The potential importance of Stromal Derived Factor-1 in the protection and repair of myocardium following simulated ischaemia-reperfusion injury

Following a heart attack, the restoration of blood flow to injured heart muscle can itself inflict injury, known as Ischaemia-Reperfusion Injury (IRI). Remote Ischaemic Conditioning (RIC) describes the phenomenon whereby the brief occlusion and restoration of blood flow to body tissues remote from the heart can protect heart muscle from IRI. However, despite promising results from experimental studies, the mechanism of action remains elusive. Recent attention has turned to a small protein called Stromal Cell-Derived Factor 1 (SDF-1), which is thought to have a dual function. Firstly, SDF-1 is thought to activate a protective mechanism that has previously been implicated in RIC, namely the Reperfusion Injury Salvage Kinase (RISK) pathway. Secondly, it is thought to play a role in attracting stem cells to the site of injury. It is therefore feasible that SDF-1 both protects heart muscle from IRI and helps repair it after injury, thus reducing heart failure. The key goals of my research are to demonstrate whether heart muscle can be protected from IRI in the presence of SDF-1 in animal models, and to ascertain the benefit of SDF-1 in preventing heart failure.

OBJECTIVE
Following ST-elevation myocardial infarction (STEMI), the therapeutic restoration of blood flow can itself inflict injury, known as Ischaemia-Reperfusion Injury (IRI). Remote Ischaemic Conditioning (RIC) describes the phenomenon whereby the application of brief non-lethal ischaemia and reperfusion to tissue remote from the heart protects the myocardium from a lethal episode of IRI. However, the mechanism remains elusive. The objective of this research is to elucidate this mechanism.

AIMS
Stromal Derived Factor-1-alpha (SDF-1) has been identified as a prime candidate and this application attempts to evaluate its role in the setting of IRI. SDF-1 is thought to have a dual function. Firstly, it regulates diverse cell functions that have previously been implicated in myocardial protection from IRI seen in RIC, namely the Reperfusion Injury Salvage Kinase (RISK) pathway. Secondly, it is thought to play a role in the trafficking of endothelial progenitor cells from bone marrow. It is therefore feasible that SDF-1 both protects the myocardium from IRI via the RISK pathway and contributes to its repair by homing stem cells to damaged myocardium. The key aims of my research, therefore, are to investigate the importance of SDF-1 in RIC acutely and to use a model of post-MI heart failure to investigate long-term benefit of increased SDF-1.

METHODOLOGY
Physiological in vivo and ex vivo rat and mouse models of myocardial IRI will be used in addition to in vitro cell models of hypoxia-reoxygenation injury, and a range of molecular biology techniques including Western blot analysis. Data will be analysed by one way ANOVA and Fishers' protected least significant difference test for multiple comparisons.

SCIENTIFIC AND MEDICAL OPPORTUNITIES
Finding the factor(s) responsible for the mechanisms of RIC is paramount for maximising its potential in patients undergoing both coronary artery bypass surgery and those presenting with STEMI.

There are expected to be a number of potential beneficiaries from this research, including academic peers, commercial organisations, the wider public, and most importantly, the patient.

ACADEMIC IMPACT
As described above, this research is expected to benefit basic and clinical scientists in the Hatter Cardiovascular Institute working on SDF-1. In addition, collaboration with other cardiovascular researchers, both nationally and internationally, will benefit both parties.
Outside of groups carrying out similar studies, this research is expected to be of interest to and benefit to wider clinical circles. We would hope to benefit, in particular, interventional cardiologists interested in the mechanisms of cardioprotection, and many other specialties who stand to gain from a better understanding of cardiovascular medicine.

Alongside direct beneficiaries of our research, indirect benefits are expected in relation to the generation of a custom antibody against active SDF-1. This has not yet been undertaken for our neo epitope of interest. This is a new and innovative technique that will benefit both the commercial company responsible and the academic community.

The Hatter Cardiovascular Institute often engages with other sectors including the public and business sector as well as local schools. If the research is relevant and appropriate, it will be disseminated to these groups.

Finally, a successful application would also contribute to the development and training of the applicant as a clinical academic, who would be able to contribute to cardiovascular science and clinical cardiology in his future career. In addition, he will acquire skills in research and statistics that will facilitate future clinical research, including a better understanding of cardiovascular morbidity and mortality.

ECONOMIC AND SOCIETAL IMPACT
In the short term, our research will be of help to the manufacturers of the materials and consumables outlined in our proposal. Specifically, the animal ventilators, data acquisition and analysis system, chemicals, drugs, reagents and inhibitors, and animal costs will all benefit United Kingdom based companies.

However, most importantly it is hoped that the outcome of this research will be of direct relevance to the patient at risk of myocardial infarction. If SDF-1 fulfils its potential as a cardioprotective agent it will alter our approach to the management of cardiovascular disease, combining current emphasis on the restoration of blood flow with protection of downstream myocardium. This will alter practice and policy in cardiology, and potentially vascular surgery and neurology, where reperfusion of ischaemic tissue is commonplace. In the longer term our research may benefit the cohort of patients presenting with ST-elevation myocardial infarction undergoing primary PCI, and potentially patients undergoing cardiac surgery and elective PCI. Circulatory disease remains the biggest cause of death in the UK, many of whom are economically active, and it is hoped that in addition to improving quality of life, health and well-being, this research will avert some of the opportunity costs.

Science and research are recognised as major contributors to prosperity in the UK and this application seeks to support both a hypothesis and an applicant with the potential to strengthen the UKs standing and competitiveness in the international science community.