title: IL-6 is produced by adipose-derived stromal cells and promotes osteogenesis.
abstract: Although Toll-like receptors (TLRs) have been implicated in the regulation of stem cell functions, their role in osteogenic differentiation of adipose-derived stromal cells (ASCs) has not been reported. We found that ASCs express a restricted subset of TLRs, including TLR1-TLR5, and that TLR agonists such as Pam3CSK4 (TLR1/2 agonist), polyinosinic:polycytidylic acid (TLR3 agonist), lipopolysaccharide (TLR4 agonist), and flagellin (TLR5 agonist), but not R848 (TLR7/8 agonist), consistently induced osteogenic differentiation in murine-derived ASCs, which coincided with the TLR expression pattern of ASCs. Cytokine expression profiles induced by TLR agonists and results from subsequent functional assays indicated that interleukin-6 (IL-6) together with soluble IL-6 receptor (sIL-6R) enhanced osteogenic differentiation of ASCs by activating STAT3. Small interfering RNA (siRNA)-mediated STAT3-silencing blunted osteogenesis and the expression of osteogenic markers, whereas STAT3 overexpression resulted in an increase in osteogenesis. Consistently, STAT3 inhibitor treatment reduced osteogenesis, STAT3 phosphorylation, and expression of osteogenic markers including osterix. Chromatin immunoprecipitation (ChIP) assays indicated that STAT3 binding to the STAT3-binding sites on the osterix promoter increased during IL-6-stimulated osteogenesis. Our results thus establish TLRs as novel regulators of ASCs which signal through IL-6/STAT3 pathway and induce osterix expression as a part of the osteogenesis.
authors.affiliation: Department of Life Science and the Research Center for Cellular Homeostasis, Ewha Womans University, Seoul 120-750, Republic of Korea.
authors.forename: Jeong-Eun
authors.initials: JE
authors.lastname: Huh
authors.affiliation: Department of Life Science and the Research Center for Cellular Homeostasis, Ewha Womans University, Seoul 120-750, Republic of Korea; Department of Bioinspired Science, Ewha Womans University, Seoul 120-750, Republic of Korea. Electronic address: leesy@ewha.ac.kr.
authors.forename: Soo Young
authors.initials: SY
authors.lastname: Lee
mesh_terms: D000273:Adipose Tissue / Q000166:cytology*; D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D015850:Interleukin-6 / Q000096:biosynthesis*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010012:Osteogenesis / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D019947:Receptors, Interleukin-6 / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors / Q000378:metabolism; D012995:Solubility; D000076182:Sp7 Transcription Factor; D017154:Stromal Cells / Q000166:cytology / Q000378:metabolism; D051193:Toll-Like Receptors / Q000819:agonists / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D015850:Interleukin-6; D019947:Receptors, Interleukin-6; D050796:STAT3 Transcription Factor; D000076182:Sp7 Transcription Factor; C479466:Sp7 protein, mouse; C494087:Stat3 protein, mouse; D051193:Toll-Like Receptors; D014157:Transcription Factors
keywords: 4′,6-diamidino-2-phenylindole; ALP; ARS; ASCs; Adipose-derived stromal cell; Alizarin Red S; DAPI; GAPDH; IL-6; LPS; MSCs; Osteogenesis; Osterix; STAT3; TLR; TLRs; Toll-like receptors; VK; adipose-derived stromal cells; alkaline phosphatase; glyceraldehyde 3 phosphate dehydrogenase; lipopolysaccharide; mesenchymal stem cells; poly-IC; polyinosinic:polycytidylic acid; sIL-6R; siRNA; small interfering RNA; soluble IL-6 receptor; von Kossa