Novel Diabetic Mouse Models as Tools for Investigating Diabetic Retinopathy

Abstract

ObjectiveMouse models possessing green fluorescent protein (GFP) and/or human aldose reductase (hAR) in vascular tissues have been established and crossed with naturally diabetic Akita mice to produce new diabetic mouse models.Research Design and MethodsColonies of transgenic C57BL mice expressing GFP (SMAA-GFP), hAR (SMAA-hAR) or both (SMAA-GFP-hAR) in vascular tissues expressing smooth muscle actin were established and crossbred with C57BL/6-Ins2Akita/J (AK) mice to produce naturally diabetic offspring AK-SMAA-GFP and AK-SMAA-GFP-hAR. Aldose reductase inhibitor AL1576 (ARI) was administered in chow. Retinal and lenticular sorbitol levels were determined by HPLC. Retinal functions were evaluated by electroretinography (ERGs). Growth factor and signaling changes were determined by Western Blots using commercially available antibodies. Retinal vasculatures were isolated from the neural retina by enzymatic digestion. Flat mounts were stained with PAS-hematoxylin and analyzed.ResultsAkita transgenics developed DM by 8 weeks of age with blood glucose levels higher in males than females. Sorbitol levels were higher in neural retinas of AK-SMAA-GFP-hAR compared to AK-SMAA-GFP mice. AK-SMAA-GFP-hAR mice also had higher VEGF levels and reduced ERG scotopic b-wave function, both of which were normalized by AL1576. AK-SMAA-GFP-hAR mice showed induction of the retinal growth factors bFGF, IGF-1, and TGFβ, as well as signaling changes in P-Akt, P-SAPK/JNK and P-44/42 MAPK that were also reduced by ARI treatment. Quantitative analysis of flat mounts in 18 week AK-SMAA-GFP-hAR mice revealed increased loss of nuclei/capillary length and a significant increase in the percentage of acellular capillaries present which was not seen in AK-SMAA-GFP-hAR treated with ARI.Conclusions/SignificanceThese new mouse models of early onset diabetes may be valuable tools for assessing both the role of hyperglycemia and AR in the development of retinal lesions associated with diabetic retinopathy.

Novel transgenic mouse models develop retinal changes associated with early diabetic retinopathy similar to those observed in rats with diabetes mellitus

“…This has resulted in naturally diabetic mice (AK-SMAA-GFP-hAR) that demonstrate increased retinal AR activity compared to similar mice not expressing hAR. Here, we report that the retinal growth factor and signaling changes as well as vascular lesion changes that we have demonstrated in AK-SMAA-GFP-hAR mice (Kador et al, 2012) are more similar to changes observed in diabetic rats than mice not expressing aldose reductase.…”

“…The development of the AK-SMAA-GFP-hAR transgenic mice and their genotyping has previously been reported (Kador et al, 2012). In the AK-SMAA-GFP-hAR group initial blood glucose levels ranged from 247–600 mg/dL for females and 342–600 mg/dL for males and in the AK-SMAA-GFP group blood glucose levels ranged from 245–572 mg/dL for females and 332–600 mg/dL for males.…”

“…Retinal sorbitol levels were determined by high-performance liquid chromatography (HPLC) as previously described (Kador et al, 2012). …”

“…The detection of the select proteins by western blot was conducted as follows (Kador et al, 2012; Zhang et al, 2012). The scanned images were subsequently photo enhanced using Corel Photo-Paint X-3.…”

“…Compared to rats, diabetic mice also have lower AR activity in other tissues such as the lens and sciatic nerve (Chung and Chung, 2003; Gaynes and Watkins, 1989; Llewelyn et al, 1991; Markus et al, 1983). Since the lower AR activity in mice may contribute to differences in retinal changes observed between the mouse and rat, select transgenic mice expressing human aldose reductase (SMAA-hAR), green fluorescent protein (SMAA-GFP), or both (SMAA-GFP-hAR) under the control of the smooth muscle α-actin promoter have been established (Kador et al, 2012). DM was subsequently introduced into these transgenic mice by cross-breeding with naturally diabetic C57BL/6-Ins2 Akita /J (AK) mice.…”