S100A8/A9 drives monocytes towards M2-like macrophage differentiation and associates with M2-like macrophages in osteoarthritic synovium

Nienke J T van Kooten; Arjen B Blom; Iris J Teunissen van Manen; Wessel F Theeuwes; Johannes Roth; Mark A J Gorris; Birgitte Walgreen; Annet W Sloetjes; Monique M Helsen; Elly L Vitters; Peter L E M van Lent; Sander Koëter; Peter M van der Kraan; Thomas Vogl; Martijn H J van den Bosch

doi:10.1093/rheumatology/keae020

S100A8/A9 drives monocytes towards M2-like macrophage differentiation and associates with M2-like macrophages in osteoarthritic synovium

Rheumatology (Oxford). 2024 Jan 12:keae020. doi: 10.1093/rheumatology/keae020. Online ahead of print.

Authors

Nienke J T van Kooten^{1

2}, Arjen B Blom¹, Iris J Teunissen van Manen¹, Wessel F Theeuwes¹, Johannes Roth³, Mark A J Gorris^{4

5}, Birgitte Walgreen¹, Annet W Sloetjes¹, Monique M Helsen¹, Elly L Vitters, Peter L E M van Lent¹, Sander Koëter², Peter M van der Kraan¹, Thomas Vogl³, Martijn H J van den Bosch¹

Affiliations

¹ Experimental Rheumatology, Radboud University Medical Center, Nijmegen, the Netherlands.
² Orthopedics, Canisius Wilhelmina Ziekenhuis, Nijmegen, the Netherlands.
³ Institute of Immunology, University of Münster, Münster, Germany.
⁴ Medical BioSciences, Radboud University Medical Center, Nijmegen, the Netherlands.
⁵ Division of Immunotherapy, Oncode Institute, Radboudumc, Nijmegen, the Netherlands.

PMID: 38216750
DOI: 10.1093/rheumatology/keae020

Abstract

Objectives: Macrophages are key orchestrators of the osteoarthritis (OA)-associated inflammatory response. Macrophage phenotype is dependent on environmental cues like the inflammatory factor S100A8/A9. Here, we investigated how S100A9 exposure during monocyte-to-macrophage differentiation affects macrophage phenotype and function.

Methods: OA synovium cellular composition was determined using flow cytometry and multiplex immunohistochemistry. Healthy donor monocytes were differentiated towards M1- and M2-like macrophages in presence of S100A9. Macrophage markers were measured using flow cytometry and phagocytic activity was determined using pHrodo Red Zymosan A BioParticles. Gene expression was determined using qPCR. Protein secretion was measured using Luminex and ELISA.

Results: Macrophages were the dominant leucocyte subpopulation in OA synovium. They mainly presented with a M2-like phenotype, although the majority also expressed M1-like macrophage markers. Long-term exposure to S100A9 during monocyte-to-macrophage differentiation increased M2-like macrophage markers CD163 and CD206 in M1-like and M2-like differentiated cells. In addition, M1-like macrophage markers were increased in M1-like, but decreased in M2-like differentiated macrophages. In agreement with this mixed phenotype, S100A9 stimulation modestly increased expression and secretion of pro-inflammatory markers and catabolic enzymes, but also increased expression and secretion of anti-inflammatory/anabolic markers. In accordance with the upregulation of M2-like macrophage markers, S100A9 increased phagocytic activity. Finally, we indeed observed a strong association between S100A8 and S100A9 expression and the M2-like/M1-like macrophage ratio in end-stage OA synovium.

Conclusion: Chronic S100A8/A9 exposure during monocyte-to-macrophage differentiation favours differentiation towards a M2-like macrophage phenotype. The properties of these cells could help explain the catabolic/anabolic dualism in established OA joints with low-grade inflammation.

Keywords: Osteoarthritis; S100A8/A9; inflammation; macrophage differentiation; synovium.