TLR-mediated Immunomodulation by Gingival Stem Cells

Objectives: Therapeutic applications of stem/progenitor cells (MSCs) embrace a wide variety of disorders, including inflammatory diseases, degenerative conditions, autoimmune disorders and allograft rejections. Biological properties of MSCs can be altered by diverse factors, including the activation of Toll-like Receptors (TLRs). The aim of the present study is to characterize the TLR mediated immunomodulatory response in gingival margin derived MSCs (G-MSCs).
Methods: Following cell isolation from the free gingival margin (n=5), cells were immunomagnetically sorted using anti-STRO-1 antibodies, seeded and cultured in basic medium to attain colony forming units (CFUs). G-MSCs were characterized for the expression of CD14, CD34, CD45, CD73, CD90 and CD105 by flow-cytometry, in addition to their multilineage differentiation potential. Consequently, the expression of the TLRs 1-10 was analysed by flow-cytometry. To test the effect of TLR stimulation on G-MSCs’ immunomodulatory functions six TLR specific ligands were added for 24 hours and a control group was left unstimulated. m-RNA was extracted and inspected for the expression of the immune regulating genes IL10, IL12, IL1β, TNFα and IDO by polymerase chain reaction.
Results: G-MSCs showed all predefined characteristics of stem/progenitor cells. G-MSCs expressed TLRs 1, 2, 3, 4, 5, 7, 8, 9 and 10. On m-RNA level, G-MSCs expressed the explored immune regulating genes (Table 1). Cells activated by Poly (I:C) (TLR3 ligand) displayed a significantly higher expression of TNFα (p<0.05) and IDO (p<0.05), beside a significant downregulation of IL12 (p<0.05, Wilcoxon Signed Ranks Test). FSL-1 (TLR2/6 ligand) displayed a significantly upregulated TNFα expression (p<0.05, Wilcoxon Signed Ranks Test).
Conclusions: The current study presents the distinctive TLR mediated expression of immunomodulatory factors in G-MSCs with a potential impact on therapeutic applications. Targeted ligation or blocking of G-MSCs’ TLRs might provide better therapeutic results or expectations in future clinical applications.