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SummaryProgressive weakness and muscle loss are associated with multiple chronic conditions including muscular dystrophy and cancer. Cancer-associated cachexia, characterized by dramatic weight loss and fatigue, leads to reduced quality of life and poor survival. Inflammatory cytokines have been implicated in muscle atrophy, however, available anti-cytokine therapies failed to prevent muscle wasting in cancer patients. We previously reported that muscle-specific deletion of the Oncostatin M (OSM) receptor (OSMR) preserved muscle mass and function in tumor-bearing mice. Here, we show that OSM is a potent inducer of muscle atrophy. OSM triggers cellular atrophy in primary myotubes utilizing the JAK/STAT3 pathway. Identification of OSM targets by RNA sequencing revealed the induction of various muscle atrophy-related genes, includingAtrogin1. OSM overexpression in mice caused muscle wasting while the neutralization of circulating OSM protected from tumor-driven loss of muscle mass and function. Our results indicate that activated OSM/OSMR signaling drives muscle atrophy, and the therapeutic targeting of this pathway may be useful in preventing muscle wasting.

SummarySkeletal muscle atrophy is a hallmark of the cachexia syndrome that is associated with poor survival and reduced quality of life in cancer patients1. Muscle atrophy involves excessive protein catabolism and loss of muscle mass and strength2. An effective therapy against muscle wasting is lacking as mechanisms driving the atrophy process remain incompletely understood. Our gene expression analysis in muscle tissues revealed upregulation of Ectodysplasin A2 Receptor (EDA2R) in tumor-bearing mice and cachectic cancer patients. Here we show that activation of EDA2R signaling promotes skeletal muscle atrophy. Stimulation of primary myotubes with EDA2R ligand, EDA-A2, triggered pronounced cellular atrophy via inducing the expression of muscle atrophy-related genesAtrogin1andMuRF1. EDA-A2-driven myotube atrophy involved activation of the noncanonical NFκB pathway and depended on NIK kinase activity. While EDA-A2 overexpression induced muscle wasting in mice, the deletion of EDA2R or muscle NIK protected tumor-bearing mice from the loss of muscle mass and function. Tumor-induced Oncostatin M upregulated muscle EDA2R expression and muscle-specific Oncostatin M Receptor (OSMR) knockout mice were resistant to tumor-driven muscle wasting. Our results demonstrate that EDA2R/NIK signaling mediates cancer-associated muscle atrophy in an OSM/OSMR-dependent manner. Thus, therapeutic targeting of these pathways may be beneficial in preventing muscle loss.

Skeletal muscle atrophy is a hallmark of the cachexia syndrome that is associated with poor survival and reduced quality of life in patients with cancer. Muscle atrophy involves excessive protein catabolism and loss of muscle mass and strength. An effective therapy against muscle wasting is currently lacking because mechanisms driving the atrophy process remain incompletely understood. Our gene expression analysis in muscle tissues indicated upregulation of ectodysplasin A2 receptor (EDA2R) in tumour-bearing mice and patients with cachectic cancer. Here we show that activation of EDA2R signalling promotes skeletal muscle atrophy. Stimulation of primary myotubes with the EDA2R ligand EDA-A2 triggered pronounced cellular atrophy by induction of the expression of muscle atrophy-related genes Atrogin1 and MuRF1. EDA-A2-driven myotube atrophy involved activation of the non-canonical NFĸB pathway and was dependent on NFκB-inducing kinase (NIK) activity. Whereas EDA-A2 overexpression promoted muscle wasting in mice, deletion of either EDA2R or muscle NIK protected tumour-bearing mice from loss of muscle mass and function. Tumour-induced oncostatin M (OSM) upregulated muscle EDA2R expression, and muscle-specific oncostatin M receptor (OSMR)-knockout mice were resistant to tumour-induced muscle wasting. Our results demonstrate that EDA2R-NIK signalling mediates cancer-associated muscle atrophy in an OSM-OSMR-dependent manner. Thus, therapeutic targeting of these pathways may be beneficial in prevention of muscle loss.

Apart from well-defined factors in neuronal cells1, only a few reports consider that the variability of sporadic amyotrophic lateral sclerosis (ALS) progression can depend on less-defined contributions from glia2,3 and blood vessels4. In this study we use an expression-weighted cell-type enrichment method to infer cell activity in spinal cord samples from patients with sporadic ALS and mouse models of this disease. Here we report that patients with sporadic ALS present cell activity patterns consistent with two mouse models in which enrichments of vascular cell genes preceded microglial response. Notably, during the presymptomatic stage, perivascular fibroblast cells showed the strongest gene enrichments, and their marker proteins SPP1 and COL6A1 accumulated in enlarged perivascular spaces in patients with sporadic ALS. Moreover, in plasma of 574 patients with ALS from four independent cohorts, increased levels of SPP1 at disease diagnosis repeatedly predicted shorter survival with stronger effect than the established risk factors of bulbar onset or neurofilament levels in cerebrospinal fluid. We propose that the activity of the recently discovered perivascular fibroblast can predict survival of patients with ALS and provide a new conceptual framework to re-evaluate definitions of ALS etiology.

In the version of this article initially published, the label along the right margin of the top row in Fig. 2d (SO1DG93A) was incorrect. The correct label is ‘SOD1G93A’. The error has been corrected in the HTML and PDF versions of the article.