Cell-derived matrices mechanics as a functional read-out in Collagen VI-related Congenital Muscular Dystrophies

Collagen VI-related congenital muscular dystrophies (COL6-RDs) are a set of neuromuscular conditions caused by pathogenic variants found in any of the three COL6 genes. The phenotypic expression of the disease does not directly correlate with the genetic background producing an overlapping spectrum of clinical phenotypes that goes from the mild Bethlem myopathy (BM) to the severe Ulrich congenital muscular dystrophy (UCMD). Diagnosis includes genetic confirmation of the disease and categorization of the phenotype based on maximum motor ability. The development of new tools able to identify phenotype traits can significantly contribute to the diagnosis and prognosis of COL6-RDs. Mutations occurring in COL6 genes result in deficiency or dysfunction of COL6 incorporated into the extracellular matrix (ECM) of connective tissues, affecting its fibrillar structure. Our research group has established personalized pre-clinical models of COL6-RDs based on cell-derived matrices (CDMs), which allowed the direct observation of the fibrillar organization of the ECM in samples derived from patients, and to compare features amongst different phenotypes. Here, we have characterized the mechanical properties of CDMs from patients using atomic force microscopy-based force spectroscopy (AFM-FS). We observed that the elastic modulus (E) varies with the phenotype, and that it correlates with COL6 organization in the CDMs. We additionally used AFM-FS to evaluate matrices derived from genetically edited cells, which resulted in E value restoration compared to control samples. Altogether, these results anticipate the potential of mechanical analysis of CDMs as a complementary clinical tool, providing phenotypic information about COL6-RDs and their response to gene therapies.