Investigating Lipid-siRNA Transport and Gene Silencing Activity in the Rodent Central Nervous System

Abstract

The clinical neurosciences are in the midst a resurgence spurred by the development of new therapeutic modalities. Short interfering RNAs (siRNA) in particular are gaining clinical traction owing to their ability to mediate selective and sustained gene inhibition. Now, a key objective in this quest of developing disease modifying therapies for neurodegenerative disorders is to get siRNA to specific sites and cells in the brain. Direct injection into cerebrospinal fluid (CSF) is the most common route of administration, however, the limited interface between CSF and brain parenchyma poses a considerable challenge for achieving therapeutic effects beyond the superficial layers of the brain. As such, the overarching objective of this dissertation is to enhance delivery to deep brain structures using lipid-siRNA conjugates injected into CSF. We investigated how lipid conjugate structure influences CSF to brain transport mechanisms, regional gene silencing, and cell-specific knockdown. After identifying a suitable candidate in mice, the goal of aim two was to deeply characterize this compound after intrathecal delivery in rats, a model that closely mimics administration in humans. To determine if this construct is truly the most effective, the final aim investigates how structural properties such as linker length and lipid valency influence delivery and knockdown after rat intrathecal injection. Collectively, this work examined properties of lipid-siRNA conjugates that facilitate CSF to brain delivery and generated a promising platform for silencing genes implicated in CNS disorders.