Fight for Sight Grant
Looking at RAGE activation to assess an important pathogenic pathway that modulates inflammatory responses and associated lesion formation in the diabetic retina. This research aims to understand pro-inflammatory pathways that are active in the diabetic retina. In particular, we are focusing on ligand-binding to the receptor for advanced glycation endproducts (RAGE) which is known to evoke pro-inflammatory signalling responses in many non-ocular tissues. We hypothesise that RAGE plays an important role in pro-inflammatory pathway activation and immune cell infiltration in diabetic retinopathy and that blockade of this receptor can protect against neuroglial and microvascular pathology as disease progresses.
The effect of diabetes on EPCs.
Mainly focuses on understanding the cell biology of specialised vascular progenitor cells called endothelial progenitor cells (EPCs) isolated from human peripheral and cord blood. EPCs have an intrinsic capacity to become endothelial cells and we have demonstrated that these cells play an important role in vascular repair and therefore represent an ideal candidate for therapeutic revascularisation. However, in many diseases such as diabetes the resident vasculature and cells are damaged. A key part of my research is to investigate the effect of the diabetic milieu on EPCs. We aim to achieve this by using two experimental systems.
1) By mimicking diabetic conditions in vitro.
2) By isolating EPCs from diabetic patients.
Our aim is to gain a better understanding of EPC dysfunction in diabetes and to discover ways to modulate/repair these cells ultimately for use as a cell therapy for diabetic patients suffering from vascular complications.
Vascular Stem Cell Therapy for Ischaemic Retinopathies
Ischaemic retinopathies, such as branch retinal vein occlusion (BRVO), are major causes of vision disturbance and blindness. Current treatments mainly focus on end-stage disease and do not address the early failure of retinal perfusion. We have previously demonstrated that a small population of vascular stem cells (outgrowth endothelial cells, OECs) can promote revascularisation of the ischaemic retina (Medina et al, 2010, see figure below). The aims of this project are to characterise the cell profile of OECs isolated from the peripheral blood of BRVO patients and evaluate the therapeutic potential of these cells following intra-vitreal transplantation in murine models of ischaemic retinopathy. In addition, we will utilise a porcine model of BRVO in order to evaluate retinal vascular repair and long-term safety following allogeneic /autologous OEC transplants. Ultimately, the outcomes of the preclinical evaluations will allow EPC therapy to be investigated in a BRVO patient-based study.
Prevention of vasopermeability in experimental diabetic retinopathy
Early diabetic retinopathy is characterised by breakdown of the inner blood retinal barrier (iBRB). Vasopermeability and overt iBRB dysfunction has been observed both in patients with diabetes and chemically (streptozotocin) induced diabetic pre clinical models. The exact mechanisms underlying the breakdown of iBRB are largely unknown but are known to lead to endothelial dysfunction and reduction in tight junction integrity.
We have previously shown that the diabetic retina exhibits glial and neurovascular degeneration (McVicar et al, 2011; Curtis et al., 2011; Stitt 2010).
In vivo imaging techniques used routinely in the diabetic clinic have been employed to highlight differences between diabetic and non diabetic Brown Norwegian (BN) rat models in concert with a variety of other methods highlighted below.
We are currently collaborating with GlaxoSmithKline in investigating the capabilities of pre clinical drug formulations in treatment of the effects of diabetes in the retina.
The aim of this project is to utilise in vivo pre clinical models to test efficacy of Lipoprotein associated phospholipase A (2) [Lp-PLA2] inhibitors (developed by GSK) in prevention of breakdown of the inner blood retinal barrier (iBRB). Lipoprotein-associated phospholipase A2 (LpPLA2) is a lipoprotein-bound enzyme involved in inflammation and primarily atherosclerosis. Few reports in the literature focus on its relevance to retinopathy.
The study has several aspects, focusing upon (i) quantitative assessment of barrier function (ii) molecular and (iii) immunological analysis of the effectiveness of our drugs of interest to identify key pathways and cell types involved in regulation of leakage from diabetic BN retina.
It is envisaged that this study will advance to clinical trials stage in the near future.
Paul to insert information
1. McVicar CM, Hamilton R, Colhoun LM, Gardiner TA, Brines M, Cerami A, Stitt AW.
Intervention with an erythropoietin-derived peptide protects against neuroglial and vascular degeneration during diabetic retinopathy. Diabetes. 201160(11):2995-3005.
2. Curtis TM, Hamilton R, Yong PH, McVicar CM, Berner A, Pringle R, Uchida K, Nagai R, Brockbank S, Stitt AW. Müller glial dysfunction during diabetic retinopathy in rats is linked to accumulation of advanced glycation end-products and advanced lipoxidation end-products. Diabetologia. 2011 Mar;54(3):690-8.
3. Stitt AW. AGEs and diabetic retinopathy. Invest Ophthalmol Vis Sci. 2010 (10):4867-74.
4. Canning P, Glenn JV, Hsu DK, Liu FT, Gardiner TA, Stitt AW. Inhibition of advanced glycation and absence of galectin-3 prevent blood-retinal barrier dysfunction during short-term diabetes. Exp Diabetes Res. 2007;2007:51837.
Fight for Sight UK
This research aims to develop a novel approach for the treatment of early stages of ischemic retinopathies based on delivery of endothelial progenitor cells (EPCs) to the ischaemic retina. The concept of such therapy is quite simple: isolate cells from the patient, expand cell numbers in the laboratory and then inject patients’ own cells back into sites of vascular damage. This research will assess each one of these key points in the context of ischaemic retinopathies.
OEC labelled in red directly incorporating into an endothelial tubular structure formed by retinal microvascular endothelial cells labelled in green.
The endothelial progenitors isolated from human blood are called Outgrowth endothelial cells (OECs) and are characterised in this image as being positive for the cytoskeletal protein vimentin in green, nuclei are counterstained in blue with DAPI.