Macrophage Subtypes Distinctly Impact Intervertebral Disc Inflammation and Extracellular Matrix Composition.

Area of Science:

• Biomedical Engineering
• Cell Biology
• Immunology

Background:

• Intervertebral disc (IVD) degeneration involves extracellular matrix (ECM) changes and inflammation, with macrophage roles unclear.
• The specific impacts of M1 (pro-inflammatory) and M2 (anti-inflammatory) macrophages on IVD health are unknown.
• A novel in vitro macrophage-IVD explant co-culture system is needed to study these interactions.

Purpose of the Study:

• To investigate the individual and combined effects of IVD cells and macrophages on ECM composition and inflammation.
• To determine the distinct roles of M1 and M2 polarized macrophages in modulating IVD degeneration.
• To establish and utilize a co-culture system for studying macrophage-IVD cell crosstalk via paracrine signaling.

Main Methods:

• Rat lumbar IVDs were cultured in agarose, and bone marrow-derived macrophages were polarized to M1 or M2.
• IVD explants were stimulated with TNFα and co-cultured with M1 or M2 macrophages for 14 days.
• ECM changes (GAG, collagen) and inflammatory markers (NO, cytokines) were analyzed.

Main Results:

• TNFα stimulation induced inflammation and altered ECM in IVDs.
• Both M1 and M2 macrophages counteracted TNFα-induced collagen degradation.
• M1 macrophages exacerbated inflammation (increased NO, IL-6), while M2 macrophages reduced pro-inflammatory mediators and increased anti-inflammatory IL-13.

Conclusions:

• In vitro co-culture of macrophages and IVD explants impacts both inflammation and ECM composition.
• M1 and M2 macrophages differentially modulate inflammatory responses, with M2 macrophages offering potential protective effects.
• The developed co-culture system enables exclusive study of paracrine signaling in macrophage-IVD interactions.