SPP1 macrophages across diseases: A call for reclassification?

Area of Science:

• Immunology
• Cell Biology
• Pathology

Background:

• Secreted phosphoprotein 1 (SPP1)+ macrophages, marked by high osteopontin gene expression, are implicated in aging, chronic inflammation, and cancer.
• While often viewed as tumor-associated macrophages, their presence in non-cancerous conditions like aging and muscle diseases indicates broader pathological relevance.

Purpose of the Study:

• To explore the diverse roles of SPP1+ macrophages across various diseases.
• To advocate for the reclassification of SPP1+ macrophages as a distinct subtype associated with chronic inflammation.

Main Methods:

• Literature review and synthesis of existing research on SPP1+ macrophages.
• Analysis of conserved traits and clinical outcomes associated with SPP1+ macrophages in different pathological contexts.

Main Results:

• SPP1+ macrophages exhibit conserved functions such as promoting fibrosis, remodeling the extracellular matrix, and modulating immune responses.
• These functions are frequently associated with adverse clinical outcomes across multiple diseases.

Conclusions:

• SPP1+ macrophages play significant roles beyond oncology, particularly in chronic inflammatory conditions.
• Reclassifying SPP1+ macrophages as a distinct subtype could advance our understanding of macrophage biology and guide the development of targeted therapies.