TNF-alpha is a mitogen in skeletal muscle

Area of Science:

• Muscle regeneration
• Cellular biology
• Immunology

Background:

• Emerging evidence implicates tumor necrosis factor-alpha (TNF-alpha) in muscle repair processes.
• Understanding the precise role of TNF-alpha in satellite cell function is crucial for muscle healing research.

Purpose of the Study:

• To investigate the effects of TNF-alpha on satellite cell proliferation and activation.
• To elucidate the molecular mechanisms by which TNF-alpha influences satellite cell cycle progression.

Main Methods:

• Primary rat myoblast cultures were exposed to recombinant TNF-alpha to assess DNA synthesis.
• Adult mice received systemic TNF-alpha injections to evaluate satellite cell activation in vivo.
• Bromodeoxyuridine (BrdU) incorporation was used to measure DNA synthesis and cell proliferation.
• Serum response factor (SRF) binding activity and reporter gene expression were analyzed.

Main Results:

• TNF-alpha treatment dose-dependently increased DNA content and BrdU incorporation in primary myoblasts.
• Systemic TNF-alpha administration significantly enhanced BrdU incorporation in satellite cells of adult mouse muscle.
• TNF-alpha stimulated SRF binding to the SRE in the c-fos promoter and increased reporter gene expression.

Conclusions:

• TNF-alpha activates quiescent satellite cells, prompting them to enter the cell cycle.
• The cytokine accelerates the G1-to-S phase transition, a key step in cell proliferation.
• These effects of TNF-alpha on satellite cells may be mediated through the activation of early response genes via SRF.