Deciphering Stem Cell From Apical Papilla-Macrophage Choreography Using a Novel 3-dimensional Organoid System

Area of Science:

• Regenerative Medicine
• Biomaterials Science
• Immunology

Background:

• Mesenchymal stem cell and immune cell crosstalk is crucial for tissue repair and regeneration.
• Understanding stem cells from apical papilla (SCAPs) and macrophage interactions is key to elucidating cellular signaling in inflammation and repair.

Purpose of the Study:

• To investigate SCAP-macrophage interactions within a novel 3D tissue construct.
• To comprehensively understand the cellular signaling mechanisms governing inflammation and repair in a dental context.

Main Methods:

• SCAPs and macrophages were cultured in 3D collagen constructs within 3D-printed molds.
• Constructs were exposed to no stimulation, lipopolysaccharide (LPS), or interleukin-4 (IL-4) for 14 days.
• Evaluated cellular interactions, inflammatory mediators, surface markers, transcription factors, and SCAP differentiation markers using advanced imaging and cytokine profiling.

Main Results:

• LPS stimulation induced pro-inflammatory responses and distinct macrophage polarization (higher pSTAT6/pSTAT1 ratio, decreased CD206).
• IL-4 stimulation promoted alternative macrophage polarization, indicated by an equal pSTAT6/pSTAT1 ratio, increased CD206, and enhanced anti-inflammatory cytokine secretion (IL-1RA, IL-10, TGF-β1).
• These polarized macrophages influenced SCAP differentiation and tissue modeling.

Conclusions:

• A novel 3D organoid system effectively analyzed SCAP-macrophage interactions during inflammation and healing.
• The study provides significant insights into the periapical dynamics of immature teeth, particularly concerning immune cell-stem cell communication.
• Findings highlight the role of macrophage polarization in modulating SCAP behavior and tissue regeneration.