Development of a Swine Model of Proliferative Vitreoretinopathy Using RPE Cells

Abstract

Purpose: : Proliferative vitreoretinopahty (PVR) is the major complication of retinal detachment surgery and a common complication of posterior segment ocular trauma. We sought to develop a large animal model of PVR in the swine to study the pathophysiology of the disease and to develop novel methods of prevention.

Methods: : PVR was induced in 3 months old domestic swine in three steps: (1) induction of a posterior vitreous detachment by 20 gauge pars plana vitrectomy, (2) creation of a retinal detachment by the injection of 500~1000 μl of BSS beneath the retina, and (3) injection of 8x10⁴ RPE cells into the vitreous cavity. Two different RPE populations were injected - GFP positive RPE cells (GFP-RPE) cultured for 1~7 weeks (n=12) and freshly isolated RPE cells (RPE^f) (n=15). Control eyes (n=10) had the same surgical procedures without the injection of RPE cells into the vitreous cavity. PVR was clinically graded post-operatively on days 3, 7, 10, and 14. Animals were sacrificed on day 14 and the eyes enucleated for histological analysis.

Results: : The retina reattached spontaneously by day 3 in all control eyes and eyes injected with RPE cells except for 3 eyes injected with GFP-RPE. The retina remained attached on day 14 in all controls eyes. In contrast, injection of RPE cells induced PVR by day 14 in all eyes (27/27). The RPE^f group had no detachment on day7, but by day14 retinal detachment was observed in 10/15 eyes. The GFP-RPE group developed a retinal detachment earlier (8/12 eyes on day7) and the final PVR grading was more severe than RPE^f. The location of the GFP-RPE cells on the inner surface of the retina correlated with the area of retinal detachment. Sections of enucleated eyes showed GFP-RPE cells on the inner surface of the retina, and the RPE origin of these cells was confirmed by the expression of cytokeratin. Some of these GFP-RPE cells expressed α-SMA, a marker for myofibroblasts, as well as fibronectin, a marker for fibrosis.

Conclusions: : We established a swine model of PVR that recapitulates key clinical features found in man. This model can be used to study the pathophysiology of this disease, as well as novel therapeutic strategies to prevent PVR.

Keywords: proliferative vitreoretinopathy • retinal detachment