Mitochondrial disorders are associated with morphological neuromuscular junction defects

• Published in: Neuromuscular disorders : NMD Vol. 45; p. 105235
• Main Authors: Lessard, Lola E. R., Girard, Emmanuelle, Streichenberger, Nathalie, Petiot, Philippe, Acquaviva, Cécile, Pagan, Cécile, Mulligan, Peter, Bouhour, Françoise, Schaeffer, Laurent, Jacquier, Arnaud
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 01.12.2024; Elsevier
• Subjects: Adult; Aged; Confocal microscopy; Denervation; Fatigability; Female; Humans; Life Sciences; Male; Middle Aged; Mitochondrial Diseases - pathology; Muscle, Skeletal - pathology; Neuromuscular Junction - pathology; Neuromuscular Junction Diseases - pathology; Ptosis; Reinnervation; Remodeling; Young Adult; Ptosis; Confocal microscopy; Reinnervation; Remodeling; Fatigability; Denervation
• ISSN: 0960-8966; 1873-2364; 1873-2364
• DOI: 10.1016/j.nmd.2024.105235

•Differentiating mitochondrial disorders from myasthenic syndromes can be challenging.•The neuromuscular junction is a plastic synapse that remodels under stress condition.•Endplates undergo morphological changes in patients with mitochondrial disorders.•This remodeling is not secondary to myofiber atrophy or neuropathy.•Pathological mechanisms underpinning this primary remodeling are to be characterized. We aimed to evaluate whether inherited mitochondrial dysfunction is associated with neuromuscular junction remodeling in patients with mitochondrial disorders. Muscle biopsies from 15 patients with mitochondrial disorders and 10 control patients were analyzed through immunostaining for various neuromuscular junction components. The patient group, with a mean age of 49.9 years, exhibited various mitochondrial disorders including chronic progressive external ophthalmoplegia, Kearns-Sayre syndrome, and mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes. Patients with mitochondrial disorders had a high percentage of remodeled (p= 0.0001), neoformed (p= 0.0049) and dilated (p= 0.016) endplates. There was a trend toward an increased proportion of neuromuscular junctions with terminal Schwann cell extension in these patients (p= 0.052). No significant difference was found in myofiber diameter between the groups. The observed neuromuscular junction defects varied widely across different mitochondrial disorder phenotypes and were present even without accompanying muscle weakness or neuropathy. This suggest that mitochondrial disorders are associated with a primary NMJ remodeling independent of muscle structural damage. Pathomechanisms underpinning this remodeling of the neuromuscular junction, as well as clinical factors predictive of this remodeling, remain to be fully characterized.