Abstract
Purpose :
We have previously identified higher incidence of vascular dropout in the deep vascular complex (DVC) in a small number of diabetic donors. To evaluate the significance of vascular dropout at DVC, we evaluated the spacing profile of the DVC and quantified number of cells locating in the inner nuclear layer (INL).
Methods :
Post-mortem ocular tissues were obtained from Moorfields Eye Bank (London, UK) and Lions NSW Eye Bank (Sydney, Australia). Whole mounts of five eyes from diabetic and four from nondiabetic donors were stained with Ulex Europaeus Agglutinin (UEA) to visualise the vasculature for signs of nonperfusion. These were then embedded in paraffin and sectioned (6μm). To evaluate the spacing profile of DVC, nearest neighbour distance (NND) was measured for capillaries in the INL on every hundredth sections of each donor and then normalized to optic disc to fovea distance (DFD). In regions with localized DVC dropout, number of INL nuclei was measured within the hemi circle with radius of half NND from normal and nonperfused capillaries. Subtypes of INL neurons were also quantified using antibodies against calretinin, choline acetyltransferase (ChAT), Protein kinase C alpha (PKCα) and parvalbumin.
Results :
Diabetic donors presented a higher percentage of overall vascular nonperfusion, more specifically, in the DVC. Spacing profile of the DVC did not differ significantly between control and diabetic donors. The distribution of NND attained a non-random distribution pattern which is negatively skewed. The number of INL nuclei and subtypes of INL neurons remained comparative between control and diabetic donor, and between normal and acellular capillaries.
Conclusions :
Our results suggested that NND remained constant across individuals, which may serve as a reliable reference to evaluate the vascular spacing profile and consequence of capillary nonperfusion. Notably, regardless of higher dropout incidence in the DVC in diabetic donors, there was no detectable cell loss around nonperfused capillaries. This was in line with reported animal DR model systems. These suggested that functional deficits in early DR was not accompanied by cells loss.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.