Expression and function of toll-like receptors in human circulating endothelial colony forming cells

• Published in: Immunology letters Vol. 168; no. 1; pp. 98 - 104
• Main Authors: Mazzucchelli, Iolanda, Lisini, Daniela, Garofoli, Francesca, Dragoni, Silvia, Angelini, Micol, Pozzi, Margherita, Bonetti, Elisa, Tzialla, Chryssoula, Kramer, Boris W., Spinillo, Arsenio, Maccario, Rita, Rosti, Vittorio, Moccia, Francesco, Borghesi, Alessandro, Stronati, Mauro
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.11.2015
• Subjects: Adult; Allergy and Immunology; Ca2; Calcium - metabolism; Cell Differentiation - genetics; Cell Differentiation - immunology; Cell Proliferation - genetics; Cells, Cultured; Cytokines - immunology; Cytokines - metabolism; Dose-Response Relationship, Drug; ECFC; Endothelial Cells - drug effects; Endothelial Cells - immunology; Endothelial Cells - metabolism; Endothelial colony forming cells; Fetal Blood - cytology; Gene Expression; Hematopoietic Stem Cells - drug effects; Hematopoietic Stem Cells - immunology; Hematopoietic Stem Cells - metabolism; Human Umbilical Vein Endothelial Cells - drug effects; Human Umbilical Vein Endothelial Cells - immunology; Human Umbilical Vein Endothelial Cells - metabolism; Humans; Leukocytes, Mononuclear - drug effects; Leukocytes, Mononuclear - immunology; Leukocytes, Mononuclear - metabolism; Lipopolysaccharides - immunology; Lipopolysaccharides - pharmacology; LPS; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; RNA, Messenger - metabolism; Stem Cells - immunology; Stem Cells - metabolism; Time Factors; TLR; Toll-Like Receptor 4 - blood; Toll-Like Receptor 4 - genetics; Toll-Like Receptor 4 - immunology; Toll-like receptors; Toll-Like Receptors - blood; Toll-Like Receptors - genetics; Toll-Like Receptors - immunology; Toll-like receptors; ECFC; TLR; Ca2; Endothelial colony forming cells; LPS; Ca 2; Ca(2+)
• ISSN: 0165-2478; 1879-0542
• DOI: 10.1016/j.imlet.2015.09.014

•Toll-like receptors (TLRs) in endothelial colony forming cells (ECFCs) are studied.•All TLRs from 1 to 10 are detectable in ECFCs.•TLR4 mRNA levels are high in ECFCs.•LPS induces cytokine production but has no effect on ECFC growth or differentiation.•LPS induces no increase in intracellular Ca2+ concentrations. Mature endothelial cells are known to sense microbial products through toll-like receptors (TLRs), a family of membrane proteins which serve as pathogen recognition and signaling elements; however, there are limited data in the literature about the expression and function of TLRs in human circulating endothelial colony forming cells (ECFCs), which are considered the most likely endothelial precursors. We expanded and differentiated in vitro umbilical cord blood (UCB) and adult peripheral blood (PB) ECFCs and studied the expression of TLR1 to TLR10 mRNA by qPCR analysis, and we further characterized TLR function in ECFCs through functional assays including in vitro ECFC growth and differentiation, assessment of cytokine production, and measurement of intracellular Ca2+ signals. Both UCB- and PB-ECFCs had detectable mRNA levels of all the TLRs from 1 to 10; TLR4, a sensor of Gram-negative bacterial lipopolysaccharide (LPS), had a higher level compared to other TLRs. Exposure to LPS induced cytokine production, although with less efficiency compared to PB-mononuclear cells. However, no effect of LPS was seen on ECFC growth and differentiation, and no increase in intracellular Ca2+ concentrations, which is essential for ECFC proliferation, was observed after exposure to increasing amounts of LPS. Our data show that all TLRs from 1 to 10 are constitutively expressed in ECFCs, and suggest that TLR4 is functional in ECFCs, but its activation through its ligand LPS does not affect ECFC growth and differentiation.