Modulating p75^NTR protects against ischemic retinopathy via increased vascular homing of mesenchymal stem cells

Abstract

Purpose : Ischemic retinopathy is characterized by initial ischemia that progresses into neovascularization. We reported that deletion of death receptor; p75^NTR enhanced vascular repair in oxygen-induced retinopathy model and preserved expression of angiogenic markers; SDF-1, CXCR-4 and CXCR-7 responsible for mesenchymal stem cells (MSCs) homing to vasculature in diabetic ischemic limbs. MSCs are potential candidates for neuro-regeneration in various retinal diseases, nevertheless, their role in retinal vascular repair remains poorly addressed. Our aim is to investigate the contribution of MSCs to vascular protection associated with p75^NTR deletion in ischemic retina.

Methods : WT and p75^NTR-/- mice were subjected to retinal ischemia reperfusion (I/R) injury. Murine GFP-labeled p75^NTR-positive or p75^NTR-null MSCs were injected intravitreally 2 days post-I/R and vascular homing was assessed one week later. Acellular capillaries were counted on trypsin-digested retinas 10 days post I/R. In vitro, MSCs were treated with a specific pharmacological inhibitor against p75^NTR; LM11A-31 and conditioned media was co-cultured with human retinal endothelial cells (HRECs) to examine angiogenic response.

Results : p75^NTR-/- ischemic retinas showed 2-Fold increase in acellular capillaries compared to 3-Fold increase in WT as well as preserved mRNA expression of CXCR-7. p75^NTR-MSCs showed best incorporation into ischemic retinal vasculature one-week post-injection and completely protected against acellular capillaries in ischemic p75^NTR-/- retinas. p75^NTR-null MSCs showed better incorporation into WT ischemic retinal vasculature and significantly decreased acellular capillaries by 60% compared to ischemic WT receiving p75^NTR-MSCs. p75^NTR-null MSCs showed increased mRNA expression of CXCR-4 as well as increased mRNA and protein expression of CXCR-7. In vitro, inhibition p75^NTR in MSCs enhanced angiogenic response of their conditional media in HRECs, where HRECs showed enhanced migration (1.3-Fold) and tube formation (2.7-Fold).

Conclusions : Our results showed that deletion of p75^NTR protects against retinal ischemia by mechanisms involving improved MSCs homing to ischemic vasculature to prevent vascular degeneration. Thus, combination of MSCs injection and p75^NTR inhibitor can serve as potential therapeutic strategy to harness vascular repair in ischemic retinopathy diseases.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.