Manual Therapy Exerts Local Anti-Inflammatory Effects Through Neutrophil Clearance.

Area of Science:

• Biomedical Science
• Immunology
• Regenerative Medicine

Background:

• Manual therapy (MT) is a traditional Chinese treatment for local inflammation, but its anti-inflammatory mechanisms lack scientific validation.
• Understanding the molecular pathways of MT is crucial for its therapeutic application in inflammatory conditions.

Purpose of the Study:

• To investigate the anti-inflammatory effects and underlying mechanisms of manual therapy (MT) in cardiotoxin (CTX)-induced skeletal muscle inflammation in mice.
• To elucidate how MT modulates cellular and molecular responses in injured skeletal muscle.

Main Methods:

• Skeletal muscle inflammation was induced using cardiotoxin (CTX) in C57BL6/J mice, followed by manual therapy (MT) intervention.
• Single-cell RNA sequencing (scRNA-seq) was integrated with molecular techniques (immunofluorescence, western blot) and histological analyses (H&E, IHC) to assess cellular and molecular changes.
• Key cellular populations, cytokine levels, and specific gene/protein expressions (S100A9, Ly6g+/Mpo+ neutrophils) were analyzed.

Main Results:

• MT significantly reduced pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) in CTX-induced skeletal muscle inflammation.
• scRNA-seq identified neutrophils as a major cell type with increased numbers and activity in injured muscle, expressing high levels of S100A9.
• MT treatment inhibited S100A9 protein expression and reduced the number and activity of neutrophils (Ly6g+/Mpo+), leading to reduced inflammation.

Conclusions:

• Manual therapy effectively mitigates localized skeletal muscle inflammation in a mouse model.
• The anti-inflammatory effect of MT is mediated by the downregulation of S100A9 expression and the clearance of neutrophils.
• These findings provide a scientific basis for MT as a therapeutic strategy for skeletal muscle inflammation.