Identifying naturally occurring adeno-associated virus serotypes that transduce mouse skeletal muscles fibro-adipogenic progenitors in vivo

Topic:

Translational Research

Poster Number: P243

Author(s):

Fady Guirguis, BS, NNDCS, NINDS, NIH, Bethesda, MD, USA./The Dubowitz Neuromuscular Centre, GOS ICH, UCL, London, UK., Véronique Bolduc, National Institute of Neurological Disorders and Stroke, Astrid Brull, PhD, Neuromuscular and Neurogenetic Disorders of Childhood Section, NINDS, NIH, Bethesda, MD, USA., Huachun Liu, PhD, Grousbeck Gene Therapy Center, Mass Eye and Ear, Harvard Medical School, Boston, MA, USA., John A. Chiorini, PhD, Adeno-Associated Virus Biology Section, NIDCR, NIH Bethesda, Maryland, USA., Nerea Zabaleta, PhD, Grousbeck Gene Therapy Center, Mass Eye and Ear, Harvard Medical School, Boston, MA, USA., Luk H. Vandenberghe, PhD, Grousbeck Gene Therapy Center, Mass Eye and Ear, Harvard Medical School, Boston, MA, USA., Haiyan Zhou, PhD, University College London, Francesco Muntoni, MD, University College London, Carsten G Bönnemann, National Institute of Neurological Disorders and Stroke

Collagen VI-related muscular dystrophies (COL6-RDs) present with congenital or early-onset progressive muscle weakness and joint contractures and may lead to loss of ambulation and respiratory failure by early teen years. COL6-RDs are caused by pathogenic variants in the genes encoding collagen VI (COLVI), which is an extracellular matrix protein that plays multiple critical roles in skeletal muscles. In mature muscle, COLVI is primarily synthesized by fibro-adipogenic progenitor cells (FAPs)—an interstitial stromal cell type. Currently, there are no specific therapies for COL6-RDs. A major challenge to overcome is the effective delivery of therapeutics to FAPs in vivo. Here, we screened 9 clinically relevant naturally occurring adeno-associated virus (AAV) serotypes to identify serotypes capable of transducing mouse skeletal muscles FAPs efficiently and selectively in vivo.
We intravenously (IV) injected 7-9-week-old Cre/FAPs reporter male mice (Ai14;PDGFRαEGFP) with each serotype at 1.5E12 vector genomes (VGs)/mouse (n=3/serotype). Tissues were collected 4 weeks post-injection, and the percentage of transduced cells was quantified using fluorescence-activated cell sorting.
We assessed the 9 AAVs’ efficiencies at transducing FAPs and non-FAPs in skeletal muscles and the liver. We identified a serotype that was significantly more efficient at transducing FAPs in both tissues than most serotypes, while its transduction of non-FAPs was no different from the majority of the other serotypes in those tissues. These results suggest this serotype has a selectively greater transduction efficiency towards FAPs in different tissues compared to other serotypes. Besides the top-performing serotype, we identified 3 moderate FAP-transducing serotypes that were still significantly more efficient at transducing muscle FAPs than the remaining 5 poor-performing serotypes.
We are currently quantifying the number of VGs per diploid genome, characterizing further the serotypes’ biodistribution, and identifying the AAV capsid motifs specific to the top-performing serotypes to inform rationally designing potentially more efficient and selective FAPs-targeting capsids.