Abstract
Purpose :
We previously reported that LDOPA treatment in diabetic patients had a sustained benefit on retinal function two weeks after the end of LDOPA treatment (Motz et al., 2020). Here, we determined if LDOPA treatment produced similar protection in diabetic mice after treatment cessation. Additionally, we evaluated the spatial relationship of microglia and retinal vasculature, a known component of microglia-mediated vasomodulation, to provide insight into mechanisms of LDOPA protection.
Methods :
Hyperglycemia (≥250 mg/dL) was induced in C57BL/6J mice by low-dose STZ (50 mg/kg, five days). Visual function was quantified by optomotor response (OMR). Once a functional deficit was detected, LDOPA (10 mg/kg LDOPA, 2.5 mg/kg carbidopa) or vehicle was injected via IP for 5 days/week over two weeks (n=10-15/group). Mice were assessed weekly by OMR for two weeks post-LDOPA treatment. Post euthanasia, eyes (STZ+LDOPA n=2; STZ+vehicle=3; control+LDOPA=4; control+vehicle=4) were fixed in 4% paraformaldehyde and stained for vascular (Collagen IV) and microglia (Iba1) markers. Imaged retinal flatmounts were separated by superior vascular plexus (SVP), intermediate capillary plexus (ICP), and deep capillary plexus (DCP). Vasculature and microglial soma were reconstructed via Bitplane Imaris (10.0) while masked to experimental conditions. Two-way and one-way ANOVAs followed by post hoc analyses were used to determine the effect of LDOPA on visual function and microglia association with retinal vasculature.
Results :
STZ+LDOPA mice remained improved over STZ+vehicle mice in spatial frequency for up to two weeks (0.37±0.02 vs. 0.35±0.01 c/d, p=0.03) and contrast sensitivity for one week (6.35±0.72 vs. 5.78±0.44 a.u., p=0.01) following conclusion of LDOPA treatment. During sustained visual acuity protection, trends suggested reduced association of microglial soma with ICP vasculature in control+LDOPA mice compared to control+vehicle mice (0.05±0.04 vs. 0.11±0.02 a.u., p=0.05), potentially indicating LDOPA-driven microglial dissociation from vasculature.
Conclusions :
Similar to patients with diabetes, we show that LDOPA treatment produces sustained benefit in diabetic mice after treatment cessation. Mechanisms behind protection remain unknown, but LDOPA status may modulate microglial association with retinal vasculature. Future work will determine the necessity of microglia for LDOPA’s benefit in the diabetic mouse retina.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.