Chung Ming Chen

Methylprednisolone effects on oxygenation and histology in a rat model of acute lung injury

We examined the effects of methylprednisolone on gas exchange, pressure-volume curve, lavage fluid inflammatory cell counts, protein content, surfactant pool size, and lung histology in a rat model of paraquat-induced lung injury. Twenty-three adult male Sprague-Dawley rats received intraperitoneal paraquat injection (35 mg/kg) and were randomly divided into three groups: (1). control group received no further treatment; (2). 1-dose methylprednisolone group received a concomitant intraperitoneal methylprednisolone injection (30 mg/kg); (3). 3-dose methylprednisolone group received a concomitant and daily intraperitoneal methylprednisolone injection (30 mg/kg) for three doses. Three days after paraquat injection, the rat was ventilated for 90 min, a static pressure-volume curve and bronchoalveolar lavage was performed, and postmortem histology was examined. Surfactant pool size of the 3-dose methylprednisolone group was significantly increased when compared with the control and 1-dose methylprednisolone groups. Methylprednisolone treatment increased oxygenation and the value was statistically significant for 3-dose methylprednisolone group at 90 min of ventilation. Inflammatory cell counts in bronchoalveolar lavage fluid and lung injury score were decreased as the methylprednisolone dose increased. We conclude that high-dose methylprednisolone treatment increased surfactant pool size and improved lung histology of paraquat-injured lungs but this augmentation could not significantly improve oxygenation throughout the ventilation period.

Neonatal Hyperoxia Exposure Induces Kidney Fibrosis in Rats

BACKGROUNDnHuman and animal studies have demonstrated that neonatal hyperoxia increases oxidative stress and adversely affects glomerular and tubular maturity. This study was undertaken to determine how exposure to neonatal hyperoxia affected kidney morphology and fibrosis and to elucidate the relationship between connective tissue growth factor (CTGF) and collagen expression in rat kidneys.nnnMETHODSnSprague-Dawley rat pups were exposed to either hyperoxia or ambient air. The control groups were maintained in ambient air for 1 week and 3 weeks. The hyperoxia groups were exposed to >95% O2 for 1 week and subsequently placed in an environment of 60% O2 for an additional 2 weeks. The animals were euthanized on Postnatal Day 7 or 21 and the kidneys underwent histological analyses and oxidative stress and total collagen measurements.nnnRESULTSnThe rats reared in O2-enriched air exhibited significantly higher tubular injury scores (1.4xa0±xa00.5 vs. 0.7xa0±xa00.7 on Day 7; 1.4xa0±xa00.5 vs. 0.6xa0±xa00.5 on Day 21), a larger proportion of the cortex occupied by glomeruli (25.5xa0±xa04.1 vs. 21.3xa0±xa03.1% on Day 7; 20.1xa0±xa03.5 vs. 17.1xa0±xa01.7% on Day 21), larger glomerular sizes (84.7xa0±xa05.8 vs. 77.5xa0±xa06.1xa0μm on Day 7; 88.4xa0±xa02.9 vs. 84.9xa0±xa03.1xa0μm on Day 21), and higher total collagen content (54.1xa0±xa027.5 vs. 18.3xa0±xa06.3xa0μg/mg protein on Day 7; 397.4xa0±xa032.8 vs. 289.5xa0±xa080.0xa0μg/mg protein on Day 21) than did rats reared in ambient air. Immunohistochemical expressions of oxidative stress marker 8-hydroxy-2-deoxyguanosine and CTGF immunoreactivities were significantly higher in the rats reared in O2-enriched air compared with the rats reared in ambient air on Postnatal Days 7 and 21.nnnCONCLUSIONnNeonatal hyperoxia exposure contributes to kidney fibrosis, which is probably caused by activated CTGF expression.

Downregulation of Caveolin-1 in a Murine Model of Acute Allergic Airway Disease

BACKGROUNDnAirway remodeling refers to the structural changes in the airways of asthma. Caveolin-1 reduces cell growth and negatively regulates smooth muscle cell proliferation. The aim was to investigate lung caveolin-1 status in a murine model of acute allergic airway disease.nnnMETHODSnSix- to eight-week-old female BALB/c mice were sensitized by intraperitoneal injections of phosphate-buffered saline or ovalbumin (OVA) and aluminium hydroxide on Days 0 and 14, challenged with aerosolized saline or OVA (1%) on Days 21-25, 28-32, and 35. The mice were killed 1 day after the last OVA/saline challenge. Serum OVA-specific immunoglobulin E (IgE) was measured by enzyme-linked immunosorbent assay. Peribronchial inflammation was quantified by morphometric analysis. Lung caveolin-1 and Type I collagen mRNA expression was determined by real-time reverse-transcription polymerase chain reaction. Total lung collagen was measured using Sircol Assay Kit.nnnRESULTSnSerum OVA-specific IgE levels were significantly elevated in OVA-challenged mice when compared with saline-challenged mice. Percentage of inflammatory cells in the bronchoalveolar lavage was significantly higher in the OVA-challenged animals. The animals lungs that were sensitized and challenged with OVA contained large numbers of inflammatory cells concentrated near the airways and in the perivascular areas. The thickness of the bronchial epithelial layer and smooth muscle layer and the numbers of total inflammatory cells and eosinophils significantly increased in OVA-challenged mice. Caveolin-1 mRNA expression significantly decreased and Type I collagen mRNA expression significantly increased in the lung tissue of OVA-challenged mice.nnnCONCLUSIONnThese results suggest that caveolin-1 seems to be involved in the pathogenesis of airway remodeling of acute allergic airway disease.

Effect of surfactant and budesonide on the pulmonary distribution of fluorescent dye in mice

BACKGROUNDnSurfactant is a useful vehicle for the intratracheal delivery of medicine to the distal lung. The aim of this study was to analyze the effect of intratracheal surfactant and budesonide instillation on the pulmonary distribution of fluorescent dye in mice.nnnMETHODSnMale athymic nude mice were assigned randomly as controls, fluorescent dye, fluorescent dyexa0+xa0surfactant (50xa0mg/kg), fluorescent dyexa0+xa0budesonide (0.25xa0mg/kg), and fluorescent dyexa0+xa0surfactantxa0+xa0budesonide groups. A total volume of 60xa0μL fluorescent solutions was intratracheally injected and followed by 60xa0μL of air. We photographed and measured fluorescence in the lungs, from the back, 15 minutes after intratracheal administration using an IVIS Xenogen imaging instrument.nnnRESULTSnThe fluorescent dye (1,1-dioctadecyltetramethyl indotricarbocyanine iodide) was most strongly detected near the trachea and weakly detected in the lungs in mice administered with fluorescent solutions. Almost no fluorescence was seen in the lung region of control mice. Intratracheal administration of surfactant or budesonide increased fluorescent intensity compared with control mice. Combined administration of surfactant and budesonide further increased fluorescent intensity compared with mice given surfactant or budesonide alone.nnnCONCLUSIONnSurfactant and budesonide enhance the pulmonary distribution of fluorescent dye in mice.

Pulmonary Hypoplasia Induced by Oligohydramnios: Findings from Animal Models and a Population-Based Study

Pulmonary hypoplasia is a substantial cause of death in newborn infants, and oligohydramnios is one of the most commonly associated abnormalities. Lung growth is influenced by physical factors such as the intrauterine space, lung liquid volume and pressure, and fetal breathing movements. During lung development, the main physical force experienced by the lungs is stretching induced by breathing movements and the lung fluid in the airspaces. Oligohydramnios reduces the intrathoracic cavity size, thus disrupting fetal lung growth and leading to pulmonary hypoplasia. The exact mechanism by which oligohydramnios alters the respiratory system structure and the effect of oligohydramnios on long-term respiratory outcomes remain unknown. In this review, we summarize the effects of oligohydramnios on lung development, discuss the mechanisms of oligohydramnios-induced pulmonary hypoplasia identified in various animal studies, and describe the long-term respiratory outcomes in childhood of oligohydramnios-exposed fetuses reported by a population-based study.

Experimental oligohydramnios decreases collagen in hypoplastic fetal rat lungs

Neonates with premature rupture of the membrane and oligohydramnios have an increased risk of acute respiratory morbidity. The aims of this study are to investigate the effects of experimental oligohydramnios on transforming growth factor (TGF)-β1 and connective tissue growth factor (CTGF) expressions and collagen level in fetal rat lungs. On day 16 of gestation, we anesthetized timed pregnant Sprague-Dawley dams, punctured the uterine wall and fetal membranes of each amniotic sac which resulted in oligohydramnios. Fetuses in the opposite uterine horn served as controls. On days 19 and 21 of gestation, fetuses were delivered by cesarean section. Rats exposed to oligohydramnios exhibited significantly lower lung weight/body weight ratios on days 19 and 21 of gestation than did the control rats. Lung type I collagen and TGF-β1 mRNA expressions and lung collagen levels were significantly decreased in rats exposed to oligohydramnios on days 19 and 21 of gestation. Type I collagen and inhibitors of metalloproteinase-1 (TIMP-1) proteins were decreased and matrix metalloproteinase-1 (MMP-1) was increased in oligohydramnios-exposed rats on days 19 and 21 of gestation. CTGF mRNA expressions were comparable between control and oligohydramnios-exposed rats on days 19 and 21 of gestation. These data suggest that downregulation of collagen might be involved in the pathogenesis of oligohydramnios-induced respiratory morbidity.

Uteroplacental Insufficiency Alters the Retinoid Pathway and Lung Development in Newborn Rats

BACKGROUNDnIntrauterine growth retardation (IUGR) is associated with reduced lung function during infancy and perhaps throughout adulthood. The retinoic acid (RA) signaling pathway modulates pre- and postnatal lung development. This study was conducted to test our hypothesis that uteroplacental insufficiency alters the elements of the retinoid pathway in developing lungs.nnnMETHODSnOn Gestation Day 18, either uteroplacental insufficiency was induced through bilateral uterine vessel ligation (IUGR group) or sham surgery (control group) was performed. Lung tissues from the offspring were examined through Western blotting, immunohistochemistry, and morphometry on Postnatal Day 3 and Postnatal Day 7.nnnRESULTSnCompared with control rats, the IUGR rats exhibited significantly lower body weights on Postnatal Day 3 and Postnatal Day 7 and significantly lower lung weights on Postnatal Day 3. Uteroplacental insufficiency significantly increased RA receptor (RAR)-β protein expression on Postnatal Day 3. The expression of RAR-α, RAR-γ, cellular RA-binding protein-1, and cellular RA-binding protein-2 between the control and IUGR rats was comparable on Postnatal Day 3 and Postnatal Day 7. Compared with the control rats, the IUGR rats exhibited a significantly higher volume fraction of alveolar airspace on Postnatal Day 3 and Postnatal Day 7 and a significantly lower volume fraction of alveolar walls on Postnatal Day 3.nnnCONCLUSIONnUteroplacental insufficiency causes defective alveolarization and transient increases in RAR-β expression in the lungs of newborn rats. The retinoid pathway may be one of the probable pathways mediating lung abnormalities caused by uteroplacental insufficiency.

Effects of maternal retinoic acid administration on lung angiogenesis in oligohydramnios-exposed fetal rats.

BACKGROUNDnAll-trans retinoic acid (ATRA) induces in vitro angiogenesis and vascular endothelial growth factor (VEGF) secretion. Prenatal administration of vitamin A tends to increase the pulmonary and plasma levels of VEGF in the developing mouse. The aims of this study were to examine the effects of maternal retinoic acid treatment on lung VEGF expression and angiogenesis in oligohydramnios-exposed fetal rats.nnnMETHODSnOn day 16 of gestation, pregnant Sprague-Dawley rats were randomly assigned to either the retinoic acid group (intragastric ATRA at 10 mg/kg body weight) or the vehicle group. We punctured each uterine sac to produce oligohydramnios, and fetuses in the opposite uterine horn served as controls. On day 21 of gestation, the fetuses were delivered by cesarean section.nnnRESULTSnRats exposed to oligohydramnios exhibited lower lung weights and lung/body weight ratios, and ATRA exhibited no effects on the body or lung weights of oligohydramnios-exposed rats. Lung microvessel density decreased in oligohydramnios-exposed rats of maternal vehicle-treated dams. Microvessel density was comparable between the oligohydramnios + retinoic acid group and the control + retinoic acid group. VEGF expression was comparable among control and oligohydramnios-exposed rats of maternal vehicle- or retinoic acid-treated dams.nnnCONCLUSIONnMaternal retinoic acid treatment did not increase lung VEGF expression or enhance lung development in oligohydramnios-exposed fetal rats. These results do not support the use of maternal retinoic acid to prevent oligohydramnios-induced pulmonary hypoplasia in the pseudoglandular stage.

Mechanism of Oligohydramnios-induced Pulmonary Hypoplasia

Abstract Pulmonary hypoplasia is common in the perinatal period and is a significant cause of death in newborn infants, and oligohydramnios is one of the most commonly associated abnormalities. Neonates exposed to oligohydramnios caused by premature rupture of membranes have an increased risk of acute respiratory morbidity. The exact mechanism by which oligohydramnios alters the respiratory system remains unknown. We herein report the effects of experimental oligohydramnios on lung growth and the expressions of growth factors and extracellular matrix in fetal rats on days 19 and 21 of gestation by producing oligohydramnios from days 16 to 21 of gestation in Sprague-Dawley dams. Rats exposed to oligohydramnios exhibited lung hypoplasia and significantly decreased expressions of extracellular matrix, transforming growth factor-β1 and platelet-derived growth factor on days 19 and 21 of gestation. Concomitant maternal retinoic acid treatment at a dose of 10 mg/kg increased platelet-derived growth factor expression but did not enhance fetal lung development. These results suggest that there is a stage-specific requirement for retinoic acid during lung development, and retinoic acid treatment should be applied with caution.