title: Bach1 deficiency reduces severity of osteoarthritis through upregulation of heme oxygenase-1.
abstract: BACKGROUND
  BTB and CNC homology 1 (Bach1) is a transcriptional repressor of Heme oxygenase-1 (HO-1), which is cytoprotective through its antioxidant effects. The objective of this study was to define the role of Bach1 in cartilage homeostasis and osteoarthritis (OA) development using in vitro models and Bach1 (-/-) mice.
  
  
  METHODS
  HO-1 expression in Bach1 (-/-) mice was analyzed by real-time PCR, immunohistochemistry and immunoblotting. Knee joints from Bach1 (-/-) and wild-type mice with age-related OA and surgically-induced OA were evaluated by OA scoring systems. Levels of autophagy proteins and superoxide dismutase 2 (SOD2) were determined by immunohistochemistry. The relationship between HO-1 and the protective effects for OA was determined in chondrocytes treated with small interfering RNA (siRNA) targeting HO-1 gene.
  
  
  RESULTS
  HO-1 expression decreased with aging in articular cartilages and menisci of mouse knees. Bach1 (-/-) mice showed reduced severity of age-related OA and surgically-induced OA compared with wild-type mice. Microtubule-associated protein 1 light chain 3 (LC3), autophagy marker, and SOD2 were increased in articular cartilage of Bach1 (-/-) mice compared with wild-type mice. Interleukin-1β (IL-1β) induced a significant increase in Adamts-5 in wild-type chondrocytes but not in Bach1(-/-) chondrocytes. The expression of SOD2 and the suppression of apoptosis in Bach1 (-/-) chondrocytes were mediated by HO-1.
  
  
  CONCLUSIONS
  Bach1 deficiency reduces the severity of OA-like changes. This may be due to maintenance of cartilage homeostasis and joint health by antioxidant effects through HO-1 and downregulation of extracellular matrix degrading enzymes. These results suggest that inactivation of Bach1 is a novel target and signaling pathway in OA prevention.
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Hiroshima, 734-8551, Japan. ttakada65@gmail.com.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Takada
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Hiroshima, 734-8551, Japan. miyaki@hiroshima-u.ac.jp.|Department of Regenerative Medicine, Hiroshima University Hospital, 1-2-3 Kasumi, Hiroshima, 734-8551, Japan. miyaki@hiroshima-u.ac.jp.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Miyaki
authors.affiliation: Department of Regenerative Medicine, Hiroshima University Hospital, 1-2-3 Kasumi, Hiroshima, 734-8551, Japan. tobikowa@gmail.com.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ishitobi
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Hiroshima, 734-8551, Japan. b091644@hiroshima-u.ac.jp.
authors.forename: Yuya
authors.initials: Y
authors.lastname: Hirai
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Hiroshima, 734-8551, Japan. tnakasa0@gmail.com.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Nakasa
authors.affiliation: Department of Biochemistry, Tohoku University Graduate School of Medicine, 2-1 Seiryo, Aoba, Sendai, Miyagi, 980-8575, Japan. igarak@m.tains.tohoku.ac.jp.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Igarashi
authors.affiliation: Department of Molecular and Experimental Medicine, The Scripps Research Institute, 10550 N Torrey Pines Road, La Jolla, CA, 92037, USA. mlotz@scripps.edu.
authors.forename: Martin K
authors.initials: MK
authors.lastname: Lotz
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Hiroshima, 734-8551, Japan. ochim@hiroshima-u.ac.jp.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Ochi
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D050976:Basic-Leucine Zipper Transcription Factors / Q000172:deficiency* / Q000235:genetics; D019902:Chondrocytes / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology*; D051547:Heme Oxygenase-1 / Q000096:biosynthesis* / Q000235:genetics; D015151:Immunoblotting; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D020411:Oligonucleotide Array Sequence Analysis; D010003:Osteoarthritis / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D034741:RNA, Small Interfering; D060888:Real-Time Polymerase Chain Reaction; D014162:Transfection; D015854:Up-Regulation
chemical_list: C486316:Bach1 protein, mouse; D050976:Basic-Leucine Zipper Transcription Factors; D008565:Membrane Proteins; D034741:RNA, Small Interfering; D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse