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  • Open Access

SPACIA1/SAAL1: a newly identified gene associated with aberrant proliferation of synovial fibroblasts

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Arthritis Research & Therapy201214 (Suppl 1) :P61

  • Published:


  • Arthritis
  • Cell Cycle Progression
  • Synovial Fibroblast
  • Inhibit Tumor Necrosis Factor
  • Cartilage Destruction


The bone and cartilage destruction seen inrheumatoid arthritis (RA) is caused by synovial pannus formation, which is characterized by aberrant proliferation of synovial fibroblasts. Inhibition of synovial proliferation has recently been reported to be a promising therapeutic strategy for RA.However, the specific mechanism underlyingdysregulated proliferation of synovial fibroblasts remains unclear.


We aimed toidentify and characterize genesthat are involved in the aberrant proliferation of synovial fibroblasts.


Microarray analysiswas performed to identifythe genes that had upregulated expression inmice with collagen-induced arthritis (CIA). The effect of candidate genes on the proliferation of synovial fibroblasts was screened using antisense oligodeoxynucleotides and small interfering RNAs (siRNAs).


We identified a novel gene named SPACIA1/SAAL1 (synoviocyte proliferation-associated in CIA 1/serum amyloid A-like 1)that was associated with aberrant proliferation of synovial fibroblasts. Immunohistochemicalanalysis indicated that SPACIA1/SAAL1 was strongly expressed in the foot joints of mice with CIA and in the thickened synovial lining of the human RA synovium. Transfection of siRNA targeting SPACIA1/SAAL1 into RA synovial fibroblastscould inhibit tumor necrosis factor (TNF)α-induced proliferation more effectively thanit could inhibit serum-induced proliferation.In addition,the antiproliferative effect of SPACIA1/SAAL1 siRNA was caused byinhibition of cell cycle progression and not by induction of apoptosis.We established transgenic (Tg) mice that overexpressed SPACIA1/SAAL1. These Tg mice did not spontaneously develop arthritis or cancer. However,inducing CIA causedgreatersynovial proliferation and worse diseasein Tg mice thanin wild-type mice.


SPACIA1/SAAL1 plays an important role in the aberrant proliferation of synovial fibroblasts under inflammatory conditions.

Authors’ Affiliations

St. Marianna University School of Medicine, Kawasaki, Japan
Santen Pharmaceutical Co., Ltd., Osaka, Japan
Institute of Medical Science, Tokyo Medical University, Tokyo, Japan
Misato Marine Hospital, Kochi, Japan


© Sato et al.; licensee BioMed Central Ltd. 2012

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.