Macrophage Polarization in Osteoarthritis Pathophysiology
Summary
Osteoarthritis is a leading cause of disability worldwide, driven not only by mechanical wear but also by chronic low-grade inflammation within the joint. Central to this inflammatory milieu are synovial macrophages, which adopt distinct functional states known as M1 and M2 phenotypes. M1 macrophages secrete pro-inflammatory cytokines and matrix-degrading enzymes that exacerbate cartilage destruction and synovitis, whereas M2 macrophages produce anti-inflammatory mediators and growth factors that support tissue repair and homeostasis. The dynamic balance between these states is governed by signalling pathways including NF-κB, JAK/STAT, MAPK and Nrf2, and is influenced by cellular crosstalk with chondrocytes, fibroblasts and adipose‐derived factors. Emerging single-cell profiling has revealed considerable heterogeneity among synovial macrophage subsets, suggesting patient-specific disease phenotypes and therapeutic targets. Consequently, strategies aimed at reprogramming macrophage polarization—shifting the joint microenvironment from catabolic to pro-regenerative—have become a central focus for novel disease-modifying interventions in osteoarthritis.
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Macrophage Polarization in Osteoarthritis Pathophysiology publication trend
The graph below shows the total number of articles in macrophage polarization in osteoarthritis pathophysiology across all publications each year (not limited to Nature Index journals).
Technical terms
Macrophage polarization: The process by which macrophages acquire distinct functional phenotypes (M1 or M2) in response to environmental cues.
M1 macrophage: A pro-inflammatory macrophage phenotype characterised by secretion of cytokines and degradative enzymes.
M2 macrophage: An anti-inflammatory macrophage phenotype associated with tissue repair and production of growth factors.
Synovium: The membrane lining a joint capsule that produces synovial fluid and hosts immune cells.
Chondrocyte: The specialised cell type responsible for maintaining cartilage extracellular matrix.
Exosome: A small extracellular vesicle that mediates intercellular communication by transferring proteins, lipids and RNAs.
MicroRNA (miRNA): A short non-coding RNA molecule that regulates gene expression post-transcriptionally.
PGAM5: A mitochondrial phosphatase involved in regulating macrophage metabolism and inflammatory signalling.
Carbonic anhydrase IX (CA9): An enzyme that regulates pH homeostasis and can influence macrophage phenotype in inflamed tissues.
References
- Targeted knockdown of PGAM5 in synovial macrophages efficiently alleviates osteoarthritis. Bone Research (2024).
- Nanomedicines Reprogram Synovial Macrophages by Scavenging Nitric Oxide and Silencing CA9 in Progressive Osteoarthritis. Advanced Science (2023).
- M2 macrophage-derived exosomal miR-26b-5p regulates macrophage polarization and chondrocyte hypertrophy by targeting TLR3 and COL10A1 to alleviate osteoarthritis. Journal of Nanobiotechnology (2024).
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