Retinopathy of prematurity (ROP) is a vision-threatening disorder that leads to pathological growth of the retinal vasculature due to hypoxia. Here, we investigated the potential effects of alamandine, a novel heptapeptide in the renin-angiotensin system (RAS), on hypoxia-induced retinal neovascularization and its underlying mechanisms. In vivo, the C57BL/6J mice with oxygen-induced retinopathy (OIR) were injected intravitreally with alamandine (1.0 μmol/kg per eye). In vitro, human retinal microvascular endothelial cells (HRMECs) were utilized to investigate the effects of alamandine (10 μg/mL) on proliferation, apoptosis, migration, and tubular formation under vascular endothelial growth factor (VEGF) stimulation. Single-cell RNA sequencing (scRNA-seq) matrix data from the Gene Expression Omnibus (GEO) database and RAS-related genes from the Molecular Signatures Database (MSigDB) were sourced for subsequent analyses. By integrating scRNA-seq data across multiple species, we identified that RAS-associated endothelial cell populations were highly related to retinal neovascularization. The liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis revealed a significant decrease in alamandine levels in both the serum and retina of OIR mice compared to those in the control group. Next, alamandine ameliorated hypoxia-induced retinal pathological neovascularization and physiologic revascularization in OIR mice. In vitro, alamandine effectively mitigated VEGF-induced proliferation, scratch wound healing, and tube formation of HRMECs primarily by inhibiting the hypoxia-inducible factor-1α (HIF-1α)/VEGF pathway. Further, coincubation with D-Pro⁷ (Mas-related G protein-coupled receptor D (MrgD) antagonist) hindered the beneficial impacts of alamandine on hypoxia-induced pathological angiogenesis both in vivo and in vitro. Our findings suggested that alamandine could mitigate retinal neovascularization by targeting the MrgD-mediated HIF-1α/VEGF pathway, providing a potential therapeutic agent for OIR prevention and treatment.
Animals ; Retinal Neovascularization/prevention & control* ; Mice, Inbred C57BL ; Vascular Endothelial Growth Factor A/metabolism* ; Humans ; Mice ; Hypoxia-Inducible Factor 1, alpha Subunit/metabolism* ; Oligopeptides/therapeutic use* ; Signal Transduction/drug effects* ; Cell Proliferation/drug effects* ; Endothelial Cells/drug effects* ; Retinopathy of Prematurity/drug therapy* ; Apoptosis/drug effects* ; Cell Movement/drug effects* ; Renin-Angiotensin System/drug effects* ; Cells, Cultured

OBJECTIVETo explore the effects of rat bone mesenchymal stem cell (BMSC) transplantation on retinal neovascularization, and to observe the changes of hypoxia-inducible factor-1 alpha (HIF-1α) and vascular endothelial growth factors (VEGF) in rats with oxygen-induced retinopathy (OIR).

METHODSSeventy-two seven-day-old Sprague-Dawley rats were randomly divided into three groups: normal control (CON), model (OIR) and BMSC transplantation. In the BMSC transplantation group, BMSCs were transplanted 5 days after oxygen conditioning. The phosphate buffered saline of the same volume was injected in the CON and OIR groups. The OIR model was prerpared according to the classic hyperoxygen method. At seven days after transplantation, retinal neovascularization was examined by retinal flat-mount staining and hematoxylin eosin (HE) staining. The expression of HIF-1α and VEGF proteins was examined by immunohistochemistry staining and Western blot analysis.

RESULTSThe retinal flat-mount staining results showed that the vessels were well organized in the CON group, but the vessels were irregularly organized, and lots of nonperfusion areas were observed in the OIR group. The large vessels were a bit circuitous, the retinal vessels were relatively organized, and less nonperfusion areas were noted in the BMSC transplantation group. The HE staining results showed that many neovessels and preretinal neovascular (pre-RNC) cells were observed on the internal limiting membrane in the OIR group. There were less pre-RNC cells in the BMSC transplantation group compared with the OIR group (P<0.01). The immunohistochemistry analysis showed that more HIF-1αand VEGFcells were observed in the OIR group compared with the CON group, and less HIF-1αand VEGFcells were observed in the BMSC transplantation group compared with OIR group (P<0.05). The Western blot analysis showed the expression of HIF-1α and VEGF proteins in the OIR group was significantly higher than that in the CON group. The expression of HIF-1α and VEGF proteins in the BMSC transplantation group was lower than that in the OIR group (P<0.01).

CONCLUSIONSBMSC transplantation therapy could alleviate retinal neovascularization in OIR rats, and its mechanisms might be associated with the inhibition of the expression of HIF-1α and VEGF proteins.

Animals ; Animals, Newborn ; Female ; Hypoxia-Inducible Factor 1, alpha Subunit ; analysis ; Male ; Mesenchymal Stem Cell Transplantation ; Rats ; Rats, Sprague-Dawley ; Retina ; chemistry ; Retinal Neovascularization ; prevention & control ; Retinopathy of Prematurity ; metabolism ; therapy ; Vascular Endothelial Growth Factor A ; analysis

BACKGROUNDThe mechanisms of pathological retinal neovascularization (RNV) remain unknown. Several microRNAs were reported to be involved in the process of RNV. Oxygen-induced retinopathy (OIR) is a useful model to investigate RNV. Our present work explored the expression and the role of microRNA-128 (miR-218) in oxygen-induced RNV.

METHODSOIR was used to establish RNV model. The expression level of miR-218 in the retina from OIR mice was assessed by quantitative real-time reverse transcriptase polymerase chain reaction. Fluorescein angiography was performed in retinae of OIR mice, and RNV was quantified by hematoxylin and eosin staining to evaluate the effect of pCDH-CMV-miR-218 intravitreal injection on RNV in OIR mice. Roundabout 1 (Robo1) expression was detected by Western blotting in mouse retinal vascular endothelial cells expressing a high or low level of miR-218 and retinal tissues from OIR mice. Cell migration was evaluated by scratch wound assay.

RESULTSIn OIR mice, the expression level of miR-218 was significantly down-regulated (P = 0.006). Retinal Robo1 expression was significantly increased at both mRNA and protein levels (P = 0.001, 0.008; respectively). miR-218 intravitreal injection inhibited retinal angiogenesis in OIR mice, and the restoration of miR-218 in retina led to down-regulation of Robo1.

CONCLUSIONSOur experiments showed that restoration of miR-218 inhibited retinal angiogenesis via targeting Robo1. MiR-218 contributed to the inhibition of retinal angiogenesis and miR-218 might be a new therapeutic target for preventing RNV.

Animals ; Cell Movement ; Cells, Cultured ; Mice ; Mice, Inbred C57BL ; MicroRNAs ; physiology ; Nerve Tissue Proteins ; physiology ; Oxygen ; pharmacology ; Receptors, Immunologic ; physiology ; Retinal Neovascularization ; prevention & control

OBJECTIVETo investigate whether propranolol application as collyrium or intraperitoneal (IP) injection can promote the recovery of oxygen-induced retinopathy (OIR).

METHODThirty-six 7-day-old mice were divided into the following 6 groups: normal control, propranolol eye drops, propranolol IP injection, eye drops negative control, IP injection negative control, and pathological model with 6 mice in each. In a typical model of OIR, litters of mice pups with their nursing mothers were exposed to an infant incubator to high oxygen concentration (75 ± 5)% between postnatal day (PD) 7 and PD12, prior to returning to room air. Two routes of propranolol treatment were assessed from PD12 to PD17: IP injection and eye drop, with doses 2 mg/(kg·time), three times a day. Another three groups were given citric acid buffer eye drops, IP injection of citric acid buffer, and negative control were not treated with any drug. Neonatal mice fed in normal conditions served as normal control. Mice were sacrificed at PD17 to evaluate the morphological changes of retinal vessels by fluorescein isothiocyanate-dextran perfusion and retinal whole mount. The retinal neovascularization was evaluated by counting the number of nuclei of the endothelial cell breaking through the internal limiting membrane (ILM).

RESULTCompared with the oxygen-exposed group, the branches of retinal vessels went normal with a less un-perfused area in the propranolol eye drops and propranolol IP injection groups [(38.9 ± 9.9)% and (5.6 ± 2.3)% vs. (16.2 ± 10.0)% and (2.2 ± 0.8)%, (25.9 ± 5.0)% and (2.1 ± 2.7)%, F=36.12 and 14.55, P both<0.001]. The number of nuclei of endothelial cells breaking through the ILM on the retinal cross-section in the propranolol eye drops group decreased (14.2 ± 5.1) per slide, which was less than that in the oxygen-exposed group (49.1 ± 8.9) per slide and the propranolol IP injection group (18.0 ± 5.9) per slide; it was also less than that in the eye drops negative control group (47.4 ± 8.1) per slide (F=187.60, P<0.05). Moreover, the number of nuclei of endothelial cells breaking through the ILM on the retinal cross-section in the propranolol IP injection group was less than that in the IP injection negative control group (49.9 ± 7.1) per slide (P<0.05).

CONCLUSIONPropranolol could effectively inhibit the formation of retinal neovascularization in mice; the eye drops was more effective than the IP injection.

Animals ; Dextrans ; Disease Models, Animal ; Endothelial Cells ; Fluorescein-5-isothiocyanate ; analogs & derivatives ; Injections, Intraperitoneal ; Mice ; Ophthalmic Solutions ; Oxygen ; adverse effects ; Propranolol ; therapeutic use ; Retina ; drug effects ; Retinal Neovascularization ; chemically induced ; drug therapy ; prevention & control ; Retinal Vessels ; drug effects

BACKGROUNDRetinopathy of prematurity (ROP) has become one of the leading causes of visual loss in children. Vascular endothelial growth factor A (VEGF-A) is the principal stimulator of angiogenesis. VEGF was differentially spliced from exon 8 to exons 8a and 8b to form two families: the pro-angiogenic VEGFxxx family and the anti-angiogenic VEGFxxxb family. Previous research has shown variable effeteness of bevacizumab in inhibiting retinal neovascularization in ROP. This study aimed to investigate whether the effectiveness of this inhibition depends on the relative ratio of the two VEGF isoforms.

METHODSIntravitreal bevacizumab injection (IVB) was performed in the oxygen-induced-retinopathy (OIR) mice on postnatal day 12 (P12) (intravitreal phosphate buffered saline (PBS) injection as control). The Evans blue perfused retina were used to test the retinal neovascularization-leakage (NVL) area and non-perfusion (NP) area.

RESULTSThe retinal NVL and NP area in the IVB group were significantly smaller than the intravitreal PBS injection group (IVP group). On P17, the protein level of total VEGF isoforms was significantly inhibited compared to IVP group (P < 0.05) while VEGF(165)b isoform was slight reduced (P > 0.05). The switch from pro-angiogenic isoforms to anti-angiogenic isoforms after IVB could be found. The relative protein expression of VEGF(165)b isoform was significantly higher in IVB group than in IVP group (P < 0.05) on P17 which was correlated with the reduced ischemia-induced angiogenesis in OIR mice after IVB.

CONCLUSIONSThe anti-angiogenic effectiveness might depend on the relative high expression of VEGF(165)b after intravitreal bevacizumab injection. Anti-angiogenic therapy is a more effective therapy for ROP.

Angiogenesis Inhibitors ; administration & dosage ; Animals ; Animals, Newborn ; Antibodies, Monoclonal, Humanized ; administration & dosage ; Bevacizumab ; Disease Models, Animal ; Intravitreal Injections ; Mice ; Mice, Inbred C57BL ; Protein Isoforms ; analysis ; Retinal Neovascularization ; prevention & control ; Retinopathy of Prematurity ; drug therapy ; Vascular Endothelial Growth Factor A ; analysis

OBJECTIVETo study the inhibition effect of HIF-1α specific siRNA expression vector pSUPERH1-siHIF-1α on retinal neovascularization in a mouse model of retinopathy of prematurity (ROP).

METHODSThe mouse model of ROP was prepared by the method Smith described. Forty-eight ROP mice were randomly divided into two groups: an experimental group that was intravitreously injected with pSUPERH1-siHIF-1α and a control group that was injected with pSUPER retro vector. The levels of HIF-1α and vascular endothelia growth factor (VEGF) in the retina were examined by Western blot. The retinal neovascularization was evaluated by angiography using FITC Dextran and quantitated histologically.

RESULTSThe levels of HIF-1α and VEGF in the retina in the experimental group were reduced 90% and 65% respectively compared with those in the control group. Meanwhile, the number of retinal neovascular endothelial nucleus outbreaking the inner limit membrane in the experimental group was significantly reduced compared with that in the control group.

CONCLUSIONSThe development of retinal neovascularization of ROP can be markedly inhibited by RNA interference targeting HIF-1α.

Animals ; Disease Models, Animal ; Humans ; Hypoxia-Inducible Factor 1, alpha Subunit ; analysis ; antagonists & inhibitors ; genetics ; Infant, Newborn ; Mice ; Mice, Inbred C57BL ; RNA, Small Interfering ; genetics ; Retinal Neovascularization ; prevention & control ; Retinopathy of Prematurity ; therapy ; Vascular Endothelial Growth Factor A ; analysis