MicroRNA-based targeting strategies enable AAV-mediated, tissue-selective gene expression in adipose tissue and skeletal muscle of mice.

Functional validation of therapeutic concepts-including understanding a target protein's mode of action in disease-relevant tissues-is a critical component of early drug discovery research. Tissue selectivity of recombinant adeno-associated viral vectors (AAVs) is an important property for both gene therapy and the modulation of target genes in model organisms, to investigate protein function and signaling pathways in specific cell types and tissues. However, while many target tissues can be transduced efficiently by selected capsids, achieving tissue specificity remains challenging in certain contexts. In this study, we compared different microRNA (miRNA)-based strategies to transcriptionally restrict AAV expression to either adipose tissue or skeletal muscle. Our findings demonstrate that liver-specific miR122 effectively suppressed AAV9-driven liver expression, while preserving adipose tissue targeting efficiency. Similarly, AAVMYO, in combination with a muscle-specific promoter and target sites for miR208a, confined transgene expression to skeletal muscle, while successfully de-targeting the liver and, importantly, the heart. Notably, both approaches outperformed conditionally self-silencing constructs that utilized artificial miRNAs (amiRs) driven by liver (LP1)- or heart (troponin T)-specific promoters. In summary, we expand the AAV toolbox by introducing expression cassette designs that enable specific expression in adipose tissue and skeletal muscle, thereby facilitating mechanistic studies in metabolic and muscle disease research.