Muscle Organoids: A Muscle Construction Kit for Modeling Disease Mechanisms in Sporadic and Hereditary Muscle Disorders In Vitro.

• Applicant: Dr. Felix Kleefeld
• Subject Area: Molecular and Cellular Neurology and Neuropathology ; Experimental Models for the Understanding of Nervous System Diseases ; Orthopaedics, Traumatology, Reconstructive Surgery
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 552757590

Myopathies represent a heterogeneous group of inherited and sporadic disorders affecting skeletal muscle, including hereditary muscular dystrophies and idiopathic inflammatory myopathies. Current therapeutic options, especially for muscular dystrophies, are limited due to complex and only partly understood pathophysiological mechanisms, which are incompletely represented by existing models such as 2D cell culture and animal models. This project aims to contribute to the establishment of innovative, complex, three-dimensional cell culture models – muscle organoids (MO). In a proof-of-concept approach, two common myopathies (hereditary dysferlin-associated limb-girdle muscular dystrophy and sporadic inclusion body myositis) will be modeled in vitro using this new technique. Both diseases are characterized by inflammatory changes, evident as the infiltration of immune cells into muscle tissue. Co-culture systems are needed to model this interaction between the immune system and muscle cells. This project focuses on adult-onset muscle diseases, where phenotypic and molecular characteristics (e.g., mtDNA deletions) become apparent later in life. This necessitates using adult stem cells (satellite cells) derived from muscle biopsies as the starting cell population for establishing the MO, as induced pluripotent stem cells (iPSCs) are unsuitable for this purpose. To address this issue, adult satellite cells obtained from muscle biopsies will be used as the starting cell population to establish the MO. The MO will be derived from adult muscle stem cells obtained from patients with autosomal-recessive limb-girdle muscular dystrophy (LGMD) type R2 dysferlin-related and patients with inclusion body myositis (IBM). The validity of the MO as disease models will be assessed through histological, transcriptomic, and ultrastructural examinations, as well as investigations of mitochondrial dynamics at predefined time points. Subsequently, the MO will be co-cultured with immune cells (PBMCs) obtained from patient blood samples. Co-culture models involving immune cells have been established in the context of tumor organoids, allowing for adopting relevant protocols. The effects of co-culture on the phenotype of the MO will be examined, focusing on mitochondrial metabolism. In summary, this project combines two innovative approaches: the establishment of muscle organoids as models for adult-onset diseases using adult stem cells derived from muscle biopsies and an exploratory immune cell co-culture model to investigate the interaction between the immune system and muscle cells in vitro, opening avenues for targeted in vitro drug testing in the future.

• DFG Programme: WBP Fellowship
• International Connection: United Kingdom
• Host: Professorin Rita Horvath, Ph.D.