DETERMINING THE ROLE FOR EXOSOMES DURING CELLULAR SENESCENCE AND AGEING

The number elderly population in the UK has dramatically increased in the last few decades. As a consequence, conditions associated with ageing, such as cancer, cardiovascular and neurodegenerative diseases, are having a huge impact on the public health system and the UK economy. It is therefore imperative to promote research that will improve our understanding of the mechanisms implicated in the maintenance of health across life. The primarily hallmark of ageing is the decline in the tissue homeostasis. However, the precise basic and cellular mechanisms implicated in the ageing process are not well established, hindering the advances in understanding how healthy ageing happens.

The organs and tissues in our body are formed by a vast number of cells, which altogether co-ordinate their actions for our body to function properly. However, a number of "abnormal" cells have been found in tissues derived from old patients. These particular cells suffer a growth arrest or lack of proliferation termed "senescence", which is thought to affect how the tissue functions. Senescent cells fail to proliferate, but they manage to communicate with their neighbour cells, mainly through the release of inflammatory proteins. In this application we will focus on a different way of intercellular communication during senescence, the release of small extracellular vesicles, called exosomes. Exosomes contain biological material in the form of proteins, RNA or small RNAs called microRNAs. Exosomes can release their inside content into particular cells, which as a consequence induce phenotypic changes in the target cells. Our preliminary data show that senescent cells secrete a high number of exosomes and, as a consequence, induce senescence in neighbouring cells. This application will explore the molecular mechanisms by which exosomes released from senescent cells induce senescence in neighbouring cells. We will also determine the inside content of these particular exosomes, in addition to the inside content of exosomes secreted by cells donated by elderly patients, to study similarities and differences between both models. Finally, we will focus on the functionality of exosomes using three-dimensional models of skin culture. During this application we will use a range of approaches, including human cell culture, high-resolution imaging techniques, state-of-the-art proteomics and genomics and an in vitro human skin model. Altogether, this project will help understand the mechanisms by which exosomes regulate normal ageing and it will allow to improve human health and wellbeing throughout life.

The overall hypothesis of this project is that exosomes secreted by senescent and ageing cells play a key role in inducing senescence and ageing in a non-cell autonomous fashion. The secretion of inflammatory proteins, termed senescence-associated secretory phenotype or SASP, has been described as the main mechanism for senescent cells to communicate with their environment. However, most cells also signal through the release of extracellular vesicles (EV) termed exosomes, but little is known of their role during senescence or ageing. Exosomes contain a subset of proteins, lipids and nucleic acids that can change in composition depending on the parent cell. Our preliminary data show that senescent cells release a higher number of exosomes than proliferating cells. We show that exosomes from senescent cells express the cell adhesion protein integrin beta 3 and can induce senescence in other cells. This application proposes to study the mechanism(s) by which these exosomes induce senescence by studying the role of integrin beta 3 and investigating the role that other kinases play. We will also determine the cargo of exosomes from senescent and elderly patient cells and study their function using human skin organotypic models. Altogether, we propose a programme of research that aims to determine the role of exosomes secreted by senescent and old patient-derived cells in modulating the behaviour of cells in the surrounding environment. Data obtained from this proposal will give an extensive overview of the basic mechanisms for exosome function during ageing and senescence. In fact, it will advance our knowledge of the biology of normal ageing and will lead to approaches to improve healthy ageing.

There are currently more than 10 million people in the UK over 65 years old, with an estimation for a significant increase within the next few years. The UK's ageing population has considerable consequences for public spending and the UK economy, due to the development of a number of age-associated diseases, such as cardiovascular, neurodegenerative and cancer. Consequently, there is an urgent need to promote research that will lead to a healthy lifespan across the entire life course.

The output of this piece of research will benefit a large number of sectors within the UK:

Academic and researcher peers will benefit from this proposal by providing new knowledge and basic scientific advancement of intercellular communication mechanisms during senescence and ageing. This will include not only peers within the immediate professional circle, but also professionals within other research areas such as cancer, immunobiology and fibrosis, where senescent cells have been identified in vivo.

Pharmaceutical companies will benefit from this project if we discover new kinases regulating exosome-induced senescence. We hypothesise that blocking the long-term accumulation of senescent cells induced by exosomes release and spread will improve healthy ageing in humans. In fact, the Van Deursen Lab has successfully demonstrated in animal models of premature ageing, that the elimination of senescence cells alleviates different ageing-related phenotypes.

The general public will also benefit from this research if it leads to the development of therapies improving healthy ageing and increasing the quality of life throughout our lifecourse. It will also benefit by increasing the public awareness and the scientific understanding of how healthy ageing occurs and by explaining how basic research impacts on the UK society and economy. In the event of finding very specific cargo contents in exosomes secreted by senescence cells and age-derived fibroblasts, future investigations will lead to the discovery of specific ageing biomarkers in a relatively short-term.

Our research will provide the UK Life sciences community with highly trained and exceedingly skilled scientists who will have received training in public engagement and have a clear emphasis on keeping the public informed about research discoveries in this field, as this is a QMUL number one priority. This is a benefit to the UK Life sciences sector by increasing UK Life sciences expertise, which will eventually help the UK science economy.

The UK Economy will also greatly benefit from the results obtained from this application. There are currently a large number of elderly people in the UK and, more than 65% of the Department for Work and Pensions benefits expenditure goes to this sector. This poses a huge burden on the UK economy and the NHS sector. Our research will lead to understanding the basic mechanism(s) for how normal and healthy ageing occurs and it will help promote healthy ageing and avoid the overuse of the NHS public spending.