Intervertebral disc degeneration is the main contributor to low back pain

now the leading cause of disability worldwide. Gene transfer

either in a therapeutic attempt or in basic research to understand the mechanisms of disc degeneration

is a fascinating and promising tool to manipulate the complex physiology of the disc. Viral vectors based on the adeno-associated virus (AAV) have emerged as powerful transgene delivery vehicles yet a systematic investigation into their respective tropism

transduction efficiency

and relative toxicity have not yet been performed in the disc

in vivo

. Herein

we used

in vivo

bioluminescence imaging to systematically compare multiple AAV serotypes

injection volumes

titers

promoters

and luciferase reporters to determine which result in high transduction efficiency of murine nucleus pulposus (NP) cells

in vivo

. We find that AAV6 using a CAG promoter to drive transgene expression

delivered into the NP of murine caudal discs at a titer of 10

11

 GC/mL

provides excellent transduction efficiency/kinetics and low toxicity

in vivo

. We also show

for the first time

that the transduction of NP cells can be significantly boosted

in vivo

by the use of small cell permeabilization peptides. Finally

to our knowledge

we are the first to demonstrate the use of optical tissue clearing and three-dimensional lightsheet microscopy in the disc

which was used to visualize fine details of tissue and cell architecture in whole intact discs following AAV6 delivery. Taken together

these data will contribute to the success of using AAV-mediated gene delivery for basic and translational studies of the IVD.