Muscle Abnormalities in Nonhospitalised Patients With Post-COVID-19 Condition

Area of Science:

• Muscle physiology
• Post-viral syndromes
• Skeletal muscle pathology

Background:

• Post-COVID condition (PCC) affects approximately 10% of individuals after SARS-CoV-2 infection, causing persistent symptoms like fatigue and muscle weakness.
• This study investigated skeletal muscle characteristics in nonhospitalized PCC patients compared to healthy controls.

Purpose of the Study:

• To assess and compare the skeletal muscle morphology, pathology, and molecular profiles of patients with Post-COVID condition (PCC) against healthy individuals.
• To identify potential mechanisms underlying muscle dysfunction in PCC.

Main Methods:

• Muscle biopsies from the vastus lateralis of 28 PCC patients and 28 matched controls were analyzed.
• Analyses included morphological assessment, fiber type composition, capillarization, myonuclei count, and molecular analyses (lipidomics, RNA sequencing).

Main Results:

• PCC patients showed increased angulated, small, rounded fibers, and fetal myosin expression, indicating degeneration and regeneration.
• Significantly lower fiber cross-sectional area and myonuclei number were observed in PCC patients.
• Reduced capillarization, lower phospholipid levels, and downregulated oxidative phosphorylation pathways were found in PCC patients.

Conclusions:

• Nonhospitalized PCC patients exhibit muscle changes suggestive of degeneration and regeneration, potentially linked to reduced physical activity.
• Myopathic and neurogenic post-viral effects may contribute to the observed muscle alterations, including inflammation, fibrosis, and altered fiber characteristics.