title: TLR4, rather than TLR2, regulates wound healing through TGF-β and CCL5 expression.
abstract: BACKGROUND
  Toll-like receptors (TLRs) have a crucial role in early host defense against invading pathogens. Recent studies suggest that TLRs play important roles in non-infections inflammation and tissue repair and regeneration.
  
  
  OBJECTIVE
  To determine the roles of TLR2 and TLR4 in mouse wound healing using TLR2-deficient (TLR2(-/-)), TLR4-deficient (TLR4(-/-)), and TLR2/TLR4-deficient (TLR2/4(-/-)) mice.
  
  
  METHODS
  Open wounds made in TLR2(-/-), TLR4(-/-), and TLR2/4(-/-) mice were examined clinically and histologically. Cytokine expression in the wounded skin was also investigated. TGF-β production from macrophages stimulated by hyaluronan, a ligand for TLR2 and TLR4, was evaluated by real-time PCR.
  
  
  RESULTS
  Wound areas in TLR2(-/-), TLR4(-/-), and TLR2/4(-/-) mice were larger than wild-type mice both at days 3 and 7 after wounding, accompanied by decreased numbers of infiltrating macrophages in the dermis and decreased TGF-β and CCL5 mRNA expression in the wounded skin. Immunohistochemistry showed decreased numbers of macrophages expressing TGF-β and reduced CCL5 expression by keratinocytes in the wounded skin from TLR2(-/-), TLR4(-/-), and TLR2/4(-/-) mice compared to wild-type mice. Moreover, TGF-β production from macrophages induced by hyaluronan stimulation in vitro was significantly decreased in the absence of TLRs, especially TLR4. Interestingly, macrophages and wounded skin from TLR2(-/-) mice showed decreased TLR4 mRNA expression compared to wild-type mice, suggesting that the effect of TLR2 deficiency was at least partially dependent on decrease in TLR4. Topical application of TGF-β and CCL5 significantly improved wound healing in TLR-deficient mice.
  
  
  CONCLUSIONS
  TLR4, rather than TLR2, regulates wound healing through TGF-β and CCL5 expression.
authors.affiliation: Department of Dermatology, Faculty of Medicine, University of Tokyo, Tokyo, Japan.
authors.forename: Hiraku
authors.initials: H
authors.lastname: Suga
authors.affiliation: Department of Dermatology, Faculty of Medicine, University of Tokyo, Tokyo, Japan. Electronic address: sugayam-der@h.u-tokyo.ac.jp.
authors.forename: Makoto
authors.initials: M
authors.lastname: Sugaya
authors.affiliation: Department of Dermatology, Faculty of Medicine, University of Tokyo, Tokyo, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Fujita
authors.affiliation: Department of Dermatology, Faculty of Medicine, University of Tokyo, Tokyo, Japan.
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Asano
authors.affiliation: Department of Dermatology, Faculty of Medicine, University of Tokyo, Tokyo, Japan.
authors.forename: Yayoi
authors.initials: Y
authors.lastname: Tada
authors.affiliation: Department of Dermatology, Faculty of Medicine, University of Tokyo, Tokyo, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Kadono
authors.affiliation: Department of Dermatology, Faculty of Medicine, University of Tokyo, Tokyo, Japan. Electronic address: satos-der@h.u-tokyo.ac.jp.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Sato
mesh_terms: D000818:Animals; D018946:Chemokine CCL5 / Q000378:metabolism*; D005786:Gene Expression Regulation; D006820:Hyaluronic Acid / Q000737:chemistry; D007249:Inflammation; D008024:Ligands; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009504:Neutrophils / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D012038:Regeneration; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000502:physiology*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D014945:Wound Healing
chemical_list: C503460:Ccl5 protein, mouse; D018946:Chemokine CCL5; D008024:Ligands; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D016212:Transforming Growth Factor beta; D006820:Hyaluronic Acid
keywords: CCL5; TGF-β; TLR2; TLR4; Wound healing