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Abstract
Background and Objectives The idiopathic inflammatory myopathy dermatomyositis is an acquired disease that involves muscle, lung, and skin impairments. Patients with dermatomyositis show a wide range of severity of proximal skeletal muscle weakness, associated with inflammatory infiltrates, vasculitis, capillary dropout, and perifascicular myofiber atrophy. Muscles of patients with dermatomyositis show signs of muscle regeneration. Because muscle stem cells (MuSCs) are responsible for myofiber repair, we wondered whether the proliferative properties of MuSCs are altered in dermatomyositis muscle. We investigated the role of type I interferon (IFN-I) in this process because dermatomyositis is associated with sustained inflammation with high IFN-I levels.
Methods MuSCs isolated from normal muscles and those from adult and juvenile patients with dermatomyositis were grown in culture and analyzed in vitro for their proliferating properties, myogenic capacities, and senescence. Gain- and loss-of-function experiments were performed to assess the role of IFN-I signaling in the proliferative capacities of MuSCs.
Results MuSCs derived from 8 adult patients with dermatomyositis (DM-MuSCs) (5 severe form and 3 mild form, established from histologic evaluation), from 3 patients with juvenile dermatomyositis, and from normal muscle were used to analyze their myogenesis in vitro. DM-MuSCs exhibited strongly reduced proliferating capacities as compared with healthy MuSCs (−31% to −43% for mild and severe dermatomyositis, respectively), leading to poor myotube formation (−36% to −71%). DM-MuSCs were enriched in senescent, β-galactosidase–positive cells, partly explaining the proliferation defect. Gain- and loss-of-function experiments were performed to assess the role of IFN-I on the proliferative capacity of MuSCs. High concentrations of IFN-I decreased the proliferation of healthy MuSCs. Similarly, conditioned medium from DM-MuSCs decreased the proliferation of healthy MuSCs (−15% to −22%), suggesting the delivery of an autocrine effector. Pharmacologic blockade of IFN signaling (using ruxolitinib or anti–IFN receptor antibodies) in DM-MuSCs rescued their proliferation up to the control values.
Discussion These results show that autocrine IFN-I signaling prevents MuSC expansion, leading to muscle repair deficit. This process may explain the persistent muscle weakness observed in patients with severe dermatomyositis.
Glossary
- DM-MuSC=
- muscle stem cell isolated from patient with dermatomyositis;
- EdU=
- 5-ethynyl-2′-deoxyuridine;
- FBS=
- fetal bovine serum;
- HC=
- healthy control;
- IFN-I=
- type I interferon;
- ISG=
- interferon-sensitive gene;
- jDM=
- juvenile dermatomyositis;
- mDM=
- mild dermatomyositis;
- MuSC=
- muscle stem cell;
- MxA=
- myxovirus resistance protein A;
- sDM=
- severe dermatomyositis
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
↵* These authors contributed equally to this work as co–senior authors.
Submitted and externally peer-reviewed. The handling editor was Anthony Amato, MD, FAAN.
Editorial, page 869
- Received October 1, 2021.
- Accepted in final form February 8, 2022.
- © 2022 American Academy of Neurology
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