Exosomes - circulating cardioprotective nanoparticles

Coronary artery disease has become one of the biggest challenges facing health care systems around the world. In 2004, ischaemic heart disease was responsible for 7.2 million deaths worldwide, making it the leading cause of death. Myocardial infarction (heart attack) is the acute event that causes mortality and morbidity in patients with coronary artery disease. Currently early reperfusion (restoration of normal coronary flow), remains the mainstay of treatment for those suffering an acute heart attack or those at risk of potential injury to their heart muscle. However, though early reperfusion is critical in limiting the size of the damage to the heart muscle and hence improving patient outcomes with regards to mortality and cardiac function, paradoxically reperfusion also causes injury to heart muscle in what is termed "lethal reperfusion injury" (myocardial cell death). Therefore, finding ways to reduce lethal reperfusion injury is a vital step in the overall long term management of patients presenting with myocardial infarction or presenting with symptoms of coronary artery disease.

With this in mind we are investigating treatments that will allow the heart to withstand the damage from a heart attack. We have had a long term interest in the hearts own endogenous ability to protect itself from severe injury and have exploited these endogenous mechanisms in our attempts to find new ways to protect the heart muscle from the consequences of severe injury. In this regard we are investigating a completely novel area which we believe may have exciting potential and involve a paradigm shift in our thinking with regard to cellular protection. We have recently purified small particles called "exosomes" from healthy blood. Exosomes have been generating a great deal of scientific interest recently, because they appear to be able to transmit "messages" from cell-to-cell. So far, however, there has been very little study of exosomes in healthy individuals, or of the effect of healthy exosomes on the heart. In our pilot studies, we have found that exosomes purified from healthy animals can protect the heart against the damage of a heart attack.

We are now proposing to investigate the mechanism of this cardioprotection. This can be potentially important as: 1) it will provide new information about exosomes in normal cardiovascular health, 2) help us to identify novel ways of protecting the heart, and, 3) potentially lead to new treatments in which exosomes are used to protect the hearts of patients at risk of a heart attack.

For these experiments we will require specialized equipment. Exosomes, which are approximately the size of viruses, cannot be seen using normal microscopy, but using laser-diffraction and particle tracking we will be able to measure the size and concentration of exosomes in different preparations. Although we can't see exosomes directly, we can evaluate their effects on cells in the heart. We use a technique called multi-photon microscopy, which allows us to obtain high-resolution images of the cells inside living tissue. This allows us to discover what happens to the cells of the heart after treatment with these nanoparticles.

Exosomes are like tiny shuttles, and contain proteins which we believe are responsible for protecting the heart. We aim to catalogue the entire protein content of healthy exosomes, and by process of elimination, determine which ones contribute to cardioprotection.
Our research will also be directed at determining whether exosomes represent a viable method of cardioprotection in patients, experiencing heart attacks. Should our research lead to the discovery of such therapeutic agents the potential to decrease in-hospital stay, reduce future hospital admissions and decrease adverse cardiac events and all-cause mortality, would directly benefiting patients and the NHS. In addition any improvement in morbidity would be expected to improve the quality of life of these patients.

Exosomes are nanometre-sized, lipid membrane vesicles that ferry proteins and other components through the circulation and appear to have a signalling role. Exosomes circulate in the blood of healthy individuals, but their properties and purpose are virtually unknown. In pilot data we have isolated exosomes from healthy rat plasma and shown that they are cardioprotective in a Langendorff isolated, perfused, rat heart system. Our objective is to characterize these exosomes, to determine their mechanism of cardioprotection, and to evaluate the potential of circulating exosomes as an autologous therapeutic agent. This will be achieved using established techniques for exosome purification and analysis which require the use of a preparative ultracentrifuge and Nanosight equipment for determining particle size distribution and concentration. The Langendorff isolated heart preparation will be used extensively for evaluating cardioprotection, and confirmed using our established in vivo rat MI model. A recovery model will be utilized establish the importance of this protection on a longer time-scale relevant for patients.

Protein content of plasma exosomes will be determined using proteomics and Western blotting. This will inform design of experimental protocols to identify the mechanism of cardioprotection. Molecular characterization of exosomal interaction and/or fusion with the heart will be achieved using multiphoton microscopy of exosomes labelled with fluorescent nanodots. We have already identified one candidate cardioprotective protein (HSP70) and its role will be investigated using a HSP70-neutralizing antibody developed by Prof Multhoff (Munich). Investigation of the cardioprotective component of exosomes may lead to identification of novel cardioprotective pathways or proteins. We stand ready to fully exploit other lead proteins and cardioprotective pathways identified, in terms of potential patents, publications and further experiments.

Business would be a potential beneficiary: We are in discussion with UCL Business regarding the application of patents for our research. If successful, this has the potential to attract R&D investment from global business. It may lead to the commercialisation and exploitation of knowledge gained about exosomes. Pharmaceutical companies are continually searching for new directions in terms of both drug discovery and as a means of drug delivery. Exosomes could offer both and should we be successful we would expect significant interest from both Pharma as well as Device companies.

Patients would be a potential beneficiary: It is difficult to be precise at this early stage, since we are investigating a novel process of cardioprotection, but we are optimistic that it will advance health and well-being in the long-term, by leading to the identification of novel means of cardioprotection. If this is indeed the case than the beneficiaries from our research will be the patients who are at risk of having a heart attack. Coronary artery disease has become one of the biggest challenges facing health care systems around the world. Myocardial infarction (heart attack) is the acute event that causes mortality and morbidity in patients with coronary artery disease. Our research is directed at determining whether exosomes represent a viable method of cardioprotection in patients, experiencing heart attacks. Should our research lead to the discovery of new therapeutic agents the potential to decrease in-hospital stay, reduce future hospital admissions and decrease adverse cardiac events and all-cause mortality, would directly benefit patients and the NHS. In addition any improvement in morbidity would be expected to improve the quality of life (QOL) of these patients.

Medicine/science would be a potential beneficiary: Since its emergence in the 1980's, the area of nanotechnology has created huge scientific interest. One of nanotechnology's biggest impacts could be in the field of medicine with new discoveries in terms of therapy and drug delivery.

Public Sector, Schools, Charities etc would be a potential beneficiaries: Our recent interest in the area of exosomes clearly fit into the overall ethos of this area and as such and data derived from our studies would have interest to a broad range of beneficiaries including academia as a whole, the public sector (ie NHS), schools, as well as the Third Sector such as Charities including the British Heart Foundation, a major supporter of our research.

Media would be a potential beneficiary. Should our studies prove successful the knowledge would initially be disseminated in peer review papers but would also be of direct interest to the public and as such we would envisage media interest as well as engagement with public by means of public lectures, conferences, seminars and workshops.

This area of research is extremely novel and would be seen as leading edge and if successful would be of direct benefit to our Institution (UCL), the MRC as well as the National benefit by being one of the leaders/pioneers in an area of research which is starting to be of interest in all branches of medicine.