Elevated TGF β2 serum levels in Emery-Dreifuss Muscular Dystrophy: Implications for myocyte and tenocyte differentiation and fibrogenic processes

Pia Bernasconi,Elena Pegoraro,Gabriele Siciliano,Elisa Schena,Nicola Carboni,Lucia Ruggiero,Antoine Muchir,Luisa Politano,Camilla Evangelisti,Patrizia Sabatelli,Gisèle Bonne,Cristina Cappelletti,Elena Biagini,Tiziana Mongini,Carmelo Rodolico,Paola Cavalcante,Liliana Vercelli,Marta Columbaro,Giuseppe Boriani,Giulia Ricci,Sabino Prencipe,Lorenzo Maggi,Lucia Morandi,Chiara Lanzuolo,Lucio Santoro,Giovanna Lattanzi

doi:10.1080/19491034.2018.1467722

Abstract

ABSTRACTAmong rare diseases caused by mutations in LMNA gene, Emery-Dreifuss Muscular Dystrophy type 2 and Limb-Girdle muscular Dystrophy 1B are characterized by muscle weakness and wasting, joint contractures, cardiomyopathy with conduction system disorders. Circulating biomarkers for these pathologies have not been identified. Here, we analyzed the secretome of a cohort of patients affected by these muscular laminopathies in the attempt to identify a common signature. Multiplex cytokine assay showed that transforming growth factor beta 2 (TGF β2) and interleukin 17 serum levels are consistently elevated in the vast majority of examined patients, while interleukin 6 and basic fibroblast growth factor are altered in subgroups of patients. Levels of TGF β2 are also increased in fibroblast and myoblast cultures established from patient biopsies as well as in serum from mice bearing the H222P Lmna mutation causing Emery-Dreifuss Muscular Dystrophy in humans. Both patient serum and fibroblast conditioned media activated a TGF β2-dependent fibrogenic program in normal human myoblasts and tenocytes and inhibited myoblast differentiation. Consistent with these results, a TGF β2 neutralizing antibody avoided fibrogenic marker activation and myogenesis impairment. Cell intrinsic TGF β2-dependent mechanisms were also determined in laminopathic cells, where TGF β2 activated AKT/mTOR phosphorylation. These data show that TGF β2 contributes to the pathogenesis of Emery-Dreifuss Muscular Dystrophy type 2 and Limb-Girdle muscular Dystrophy 1B and can be considered a potential biomarker of those diseases. Further, the evidence of TGF β2 pathogenetic effects in tenocytes provides the first mechanistic insight into occurrence of joint contractures in muscular laminopathies.

Highlights

Emery-Dreifuss Muscular Dystrophy (EDMD) is a rare genetic condition causing elbow and Achilles tendon contractures, rigid spine, muscle weakness and wasting and cardiomyopathy with conduction system disorder [1]
Other cytokines affected in Emery-Dreifuss Muscular Dystrophy type 2 (EDMD2) sera were Interleukin (IL) 17 (IL17) that was increased to a variable extent in most patients and basic FGF (FGF-b), this growth factor was increased in subgroups of patients (LMNA1 and 3, Fig. 1B) and decreased in other patients (LMNA2 group, Fig. 1B)
2) Activation of AKT/mTOR pathway is demonstrated as an effect of increased TGFbeta 2 signaling in EDMD2 myoblasts

Summary

Introduction

Emery-Dreifuss Muscular Dystrophy (EDMD) is a rare genetic condition causing elbow and Achilles tendon contractures, rigid spine, muscle weakness and wasting and cardiomyopathy with conduction system disorder [1]. Signs of lipodystrophy are observed in a significant percentage of EDMD patients [2,3]. The disease is linked to mutations in nuclear envelope/lamina genes including LMNA, EMD, SYNE 1/2 and can be caused by FHL1 mutations or worsened by modifiers such as SUN1 and SUN2, encoding nuclear envelope proteins [4]. We have previously described pathogenetic mechanisms of EDMD by showing that LMNA mutations affect lamin A/C levels and phosphorylation [5] and cause clustering of myonuclei, an effect involving SUN1 and SUN2 [6].

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Results

Conclusion