Comparing the Efficacy of Adeno‐associated Virus Serotype 9 (AAV9) Mediated Retrograde Transgene Delivery to Hypoglossal (XII) Motor Neurons (MNs) in Mouse Versus Rat Models

Abstract

Previous work by our group shows that AAV9 can robustly transduce XII MNs following direct intralingual injection and subsequent retrograde transport along the XII nerve. The current experiments compared the effectiveness of this approach in commonly studied strains of mouse and rat. In the adult C57BL/6 mouse, delivery of AAV9‐CBA‐GFP (1.20e10vg/μL, 8.33μL) via a unilateral or bilateral injection to the base of the tongue both produced a robust transgene expression in XII MNs as determined by immunohistochemistry (tissues harvested 6 weeks post‐injection). The extent of XII MN transduction was similar with uni‐ or bilateral tongue injection, presumably owing to the small volume of the mouse tongue. In contrast to the murine data, following intralingual delivery of AAV9‐CMV‐mCherry in adult Sprague‐Dawley (SD) rats (1.42e10vg/μL, 1.5 μL or 7.0μL), transgene expression in XII MNs was not detected using either fluorescence microscopy or antibodies against mCherry. Intralingual delivery was repeated in 3 separate cohorts (N=28 total) and MN transduction was never detected. We next tried a direct unilateral injection of AAV9‐mCherry into the main trunk of the XII nerve of adult SD rats (1.42e10vg/μL, 1.5μL). The nerve was injected in the neck, proximal to the point where it bifurcates into medial and lateral branches. At 6 wks post‐injection, we observed clear expression of mCherry in XII MNs detected using immunochemistry. Unexpectedly, MN transgene expression was seen in both XII motor nuclei, despite the unilateral nature of the AAV delivery. We are unaware of any neuroanatomical evidence to suggest that retrograde transport along a single XII nerve would result in bilateral targeting of XII motoneurons, and ongoing experiments are aimed at determining the mechanisms underlying this result. Collectively, these results indicate that retrograde transport of AAV9 following intramuscular delivery may show species variability. Problems with intralingual delivery in the rat were circumvented by direct delivery of AAV9 to the XII nerve.Support or Funding InformationFunding: 1R01HL139708‐01A1 (DDF)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.