Deciphering the Osteoimmune Landscape in Subtalar Arthrodesis: A Single-Cell RNA Sequencing Approach

Area of Science:

• Orthopedics
• Immunology
• Regenerative Medicine

Background:

• Subtalar arthrodesis (SA) is a key procedure for posttraumatic subtalar arthritis (PSA).
• The role of the immune system in bone healing after SA is not fully understood.
• Defining the systemic osteoimmunological response is crucial for improving outcomes.

Purpose of the Study:

• To investigate immune cell dynamics following SA.
• To correlate immune cell profiles with bone healing rates (early vs. delayed union).
• To identify specific immune pathways influencing subtalar bone fusion.

Main Methods:

• Single-cell RNA sequencing (scRNA-seq) of peripheral blood mononuclear cells (PBMCs) from SA patients.
• Collection of PBMCs pre-surgery and 3 months post-surgery.
• Computed tomography (CT) scans to assess bone fusion and categorize patients into early (EU) and delayed union (DU) groups.

Main Results:

• Monocytes in the EU group showed enhanced antigen processing, while DU monocytes had increased phagocytosis.
• NK cells in the DU group displayed stronger cytotoxicity via Fc-gamma receptor and ADCC pathways.
• NK cells in the EU group exhibited higher chemokine and cytokine activity, with immune differences persisting postoperatively.

Conclusions:

• Systemic immune environment variations influence bone healing after subtalar arthrodesis.
• Monocytes and NK cells play significant roles in bone union.
• Immunomodulatory strategies could potentially enhance bone repair in SA patients.