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Jasenka Guduric-Fuchs, Sarah Chambers, Christina O Neill, Reinhold Medina, Alan W Stitt; Pro-Tissue Repair capacity of circulating angiogenic cells (CACs) is impaired when exposed to High Glucose. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4524.
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© ARVO (1962-2015); The Authors (2016-present)
Endothelial progenitor cells (EPCs) promote angiogenesis, maintain and regenerate the vasculature. We have recently demonstrated that early EPCs represent circulating angiogenic cells (CACs) which express haematopoietic markers and are molecularly and functionally similar to M2-macrophages. CACs-based cytotherapy significantly enhances vascular repair in the murine ischaemic retina and is mediated by paracrine release of angiogenic factors. This pro-angiogenic potential of CACs could be harnessed as a novel cellular therapy for the treatment of diabetic retinopathy. However, since CACs are akin to M2-macrophages, a switch between their pro-angiogenic and pro-inflammatory phenotype is possible and will be dictated by their environment. Therefore, the plasticity and pro-angiogenic function of CACs needs to be assessed within the context of a diabetic milieu.
CACs were compared to M1 and M2 polarised macrophages, by transcriptomics analysis, gene expression, flow cytometry, and 3D tubulogenesis assay. CACs were exposed to 30mM D-glucose (high DG) for 4 days. In vitro 3D-angiogenesis assay was used to assess the pro-angiogenic potential of CACs and their conditioned medium on retinal microvascular endothelial cell (RMEC) tube formation. Gene expression from high DG-treated cells was compared to M1 and M2-macrophages by RT-qPCR.
Flow cytometry-based cell surface immunophenotyping clearly distinguised CACs from M1 and M2 macrophages based on their high expression of CD163 and lack of ICAM1. High DG significantly reduced the pro-angiogenic potential of CACs and their conditioned medium on retinal microvascular endothelial cell (RMEC) tube formation (P<0.0001), compared to the untreated control (5mM DG) and the osmotic control (5mM DG + 25mM L-Glucose LG). DG-treated CACs induced a more M1 pro-inflammatory profile, with higher levels of IL1alpha, IL1beta, and IL6 and lower levels of M2 markers CD163 and CD204.
This study shows that although CACs are capable of inducing angiogenesis and act as M2 macrophages, they have a reduced capacity to promote angiogenesis when exposed to high DG in vitro. This significant decrease in vasoreparative properties is coupled to phenotypic changes towards a more M1 profile, potentially driven by IL1beta. The plasticity of CACs is an important consideration when delivering them as a cellular therapy into the diabetic milieu.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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