Administration of Drugs/Gene Products to the Respiratory System: A Historical Perspective of the Use of Inert Liquids.

The present review is a historical perspective of methodology and applications using inert liquids for respiratory support and as a vehicle to deliver biological agents to the respiratory system. As such, the background of using oxygenated inert liquids (considered a drug when used in the lungs) opposed to an oxygen-nitrogen gas mixture for respiratory support is presented. The properties of these inert liquids and the mechanisms of gas exchange and lung function alterations using this technology are described. In addition, published preclinical and clinical trial results are discussed with respect to treatment modalities for respiratory diseases. Finally, this forward-looking review provides a comprehensive overview of potential methods for administration of drugs/gene products to the respiratory system and potential biomedical applications.

Pulmonary immune cell transcriptome changes in double-hit model of BPD induced by chorioamnionitis and postnatal hyperoxia.

BACKGROUND: Preterm infants with bronchopulmonary dysplasia (BPD) have lifelong increased risk of respiratory morbidities associated with environmental pathogen exposure and underlying mechanisms are poorly understood. The resident immune cells of the lung play vital roles in host defense. However, the effect of perinatal events associated with BPD on pulmonary-specific immune cells is not well understood. METHODS: We used a double-hit model of BPD induced by prenatal chorioamnionitis followed by postnatal hyperoxia, and performed a global transcriptome analysis of all resident pulmonary immune cells. RESULTS: We show significant up-regulation of genes involved in chemokine-mediated signaling and immune cell chemotaxis, and down-regulation of genes involved in multiple T lymphocyte functions. Multiple genes involved in T cell receptor signaling are downregulated and Cd8a gene expression remains downregulated at 2 months of age in spite of recovery in normoxia for 6 weeks. Furthermore, the proportion of CD8a+CD3+ pulmonary immune cells is decreased. CONCLUSIONS: Our study has highlighted that perinatal lung inflammation in a double-hit model of BPD results in short- and long-term dysregulation of genes associated with the pulmonary T cell receptor signaling pathway, which may contribute to increased environmental pathogen-associated respiratory morbidities seen in children and adults with BPD. IMPACT: In a translationally relevant double-hit model of BPD induced by chorioamnionitis and postnatal hyperoxia, we identified pulmonary immune cell-specific transcriptomic changes and showed that T cell receptor signaling genes are downregulated in short term and long term. This is the first comprehensive report delineating transcriptomic changes in resident immune cells of the lung in a translationally relevant double-hit model of BPD. Our study identifies novel resident pulmonary immune cell-specific targets for potential therapeutic modulation to improve short- and long-term respiratory health of preterm infants with BPD.

Screening Echocardiography and Brain Natriuretic Peptide Levels Predict Late Pulmonary Hypertension in Infants with Bronchopulmonary Dysplasia.

Through this study, we aimed to assess the ability of routine neonatal screening at time of bronchopulmonary dysplasia (BPD) diagnosis to predict the development of late pulmonary hypertension (PHTN). This is a retrospective longitudinal cohort study of 37 premature infants with BPD assessing the utility of screening serum brain natriuretic peptide (BNP) and echocardiograms performed at the time of BPD diagnosis ('early PHTN') to predict 'late PHTN' at the last follow-up. Screening evaluation demonstrated early PHTN in 9/37 patients. At an average follow-up interval of 52.7 ± 38.7 weeks, 4/9 had late PHTN; one patient without early PHT had late PHT. At initial screening, infants with late PHTN were significantly more likely to have demonstrated elevated BNP values (p = 0.003), and echocardiographic evidence of right atrial dilatation (p = 0.01), right ventricular hypertrophy (p = 0.01), lower right ventricular area change percentage (p = 0.03), and larger main pulmonary artery Z-scores (p = 0.02). Serum BNP and echocardiographic evaluation performed at the time of BPD diagnosis can detect patients at increased risk of late PHTN. Large, prospective studies are necessary to further address this question.

In utero gene editing for monogenic lung disease.

Monogenic lung diseases that are caused by mutations in surfactant genes of the pulmonary epithelium are marked by perinatal lethal respiratory failure or chronic diffuse parenchymal lung disease with few therapeutic options. Using a CRISPR fluorescent reporter system, we demonstrate that precisely timed in utero intra-amniotic delivery of CRISPR-Cas9 gene editing reagents during fetal development results in targeted and specific gene editing in fetal lungs. Pulmonary epithelial cells are predominantly targeted in this approach, with alveolar type 1, alveolar type 2, and airway secretory cells exhibiting high and persistent gene editing. We then used this in utero technique to evaluate a therapeutic approach to reduce the severity of the lethal interstitial lung disease observed in a mouse model of the human SFTPCI73T mutation. Embryonic expression of SftpcI73T alleles is characterized by severe diffuse parenchymal lung damage and rapid demise of mutant mice at birth. After in utero CRISPR-Cas9-mediated inactivation of the mutant SftpcI73T gene, fetuses and postnatal mice showed improved lung morphology and increased survival. These proof-of-concept studies demonstrate that in utero gene editing is a promising approach for treatment and rescue of monogenic lung diseases that are lethal at birth.

In utero CRISPR-mediated therapeutic editing of metabolic genes.

In utero gene editing has the potential to prenatally treat genetic diseases that result in significant morbidity and mortality before or shortly after birth. We assessed the viral vector-mediated delivery of CRISPR-Cas9 or base editor 3 in utero, seeking therapeutic modification of Pcsk9 or Hpd in wild-type mice or the murine model of hereditary tyrosinemia type 1, respectively. We observed long-term postnatal persistence of edited cells in both models, with reduction of plasma PCSK9 and cholesterol levels following in utero Pcsk9 targeting and rescue of the lethal phenotype of hereditary tyrosinemia type 1 following in utero Hpd targeting. The results of this proof-of-concept work demonstrate the possibility of efficiently performing gene editing before birth, pointing to a potential new therapeutic approach for selected congenital genetic disorders.

Inflammatory Response of Pulmonary Artery Smooth Muscle Cells Exposed to Oxidative and Biophysical Stress.

Pulmonary hypertension in the neonate requires treatment with oxygen and positive pressure ventilation, both known to induce lung injury. The direct response of pulmonary artery smooth muscle cells, the most abundant cells in the artery wall, to the stress of positive pressure and hyperoxia has not been previously studied. Pulmonary artery smooth muscle cells were cultured in temperature- and pressure-controlled air-tight chambers under conditions of positive pressure or hyperoxia for 24 h. Control cells were cultured in room air under atmospheric pressure. After the exposure period, culture medium was collected and samples were analyzed by ELISA, Human Cytokine 25-Plex Panel using a Luminex 200 analyzer and Western blot. Secretion of various inflammatory mediators, specifically IL-6, IL-8, IL-2R, MIP-1ß, MCP-1, IP-10, IL-7, IL-1RA, and IFN-α, was higher in the positive pressure and hyperoxia groups compared with control. The level of cyclin D1 was decreased in the hyperoxia and positive pressure group compared with control. Levels of fibronectin and α-smooth muscle actin were not different among the groups. Pulmonary artery smooth muscle cells directly produce multiple inflammatory mediators in response to oxidative and biophysical stress in vitro, which may be part of a cascade that leads to the vascular and perivascular changes in pulmonary hypertension.

Skeletal dysplasia: Respiratory management during infancy.

BACKGROUND: Skeletal dysplasia encompasses a variety of developmental disorders of the bone and cartilage that manifest as disproportionate shortening of limbs and trunk in the neonate. Many types of skeletal dysplasia are complicated by respiratory failure at or soon after birth and require intensive care and prolonged hospitalization. Respiratory complications in these infants are complex and are characterized by airway anomalies, restrictive lung disease due to a narrow and abnormally compliant chest wall, pulmonary hypoplasia, and central apnea. Appropriate management of these unique patients requires a clear understanding of the pathophysiology and use of pulmonary function tests for early recognition and management of complications. CONCLUSION: This review provides an overview of the underlying respiratory pathology and a practical guide to the newborn care provider for the diagnosis and management of respiratory complications in infants with skeletal dysplasia.

Lung Rest During Extracorporeal Membrane Oxygenation for Neonatal Respiratory Failure-Practice Variations and Outcomes.

OBJECTIVE: Describe practice variations in ventilator strategies used for lung rest during extracorporeal membrane oxygenation for respiratory failure in neonates, and assess the potential impact of various lung rest strategies on the duration of extracorporeal membrane oxygenation and the duration of mechanical ventilation after decannulation. DATA SOURCES: Retrospective cohort analysis from the Extracorporeal Life Support Organization registry database during the years 2008-2013. STUDY SELECTION: All extracorporeal membrane oxygenation runs for infants less than or equal to 30 days of life for pulmonary reasons were included. DATA EXTRACTION: Ventilator type and ventilator settings used for lung rest at 24 hours after extracorporeal membrane oxygenation initiation were obtained. DATA SYNTHESIS: A total of 3,040 cases met inclusion criteria. Conventional mechanical ventilation was used for lung rest in 88% of cases and high frequency ventilation was used in 12%. In the conventional mechanical ventilation group, 32% used positive end-expiratory pressure strategy of 4-6 cm H2O (low), 22% used 7-9 cm H2O (mid), and 43% used 10-12 cm H2O (high). High frequency ventilation was associated with an increased mean (SEM) hours of extracorporeal membrane oxygenation (150.2 [0.05] vs 125 [0.02]; p < 0.001) and an increased mean (SEM) hours of mechanical ventilation after decannulation (135 [0.09] vs 100.2 [0.03]; p = 0.002), compared with conventional mechanical ventilation among survivors. Within the conventional mechanical ventilation group, use of higher positive end-expiratory pressure was associated with a decreased mean (SEM) hours of extracorporeal membrane oxygenation (high vs low: 136 [1.06] vs 156 [1.06], p = 0.001; mid vs low: 141 [1.06] vs 156 [1.06]; p = 0.04) but increased duration of mechanical ventilation after decannulation in the high positive end-expiratory pressure group compared with low positive end-expiratory pressure (p = 0.04) among survivors. CONCLUSIONS: Wide practice variation exists with regard to ventilator settings used for lung rest during neonatal respiratory extracorporeal membrane oxygenation. Use of high frequency ventilation when compared with conventional mechanical ventilation and use of low positive end-expiratory pressure strategy when compared with mid positive end-expiratory pressure and high positive end-expiratory pressure strategy is associated with longer duration of extracorporeal membrane oxygenation. Further research to provide evidence to drive optimization of pulmonary management during neonatal respiratory extracorporeal membrane oxygenation is warranted.

Short-term weight gain velocity in infants with congenital diaphragmatic hernia (CDH).

BACKGROUND: Appropriate post-natal growth remains a mainstay of therapeutic goals for infants with CDH, with the hypothesis that optimizing linear growth will improve survival through functional improvements in pulmonary hypoplasia. However, descriptions of growth and the effect on survival are limited in affected infants. OBJECTIVE: Describe in-hospital weight gain related to survival among infants with CDH. DESIGN/METHODS: Children's Hospitals Neonatal Database (CHND) identified infants with CDH born ≥34weeks' gestation (2010-14). Exclusion criteria were: admission age>7days, death/discharge age<14days, or surgical CDH repair prior to admission. Weight gain velocity (WGV: g/kg/day) was calculated using an established exponential approximation and the cohort stratified by Q1: <25%ile, Q2-3: 25-75%ile, and Q4: >75%ile. Descriptive measures and unadjusted Kaplan-Meier analyses describe the implications of WGV on mortality/discharge. RESULTS: In 630 eligible infants, median WGV was 4.6g/kg/day. After stratification by WGV [Q1: (n=156; <3.1g/kg/day); Q2-3 (n=316; 3.1-5.9g/kg/day), and Q4 (n=158, >5.9g/kg/day)] infants in Q1 had shortest median length of stay, less time on TPN and intervention for gastro-esophageal reflux relative to the other WGV strata (p<0.01 for all). Unadjusted survival estimates revealed that Q1 [hazard ratio (HR)=9.5, 95% CI: 5.7, 15.8] and Q4 [HR=2.9, 95% CI: 1.7, 5.1, p<0.001 for both] WGV were strongly associated with NICU mortality relative to Q2-3 WGV. CONCLUSION: Variable WGV is evident in infants with CDH. Highest and lowest WGV appear to be related to adverse outcomes. Efforts are needed to develop nutritional strategies targeting optimal growth.

Gene Editing and Genetic Lung Disease. Basic Research Meets Therapeutic Application.

Although our understanding of the genetics and pathology of congenital lung diseases such as surfactant protein deficiency, cystic fibrosis, and alpha-1 antitrypsin deficiency is extensive, treatment options are lacking. Because the lung is a barrier organ in direct communication with the external environment, targeted delivery of gene corrective technologies to the respiratory system via intratracheal or intranasal routes is an attractive option for therapy. CRISPR/Cas9 gene-editing technology is a promising approach to repairing or inactivating disease-causing mutations. Recent reports have provided proof of concept by using CRISPR/Cas9 to successfully repair or inactivate mutations in animal models of monogenic human diseases. Potential pulmonary applications of CRISPR/Cas9 gene editing include gene correction of monogenic diseases in pre- or postnatal lungs and ex vivo gene editing of patient-specific airway stem cells followed by autologous cell transplant. Strategies to enhance gene-editing efficiency and eliminate off-target effects by targeting pulmonary stem/progenitor cells and the assessment of short-term and long-term effects of gene editing are important considerations as the field advances. If methods continue to advance rapidly, CRISPR/Cas9-mediated gene editing may provide a novel opportunity to correct monogenic diseases of the respiratory system.

Management of Supplemental Oxygen for Infants with Persistent Pulmonary Hypertension of Newborn: A Survey.

Objective To evaluate practice variations amongst neonatologists regarding oxygen management in neonates with persistent pulmonary hypertension of newborn (PPHN). Study Design An online survey was administered to neonatologists to assess goal oxygenation targets and oxygen titration practices in PPHN. Response variations were assessed and intergroup comparisons performed. Results Thirty-three percent (492) of neonatologists completed the survey. Twenty-eight percent reported using specific oxygen titration guidelines. Majority of respondents used a combination of oxygen saturation (SpO2) and arterial oxygen tension (PaO2) initially to titrate oxygen. Seventy percent of the respondents used higher goal SpO2 > 95% or 95 to 98% and thirty-eight percent of the respondents used PaO2 > 80 mm Hg. Physicians with extracorporeal membrane oxygenation experience and those with greater than ten years neonatal intensive care unit experience inclined toward use of SpO2 alone for oxygen titration and aimed for lower range of SpO2 and PaO2 targets. Greater proportion of neonatologists who employed specific oxygen titration guidelines used lower SpO2 targets. Conclusion Wide practice variations exist amongst neonatologists regarding optimal SpO2 and PaO2 targets and oxygen titration practices in the management of PPHN.

Inhibition of ß-catenin signaling improves alveolarization and reduces pulmonary hypertension in experimental bronchopulmonary dysplasia.

Bronchopulmonary dysplasia (BPD) is the most common and serious chronic lung disease of preterm infants. The development of pulmonary hypertension (PH) significantly increases the mortality and morbidity of this disease. ß-Catenin signaling plays an important role in tissue development and remodeling. Aberrant ß-catenin signaling is associated with clinical and experiment models of BPD. To test the hypothesis that inhibition of ß-catenin signaling is beneficial in promoting alveolar and vascular development and preventing PH in experimental BPD, we examined the effects of ICG001, a newly developed pharmacological inhibitor of ß-catenin, in preventing hyperoxia-induced BPD in neonatal rats. Newborn rat pups were randomized at postnatal day (P)2 to room air (RA) + DMSO (placebo), RA + ICG001, 90% FiO2 (O2) + DMSO, or O2 + ICG001. ICG001 (10 mg/kg) or DMSO was given by daily intraperitoneal injection for 14 days during continuous exposure to RA or hyperoxia. Primary human pulmonary arterial smooth muscle cells (PASMCs) were cultured in RA or hyperoxia (95% O2) in the presence of DMSO or ICG001 for 24 to 72 hours. Treatment with ICG001 significantly increased alveolarization and reduced pulmonary vascular remodeling and PH during hyperoxia. Furthermore, administering ICG001 decreased PASMC proliferation and expression of extracellular matrix remodeling molecules in vitro under hyperoxia. Finally, these structural, cellular, and molecular effects of ICG001 were associated with down-regulation of multiple ß-catenin target genes. These data indicate that ß-catenin signaling mediates hyperoxia-induced alveolar impairment and PH in neonatal animals. Targeting ß-catenin may provide a novel strategy to alleviate BPD in preterm infants.

Inhibition of LRP5/6-mediated Wnt/ß-catenin signaling by Mesd attenuates hyperoxia-induced pulmonary hypertension in neonatal rats.

BACKGROUND: Hyperoxia-induced neonatal lung injury is associated with activation of Wnt/ß-catenin signaling. Low-density lipoprotein receptor-related proteins 5 and 6 (LRP5/6) are Wnt coreceptors that bind to Wnt ligands and mediate canonical Wnt/ß-catenin signaling. We hypothesized that inhibition of LRP5/6 by their universal inhibitor, Mesd, would attenuate hyperoxia-induced lung injury. METHODS: Newborn rat pups were randomly exposed to normoxia or hyperoxia at 90% FiO2 and injected intraperitoneally with placebo or Mesd every other day for 14 d. On day 15, phosphorylation of LRP5/6 (pLRP5/6), expression of Wnt/ß-catenin target genes, cyclin D1 and Wnt-induced signaling protein-1 (WISP-1), right-ventricular systolic pressure (RVSP), right-ventricular hypertrophy (RVH), pulmonary vascular remodeling, alveolarization, and vascularization were measured. RESULTS: Hyperoxia exposure markedly induced pLRP5/6, cyclin D1, and WISP-1 expression in the lungs of placebo animals, but they were significantly attenuated by the administration of Mesd. Mesd also significantly attenuated hyperoxia-induced pulmonary hypertension (PH) and pulmonary vascular remodeling. However, there was no effect on alveolarization or vascularization after Mesd administration. CONCLUSION: This study demonstrates that LRP5/6 mediates pulmonary vascular remodeling and PH in hyperoxia-induced neonatal lung injury, thereby suggesting a potential therapeutic target to alleviate PH in neonates with severe bronchopulmonary dysplasia.

Targeting glycogen synthase kinase-3ß to prevent hyperoxia-induced lung injury in neonatal rats.

The pathological hallmarks of bronchopulmonary dysplasia (BPD), a chronic lung disease of premature infants, include inflammation, arrested alveolarization, and dysregulated angiogenesis. Severe BPD is often complicated by pulmonary hypertension (PH) that significantly increases morbidity and mortality. Glycogen synthase kinase (GSK)-3ß plays a pivotal role in embryonic development, cell proliferation and survival, and inflammation by modulating multiple signaling pathways, particularly the nuclear transcription factor, NF-κB, and Wnt/ß-catenin pathways. Aberrant GSK-3ß signaling is linked to BPD. We tested the hypothesis that inhibition of GSK-3ß is beneficial in preventing hyperoxia-induced neonatal lung injury, an experimental model of BPD. Newborn rats were exposed to normoxia or hyperoxia (90% oxygen), and received daily intraperitoneal injections of placebo (DMSO) or SB216763, a specific pharmacological inhibitor of GSK-3ß, for 14 days. Hyperoxia exposure in the presence of the placebo increased GSK-3ß phosphorylation, which was correlated with increased inflammation, decreased alveolarization and angiogenesis, and increased pulmonary vascular remodeling and PH. However, treatment with SB216763 decreased phosphorylation of NF-κB p65, expression of monocyte chemotactic protein-1, and lung inflammation during hyperoxia. Furthermore, treatment with the GSK-3ß inhibitor also improved alveolarization and angiogenesis, and decreased pulmonary vascular remodeling and PH. These data indicate that GSK-3ß signaling plays an important role in the pathogenesis of hyperoxia-induced neonatal lung injury, and that inhibition of GSK-3ß is beneficial in preventing inflammation and protecting alveolar and vascular structures during hyperoxia. Thus, targeting GSK-3ß signaling may offer a novel strategy to prevent and treat preterm infants with BPD.

Neonatal non-invasive respiratory support: physiological implications.

The introduction of assisted ventilation for neonatal pulmonary insufficiency has resulted in the successful treatment of many previously fatal diseases. During the past three decades, refinement of invasive mechanical ventilation techniques has dramatically improved survival of many high-risk neonates. However, as with many advances in medicine, while mortality has been reduced, morbidity has increased in the surviving high-risk neonate. In this regard, introduction of assisted ventilation has been associated with chronic lung injury, also known as bronchopulmonary dysplasia. This disease, unknown prior to the appearance of mechanical ventilation, has produced a population of patients characterized by ventilator or oxygen dependence with serious accompanying pulmonary and neurodevelopmental morbidity. The purpose of this article is to review non-invasive respiratory support methodologies to address the physiologic mechanisms by which these methods may prevent the pathophysiologic effects of invasive mechanical ventilation.

Pentoxifylline and prevention of hyperoxia-induced lung -injury in neonatal rats.

INTRODUCTION: Oxygen exposure plays an important role in the pathogenesis of bronchopulmonary dysplasia (BPD). The phosphodiesterase inhibitor pentoxifylline (PTX) has anti-inflammatory and antifibrotic effects in multiple organs. It was hypothesized that PTX would have a protective effect on hyperoxia-induced lung injury (HILI). METHODS: Newborn Sprague-Dawley rats were exposed to >95% oxygen (O(2)) and injected subcutaneously with normal saline (NS) or PTX (75 mg/kg) twice a day for 9 d. NS-injected, room air-exposed pups were controls. At days 4 and 9, lung tissue was collected to assess edema, antioxidant enzyme (AOE) activities, and vascular endothelial growth factor (VEGF) expression. At day 9, pulmonary macrophage infiltration, vascularization, and alveolarization were also examined. RESULTS: At day 9, treatment with PTX significantly increased survival from 54% to 88% during hyperoxia. Treatment with PTX significantly decreased lung edema and macrophage infiltration. PTX treatment increased lung AOE activities including those of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX). Furthermore, PTX treatment also increased the gene expression of VEGF189 and VEGF165, increased VEGF protein expression, and improved pulmonary vascularization. DISCUSSION: These data indicate that the reduced lung edema and inflammation, increased AOE activities, and improved vascularization may be responsible for the improved survival with PTX during hyperoxia. PTX may be a potential therapy in reducing some of the features of BPD in preterm newborns.

Connective tissue growth factor antibody therapy attenuates hyperoxia-induced lung injury in neonatal rats.

Despite recent advances in neonatal intensive care and surfactant therapy, bronchopulmonary dysplasia (BPD) continues to be one of the most common long-term pulmonary complications associated with preterm birth. Clinical efforts to prevent and treat BPD have been largely unsuccessful due to its multifactorial nature and poorly understood disease process. Connective tissue growth factor (CTGF) is a matricellular protein that plays an important role in tissue development and remodeling. Previous studies have demonstrated that hyperoxia exposure up-regulates CTGF expression in neonatal rat lungs. Whether CTGF overexpression plays a role in the pathogenesis of BPD, and whether CTGF antagonism has a therapeutic potential for BPD, are unknown. In the present study, we examined CTGF expression in lung autopsy specimens from patients with BPD and control subjects with no BPD. We assessed the effect of a CTGF-neutralizing monoclonal antibody (CTGF Ab) on preventing hyperoxia-induced lung injury in neonatal rats. Our study demonstrates that CTGF expression is increased in BPD lungs. In newborn rats, exposure to 90% oxygen for 14 days resulted in activation of ß-catenin signaling, decreased alveolarization and vascular development, and physiological and histological evidence of pulmonary hypertension (PH). However, treatment with CTGF Ab prevented ß-catenin signaling activation, improved alveolarization and vascular development, and attenuated PH during hyperoxia. These data indicate that CTGF-ß-catenin signaling plays a critical role in the pathogenesis of experimental BPD. CTGF antagonism may offer a novel therapeutic strategy to alleviate BPD and PH in neonates.