Analysis of the vasoreparative and anti-inflammatory potential of circulating angiogenic cells (CACS) for the treatment of diabetic retinopathy

• Main Author: Chambers, Sarah Elizabeth Jane
• Published: Queen's University Belfast 2015
• Subjects: 617.7
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.695297

Interest in regenerative medicine is increasing, in particular, the use of cell-based therapies for treatment of ischaemic diseases has renewed hope of finding a cure, beyond the treatment of symptoms. CAC-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 DR. However, CACs are dysfunctional in diabetes and raises concerns that exposure to the diabetic milieu alters CACs to a phenotype that could exacerbate pathology, rather than repair it. The aim of this thesis is to define the precise phenotype of CACs and their angiogenic properties in the context of hyperglycaemia, and to further the development of CACs as a potential clinical application for therapeutic angiogenesis, that is safe and feasible. CACs were isolated from human peripheral blood mononuclear cells that were cultured on fibronectin-coated flasks with endothelial media for 7 days. CACs are not definite M2 macrophages, but represent a distinct subtype of macrophage or macrophage-like cell that share M2 characteristics - anti-inflammatory, pro-angiogenic. CACs conditioned media (CM) can promote tube formation in endothelial cells; however, CACs CM pro-angiogenic potential is reduced when cells are exposed to high D-glucose treatment in vitro. This is due to a change in phenotype towards a pro-inflammatory profile by two potential mechanisms: up-regulation of IL 1 J3, or imbalance of MMP-91TIMP-1 ratio. CACs from type 1 diabetic patients were assessed in comparison to non-diabetic CACs and based on their M1/M2 profile, significant differences were found such as a decrease in CD163 and CD209 expression. This forms foundations for the study of the phenotypic differences in CACs when they are isolated from or delivered to the diabetic milieu. CACs were also isolated from mice bone marrow and characterised. This is an important step towards delivery of these cells in vivo. This project identified that a switch in phenotype is an important consideration when delivering CACs as a cell therapy into a diabetic environment. It highlights that more research is required to understand how CACs behave in vivo, and the plasticity of their M2-like phenotype, before these cells can be used successfully as a cellular therapy.