Extracellular vesicles (EVs) are emerging as significant mediators of inter-tissue communication by proteins, miRNAs, lipid and metabolites in pathological contexts such as cancer, metabolic and neurological disease, but also in physiological contexts such as exercise. The latter is a particularly interesting finding as it adds to the concept that some of the positive effects of exercise on health can be explained by a complex network of signalling by proteins within or independently of EVs. While these findings implicate EV trafficking as a fundamental biological process, little is known regarding what signals mediate the delivery, or tropism of EVs to specific sites. These questions are especially relevant, not only to provide an integrated understanding of health, but also alongside the recognition that EVs show much potential as carriers of therapeutic agents, given that they protect their cargo from degradation and clearance in plasma. Understanding tissue specific tropism of EVs could well be a considerable step in the development of a drug delivery system that avoids entirely the unwanted off-target effects of systemic drug administration. The proposed work will build on a collective weight of evidence, both from this and other laboratories that suggests that the proteomic signature of an EV determines its organ destination. Examining this experimentally requires the use of high coverage proteomic analyses provided via tandem mass spectrometry. Specifically, the laboratory has developed a ‘pulse chase’ technique whereby tissue specific EV localisation can be tracked using stable isotope labelling of mice. This approach is especially powerful, when combined with targeted analyses of circulating EVs via modern platforms offering phenotype analysis of EV subtypes via a combination of microfluidics, immuno-detection and interferometric imaging. Once specific proteins are identified that mediate tropism to certain tissues, antibodies against these proteins can be used via this system to specifically isolate these EVs and phenotype their cargo in humans.
The objectives of this project are therefore to:- 1) Examine tissue specific uptake of EVs following exercise 2) Validate the protein signature in EVs that mediate tissue specific tropism 3) Identify/validate protein cargo to infer a biological role of this EV delivery in humans. 4) Identify a tissue source of these EVs
Methods used will focus primarily on sample preparation, data acquisition and data analysis associated with quantitative proteomics, with training provided by Dr Martin Whitham (Sport, Exercise and Rehabilitation Sciences). This approach will be supplemented by targeted EV analyses with training and support provided by Dr Paul Harrison (Institute of Inflammation and Ageing).
References Whitham, M. et al. Cell Metabolism 27,237–251