Conditioned Medium from IFNγ-Pretreated Human Gingival Mesenchymal Stromal Cells Enhances the Immunomodulatory Effects on Neutrophils.

Introduction/ Objective: Neutrophils are crucial for an effective innate immune response. However, overactivation is associated with chronic inflammation, as in systemic lupus erythematosus (SLE). Gingival mesenchymal stromal cells (GMSCs) are used as anti-inflammatory therapies because they possess strong immunomodulatory properties, primarily acting through paracrine mechanisms. GMSCs exhibit immunoplasticity in response to their microenvironment and adjust their secretion profile. This study aimed to investigate the effects of conditioned media derived from human gingival mesenchymal stromal cells (hGMSC-CM) or from cells pretreated with IFNγ (hGMSCγ- CM) on neutrophil antimicrobial and proinflammatory functions.

Methods

hGMSCs were isolated to meet the criteria of the International Society for Cell & Gene Therapy (ISCT). Neutrophil intracellular reactive oxygen species (ROS) production; neutrophil elastase (NE), cathepsin G (CG), and myeloperoxidase (MPO) enzymatic activities; induction of lytic and vital neutrophil extracellular traps (NETs); and bacterial uptake and engulfment were analyzed using flow cytometry, photometric methods, and fluorescence and confocal microscopy.

Results

Both hGMSC-derived CMs significantly reduced intracellular ROS levels, reduced the enzymatic activities of MPO, CG, and NE by decreasing degranulation, and diminished NET formation (DNA, LL37, and PAD4) through both the lytic and vital pathways, including NET production observed in an inflammatory environment using plasma from SLE patients.

Discussion

These inhibitory effects were more pronounced with hGMSCγ-CM. Interestingly, hGMSCγ-CM did not impair bacterial uptake, engulfment, or neutrophil microbicidal activity against Staphylococcus aureus and Escherichia coli, thereby maintaining the functional balance of neutrophils.

Conclusion

These findings support the use of hGMSCγ-CM as a cell-free biological product for therapies targeting inflammation driven by neutrophil overactivation.