Effects of positive end-expiratory pressure, inhaled nitric oxide and surfactant on expression of proinflammatory cytokines and growth factors in preterm piglet lungs

Exosomal miR-223 promotes ARDS by targeting insulin-like growth factor 1 receptor: A cell communication study

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a respiratory failure syndrome characterized by hypoxemia and changes in the respiratory system. ARDS is the most common cause of death in COVID-19 deaths was ARDS. In this study, we explored the role of miR-223 in exosomes in ARDS.

METHODS

Exosomes were purified from the supernatants of macrophages. qPCR was used to detect relative mRNA levels. A luciferase reporter assay was performed to verify the miRNA target genes. Western blotting was used to detect the activation of inflammatory pathways. Flow cytometry was performed to assess apoptosis. An LPS-induced ARDS mouse model was used to assess the function of miR-223 in ARDS.

RESULTS

Exosomes secreted by macrophages promoted apoptosis in A549 cells. Macrophages and exosomes contain high levels of miR-223. Exogenous miR-223 can decrease the expression of insulin-like growth factor 1 receptor (IGF-1R) in A549 and promote the apoptosis of A549.Transfection of anti-miR223 antisense nucleotides effectively reduced the level of miR-223 in macrophages and exosomes and eliminated the pro-apoptotic effect of A549. In vivo, LPS stimulation increased inflammatory cell infiltration in the lungs of mice, whereas knockdown of miR-223 in mice resulted in significantly reduced eosinophil infiltration.

CONCLUSIONS

Macrophages can secrete exosomes containing miR-223 and promote apoptosis by targeting the IGF-1R/Akt/mTOR signaling pathway in A549 cells and mouse models, suggesting that miR-223 is a potential target for treating COVID-19 induced ARDS.

Preterm pigs for preterm birth research: reasonably feasible

Preterm birth will disrupt the pattern and course of organ development, which may result in morbidity and mortality of newborn infants. Large animal models are crucial resources for developing novel, credible, and effective treatments for preterm infants. This review summarizes the classification, definition, and prevalence of preterm birth, and analyzes the relationship between the predicted animal days and one human year in the most widely used animal models (mice, rats, rabbits, sheep, and pigs) for preterm birth studies. After that, the physiological characteristics of preterm pig models at different gestational ages are described in more detail, including birth weight, body temperature, brain development, cardiovascular system development, respiratory, digestive, and immune system development, kidney development, and blood constituents. Studies on postnatal development and adaptation of preterm pig models of different gestational ages will help to determine the physiological basis for survival and development of very preterm, middle preterm, and late preterm newborns, and will also aid in the study and accurate optimization of feeding conditions, diet- or drug-related interventions for preterm neonates. Finally, this review summarizes several accepted pediatric applications of preterm pig models in nutritional fortification, necrotizing enterocolitis, neonatal encephalopathy and hypothermia intervention, mechanical ventilation, and oxygen therapy for preterm infants.

Efficacy of perinatal pharmacotherapeutic actions for survival of very preterm newborn rabbits at 26-day gestation

Investigation of the pathophysiology of lung impairment and protection in very preterm neonates at birth requires adequate experimental models. This study aimed to elucidate the efficacy and mechanism of perinatal pharmacotherapeutic action in postnatal survival of very preterm rabbits. Pregnant New Zealand White rabbits on 25-day gestation (term 31 days) were given dexamethasone (D), or sham injection as control (C), and cesarean delivered 24 hours later on day 26. Newborns were anesthetized, intratracheally intubated, randomly received either saline or porcine surfactant (S), allocated to four groups (C, S, D, and DS), and ventilated with low tidal volume. Under the identical protocol, another four groups were added with nitric oxide (N) inhalation (CN, SN, DN, and DSN). Survival length, lung mechanics, histopathology, and pathobiology of lung tissue were measured for benefits and injury patterns. DSN had the longest median survival time (ST50, 10.3 h), whereas C had the shortest (3.5 h), with remaining groups in-between. The survival was mainly benefited by S, when additive effects with D and/or N were discernible, by improved lung mechanics and alveolar aeration, ameliorated lung injury severity and pneumothorax, and augmented lung phospholipid pools, with DSN being the most optimal. Variable mRNA expression profiles of alveolar epithelia-associated cytokines and inflammatory mediators further characterized injury and response patterns as phenotyping conditioned in pharmacotherapeutic actions. In conclusion, the combined regimens of perinatal medications achieved remarkable survival in very preterm rabbits with lung protective ventilation strategy, offering a unique model in investigation of very preterm birth-associated respiratory physiology and morbidities.NEW & NOTEWORTHY By establishing a very preterm rabbit model with 26-day gestation (term 31 days), optimal survival length for 50% of animals in groups was achieved by comparing regimens of combined antenatal glucocorticoids, postnatal surfactant and inhaled nitric oxide, with a low tidal volume ventilation strategy. The efficacies of pharmacotherapeutic action were associated with significantly improved lung mechanics, ameliorated lung injury and pneumothorax, and enhanced surfactant phospholipid metabolism, along with variable mRNA expression profiles characterizing the response patterns.

Intratracheal Keratinocyte Growth Factor Enhances Surfactant Protein B Expression in Mechanically Ventilated Preterm Pigs

Bronchopulmonary dysplasia (BPD) is a devastating disease of prematurity that is associated with mechanical ventilation and hyperoxia. We used preterm pigs delivered at gestational day 102 as a translational model for 26-28-week infants to test the hypothesis administering recombinant human keratinocyte growth factor (rhKGF) at initiation of mechanical ventilation will stimulate type II cell proliferation and surfactant production, mitigate ventilator induced lung injury, and reduce epithelial to mesenchymal transition considered as a precursor to BPD. Newborn preterm pigs were intubated and randomized to receive intratracheal rhKGF (20 μg/kg; n = 6) or saline (0.5 ml 0.9% saline; control; n = 6) before initiating 24 h of ventilation followed by extubation to nasal oxygen for 12 h before euthanasia and collection of lungs for histopathology and immunohistochemistry to assess expression of surfactant protein B and markers of epithelial to mesenchymal transition. rhKGF pigs required less oxygen during mechanical ventilation, had higher tidal volumes at similar peak pressures indicative of improved lung compliance, and survival was higher after extubation (83% vs. 16%). rhKGF increased surfactant protein B expression (p < 0.05) and reduced TGF-1β (p < 0.05), that inhibits surfactant production and is a prominent marker for epithelial to mesenchymal transition. Our findings suggest intratracheal administration of rhKGF at initiation of mechanical ventilation enhances surfactant production, reduces ventilator induced lung injury, and attenuates epithelial-mesenchymal transition while improving pulmonary functions. rhKGF is a potential therapeutic strategy to mitigate pulmonary responses of preterm infants that require mechanical ventilation and thereby reduce the incidence and severity of bronchopulmonary dysplasia.

The Neonatal and Juvenile Pig in Pediatric Drug Discovery and Development

Pharmacotherapy in pediatric patients is challenging in view of the maturation of organ systems and processes that affect pharmacokinetics and pharmacodynamics. Especially for the youngest age groups and for pediatric-only indications, neonatal and juvenile animal models can be useful to assess drug safety and to better understand the mechanisms of diseases or conditions. In this respect, the use of neonatal and juvenile pigs in the field of pediatric drug discovery and development is promising, although still limited at this point. This review summarizes the comparative postnatal development of pigs and humans and discusses the advantages of the juvenile pig in view of developmental pharmacology, pediatric diseases, drug discovery and drug safety testing. Furthermore, limitations and unexplored aspects of this large animal model are covered. At this point in time, the potential of the neonatal and juvenile pig as nonclinical safety models for pediatric drug development is underexplored.

Effects of inhaled nitric oxide for postoperative hypoxemia in acute type A aortic dissection: a retrospective observational study

Background

Postoperative hypoxemia in acute type A aortic dissection (AADA) is a common complication and is associated with negative outcomes. This study aimed to analyze the efficacy of low-dose (5–10 ppm) inhaled nitric oxide (iNO) in the management of hypoxemia after AADA surgery.

Methods

In this retrospective observational study, Medical records of patients who underwent AADA surgery at two institutions between January 2015 and January 2018 were collected. Patients with postoperative hypoxemia were classified as iNO and control groups. Clinical characteristics and outcomes were compared using a propensity score-matched (PSM) analysis.

Results

Among 436 patients who underwent surgical repair, 187 (42.9%) had hypoxemia and 43 were treated with low-dose iNO. After PSM, patients were included in the iNO treatment (n = 40) and PSM control (n = 94) groups in a 1:3 ratio. iNO ameliorated hypoxemia at 6, 24, 48, and 72 h after initiation, and shortened the durations of ventilator support (39.0 h (31.3–47.8) vs. 69.0 h (47.8–110.3), p < 0.001) and ICU stay (122.0 h (80.8–155.0) vs 179.5 h (114.0–258.0), p < 0.001). There were no significant between-group differences in mortality, complications, or length of hospital stay.

Conclusions

In this study, we found that low-dose iNO improved oxygenation in patients with hypoxemia after AADA surgery and shortened the durations of mechanical ventilation and ICU stay. No significant side effects or increase in postoperative mortality or morbidities were observed with iNO treatment. These findings warrant a randomized multicenter controlled trial to assess the exact efficiency of iNO for hypoxemia after AADA.

Suppression of pulmonary group B streptococcal proliferation and translocation by surfactants in ventilated near-term newborn rabbits

BACKGROUND

The pathogenesis of neonatal group B Streptococcus (GBS) lung infection may be associated with surfactant dysfunction or deficiency. This study aimed to investigate the efficacy of surfactants on early postnatal GBS infection in ventilated newborn rabbit lungs.

METHODS

A near-term newborn rabbit model was established by intratracheal GBS instillation immediately at birth, followed by mechanical ventilation. At postnatal 1 h, a porcine surfactant was given intratracheally at 100 or 200 mg/kg. After 6 h, animals were euthanized, and lung and blood samples were collected for bacterial counting. Lung histopathology and messenger RNA (mRNA) expression of inflammatory mediators, surfactant proteins, and growth factors in lung tissue were assessed.

RESULTS

The surfactants significantly suppressed (by >50%) pulmonary bacterial proliferation and systemic translocation, alleviated lung inflammatory injury, and improved alveolar expansion by morphometry, in favor of high-dose surfactants. Though the survival rate and lung mechanics were not improved, the surfactants significantly suppressed mRNA expression of proinflammatory mediators, while that for surfactant proteins and growth factors was differentially expressed, compared to the control and GBS infection groups.

CONCLUSION

Exogenous surfactants may provide a therapeutic alternative for neonatal lung infection by suppressing pulmonary GBS proliferation and translocation into systemic circulation, alleviating inflammatory injury and regulating growth factor expression.

Limiting ventilator-associated lung injury in a preterm porcine neonatal model

PURPOSE

Preterm infants are prone to respiratory distress syndrome (RDS), with severe cases requiring mechanical ventilation for support. However, there are no clear guidelines regarding the optimal ventilation strategy. We hypothesized that airway pressure release ventilation (APRV) would mitigate lung injury in a preterm porcine neonatal model.

METHODS

Preterm piglets were delivered on gestational day 98 (85% of 115day term), instrumented, and randomized to volume guarantee (VG; n=10) with low tidal volumes (5.5cm³kg^-1) and PEEP 4cmH₂O or APRV (n=10) with initial ventilator settings: P_High 18cmH₂O, P_Low 0cmH₂O, T_High 1.30s, T_Low 0.15s. Ventilator setting changes were made in response to clinical parameters in both groups. Animals were monitored continuously for 24hours.

RESULTS

The mortality rates between the two groups were not significantly different (p>0.05). The VG group had relatively increased oxygen requirements (F_iO₂ 50%±9%) compared with the APRV group (F_iO₂ 28%±5%; p>0.05) and a decrease in PaO₂/FiO₂ ratio (VG 162±33mmHg; APRV 251±45mmHg; p<0.05). The compliance of the VG group (0.51±0.07L·cmH₂O^-1) was significantly less than the APRV group (0.90±0.06L·cmH₂O^-1; p<0.05).

CONCLUSION

This study demonstrates that APRV improves oxygenation and compliance as compared with VG. This preliminary work suggests further study into the clinical uses of APRV in the neonate is warranted.

LEVEL OF EVIDENCE

Not Applicable (Basic Science Animal Study).

Exhaled nitric oxide is associated with postnatal adaptation to hypoxia in Tibetan and non-Tibetan newborn infants

AIM

This Chinese study assessed partial pressure of exhaled nitric oxide (PeNO) in healthy Tibetan and non-Tibetan newborn infants born at a very high altitude.

METHODS

Full-term Tibetan and non-Tibetan neonates born in Lhasa, 3658 metres above sea level, were compared to non-Tibetan neonates born in Kunming (1891 m) and Huai'an (16 m). The chemiluminiscence technique was used to measure the fraction of exhaled nitric oxide during spontaneous tidal breathing and this was then converted to partial pressure of exhaled nitric oxide (PeNO).

RESULTS

In their first week, Tibetan and non-Tibetan neonates born in Lhasa had persistently higher PeNO levels than non-Tibetan neonates born in Kunming and Huai'an, which was further verified by partial pressure of inspired oxygen adjustment. However, the non-Tibetans born in Lhasa required short-term oxygen therapy to improve their early postnatal oxygenation. The temporal changes of PeNO and cardio-respiratory function measurements demonstrated that Tibetan and non-Tibetan newborns in Lhasa initially needed to adapt to attain homoeostasis in oxygenation and gas exchange.

CONCLUSION

Tibetan and non-Tibetan newborn infants living at the same high altitude demonstrated comparable PeNO levels during postnatal adaptation to hypobaric hypoxia, which warrants further investigation of the mechanism of endogenous nitric oxide and hypoxic tolerance.

A preterm pig model of lung immaturity and spontaneous infant respiratory distress syndrome

Respiratory distress syndrome (RDS) and bronchopulmonary dysplasia remain the leading causes of preterm infant morbidity, mortality, and lifelong disability. Research to improve outcomes requires translational large animal models for RDS. Preterm pigs delivered by caesarian section at gestation days (GD) 98, 100, 102, and 104 were provided 24 h of neonatal intensive care, monitoring (pulse oximetry, blood gases, serum biomarkers, radiography), and nutritional support, with or without intubation and mechanical ventilation (MV; pressure control ventilation with volume guarantee). Spontaneous development of RDS and mortality without MV are inversely related with GD at delivery and correspond with inadequacy of tidal volume and gas exchange. GD 98 and 100 pigs have consolidated lungs, immature alveolar architecture, and minimal surfactant protein-B expression, and MV is essential at GD 98. Although GD 102 pigs had some alveoli lined by pneumocytes and surfactant was released in response to MV, blood gases and radiography revealed limited recruitment 1-2 h after delivery, and mortality at 24 h was 66% (35/53) with supplemental oxygen provided by a mask and 69% (9/13) with bubble continuous positive airway pressure (8-9 cmH2O). The lungs at GD 104 had higher densities of thin-walled alveoli that secreted surfactant, and MV was not essential. Between GD 98 and 102, preterm pigs have ventilation inadequacies and risks of RDS that mimic those of preterm infants born during the saccular phase of lung development, are compatible with standards of neonatal intensive care, and are alternative to fetal nonhuman primates and lambs.

Inhaled NO contributes to lung repair in piglets with acute respiratory distress syndrome via increasing circulating endothelial progenitor cells

Background

Nitric oxide (NO) plays an important role in mobilization of endothelial progenitor cells (EPCs). We hypothesized that inhaled NO (iNO) would induce EPC mobilization and therefore promote lung repair in acute respiratory distress syndrome (ARDS).

Methodology/Principal Findings

Healthy piglets were randomized into four groups (n = 6): Control (Con; mechanical ventilation only); ARDS (established by oleic acid infusion and mechanical ventilation); ARDS plus granulocyte-colony stimulating factor (G-CSF; 10 µg/kg/d subcutaneously); ARDS plus NO inhalation (iNO; 10 ppm). EPCs and mobilizing cytokines were assayed at different time points (baseline, 0, 24, 72 and 168 h) and injury reparation was assessed at 168 h. Compared to the Con group, the levels of EPCs were increased in bone marrow but not in blood in the ARDS group at 24 h. Compared to the ARDS group, inhaled NO induced a rapid elevation in the number of CD34⁺KDR⁺, KDR⁺CD133⁺ and CD34⁺KDR⁺CD133⁺ EPCs in blood (2163±454 vs. 1094±416, 1302±413 vs. 429±244, 1140±494 vs. 453±273 cells/ml, respectively, P<0.05), and a reduction in the percentage of KDR⁺CD133⁺ cells in bone marrow. Lung CD34, CD133, VEGF, VEGF receptor 2, endothelial NO synthase mRNA, and VEGF and VEGF receptor 2 protein expression levels were augmented in the iNO group, but not in the G-CSF group, compared to ARDS. Furthermore, iNO treatment reduced vascular permeability, increased pulmonary vessel density, and alleviated pulmonary edema and inflammation compared to ARDS treatment. Plasma VEGF, stromal cell-derived factor-1 (SDF-1) and bone marrow NO₂⁻/NO₃⁻ were significantly higher in the iNO group compared to the ARDS group at 72 h.

Conclusions

These results suggest that iNO induces mobilization of EPCs from bone marrow into circulation, contributes to vascular repair, and thereby alleviates lung damage.

Current technology in the diagnosis of developmentally related lung disorders

Respiratory disorders that present in the newborn period may result from structural, functional, or acquired mechanisms that limit gas exchange between the airspace and vascular bed. Exciting new imaging, gene sequencing, mass spectrometry, and molecular and cell-based techniques are enhancing our understanding of mechanisms of disease; highlighting the complexity of interactions between genes, development, and environment in the manifestation of health and disease; and becoming part of the clinical armamentarium for the care of patients. Some of these technologies and their clinical potential are briefly reviewed in this paper.

Transforming growth factor-beta modulates the expression of nitric oxide signaling enzymes in the injured developing lung and in vascular smooth muscle cells

Nitric oxide signaling has an important role in regulating pulmonary development and function. Expression of soluble guanylate cyclase (sGC) and cGMP-dependent protein kinase I (PKGI), both critical mediators of nitric oxide (NO) signaling, is diminished in the injured newborn lung through unknown mechanisms. Recent studies suggest that excessive transforming growth factor-beta (TGF-beta) activity inhibits injured newborn lung development. To explore mechanisms that regulate pulmonary NO signaling, we tested whether TGF-beta decreases sGC and PKGI expression in the injured developing lung and pulmonary vascular smooth muscle cells (SMC). We found that chronic oxygen-induced lung injury decreased pulmonary sGCalpha(1) and PKGI immunoreactivity in mouse pups and that exposure to a TGF-beta-neutralizing antibody prevented this reduction of sGC and PKGI protein expression. In addition, TGF-beta(1) decreased expression of NO signaling enzymes in freshly isolated pulmonary microvascular SMC/myofibroblasts, suggesting that TGF-beta has a direct role in modulating NO signaling in the pup lung. Moreover, TGF-beta(1) decreased sGC and PKGI expression in pulmonary artery and aortic SMC from adult rats and mice, suggesting a general role for TGF-beta in modulating NO signaling in vascular SMC. Although other cytokines decrease sGC mRNA stability, TGF-beta did not modulate sGCalpha(1) or PKGIbeta mRNA turnover in vascular SMC. These studies indicate for the first time that TGF-beta decreases NO signaling enzyme expression in the injured developing lung and pulmonary vascular SMC. Moreover, they suggest that TGF-beta-neutralizing molecules might counteract the effects of injury on NO signaling in the newborn lung.