[Muscle stem cells and metabolism in Duchenne muscular dystrophy, focus on AMPK].

Through their myogenic activity, adult muscle stem cells (MuSCs) are crucial for the regeneration of striated skeletal muscle. Once activated, they proliferate, differentiate and then fuse to repair or form new muscle fibers (myofibers). Their progression through myogenesis requires a complex regulation involving multiple players such as metabolism, in particular via AMPK.

[Metabolic dysfunctions in type I myotonic dystrophy: A potential therapeutic target].

Myotonic dystrophy type I (DM1) is a genetic disease characterized by a multisystemic RNA metabolism dysregulation and splicing toxicity. Numerous signaling pathways are deregulated, and especially AMPK, a key sensor and regulator of cellular metabolism. To restore AMPK signaling activity in DM1 muscle tissue and cells could improve mitochondrial biogenesis and dynamics, mitophagy and oxidative stress, energy production and, in fine, skeletal muscle tissue homeostasis.

Nicotinamide and pyridoxine stimulate muscle stem cell expansion and enhance regenerative capacity during aging.

Skeletal muscle relies on resident muscle stem cells (MuSCs) for growth and repair. Aging and muscle diseases impair MuSC function, leading to stem cell exhaustion and regenerative decline that contribute to the progressive loss of skeletal muscle mass and strength. In the absence of clinically available nutritional solutions specifically targeting MuSCs, we used a human myogenic progenitor high-content imaging screen of natural molecules from food to identify nicotinamide (NAM) and pyridoxine (PN) as bioactive nutrients that stimulate MuSCs and have a history of safe human use.

Contribution of major histocompatibility complex class II immunostaining in distinguishing idiopathic inflammatory myopathy subgroups: A histopathological cohort study.

Idiopathic inflammatory myopathies (IIM) are rare, acquired muscle diseases; their diagnosis of is based on clinical, serological, and histological criteria. MHC-I-positive immunostaining, although non-specific, is used as a marker for IIM diagnosis; however, the significance of major histocompatibility complex (MHC)-II immunostaining in IIM remains debated. We investigated patterns of MHC-II immunostaining in myofibers and capillaries in muscle biopsies from 103 patients with dermatomyositis ([DM], n = 31), inclusion body myositis ([IBM], n = 24), anti-synthetase syndrome ([ASyS], n = 10), immune-mediated necrotizing myopathy ([IMNM], n = 18), or overlap myositis ([OM], n = 20).