title: Overexpression of SPACIA1/SAAL1, a newly identified gene that is involved in synoviocyte proliferation, accelerates the progression of synovitis in mice and humans.
abstract: OBJECTIVE
  To identify novel genes associated with dysregulated proliferation of activated synovial fibroblasts, which are involved in arthritic joint destruction.
  
  
  METHODS
  We performed transcriptome analysis to identify genes that were up-regulated in the foot joints of mice with collagen-induced arthritis (CIA). The effect of candidate genes on proliferation of synovial fibroblasts was screened using antisense oligodeoxynucleotides and small interfering RNAs (siRNAs). We characterized the expression and function of a novel gene, synoviocyte proliferation-associated in collagen-induced arthritis 1 (SPACIA1)/serum amyloid A-like 1 (SAAL1) using antibodies and siRNA and established transgenic mice to examine the effect of SPACIA1/SAAL1 overexpression in CIA.
  
  
  RESULTS
  Human and mouse SPACIA1/SAAL1 encoded 474 amino acid proteins that shared 80% homology. SPACIA1/SAAL1 was primarily expressed in the nucleus of rheumatoid arthritis (RA) synovial fibroblasts and was highly expressed in the hyperplastic lining of inflamed synovium. In addition, its expression level in RA- or osteoarthritis (OA)-affected synovial tissue was positively correlated with the thickness of the synovial lining. Furthermore, SPACIA1/SAAL1 siRNA inhibited the proliferation of synovial fibroblasts, especially tumor necrosis factor α-induced synovial fibroblasts, by blocking entry into the S phase without inducing apoptosis. Finally, transgenic mice overexpressing SPACIA1/SAAL1 exhibited early onset and rapid progression of CIA.
  
  
  CONCLUSIONS
  These results suggest that SPACIA1/SAAL1 is necessary for abnormal proliferation of synovial fibroblasts and its overexpression is associated with the progression of synovitis in mice and humans. Thus, therapy targeting SPACIA1/SAAL1 might have potential as an inhibitor of synovial proliferation in RA and/or OA.
authors: St. Marianna University School of Medicine, Kawasaki, Japan.
authors: Tomoo
authors: T
authors: Sato
authors: Ryoji
authors: R
authors: Fujii
authors: Koji
authors: K
authors: Konomi
authors: Naoko
authors: N
authors: Yagishita
authors: Satoko
authors: S
authors: Aratani
authors: Natsumi
authors: N
authors: Araya
authors: Hiroyuki
authors: H
authors: Aono
authors: Kazuo
authors: K
authors: Yudoh
authors: Noboru
authors: N
authors: Suzuki
authors: Moroe
authors: M
authors: Beppu
authors: Yoshihisa
authors: Y
authors: Yamano
authors: Kusuki
authors: K
authors: Nishioka
authors: Toshihiro
authors: T
authors: Nakajima
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001169:Arthritis, Experimental / Q000473:pathology / Q000503:physiopathology; D001172:Arthritis, Rheumatoid / Q000473:pathology / Q000503:physiopathology; D049109:Cell Proliferation; D004195:Disease Models, Animal; D018450:Disease Progression; D005786:Gene Expression Regulation / Q000502:physiology; D005796:Genes / Q000502:physiology*; D006801:Humans; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D010003:Osteoarthritis / Q000473:pathology / Q000503:physiopathology; D000685:Serum Amyloid A Protein / Q000235:genetics / Q000502:physiology; D013583:Synovial Membrane / Q000473:pathology* / Q000503:physiopathology*; D013585:Synovitis / Q000473:pathology* / Q000503:physiopathology*; D059467:Transcriptome / Q000502:physiology; D015854:Up-Regulation / Q000502:physiology
chemical_list: C569509:SAAL1 protein, human; C569510:SPACIA1 protein, mouse; D000685:Serum Amyloid A Protein