Engineered muscle tissues with enhanced maturation enable the identification of clinically relevant rAAV products

Developing in vitro models that recapitulate both the structure and function of native human tissues is crucial for a better understanding of pathophysiology and for improving the reliability of preclinical studies. Here, we demonstrate that engineered muscle tissues derived from human pluripotent stem cells can serve as an in vitro platform for gene therapy. Recombinant vectors derived from the adeno-associated virus (AAV) transduce engineered muscle tissues with high efficiency and in a dose-dependent manner, allowing long term assessment of transgene expression in a human cellular context. We next used this model to conduct a comparative analysis of 8 natural AAV capsids and showed that their relative efficiency depends on engineered muscle tissue maturation level. In more mature tissues subjected to uniaxial mechanical stretch, AAV9 performed better, which demonstrates the importance of differentiation conditions on the transduction process. Finally, our model also confirmed the higher efficiency of artificial MyoAAV variants specifically developed to have an improved muscle transduction. Altogether, this work highlights the potential of human engineered muscle tissues in the evaluation of AAV-mediated transgene expression and its functional impact on muscle phenotypes.