Endothelial Progenitor Cells With Low Aldehyde Dehydrogenase Activity Recruited Monocyte-Derived Macrophages Through CCL2 secretion And Rescued Vessel And Photoreceptor With Retinal Degeneration

Abstract

Purpose: : Inherited retinal degenerations are characteristic of retinal neuronal apoptosis and retinal vasculature apoptosis. We previously reported that endothelial progenitor cells (EPCs) with low activity of aldehyde dehydrogenase (Alde) possess a greater ability for neuroprotection and vasoprotection in retinal degeneration than Alde-High EPCs. CCL2 was expressed more highly in Alde-Low EPCs than Alde-High EPCs. CCL2 is also known as monocyte chemotactic protein-1 and recruits macrophages. After intravitreal injection, a greater number of macrophages were recruited in retinas injected with Alde-Low EPCs than in retinas injected with Alde-High EPCs, HUVEC or PBS. To evaluate the involvement of CCL2 and macrophage, the expression level of CCL2 in Alde-Low and -High EPCs were changed by genetic engineering. Moreover, we compared the characteristics of migrated macrophage and residual retinal microglia.

Methods: : To determine whether CCL2 plays an important role in prevention of vascular attenuation and neural degeneration, we stably knocked down CCL2 in Alde-Low EPCs using shRNA. To confirm whether recovery of CCL2 with Alde-High EPCs recruited macrophages and rescued of vascular and retinal neuron, CCL2 were retrovirally introduced into Alde-High EPCs. Alde-High EPCs were infected with the retrovirus MSCV-CCL2 vector (Alde-High CCL2 EPCs). These cells were injected intravitrealy in ostnatal day 6 rd1 retinal degeneration model mouse. To compare the characteristics of migrated macrophages and residual retinal microglia, we quantified and collected cells by flow cytometric analysis.

Results: : Intravitreal injection of Alde-Low EPCs with CCL2 shRNA could not rescue the attenuation vascular in deep layer and degeneration of photoreceptors. The numbers of migrated macrophages were also completely diminished. Intravitreal injection of Alde-High CCL2 EPCs retarded the attenuation of vascular, however, it did not retard completely such as Alde-Low EPCs. The numbers of migrated macrophages after injection of Alde-High CCL2 EPCs were increased compared with Alde-High EPCs. Moreover, neurotrophic factors and anti-inflammatory mediators were highly expressed in migrated macrophages as compared with residual retinal microglia.

Conclusions: : Injection of Alde-Low EPCs might retard the degeneration of vascular and neural cells in rd1 mice through CCL2 and migrated macrophages.

Keywords: neuroprotection • retinal degenerations: cell biology • microglia