Apoptosis in multinucleated skeletal muscle myotubes

Area of Science:

• Cell Biology
• Muscle Physiology
• Molecular Biology

Background:

• Endonuclease-mediated DNA degradation is observed in skeletal muscle disorders, but its interpretation is complex.
• Apoptosis in postmitotic, multinucleated skeletal muscle is poorly understood.
• Distinguishing muscle cell apoptosis from non-muscle cell contributions in vivo is challenging.

Purpose of the Study:

• To investigate the characteristics and mechanisms of apoptosis in skeletal muscle cells.
• To determine if apoptosis in skeletal muscle shares features with mononuclear mitotic cells.
• To compare the apoptotic degeneration pattern in skeletal muscle with that observed in muscular dystrophies.

Main Methods:

• C2C12 skeletal muscle myotubes were treated with staurosporine.
• Classic apoptosis features were assessed, including cell/nuclear morphology and phosphatidylserine externalization.
• Procaspase 3 activation, DNA degradation (TUNEL assay), and DNA laddering were analyzed.

Main Results:

• Staurosporine induced cell and nuclear shrinkage, preserving cellular membranes initially.
• Phosphatidylserine externalization occurred within 2 hours; procaspase 3 activation within 4 hours.
• DNA degradation and laddering were detected within 4 and 8 hours, respectively.

Conclusions:

• Apoptosis in postmitotic, multinucleated skeletal muscle exhibits characteristics similar to mononuclear mitotic cells.
• The observed apoptotic degeneration pattern in skeletal muscle does not align with patterns seen in muscular dystrophies.
• This research clarifies the process of programmed cell death in skeletal muscle.