Investigating Adhesion Molecules in Stem Cell - Immune Cell Interactions Using Organoids

Immune cell-mesenchymal stem cell interactions modulate repair and regeneration, with cell-to-cell interactions being a necessary component facilitating this crosstalk. This study used a collagen-based organoid model to examine direct cell-to-cell interactions between stem cells from apical papilla (SCAP) and macrophages (MQ). The aim was to better understand how adhesion molecules contribute to apical periodontitis dynamics in the immature permanent tooth.

Two-dimensional SCAP-MQ co-cultures were compared to three-dimensional (3D) SCAP-MQ self-assembled tissue constructs under 3 conditions: non-stimulated, lipopolysaccharide (LPS), and interleukin (IL)-4 for up to 7 days. Expression of 5 candidate adhesion molecules (CD200, CD200 R, intercellular adhesion molecule (ICAM)-1, N-cadherin, and lymphocyte function-associated antigen (LFA)-1) were assessed by quantitative real time polymerase chain reaction and confocal microscopy.

LPS decreases CD200 and CD200 R immunofluorescence in an organoid model (P < .05). N-CADHERIN gene expression increased on day 5 in the 3D model in response to LPS (P < .05). LFA-1 showed a trend toward increased immunofluorescence in the juxtacrine zone of the organoid model under LPS stimulation, though this difference was not significant. ICAM-1 gene expression in the 2D model increased in response to LPS (P < .05) but no change was observed with IL-4.

Extracellular collagen and inflammatory conditions modulate adhesion molecule expression in SCAP-MQ co-cultures. LPS promoted N-cadherin, ICAM-1, and LFA-1 expression, while IL-4 increased CD200, CD200 R, and ICAM-1. These findings highlight the molecular mechanisms underlying SCAP-MQ interactions and validate the use of 3D models to potentially inform future therapeutic strategies for enhancing pulpal regeneration.