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

Effect and factors associated with reactivation after intravitreal conbercept or aflibercept in retinopathy of prematurity

BACKGROUND

To evaluate the effect and factors associated with the reactivation of retinopathy of prematurity (ROP) after intravitreal conbercept or aflibercept.

METHODS

We retrospectively reviewed the medical records of 176 eyes diagnosed with ROP and treated with anti-VEGF therapy between January 2018 and September 2022. The rate of reactivation and complications were assessed during the follow-up period. The factors of reactivation of ROP after intravitreal conbercept or aflibercept were analyzed on the basis of clinical factors and retinal parameters.

RESULTS

Reactivation of ROP occurred in 10 eyes (13.9%) after intravitreal conbercept and 13 eyes (12.5%) after intravitreal aflibercept (P = 0.79). The interval between injection and reactivation was significantly longer in the aflibercept group than in the conbercept group (15.50 ± 4.05 vs. 5.36 ± 0.50 weeks) (P < 0.001). The central retinal arteriolar equivalent (CRAE) of aggressive ROP was larger than that of type 1 prethreshold and threshold ROP before anti-VEGF therapy (P < 0.05). Zone I and stage 3 exhibited a positive correlation with the reactivation of retinopathy of prematurity (ROP) [odds ratio (OR) = 20.15, 5.02]. The changes in CRAE of pre-and post-therapy and gestational age were identified as potential protective factors for these outcomes (OR = 0.23, 0.49).

CONCLUSIONS

Conbercept and aflibercept are effective for treating ROP. Aflibercept resulted in longer treatment intervals compared to conbercept. Zone, stage, and gestational age were associated with the reactivation of ROP. CRAE was associated with not only the severity of ROP but also its reactivation. Additionally, it may be an objective indicator in the early indication and follow-up of ROP.

Identification and clinical significance of tsRNAs and miRNAs in PBMCs of treatment-requiring retinopathy of prematurity

The aim of the study is to reveal the expression profiling and clinical significance of peripheral blood mononuclear cell (PBMC) tRNA-derived small RNAs (tsRNAs) and microRNAs (miRNAs) of premature infants with treatment-requiring retinopathy of prematurity (ROP). Significantly altered tsRNAs and miRNAs were screened using small RNA sequencing. RT-qPCR was used to verify the altered RNAs identified by small RNA transcriptomics. The target genes, their enriched functions, and possibly involved signaling pathways were identified by bioinformatics analyses. According to the small RNA sequencing, 125 tsRNAs and 205 miRNAs were significantly altered in PBMCs obtained from infants with treatment-requiring ROP compared with the premature controls without retinopathy. We preliminarily validated the significant alterations of 6 tsRNAs and 9 miRNAs. The target genes for those tsRNAs were enriched for cellular macromolecule metabolic process, intracellular anatomical structure, transcription regulatory region nucleic acid binding, and Th17 cell differentiation; those of the altered miRNAs were enriched for the developmental process, cell junction, DNA-binding transcription activator activity, and FoxO signaling pathway. By verification with the extended sample size, we identified tsRNAs and miRNAs that could be potential biomarkers with clinical values. The study recognized the alterations and clinical significance of changed tsRNA/miRNA profiles in PBMCs from premature infants with ROP. These significantly altered tsRNAs and miRNAs might be useful as potential diagnostic biomarkers and molecular targets for treatment-requiring ROP.

Oxygen-induced pathological angiogenesis promotes intense lipid synthesis and remodeling in the retina

The retina is a notable tissue with high metabolic needs which relies on specialized vascular networks to protect the neural retina while maintaining constant supplies of oxygen, nutrients, and dietary essential fatty acids. Here we analyzed the lipidome of the mouse retina under healthy and pathological angiogenesis using the oxygen-induced retinopathy model. By matching lipid profiles to changes in mRNA transcriptome, we identified a lipid signature showing that pathological angiogenesis leads to intense lipid remodeling favoring pathways for neutral lipid synthesis, cholesterol import/export, and lipid droplet formation. Noteworthy, it also shows profound changes in pathways for long-chain fatty acid production, vital for retina homeostasis. The net result is accumulation of large quantities of mead acid, a marker of essential fatty acid deficiency, and a potential marker for retinopathy severity. Thus, our lipid signature might contribute to better understand diseases of the retina that lead to vision impairment or blindness.

Aflibercept Suppression of angiopoietin-2 in a Rabbit Retinal Vascular Hyperpermeability Model

Purpose

Anti-vascular endothelial growth factor (anti-VEGF) therapies, which attenuate the capacity of VEGF to bind to VEGF receptors, are standard-of-care options for various retinal disorders that are characterized by pathologic retinal angiogenesis and vascular permeability. Multiple receptors and ligands have also been reported as being involved in these pathways, including angiopoietin-1 (ANG1) and angiopoietin-2 (ANG2).

Methods

Electrochemiluminescence immunoassays were used to detect human VEGF (hVEGF), as well as rabbit ANG2 and basic fibroblast growth factor protein levels in vitreous samples derived from a study evaluating the efficacy of the anti-VEGF agents ranibizumab, aflibercept, and brolucizumab in an hVEGF165-induced rabbit retinal vascular hyperpermeability model.

Results

hVEGF was completely suppressed in rabbit vitreous after anti-VEGF treatment for 28 days. ANG2 protein in vitreous and ANGPT2 mRNA in retina tissue were similarly suppressed, although the anti-VEGF agents do not directly bind to ANG2. Aflibercept demonstrated the greatest inhibitory effect in ANG2 levels in vitreous, which correlated with strong, durable suppression of intraocular hVEGF levels.

Conclusions

This study explored the effects of anti-VEGF therapies beyond direct binding of VEGF by evaluating protein levels and the expression of target genes involved in angiogenesis and associated molecular mechanisms in the rabbit retina and choroid.

Translational Relevance

In vivo data suggest that anti-VEGF agents currently used for the treatment of retinal diseases could provide beneficial effects beyond direct binding of VEGF, including suppression of ANG2 protein and ANGPT2 mRNA.

Transcriptome analysis of AAV-induced retinopathy models expressing human VEGF, TNF-α, and IL-6 in murine eyes

Retinopathies are multifactorial diseases with complex pathologies that eventually lead to vision loss. Animal models facilitate the understanding of the pathophysiology and identification of novel treatment options. However, each animal model reflects only specific disease aspects and understanding of the specific molecular changes in most disease models is limited. Here, we conducted transcriptome analysis of murine ocular tissue transduced with recombinant Adeno-associated viruses (AAVs) expressing either human VEGF-A, TNF-α, or IL-6. VEGF expression led to a distinct regulation of extracellular matrix (ECM)-associated genes. In contrast, both TNF-α and IL-6 led to more comparable gene expression changes in interleukin signaling, and the complement cascade, with TNF-α-induced changes being more pronounced. Furthermore, integration of single cell RNA-Sequencing data suggested an increase of endothelial cell-specific marker genes by VEGF, while TNF-α expression increased the expression T-cell markers. Both TNF-α and IL-6 expression led to an increase in macrophage markers. Finally, transcriptomic changes in AAV-VEGF treated mice largely overlapped with gene expression changes observed in the oxygen-induced retinopathy model, especially regarding ECM components and endothelial cell-specific gene expression. Altogether, our study represents a valuable investigation of gene expression changes induced by VEGF, TNF-α, and IL-6 and will aid researchers in selecting appropriate animal models for retinopathies based on their agreement with the human pathophysiology.

RNA-Seq Provides Insights into VEGF-Induced Signaling in Human Retinal Microvascular Endothelial Cells: Implications in Retinopathy of Prematurity

The pathophysiology of retinopathy of prematurity (ROP) is postulated to first involve delayed intraretinal vascularization, followed by intravitreal neovascularization (IVNV). Although intravitreal agents that reduce the bioactivity of vascular endothelial growth factor (VEGF) are used to treat IVNV, concerns exist regarding their effects on intraretinal vascularization. In an experimental ROP model, VEGF receptor 2 (VEGFR2) knockdown in retinal endothelial cells reduced IVNV and promoted intraretinal vascularization, whereas knockdown of a downstream effector, signal transducer and activator of transcription 3 (STAT3) in retinal endothelial cells only reduced IVNV. In this study, we tested the hypothesis that the different pathways involved in VEGF-triggered VEGFR2 signaling and VEGF-triggered STAT3 signaling in retinal endothelial cells would allow us to delineate signaling pathways involved in IVNV from those involved in intraretinal vascularization in ROP. To address our hypothesis, we used RNA-sequencing and pathway enrichment analysis to determine changes in the transcriptome of cultured human retinal microvascular endothelial cells (HRMECs). Of the enriched pathways, inactivation of oncostatin M signaling was predicted by either KDR or STAT3 knockdown in the presence of VEGF. Activation of kinetochore metaphase signaling was predicted by KDR knockdown, whereas inactivation was predicted by STAT3 knockdown in the presence of VEGF. Inactivation of signaling by the Rho family of GTPases was predicted by KDR knockdown, but activation was predicted by STAT3 knockdown in the presence of VEGF. Taken together, our data identified unique signaling pathway differences between VEGF-triggered VEGFR2 and VEGF-triggered STAT3 in HRMECs that might have implications in ROP.

APJ/apelin: a promising target for the treatment of retinopathy of prematurity

Retinopathy of prematurity is a noticeable retinal abnormality causing common blindness in children. An uncontrolled retinal vasculature in retinopathy of prematurity inflicts vision loss in numerous children despite the accessibility to a wide range of clinical treatments prescribed for retinopathy of prematurity. Apelin/APJ [class A (rhodopsin-like) G-protein-coupled receptor] signaling regulates retinopathy of prematurity augmented with uncontrolled angiogenesis. Antagonists targeting pathological apelin/APJ-signaling-induced angiogenesis could be effective in attenuating retinopathy of prematurity. The therapeutic proficiency of antagonists in diverse modalities: peptides, bioactive molecules and antibodies, targeting apelin peptides or the APJ receptor is discussed in this review. We hypothesize the antagonists could effectively attenuate the retinal vasculature triggered by apelin/APJ signaling activation governing vision impairment in young children.

Gene expression profile of the murine ischemic retina and its response to Aflibercept (VEGF-Trap)

Ischemic retinal dystrophies are leading causes of acquired vision loss. Although the dysregulated expression of the hypoxia-responsive VEGF-A is a major driver of ischemic retinopathies, implication of additional VEGF-family members in their pathogenesis has led to the development of multivalent anti-angiogenic tools. Designed as a decoy receptor for all ligands of VEGFR1 and VEGFR2, Aflibercept is a potent anti-angiogenic agent. Notwithstanding, the molecular mechanisms mediating Aflibercept's efficacy remain only partially understood. Here, we used the oxygen-induced retinopathy (OIR) mouse as a model system of pathological retinal vascularization to investigate the transcriptional response of the murine retina to hypoxia and of the OIR retina to Aflibercept. While OIR severely impaired transcriptional changes normally ensuing during retinal development, analysis of gene expression patterns hinted at alterations in leukocyte recruitment during the recovery phase of the OIR protocol. Moreover, the levels of Angiopoietin-2, a major player in the progression of diabetic retinopathy, were elevated in OIR tissues and consistently downregulated by Aflibercept. Notably, GO term, KEGG pathway enrichment, and expression dynamics analyses revealed that, beyond regulating angiogenic processes, Aflibercept also modulated inflammation and supported synaptic transmission. Altogether, our findings delineate novel mechanisms potentially underlying Aflibercept's efficacy against ischemic retinopathies.

In-depth transcriptomic analysis of human retina reveals molecular mechanisms underlying diabetic retinopathy

Diabetic Retinopathy (DR) is among the major global causes for vision loss. With the rise in diabetes prevalence, an increase in DR incidence is expected. Current understanding of both the molecular etiology and pathways involved in the initiation and progression of DR is limited. Via RNA-Sequencing, we analyzed mRNA and miRNA expression profiles of 80 human post-mortem retinal samples from 43 patients diagnosed with various stages of DR. We found differentially expressed transcripts to be predominantly associated with late stage DR and pathways such as hippo and gap junction signaling. A multivariate regression model identified transcripts with progressive changes throughout disease stages, which in turn displayed significant overlap with sphingolipid and cGMP-PKG signaling. Combined analysis of miRNA and mRNA expression further uncovered disease-relevant miRNA/mRNA associations as potential mechanisms of post-transcriptional regulation. Finally, integrating human retinal single cell RNA-Sequencing data revealed a continuous loss of retinal ganglion cells, and Müller cell mediated changes in histidine and β-alanine signaling. While previously considered primarily a vascular disease, attention in DR has shifted to additional mechanisms and cell-types. Our findings offer an unprecedented and unbiased insight into molecular pathways and cell-specific changes in the development of DR, and provide potential avenues for future therapeutic intervention.

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.