ABSTRACT
Purpose: It is challenging to deliver the full-length dysferlin gene or protein to restore cellular functions of dysferlin-deficient (DYSF-/-) myofibres in dysferlinopathy, a disease caused by the absence of dysferlin, which is currently without effective treatment. Exosomes, efficient membranous nanoscale carriers of biological cargoes, could be useful. Experimental design: Myotube- and human serum-derived exosomes were investigated for their capabilities of restoring dysferlin protein and cellular functions in murine and human DYSF-/- cells. Moreover, dysferlinopathic patient serum- and urine-derived exosomes were assessed for their abilities as diagnostic tools for dysferlinopathy. Results: Here we show that exosomes from dysferlin-expressing myotubes carry abundant dysferlin and enable transfer of full-length dysferlin protein to DYSF-/- myotubes. Exogenous dysferlin correctly localizes on DYSF-/- myotube membranes, enabling membrane resealing in response to injury. Human serum exosomes also carry dysferlin protein and improve membrane repair capabilities of human DYSF-/- myotubes irrespective of mutations. Lack of dysferlin in dysferlinopathic patient serum and urine exosomes enables differentiation between healthy controls and dysferlinopathic patients. Conclusions: Our findings provide evidence that exosomes are efficient carriers of dysferlin and can be employed for the treatment and non-invasive diagnosis of dysferlinopathy.
Subject(s)
Exosomes/metabolism , Muscular Dystrophies, Limb-Girdle/diagnosis , Muscular Dystrophies, Limb-Girdle/pathology , Serum/metabolism , Adolescent , Adult , Animals , Cell Line , Cell Membrane/metabolism , Dysferlin/deficiency , Dysferlin/metabolism , Exosomes/ultrastructure , Female , Humans , Male , Mice , Muscle Fibers, Skeletal/metabolism , Muscle Fibers, Skeletal/ultrastructure , Muscular Dystrophies, Limb-Girdle/blood , Muscular Dystrophies, Limb-Girdle/urine , Urine , Young AdultABSTRACT
BACKGROUND: Mutations in the fukutin-related protein gene FKRP (MIM *606596) cause a form of congenital muscular dystrophy (MDC1C) and also limb girdle muscular dystrophy type 2I (LGMD2I). Exercise-induced myoglobinuria, frequently occurring in metabolic myopathies, has been described in Becker muscular dystrophy and in a few cases of LGMD. OBJECTIVES: To describe that episodes with myoglobinuria, often associated with exercise-induced myalgia, may be common and a presenting symptom in patients with LGMD2I. METHODS: Data on episodes of suspected myoglobinuria and myalgia were collected from the patient records on 14 patients with a diagnosis of LGMDI. RESULTS: Five LGMD2I patients reported recurrent episodes of dark urine and myalgia after exercise, and in three of them, this was the only symptom for several years. CONCLUSIONS: We conclude that episodes compatible with exercise-induced myoglobinuria may be frequent in LGMD2I.
