Irradiation pretreatment before fibroblast implantation in experimental PVR

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.

Experimental Posterior Perforating Ocular Injury in Rabbit Eyes: Effects of Radiotherapy with or without Intravitreal Cyclosporin on Vitreous Proliferation

Double perforating ocular injuries were made in 30 rabbits and the effects of radiotherapy (RT) alone or in combination with cyclosporin (CS) on vitreous proliferation investigated. Thirteen rabbits in group 1 received RT alone (600 cGy), and 13 rabbits in group 2 received RT combined with 100 microg of intravitreal CS. No treatment was given to 4 rabbits in the control group (group 3). All animals were ophthalmologically examined on the 1st, 3rd, 7th, 14th and 28th days following the injury and the clinical findings scored; they were sacrificed on the 28th day, and histopathological scoring was made. The median histopathological score of the RT group (4.0; range: 0-8) was significantly higher than that of the CS + RT group (1.0; range: 0-5; p = 0.018). We conclude that intravitreal CS may be used as an adjunctive agent to RT to inhibit intraocular proliferation following penetrating ocular injury in rabbits.

The antiproliferative effect of fractionized radiation therapy: optimization of dosage

Fractionized radiation therapy with high-energy electrons have proven to reduce retinal detachment rate from 85% to 5% in the fibroblast model using a dosage of 3000 rad, starting from the first postoperative day. The purpose of this study is to gain more information about the therapeutic range of fractionized radiation therapy in experimental PVR. We therefore investigated the efficacy of this therapy when the total dose is reduced to 2000 rad. Irradiation treatment started on the first postoperative day. Eight weeks after cell implantation 5 of 14 eyes (35%) in the irradiated group and 15 of 16 eyes of the control group (93%) showed traction detachment. The statistically significant result proves a broad therapeutic range of fractionized radiation therapy in experimental PVR. We believe that a combination with antiinflammatory drugs could lead to a dose reduction in both therapies in patients.