Differential myofiber-type transduction preference of adeno-associated virus serotypes 6 and 9.

Muhammad Riaz,Yotam Raz,Maaike Van Putten,Elizabeth B Moloney,Yvonne D Krom,Joost Verhaagen,Silvere M Van Der Maarel,Vered Raz

doi:10.1186/s13395-015-0064-4

Abstract

BackgroundGene therapy strategies are promising therapeutic options for monogenic muscular dystrophies, with several currently underways. The adeno-associated viral (AAV) vector is among the most effective gene delivery systems. However, transduction efficiency in skeletal muscles varies between AAV serotypes, with the underlying factors poorly understood. We hypothesized that myofiber-specific tropism differs between AAV serotypes.MethodsWe developed a quantitative histology procedure and generated myofiber pattern maps for four myosin heavy chain (MyHC) isotypes. We compared myofiber pattern maps between AAV6 or AAV9 injected tibialis anterior muscle in mice. We correlated MyHC expression with AAV-derived green fluorescence protein (GFP) expression using statistical models.ResultsWe found that MyHC-2x expressing myofibers display a significantly higher preference for AAV transduction, whereas MyHC-2b expressing myofibers negatively correlated with AAV transduction. In addition, we show that AAV9-mediated transduction is enriched in myofibers expressing MyHC-1 and MyHC-1/2a. Moreover, AAV9-mediated transduction can predominantly be predicted by the expression of MyHC isotypes. In contrast, AAV6 transduction can be predicted by myofiber size but not by myofiber types.ConclusionsOur findings identify differences between AAV6 and AAV9 for myofiber-type preferences, which could be an underlying factor for mosaic transduction of skeletal muscle. Adjusting AAV serotype for specific muscle conditions can therefore improve transduction efficacy in clinical applications.Electronic supplementary materialThe online version of this article (doi:10.1186/s13395-015-0064-4) contains supplementary material, which is available to authorized users.

Highlights

Gene therapy strategies are promising therapeutic options for monogenic muscular dystrophies, with several currently underways
Using the prediction model that includes myofiber types and cross-sectional area (CSA), we show that a correlation between green fluorescence protein (GFP) mean fluorescence intensity (MFI) and myofiber types was insignificant in the AAV6transduced muscles but remained significant in the AAV9-transduced muscles
We show that in skeletal muscle, fasttwitch myofiber expressing myosin heavy chain (MyHC)-2b isotype is poorly transduced, whereas those expressing MyHC-2x isotype are preferentially transduced by both AAV6 and AAV9

Summary

Introduction

Gene therapy strategies are promising therapeutic options for monogenic muscular dystrophies, with several currently underways. The adeno-associated viral (AAV) vector is among the most effective gene delivery systems. Transduction efficiency in skeletal muscles varies between AAV serotypes, with the underlying factors poorly understood. We hypothesized that myofiber-specific tropism differs between AAV serotypes. Adeno-associated viruses (AAV) have been successfully engineered as gene-delivery vectors for efficient transduction of post-mitotic cells including skeletal muscles [1]. Several AAV serotypes with variable tropism have been developed for superior transduction [3, 4], and most of these have been suggested for. Preference of AAVs for myofiber types and its contribution to overall transduction efficiency has not been thoroughly investigated. We suggest that myofiber types of skeletal muscle can play a role in the selection of AAV serotypes for effective transduction and treatment

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Conclusion