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Koroth J, Chitwood C, Kumar R, Lin WH, Reves BT, Boyce T, Reineke TM, Ellingson AM, Johnson CP, Stone LS, Chaffin KC, Simha NK, Ogle BM, Bradley EW. Identification of a novel, MSC-induced macrophage subtype via single-cell sequencing: implications for intervertebral disc degeneration therapy. Front Cell Dev Biol 2024; 11:1286011. [PMID: 38274272 PMCID: PMC10808728 DOI: 10.3389/fcell.2023.1286011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Accepted: 12/22/2023] [Indexed: 01/27/2024] Open
Abstract
Intervertebral disc (IVD) degeneration is a common pathological condition associated with low back pain. Recent evidence suggests that mesenchymal signaling cells (MSCs) promote IVD regeneration, but underlying mechanisms remain poorly defined. One postulated mechanism is via modulation of macrophage phenotypes. In this manuscript, we tested the hypothesis that MSCs produce trophic factors that alter macrophage subsets. To this end, we collected conditioned medium from human, bone marrow-derived STRO3+ MSCs. We then cultured human bone marrow-derived macrophages in MSC conditioned medium (CM) and performed single cell RNA-sequencing. Comparative analyses between macrophages cultured in hypoxic and normoxic MSC CM showed large overlap between macrophage subsets; however, we identified a unique hypoxic MSC CM-induced macrophage cluster. To determine if factors from MSC CM simulated effects of the anti-inflammatory cytokine IL-4, we integrated the data from macrophages cultured in hypoxic MSC CM with and without IL-4 addition. Integration of these data sets showed considerable overlap, demonstrating that hypoxic MSC CM simulates the effects of IL-4. Interestingly, macrophages cultured in normoxic MSC CM in the absence of IL-4 did not significantly contribute to the unique cluster within our comparison analyses and showed differential TGF-β signaling; thus, normoxic conditions did not approximate IL-4. In addition, TGF-β neutralization partially limited the effects of MSC CM. In conclusion, our study identified a unique macrophage subset induced by MSCs within hypoxic conditions and supports that MSCs alter macrophage phenotypes through TGF-β-dependent mechanisms.
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Affiliation(s)
- Jinsha Koroth
- Department of Orthopedic Surgery, Medical School, University of Minnesota, Minneapolis, MN, United States
| | - Casey Chitwood
- Department of Biomedical Engineering, College of Science and Engineering, University of Minnesota, Minneapolis, MN, United States
| | - Ramya Kumar
- Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, CO, United States
- Department of Chemistry, College of Science and Engineering, University of Minnesota, Minneapolis, MN, United States
| | - Wei-Han Lin
- Department of Biomedical Engineering, College of Science and Engineering, University of Minnesota, Minneapolis, MN, United States
| | | | | | - Theresa M. Reineke
- Department of Chemistry, College of Science and Engineering, University of Minnesota, Minneapolis, MN, United States
- Stem Cell Institute, University of Minnesota, Minneapolis, MN, United States
| | - Arin M. Ellingson
- Department of Orthopedic Surgery, Medical School, University of Minnesota, Minneapolis, MN, United States
- Department of Rehabilitation Medicine, School of Medicine, University of Minnesota, Minneapolis, MN, United States
| | - Casey P. Johnson
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, United States
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States
| | - Laura S. Stone
- Department of Anesthesiology, School of Medicine, University of Minnesota, Minneapolis, MN, United States
| | | | | | - Brenda M. Ogle
- Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, CO, United States
- Stem Cell Institute, University of Minnesota, Minneapolis, MN, United States
| | - Elizabeth W. Bradley
- Department of Orthopedic Surgery, Medical School, University of Minnesota, Minneapolis, MN, United States
- Stem Cell Institute, University of Minnesota, Minneapolis, MN, United States
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