Effects of human endothelial colony forming cells on oxygen induced retinopathy in various immune competent cell-depleted mice.

Abstract

Purpose : Human endothelial colony forming cells (ECFCs) are a homogeneous subpopulation of endothelial progenitor cells that can be isolated from human cord blood. We and others have shown that ECFCs enhance vascular repair in a murine model of oxygen induced retinopathy (OIR). Past studies all used C57Bl/6 mice as the recipient and, thus, it is unclear if the rescue effect is dependent on the immune response due to interspecies cross-reaction. In this study we assessed the efficacy of human ECFCs in rescuing OIR using mice lacking various immune-competent cell types.

Methods : Human ECFCs were derived from cord blood. We used the following mice: Rag2 KO mice, lacking mature lymphocytes; LCK cre mice crossed with transgenic mice expressing human diphtheria toxin receptors (DTR), for LCK+ T-lymphocyte ablation (LCK-DTR mice); and LysM-DTR mice, for LysM+ myeloid cell ablation. We induced OIR in these mice and injected 1.0 x 10⁵ ECFCs or vehicle intravitreally at P12. Immune cell depletion in DTR transgenic mice was subsequently started by intraperitoneal injection of 25 ng/g DT for 5 consecutive days. We analyzed the percentage of area of neovascular tufts (NV) and vascular obliteration (VO) at P17 (n>8).

Results : Rag 2 KO mice injected with ECFCs showed 65.6 % reduction in NV (p<0.001) and 36.3 % reduction in VO when compared to vehicle control (p<0.001). These results were similar to our previous reports using C57Bl/6 wild type mice. In LCK-DTR mice after receiving ECFCs, the areas of NV or VO did not show any statistically significant change either between cre (+) and cre (-) mice (NV: 0.42 ± 0.24 % and 1.39 ± 0.75 %, respectively (p=0.26). VO: 3.68 ± 1.13 % and 4.91 ± 1.95 %, respectively (p=0.60).). LysM-DTR mice injected with ECFCs also showed no statistically significant change between cre (+) and cre (-) mice (NV: 0.28 ± 0.25 % and 0.20 ± 0.16 %, respectively (p=0.80). VO: 2.73 ± 0.95 % and 1.68 ± 0.53 %, respectively (p=0.35).).

Conclusions : We did not detect any statistically significant difference in OIR rescue between immune-cell depleted and control mice following ECFC injection. These results suggest the rescue effect of ECFCs in OIR is not a simple consequence of interspecies immune reaction induced by ECFCs.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.