Metabolomics study of kidney tissue in a mouse model of oxygen-induced retinopathy

Objective

To explore the effects of hyperoxic environments on renal metabolites to understand the potential mechanisms that contribute to pathologic retinal vascular neovascularization and renal injury through metabolomic studies in a mouse model of oxygen-induced retinopathy (OIR) model.

Methods

Sixteen C57/B6J mice pups born to day 7 (P7) were randomly and equally divided into an OIR model group and a normal control group using a randomized numerical table of mother mice.Mice were reared standardly from birth until day 7 (P7), then mice and their mother mice in the OIR group were placed in a hyperoxic (75±2)% chamber until day 12 (P12) and then reared normally.Mice in the normal control group were reared normally throughout.Mice in two groups were killed by carbon dioxide euthanasia on postnatal day 17 (P17). The mice retinal wholemount from the two groups were made and stained with isolectin B4 (IB4) to observe the morphology of retinal vessels, central non-perfusion area and pathological neovascularization.The kidney tissue of P17 mice was analyzed by liquid chromatograph mass spectrometer.After anticoagulant treatment, the whole blood of mice was centrifuged and precipitated, and the obtained plasma without cellular components was analyzed by targeted metabonomics.Mass spectral information was interpreted using metabolomics data processing software Progenesis QI v2.3.Overall differences in metabolic profiles were distinguished by unsupervised principal component analysis and orthogonal partial least squares analysis (OPLS-DA). The fold change and P values of metabolites were compared between the two groups.The variable importance of projection value>1 and P value<0.05 was used to screen out differential metabolites.Metabolic pathway enrichment analysis of differential metabolites was performed based on the KEGG database.The feeding and use of animals were strictly in accordance with the requirements of the Ethics Committee of Jinan University, and the research protocol was reviewed and approved by the Ethics Committee of Jinan University (No.20200401-54).

Results

The IB4 staining of retinal wholemounts showed that the retinal blood vessels were evenly distributed in the P17 mice from control group.The peripheral retinal vessels were tortuous and disordered with a large non-perfusion area in central region in P17 mice from OIR group, and a large number of neovascularization clusters were formed at the junction of the nonperfusion area and the vascular area of the retina, showing strong fluorescent staining.The relative area of retinal nonperfusion area in OIR group was (25.16±3.50)%, which was significantly larger than (0.63±0.30)% in normal control group (t=12.07, P<0.001). The OPLS-DA parameter R2X cum (0.578), interpretation rate R2Y cum (0.978) and prediction rate Q2 cum (0.857) values were all greater than 0.5, indicating that the OPLS-DA model had a good predictive ability.A total of 26 main differential metabolites were found, among which 17 were up-regulated and 9 were down-regulated, including glycerophospholipids (PC 20∶4(5Z, 8Z, 11Z, 14Z)/0∶0, PC 22∶6(4Z, 7Z, 10Z, 13Z, 16Z, 19Z)/0∶0, PC 14∶1(9Z)/20∶2(11Z, 14Z), PE P-18∶0/20∶4(6E, 8Z, 11Z, 14Z)(5OH[S]), amino acid metabolites (arginine, ornithine, pipecolic acid, and hydroxylysine), purines (guanine, hypoxanthine, hydroxypurinol), and fatty acids (methyl 15-palmitate, 2, 6, 8, 12-tetramethyl-2, 4-tridecadien-1-ol), and so on.Differential metabolites were mainly enriched in ABC transporters (L-arginine, taurine, inositol, adenosine, N-acetyl-D-glucosamine, L-glutamine), aminoacyl-tRNA biosynthesis (L-isoleucine, L-proline, L-arginine, L-histidine, L-glutamine), arginine biosynthesis (L-arginine, L-ornithine, L-glutamine) metabolic pathways.The plasma targeted metabonomics showed that the differential amino acid metabolites were mainly enriched in metabolic pathways such as aminoacyl-tRNA biosynthesis, arginine biosynthesis and metabolism, and ABC transporters.

Conclusions

ABC transporter, aminoacyl-tRNA biosynthesis, and arginine biosynthesis metabolic pathways in OIR mice may participate in the pathological changes of renal injury and neovascularization in retinopathy of prematurity.

Oxygen-induced retinopathy; Mice; Kidney; Liquid chromatograph mass spectrometer; Metabolite analysis; Retinopathy of prematurity