Inhibitory Effect of Adenoviral Vector-Mediated Delivery of p21WAF1/CIP1on Retinal Vascular Endothelial Cell Proliferation and Tube Formation in Cultured Rhesus Monkey Cells (RF/6A)

Low expression of RBP4 in the vitreous humour of patients with proliferative diabetic retinopathy who underwent Conbercept intravitreal injection

Intravitreal injection of anti-VEGF antibodies has been widely used in the treatment of proliferative diabetic retinopathy (PDR). However, anti-VEGF drugs can exacerbate fibrosis and eventually lead to retinal detachment. To explore proteins closely related to fibrosis, we conducted proteomic analysis of human vitreous humour collected from PDR patients who have or have not intravitreal Conbercept (IVC) injection. Sixteen vitreous humour samples from PDR patients with preoperative IVC and 20 samples from those without preoperative IVC were examined. An immunodepletion kit was used to remove high-abundance vitreous proteins. Conbercept-induced changes were determined using a tandem mass tag-based quantitative proteomic strategy. Enzyme-linked immunosorbent assays were performed to confirm the concentrations of selected proteins and validate the proteomic results. Based on a false discovery rate between 0.05% and -0.05% and a fold-change > 1.5, 97 proteins were altered (49 higher levels and 48 lower levels) in response to IVC. Differentially expressed proteins were found in the extracellular and intracellular regions and were found to be involved in VEGF binding and VEGF-activated receptor activity. Protein-protein interactions indicated associations with fibrosis, neovascularisation and inflammatory signalling pathways. We found the low levels of RBP4 in the vitreous humour of PDR patients with IVC injection, as revealed by ELISA and proteomic profiling. Moreover, RBP4 significantly restored the mitochondrial function of HRMECs induced by AGEs and down regulated the level of glycolysis. Our study is the first to report that RBP4 decreases in the vitreous humour of PDR patients who underwent Conbercept treatment, thereby verifying the role of RBP4 in glucose metabolism. Results provide evidence for the potential mechanism underlying Conbercept-related fibrosis.

Rapamycin prevents retinal neovascularization by downregulation of cyclin D1 in a mouse model of oxygen-induced retinopathy

Background

Rapamycin (RAPA) is a potent angiogenic inhibitor and the aim of this study is to identify the inhibitory effect of RAPA on retinal neovascularization (RNV) in experimental oxygen-induced retinopathy (OIR).

Methods

Forty-two 7-day-old C57BL/6 J mice were randomly divided into normoxia control group (14 mice), OIR group (14 mice), and rapamycin (RAPA) group. OIR model was induced in OIR and RAPA group. Vehicle and RAPA (2 mg/kg/d) was injected intraperitoneally daily from postnatal day 12 (P12) in OIR and RAPA groups, respectively. RNV was evaluated using fluorescence angiography and histopathology on P17. Non-perfused areas of retina were analyzed by Image-Pro plus 6.0 software. Retinal expression of cyclin D1 was detected both at mRNA and protein levels.

Results

RAPA treatment significantly decreased RNV, non-perfused areas and number of endothelial cell nuclei breaking through the internal limiting membrane (ILM) in OIR mice. Moreover, RAPA decreased activation of cyclin D1 in retina caused by OIR.

Conclusion

RAPA can inhibit RNV by downregulating the expression of cyclin D1, which indicates its therapeutic potential in treating RNV-related diseases.

Adenoviral Vector-Mediated Delivery of p21WAF1/CIP1 Prevents Retinal Neovascularization in an Oxygen-Induced Retinopathy Model

OBJECTIVE

To evaluate the inhibitory effect(s) of adenovirus (Ad) vector-mediated delivery of p21^WAF1/CIP1 (Ad-p21) on retinal neovascularization (RNV) in an animal model of oxygen-induced retinopathy (OIR).

METHODS

RNV was determined by examination of retinal fiat mounts and sections postnatal (P) day-17 (P17). Non-perfused retinal areas were analyzed using Image-Pro plus 6.0 software. Reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analysis were used to measure mRNA and protein expression of p21 and cyclin-dependent kinase (CDK) 2.

RESULTS

Compared with phosphate buffer saline (PBS) and Ad-NC group mice, non-perfused retinal areas, neovascularization, and number of endothelial cell nuclei breaking through the internal limiting membrane (ILM) in Ad-p21 group mice were significantly reduced. There were fewer non-perfused retinal areas in Ad-p21 mice than in either PBS or Ad-NC group mice, the differences being significant (F = 101.634; p < 0.05). Levels of p21 mRNA and protein in the Ad-p21 group had increased significantly compared with the other three groups (F = 839.664, 509.817; p < 0.05). Levels of CDK2 mRNA and protein in the Ad-p21 group decreased significantly (F = 301.858, 592.882; p < 0.05).

CONCLUSIONS

Ad-p21 inhibits RNV in OIR. A potential underlying mechanism for this may be that overexpression of p21 arrests the cell cycle at the G1- to S-phase transition via inhibition of CDK2 activity.

Matrigel: from discovery and ECM mimicry to assays and models for cancer research

The basement membrane is an important extracellular matrix that is found in all epithelial and endothelial tissues. It maintains tissue integrity, serves as a barrier to cells and to molecules, separates different tissue types, transduces mechanical signals, and has many biological functions that help to maintain tissue specificity. A well-defined soluble basement membrane extract, termed BME/Matrigel, prepared from an epithelial tumor is similar in content to authentic basement membrane, and forms a hydrogel at 24-37°C. It is used in vitro as a substrate for 3D cell culture, in suspension for spheroid culture, and for various assays, such as angiogenesis, invasion, and dormancy. In vivo, BME/Matrigel is used for angiogenesis assays and to promote xenograft and patient-derived biopsy take and growth. Studies have shown that both the stiffness of the BME/Matrigel and its components (i.e. chemical signals) are responsible for its activity with so many different cell types. BME/Matrigel has widespread use in assays and in models that improve our understanding of tumor biology and help define therapeutic approaches.

Overexpression p21WAF1/CIP1 in suppressing retinal pigment epithelial cells and progression of proliferative vitreoretinopathy via inhibition CDK2 and cyclin E

Background

P21 is one kind of cyclin-dependent kinase inhibitor that can prevent cells from going through the G1/S phase checkpoint and inhibit cell proliferation. Proliferative vitreoretinopathy (PVR) is a proliferative response in the eye. The aim of this study was to determine whether p21^Waf1/Cip1 (p21) suppresses the proliferation and migration of retinal pigment epithelial (RPE) cells in vitro and controls PVR development in vivo.

Methods

Cell cycle analyses and transwell assays were conducted to assess cell proliferation characteristics and the migration ability of RPE cells after transfection with p21. Western blot and reverse-transcription polymerase chain reaction technologies were used to detect the expression of p21, CDK₂ and cyclinE in RPE cells and rabbit retinal tissues. The impact of increasing p21 expression on PVR development was conducted by implantation of an adenovirus vector containing rabbit p21 (rAd-p21) in a PVR rabbit model. The prevalence of PVR and retinal detachment was determined by indirect ophthalmoscopy on days 3, 7, 14, and 21 after the injection of rAd-p21 into the vitreous. B scans and hematoxylin-eosin staining were employed to check rabbit retinas on day 21.

Results

Cell cycle analyses and transwell assays showed that p21 inhibited the proliferation and migration of RPE cells. Increased expression of p21 was detected in cultured RPE cells and rabbit retinas after transfection with the p21 gene, whereas levels of CDK₂ and cyclinE were decreased. The increase in p21 expression effectively suppressed the development of PVR in a rabbit model.

Conclusions

The increase in p21 expression in RPE cells not only inhibits the proliferation and migration of RPE cells in vitro, but also suppresses the development of PVR in vivo, which indicates its therapeutic potential in treating PVR.

Curcumin inhibits human retinal pigment epithelial cell proliferation

Proliferative vitreoretinopathy (PVR) is a common cause of intraoperative failure following retinal reattachment surgery and is mediated in part through the migration, de-differentiation and proliferation of retinal pigment epithelial (RPE) cells. Given the cytotoxic effects of curcumin on epithelial and endothelial cells, in this study, we assessed the effects of curcumin on human RPE (hRPE) cell proliferation. WST-1 analysis revealed that curcumin significantly inhibited primary hRPE cell proliferation in a dose- and time-dependent manner (P<0.001) with the greatest inhibition observed at the dose of 15 μg/ml curcumin. Flow cytometric analysis indicated that the cytotoxic effects of curcumin on hRPE cell proliferation were mediated by cell cycle arrest at the G0/G1 phase and the induction of apoptosis (both P<0.001), which was confirmed by ultrastructural analysis using transmission electron microscopy. Furthermore, western blot analysis revealed that curcumin induced p53 and p21^WAF1/CIP1 expression with a concomitant decrease in proliferating cell nuclear antigen protein levels (P<0.05). Curcumin effectively inhibited primary hRPE cell proliferation, which may be mediated by the p53 pathway. Further in vivo studies are required in order to fully explore the therapeutic potential of curcumin for PVR.

p53/p21 Pathway involved in mediating cellular senescence of bone marrow-derived mesenchymal stem cells from systemic lupus erythematosus patients

Our and other groups have found that bone marrow-derived mesenchymal stem cells (BM-MSCs) from systemic lupus erythematosus (SLE) patients exhibited senescent behavior and are involved in the pathogenesis of SLE. Numerous studies have shown that activation of the p53/p21 pathway inhibits the proliferation of BM-MSCs. The aim of this study was to determine whether p53/p21 pathway is involved in regulating the aging of BM-MSCs from SLE patients and the underlying mechanisms. We further confirmed that BM-MSCs from SLE patients showed characteristics of senescence. The expressions of p53 and p21 were significantly increased, whereas levels of Cyclin E, cyclin-dependent kinase-2, and phosphorylation of retinoblastoma protein were decreased in the BM-MSCs from SLE patients and knockdown of p21 expression reversed the senescent features of BM-MSCs from SLE patients. Our results demonstrated that p53/p21 pathway played an important role in the senescence process of BM-MSCs from SLE.