Senescent endothelial progenitor cells show impaired vasoregenerative capacity in the ischemic retina

Abstract

 

Purpose

 

Endothelial progenitor cells (EPCs) have promise to promote vascular regeneration during ischemic retinopathies. Obtaining sufficient numbers of EPCs for autologous therapy may be hampered by cells reaching premature senescence. We examined replicative senescence in EPCs and determined if this impairs their vasoreparative properties.

 

Methods

 

EPCs isolated from human peripheral and umbilical cord blood were expanded in culture until growth arrest. Changes in gene expression associated with EPC senescence were assessed by transcriptome, proteome and secretome analysis. EPC function was evaluated in vitro by migration and tubulogenesis assays. The therapeutic potential of senescent EPCs was evaluated in vivo using the oxygen-induced retinopathy (OIR) model. At post-natal day 13 (P13), mice were divided into three experimental groups (n=6/group) for intravitreal delivery of early-passage EPCs, senescent EPCs, and vehicle. Retinas were sampled at P17 for evaluation of the vasculature.

 

Results

 

Late passage EPCs displayed a significantly increased cytoplasmic volume, increased β-galactosidase activity and accumulation of γ-H2AX foci (p<0.001). There was also a significant decrease in telomerase activity coupled with telomere shortening. Senescent (late-passage) EPCs demonstrated impaired migratory and tubulogenic capacity compared to early-passage EPCs (p<0.001). Integrated transcriptome-proteome analysis identified inflammatory signalling pathways as major components of the EPC senescence programme, with IL8 identified as a principal senescence facilitator. Depletion of IL8 in EPCs significantly extended ex-vivo lifespan, delayed senescence and enhanced function. In OIR, both early and late-passage EPCs significantly reduced retinal avascular area compared to vehicle treated eyes (p<0.001). However, senescent EPCs demonstrated reduced vasoreparative ability and did not integrate into the retinal vasculature as efficiently as early-passage EPCs. Furthermore, only early-passage EPCs significantly reduced the area of pathological pre-retinal neovascularisation (p<0.001).

 

Conclusions

 

Ex-vivo expansion of human EPCs ultimately leads to replicative senescence linked to cellular dysfunction. Modulation of EPC senescence may improve the potential of autologous cell therapy for ischemic retinopathies.

 

 

Senescent (LP) EPCs show reduced vasoreparative ability compared to early passage (EP) EPCs

 

Keywords: 700 retinal neovascularization • 721 stem cells • 706 retinopathy of prematurity