Developing new mature, functional vascular networks in ischemic disease

When blood vessels supplying parts of the heart or other organs become blocked, those organs have a reduced blood supply, so oxygen and other nutrients cannot be delivered in sufficient amounts, and waste products efficiently removed, and the tissue cease to work properly. Tissues can induce blood vessels to regrow into the area, but the new vessels must work properly, i.e. be able to respond to the demands of the tissue, (hold blood in, but allow oxygen and sugars out), and maintain the environment of the tissues (i.e. not allow too much fluid to cross the vessel walls, but to maintain the hydration of the tissues). This process has proved much more difficult to mimic than was originally though ten years ago when this process was first investigated. We have developed a simple system to help us build proper blood vessels, and used them to identify new combinations of treatments that build blood vessels that function the way they would in normal tissues. We intend to use these combination of factors needed to make vessels, and improve on them, test that they work properly, and then try them in models of heart and vessel disease.

The proposal consists of two parts. Part 1 will determine the balance of factors required to provide a physiologically relevant neovasculature in a relatively sparsely perfused tissue. This will be carried out using the rat mesenteric microvascular angiogenesis assay, using adenoviruses expressing VEGF, Ang1, eNOS, netrin, ephrins and DLL4. Angiogenesis, arteriolargenesis (formation of novel arterioles from existing capillaries), and arteriogenesis (expansion of the arterial system from existing arterioles) will be measured using intravital microscopy and confocal imaging of the mesentery. Flow, permeability coefficients (solute permeability, hydraulic conductivity, oncotic reflection coefficient), compliance, and vasoreactivity will be determined. Endothelial intracellular calcium in response to agonists and physical forces in vivo will be measured using intravital dyes perfused into the vessels. This will dissect mechanisms through which vascular remodelling occurs under physiological conditions. Part 2 will transfer this knowledge, built on existing expertise, into animal models of human cardiovascular disease. It will develop and validate novel vectors for the delivery of key remodelling agents to cardiac and skeletal muscle cells. We will use adenovirus (AdV), validated for delivery of genes to these cells, and generate novel viruses expressing Ang1, eNOS and VEGF under control of tissue specific promoters, inducible by hypoxic conditions. These will then be validated in vivo, and applied to disease models, as adenoviruses injected locally. The effect of these viruses on muscle blood flow and cardiac function will be assessed to determine whether the approach of developing normal vasculature is more efficient at recovering animals from cardiovascular insults than angiogenic or arteriogenic agents alone.

Cardiovascular disease is the leading cause of morbidity and mortality in the western world and is dramatically increasing in developing countries. Most cardiovascular disease arises from ischemia due to vessel disease. Vascular remodelling of ischemic tissues can prevent ischemia, and result in restoration of function after an ischemic event. This project will attempt to define how to revascularise ischemic tissues. Moreover, it will bring a new approach - to generate physiologically valid blood vessels functioning normally within the ischemic tissues, more rapidly than is possible naturally. If successful this could benefit millions of UK citizens with cardiovascular disease. The end result of this project, three years after initiation, will be proof of concept studies for increasing cardiovascular function. If this ambitious aim is achieved it will inform translational studies into human. Thus increased health and mobility and reduced morbidity could result from it. Thus the principal beneficiaries would be people with cardiovascular disease, due to improved therapies.
However, as with all research, there will be substantial hurdles if this project proves successful before new treatments are available. The project will also deliver impact in the medium term, within and immediately beyond the time scale of the project. Impact will be both academic and socioeconomic.
Academic impact. The understanding of how vessel growth factors combine to generate functional blood vessels is still in its infancy. We know that VEGFs cause chaotic leaky vessels, that Ang1 recruits pericytes, and eNOS promotes arteriolarisation. The role of netrins, DLL4, and Ephrins are still being elucidated, and while it is clear for example that DLL4 controls sprout patterning, its contribution to permeability, communication, arteriolargenesis and maturation are not well understood. Thus this project will enhance the knowledge economy and scientifically advance the field internationally. The development of novel viral vectors that deliver tissue specific inducible vascular remodelling agents will benefit the community, and will be made widely available. The determination of delivery of viruses will be a key advance over the next few years, and to show a physiological relevance for these vectors will be key. Thus innovative methodologies will be cross disciplinary in their impact. The project will also involve hands on training of new researchers by the PI and collaborators in techniques they have personally developed, and this will enhance the UK science base for translational cardiovascular research. Economically, the translation to humans is apparent and if successful would stimulate private companies to try and put these approaches into humans. We have previously had dealings with gene delivery companies such as Oxford Biomedica, and are working with gene therapy researchers (e.g. at Moorfields) to develop in vivo therapies for human disease. This is an area of intense research and development, and demonstration of its viability for cardiovascular disease would greatly improve confidence for business in this area. The cost to the nation of cardiovascular disease was put at £16bn to the NHS and a total of £29bn in 2006. Generation of therapies based on understanding the physiological consequences of treatment are key. Finally the assays put in place, and in development could be used for more commercial based research, providing additional income to the University.