title: Regulation of macrophage migration and activity by high-mobility group box 1 protein released from periodontal ligament cells during orthodontically induced periodontal repair: an in vitro and in vivo experimental study.
abstract: OBJECTIVE
  Recent studies have shown that periodontal ligament (PDL) cells interact with macrophages from the immune system during orthodontically induced repair of periodontal tissue. Hypothesizing that high-mobility group box 1 (HMGB1) protein is released by mechanically stressed PDL cells into the extracellular space and has a role in mediating the local immune response by acting as an "alarmin", this study was performed to further elucidate these cellular interactions, with a special focus on the impact of proinflammatory mediators secreted by PDL cells on macrophage physiology.
  
  
  METHODS
  The study included an in vivo part in which orthodontic stress was induced in rats and their PDL analyzed for expression of HMGB1 by immunohistochemistry after 5 days of tooth movement. In the in vitro part, human PDL cells were subjected to compressive loading, followed by stimulating human macrophages with conditioned supernatants of these stressed PDL cells and analyzing how mediators that had been released by these cells into the medium would impact macrophage physiology. Assays for macrophage migration and osteoclast differentiation were used in addition to immunohistochemistry, enzyme-linked immunosorbent assays, and western blotting.
  
  
  RESULTS
  Induction of mechanical stress was found to upregulate HMGB1 expression both in vivo and in vitro. At the same time, translocation HMGB1 from nuclei into cytoplasm was observed. Culturing macrophages in conditioned PDL cell medium was associated with enhanced chemotactic migration and osteoclast differentiation. Addition of anti-HMGB1 antibodies to inhibit HMGB1 in the conditioned medium was found to significantly attenuate these effects. A less marked increase of migration and osteoclast differentiation by macrophages was observed after isolated addition of HMGB1, at its observed pathological concentration, to nonconditioned medium.
  
  
  CONCLUSIONS
  This study clearly indicates an immunomodulatory potential of human PDL cells via release of mediators, including HMGB1 protein. Our finding that these mediators modify the migration and differentiation of macrophages as a function of periodontal repair during orthodontic treatment broadens the theoretical basis toward developing interventional strategies to avoid orthodontically induced root resorption.
authors: Department of Orthodontics, University of Bonn, Rhenish Friedrich-Wilhelm University, Welschnonnenstr. 17, 53111, Bonn, Germany, michael.wolf@ukb.uni-bonn.de.
authors: Michael
authors: M
authors: Wolf
authors: Stefan
authors: S
authors: Lossdörfer
authors: Rogerio
authors: R
authors: Craveiro
authors: Werner
authors: W
authors: Götz
authors: Andreas
authors: A
authors: Jäger
mesh_terms: D000818:Animals; D002465:Cell Movement; D002478:Cells, Cultured; D024243:HMGB1 Protein / Q000276:immunology*; D006801:Humans; D056747:Immunomodulation / Q000276:immunology; D066298:In Vitro Techniques; D008262:Macrophage Activation / Q000276:immunology; D008264:Macrophages / Q000166:cytology / Q000276:immunology*; D040542:Mechanotransduction, Cellular / Q000276:immunology*; D010513:Periodontal Ligament / Q000166:cytology* / Q000276:immunology*; D051381:Rats; D017208:Rats, Wistar; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques / Q000379:methods*
chemical_list: D024243:HMGB1 Protein; C585491:HMGB1 protein, human; C104200:Hbp1 protein, rat
references: J Exp Med. 2000 Aug 21;192(4):565-70
references: 10952726
references: J Periodontal Res. 2008 Apr;43(2):168-73
references: 18302618
references: J Periodontal Res. 2008 Feb;43(1):76-83
references: 18067550
references: Histochemistry. 1993 Aug;100(2):161-6
references: 8244767
references: Arch Oral Biol. 1985;30(10):739-43
references: 3866521
references: Cytokine Growth Factor Rev. 2006 Jun;17(3):189-201
references: 16513409
references: J Interferon Cytokine Res. 1999 Sep;19(9):1047-52
references: 10505748
references: J Bone Miner Res. 2008 Jul;23(7):1084-96
references: 18302500
references: Clin Oral Investig. 2011 Dec;15(6):941-52
references: 20697756
references: J Cell Physiol. 2008 Mar;214(3):730-9
references: 17786958
references: J Cell Physiol. 2006 May;207(2):480-90
references: 16419037
references: J Periodontal Res. 2006 Dec;41(6):547-53
references: 17076780
references: Arthritis Res Ther. 2011 Aug 26;13(4):R136
references: 21871094
references: J Immunol. 2005 Jun 15;174(12):7506-15
references: 15944249
references: Eur J Orthod. 2005 Feb;27(1):1-11
references: 15743857
references: Lancet. 2004 Jul 10-16;364(9429):149-55
references: 15246727
references: J Dent Res. 1954 Aug;33(4):481-6
references: 13184036
references: Science. 1999 Jul 9;285(5425):248-51
references: 10398600
references: J Periodontal Res. 2011 Jun;46(3):318-26
references: 21332473
references: Clin Oral Investig. 2010 Feb;14(1):89-98
references: 19280233
references: Tissue Eng Part A. 2012 Sep;18(17-18):1849-56
references: 22497226
references: Tissue Eng. 2007 Apr;13(4):767-73
references: 17432951
references: J Dent Res. 1998 Feb;77(2):393-405
references: 9465172
references: J Cell Biochem. 2010 Dec 1;111(5):1310-20
references: 20803525
references: Oral Microbiol Immunol. 2009 Aug;24(4):292-8
references: 19572890
references: Nature. 2002 Jul 11;418(6894):191-5
references: 12110890
references: Innate Immun. 2012 Oct;18(5):745-52
references: 22436844
references: Am J Orthod Dentofacial Orthop. 2001 Mar;119(3):307-12
references: 11244425
references: Arch Oral Biol. 2011 May;56(5):466-73
references: 21193170
references: Cell Immunol. 2012;272(2):137-43
references: 22119482