Intraspinal AAV Injections Immediately Rostral to a Thoracic Spinal Cord Injury Site Efficiently Transduces Neurons in Spinal Cord and Brain

Abstract

In the vast majority of studies utilizing adeno-associated virus (AAV) in central nervous system applications, including those published with spinal cord injury (SCI) models, AAV has been administered at the level of the cell body of neurons targeted for genetic modification, resulting in transduction of neurons in the vicinity of the injection site. However, as SCI interrupts many axon tracts, it may be more beneficial to transduce a diverse pool of supraspinal neurons. We determined if descending axons severed by SCI are capable of retrogradely transporting AAV to remotely transduce a variety of brain regions. Different AAV serotypes encoding the reporter green fluorescent protein (GFP) were injected into gray and white matter immediately rostral to a spinal transection site. This resulted in the transduction of thousands of neurons within the spinal cord and in multiple regions within the brainstem that project to spinal cord. In addition, we established that different serotypes had disparate regional specificity and that AAV5 transduced the most brain and spinal cord neurons. This is the first demonstration that retrograde transport of AAV by axons severed by SCI is an effective means to transduce a collection of supraspinal neurons. Thus, we identify a novel, minimally invasive means to transduce a variety of neuronal populations within both the spinal cord and the brain following SCI. This paradigm to broadly distribute viral vectors has the potential to be an important component of a combinatorial strategy to promote functional axonal regeneration.

Global connectivity and function of descending spinal input revealed by 3D microscopy and retrograde transduction

“…AAV serotypes vary widely in their tropism for different types of neurons and their onset of transgene expression (Castle et al, 2016). This appears to be particularly true for retrograde transduction from the spinal cord, as prior tests showed higher efficiency in propriospinal and brainstem populations compared to CST neurons (Jara et al, 2012;Klaw et al, 2013). To and tdTomato signal at all time points, confirming appropriate targeting and transduction of cell bodies directly exposed to AAV2-Retro ( Fig.…”

“…Descending axons converge to relatively small target fields in the spinal cord, and thus a small number of retrograde injections could potentially affect widely distributed supraspinal neurons of origin (Frampton et al, 2005;Nassi et al, 2015). The potential utility of this retrograde approach is well recognized, but has been limited by inadequate efficiency of transduction, particularly for corticospinal tract neurons (Jara et al, 2012;Klaw et al, 2013). Here we harness a recently developed adeno-associated serotype termed AAV2-Retro as a tool to clarify supraspinal connectivity and function (Tervo et al, 2016).…”

Controlling AAV Tropism in the Nervous System with Natural and Engineered Capsids

“…AAV1 appears to be more effective than AAVs 2, 3, 4, 5, or 6 for retrograde transduction of motor neurons following muscle or sciatic nerve injection [56]. Further, AAVs 1 and 5 demonstrate greater retrograde transduction of brainstem than AAVs 2, 8, or 9 following injection of the transected spinal cord [59]. Within the brain, AAV9 is most frequently observed to undergo axonal transport, and is the recommended choice if distal transduction is desired [21, 23, 34, 36, 57, 60].…”

Transduction efficiency of neurons and glial cells by AAV-1, -5, -9, -rh10 and -hu11 serotypes in rat spinal cord following contusion injury

“…[30][31][32][33][34][35][36] Among several animal models of SCI, adult rat contusion models have been established as exhibiting a striking similarity to most human spinal trauma. 37 However, transduction efficacy and cellular tropism of different AAV vectors in the damaged spinal cord have not been systematically examined following contusion SCI.…”