Abnormal NFAT5 Physiology in Duchenne Muscular Dystrophy Fibroblasts as a Putative Explanation for the Permanent Fibrosis Formation in Duchenne Muscular Dystrophy.

Sandrine Herbelet,Jan L De Bleecker,Boel De Paepe

doi:10.3390/ijms21217888

Sandrine Herbelet, Jan L De Bleecker + Show 1 more

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https://doi.org/10.3390/ijms21217888

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Abstract

Duchenne muscular dystrophy (DMD) is characterized by chronic inflammation and fibrotic tissue production by fibroblasts. The promyogenic factor nuclear factor of activated T-cells 5 (NFAT5) is virtually present in all cells, responding to hyperosmolar or pro-inflammatory stress. In embryogenic fibroblasts, absence of NFAT5 results in cell cycle arrest. Here, unaffected skeletal muscle fibroblasts from one healthy donor showed NFAT5 nuclear translocation upon hyperosmolar stress and normal cell viability. Absence of NFAT5 translocation under pro-inflammatory conditions resulted in decreased cell growth (Incucyte ZOOM). In DMD skeletal muscle fibroblasts from one DMD patient, NFAT5 was merely located in the nucleus. Exposure to hyperosmolar conditions or pro-inflammatory cytokines IFN-γ, IL-1β and TNF-α had no influence on NFAT5 physiology (immunofluorescence, western blotting, RT-qPCR). Hyperosmolarity resulted in decreased cell viability and pro-inflammatory stress in unaltered cell growth. These findings suggest that NFAT5 is vital to DMD fibroblast survival. Exposure to pro-inflammatory or hyperosmolar stress in DMD fibroblasts results in an unexpected NFAT5 response, where fibroblasts are not triggered by inflammatory cytokines and do not withstand hyperosmolarity. Chronic inflammation could be viewed as a non-restrictive factor in the formation of fibrosis in DMD. Abnormal NFAT5 physiology could provide a molecular explanation for permanent fibrotic matrix production by DMD fibroblasts.

Highlights

Duchenne muscular dystrophy (DMD) is an inherited, X-linked, severe muscle degenerating disorder caused by mutations in the dystrophin gene as initially described in 1987 by Hoffman et al [1] and Koenig et al [2]
Nuclear translocation was clearly visible by immunofluorescence (IF) (Figure 1A, left side, white arrow) and by fractionated western blotting (WB) where nuclear factor of activated T-cells 5 (NFAT5) decreased in the cytoplasmic fraction and increased in the nuclear compartment (Figure 1A, right side)
In rheumatoid arthritis (RA), a disease characterized by high levels of pro-inflammatory cytokines, NFAT5 is translocated to the nucleus and highly expressed in fibroblast-like synoviocytes (FLS) after exposure to pro-inflammatory cytokines, including tumor necrosis factor (TNF)-α and IL-1β

Summary

Introduction

Duchenne muscular dystrophy (DMD) is an inherited, X-linked, severe muscle degenerating disorder caused by mutations in the dystrophin gene as initially described in 1987 by Hoffman et al [1] and Koenig et al [2]. This leads to dysfunctional dystrophin-associated protein complex (DAPC), contraction-induced damage and leaky channels in myocytes [3,4]. DMD is characterized by cycles of myocyte degeneration and regeneration, where muscular tissue is replaced by fibrotic tissue The latter is formed by fibroblasts, which initially play a scaffolding role, along which skeletal muscle stem cells, called myoblasts, regenerate the injured tissue. This process is a tightly controlled process, where fibroblasts disappear when their scaffolding role is no longer needed

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