Exososomal CNS-Delivery of Therapies for a Lysosomal Disorder

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ABSTRACT Lysosomal storage diseases (LSDs) are genetic disorders caused by pathogenic variants in genes encoding enzymes that are essential for the lysosomal function. These inborn organelle diseases have a cumulative incidence of ~1/2,000-3,000. LSDs have a broad clinical spectrum, mostly associated with a progressive neurodegenerative course, resulting in severe disability and death. The current advances achieved in LSD treatment are exemplified by the enzyme replacement therapy (ERT), which consist of weekly or biweekly intravenous administrations of the recombinant enzymes. Although generally well-tolerated, ERT showed limited biodistribution in the central nervous system (CNS). ERT agents are large molecules, and so they are incapable of crossing the blood-brain barrier (BBB). The lack of reliable and efficacious delivery across the BBB severely limits the ERT and other therapies to treat neurological symptoms. Hence, the development of delivery strategies for therapeutic agents for LSDs is an urgent and unmet need. Unfortunately, 98% of small- molecule drugs and every biological agent, including proteins, cannot cross the BBB. Numerous CNS delivery strategies have been developed to overcome the often stated ‘problem-behind the problem’ of many neurological conditions. Recent studies have shown that exosomes provide a physiological means to deliver proteins or miRNA across BBB. Exosomes, “fingerprints of the cell,” are extracellular nanovesicles are released by cells into the circulation and bodily fluids, displaying distinct cargo profile dependable upon their cellular origin. In 2018, clinic-approved exosomes started to be produced under GMP standards. We hypothesize that exosomes are therapeutic nanovesicles that allow penetration through the BBB to treat neuropathic forms of LSDs. We established a murine neural cell line that secretes neural-derived exosomes containing specific lysosomal enzymes. Leveraging the unique resources we have built over the years, along with our work investigating neurological LSDs and function of exosomes, we will address the following aims: Aim 1. Characterize and further improve the exosomal production from an established murine neural cell line derived from a Twitcher (Twi) mouse model of a severe neurological LSD. We will optimize the production of exosomes from neural immortalized Twi murine cell line stably expressing human GALC (galactocerebrosidase). Using targeted proteomics and sphingolipidomics, we will characterize neuronal exosomes Aim 2. Examine the therapeutic potential of neural-derived exosomes as a CNS- delivery system in the Twitcher, mouse model. We will examine the biodistribution and efficacy of neural- derived exosomes in the neurological course using Twi mice. As mediators of intercellular communication and surrogates of intracellular changes in pathological states, exosomes become a reliable source to deliver therapies to LSDs. This proof-of-principle study will reveal exosomes as a powerful and robust CNS- ‘nanovesicle-delivery’ strategy of therapeutic applications to treat neurodegenerative disorders.