P.61 Imaging Mass Cytometry reveals new clues to understand the pathogenesis of Becker muscular dystrophy

Abstract

Muscular dystrophies are genetic diseases characterised by muscle fiber loss and its replacement by fibrotic and adipose tissue. Several cell types, including macrophages and fibroadipogenic precursor cells (FAPS) interact with degenerative muscle fibers locally in what is known as the degenerative niche. Recent technological advances known as spatial biology allow dissecting cell-to-cell interactions in vivo using samples of tissue, although this has not been applied to human muscle tissue yet. We analysed muscle biopsies of controls and patients with Becker muscular dystrophy (BMD) at early, moderate and advanced stages of degeneration using Hyperion Imaging Mass Cytometry (IMC). We labelled single sections of the biopsies with 40 markers labelling different components of the muscle structure. We developed a deep learning algorithm to analyse the images and studied changes in the composition and spatial correlations of the different markers across disease progression. We included 2 control and 8 muscle biopsies of BMD. We observed a progressive increase in the amount of collagen-I and III, that significantly correlated with the amount of CD68+ macrophages (R=0.93 and R=0.94), most of them positive for the M2 marker CD206. Fat and collagen I surrounded vessels during the first stages of disease progression, substituting muscle fibres in later stages. We observed a negative correlation between regenerative muscle fibers and collagen-I (R=-0.83) and with CD68 cells (R:-0.90). We also observed a modification in the number of satellite cells in the biopsies across disease progression. IMC enables the study of changes in muscle structure along disease progression in patients with muscular dystrophies establishing spatio-temporal correlations opening the door to confirm and understand new potential pathogenic pathways in vivo in human samples.