Transcription factor SP1 mediates hyperglycemia-induced upregulation of roundabout4 in retinal microvascular endothelial cells

PTEN in kidney diseases: a potential therapeutic target in preventing AKI-to-CKD transition

Renal fibrosis, a critical factor in the development of chronic kidney disease (CKD), is predominantly initiated by acute kidney injury (AKI) and subsequent maladaptive repair resulting from pharmacological or pathological stimuli. Phosphatase and tensin homolog (PTEN), also known as phosphatase and tensin-associated phosphatase, plays a pivotal role in regulating the physiological behavior of renal tubular epithelial cells, glomeruli, and renal interstitial cells, thereby preserving the homeostasis of renal structure and function. It significantly impacts cell proliferation, apoptosis, fibrosis, and mitochondrial energy metabolism during AKI-to-CKD transition. Despite gradual elucidation of PTEN's involvement in various kidney injuries, its specific role in AKI and maladaptive repair after injury remains unclear. This review endeavors to delineate the multifaceted role of PTEN in renal pathology during AKI and CKD progression along with its underlying mechanisms, emphasizing its influence on oxidative stress, autophagy, non-coding RNA-mediated recruitment and activation of immune cells as well as renal fibrosis. Furthermore, we summarize prospective therapeutic targeting strategies for AKI and CKD-treatment related diseases through modulation of PTEN.

USP5 facilitates diabetic retinopathy development by stabilizing ROBO4 via deubiquitination

Ubiquitin-specific proteases (USPs) have been proved to play important roles in the progression of diabetic retinopathy. In this study, we explored the role of USP5 and its possible mechanisms in diabetic retinopathy development. Cell proliferation, apoptosis, inflammation and oxidative stress were determined using CCK-8 assay, EdU staining assay, flow cytometry, and ELISA, respectively. The mRNA and protein expression of ROBO4 and USP5 were measured through RT-qPCR and western blot, respectively. Co-IP and deubiquitination assay were conducted to evaluate the interaction between ROBO4 and USP5. The results showed that high glucose (HG) stimulation significantly led to HRPE cell damage as described by suppressing proliferation, and promoting oxidative stress, inflammation and apoptosis. ROBO4 was markedly increased in diabetic retinopathy plasma samples and HG-triggered HRPE cells. Depletion of ROBO4 could alleviate HG-caused HRPE cell damage. USP5 was also significantly elevated in diabetic retinopathy plasma samples and HG-triggered HRPE cells. USP5 overexpression aggravated HG-induced HRPE cell damage. USP5 stabilized ROBO4 through deubiquitination. Moreover, USP5 knockdown decreased ROBO4 expression to mitigate HG-triggered cell damage in HRPE cells. USP5 stabilized ROBO4 via deubiquitination to repress cell proliferation, and facilitate inflammation, cell apoptosis and oxidative stress in HG-treated HRPE cells, thereby promoting the development of diabetic retinopathy.

Canagliflozin protects against hyperglycemia-induced cerebrovascular injury by preventing blood-brain barrier (BBB) disruption via AMPK/Sp1/adenosine A2A receptor

Diabetes mellitus causes brain microvascular endothelial cell (MEC) damage, inducing dysfunctional angiogenic response and disruption of the blood-brain barrier (BBB). Canagliflozin is a revolutionary hypoglycemic drug that exerts neurologic and/or vascular-protective effects beyond glycemic control; however, its underlying mechanism remains unclear. In the present study, we hypothesize that canagliflozin ameliorates BBB permeability by preventing diabetes-induced brain MEC damage. Mice with high-fat diet/streptozotocin-induced diabetes received canagliflozin for 8 weeks. We assessed vascular integrity by measuring cerebrovascular neovascularization indices. The expression of specificity protein 1 (Sp1), as well as tight junction proteins (TJs), phosphorylated AMP-activated protein kinase (p-AMPK), and adenosine A2A receptors was examined. Mouse brain MECs were grown in high glucose (30 mM) to mimic diabetic conditions. They were treated with/without canagliflozin and assessed for migration and angiogenic ability. We also performed validation studies using AMPK activator (AICAR), inhibitor (Compound C), Sp1 small interfering RNA (siRNA), and adenosine A2A receptor siRNA. We observed that cerebral pathological neovascularization indices were significantly normalized in mice treated with canagliflozin. Increased Sp1 and adenosine A2A receptor expression and decreased p-AMPK and TJ expression were observed under diabetic conditions. Canagliflozin or AICAR treatment alleviated these changes. However, this alleviation effect of canagliflozin was diminished again after Compound C treatment. Either Sp1 siRNA or adenosine A2A receptor siRNA could increase the expression of TJs. Luciferase reporter assay confirmed that Sp1 could bind to the adenosine A2A receptor gene promoter. Our study identifies the AMPK/Sp1/adenosine A2A receptor pathway as a treatment target for diabetes-induced cerebrovascular injury.

AMPK-SP1-Guided Dynein Expression Represents a New Energy-Responsive Mechanism and Therapeutic Target for Diabetic Nephropathy

Key Points

AMP kinase senses diabetic stresses in podocytes, subsequently upregulates specificity protein 1–mediated dynein expression and promotes podocyte injury. Pharmaceutical restoration of dynein expression by targeting specificity protein 1 represents an innovative therapeutic strategy for diabetic nephropathy.

Background

Diabetic nephropathy (DN) is a major complication of diabetes. Injury to podocytes, epithelial cells that form the molecular sieve of a kidney, is a preclinical feature of DN. Protein trafficking mediated by dynein, a motor protein complex, is a newly recognized pathophysiology of diabetic podocytopathy and is believed to be derived from the hyperglycemia-induced expression of subunits crucial for the transportation activity of the dynein complex. However, the mechanism underlying this transcriptional signature remains unknown.

Methods

Through promoter analysis, we identified binding sites for transcription factor specificity protein 1 (SP1) as the most shared motif among hyperglycemia-responsive dynein genes. We demonstrated the essential role of AMP-activated protein kinase (AMPK)–regulated SP1 in the transcription of dynein subunits and dynein-mediated trafficking in diabetic podocytopathy using chromatin immunoprecipitation quantitative PCR and live cell imaging. SP1-dependent dynein-driven pathogenesis of diabetic podocytopathy was demonstrated by pharmaceutical intervention with SP1 in a mouse model of streptozotocin-induced diabetes.

Results

Hyperglycemic conditions enhance SP1 binding to dynein promoters, promoted dynein expression, and enhanced dynein-mediated mistrafficking in cultured podocytes. These changes can be rescued by chemical inhibition or genetic silencing of SP1. The direct repression of AMPK, an energy sensor, replicates hyperglycemia-induced dynein expression by activating SP1. Mithramycin inhibition of SP1-directed dynein expression in streptozotocin-induced diabetic mice protected them from developing podocytopathy and prevented DN progression.

Conclusions

Our work implicates AMPK-SP1–regulated dynein expression as an early mechanism that translates energy disturbances in diabetes into podocyte dysfunction. Pharmaceutical restoration of dynein expression by targeting SP1 offers a new therapeutic strategy to prevent DN.

DNA hypomethylation of Syk induces oxidative stress and apoptosis via the PKCβ/P66shc signaling pathway in diabetic kidney disease

Epigenetic alterations, especially DNA methylation, have been shown to play a role in the pathogenesis of diabetes mellitus (DM) and its complications, including diabetic kidney disease (DKD). Spleen tyrosine kinase (Syk) is known to be involved in immune and inflammatory disorders. We, therefore, investigated the possible involvement of Syk promoter methylation in DKD, and the mechanisms underlying this process. Kidney tissues were obtained from renal biopsies of patients with early and advanced DKD. A diabetic mouse model (ApoE-/- DM) was generated from ApoE knockout (ApoE-/-) mice using a high-fat and high-glucose diet combined with low-dose streptozocin intraperitoneal injection. We also established an in vitro model using HK2 cells. A marked elevation in the expression levels of Syk, PKCβ, and P66shc in renal tubules was observed in patients with DKD. In ApoE-/- DM mice, Syk expression and the binding of Sp1 to the Syk gene promoter were both increased in the kidney. In addition, the promoter region of the Syk gene exhibited hypomethylation. Syk inhibitor (R788) intervention improved renal function and alleviated pathologic changes in ApoE-/- DM mice. Moreover, R788 intervention alleviated oxidative stress and apoptosis and downregulated the expression of PKCβ/P66shc signaling pathway proteins. In HK2 cells, oxLDL combined with high-glucose stimulation upregulated Sp1 expression in the nucleus (compared with control and oxLDL groups), and this was accompanied by an increase in the binding of Sp1 to the Syk gene promoter. SP1 silencing downregulated the expression of Syk and inhibited the production of reactive oxygen species and cell apoptosis. Finally, PKC agonist intervention reversed the oxidative stress and apoptosis induced by Syk inhibitor (R406). In DKD, hypomethylation at the Syk gene promoter was accompanied by an increase in Sp1 binding at the promoter. As a consequence of this enhanced Sp1 binding, Syk gene expression was upregulated. Syk inhibitors could attenuate DKD-associated oxidative stress and apoptosis via downregulation of PKCβ/P66shc signaling pathway proteins. Together, our results identify Syk as a promising target for intervention in DKD.

Identification of a potentially functional circRNA-miRNA-mRNA regulatory network in type 2 diabetes mellitus by integrated microarray analysis

BACKGROUND

Circular RNAs (circRNAs) function as miRNA sponges by adsorbing microRNAs (miRNAs), thereby regulating messenger RNA (mRNA) expression. The circRNA-miRNA-mRNA regulatory network associated with type 2 diabetes mellitus (T2DM) has rarely been explored. A circRNA-miRNA-mRNA regulatory network associated with T2DM was established to help deepen our understanding of the molecular mechanism of and therapeutic targets for T2DM.

METHODS

Differentially expressed circRNAs (DEcircRNAs), miRNAs (DEmiRNAs), and mRNAs (DEmRNAs) were derived from the Gene Expression Omnibus (GEO) microarray datasets GSE114248, GSE51674 and GSE95849, respectively. A circRNA-miRNA-mRNA regulatory network associated with T2DM and its subnetwork were constructed. The hub genes were screened using a protein-protein interaction (PPI) network. Finally, a hub gene-related network was constructed. Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed.

RESULTS

The circRNA-miRNA-mRNA network included 9 circRNAs, 24 miRNAs and 320 mRNAs. When four key circRNAs (circMYO9B, circGRAMD1B, circTHAP4 and circTMC7) were chosen, the subnetwork contained 4 circRNAs, 18 miRNAs and 307 mRNAs. Afterwards, 8 hub genes (SIRT1, GNG7, KDR, FOS, SIN3B, STAT1, SP1, and MAPK3) were extracted from the PPI network. GO and KEGG pathway analyses revealed that the network might be involved in oxidative stress responses, regulation of inflammation, neovascularization, endocrine and cancer-related processes, etc.

CONCLUSIONS

A circRNA-miRNA-hub gene regulatory network was constructed, and the potential functions of the hub genes were analyzed. Four important circRNAs (circMYO9B, circGRAMD1B, circTHAP4 and circTMC7) might be involved in the occurrence and development of T2DM, and this finding provides new insight into the molecular mechanism of and therapeutic targets for T2DM and its complications. Future studies are needed to validate the sponge effects and mechanisms of these 4 circRNAs.

Endothelial Robo4 suppresses endothelial-to-mesenchymal transition induced by irradiation and improves hematopoietic reconstitution

Bone marrow ablation is routinely performed before hematopoietic stem cell transplantation (HSCT). Hematopoietic stem and progenitor cells (HSPCs) require a stable bone marrow microenvironment to expand and refill the peripheral blood cell pool after ablation. Roundabout guidance receptor 4 (Robo4) is a transmembrane protein exclusive to endothelial cells and is vital in preserving vascular integrity. Hence, the hypothesis is that Robo4 maintains the integrity of bone marrow endothelial cells following radiotherapy. We created an endothelial cell injury model with γ-radiation before Robo4 gene manipulation using lentiviral-mediated RNAi and gene overexpression techniques. We demonstrate that Robo4 and specific mesenchymal proteins (Fibronectin, Vimentin, αSma, and S100A4) are upregulated in endothelial cells exposed to irradiation (IR). We found that Robo4 depletion increases the expression of endoglin (CD105), an auxiliary receptor for the transforming growth factor (TGF-β) family of proteins, and promotes endothelial-to-mesenchymal transition (End-MT) through activation of both the canonical (Smad) and non-canonical (AKT/NF-κB) signaling pathways to facilitate Snail1 activation and its nuclear translocation. Endothelial Robo4 overexpression stimulates the expression of immunoglobulin-like adhesion molecules (ICAM-1 and VCAM-1) and alleviates irradiation-induced End-MT. Our coculture model showed that transcriptional downregulation of endothelial Robo4 reduces HSPC proliferation and increases HSC quiescence and apoptosis. However, Robo4 overexpression mitigated the damaged endothelium's suppressive effects on HSC proliferation and differentiation. These findings indicate that by controlling End-MT, Robo4 preserves microvascular integrity after radiation preconditioning, protects endothelial function, and lessens the inhibitory effect of damaged endothelium on hematopoietic reconstitution.

The role of TET2-mediated ROBO4 hypomethylation in the development of diabetic retinopathy

BACKGROUND

In diabetic retinopathy, increasing evidence points to a link between the pathogenesis of retinal microangiopathy and the endothelial cell-specific factor roundabout4 (ROBO4). According to earlier research, specificity protein 1 (SP1) enhances the binding to the ROBO4 promoter, increasing Robo4 expression and hastening the progression of diabetic retinopathy. To determine if this is related to aberrant epigenetic modifications of ROBO4, we examined the methylation level of the ROBO4 promoter and the corresponding regulatory mechanism during the course of diabetic retinopathy and explored the effect of this mechanism on retinal vascular leakage and neovascularization.

METHODS

The methylation level of CpG sites in the ROBO4 promoter was detected in human retinal endothelial cells (HRECs) cultured under hyperglycemic conditions and retinas from streptozotocin-induced diabetic mice. The effects of hyperglycemia on DNA methyltransferase 1, Tet methylcytosine dioxygenase 2 (TET2), 5-methylcytosine, 5-hydroxymethylcytosine, and the binding of TET2 and SP1 to the ROBO4 promoter, as well as the expression of ROBO4, zonula occludens 1 (ZO-1) and occludin were examined. Short hairpin RNA was used to suppress the expression of TET2 or ROBO4 and the structural and functional changes in the retinal microvascular system were assessed.

RESULTS

In HRECs cultured under hyperglycemic conditions, the ROBO4 promoter methylation level decreased. Hyperglycemia-induced TET2 overexpression caused active demethylation of ROBO4 by oxidizing 5-methylcytosine to 5-hydroxymethylcytosine, which enhanced the binding of SP1 to ROBO4, increased the expression of ROBO4, and decreased the expression of ZO-1 and occludin, leading to the abnormalities in monolayer permeability, migratory ability and angiogenesis of HRECs. The above pathway was also demonstrated in the retinas of diabetic mice, which caused leakage from retinal capillaries and neovascularization. Inhibition of TET2 or ROBO4 expression significantly ameliorated the dysfunction of HRECs and retinal vascular abnormalities.

CONCLUSIONS

In diabetes, TET2 can regulate the expression of ROBO4 and its downstream proteins by mediating active demethylation of the ROBO4 promoter, which accelerates the development of retinal vasculopathy. These findings suggest that TET2-induced ROBO4 hypomethylation is a potential therapeutic target, and anti- TET2/ROBO4 therapy is anticipated to emerge as a novel strategy for early intervention and delayed progression of diabetic retinopathy.

Sp1 promotes tumour progression by remodelling the mitochondrial network in cervical cancer

BACKGROUND

Cervical cancer remains one of the most prevalent cancers worldwide. Accumulating evidence suggests that specificity protein 1 (Sp1) plays a pivotal role in tumour progression. The underlying role and mechanism of Sp1 in tumour progression remain unclear.

METHODS

The protein level of Sp1 in tumour tissues was determined by immunohistochemistry. The effect of Sp1 expression on the biological characteristics of cervical cancer cells was assessed by colony, wound healing, transwell formation, EdU, and TUNEL assays. Finally, the underlying mechanisms and effects of Sp1 on the mitochondrial network and metabolism of cervical cancer were analysed both in vitro and in vivo.

RESULTS

Sp1 expression was upregulated in cervical cancer. Sp1 knockdown suppressed cell proliferation both in vitro and in vivo, while overexpression of Sp1 had the opposite effects. Mechanistically, Sp1 facilitated mitochondrial remodelling by regulating mitofusin 1/2 (Mfn1/2), OPA1 mitochondrial dynamin-like GTPase (Opa1), and dynamin 1-like (Drp1). Additionally, the Sp1-mediated reprogramming of glucose metabolism played a critical role in the progression of cervical cancer cells.

CONCLUSIONS

Our study demonstrates that Sp1 plays a vital role in cervical tumorigenesis by regulating the mitochondrial network and reprogramming glucose metabolism. Targeting Sp1 could be an effective strategy for the treatment of cervical cancer.

The SLIT/ROBO Pathway in Liver Fibrosis and Cancer

Liver fibrosis is a common outcome of most chronic liver insults/injuries that can develop into an irreversible process of cirrhosis and, eventually, liver cancer. In recent years, there has been significant progress in basic and clinical research on liver cancer, leading to the identification of various signaling pathways involved in tumorigenesis and disease progression. Slit glycoprotein (SLIT)1, SLIT2, and SLIT3 are secreted members of a protein family that accelerate positional interactions between cells and their environment during development. These proteins signal through Roundabout receptor (ROBO) receptors (ROBO1, ROBO2, ROBO3, and ROBO4) to achieve their cellular effects. The SLIT and ROBO signaling pathway acts as a neural targeting factor regulating axon guidance, neuronal migration, and axonal remnants in the nervous system. Recent findings suggest that various tumor cells differ in SLIT/ROBO signaling levels and show varying degrees of expression patterns during tumor angiogenesis, cell invasion, metastasis, and infiltration. Emerging roles of the SLIT and ROBO axon-guidance molecules have been discovered in liver fibrosis and cancer development. Herein, we examined the expression patterns of SLIT and ROBO proteins in normal adult livers and two types of liver cancers: hepatocellular carcinoma and cholangiocarcinoma. This review also summarizes the potential therapeutics of this pathway for anti-fibrosis and anti-cancer drug development.

Knockdown of Krüppel-Like Factor 9 Inhibits Aberrant Retinal Angiogenesis and Mitigates Proliferative Diabetic Retinopathy

Advanced proliferative diabetic retinopathy (PDR) characterized by aberrant retinal angiogenesis is a leading cause of retinal detachment and blindness. Krüppel-like factor 9 (KLF9), a member of the zinc-finger family of transcription factors, participates in the development of diabetic nephropathy and the promotion of angiogenesis of human umbilical vein endothelial cells. Therefore, we speculate that KLF9 may exert a crucial role in PDR. The current study revealed that KLF9 was highly expressed in the high glucose (HG)-treated human retinal microvascular endothelial cells (HRMECs) and the retinas of oxygen-induced retinopathy (OIR) rats. Knockdown of KLF9 inhibited the proliferation, migratory capability, invasiveness and tube formation of HG-treated HRMECs. Besides, knockdown of KLF9 decreased the expression of yes-associated protein 1 (YAP1) in HG-treated HRMECs. Dual-luciferase reporter assays confirmed that KLF9 transcriptionally upregulated YAP1 expression. Overexpression of YAP1 reversed the KLF9 silencing-induced repression of HRMEC proliferation and tube formation. Further in vivo evidence demonstrated that knockdown of KLF9 reduced the expression of Ki67, CD31 and vascular endothelial growth factor A (VEGFA) in the retinas of OIR rats. Collectively, KLF9 silencing might mitigate the progression of PDR by inhibiting angiogenesis via blocking YAP1 transcription.

Regulation of peroxiredoxin-3 gene expression under basal and hyperglycemic conditions: Key roles for transcription factors Sp1, CREB and NF-κB

Peroxiredoxin-3 (Prx-3), a thioredoxin-dependent peroxidase located exclusively in the mitochondrial matrix, catalyses peroxides/peroxinitrites. Altered levels of Prx-3 is associated with diabetic cardiomyopathy (DCM). However, molecular mechanisms of Prx-3 gene regulation remain partially understood. We undertook a systemic analysis of the Prx-3 gene to identify the key motifs and transcriptional regulatory molecules. Transfection of promoter-reporter constructs in the cultured cells identified -191/+20 bp domain as the core promoter region. Stringent in silico analysis of this core promoter revealed putative binding sites for specificity protein 1 (Sp1), cAMP response element-binding protein (CREB) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Interestingly, while co-transfection of the -191/+20 bp construct with Sp1/CREB plasmid diminished Prx3 promoter-reporter activity, mRNA and protein levels, co-transfection with NF-κB expression plasmid augmented the same. Consistently, inhibition of Sp1/CREB/NF-κB expression reversed the promoter-reporter activity, mRNA and protein levels of Prx-3, thereby confirming their regulatory effects. ChIP assays provided evidence for interactions of Sp1/CREB/NF-κB with the Prx-3 promoter. H9c2 cells treated with high glucose as well as streptozotocin (STZ)-treated diabetic rats showed time-dependent reduction in promoter activity, endogenous transcript and protein levels of Prx-3. Augmentation of Sp1/CREB protein levels and their strong binding with Prx-3 promoter are responsible for diminished Prx-3 levels under hyperglycemia. The activation/increase in the NF-κB expression under hyperglycemia was not sufficient to restore the reduction of endogenous Prx-3 levels owing to its weak binding affinity. Taken together, this study elucidates the previously unknown roles of Sp1/CREB/NF-κB in regulating Prx-3 gene expression under hyperglycemic condition.

Angiotensin-converting enzyme inhibitor promotes angiogenesis through Sp1/Sp3-mediated inhibition of notch signaling in male mice

Angiogenesis is a critical pathophysiological process involved in organ growth and various diseases. Transcription factors Sp1/Sp3 are necessary for fetal development and tumor growth. Sp1/Sp3 proteins were downregulated in the capillaries of the gastrocnemius in patients with critical limb ischemia samples. Endothelial-specific Sp1/Sp3 knockout reduces angiogenesis in retinal, pathological, and tumor models and induced activation of the Notch1 pathway. Further, the inactivation of VEGFR2 signaling by Notch1 contributes to the delayed angiogenesis phenotype. Mechanistically, endothelial Sp1 binds to the promoter of Notch1 and inhibits its transcription, which is enhanced by Sp3. The proangiogenic effect of ACEI is abolished in Sp1/Sp3-deletion male mice. We identify USP7 as an ACEI-activated deubiquitinating enzyme that translocated into the nucleus binding to Sp1/Sp3, which are deacetylated by HDAC1. Our findings demonstrate a central role for endothelial USP7-Sp1/Sp3-Notch1 signaling in pathophysiological angiogenesis in response to ACEI treatment.

Robo4 inhibits gamma radiation-induced permeability of a murine microvascular endothelial cell by regulating the junctions

BACKGROUND

Hematopoietic stem cell transplantation involves irradiation preconditioning which causes bone marrow endothelial cell dysfunction. While much emphasis is on the reconstitution of hematopoietic stem cells in the bone marrow microenvironment, endothelial cell preservation is indispensable to overcome the preconditioning damages. This study aims to ascertain the role of Roundabout 4 (Robo4) in regulating irradiation-induced damage to the endothelium.

METHODS

Microvascular endothelial cells were treated with γ-radiation to establish an endothelial cell injury model. Robo4 expression in the endothelial cells was manipulated employing lentiviral-mediated RNAi and gene overexpression technology before irradiation treatment. The permeability of endothelial cells was measured using qPCR, immunocytochemistry, and immunoblotting to analyze the effect on the expression and distribution of junctional molecules, adherens junctions, tight junctions, and gap junctions. Using Transwell endothelial monolayer staining, FITC-Dextran permeability, and gap junction-mediated intercellular communication (GJIC) assays, we determined the changes in endothelial functions after Robo4 gene manipulation and irradiation. Moreover, we measured the proportion of CD31 expression in endothelial cells by flow cytometry. We analyzed variations between two or multiple groups using Student's t-tests and ANOVA.

RESULTS

Ionizing radiation upregulates Robo4 expression but disrupts endothelial junctional molecules. Robo4 deletion causes further degradation of endothelial junctions hence increasing the permeability of the endothelial cell monolayer. Robo4 knockdown in microvascular endothelial cells increases the degradation and delocalization of ZO-1, PECAM-1, occludin, and claudin-5 molecules after irradiation. Conversely, connexin 43 expression increases after silencing Robo4 in endothelial cells to induce permeability but are readily destroyed when exposed to 10 Gy of gamma radiation. Also, Robo4 knockdown enhances Y731-VE-cadherin phosphorylation leading to the depletion and destabilization of VE-cadherin at the endothelial junctions following irradiation. However, Robo4 overexpression mitigates irradiation-induced degradation of tight junctional proteins and stabilizes claudin-5 and ZO-1 distribution. Finally, the enhanced expression of Robo4 ameliorates the irradiation-induced depletion of VE-cadherin and connexin 43, improves the integrity of microvascular endothelial cell junctions, and decreases permeability.

CONCLUSION

This study reveals that Robo4 maintains microvascular integrity after radiation preconditioning treatment by regulating endothelial permeability and protecting endothelial functions. Our results also provided a potential mechanism to repair the bone marrow vascular niche after irradiation by modulating Robo4 expression.

The potential function of SP1 and CPPED1 in restenosis after percutaneous coronary intervention

OBJECTIVES

Impacts of molecular pathways have been discussed recently on restenosis after percutaneous coronary intervention (PCI). Hence, this study aimed to explore the impact of calcineurin-like phosphoesterase domain containing 1 (CPPED1) and specificity protein 1 (SP1) on restenosis after PCI.

METHODS

A carotid balloon injury rat model was established, followed by western blot analysis of SP1 and CPPED1 expression in carotid artery (CA) tissues. After SP1 and CPPED1 were overexpressed, the neointimal hyperplasia and luminal stenosis were assessed. In addition, EPC underwent hypoxia/reoxygenation (H/R) treatment to construct an endothelial injury cell model. Then, cell proliferation, apoptosis, intracellular reactive oxygen species (ROS), and Ca²⁺ concentration were detected with cell counting kit-8 (CCK-8), flow cytometry, Chloromethyl-2'7'-dichlorofluorescein diacetate (CM-H2DCFDA) penetrant, and Fluo-4 AM staining, respectively. The binding relationship between SP1 and CPPED1 was verified by dual-luciferase reporter and chromatin immunoprecipitation (ChIP) assays.

RESULTS

SP1 and CPPED1 were lowly expressed in the model rats with carotid balloon injury. Mechanistically, SP1 bound to the promoter region of CPPED1 to activate CPPED1 expression. Overexpressing SP1 or CPPED1 lowered neointimal formation and restenosis rate, thus promoting the recovery of carotid balloon injury in rats. Meanwhile, SP1 and CPPED1 upregulation reduced ROS levels, Ca²⁺ concentration, and apoptosis of EPCs, accompanied by accelerated EPC viability.

CONCLUSIONS

SP1 or CPPED1 overexpression reduced neointimal formation and restenosis rate in carotid balloon injury.

SP1-mediated transcriptional activation of PTTG1 regulates the migration and phenotypic switching of aortic vascular smooth muscle cells in aortic dissection through MAPK signaling

Pituitary tumor-transforming gene 1 (PTTG1) has been found to be associated with the process of cell proliferation and invasion, and is highly expressed in aortic dissection (AD). However, its potential role and underlying mechanism in AD remain uncertain. This study aims at elucidating the roles of specificity protein 1 (SP1) and PTTG1 in the migration and phenotypic switching of aortic vascular smooth muscle cells (VSMCs) in AD. Aortic samples were collected from 35 patients with AD for examination of PTTG1 expression in the tissues by qPCR, western blot and immunofluorescence. Human aortic vascular smooth muscle cells (HAVSMCs) were stimulated with platelet-derived growth factor-BB (PDGF-BB) to establish the cellular model of AD. PTTG1 expression in VSMCs was also examined by qPCR and western blot. Cell viability was detected by CCK-8, cell proliferation by EdU staining and cell migration by wound healing and transwell. Western blot was then performed to assay migration-related proteins. After interference with PTTG1, the levels of smooth muscle pthenotypic switch markers smooth muscle protein 22 alpha (SM22-α) and osteopontin (OPN) were detected by qPCR, western blot and immunofluorescence. The binding of SP1 and PTTG1 was verified with dual-luciferase reporter assay and chromatin immunoprecipitation assay (ChIP). PTTG1 overexpression was found in AD patients. Interference with PTTG1 attenuated the proliferation and migration of PDGF-BB-stimulated HAVSMCs, in addition to their switching from contractile phenotype to synthetic phenotype. Transcription factor SP1 was up-regulated in PDGF-BB-stimulated HAVSMCs, combined with PTTG1 promoter sequence and regulated PTTG1 expression, whose overexpression reversed the effects of PTTG1 interference on cell proliferation, migration and phenotypic switching. SP1 transcriptional activation of PTTG1 activated MAPK/ERK signaling pathway. In conclusion, SP1 transcriptional activation of PTTG1 regulates the migration and phenotypic transformation of HAVSMCs in AD by MAPK Signaling.

Vascular Leakage Prevention by Roundabout 4 under Pathological Conditions

Vascular permeability is regulated mainly by the endothelial barrier and controls vascular homeostasis, proper vessel development, and immune cell trafficking. Several molecules are involved in regulating endothelial barrier function. Roundabout 4 (Robo4) is a single-pass transmembrane protein that is specifically expressed in vascular endothelial cells. Robo4 is an important regulator of vascular leakage and angiogenesis, especially under pathological conditions. The role of Robo4 in preventing vascular leakage has been studied in various disease models, including animal models of retinopathy, tumors, diabetes, and endotoxemia. The involvement of Robo4 in vascular endothelial growth factor and inflammation-mediated signaling pathways has been well studied, and recent evidence suggests that Robo4 modulates endothelial barrier function via distinct mechanisms. In this review, we discuss the role of Robo4 in endothelial barrier function and the underlying molecular mechanisms.

Salidroside Prevents Hypoxia-Induced Human Retinal Microvascular Endothelial Cell Damage Via miR-138/ROBO4 Axis

Purpose

Retinopathies are associated with the injury of retinal microvascular endothelial cells. Salidroside (SAL) is a medicinal supplement that has antioxidative and cytoprotective properties. We hypothesized that SAL might have a protective function in retinopathies. This research aims to explore the function and mechanism of SAL in hypoxia-induced retinal microvascular endothelial cell injury.

Methods

Human retinal microvascular endothelial cells (HRMECs) injury was induced by culturing under hypoxic condition. The function of SAL on HRMECs injury was investigated using cell counting kit-8, 5-ethynyl-2′-deoxyuridine (EdU) staining, flow cytometry, Western blotting, and enzyme linked immunosorbent assay. MicroRNA (miR)-138, roundabout 4 (ROBO4), and proteins in the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathways were examined using quantitative reverse transcription polymerase chain reaction or Western blotting. The target correlation was determined by dual-luciferase reporter analysis and RNA immunoprecipitation.

Results

Hypoxia resulted in proliferation inhibition, cycle arrest, apoptosis, inflammatory reaction, and oxidative stress in HRMECs. SAL attenuated hypoxia-induced HRMECs injury via increasing cell proliferation, and mitigating cycle arrest, apoptosis, inflammatory reaction, and oxidative stress. MiR-138 expression was enhanced by hypoxia, and decreased via SAL stimulation. MiR-138 upregulation reversed the influence of SAL on hypoxia-induced HRMECs injury. ROBO4 was targeted via miR-138. ROBO4 overexpression weakened the role of miR-138 in HRMECs injury. The PI3K/AKT/mTOR pathway was inactivated under hypoxic condition, and SAL increased the activation of PI3K/AKT/mTOR pathways by decreasing miR-138.

Conclusions

SAL protected against hypoxia-induced HRMECs injury through regulating miR-138/ROBO4 axis, indicating the protective potential of SAL in retinopathies.

A novel role of kallikrein-related peptidase 8 in the pathogenesis of diabetic cardiac fibrosis

Rationale: Among all the diabetic complications, diabetic cardiomyopathy, which is characterized by myocyte loss and myocardial fibrosis, is the leading cause of mortality and morbidity in diabetic patients. Tissue kallikrein-related peptidases (KLKs) are secreted serine proteases, that have distinct and overlapping roles in the pathogenesis of cardiovascular diseases. However, whether KLKs are involved in the development of diabetic cardiomyopathy remains unknown.The present study aimed to determine the role of a specific KLK in the initiation of endothelial-to-mesenchymal transition (EndMT) during the pathogenesis of diabetic cardiomyopathy.

Methods and Results-By screening gene expression profiles of KLKs, it was found that KLK8 was highly induced in the myocardium of mice with streptozotocin-induced diabetes. KLK8 deficiency attenuated diabetic cardiac fibrosis, and rescued the impaired cardiac function in diabetic mice. Small interfering RNA (siRNA)-mediated KLK8 knockdown significantly attenuated high glucose-induced endothelial damage and EndMT in human coronary artery endothelial cells (HCAECs). Diabetes-induced endothelial injury and cardiac EndMT were significantly alleviated in KLK8-deficient mice. In addition, transgenic overexpression of KLK8 led to interstitial and perivascular cardiac fibrosis, endothelial injury and EndMT in the heart. Adenovirus-mediated overexpression of KLK8 (Ad-KLK8) resulted in increases in endothelial cell damage, permeability and transforming growth factor (TGF)-β1 release in HCAECs. KLK8 overexpression also induced EndMT in HCAECs, which was alleviated by a TGF-β1-neutralizing antibody. A specificity protein-1 (Sp-1) consensus site was identified in the human KLK8 promoter and was found to mediate the high glucose-induced KLK8 expression. Mechanistically, it was identified that the vascular endothelial (VE)-cadherin/plakoglobin complex may associate with KLK8 in HCAECs. KLK8 cleaved the VE-cadherin extracellular domain, thus promoting plakoglobin nuclear translocation. Plakoglobin was required for KLK8-induced EndMT by cooperating with p53. KLK8 overexpression led to plakoglobin-dependent association of p53 with hypoxia inducible factor (HIF)-1α, which further enhanced the transactivation effect of HIF-1α on the TGF-β1 promoter. KLK8 also induced the binding of p53 with Smad3, subsequently promoting pro-EndMT reprogramming via the TGF-β1/Smad signaling pathway in HCAECs. The in vitro and in vivo findings further demonstrated that high glucose may promote plakoglobin-dependent cooperation of p53 with HIF-1α and Smad3, subsequently increasing the expression of TGF-β1 and the pro-EndMT target genes of the TGF-β1/Smad signaling pathway in a KLK8-dependent manner.

Conclusions: The present findings uncovered a novel pro-EndMT mechanism during the pathogenesis of diabetic cardiac fibrosis via the upregulation of KLK8, and may contribute to the development of future KLK8-based therapeutic strategies for diabetic cardiomyopathy.

Exosomal miR-638 Inhibits Hepatocellular Carcinoma Progression by Targeting SP1

Purpose

Exosomal microRNAs (miRNAs) play essential roles in the development of hepatocellular carcinoma (HCC). Nevertheless, the role and mechanism of exosomal miR-638 in HCC development remain largely unknown.

Methods

Exosomes were isolated and confirmed via transmission electron microscopy and western blot. The abundances of miR-638 and specificity protein 1 (SP1) were measured via quantitative reverse transcription polymerase chain reaction or western blot. Cell proliferation was investigated by Cell Counting Kit-8, colony formation assay, apoptosis, cell cycle distribution and related protein expression. Cell migration and invasion were detected via transwell assay and western blot. Co-culture experiment was performed to assess exosome transfer from HCC cells to endothelial cells. The target correlation between miR-638 and SP1 was analyzed via dual-luciferase reporter and RNA immunoprecipitation assays. The subcutaneous xenograft experiment was conducted to test the function of miR-638 in vivo.

Results

The miR-638 level declined in exosomes from serum or HCC cell medium. miR-638 overexpression repressed HCC cell proliferation by decreasing viability and colony formation and inducing apoptosis and cell cycle arrest at G1 phase, and decreased abilities of migration and invasion. Exosomal miR-638 from HCC cells could transfer to human umbilical vein endothelial cells (HUVECs) and suppress HUVEC proliferation, migration and invasion. SP1 was a target of miR-638 and overexpression of SP1 reversed the effect of miR-638 on HCC cells. Overexpression of miR-638 reduced xenograft tumor growth via decreasing SP1.

Conclusion

Exosomal miR-638 inhibited HCC tumorigenesis by targeting SP1. This study indicated the potential clinical implications of miR-638 in HCC.

O-GlcNAcylation Mediates Glucose-Induced Alterations in Endothelial Cell Phenotype in Human Diabetes Mellitus

Background Posttranslational protein modification with O-linked N-acetylglucosamine (O-GlcNAc) is linked to high glucose levels in type 2 diabetes mellitus (T2DM) and may alter cellular function. We sought to elucidate the involvement of O-GlcNAc modification in endothelial dysfunction in patients with T2DM. Methods and Results Freshly isolated endothelial cells obtained by J-wire biopsy from a forearm vein of patients with T2DM (n=18) was compared with controls (n=10). Endothelial O-GlcNAc levels were 1.8-ford higher in T2DM patients than in nondiabetic controls (P=0.003). Higher endothelial O-GlcNAc levels correlated with serum fasting blood glucose level (r=0.433, P=0.024) and hemoglobin A1c (r=0.418, P=0.042). In endothelial cells from patients with T2DM, normal glucose conditions (24 hours at 5 mmol/L) lowered O-GlcNAc levels and restored insulin-mediated activation of endothelial nitric oxide synthase, whereas high glucose conditions (30 mmol/L) maintained both O-GlcNAc levels and impaired insulin action. Treatment of endothelial cells with Thiamet G, an O-GlcNAcase inhibitor, increased O-GlcNAc levels and blunted the improvement of insulin-mediated endothelial nitric oxide synthase phosphorylation by glucose normalization. Conclusions Taken together, our findings indicate a role for O-GlcNAc modification in the dynamic, glucose-induced impairment of endothelial nitric oxide synthase activation in endothelial cells from patients with T2DM. O-GlcNAc protein modification may be a treatment target for vascular dysfunction in T2DM.

Robo4-mediated pancreatic endothelial integrity decreases inflammation and islet destruction in autoimmune diabetes

In Type 1 Diabetes Mellitus (T1DM), leukocyte infiltration of the pancreatic islets and the resulting immune-mediated destruction of beta cells precede hyperglycemia and clinical disease symptoms. In this context, the role of the pancreatic endothelium as a barrier for autoimmunity- and inflammation-related destruction of the islets is not well studied. Here, we identified Robo4, expressed on endothelial cells, as a regulator of pancreatic vascular endothelial permeability during autoimmune diabetes. Circulating levels of Robo4 were upregulated in mice subjected to the Multiple Low-Dose Streptozotocin (MLDS) model of diabetes. Upon MLDS induction, Robo4-deficiency resulted in increased pancreatic vascular permeability, leukocyte infiltration to the islets and islet apoptosis, associated with reduced insulin levels and faster diabetes development. On the contrary, in vivo administration of Slit2 in mice modestly delayed the emergence of hyperglycaemia and ameliorated islet inflammation in MLDS-induced diabetes. Thus, Robo4-mediated endothelial barrier integrity reduces insulitis and islet destruction in autoimmune diabetes. Our findings highlight the importance of the endothelium as gatekeeper of pancreatic inflammation during T1DM development and may pave the way for novel Robo4-related therapeutic approaches for autoimmune diabetes.

Immune Mediated Degeneration and Possible Protection in Glaucoma

The underlying pathomechanisms for glaucoma, one of the most common causes of blindness worldwide, are still not identified. In addition to increased intraocular pressure (IOP), oxidative stress, excitotoxicity, and immunological processes seem to play a role. Several pharmacological or molecular/genetic methods are currently investigated as treatment options for this disease. Altered autoantibody levels were detected in serum, aqueous humor, and tissue sections of glaucoma patients. To further analyze the role of the immune system, an IOP-independent, experimental autoimmune glaucoma (EAG) animal model was developed. In this model, immunization with ocular antigens leads to antibody depositions, misdirected T-cells, retinal ganglion cell death and degeneration of the optic nerve, similar to glaucomatous degeneration in patients. Moreover, an activation of the complement system and microglia alterations were identified in the EAG as well as in ocular hypertension models. The inhibition of these factors can alleviate degeneration in glaucoma models with and without high IOP. Currently, several neuroprotective approaches are tested in distinct models. It is necessary to have systems that cover underlying pathomechanisms, but also allow for the screening of new drugs. In vitro models are commonly used, including single cell lines, mixed-cultures, and even organoids. In ex vivo organ cultures, pathomechanisms as well as therapeutics can be investigated in the whole retina. Furthermore, animal models reveal insights in the in vivo situation. With all these models, several possible new drugs and therapy strategies were tested in the last years. For example, hypothermia treatment, neurotrophic factors or the blockage of excitotoxity. However, further studies are required to reveal the pressure independent pathomechanisms behind glaucoma. There is still an open issue whether immune mechanisms directly or indirectly trigger cell death pathways. Hence, it might be an imbalance between protective and destructive immune mechanisms. Moreover, identified therapy options have to be evaluated in more detail, since deeper insights could lead to better treatment options for glaucoma patients.

Inhibitor of growth 4 affects hypoxia-induced migration and angiogenesis regulation in retinal pigment epithelial cells

Inhibitor of growth 4 (ING4), a potential tumor suppressor, is implicated in cell migration and angiogenesis. However, its effects on diabetic retinopathy (DR) have not been elucidated. In this study, we aimed to evaluate ING4 expression in normal and diabetic rats and clarify its effects on hypoxia-induced dysfunction in human retinal pigment epithelial (ARPE-19) cells. A Type 1 diabetic model was generated by injecting rats intraperitoneally with streptozotocin and then killed them 4, 8, or 12 weeks later. ING4 expression in retinal tissue was detected using western blot analysis, reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR), and immunohistochemistry assays. After transfection with an ING4 overexpression lentiviral vector or small interfering RNA (siRNA), ARPE-19 migration under hypoxia was tested using wound healing and transwell assays. The angiogenic effect of conditioned medium (CM) from ARPE-19 cells was examined by assessing human retinal endothelial cell (HREC) capillary tube formation. Additionally, western blot analysis and RT-qPCR were performed to investigate the signaling pathways in which ING4, specificity protein 1 (Sp1), matrix metalloproteinase 2 (MMP-2), MMP-9, and vascular endothelial growth factor A (VEGF-A) were involved. Here, we found that ING4 expression was significantly reduced in the diabetic rats' retinal tissue. Silencing ING4 aggravated hypoxia-induced ARPE-19 cell migration. CM collected from ING4 siRNA-transfected ARPE-19 cells under hypoxia promoted HREC angiogenesis. These effects were reversed by ING4 overexpression. Furthermore, ING4 suppressed MMP-2, MMP-9, and VEGF-A expression in an Sp1-dependent manner in hypoxia-conditioned ARPE-19 cells. Overall, our results provide valuable mechanistic insights into the protective effects of ING4 on hypoxia-induced migration and angiogenesis regulation in ARPE-19 cells. Restoring ING4 may be a novel strategy for treating DR.

Regulatory mechanisms of Robo4 and their effects on angiogenesis

Roundabout4 (Robo4) is a transmembrane receptor that belongs to the Roundabout (Robo) family of axon guidance molecules. Robo4 is an endothelial-specific receptor that participates in endothelial cell migration, proliferation, and angiogenesis and the maintenance of vasculature homeostasis. The purpose of this review is to summarize and analyze three main mechanisms related to the expression and function of Robo4 during developmental and pathological angiogenesis. In this review, static shear stress and the binding of transcription factors such as E26 transformation-specific variant 2 (ETV2) and Slit3 induce Robo4 expression and activate Robo4 during tissue and organ development. Robo4 interacts with Slit2 or UNC5B to maintain vascular integrity, while a disturbed flow and the expression of transcription factors in inflammatory or neoplastic environments alter Robo4 expression levels, although these changes have uncertain functions. Based on the mechanisms described above, we discuss the aberrant expression of Robo4 in angiogenesis-related diseases and propose antiangiogenic therapies targeting the Robo4 signaling pathway for the treatment of ocular neovascularization lesions and tumors. Finally, although many problems related to Robo4 signaling pathways remain to be resolved, Robo4 is a promising and potentially valuable therapeutic target for treating pathological angiogenesis and developmental defects in angiogenesis.

Enhanced ROBO4 is mediated by up-regulation of HIF-1α/SP1 or reduction in miR-125b-5p/miR-146a-5p in diabetic retinopathy

Retinal cell damage caused by diabetes leads to retinal microvascular injury. Roundabout 4 (ROBO4) is involved in angiogenesis, which varies with the development of diabetic retinopathy (DR). Here, we explored the transcriptional regulation and microRNA‐mediated modulation of ROBO4 expression and related retinal cell function in DR. A streptozotocin‐induced type I diabetic animal model was established to detect the expression of hypoxia inducible factor‐1α (HIF‐1α), specificity protein 1 (SP1) and ROBO4. Retinal pigment epithelium (RPE) cells were cultured under hyperglycaemia or hypoxia and used for mechanistic analysis. Furthermore, roles of miR‐125b‐5p and miR‐146a‐5p were evaluated, and their targets were identified using luciferase assays. The cell functions were evaluated by MTS assays, permeability analysis and migration assays. The development of DR increased the levels of HIF‐1α, SP1 and ROBO4 both in the DR model and in hyperglycaemic/hypoxic RPE cells. They were co‐expressed and up‐regulated in diabetic retinas and in RPE cells under hyperglycaemia/hypoxia. Knockdown of HIF‐1α significantly inhibited SP1 and ROBO4, whereas SP1 down‐regulation abolished ROBO4 expression in RPE cells under hyperglycaemia/hypoxia. miR‐125b‐5p and miR‐146a‐5p were down‐regulated by hyperglycaemia and/or hypoxia. Up‐regulation of miRNAs reversed these changes and resulted in recovery of target gene expression. Moreover, luciferase assays confirmed miR‐125b‐5p targeted SP1 and ROBO4, and miR‐146a‐5p targeted HIF‐1α and ROBO4 directly. The decreased cell viability, enhanced permeability, and increased cell migration under DR conditions were mitigated by knockdown of HIF‐1α/SP1/ROBO4 or up‐regulation of miR‐125b‐5p/miR‐146a‐5p. In general, our results identified a novel mechanism that miR‐125b‐5p/miR‐146a‐5p targeting HIF‐1α/SP1‐dependent ROBO4 expression could retard DR progression.

Models of retinal diseases and their applicability in drug discovery

INTRODUCTION

The impact of vision debilitating diseases is a global public health concern, which will continue until effective preventative and management protocols are developed. Two retinal diseases responsible for the majority of vision loss in the working age adults and elderly populations are diabetic retinopathy (DR) and age-related macular degeneration (AMD), respectively. Model systems, which recapitulate aspects of human pathology, are valid experimental modalities that have contributed to the identification of signaling pathways involved in disease development and consequently potential therapies. Areas covered: The pathology of DR and AMD, which serve as the basis for designing appropriate models of disease, is discussed. The authors also review in vitro and in vivo models of DR and AMD and evaluate the utility of these models in exploratory and pre-clinical studies. Expert opinion: The complex nature of non-Mendelian diseases such as DR and AMD has made identification of effective therapeutic treatments challenging. However, the authors believe that while in vivo models are often criticized for not being a 'perfect' recapitulation of disease, they have been valuable experimentally when used with consideration of the strengths and limitations of the experimental model selected and have a place in the drug discovery process.

Sodium-glucose transporter as a novel therapeutic target in disease

Glucose is the primary energy fuel of life. A glucose transporter, the sodium-glucose transporter (SGLT), is receiving attention as a novel therapeutic target in disease. This review summarizes the physiological role of SGLT in cerebral ischemia, cancer, cardiac disease, and intestinal ischemia, which has encouraged analysis of SGLT function. In cerebral ischemia and cardiomyopathy, SGLT-1 is involved in worsening of the injury. In addition, SGLT-1 promotes the development of cancer. On the other hand, SGLT-1 has a protective effect against cardiac and intestinal ischemia. Interestingly, SGLT-1 expression levels are increased in some diseased tissue, such as in cerebral ischemia and cancer. This suggests that SGLT-1 may have an important role in many diseases. This review discusses the potential of SGLT as a target for novel therapeutic agents.

A Critical Analysis of the Available In Vitro and Ex Vivo Methods to Study Retinal Angiogenesis

Angiogenesis is a biological process with a central role in retinal diseases. The choice of the ideal method to study angiogenesis, particularly in the retina, remains a problem. Angiogenesis can be assessed through in vitro and in vivo studies. In spite of inherent limitations, in vitro studies are faster, easier to perform and quantify, and typically less expensive and allow the study of isolated angiogenesis steps. We performed a systematic review of PubMed searching for original articles that applied in vitro or ex vivo angiogenic retinal assays until May 2017, presenting the available assays and discussing their applicability, advantages, and disadvantages. Most of the studies evaluated migration, proliferation, and tube formation of endothelial cells in response to inhibitory or stimulatory compounds. Other aspects of angiogenesis were studied by assessing cell permeability, adhesion, or apoptosis, as well as by implementing organotypic models of the retina. Emphasis is placed on how the methods are applied and how they can contribute to retinal angiogenesis comprehension. We also discuss how to choose the best cell culture to implement these methods. When applied together, in vitro and ex vivo studies constitute a powerful tool to improve retinal angiogenesis knowledge. This review provides support for researchers to better select the most suitable protocols in this field.