Transcriptome analysis reveals dysregulation of genes involved in oxidative phosphorylation in a murine model of retinopathy of prematurity.

BACKGROUND: Retinal gene expression pattern is severely altered after exposition to hyperoxia in mice with oxygen-induced retinopathy (OIR), a common model of retinopathy of prematurity. Gene ontology and signaling pathway analyses may add new insights into a better understanding of the pathogenesis of this disease. METHODS: Seven-day-old C57BL/6J mice (n = 60) were exposed to 75% oxygen for 5 days and then recovered in room air. The controls (n = 60) were kept in the normoxic conditions. Retinas were harvested immediately following hyperoxia, during the phase of maximal neovascularization, and at the time of neovascularization regression. The retinal RNA samples were evaluated for gene expression using mouse gene expression microarrays. DAVID annotation tools were used for gene ontology and pathway analyses. RESULTS: The most significantly enriched signaling pathways during the neovascularization phase of OIR were: focal adhesion; ECM-receptor interaction; PI3K-Akt; oxidative phosphorylation; and Alzheimer's, Parkinson's and Huntington's disease signaling pathways. Genes involved in apoptosis, cell proliferation, cell differentiation, and immune responses were associated with neovascularization regression. CONCLUSIONS: Performed analyses revealed the possible involvement of various signaling pathways in OIR pathomechanism, mostly specific to the OIR phase. Dysregulation of genes involved in oxidative phosphorylation may have an impact on neovascularization development.

Pulmonary vascular disease is evident in gene regulation of experimental bronchopulmonary dysplasia.

Objective: To examine the gene expression regarding pulmonary vascular disease in experimental bronchopulmonary dysplasia in young mice. Premature delivery puts babies at risk of severe complications. Bronchopulmonary dysplasia (BPD) is a common complication of premature birth leading to lifelong affection of pulmonary function. BPD is recognized as a disease of arrested alveolar development. The disease process is not fully described and no complete cure or prevention is known. The focus of interest in the search for treatment and prevention of BPD has traditionally been at airspace level; however, the pulmonary vasculature is increasingly acknowledged in the pathology of BPD. The aim of the investigation was to study the gene expression in lungs with BPD with regards to pulmonary vascular disease (PVD).Methods: We employed a murine model of hyperoxia-induced BPD and gene expression microarray technique to determine the mRNA expression in lung tissue from young mice. We combined gene expression pathway analysis and analyzed the biological function of multiple single gene transcripts from lung homogenate to study the PVD relevant gene expression.Results: There were n = 117 significantly differentially regulated genes related to PVD through down-regulation of contractile elements, up- and down-regulation of factors involved in vascular tone and tissue-specific genes. Several genes also allowed for pinpointing gene expression differences to the pulmonary vasculature. The gene Nppa coding for a natriuretic peptide, a potent vasodilator, was significantly down-regulated and there was a significant up-regulation of Pde1a (phosphodiesterase 1A), Ptger3 (prostaglandin e receptor 3), and Ptgs1 (prostaglandin-endoperoxide synthase one).Conclusion: The pulmonary vasculature is affected by the arrest of secondary alveolarization as seen by differentially regulated genes involved in vascular tone and pulmonary vasculature suggesting BPD is not purely an airspace disease. Clues to prevention and treatment may lie in the pulmonary vascular system.

Short- and long-term impact of hyperoxia on the blood and retinal cells' transcriptome in a mouse model of oxygen-induced retinopathy.

BACKGROUND: We aimed to identify global blood and retinal gene expression patterns in murine oxygen-induced retinopathy (OIR), a common model of retinopathy of prematurity, which may allow better understanding of the pathogenesis of this severe ocular prematurity complication and identification of potential blood biomarkers. METHODS: A total of 120 C57BL/6J mice were randomly divided into an OIR group, in which 7-day-old pups were maintained in 75% oxygen for 5 days, or a control group. RNA was extracted from the whole-blood mononuclear cells and retinal cells on days 12, 17, and 28. Gene expression in the RNA samples was evaluated with mouse gene expression microarrays. RESULTS: There were 38, 1370 and 111 genes, the expression of which differed between the OIR and control retinas on days 12, 17, and 28, respectively. Gene expression in the blood mononuclear cells was significantly altered only on day 17. Deptor and Nol4 genes showed reduced expression both in the blood and retinal cells on day 17. CONCLUSION: There are sustained marked changes in the global pattern of gene expression in the OIR mice retinas. An altered expression of Deptor and Nol4 genes in the blood mononuclear cells requires further investigation as they may indicate retinal neovascularization.

Immune System Regulation Affected by a Murine Experimental Model of Bronchopulmonary Dysplasia: Genomic and Epigenetic Findings.

BACKGROUND: Bronchopulmonary dysplasia (BPD) is a common cause of abrupted lung development after preterm birth. BPD may lead to increased rehospitalization, more severe and frequent respiratory infections, and life-long reduced lung function. The gene regulation in lungs with BPD is complex, with various genetic and epigenetic factors involved. OBJECTIVES: The aim of this study was to examine the regulatory relation between gene expression and the epigenome (DNA methylation) relevant for the immune system after hyperoxia followed by a recovery period in air using a mouse model of BPD. METHODS: Newborn mice pups were subjected to an immediate hyperoxic condition from birth and kept at 85% O2 levels for 14 days followed by a 14-day period in room air. Next, mice lung tissue was used for RNA and DNA extraction with subsequent microarray-based assessment of lung transcriptome and supplementary methylome analysis. RESULTS: The immune system-related transcriptomeregulation was affected in mouse lungs after hyperoxia. A high proportion of genes relevant in the immune system exhibited significant expression alterations, e.g., B cell-specific genes central to the cytokine-cytokine receptor interaction, the PI3K-AKT, and the B cell receptor signaling pathways. The findings were accompanied by significant DNA hypermethylation observed in the PI3K-AKT pathway and immune system-relevant genes. CONCLUSIONS: Oxygen damage could be partly responsible for the increased susceptibility and abnormal response to respiratory viruses and infections seen in premature babies with BPD through dysregulated genes.

Neonatal Ogg1/Mutyh knockout mice have altered inflammatory gene response compared to wildtype mice in the brain and lung after hypoxia-reoxygenation.

Background 8-Oxoguanine DNA-glycosylase 1 (OGG1) and mutY DNA glycosylase (MUTYH) are crucial in the repair of the oxidative DNA lesion 7,8-dihydro-8-oxoguanine caused by hypoxia-reoxygenation injury. Our objective was to compare the gene expression changes after hypoxia-reoxygenation in neonatal Ogg1-Mutyh double knockout mice (OM) and wildtype mice (WT), and study the gene response in OM after hyperoxic reoxygenation compared to normoxic. Methods Postnatal day 7 mice were subjected to 2 h of hypoxia (8% O2) followed by reoxygenation in either 60% O2 or air, and sacrificed right after completed reoxygenation (T0h) or after 72 h (T72h). The gene expression of 44 a priori selected genes was examined in the hippocampus/striatum and lung. Results We found that OM had an altered gene response compared to WT in 21 genes in the brain and 24 genes in the lung. OM had a lower expression than WT of inflammatory genes in the brain at T0h, and higher expression at T72h in both the brain and lung. In the lung of OM, five genes were differentially expressed after hyperoxic reoxygenation compared to normoxic. Conclusion For the first time, we report that Ogg1 and Mutyh in combination protect against late inflammatory gene activation in the hippocampus/striatum and lung after neonatal hypoxia-reoxygenation.

Temporal Patterns of Gene Expression Profiles in the Neonatal Mouse Lung after Hypoxia-Reoxygenation.

BACKGROUND: One out of four children with neonatal asphyxia has lung involvement. Still, there has been little research on injury mechanisms of hypoxia-reoxygenation in the neonatal lung. OBJECTIVES: To make a temporal profile of the gene expression changes of 44 a priori selected genes after hypoxia-reoxygenation in the newborn mouse lung, and to compare the changes after hyperoxic and normoxic reoxygenation. METHODS: Postnatal day 7 mice were randomized to 2-hour hypoxia (8% O2) and 30-min reoxygenation in either 60% O2 or air. After 0-72 h of observation, gene expression changes and protein concentrations in whole lung homogenates were examined. RESULTS: Immediately after completed reoxygenation, 7 genes of mediators of inflammation were downregulated, and there was an antiapoptotic gene expression pattern. Three DNA glycosylases were downregulated, while genes involved in cell cycle renewal indicated both increased and decreased cell cycle arrest. Sod1 (T2.5h median H60: 1.01, H21: 0.88, p = 0.005; T5h median H60: 1.04, H21: 0.85, p = 0.038) and Il1b (T0h median H60: 0.86, H21: 1.08, p = 0.021) were significantly differentially expressed when comparing hyperoxic and normoxic reoxygenation. CONCLUSION: In this newborn mouse lung hypoxia-reoxygenation model, we found downregulation of genes of mediators of inflammation, an antiapoptotic gene expression pattern, and downregulation of DNA glycosylases. Sod1 and Il1b were significantly differentially expressed when comparing reoxygenation using 60% O2 with air.

Increased expression of inflammatory genes in the neonatal mouse brain after hyperoxic reoxygenation.

BACKGROUND: Hyperoxic reoxygenation following hypoxia increases the expression of inflammatory genes in the neonatal mouse brain. We have therefore compared the temporal profile of 44 a priori selected genes after hypoxia and hyperoxic or normoxic reoxygenation. METHODS: Postnatal day 7 mice were subjected to 2 h of hypoxia (8% O2) and 30 min reoxygenation with 60% or 21% O2. After 0 to 72 h observation, mRNA and protein were examined in the hippocampus and striatum. RESULTS: There were significantly higher gene expression changes in six genes after hyperoxic compared to normoxic reoxygenation. Three genes had a generally higher expression throughout the observation period: the inflammatory genes Hmox1 (mean difference: 0.52, 95% confidence interval (CI): 0.15-1.01) and Tgfb1 (mean difference: 0.099, CI: 0.003-0.194), and the transcription factor Nfkb1 (mean difference: 0.049, CI: 0.011-0.087). The inflammatory genes Cxcl10 and Il1b, and the DNA repair gene Neil3, had a higher gene expression change after hyperoxic reoxygenation at one time point only. Nineteen genes involved in inflammation, transcription regulation, apoptosis, angiogenesis, and glucose transport had significantly different gene expression changes with time in all intervention animals. CONCLUSION: We confirm that hyperoxic reoxygenation induces a stronger inflammatory gene response than reoxygenation with air.