Small Interfering RNA Targeted to ASPP2 Promotes Progression of Experimental Proliferative Vitreoretinopathy

In vitro laboratory models of proliferative vitreoretinopathy

Proliferative vitreoretinopathy (PVR), the most common cause of recurrent retinal detachment, is characterized by the formation and contraction of fibrotic membranes on the surface of the retina. There are no Food and Drug Administration (FDA)-approved drugs to prevent or treat PVR. Therefore, it is necessary to develop accurate in vitro models of the disease that will enable researchers to screen drug candidates and prioritize the most promising candidates for clinical studies. We provide a summary of recent in vitro PVR models, as well as avenues for model improvement. Several in vitro PVR models were identified, including various types of cell cultures. Additionally, novel techniques that have not been used to model PVR were identified, including organoids, hydrogels, and organ-on-a-chip models. Novel ideas for improving in vitro PVR models are highlighted. Researchers may consult this review to help design in vitro models of PVR, which will aid in the development of therapies to treat the disease.

Experimental Models to Study Epithelial-Mesenchymal Transition in Proliferative Vitreoretinopathy

Proliferative vitreoretinal diseases (PVDs) encompass proliferative vitreoretinopathy (PVR), epiretinal membranes, and proliferative diabetic retinopathy. These vision-threatening diseases are characterized by the development of proliferative membranes above, within and/or below the retina following epithelial-mesenchymal transition (EMT) of the retinal pigment epithelium (RPE) and/or endothelial-mesenchymal transition of endothelial cells. As surgical peeling of PVD membranes remains the sole therapeutic option for patients, development of in vitro and in vivo models has become essential to better understand PVD pathogenesis and identify potential therapeutic targets. The in vitro models range from immortalized cell lines to human pluripotent stem-cell-derived RPE and primary cells subjected to various treatments to induce EMT and mimic PVD. In vivo PVR animal models using rabbit, mouse, rat, and swine have mainly been obtained through surgical means to mimic ocular trauma and retinal detachment, and through intravitreal injection of cells or enzymes to induce EMT and investigate cell proliferation and invasion. This review offers a comprehensive overview of the usefulness, advantages, and limitations of the current models available to investigate EMT in PVD.

Upregulation of ASPP2 expression alleviates the development of proliferative vitreoretinopathy in a rat model

AIM

To investigate whether upregulation of apoptosis-stimulating p53 protein 2 (ASPP2) expression could alleviate the development of proliferative vitreoretinopathy (PVR) in a rat model.

METHODS

ASPP2-lentivirus or scrambled-lentivirus were transfected into ARPE-19 cells, followed with measurements of cell cytotoxicity by cell counting kit-8 assay. ASPP2 upregulation was confirmed by Western blotting and immunocytochemistry. Then ARPE-19 cells pretreated with ASPP2-lentivirus were intravitreally injected to Brown Norway rats to induce PVR models. PVR development and retinal function were evaluated by retinal photography and electroretinography, respectively. Finally, epithelial-mesenchymal transition as well as autophagy were investigated in rats' retinas via Western blotting.

RESULTS

Protein expression of ASPP2 was significantly upregulated by ASPP2-lentivirus transfection in ARPE-19 cells. The development and progression of PVR were impeded significantly in rats with intravitreal injection of ARPE-19 cells pretreated with ASPP2-lentivirus. Accordingly, retinal functions were less affected and PVR grades were much lower in rats with ASPP2-lentivirus compared to scrambled-lentivirus treatment. Moreover, epithelial-mesenchymal transition and autophagy markers were decreased in the retinas of rats treated with ASPP2-lentivirus.

CONCLUSION

ASPP2-lentivirus transfected to ARPE-19 cells mitigates the progression of PVR in rat models, which might be partly through reduced autophagy and attenuated epithelial-mesenchymal transition. ASPP2 might stand as a new approach for PVR treatment in the future.

METTL3 attenuates proliferative vitreoretinopathy and epithelial-mesenchymal transition of retinal pigment epithelial cells via wnt/β-catenin pathway

Proliferative vitreoretinopathy (PVR) is a refractory vitreoretinal fibrosis disease, and epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells is the key pathological mechanism of PVR. However, few studies focused on the role of METTL3, the dominating methyltransferase for m6A RNA modification in PVR pathogenesis. Immunofluorescence staining and qRT-PCR were used to determine the expression of METTL3 in human tissues. Lentiviral transfection was used to stably overexpress and knockdown METTL3 in ARPE-19 cells. MTT assay was employed to study the effects of METTL3 on cell proliferation. The impact of METTL3 on the EMT of ARPE-19 cells was assessed by migratory assay, morphological observation and expression of EMT markers. Intravitreal injection of cells overexpressing METTL3 was used to assess the impact of METTL3 on the establishment of the PVR model. We found that METTL3 expression was less in human PVR membranes than in the normal RPE layers. In ARPE-19 cells, total m6A abundance and the METTL3 expression were down-regulated after EMT. Additionally, METTL3 overexpression inhibited cell proliferation through inducing cell cycle arrest at G0/G1 phase. Furthermore, METTL3 overexpression weakened the capacity of TGFβ1 to trigger EMT by regulating wnt/β -catenin pathway. Oppositely, knockdown of METTL3 facilitated proliferation and EMT of ARPE-19 cells. In vivo, intravitreal injection of METTL3-overexpressing cells delayed the development of PVR compared with injection of control cells. In summary, this study suggested that METTL3 is involved in the PVR process, and METTL3 overexpression inhibits the EMT of ARPE-19 cells in vitro and suppresses the PVR process in vivo.

Effect of Methotrexate on an In Vitro Patient-Derived Model of Proliferative Vitreoretinopathy

Purpose

The purpose of this study was to develop a method for isolating, culturing, and characterizing cells from patient-derived membranes in proliferative vitreoretinopathy (PVR) to be used for drug testing.

Methods

PVR membranes were obtained from six patients with grade C PVR. Membrane fragments were analyzed by gross evaluation, fixed for immunohistologic studies to establish cell identity, or digested with collagenase II to obtain single cell suspensions for culture. PVR-derived primary cultures were used to examine the effects of methotrexate (MTX) on proliferation, migration, and cell death.

Results

Gross analysis of PVR membranes showed presence of pigmented cells, indicative of retinal pigment epithelial cells. Immunohistochemistry identified cells expressing α-smooth muscle actin, glial fibrillary acidic protein, Bestrophin-1, and F4/80, suggesting the presence of multiple cell types in PVR. Robust PVR primary cultures (C-PVR) were successfully obtained from human membranes, and these cells retained the expression of cell identity markers in culture. C-PVR cultures formed membranes and band-like structures in culture reminiscent of the human condition. MTX significantly reduced the proliferation and band formation of C-PVR, whereas it had no significant effect on cell migration. MTX also induced regulated cell death within C-PVR as assessed by increased expression of caspase-3/7.

Conclusions

PVR cells obtained from human membranes can be successfully isolated, cultured, and profiled in vitro. Using these primary cultures, we identified MTX as capable of significantly reducing growth and inducing cell death of PVR cells in vitro.

Effects of ASPP2 on proliferation and apoptosis of malignant spinal tumor cells

Malignant spinal tumors have rapid progression and destruct spines or other tissues, leading to metastasis of peripheral organs, causing high difficulty for surgery, recurrence and worse prognosis, thus severely affecting patient life quality and survival period. Apoptosis stimulating protein 2 of p53 (ASSP2) is one member of p53 binding protein family pro-apoptotic member, and can enhance apoptotic activity via modulating p53 pathway. Previous study found critical roles of ASPP2 in occurrence and progression of tumors, whilst the functional role of mechanism of ASPP2 on malignant spinal tumor cells has not been illustrated. Malignant spinal tumor tissue and adjacent tissues were collected for testing ASPP2 mRNA and protein expression in real-time PCR and Western blot. ASPP2 over-expression vector was used to transfect tumor cells, whilst MTT assay was employed for tumor proliferation, followed by p53 expression in Western blot. Caspase 3 activity assay was employed for testing the effect on cell apoptosis. Flow cytometry was employed for tumor cell apoptosis. Real-time PCR tested expressional change of Bcl2 and Bax. ASPP2 mRNA/protein level was significantly depressed in malignant spinal tumor tissues (P<0.05 compared to adjacent tissues). ASPP2-overexpression vector transfection tumor cells increased apoptosis and inhibited proliferation, accompanied with lower Bcl-2, higher Bax, Caspase 3 and p53 (P<0.05 compared to control group). ASPP2 is down-regulated in malignant spinal tumor tissues. ASPP2 can inhibit malignant spinal tumor cell proliferation via mediating p53 expression for cell apoptosis, thus can work as one molecular target for tumor diagnosis and prognostic analysis.

Identification of TP53BP2 as a Novel Candidate Gene for Primary Open Angle Glaucoma by Whole Exome Sequencing in a Large Multiplex Family

Primary open angle glaucoma (POAG) is a major type of glaucoma characterized by progressive loss of retinal ganglion cells with associated visual field loss without an identifiable secondary cause. Genetic factors are considered to be major contributors to the pathogenesis of glaucoma. The aim of the study was to identify the causative gene in a large family with POAG by applying whole exome sequencing (WES). WES was performed on the DNA of four affected family members. Rare pathogenic variants shared among the affected individuals were filtered. Polymerase chain reaction and Sanger sequencing were used to analyze variants segregating with the disease in additional family members. WES analysis identified a variant in TP53BP2 (c.109G>A; p.Val37Met) that segregated heterozygously with the disease. In silico analysis of the substitution predicted it to be pathogenic. The variant was absent in public databases and in 180 population-matched controls. A novel genetic variant in the TP53BP2 gene was identified in a family with POAG. Interestingly, it has previously been demonstrated that the gene regulates apoptosis in retinal ganglion cells. This supports that the TP53BP2 variant may represent the cause of POAG in this family. Additional screening of the gene in patients with POAG from different populations is required to confirm its involvement in the disease.