Aquaporin 11 alleviates retinal Müller intracellular edema through water efflux in diabetic retinopathy

SUMOylation is a Translatable Target in Hypoxic MNPs Regulating Retinal Vasculopathy

Retinal vasculopathies pose a devastating threat to human health. While anti-VEGF therapy situates the first-line treatment for patients, the clinical efficacy is limited by suboptimal response and potential risks raised by long-term high-dosage use. Neurovascular unit uncoupling is recognized as a key mechanism contributing to pathological neovascularization, yet how immune components get involved is less appreciated. Here, it is reported that SUMOylation modulates the pro-angiogenic capacity of macrophage, and inhibition of the SUMO-conjugating enzyme UBC9 synergizes with anti-VEGF therapy in preclinical models. Diabetic human retinal mononuclear phagocytes (MNPs) overexpress UBC9. Genetic ablation of UBC9 in MNPs compromises the crosstalk with endothelial cells by reducing Vegfa splicing isoforms, including Vegf120, Vegf144, Vegf164, and Vegf188. Mechanistically, hypoxia facilitates the SUMOylation of fused in sarcoma (FUS) protein at lysine residues K327 and K502. Mutation of the SUMOylation sites enhances FUS binding to the Vegfa 3'-untranslated region (3'UTR), leading to mRNA destabilization and decreased VEGFA production. Intravitreal administration of anti-VEGF elevates UBC9 whereas Ubc9 siRNA-liposomes alleviates retinal vascular leakage and choroidal neovascularization, and a better therapeutic efficacy is yielded when combining with anti-VEGF therapy. Taken together, this study highlights a novel approach for treating retinal vascular diseases by modulating the MNPs-endothelial cell interplay.

AQP4- and Kir4.1-Mediated Müller Cell Oedema Is Involved in Retinal Injury Induced By Hypobaric Hypoxia

Hypobaric hypoxia is the main cause of high-altitude retinopathy (HAR). Retinal oedema is the key pathological change in HAR. However, its pathological mechanism is not clear. In this study, a 5000-m hypobaric hypoxic environment was simulated. Haematoxylin and eosin (H&E) staining and electrophysiological (ERG) detection were used to observe the morphological and functional changes in the retina of mice under hypobaric hypoxia for 2-72 h. Toluidine blue staining and transmission electron microscopy were used to observe the morphology of Müller cells in the hypobaric hypoxia groups. The functional changes and oedema mechanism of Müller cells were detected by immunofluorescence and western blotting. The expression levels of glutamine synthetase (GS), glial fibrillary acidic protein (GFAP), aquaporin 4 (AQP4), and inwardly rectifying potassium channel subtype 4.1 (Kir4.1) in Müller cells were quantitatively analysed. This study revealed that retinal oedema gradually increased with prolonged exposure to a 5000-m hypobaric hypoxic environment. In addition, the ERG showed that the time delay and amplitude of the a-wave and b-wave decreased. The expression of GS decreased, and the expression of GFAP increased in Müller cells after exposure to hypobaric hypoxia for 4 h. At the same time, retinal AQP4 expression increased, and Kir4.1 expression decreased. The oedema and functional changes in Müller cells are consistent with the time point of retinal oedema. In conclusion, Müller cell oedema is involved in retinal oedema induced by hypobaric hypoxia. An increase in AQP4 and a decrease in Kir4.1 are the main causes of Müller cell oedema caused by hypobaric hypoxia.

TRPML1 acts as a predisposing factor in lymphedema development by regulating the subcellular localization of aquaporin-3, -5

An imbalance in lymphatic fluid, whether it is caused by generation, transport, outflow, or dysfunctional vessels, can lead to lymphedema; however, the exact pathogenesis of this disease remains unclear. To explore the mechanism, we focused on the association among TRPML1, aquaporin-3 (AQP3), and aquaporin-5 (AQP5) in human lymphatic endothelial cells (HLECs). We explored the role of TRPML1 in altering the permeability of HLECs in lymphedema. Meanwhile, we constructed a disease model using gene-knockout mice to observe the effect of TRPML1 on inflammation and fibrosis in lymphedema sites. Our results indicate that TRPML1 not only regulates the localization of AQP3, -5 to the cell membrane but also increases HLEC permeability, disrupts lymphatic fluid transport, and mediates the development of chronic inflammation at the site of lymphedema. Our study suggests that TRPML1 is a precipitating factor in lymphedema. Our findings improve the understanding of TRPML1 and aquaporins in secondary lymphedema, providing valuable insights for future research.

New insights on the role of microRNAs in retinal Müller glial cell function

MicroRNAs belong to the family of non-coding RNAs that participate in cell proliferation, cell death and development. The Müller glial cells are the inherent and specific neuroglia cells in the retinal organisation and play significant roles in retinal neuroprotection, organisational maintenance, inflammation and immunity, regeneration, and the occurrence and development of retinal diseases. However, only a few studies report the underlying mechanism of how miRNAs drive the function of Müller glial cells in the development of retinal diseases. This review aims to summarise the roles of miRNAs in retinal Müller glial cell function, including gliogenesis, inflammation and immunity, regeneration, the development of retinal diseases, and retinal development. This review may point out a novel miRNA-based insight into retinal repair and regeneration. MiRNAs in Müller glial cells may be considered a diagnostic and therapeutic target in the process of retinal repair and regeneration.

The role of retinal glial cells and related factors in macular edema

Macular edema (ME) has emerged as a leading cause of visual impairment, representing a critical clinical manifestation and complication associated with many eye diseases. In the occurrence and development of ME, retinal glial cells like Müller cells and microglial cells play vital roles. Moreover, growth factor and cytokines associated with them, such as vascular endothelial growth factor (VEGF), pigment epithelium-derived factor (PEDF), hypoxia-inducible factor-1α (HIF-1α), angiopoietin-like protein 4 (ANGPTL4), interleukin-6(IL-6), interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), prostaglandin, etc., also take part in the pathogenesis of ME. Changes in these cytokines can lead to retinal angiogenesis, increased vascular permeability, blood-retinal barrier (BRB) breakdown, and fluid leakage, further causing ME to occur or deteriorate. Research on the role of retinal glial cells and related cytokines in ME will provide new therapeutic directions and effective remedies. This article is a literature review on the role of Müller cells, microglial cells and related factors in ME pathogenesis.

Anti-VEGF combined with ocular corticosteroids therapy versus anti-VEGF monotherapy for diabetic macular edema focusing on drugs injection times and confounding factors of pseudophakic eyes: A systematic review and meta-analysis

PURPOSE

To assess the effectiveness and safety of combining intravitreal endothelial growth factor inhibitor (anti-VEGF) and ocular corticosteroids for diabetic macular edema (DME).

METHODS

Articles concentrating on the efficacy and safety of combining anti-VEGF and ocular corticosteroids therapy for DME versus anti-VEGF monotherapy was screened systematically. Meta-analysis was conducted on the basis of a protocol registered in the PROSPERO (CRD42023408338) and performed on the extracted continuous variables and dichotomous variables. The outcome was expressed as weighted mean difference (MD) and risk ratio (RR).

RESULTS

Add up to 21 studies including 1468 eyes were enrolled in this study. The MD for best-corrected visual acuity (BCVA) improvement at 1/3/6/12-month between the combination therapy group and monotherapy group were 2.56 (95% CI [0.43, 4.70]), 2.46 (95% CI [-0.40, 5.32]), - 1.76 (95% CI [-3.18, -0.34]), - 1.94 (95% CI [-3.87, 0.00]), respectively. The MD for central retinal thickness (CMT) reduction at 1/3/6/12-month between two groups were - 66.27 (95% CI [-101.08, -31.47]), - 33.62 (95% CI [-57.55, -9.70]), - 4.54 (95% CI [-16.84, 7.76]), - 26.67 (95% CI [-41.52, -11.82]), respectively. Additionally, the combination group had higher relative risk of high intraocular pressure and cataract progression events.

CONCLUSIONS

Anti-VEGF combined with ocular corticosteroids had a significant advantage over anti-VEGF monotherapy within 3 months of DME treatment, which reached the maximum with increasing anti-VEGF injection times to 3. However, with the prolongation of the treatment cycle, the effect of combined therapy after 6 months was no better than monotherapy, and the side effects of combined therapy were more severe.