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Increased intra-mitochondrial lipofuscin aggregates with spherical dense body formation in mitochondrial myopathy

Jian-Qiang Lu1, Cynthia M F Monaco2, Thomas J Hawke2

  • 1Department of Pathology and Molecular Medicine/Neuropathology, McMaster University, Hamilton, Ontario, Canada.

Journal of the Neurological Sciences
|April 10, 2020
PubMed

Insights

Lipofuscin accumulation within mitochondria is elevated in mitochondrial myopathy (MM). This intra-mitochondrial lipofuscin formation, particularly spherical dense bodies (SDBs), contributes to mitochondrial disease pathology.

Area of Science:

  • Mitochondrial Biology
  • Cellular Pathology
  • Muscle Diseases

Background:

  • Lipofuscin accumulation, resulting from impaired autophagy-lysosome degradation of damaged mitochondria, may worsen mitochondrial abnormalities.
  • Intra-mitochondrial lipofuscin aggregation is implicated in the pathophysiology of mitochondrial myopathy (MM) and other mitochondrial diseases.

Purpose of the Study:

  • To investigate the presence and significance of intra-mitochondrial lipofuscin aggregates and spherical dense bodies (SDBs) in patients with MM.
  • To compare these findings with other myopathies and age-matched controls.

Main Methods:

  • Analysis of vastus lateralis muscle biopsies from MM patients, inclusion body myositis (IBM) patients, younger adults, and older subjects.
  • Assessment of lipofuscin aggregation using autofluorescence microscopy, histochemical stains, and electron microscopy (EM).
  • Semi-quantitative assessment of intra-mitochondrial lipofuscin aggregates, SDBs, and paracrystalline inclusions (PCIs) via EM.

Main Results:

  • Intra-mitochondrial lipofuscin aggregates did not significantly differ between MM patients, older subjects, and IBM patients, but were different from younger adults.
  • Intra-mitochondrial SDBs were significantly more abundant in MM patients compared to older subjects, IBM patients, and younger adults.
  • A significant positive correlation was observed between intra-mitochondrial lipofuscin aggregates and SDBs.

Conclusions:

  • Intra-mitochondrial formation of lipofuscin SDBs is increased in mitochondrial myopathy (MM).
  • These findings suggest that intra-mitochondrial lipofuscin SDBs play a role in the pathophysiology of mitochondrial diseases.
Keywords:
Chronic progressive external ophthalmoplegiaElectron microscopyLipofuscinMitochondrial myopathyParacrystalline inclusionsSpherical dense bodies

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