Targeted genetic manipulation of muscle stem cells in vivo towards new treatment strategies against muscular dystrophies

• Applicant: Dr. Jessica Hartmann
• Subject Area: Anatomy and Physiology ; Public Health, Healthcare Research, Social and Occupational Medicine
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 569254922

Our project addresses a significant challenge in gene transfer for both, medical and fundamental research. The overarching objective is to pioneer a gene therapy approach capable of delivering genetic material exclusively to therapy-relevant cells. More specifically, we aim at targeting muscle stem cells (MuSCs) with a focus on safety and high efficiency. This is particularly crucial for treating conditions like muscular dystrophies, where the decline in the maintenance of functional tissues and organs poses a critical factor limiting the quality of life and lifespan. To establish the feasibility of our approach, we aim to develop conditions for in vivo gene correction of MuSCs in a Duchenne Muscular Dystrophy (DMD) mouse model, using engineered Adeno-Associated Virus vectors (AAVs). The gene correction will then spread to muscle fibres through stem cell proliferation and differentiation. As a proof-of-principle, we will leverage the well-established Her2-AAV, which specifically manipulates Her2-expressing cells. We will generate a new mouse model with artificial Her2 expression in MuSCs, which will be then targeted by Her2-AAV. This will allow us to set up experimental conditions for MuSC-specific gene delivery and genome editing. To demonstrate the clinical relevance of our strategy, we will generate AAVs engineered for MuSC-specific targeting through naturally expressed surface molecules. This involves the identification of suitable surface molecules specifically expressed by MuSCs, followed by the generation of high-affinity binders based on designed ankyrin repeat proteins (DARPins) and their display on AAVs. The next phase involves defining the therapeutic potential of MuSC-specific AAVs by performing MuSC-specific gene correction in a DMD mouse model. We will compare our strategy to established unmodified AAVs with a broad tropism. We will address the extent of gene correction in MuSCs throughout the body and its stability over time. By targeting the gene therapy to muscle stem cells directly in vivo, our strategy is distinct from current gene/stem cell therapy methods. By focusing on a rare and long-lived population of stem cells, our approach will allow efficient and long-lasting gene correction in skeletal muscles. Engineered AAVs are de-targeted from sensitive organs (e.g. liver), thereby ensuring the safety of our strategy. The complementary expertise of both partners, on AAV engineering on one hand and MuSC characterisation on the other, guarantees the feasibility of the project. Preliminary experiments have yielded encouraging results, validating proof-of-principle milestones. Successful implementation of our approach in treating DMD opens avenues for applications in other muscle-related conditions. The technology can be extended to a wide variety of disease models, and the new Her2 mouse model allows versatile applications beyond skeletal muscle, thereby fostering advancements in both medical and fundamental research.

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partner: Dr. Brendan Evano