Using DARC to demonstrate diabetic eye disease

Abstract

Purpose: Retinal neurodegeneration is known to be an early event in diabetic retinopathy. We have previously identified retinal ganglion cell (RGC) apoptosis histologically in both streptazocin-induced and transgenic models of diabetes. In this study we investigated the development of RGC apoptosis in vivo in the C57BL/6-Ins2Akita/J transgenic model of diabetes.

Methods: Male C57BL/6-Ins2Akita/J diabetic transgenic mice and age-matched wild-type controls (n=6 each), were imaged using our recently established technique of DARC (Detection of Apoptotic Retinal Cells). Animals were repeatedly imaged at 8 and 16 weeks of age. Briefly, animals underwent general anaesthesia, following which intravitreal fluorescent labelled annexin 5 was administered, and eyes imaged. Following the last imaging session, animals were sacrificed. Images of the whole retina were analyzed and apoptosing cells counted, using the methods we have previously described.

Results: RGC apoptosis was observed to be maximal at 8 weeks in vivo in the Ins2Akita/J diabetic, with a significant reduction in this level (p=0.041) at 16 weeks. At 8 weeks there was more apoptosis in diabetic than matched controls, with no difference between levels at 16 weeks.

Conclusions: This is the first study as far as we are aware of the in vivo demonstration of RGC apoptosis, and confirms the previous findings of our group. The fact that the level of RGC apoptosis is highest at 8 weeks is very interesting, and we plan to investigate this further. RGC apoptosis may thus be an early marker of diabetic eye disease and potentially a screening tool in patients.