Established PABPN1 intranuclear inclusions in OPMD muscle can be efficiently reversed by AAV-mediated knockdown and replacement of mutant expanded PABPN1

Systemic Delivery of a Monoclonal Antibody to Immunologically Block Myostatin in the A17 Mouse Model of OPMD

Oculopharyngeal muscular dystrophy (OPMD) is a late-onset rare muscle disease affecting approximately 1 in 80,000 individuals worldwide. However, it can affect as much as 1:600 individuals in some populations due to a strong founder effect. The muscle pathology is characterized by progressive eyelid drooping (ptosis), swallowing difficulties (dysphagia), and limb weakness at later stages of disease progression. The genetic defect is associated with significant fibrotic deposition and atrophy in affected muscles. No treatments are available to cure the disease. Only surgical techniques to correct ptosis and swallowing are currently possible, though they carry a risk of recurrence. Myostatin is a negative regulator of muscle growth, and several strategies to downregulate its expression have been developed with the aim of improving muscle mass and strength in muscular pathologies. We recently showed that weekly systemic treatment of the A17 murine model of OPMD with a monoclonal antibody for myostatin improves body and muscle mass, increases muscle strength, and reduces muscle fibrosis. Here, we describe the methodology for repeated intraperitoneal delivery of myostatin antibody in the murine model. Furthermore, we detail the most relevant analyses to assess histopathological and functional improvements of this treatment in this mouse model.

[Nuclear aggregates in oculopharyngeal muscular dystrophy]

Oculopharyngeal muscular dystrophy (OPMD) is one of the diseases related to pathological expansions of trinucleotides. Its pathogenesis remains unclear although the presence of aggregates within the nuclei of the muscle fiber seems to play an important role. The basic research studies presented here help understand their composition and their deleterious role. These elements may result in new therapeutic avenues.

Pharyngeal pathology in a mouse model of oculopharyngeal muscular dystrophy is associated with impaired basal autophagy in myoblasts

Oculopharyngeal muscular dystrophy (OPMD) is a late-onset dominant disease that primarily affects craniofacial muscles. Despite the fact that the genetic cause of OPMD is known to be expansion mutations in the gene encoding the nuclear polyadenosine RNA binding protein PABPN1, the molecular mechanisms of pathology are unknown and no pharmacologic treatments are available. Due to the limited availability of patient tissues, several animal models have been employed to study the pathology of OPMD. However, none of these models have demonstrated functional deficits in the muscles of the pharynx, which are predominantly affected by OPMD. Here, we used a knock-in mouse model of OPMD, Pabpn1 +/A17 , that closely genocopies patients. In Pabpn1 +/A17 mice, we detected impaired pharyngeal muscle function, and impaired pharyngeal satellite cell proliferation and fusion. Molecular studies revealed that basal autophagy, which is required for normal satellite cell function, is higher in pharynx-derived myoblasts than in myoblasts derived from limb muscles. Interestingly, basal autophagy is impaired in cells derived from Pabpn1 +/A17 mice. Pabpn1 knockdown in pharyngeal myoblasts failed to recapitulate the autophagy defect detected in Pabpn1 +/A17 myoblasts suggesting that loss of PABPN1 function does not contribute to the basal autophagy defect. Taken together, these studies provide the first evidence for pharyngeal muscle and satellite cell pathology in a mouse model of OPMD and suggest that aberrant gain of PABPN1 function contributes to the craniofacial pathology in OPMD.

Recent Progress in Oculopharyngeal Muscular Dystrophy

Oculopharyngeal muscular dystrophy (OPMD) is a late-onset intractable myopathy, characterized by slowly progressive ptosis, dysphagia, and proximal limb weakness. It is caused by the abnormal expansion of the alanine-encoding (GCN)n trinucleotide repeat in the exon 1 of the polyadenosine (poly[A]) binding protein nuclear 1 gene (11-18 repeats in OPMD instead of the normal 10 repeats). As the disease progresses, the patients gradually develop a feeling of suffocation, regurgitation of food, and aspiration pneumonia, although the initial symptoms and the progression patterns vary among the patients. Autologous myoblast transplantation may provide therapeutic benefits by reducing swallowing problems in these patients. Therefore, it is important to assemble information on such patients for the introduction of effective treatments in nonendemic areas. Herein, we present a concise review of recent progress in clinical and pathological studies of OPMD and introduce an idea for setting up a nation-wide OPMD disease registry in Japan. Since it is important to understand patients' unmet medical needs, realize therapeutically targetable symptoms, and identify indices of therapeutic efficacy, our attempt to establish a unique patient registry of OPMD will be a helpful tool to address these urgent issues.

Translational research on Myology and Mobility Medicine: 2021 semi-virtual PDM3 from Thermae of Euganean Hills, May 26 - 29, 2021

On 19-21 November 2020, the meeting of the 30 years of the Padova Muscle Days was virtually held while the SARS-CoV-2 epidemic was hitting the world after a seemingly quiet summer. During the 2020-2021 winter, the epidemic is still active, despite the start of vaccinations. The organizers hope to hold the 2021 Padua Days on Myology and Mobility Medicine in a semi-virtual form (2021 S-V PDM3) from May 26 to May 29 at the Thermae of Euganean Hills, Padova, Italy. Here the program and the Collection of Abstracts are presented. Despite numerous world problems, the number of submitted/selected presentations (lectures and oral presentations) has increased, prompting the organizers to extend the program to four dense days.

Age-Associated Salivary MicroRNA Biomarkers for Oculopharyngeal Muscular Dystrophy

Small non-coding microRNAs (miRNAs) are involved in the regulation of mRNA stability. Their features, including high stability and secretion to biofluids, make them attractive as potential biomarkers for diverse pathologies. This is the first study reporting miRNA as potential biomarkers for oculopharyngeal muscular dystrophy (OPMD), an adult-onset myopathy. We hypothesized that miRNA that is differentially expressed in affected muscles from OPMD patients is secreted to biofluids and those miRNAs could be used as biomarkers for OPMD. We first identified candidate miRNAs from OPMD-affected muscles and from muscles from an OPMD mouse model using RNA sequencing. We then compared the OPMD-deregulated miRNAs to the literature and, subsequently, we selected a few candidates for expression studies in serum and saliva biofluids using qRT-PCR. We identified 126 miRNAs OPMD-deregulated in human muscles, but 36 deregulated miRNAs in mice only (pFDR < 0.05). Only 15 OPMD-deregulated miRNAs overlapped between the in humans and mouse studies. The majority of the OPMD-deregulated miRNAs showed opposite deregulation direction compared with known muscular dystrophies miRNAs (myoMirs), which are associated. In contrast, similar dysregulation direction was found for 13 miRNAs that are common between OPMD and aging muscles. A significant age-association (p < 0.05) was found for 17 OPMD-deregulated miRNAs (13.4%), whereas in controls, only six miRNAs (1.4%) showed a significant age-association, suggesting that miRNA expression in OPMD is highly age-associated. miRNA expression in biofluids revealed that OPMD-associated deregulation in saliva was similar to that in muscles, but not in serum. The same as in muscle, miRNA expression levels in saliva were also found to be associated with age (p < 0.05). Moreover, the majority of OPMD-miRNAs were found to be associated with dysphagia as an initial symptom. We suggest that levels of specific miRNAs in saliva can mark muscle degeneration in general and dysphagia in OPMD.