Abstract
Purpose: :
The clinical value of enzymatic vitreolysis to create a posterior vitreous detachment (PVD) in several retinal diseases has recently received much attention. The intravitreal injection of a high dose of Dispase, with creation of a retinal tear, has previously been reported to cause proliferative vitreoretinopathy (PVR). However, the effect of dose on the safety of Dispase has not been extensively explored. We have studied the toxicity of commercial Dispase in vitro in cell culture, as well as in vivo in the rabbit.
Methods: :
ARPE19 (origin; human retinal pigment epithelium) and r-MC1 (origin: rat ganglion cell ) cell lines were used to investigate the effect of commercial Dispase I (Sanko Junyaku, Tokyo, Japan) on cell growth using the MTT assay. The dose of Dispase varied from 50 to 2,000PU/ml and MTT was performed at 0, 24, 48 and 96 hours. Additionally, seven pigmented rabbits were injected intravitreally with 0.1ml of Dispase at doses of 10, 20, 40 and 100PU. ERGs were performed before the injection of Dispase and one week later.
Results: :
With a concentration of 50PU/ml of Dispase no difference was observed with the MTT assay in either the ARPE19 or r-MCI cell lines compared to the control. With > 100PU/ml light absorption with the MTT assay decreased. Similarly, the intravitreal injection of 10PU of Dispase in 6 eyes resulted in no change in the ERG at 1 week. However, higher doses resulted in a decreased ERG - 20PU, in 1 of 2 eyes; 40PU, in 2 of 2 eyes; 100PU in 4 of 4 eyes. Histopathological study of these eyes is pending.
Conclusions: :
The toxic effect of Dispase is dose related. Fifty PU/ml of Dispase did not effect the in vitro cell growth of the ARPE19 or r-MC1 cell lines. Similarly, 10PU of Dispase injected intravitreally did not effect the in vivo ERG at 1 week in rabbits. However, higher doses were associated with toxic side effects. The active enzyme in commercial Dispase is ≤ 14% of the total protein in solution. Nevertheless, enzymatic vitreolysis with commercial Dispase can be safely achieved with a low dose of the enzyme. Purified Dispase is supposed to have a greater safety profile.
Keywords: electroretinography: non-clinical • vitreous • enzymes/enzyme inhibitors