Relationship between Pericytes and Endothelial Cells in Retinal Neovascularization: A Histological and Immunofluorescent Study of Retinal Angiogenesis

Single-cell RNA sequencing analysis of the retina under acute high intraocular pressure

JOURNAL/nrgr/04.03/01300535-202419110-00032/figure1/v/2024-03-08T184507Z/r/image-tiff High intraocular pressure causes retinal ganglion cell injury in primary and secondary glaucoma diseases, yet the molecular landscape characteristics of retinal cells under high intraocular pressure remain unknown. Rat models of acute hypertension ocular pressure were established by injection of cross-linked hyaluronic acid hydrogel (Healaflow®). Single-cell RNA sequencing was then used to describe the cellular composition and molecular profile of the retina following high intraocular pressure. Our results identified a total of 12 cell types, namely retinal pigment epithelial cells, rod-photoreceptor cells, bipolar cells, Müller cells, microglia, cone-photoreceptor cells, retinal ganglion cells, endothelial cells, retinal progenitor cells, oligodendrocytes, pericytes, and fibroblasts. The single-cell RNA sequencing analysis of the retina under acute high intraocular pressure revealed obvious changes in the proportions of various retinal cells, with ganglion cells decreased by 23%. Hematoxylin and eosin staining and TUNEL staining confirmed the damage to retinal ganglion cells under high intraocular pressure. We extracted data from retinal ganglion cells and analyzed the retinal ganglion cell cluster with the most distinct expression. We found upregulation of the B3gat2 gene, which is associated with neuronal migration and adhesion, and downregulation of the Tsc22d gene, which participates in inhibition of inflammation. This study is the first to reveal molecular changes and intercellular interactions in the retina under high intraocular pressure. These data contribute to understanding of the molecular mechanism of retinal injury induced by high intraocular pressure and will benefit the development of novel therapies.

Specific ablation of PDGFRβ-overexpressing pericytes with antibody-drug conjugate potently inhibits pathologic ocular neovascularization in mouse models

BACKGROUND

Crosstalk between pericytes and endothelial cells is critical for ocular neovascularization. Endothelial cells secrete platelet-derived growth factor (PDGF)-BB and recruit PDGF receptor β (PDGFRβ)-overexpressing pericytes, which in turn cover and stabilize neovessels, independent of vascular endothelial growth factor (VEGF). Therapeutic agents inhibiting PDGF-BB/PDGFRβ signaling were tested in clinical trials but failed to provide additional benefits over anti-VEGF agents. We tested whether an antibody-drug conjugate (ADC) - an engineered monoclonal antibody linked to a cytotoxic agent - could selectively ablate pericytes and suppress retinal and choroidal neovascularization.

METHODS

Immunoblotting, flow cytometry, cell viability test, and confocal microscopy were conducted to assess the internalization and cytotoxic effect of ADC targeting mPDGFRβ in an in vitro setting. Immunofluorescence staining of whole-mount retinas and retinal pigment epithelium-choroid-scleral complexes, electroretinography, and OptoMotry test were used to evaluate the effect and safety of ADC targeting mPDGFRβ in the mouse models of pathologic ocular neovascularization.

RESULTS

ADC targeting mPDGFRβ is effectively internalized into mouse brain vascular pericytes and showed significant cytotoxicity compared with the control ADC. We also show that specific ablation of PDGFRβ-overexpressing pericytes using an ADC potently inhibits pathologic ocular neovascularization in mouse models of oxygen-induced retinopathy and laser-induced choroidal neovascularization, while not provoking generalized retinal toxicity.

CONCLUSION

Our results suggest that removing PDGFRβ-expressing pericytes by an ADC targeting PDGFRβ could be a potential therapeutic strategy for pathologic ocular neovascularization.

Ferulic Acid-Loaded Polymeric Nanoparticles for Potential Ocular Delivery

Ferulic acid (FA) is an antioxidant compound that can prevent ROS-related diseases, but due to its poor solubility, therapeutic efficacy is limited. One strategy to improve the bioavailability is nanomedicine. In the following study, FA delivery through polymeric nanoparticles (NPs) consisting of polylactic acid (NPA) and poly(lactic-co-glycolic acid) (NPB) is proposed. To verify the absence of cytotoxicity of blank carriers, a preliminary in vitro assay was performed on retinal pericytes and endothelial cells. FA-loaded NPs were subjected to purification studies and the physico-hemical properties were analyzed by photon correlation spectroscopy. Encapsulation efficiency and in vitro release studies were assessed through high performance liquid chromatography. To maintain the integrity of the systems, nanoformulations were cryoprotected and freeze-dried. Morphology was evaluated by a scanning electron microscope. Physico-chemical stability of resuspended nanosystems was monitored during 28 days of storage at 5 °C. Thermal analysis and Fourier-transform infrared spectroscopy were performed to characterize drug state in the systems. Results showed homogeneous particle populations, a suitable mean size for ocular delivery, drug loading ranging from 64.86 to 75.16%, and a controlled release profile. The obtained systems could be promising carriers for ocular drug delivery, legitimating further studies on FA-loaded NPs to confirm efficacy and safety in vitro.

Retinal Vascular Endothelial Cell Dysfunction and Neuroretinal Degeneration in Diabetic Patients

Diabetes mellitus (DM) has become a vital societal problem as epidemiological studies demonstrate the increasing incidence of type 1 and type 2 diabetes. Lesions observed in the retina in the course of diabetes, referred to as diabetic retinopathy (DR), are caused by vascular abnormalities and are ischemic in nature. Vascular lesions in diabetes pertain to small vessels (microangiopathy) and involve precapillary arterioles, capillaries and small veins. Pericyte loss, thickening of the basement membrane, and damage and proliferation of endothelial cells are observed. Endothelial cells (monolayer squamous epithelium) form the smooth internal vascular lining indispensable for normal blood flow. Breaking its continuity initiates blood coagulation at that site. The endothelium controls the process of exchange of chemical substances (nutritional, regulatory, waste products) between blood and the retina, and blood cell passing through the vascular wall. Endothelial cells produce biologically active substances involved in blood coagulation, regulating vascular wall tension and stimulating neoangiogenesis. On the other hand, recent studies have demonstrated that diabetic retinopathy may be not only a microvascular disease, but is a result of neuroretinal degeneration. Neuroretinal degeneration appears structurally, as neural apoptosis of amacrine and Muller cells, reactive gliosis, ganglion cell layer/inner plexiform (GCL) thickness, retinal thickness, and retinal nerve fiber layer thickness, and a reduction of the neuroretinal rim in minimum rim width (MRW) and functionally as an abnormal electroretinogram (ERG), dark adaptation, contrast sensitivity, color vision, and microperimetric test. The findings in early stages of diabetic retinopathy may precede microvascular changes of this disease. Furthermore, the article's objective is to characterize the factors and mechanisms conducive to microvascular changes and neuroretinal apoptosis in diabetic retinopathy. Only when all the measures preventing vascular dysfunction are determined will the risk of complications in the course of diabetes be minimized.

Cluster Analysis of Early Postnatal Biochemical Markers May Predict Development of Retinopathy of Prematurity

Purpose

Growth factors and inflammatory and angiogenetic proteins are involved in the development of retinopathy of prematurity (ROP). However, no early biochemical markers are in clinical use to predict ROP. By performing cluster analysis of multiple biomarkers, we aimed to determine patient groups with high and low risk for developing ROP.

Methods

In total, 202 protein markers in plasma were quantified by proximity extension assay from 35 extremely preterm infants on day 2 of life. Infants were sorted in groups by automated two-dimensional hierarchical clustering of all biomarkers. ROP was classified as stages I to III with or without surgical treatment. Predictive biomarkers were evaluated by analysis of variance and detected differences by two-sided paired t-test with Bonferroni corrections for multiple comparisons.

Results

Differences in 39 biochemical markers divided infants without ROP into two control groups (control 1, n = 7; control 2, n = 5; P < 0.05). Sixty-six biochemical markers defined differences between the control groups (n = 13) and all ROP infants (n = 23; P < 0.05). PARK7, VIM, MPO, CD69, and NEMO were markedly increased in control 1 compared to all ROP infants (P < 0.001). Lower TNFRSF4 and higher HER2 and GAL appeared in infants with ROP as compared to control 1 and/or 2 (P < 0.05, respectively).

Conclusions

Our data suggest that early elevated levels of PARK7, VIM, MPO, CD69, and NEMO may be associated with lower risk of developing ROP. Lower levels of TNFRSF4 with higher levels of HER2 and GAL may predict ROP development.

Translational Relevance

Cluster analysis of early postnatal biomarkers may help to identify infants with low or high risk of developing ROP.

miR‑133b regulates proliferation and apoptosis in high‑glucose‑induced human retinal endothelial cells by targeting ras homolog family member A

The aim of the present study was to investigate the role of microRNA (miR)‑133b in high‑glucose‑induced human retinal endothelial cells (hRECs), particularly regarding its potential targeting of ras homolog family member A (RhoA). To establish the high‑glucose‑induced diabetic retinopathy (DR) model, hRECs were cultured in high‑glucose medium for 1, 2 and 3 days. An Annexin allophycocyanin (APC)/7‑aminoactinomycin D (7‑AAD) staining assay was performed to measure the apoptosis of hRECs. Next, the cells were transfected with miR‑133b inhibitors or mimics, and the cell proliferation and apoptosis were measured by MTT and Annexin‑APC/7‑AAD staining assays, respectively. In addition, reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR), western blotting and immunocytochemistry were used to detect the expression levels of RhoA, Rho‑associated protein kinase 1 (ROCK1), LIM domain kinase 1 (LIMK), myosin light chain (MLC) and phosphorylated (p)‑MLC. It was observed that high‑glucose or miR‑133b inhibitor treatment attenuated the apoptosis of hRECs, and upregulated the mRNA and protein expression levels of RhoA, ROCK1 and LIMK, as well as the p‑MLC protein level, in the hRECs. However, miR‑133b overexpression inhibited the cell proliferation, promoted apoptosis, and downregulated the mRNA and protein levels of RhoA, ROCK1 and LIMK, as well as p‑MLC protein, in high‑glucose‑induced hRECs. In conclusion, overexpression of miR‑133b inhibited the proliferation and promoted apoptosis in a DR cell model by downregulating RhoA expression.