Stem Cell Exosomes; a system for initiating tissue repair and regeneration in diverse disease settings

Stem and progenitor cells (SCs, PCs) offer enormous potential as therapeutic agents, and early trial data are very promising, revealing dramatic restorative effects in a number of scenarios. However, SC's/PCs act mainly via the secretion of molecules and have a poor survival after transplantation. They can even change once injected, into a variety of different cell types with undesirable behaviors. SC's/PCs secrete small nano-vesicles (exosomes) containing a variety of factors with vascular protective and regenerative actions. Exosomes are essentially miniature yet stable versions of the cell of origin, and they can exert powerful effects on cells and tissues. Exosomes may represent valid therapeutic alternatives to the use of PCs.

The Emanueli lab has proved that the pericardial fluid (PF) surrounding the heart contain exosomes that have very potent vascular regenerative effects, similar or even superior to the PCs derived exosomes. Given cardiovascular disease remains the principal cause of death in the west, there is a huge unmet need here, and this therapy may be amenable to a range of conditions including neurovascular defects as exosomes can pass the blood-brain barrier. The proposal involves establishing a novel system for characterizing exosomes possessing proangiogenic capacities, including PF and PCs and their mechanisms of impact on vascular cells. The final aim will be to identify the "ideal exosome" features to be replicated to design boinspired-therapeutic nanoparticles for vascular regeneration. The PhD student will conduct detailed studies to 1) Establish the best protocols for purifying exosomes from the culture medium of PCs and from the PF that Emanueli obtain (under ethical approval) as leftover material from open heart surgeries (collaborations with Profs Angelini and Caputo - academic cardiac surgeons in Bristol); 2) Define the molecular repertoire associated with the vascular effects of highly purified exosome products, using optimised cutting-edge protein array (SOMAlogic, USA-industrial partners) technologies and RNA-profiling; 3) Test the biodistribution and therapeutic benefit of therapeutically administered exosomes for the repair of blood vessels using in vitro assays and a mouse model of post-ischaemic vascular regeneration (mouse unilateral limb ischaemia).

The project will provide interdisciplinarity, through process technologies for exosome purification, profiling and bioinformatics of vesicle contents, functional and mechanistic assessments through quantitative assays, in vivo biodistribution imaging technologies (positron emission tomography, Cardiff), and proof of efficacy in an ischemia model. Collaborative industrial interactions are in place in relation to the profiling, regulatory system and quality assessment of these processes; with the aim of being in strong position for developing a future clinical product.