ICAM-1 depletion does not alter retinal vascular development in a model of oxygen-mediated neovascularization

Induced pluripotent stem cells can improve thrombolytic effect of low-dose rt-PA after acute carotid thrombosis in rat

Background

Intravenous thrombolysis using recombinant tissue plasminogen activator (rt-PA) is the standard treatment for acute ischemic stroke. Standard-dose rt-PA (0.9 mg/kg) is known to achieve good recanalization but carries a high bleeding risk. Lower dose of rt-PA has less bleeding risk but carries a high re-occlusion rate. We investigate if induced pluripotent stem cells (iPSCs) can improve the thrombolytic effect of low-dose rt-PA (0.45 mg/kg).

Methods

Single irradiation with 6 mW/cm² light-emitting diode (LED) for 4 h at rat common carotid artery was used as thrombosis model according to our previous report. Endothelin-1 (ET-1), intercellular adhesion molecule-1 (ICAM-1), and interleukin 1 beta (IL-1 beta) were used as the inflammatory markers for artery endothelial injury. Angiopoietin-2 (AP-2), brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) were examined in artery wall and iPSCs culture. Animal ultrasound was used to evaluate the stenosis degree of common carotid artery before and at 2 h, 24 h, 4 days and 7 days after LED irradiation.

Results

After LED irradiation alone, there was a persistent occlusion from 2 h to 7 days. Standard-dose rt-PA alone could recanalize the occluded artery from 24 h to 7 days to stenotic degree ≤ 50%. Low-dose rt-PA or 1 × 10⁶ mouse iPSCs alone could not recanalize the occluded arteries from 2 h to 7 days. Combination use of low-dose rt-PA plus 1 × 10⁶ mouse iPSCs caused better recanalization from 24 h to 7 days. ET-1, ICAM-1 and IL-1 beta were strongly expressed after LED irradiation but reduced after iPSCs treatment. AP-2, BDNF and VEGF were rarely induced after LED irradiation but strongly expressed after iPSCs treatment. In vitro study showed iPSCs could express AP-2, BDNF and VEGF.

Conclusion

The adjuvant use of iPSCs may help improving the thrombolytic effect of low-dose rt-PA by suppressing inflammatory factors and inducing angiogenic trophic factors. Stem cells could be a potential regimen in acute thrombolytic therapy to improve recanalization and reduce complications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02615-z.

Systemic Rho-kinase inhibition using fasudil in mice with oxygen-induced retinopathy

PURPOSE

To investigate the influence of the selective Rho-kinase (ROCK) inhibitor, fasudil, on the mRNA level of proinflammatory factors and the retinal vascular development in mice with oxygen-induced retinopathy (OIR).

METHODS

C57BL/6J mice underwent standard protocol for OIR induction from postnatal days 7 to 12. Subsequently, they received a daily intraperitoneal injection of fasudil or sodium chloride from P12 to P16. Analyses were performed using vascular staining on retinal flat mounts, RNA expression by qPCR, and immunohistochemistry on paraffin sections.

RESULTS

On retinal flat mounts, the proportion of avascular area and tuft formation did not differ between the fasudil and NaCl group. Immunohistochemical staining revealed a less intense staining with inflammatory markers after fasudil. Nevertheless, there were no differences on RNA level between the two groups.

CONCLUSIONS

In conclusion, our findings support that daily systemic application of fasudil does not decrease retinal neovascularization in rodents with oxygen-induced retinopathy. The results of our study together with the controversial results on the effects of different ROCK inhibitors from the literature makes it apparent that effects of ROCK inhibition are more complex, and further studies are necessary to analyze its potential therapeutic effects.

Local partial depletion of CD11b+ cells and their influence on choroidal neovascularization using the CD11b-HSVTK mouse model

PURPOSE

To assess the influence of retinal macrophages and microglia on the formation of choroidal neovascularization (CNV). Therefore, we used a transgenic mouse (CD11b-HSVTK) in which the application of ganciclovir (GCV) results in a depletion of CD11b⁺ cells.

METHODS

We first investigated if a local depletion of CD11b⁺ macrophages and microglia in the retina is feasible. In a second step, the influence of CD11b⁺ cell depletion on CNV formation was analysed. One eye of each CD11b-HSVTK mouse was injected with GCV, and the fellow eye received sodium chloride solution (NaCl). Cell counting was performed at day 3 and 7 (one injection) or at day 14 and 21 (two injections). Choroidal neovascularization (CNV) was induced by argon laser and analysed at day 14.

RESULTS

The most effective CD11b⁺ cell depletion was achieved 7 days after a single injection and 14 days after two injections of GCV. After two injections of GCV, we found a significant reduction of CD11b⁺ cells in central (52 ± 23.9 cells/mm² ) and peripheral retina (53 ± 20.6 cells/mm² ); compared to eyes received NaCl (216 ± 49.0 and 210 ± 50.5 cells/mm² , p < 0.001, respectively). Regarding CNV areas, no statistical significance was found between the groups.

CONCLUSION

The CD11b-HSVTK mouse is a feasible model for a local depletion of CD11b⁺ cells in the retina. Nevertheless, only a partial depletion of CD11b⁺ cells could be achieved compared to baseline data without any intravitreal injections. Our results did not reveal a significant reduction in CNV areas. In the light of previous knowledge, the potential influence of systemic immune cells on CNV formation might be more relevant than expected.

Intravitreal inhibition of complement C5a reduces choroidal neovascularization in mice

PURPOSE

To investigate the influence of complement component C5a inhibition on laser-induced choroidal neovascularization (CNV) in mice using a C5a specific L-aptamer.

METHODS

In C57BL/6 J mice CNV was induced by argon-laser, C5a-inhibitor (NOX-D20) was intravitreally injected in three concentrations: 0.3, 3.0, and 30 mg/ml. The unPEGylated derivate (NOX-D20001) was applied at 3.0 mg/ml; the vehicle (5 % glucose) was injected in controls. Vascular leakage was evaluated using fluorescence angiography, CNV area was examined immunohistochemically. Activated immune cells surrounding the CNV lesion and potential cytotoxicity were analyzed.

RESULTS

Compared to controls, CNV areas were significantly reduced after NOX-D20 injection at a concentration of 0.3 and 3.0 mg/ml (p = 0.042; p = 0.016). NOX-D20001 significantly decreased CNV leakage but not the area (p = 0.007; p = 0.276). At a concentration of 30 mg/ml, NOX-D20 did not reveal significant effects on vascular leakage or CNV area (p = 0.624; p = 0.121). The amount of CD11b positive cells was significantly reduced after treatment with 0.3 and 3.0 mg/ml NOX-D20 (p = 0.027; p = 0.002). No adverse glial cell proliferation or increased apoptosis were observed at effective dosages.

CONCLUSIONS

Our findings demonstrate that the targeted inhibition of complement component C5a reduces vascular leakage and neovascular area in laser-induced CNV in mice. NOX-D20 was proven to be an effective and safe agent that might be considered as a therapeutic candidate for CNV treatment. The deficiency of activated immune cells highlights promising new aspects in the pathology of choroidal neovascularization, and warrants further investigations.

Role of the retinal vascular endothelial cell in ocular disease

Retinal endothelial cells line the arborizing microvasculature that supplies and drains the neural retina. The anatomical and physiological characteristics of these endothelial cells are consistent with nutritional requirements and protection of a tissue critical to vision. On the one hand, the endothelium must ensure the supply of oxygen and other nutrients to the metabolically active retina, and allow access to circulating cells that maintain the vasculature or survey the retina for the presence of potential pathogens. On the other hand, the endothelium contributes to the blood-retinal barrier that protects the retina by excluding circulating molecular toxins, microorganisms, and pro-inflammatory leukocytes. Features required to fulfill these functions may also predispose to disease processes, such as retinal vascular leakage and neovascularization, and trafficking of microbes and inflammatory cells. Thus, the retinal endothelial cell is a key participant in retinal ischemic vasculopathies that include diabetic retinopathy and retinopathy of prematurity, and retinal inflammation or infection, as occurs in posterior uveitis. Using gene expression and proteomic profiling, it has been possible to explore the molecular phenotype of the human retinal endothelial cell and contribute to understanding of the pathogenesis of these diseases. In addition to providing support for the involvement of well-characterized endothelial molecules, profiling has the power to identify new players in retinal pathologies. Findings may have implications for the design of new biological therapies. Additional progress in this field is anticipated as other technologies, including epigenetic profiling methods, whole transcriptome shotgun sequencing, and metabolomics, are used to study the human retinal endothelial cell.

Usefulness of the vitreous fluid analysis in the translational research of diabetic retinopathy

Diabetic retinopathy (DR) is the major cause of acquired blindness in working-age adults. Current treatments for DR (laser photocoagulation, intravitreal corticosteroids, intravitreal antivascular endothelial growth factor (VEGF) agents, and vitreo-retinal surgery) are applicable only at advanced stages of the disease and are associated with significant adverse effects. Therefore, new pharmacological treatments for the early stages of the disease are needed. Vitreous fluid obtained from diabetic patients undergoing vitreoretinal surgery is currently used to explore the events that are taking place in the retina for clinical research. However, several confounding factors such as vitreous haemorrhage and concentration of vitreous proteins should be considered in the analysis of the results. In this paper we will focus on the vitreous fluid as a tool for exploring the mediators of DR and in particular the molecules related to inflammatory pathways. In addition, their role in the pathogenesis of DR will be discussed. The usefulness of new technologies such as flow cytometry and proteomics in identifying new candidates involved in the inflammatory process that occurs in DR will be overviewed. Finally, a more personalized treatment based on vitreous fluid analysis aiming to reduce the burden associated with DR is suggested.

Leukocyte adhesion molecules in diabetic retinopathy

Diabetes is a systemic disease that causes a number of metabolic and physiologic abnormalities. One of the major microvascular complications of diabetes is diabetic retinopathy (DR), a leading cause of blindness in people over age 50. The mechanisms underlying the development of DR are not fully understood; however, extensive studies have recently implicated chronic, low-grade inflammation in the pathophysiology of DR. During inflammation leukocytes undergo sequential adhesive interactions with endothelial cells to migrate into the inflamed tissues, a process known as the “leukocyte recruitment cascade” which is orchestrated by precise adhesion molecule expression on the cell surface of leukocytes and the endothelium. This paper summarizes the recent clinical and preclinical works on the roles of leukocyte adhesion molecules in DR.

Selective inner retinal dysfunction in growth hormone transgenic mice

OBJECTIVE

The discovery of locally produced growth hormone (GH) and its receptor in the retina of rodents raises the possibility that GH might modulate retinal function. To test this hypothesis, we determined the retinal electroretinogram (ERG) of bovine GH (bGH) transgenic mice.

DESIGN

ERGs were recorded from 11 wild type (WT) and 9 bGH mice, at 2 months of age in response to a series of light flashes at increasing intensity. Three ERG components were assessed for their amplitude and timing: a-wave, b-wave and oscillatory potentials (OPs). OPs were isolated with a 75-300 Hz digital filter. Retina layer sizes, nuclei number and vascularization were assessed by respectively staining cross sections with DAPI and Bandeiraea simplicifolia.

RESULTS

OPs were selectively affected in the bGH mouse compared to WT. When OP amplitude values were normalized to the a-wave amplitude (to account for inter-animal variability in WT and bGH groups), OP2, OP3, and OP4 showed amplitude reductions (of 65%, 72%, and 68%, respectively) in the bGH mouse compared to the WT. This was accompanied by a prolongation of the implicit time for the peak of OP3 (28.1 vs 31.1 ms, WT vs bGH) and OP4 (37.8 vs 41.6 ms), while the implicit time of a- and b-waves were unaffected. Fast Fourier transform analysis revealed that the OPs' dominant frequency was significantly reduced (P<0.05) in the bGH mice (100 Hz) compared to WT (108Hz). There was no significant change in retinal histology except for a significant increase in the axial length of the eye in bGH mice.

CONCLUSIONS

Mice expressing bGH display a selective inner retinal defect as demonstrated using ERG recordings. The specific OP defect observed in these mice is similar to the ERG results obtained in patients with diabetic retinopathy and in related animal models.