Specific inflammatory osteoclast precursors induced during chronic inflammation give rise to highly active osteoclasts associated with inflammatory bone loss

Yaron Meirow; Milena Jovanovic; Yuval Zur; Juliana Habib; Daniele Filippo Colombo; Nira Twaik; Hadas Ashkenazi-Preiser; Kerem Ben-Meir; Ivan Mikula Jr; Or Reuven; Guy Kariv; Leonor Daniel; Saja Baraghithy; Yehuda Klein; Jeroen Krijgsveld; Noam Levaot; Michal Baniyash

doi:10.1038/s41413-022-00206-z

Specific inflammatory osteoclast precursors induced during chronic inflammation give rise to highly active osteoclasts associated with inflammatory bone loss

Bone Res. 2022 Apr 8;10(1):36. doi: 10.1038/s41413-022-00206-z.

Authors

Yaron Meirow¹, Milena Jovanovic², Yuval Zur², Juliana Habib², Daniele Filippo Colombo³, Nira Twaik¹, Hadas Ashkenazi-Preiser¹, Kerem Ben-Meir¹, Ivan Mikula Jr¹, Or Reuven¹, Guy Kariv¹, Leonor Daniel¹, Saja Baraghithy⁴, Yehuda Klein⁵, Jeroen Krijgsveld^{3

6}, Noam Levaot², Michal Baniyash⁷

Affiliations

¹ The Concern Foundation Laboratories at The Lautenberg Center for Immunology and Cancer Research, Israel-Canada Medical Research Institute, Faculty of Medicine, The Hebrew University, Jerusalem, Israel.
² Department of Physiology and Cell Biology, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
³ Division of Proteomics of Stem Cells and Cancer, German Cancer Research Center (DKFZ), Heidelberg, Germany.
⁴ Institute for Drug Research, Faculty of Medicine, The Hebrew University, Jerusalem, Israel.
⁵ Hebrew University-Hadassah School of Dental Medicine, Jerusalem, Israel.
⁶ Heidelberg University, Medical Faculty, Heidelberg, Germany.
⁷ The Concern Foundation Laboratories at The Lautenberg Center for Immunology and Cancer Research, Israel-Canada Medical Research Institute, Faculty of Medicine, The Hebrew University, Jerusalem, Israel. michalb@ekmd.huji.ac.il.

Abstract

Elevated osteoclast (OC) activity is a major contributor to inflammatory bone loss (IBL) during chronic inflammatory diseases. However, the specific OC precursors (OCPs) responding to inflammatory cues and the underlying mechanisms leading to IBL are poorly understood. We identified two distinct OCP subsets: Ly6C^hiCD11b^hi inflammatory OCPs (iOCPs) induced during chronic inflammation, and homeostatic Ly6C^hiCD11b^lo OCPs (hOCPs) which remained unchanged. Functional and proteomic characterization revealed that while iOCPs were rare and displayed low osteoclastogenic potential under normal conditions, they expanded during chronic inflammation and generated OCs with enhanced activity. In contrast, hOCPs were abundant and manifested high osteoclastogenic potential under normal conditions but generated OCs with low activity and were unresponsive to the inflammatory environment. Osteoclasts derived from iOCPs expressed higher levels of resorptive and metabolic proteins than those generated from hOCPs, highlighting that different osteoclast populations are formed by distinct precursors. We further identified the TNF-α and S100A8/A9 proteins as key regulators that control the iOCP response during chronic inflammation. Furthermore, we demonstrated that the response of iOCPs but not that of hOCPs was abrogated in tnf-α^-/- mice, in correlation with attenuated IBL. Our findings suggest a central role for iOCPs in IBL induction. iOCPs can serve as potential biomarkers for IBL detection and possibly as new therapeutic targets to combat IBL in a wide range of inflammatory conditions.