title: IL-17 inhibits osteoblast differentiation and bone regeneration in rat.
abstract: OBJECTIVE
  The interleukin-17 (IL-17) family is a group of pro-inflammatory cytokines that are produced by a subset of helper T cells. IL-17 family members are not only involved in the immune response of tissues but also play a role in bone metabolism. Although the role of IL-17 in osteoclast-mediated bone resorption has been extensively studied, its role during osteoblast-mediated bone formation has rarely been investigated. In this study, we examined the effect of IL-17 on osteogenesis in rats both in vitro and in vivo.
  
  
  METHODS
  To evaluate osteogenesis in vitro, rat calvarial osteoblast precursor cells were cultured for 14 days in osteogenic medium with or without 50ng/mL IL-17. Osteogenic activity was evaluated by alkaline phosphatase and alizarin red staining. The mRNA expression of alkaline phosphatase, osteocalcin, and osterix was also measured by using real-time PCR. To test whether IL-17 affects bone formation in vivo, bone filling was examined by micro-computed tomography and histological observations at 8 weeks after critical-sized defects were made in rat calvaria.
  
  
  RESULTS
  The presence of IL-17 significantly reduced alkaline phosphatase and alizarin red staining and the expression of alkaline phosphatase, osteocalcin, and osterix in vitro. IL-17 also significantly inhibited the filling of calvarial defects in vivo.
  
  
  CONCLUSIONS
  IL-17 exerted a negative effect on osteogenesis in a rat model. In contrast to the previously reported beneficial effect on osteogenic differentiation of human mesenchymal stem cells, our results suggest a species or cell type-specific role for IL-17 in bone formation.
authors.affiliation: Department of Periodontology, School of Dentistry, Kyungpook National University, Daegu 700-412, Republic of Korea.
authors.forename: Yong-Gun
authors.initials: YG
authors.lastname: Kim
authors.affiliation: Department of Periodontology, School of Dentistry, Kyungpook National University, Daegu 700-412, Republic of Korea.
authors.forename: Jin-Woo
authors.initials: JW
authors.lastname: Park
authors.affiliation: Department of Periodontology, School of Dentistry, Kyungpook National University, Daegu 700-412, Republic of Korea.
authors.forename: Jae-Mok
authors.initials: JM
authors.lastname: Lee
authors.affiliation: Department of Periodontology, School of Dentistry, Kyungpook National University, Daegu 700-412, Republic of Korea.
authors.forename: Jo-Young
authors.initials: JY
authors.lastname: Suh
authors.affiliation: Department of Periodontology, Gangneung-Wonju National University College of Dentistry, Gangneung 210-702, Republic of Korea.
authors.forename: Jae-Kwan
authors.initials: JK
authors.lastname: Lee
authors.affiliation: Department of Periodontology, Gangneung-Wonju National University College of Dentistry, Gangneung 210-702, Republic of Korea.
authors.forename: Beom-Seok
authors.initials: BS
authors.lastname: Chang
authors.affiliation: Department of Periodontology, Gangneung-Wonju National University College of Dentistry, Gangneung 210-702, Republic of Korea. Electronic address: hsum@gwnu.ac.kr.
authors.forename: Heung-Sik
authors.initials: HS
authors.lastname: Um
authors.affiliation: Department of Biochemistry and Institute for Hard Tissue & Bio-tooth Regeneration (IHBR), School of Dentistry, Kyungpook National University, Daegu 700-421, Republic of Korea.
authors.forename: Jae-Young
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Department of Biochemistry and Institute for Hard Tissue & Bio-tooth Regeneration (IHBR), School of Dentistry, Kyungpook National University, Daegu 700-421, Republic of Korea. Electronic address: ylee@knu.ac.kr.
authors.forename: Youngkyun
authors.initials: Y
authors.lastname: Lee
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001861:Bone Regeneration / Q000187:drug effects*; D018929:Cell Culture Techniques; D002454:Cell Differentiation / Q000187:drug effects; D020381:Interleukin-17 / Q000494:pharmacology*; D010006:Osteoblasts / Q000187:drug effects*; D015675:Osteocalcin / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D012886:Skull / Q000166:cytology; D013194:Staining and Labeling; D014157:Transcription Factors / Q000378:metabolism; D055114:X-Ray Microtomography
chemical_list: D020381:Interleukin-17; D012333:RNA, Messenger; C495181:Sp7 protein, rat; D014157:Transcription Factors; D015675:Osteocalcin; D000469:Alkaline Phosphatase
keywords: Bone formation; Differentiation; IL-17; Rat calvarial osteoblast