured in cord blood of preterm infants who were enrolled in a longitudinal cohort study. In experiment 2, using an experimental BPD-PH model, rat pups exposed to room air or hyperoxia (85% O₂) were randomly assigned to receive every other day injections of recombinant Klotho or placebo. The effect of Klotho on lung structure, PH and cardiac function was assessed. As compared to controls, preterm infants with BPD or BPD-PH had decreased cord Klotho levels. Early Klotho supplementation in neonatal hyperoxia-exposed rodents preserved lung alveolar and vascular structure, attenuated PH, reduced pulmonary vascular remodeling and improved cardiac function. Together, these findings have important implications as they suggest that perinatal Klotho deficiency contributes to BPD-PH risk and strategies that preserve Klotho levels, may improve long-term cardiopulmonary outcomes in preterm infants.

Intra-tracheal administration of a naked plasmid expressing stromal derived factor-1 improves lung structure in rodents with experimental bronchopulmonary dysplasia

Background

Bronchopulmonary dysplasia (BPD) is characterized by alveolar simplification and disordered angiogenesis. Stromal derived factor-1 (SDF-1) is a chemokine which modulates cell migration, proliferation, and angiogenesis. Here we tested the hypothesis that intra-tracheal (IT) administration of a naked plasmid DNA expressing SDF-1 would attenuate neonatal hyperoxia-induced lung injury in an experimental model of BPD, by promoting angiogenesis.

Design/methods

Newborn Sprague-Dawley rat pups (n = 18–20/group) exposed to room air (RA) or hyperoxia (85% O2) from postnatal day (P) 1 to 14 were randomly assigned to receive IT a naked plasmid expressing SDF-1, JVS-100 (Juventas Therapeutics, Cleveland, Ohio) or placebo (PL) on P3. Lung alveolarization, angiogenesis, inflammation, vascular remodeling and pulmonary hypertension (PH) were assessed on P14. PH was determined by measuring right ventricular systolic pressure (RVSP) and the weight ratio of the right to left ventricle + septum (RV/LV + S). Capillary tube formation in SDF-1 treated hyperoxia-exposed human pulmonary microvascular endothelial cells (HPMEC) was determined by matrigel assay. Data is expressed as mean ± SD and analyzed by two-way ANOVA.

Results

Exposure of neonatal pups to 14 days of hyperoxia decreased lung SDF-1 gene expression. Moreover, whilst hyperoxia exposure inhibited capillary tube formation in HPMEC, SDF-1 treatment increased tube length and branching in HPMEC. PL-treated hyperoxia-exposed pups had decreased alveolarization and lung vascular density. This was accompanied by an increase in RVSP, RV/LV + S, pulmonary vascular remodeling and inflammation. In contrast, IT JVS-100 improved lung structure, reduced inflammation, PH and vascular remodeling.

Conclusions

Intratracheal administration of a naked plasmid expressing SDF-1 improves alveolar and vascular structure in an experimental model of BPD. These findings suggest that therapies which modulate lung SDF-1 expression may have beneficial effects in preterm infants with BPD.

Intra-Amniotic Soluble Endoglin Impairs Lung Development in Neonatal Rats

Soluble endoglin (sENG) is increased in the amniotic fluid of women with preeclampsia and chorioamnionitis. Preterm infants born to women with these disorders have an increased risk of aberrant lung development. Whether this increased risk is secondary to elevated sENG levels is unclear. The objective of this study was to determine whether intrauterine exposure to an adenovirus overexpressing sENG impairs neonatal lung angiogenesis by modulating lung endothelial nitric oxide synthase (eNOS) signaling. Pregnant Sprague-Dawley rats were randomly assigned to receive ultrasound-guided intra-amniotic injections of adenovirus overexpressing sENG (Ad-sENG) or control adenovirus (Ad-control) on embryonic day 17. After this exposure, rat pups were maintained in normoxia and evaluated on postnatal day 14. Intra-amniotic Ad-sENG decreased lung vascular endothelial growth factor receptor 2 and eNOS expression in rat pups. This was accompanied by a marked decrease in lung angiogenesis and alveolarization. Ad-sENG-exposed pups also had an increase in right ventricular systolic pressure, weight ratio of right ventricle to left ventricle plus septum, and pulmonary vascular remodeling. In addition, exposure of human pulmonary artery endothelial cells to recombinant sENG reduced endothelial tube formation and protein levels of eNOS, phosphorylated eNOS, and phosphorylated Smad1/5. Together, our findings demonstrate that intrauterine exposure to an adenovirus overexpressing sENG disrupts lung development by impairing Smad1/5-eNOS signaling. We speculate that sENG-mediated dysregulation of Smad1/5-eNOS signaling contributes to impaired lung development and potentially primes the developing lung for further postnatal insults. Further studies exploring the relationship between amniotic fluid sENG levels and preterm respiratory outcomes will be necessary.

Image processing can cause some malignant soft-tissue lesions to be missed in digital mammography images

AIM

To investigate the effect of image processing on cancer detection in mammography.

METHODS AND MATERIALS

An observer study was performed using 349 digital mammography images of women with normal breasts, calcification clusters, or soft-tissue lesions including 191 subtle cancers. Images underwent two types of processing: FlavourA (standard) and FlavourB (added enhancement). Six observers located features in the breast they suspected to be cancerous (4,188 observations). Data were analysed using jackknife alternative free-response receiver operating characteristic (JAFROC) analysis. Characteristics of the cancers detected with each image processing type were investigated.

RESULTS

For calcifications, the JAFROC figure of merit (FOM) was equal to 0.86 for both types of image processing. For soft-tissue lesions, the JAFROC FOM were better for FlavourA (0.81) than FlavourB (0.78); this difference was significant (p=0.001). Using FlavourA a greater number of cancers of all grades and sizes were detected than with FlavourB. FlavourA improved soft-tissue lesion detection in denser breasts (p=0.04 when volumetric density was over 7.5%) CONCLUSIONS: The detection of malignant soft-tissue lesions (which were primarily invasive) was significantly better with FlavourA than FlavourB image processing. This is despite FlavourB having a higher contrast appearance often preferred by radiologists. It is important that clinical choice of image processing is based on objective measures.

Inhibition of Rac1 Signaling Downregulates Inflammasome Activation and Attenuates Lung Injury in Neonatal Rats Exposed to Hyperoxia

BACKGROUND

Inflammatory injury, particularly the production of active interleukin (IL)-1β plays a major role in the pathogenesis of bronchopulmonary dysplasia (BPD) in preterm infants. The release of active IL-1β is controlled by posttranscriptional modifications of its proform (pro-IL-1β) through the inflammasome. Rac1 is a member of the Rho family of GTPases that regulate the inflammatory process.

OBJECTIVE

This study tested the hypothesis that Rac1 signaling increases inflammasome activation that results in damaging inflammation, and that the inhibition of Rac1 signaling prevents lung injury, by inhibiting inflammasome activation in a newborn rat model of BPD induced by hyperoxia.

METHODS

Newborn rat pups were exposed to room air or hyperoxia (85% O2) and received daily intraperitoneal injections of placebo (normal saline) or NSC23766, a specific Rac1 inhibitor, for 10 days. The effects on lung inflammation, alveolarization, vascular development, vascular remodeling, right ventricular systolic pressure, and right ventricular hypertrophy (RVH) were then assessed.

RESULTS

Hyperoxia exposure upregulated Rac1 and increased the production of active IL-1β, which was accompanied by increasing expression of the inflammasome. In addition, hyperoxia induced the pathological hallmarks of BPD. However, treatment with NSC23766 significantly decreased inflammasome activation and macrophage infiltration, improved alveolar and vascular development, and reduced pulmonary vascular remodeling and RVH.

CONCLUSION

These results indicate that Rac1 signaling regulates the expression of the inflammasome and plays a pivotal role in the pathogenesis of hyperoxia-induced neonatal lung injury. Therefore, targeting Rac1 signaling may provide a novel strategy to prevent and treat BPD in preterm infants.

Can the channelized Hotelling observer including aspects of the human visual system predict human observer performance in mammography?

PURPOSE

In mammography, images are processed prior to display. Model observers (MO) are candidates to objectively evaluate processed images if they can predict human observer performance for detail detection. The aim of this study was to investigate if the channelized Hotelling observer (CHO) can be configured to predict human observer performance in mammography like images.

METHODS

The performance correlation between human observers and CHO has been evaluated using different channel-sets and by including aspects of the human visual system (HVS). The correlation was investigated for the detection of disk-shaped details in simulated white noise (WN) and clustered lumpy backgrounds (CLB) images, representing respectively quantum noise limited and mammography like images. The images were scored by the MO and five human observers in 2-alternative forced choice experiments.

RESULTS

For WN images the most useful formulation of the CHO to predict human observer performance was obtained using three difference of Gaussian channels without adding HVS aspects (RLR2=0.62). For CLB images the most useful formulation was the partial least square channel-set without adding HVS aspects (RLR2=0.71). The correlation was affected by detail size and background.

CONCLUSIONS

This study has shown that the CHO can predict human observer performance. Due to object size and background dependency it is important that the range of object sizes and allowed variability in background are specified and validated carefully before the CHO can be implemented for objective image quality assessment.

Can the non-pre-whitening model observer, including aspects of the human visual system, predict human observer performance in mammography?

PURPOSE

In mammography, images are processed prior to display. Current methodologies based on physical image quality measurements are however not designed for the evaluation of processed images. Model observers (MO) might be suitable for this evaluation. The aim of this study was to investigate whether the non-pre-whitening (NPW) MO can be used to predict human observer performance in mammography-like images by including different aspects of the human visual system (HVS).

METHODS

The correlation between human and NPW MO performance has been investigated for the detection of disk shaped objects in simulated white noise (WN) and clustered lumpy backgrounds (CLB), representing quantum noise limited and mammography-like images respectively. The images were scored by the MO and five human observers in a 2-alternative forced choice experiment.

RESULTS

For WN images it was found that the log likelihood ratio (RLR2), which expresses the goodness of fit, was highest (0.44) for the NPW MO without addition of HVS aspects. For CLB the RLR2 improved from 0.46 to 0.65 with addition of HVS aspects. The correlation was affected by object size and background.

CONCLUSIONS

This study shows that by including aspects of the HVS, the performance of the NPW MO can be improved to better predict human observer performance. This demonstrates that the NPW MO has potential for image quality assessment. However, due to the dependencies found in the correlation, the NPW MO can only be used for image quality assessment for a limited range of object sizes and background variability.

The Effect of Gender on Mesenchymal Stem Cell (MSC) Efficacy in Neonatal Hyperoxia-Induced Lung Injury

Background

Mesenchymal stem cells (MSC) improve alveolar and vascular structures in experimental models of bronchopulmonary dysplasia (BPD). Female MSC secrete more anti-inflammatory and pro-angiogenic factors as compared to male MSC. Whether the therapeutic efficacy of MSC in attenuating lung injury in an experimental model of BPD is influenced by the sex of the donor MSC or recipient is unknown. Here we tested the hypothesis that female MSC would have greater lung regenerative properties than male MSC in experimental BPD and this benefit would be more evident in males.

Objective

To determine whether intra-tracheal (IT) administration of female MSC to neonatal rats with experimental BPD has more beneficial reparative effects as compared to IT male MSC.

Methods

Newborn Sprague-Dawley rats exposed to normoxia (RA) or hyperoxia (85% O2) from postnatal day (P) 2- P21 were randomly assigned to receive male or female IT bone marrow (BM)-derived green fluorescent protein (GFP⁺) MSC (1 x 10⁶ cells/50 μl), or Placebo on P7. Pulmonary hypertension (PH), vascular remodeling, alveolarization, and angiogenesis were assessed at P21. PH was determined by measuring right ventricular systolic pressure (RVSP) and pulmonary vascular remodeling was evaluated by quantifying the percentage of muscularized peripheral pulmonary vessels. Alveolarization was evaluated by measuring mean linear intercept (MLI) and radial alveolar count (RAC). Angiogenesis was determined by measuring vascular density. Data are expressed as mean ± SD, and analyzed by ANOVA.

Results

There were no significant differences in the RA groups. Exposure to hyperoxia resulted in a decrease in vascular density and RAC, with a significant increase in MLI, RVSP, and the percentage of partially and fully muscularized pulmonary arterioles. Administration of both male and female MSC significantly improved vascular density, alveolarization, RVSP, percent of muscularized vessels and alveolarization. Interestingly, the improvement in PH and vascular remodeling was more robust in the hyperoxic rodents who received MSC from female donors. In keeping with our hypothesis, male animals receiving female MSC, had a greater improvement in vascular remodeling. This was accompanied by a more significant decrease in lung pro-inflammatory markers and a larger increase in anti-inflammatory and pro-angiogenic markers in male rodents that received female MSC. There were no significant differences in MSC engraftment among groups.

Conclusions

Female BM-derived MSC have greater therapeutic efficacy than male MSC in reducing neonatal hyperoxia-induced lung inflammation and vascular remodeling. Furthermore, the beneficial effects of female MSC were more pronounced in male animals. Together, these findings suggest that female MSC maybe the most potent BM-derived MSC population for lung repair in severe BPD complicated by PH.

MEDXVIEWER: PROVIDING A WEB-ENABLED WORKSTATION ENVIRONMENT FOR COLLABORATIVE AND REMOTE MEDICAL IMAGING VIEWING, PERCEPTION STUDIES AND READER TRAINING

MedXViewer (Medical eXtensible Viewer) has been developed to address the need for workstation-independent, picture archiving and communication system (PACS)-less viewing and interaction with anonymised medical images. The aim of this paper is to describe the design and features of MedXViewer as well as to introduce the new features available in the latest release (version 1.2). MedXViewer currently supports digital mammography and tomosynthesis. The flexible software design used to develop MedXViewer allows it to be easily extended to support other imaging modalities. Regions of interest can be drawn by a user, and any associated information about a mark, an image or a study can be added. The questions and settings can be easily configured depending on the need of the research allowing both ROC and FROC studies to be performed. Complex tree-like questions can be asked where a given answer presents the user to new questions. The hanging protocol can be specified for each study. Panning, windowing, zooming and moving through slices are all available while modality-specific features can be easily enabled, e.g. quadrant zooming in digital mammography and tomosynthesis studies. MedXViewer can integrate with a web-based image database OPTIMAM Medical Image Database allowing results and images to be stored centrally. The software can, alternatively, run without a network connection where the images and results can be encrypted and stored locally on a machine or external drive. MedXViewer has been used for running remote paper-less observer studies and is capable of providing a training infrastructure and coordinating remote collaborative viewing sessions.

SIMULATING LOCAL DENSE AREAS USING PMMA TO ASSESS AUTOMATIC EXPOSURE CONTROL IN DIGITAL MAMMOGRAPHY

Current digital mammography (DM) X-ray systems are equipped with advanced automatic exposure control (AEC) systems, which determine the exposure factors depending on breast composition. In the supplement of the European guidelines for quality assurance in breast cancer screening and diagnosis, a phantom-based test is included to evaluate the AEC response to local dense areas in terms of signal-to-noise ratio (SNR). This study evaluates the proposed test in terms of SNR and dose for four DM systems. The glandular fraction represented by the local dense area was assessed by analytic calculations. It was found that the proposed test simulates adipose to fully glandular breast compositions in attenuation. The doses associated with the phantoms were found to match well with the patient dose distribution. In conclusion, after some small adaptations, the test is valuable for the assessment of the AEC performance in terms of both SNR and dose.

Site-specific associations of muscle thickness with bone mineral density in middle-aged and older men and women

It is unknown whether age-related site-specific muscle loss is associated with areal bone mineral density (aBMD) in older adults. To examine the relationships between aBMD and whole-body muscle thickness distribution, 97 healthy adults (46 women and 51 men) aged 50-78 years volunteered. Total and appendicular lean soft tissue mass, aBMD of the lumbar spine (LS-aBMD) and femoral neck (FN-aBMD) were determined using dual-energy X-ray absorptiometry. Muscle thickness (MT) was measured by ultrasound at nine sites of the body (forearm, upper arm, trunk, upper leg, and lower leg). Relationships of each co-variate with aBMD were tested partialling out the effect of age. aBMD was not correlated with either MT of the trunk or anterior lower leg in either sex. In men, significant and relatively strong correlations were observed between anterior and posterior upper arms, posterior lower leg, and anterior upper leg MT and LS-aBMD or FN-aBMD. In women, significant correlations were observed between anterior and posterior upper legs, posterior lower leg, and anterior upper arm MT and FN-aBMD. LS-aBMD was only correlated with forearm and posterior upper leg MT in women. In conclusion, the site-specific association of MT and aBMD differs between sexes and may be associated with the participants' daily physical activity profile.

Average glandular dose in digital mammography and digital breast tomosynthesis: comparison of phantom and patient data

For the evaluation of the average glandular dose (AGD) in digital mammography (DM) and digital breast tomosynthesis (DBT) phantoms simulating standard model breasts are used. These phantoms consist of slabs of polymethyl methacrylate (PMMA) or a combination of PMMA and polyethylene (PE). In the last decades the automatic exposure control (AEC) increased in complexity and became more sensitive to (local) differences in breast composition. The question is how well the AGD estimated using these simple dosimetry phantoms agrees with the average patient AGD. In this study the AGDs for both dosimetry phantoms and for patients have been evaluated for 5 different x-ray systems in DM and DBT modes. It was found that the ratios between patient and phantom AGD did not differ considerably using both dosimetry phantoms. These ratios averaged over all breast thicknesses were 1.14 and 1.15 for the PMMA and PMMA-PE dosimetry phantoms respectively in DM mode and 1.00 and 1.02 in the DBT mode. These ratios were deemed to be sufficiently close to unity to be suitable for dosimetry evaluation in quality control procedures. However care should be taken when comparing systems for DM and DBT since depending on the AEC operation, ratios for particular breast thicknesses may differ substantially (0.83-1.96). Although the predictions of both phantoms are similar we advise the use of PMMA  +  PE slabs for both DM and DBT to harmonize dosimetry protocols and avoid any potential issues with the use of spacers with the PMMA phantoms.

A Pilot Study on the Development of Remote Quality Control of Digital Mammography Systems in the NHS Breast Screening Programme

In the UK, physicists and radiographers perform routine quality control (QC) of digital mammography equipment at daily, weekly and monthly intervals. The tests performed and tolerances are specified by standard protocols. The manual nature of many of the tests introduces variability due to the positioning of regions of interest (ROIs) and can be time consuming. The tools on workstations provided by manufacturers limit the range of analysis that radiographers can perform and do not allow for a standard set of tools and analysis because they are specific to a given manufacturer. Automated software provides a means of reducing the variability in the analysis and also provides the possibility of additional, more complex analysis than is currently performed on the daily, weekly and monthly checks by radiographers. To this end, a set of tools has been developed to analyse the routine images taken by radiographers. As well as automatically reproducing the usual measurements by radiographers more complex analysis is provided. A QC image collection system has been developed which automatically routes QC data from a clinical site to a centralised server for analysis. A Web-based interface has been created that allows the users to view the performance of the mammographic equipment. The pilot system obtained over 3000 QC images from seven X-ray units at a single screening centre over 2 years. The results show that these tools and methods of analysis can highlight changes in a detector over time that may otherwise go unnoticed with the conventional analysis.

Dose assessment in contrast enhanced digital mammography using simple phantoms simulating standard model breasts

Slabs of polymethyl methacrylate (PMMA) or a combination of PMMA and polyethylene (PE) slabs are used to simulate standard model breasts for the evaluation of the average glandular dose (AGD) in digital mammography (DM) and digital breast tomosynthesis (DBT). These phantoms are optimized for the energy spectra used in DM and DBT, which normally have a lower average energy than used in contrast enhanced digital mammography (CEDM). In this study we have investigated whether these phantoms can be used for the evaluation of AGD with the high energy x-ray spectra used in CEDM. For this purpose the calculated values of the incident air kerma for dosimetry phantoms and standard model breasts were compared in a zero degree projection with the use of an anti scatter grid. It was found that the difference in incident air kerma compared to standard model breasts ranges between -10% to +4% for PMMA slabs and between 6% and 15% for PMMA-PE slabs. The estimated systematic error in the measured AGD for both sets of phantoms were considered to be sufficiently small for the evaluation of AGD in quality control procedures for CEDM. However, the systematic error can be substantial if AGD values from different phantoms are compared.

CXCR4 blockade attenuates hyperoxia-induced lung injury in neonatal rats

BACKGROUND

Lung inflammation is a key factor in the pathogenesis of bronchopulmonary dysplasia (BPD). Stromal-derived factor-1 (SDF-1) and its receptor chemokine receptor 4 (CXCR4) modulate the inflammatory response. It is not known if antagonism of CXCR4 alleviates lung inflammation in neonatal hyperoxia-induced lung injury.

OBJECTIVE

We aimed to determine whether CXCR4 antagonism would attenuate lung injury in rodents with experimental BPD by decreasing pulmonary inflammation.

METHODS

Newborn rats exposed to normoxia (room air, RA) or hyperoxia (FiO2 = 0.9) from postnatal day 2 (P2) to P16 were randomized to receive the CXCR4 antagonist, AMD3100 or placebo (PL) from P5 to P15. Lung alveolarization, angiogenesis and inflammation were evaluated at P16.

RESULTS

Compared to the RA pups, hyperoxic PL pups had a decrease in alveolarization, reduced lung vascular density and increased lung inflammation. In contrast, AMD3100-treated hyperoxic pups had improved alveolarization and increased angiogenesis. This improvement in lung structure was accompanied by a decrease in the macrophage and neutrophil counts in the bronchoalveolar lavage fluid and reduced lung myeloperoxidase activity.

CONCLUSION

CXCR4 antagonism decreases lung inflammation and improves alveolar and vascular structure in neonatal rats with experimental BPD. These findings suggest a novel therapeutic strategy to alleviate lung injury in preterm infants with BPD.

Estimation of scattered radiation in digital breast tomosynthesis

Digital breast tomosynthesis (DBT) is a promising technique to overcome the tissue superposition limitations found in planar 2D x-ray mammography. However, as most DBT systems do not employ an anti-scatter grid, the levels of scattered radiation recorded within the image receptor are significantly higher than that observed in planar 2D x-ray mammography. Knowledge of this field is necessary as part of any correction scheme and for computer modelling and optimisation of this examination. Monte Carlo (MC) simulations are often used for this purpose, however they are computationally expensive and a more rapid method of calculation is desirable. This issue is addressed in this work by the development of a fast kernel-based methodology for scatter field estimation using a detailed realistic DBT geometry. Thickness-dependent scatter kernels, which were validated against the literature with a maximum discrepancy of 4% for an idealised geometry, have been calculated and a new physical parameter (air gap distance) was used to estimate more accurately the distribution of scattered radiation for a series of anthropomorphic breast phantom models. The proposed methodology considers, for the first time, the effects of scattered radiation from the compression paddle and breast support plate, which can represent more than 30% of the total scattered radiation recorded within the image receptor. The results show that the scatter field estimator can calculate scattered radiation images in an average of 80 min for projection angles up to 25° with equal to or less than a 10% error across most of the breast area when compared with direct MC simulations.

Estimation of mean glandular dose for contrast enhanced digital mammography: factors for use with the UK, European and IAEA breast dosimetry protocols

The UK, European and IAEA protocols for breast dosimetry in mammography use tabulations of conversion factors, which relate measurements of incident air kerma to the mean glandular dose to the breast. To supplement the existing tabulations, a Monte Carlo computer program has been used to calculate conversion factors for the high-energy spectra used for contrast enhanced digital mammography. The calculations were made for the x-ray spectra from a tungsten target (tube voltage range 40-50 kV) filtered by 0.28, 0.30 and 0.32 mm of copper, and from molybdenum and rhodium targets (tube voltage range 40-49 kV), each filtered by 0.30 mm of copper. The g-factors for all of these spectra were plotted for each breast thickness as a function of half value layer (HVL) and were found to lie on smooth curves within 0.3%. These reflect the fact that the characteristic x-rays present in the spectra from molybdenum and rhodium are heavily filtered and all the spectra are essentially Bremsstrahlung. As a consequence, the s-factor previously used in the dosimetry protocols to adjust for different target/filter combinations can be taken as unity for all of the spectra considered. Tables of g-factors and c-factors are provided for breast thicknesses in the range 20-110 mm and HVLs in the range 2.4-3.6 mm of aluminium. The tables of c-factors are given for breast glandularities in the range 0.1%-100% and for typical glandularities for women in the age bands 40-49 and 50-64 attending the UK national breast screening programme.

Validation of simulation of calcifications for observer studies in digital mammography

Studies using simulated calcifications can be performed to measure the effect of different imaging factors on calcification detection in digital mammography. The simulated calcifications must be inserted into clinical images with realistic contrast and sharpness. MoCa is a program which modifies the contrast and sharpness of simulated calcification clusters extracted from images of mastectomy specimens acquired on a digital specimen cabinet at high magnification for insertion into clinical mammography images. This work determines whether the use of MoCa results in simulated calcifications with the correct contrast and sharpness. Aluminium foils (thickness 0.1-0.4 mm) and 1.60 µm thick gold discs (diameter 0.13-0.8 mm) on 0.5 mm aluminium were imaged with a range of thicknesses of polymethyl methacrylate (PMMA) using an amorphous selenium direct digital (DR) system and a powder phosphor computed radiography (CR) system (real images). Simulated images of the tests objects were also generated using MoCa. The contrast of the aluminium squares and the degradation of the contrast of the gold discs as a function of disc diameter were compared in the real and simulated images. The average ratios of the simulated-to-real aluminium contrasts over all aluminium and PMMA thicknesses were 1.03 ± 0.04 (two standard errors in the mean) and 0.99 ± 0.03 for the DR and CR systems, respectively. The ratio of the simulated-to-real degradations of contrast averaged over all disc diameters and PMMA thicknesses were 1.007 ± 0.008 and 1.002 ± 0.013 for DR and CR, respectively. The use of MoCa was accurate within the experimental errors.

Bone marrow-derived c-kit+ cells attenuate neonatal hyperoxia-induced lung injury

Recent studies suggest that bone marrow (BM)-derived stem cells have therapeutic efficacy in neonatal hyperoxia-induced lung injury (HILI). c-kit, a tyrosine kinase receptor that regulates angiogenesis, is expressed on several populations of BM-derived cells. Preterm infants exposed to hyperoxia have decreased lung angiogenesis. Here we tested the hypothesis that administration of BM-derived c-kit(+) cells would improve angiogenesis in neonatal rats with HILI. To determine whether intratracheal (IT) administration of BM-derived c-kit(+) cells attenuates neonatal HILI, rat pups exposed to either normobaric normoxia (21% O2) or hyperoxia (90% O2) from postnatal day (P) 2 to P15 were randomly assigned to receive either IT BM-derived green fluorescent protein (GFP)(+) c-kit(-) cells (PL) or BM-derived GFP(+) c-kit(+) cells on P8. The effect of cell therapy on lung angiogenesis, alveolarization, pulmonary hypertension, vascular remodeling, cell proliferation, and apoptosis was determined at P15. Cell engraftment was determined by GFP immunostaining. Compared to PL, the IT administration of BM-derived c-kit(+) cells to neonatal rodents with HILI improved alveolarization as evidenced by increased lung septation and decreased mean linear intercept. This was accompanied by an increase in lung vascular density, a decrease in lung apoptosis, and an increase in the secretion of proangiogenic factors. There was no difference in pulmonary vascular remodeling or the degree of pulmonary hypertension. Confocal microscopy demonstrated that 1% of total lung cells were GFP(+) cells. IT administration of BM-derived c-kit(+) cells improves lung alveolarization and angiogenesis in neonatal HILI, and this may be secondary to an improvement in the lung angiogenic milieu.

Comparison of the x-ray attenuation properties of breast calcifications, aluminium, hydroxyapatite and calcium oxalate

Aluminium is often used as a substitute material for calcifications in phantom measurements in mammography. Additionally, calcium oxalate, hydroxyapatite and aluminium are used in simulation studies. This assumes that these materials have similar attenuation properties to calcification, and this assumption is examined in this work. Sliced mastectomy samples containing calcification were imaged at ×5 magnification using a digital specimen cabinet. Images of the individual calcifications were extracted, and the diameter and contrast of each calculated. The thicknesses of aluminium required to achieve the same contrast as each calcification when imaged under the same conditions were calculated using measurements of the contrast of aluminium foils. As hydroxyapatite and calcium oxalate are also used to simulate calcifications, the equivalent aluminium thicknesses of these materials were also calculated using tabulated attenuation coefficients. On average the equivalent aluminium thickness was 0.85 times the calcification diameter. For calcium oxalate and hydroxyapatite, the equivalent aluminium thicknesses were 1.01 and 2.19 times the thickness of these materials respectively. Aluminium and calcium oxalate are suitable substitute materials for calcifications. Hydroxyapatite is much more attenuating than the calcifications and aluminium. Using solid hydroxyapatite as a substitute for calcification of the same size would lead to excessive contrast in the mammographic image.

Antagonism of CXCR7 attenuates chronic hypoxia-induced pulmonary hypertension

INTRODUCTION

Chemokines may directly participate in the pathogenesis of neonatal chronic hypoxia-induced pulmonary hypertension (PH). Although stromal-derived factor-1 (SDF-1) has been shown to be involved in PH, the role of its most recently discovered receptor, chemokine receptor type 7 (CXCR7), remains unclear. We sought to determine whether antagonism of the CXCR7 receptor would decrease pulmonary vascular remodeling in newborn mice exposed to chronic hypoxia by decreasing pulmonary vascular cell proliferation.

METHODS

Neonatal mice were exposed to hypoxia (fractional inspired oxygen concentration = 0.12) or room air (RA) for 2 wk. After 1 wk of exposure, mice received daily injections of placebo or a CXCR7 antagonist (CCX771) from postnatal day 7 (P7) to P14. Right ventricular systolic pressure (RVSP), the ratio of the weight of the right ventricle to left ventricle + septum (RV/LV + S), and pulmonary vascular cell proliferation and remodeling were determined at P14.

RESULTS

As compared with mice exposed to RA, hypoxia placebo mice had a significant increase in the lung protein expression of CXCR7. Although hypoxic placebo-treated mice had a significant increase in RVSP, RV/LV+S, and pulmonary vascular cell proliferation and remodeling, the administration of CCX771 markedly decreased these changes.

DISCUSSION

These results indicate that antagonism of CXCR7 may be a potent strategy to decrease PH and vascular remodeling.

Inter-limb musculoskeletal differences in competitive ten-pin bowlers: a preliminary analysis

OBJECTIVES

To compare musculoskeletal characteristics of the loaded and non-loaded forearm and upper leg of competitive ten-pin bowlers.

METHODS

10 competitive bowlers (30.6∓6.8 yrs) had their areal bone mineral density (aBMD) and body composition measured with Dual Energy X-ray Absorptiometry (DXA). Volumetric bone mineral density (vBMD) and bone characteristics were assessed at 4% and 66% of the limb length of each radius and 50% of the limb length of each femur using a pQCT. Bone and muscle characteristics of the loaded and non-loaded limbs were compared and analyzed using paired t-tests.

RESULTS

The loaded arm of competitive bowlers had significantly (p<0.05) greater bone free lean body mass (BFLBM) (5%) and ultra distal radius site (UD radius) aBMD (6.3%) compared to the non-loaded side. Cortical and trabecular vBMD was significantly (p<0.05) greater (1.3%, 4.8%) at the radius 66% and 4% sites in the loaded forearm, respectively. aBMD of the femoral neck, trochanter, and total hip were significantly greater (12.2-15.6%) in the slide leg. Total (5.2%) and cortical (9.2%) bone areas, total (8.2%) and cortical (8.7%) bone mineral content (BMC), and cortical wall thickness (9%) were significantly greater at the 50% femur site in the slide leg compared to the contralateral side.

CONCLUSION

The femoral shaft of bowlers adapts by increasing bone area and cortical thickness without a change in vBMD, while the loaded radius adapts by increasing vBMD.

Does current practice in the United States of carotid artery stent placement benefit asymptomatic octogenarians?

BACKGROUND AND PURPOSE

CAS or CEA for asymptomatic carotid stenosis is the focus of recently completed and ongoing randomized clinical trials. These techniques are widely utilized outside the setting of such trials. Therefore, our goal was to analyze the in-hospital stroke or death rates after CAS or CEA for asymptomatic stenosis that reflect current nationwide practice.

MATERIALS AND METHODS

Using sample-weighted ANOVA, we analyzed records from the 2006 and 2007 NIS, which are nationally representative cohorts for asymptomatic CAS or CEA. The primary outcome measure was a composite end point of in-hospital stroke, cardiac complications, or death. In-hospital stroke or death was a secondary outcome measure.

RESULTS

For ≥ 80 years of age, the in-hospital stroke, cardiac complications, or death rate after CAS was 4.9%, while the complication rate after CEA was 3.8%. The stroke or death rate after CAS was 2.7% for ≥ 80 years of age and was 1.5% after CEA for the same age group. Multivariate analysis showed that age (OR, 1.12; 95% CI, 0.97-1.3; P < .07) or procedure (OR, 1.12; 95% CI, 0.99-1.27; P < .14) was not associated with the composite end point of in-hospital stroke, cardiac complications, or death. In contrast, CAS (OR, 1.28; 95% CI, 1.03-1.58) and female sex (OR, 1.23; 95% CI, 1.04-1.45) were independently associated with in-hospital stroke or death following asymptomatic carotid revascularization. Hospital charges and hospital costs were lower for CEA than CAS (2007 costs: $7779 versus $12,104).

CONCLUSIONS

CAS is independently associated with increased in-hospital stroke or death (excluding cardiac complications from the composite outcome). In those ≥ 80 years of age, CAS as currently performed may not improve the natural history of asymptomatic carotid stenosis, because in-hospital stroke or death rates following CAS approached 3% in this group.

Estimation of mean glandular dose for breast tomosynthesis: factors for use with the UK, European and IAEA breast dosimetry protocols

A formalism is proposed for the estimation of mean glandular dose for breast tomosynthesis, which is a simple extension of the UK, European and IAEA protocols for dosimetry in conventional projection mammography. The formalism introduces t-factors for the calculation of breast dose from a single projection and T-factors for a complete exposure series. Monte Carlo calculations of t-factors have been made for an imaging geometry with full-field irradiation of the breast for a wide range of x-ray spectra, breast sizes and glandularities. The t-factors show little dependence on breast glandularity and tables are provided as a function of projection angle and breast thickness, which may be used for all x-ray spectra simulated. The T-factors for this geometry depend upon the choice of projection angles and weights per projection, but various example calculations gave values in the range 0.93-1.00. T-factors are also provided for the Sectra tomosynthesis system, which employs a scanned narrow-beam imaging geometry. In this quite different configuration, the factor (denoted T(S)) shows an important dependence on breast thickness, varying between 0.98 and 0.76 for 20 and 110 mm thick breasts, respectively. Additional data are given to extend the current tabulations of g-, c- and s-factors used for dosimetry of conventional 2D mammography.

Inhibition of the SDF-1/CXCR4 axis attenuates neonatal hypoxia-induced pulmonary hypertension

Exposure of the neonatal lung to chronic hypoxia produces significant pulmonary vascular remodeling, right ventricular hypertrophy, and decreased lung alveolarization. Given recent data suggesting that stem cells could contribute to pulmonary vascular remodeling and right ventricular hypertrophy, we tested the hypothesis that blockade of SDF-1 (stromal cell-derived factor 1), a key stem cell mobilizer or its receptor, CXCR4 (CXC chemokine receptor 4), would attenuate and reverse hypoxia-induced cardiopulmonary remodeling in newborn mice. Neonatal mice exposed to normoxia or hypoxia were randomly assigned to receive daily intraperitoneal injections of normal saline, AMD3100, or anti-SDF-1 antibody from postnatal day 1 to 7 (preventive strategy) or postnatal day 7 to 14 (therapeutic strategy). As compared to normal saline, inhibition of the SDF-1/CXCR4 axis significantly improved lung alveolarization and decreased pulmonary hypertension, right ventricular hypertrophy, vascular remodeling, vascular cell proliferation, and lung or right ventricular stem cell expressions to near baseline values. We therefore conclude that the SDF-1/CXCR4 axis both prevents and reverses hypoxia-induced cardiopulmonary remodeling in neonatal mice, by decreasing progenitor cell recruitment to the pulmonary vasculature, as well as by decreasing pulmonary vascular cell proliferation. These data offer novel insights into the role of the SDF-1/CXCR4 axis in the pathogenesis of neonatal hypoxia-induced cardiopulmonary remodeling and have important therapeutic implications.