Blocking vascular permeability by targeting CD148; a novel approach for treating retinopathy

Background: Diabetic retinopathy is a complication of diabetes caused by high blood sugar which causes permeabilisation of blood vessels at the back of the eye resulting in the leakage of blood and fluids. As the condition progresses angiogenesis occurs leading to the formation of more defective blood vessels exacerbating the condition. Diabetic retinopathy affects up to 80% of all diabetes patients who have had the disease for 20 years or more. Although good management of blood sugar levels can significantly alleviate the severity of this condition, when treatment is necessary both surgical and drug based therapies are used. The administration of anti-VEGF drugs via intra-vitreal injection on a monthly basis is commonly prescribed for this condition. However, there are several concerns with the use and efficacy of this approach, not least the high level of patient non-response to this therapy (>45%) and the expense of producing and administering these drugs. There is therefore a need to identify novel therapeutic targets with the aim of improving or offering an alternative to existing treatments.
Research Question: We have identified a novel pathway which when stimulated blocks vascular permeability responses to known inducers of this response such as VEGFA and bradykinin. The pathway acts through the stimulation of a protein tyrosine phosphatase receptor (CD148) on the surface of endothelial cells. We have already identified a peptide QM107 which interacts with CD148 and blocks vascular permeability, however our preliminary data would suggest that recombinant proteins derived from the extracellular domain of CD148 have an even more efficacious effect in inhibiting vascular permeability and angiogenic responses. The purpose of this project is to explore this further and in so doing answer the following questions:
1) What is the minimum peptide sequence derived from CD148 required to achieve inhibition of vascular permeability?
2) Is this more effective than QM107?
3) Can the CD148 derived peptide also block angiogenesis?
4) Does this peptide work in an in vivo model of diabetic retinopathy?
Techniques: This project will encompass a broad range of techniques which are routinely used in the Whiteford lab. Molecular Biology and protein purification approaches will be used, with some bioinformatics. Permeability assays such as the Myles assay will be used in vivo, as will a novel approach for visualisation vessel leakage in murine eyes. In addition cell based assays for angiogenesis and vascular permeability will also be employed.