Attenuation of fibrosis in vitro and in vivo with SPARC siRNA
1 State Key Laboratory of Genetic Engineering and MOE Key Laboratory of Contemporary Anthropology, School of Life Sciences, Fudan University, 220 Handan Road, Shanghai 200433, PR China
2 Division of Rheumatology and Clinical Immunogenetics, Department of Internal Medicine, The University of Texas Medical School at Houston, 6431 Fannin St, Houston, Texas 77030, USA
3 Department of Pathology, Baylor College of Medicine, One Baylor plaza, Houston, Texas 77030, USA
4 Department of Molecular Genetics, MD. Anderson Cancer Center, University of Texas, 1515 Holcombe Blvd, Houston, Texas 77030, USA
Arthritis Research & Therapy 2010, 12:R60 doi:10.1186/ar2973Published: 1 April 2010
SPARC is a matricellular protein, which, along with other extracellular matrix components including collagens, is commonly over-expressed in fibrotic diseases. The purpose of this study was to examine whether inhibition of SPARC can regulate collagen expression in vitro and in vivo, and subsequently attenuate fibrotic stimulation by bleomycin in mouse skin and lungs.
In in vitro studies, skin fibroblasts obtained from a Tgfbr1 knock-in mouse (TBR1CA; Cre-ER) were transfected with SPARC siRNA. Gene and protein expressions of the Col1a2 and the Ctgf were examined by real-time RT-PCR and Western blotting, respectively. In in vivo studies, C57BL/6 mice were induced for skin and lung fibrosis by bleomycin and followed by SPARC siRNA treatment through subcutaneous injection and intratracheal instillation, respectively. The pathological changes of skin and lungs were assessed by hematoxylin and eosin and Masson's trichrome stains. The expression changes of collagen in the tissues were assessed by real-time RT-PCR and non-crosslinked fibrillar collagen content assays.
SPARC siRNA significantly reduced gene and protein expression of collagen type 1 in fibroblasts obtained from the TBR1CA; Cre-ER mouse that was induced for constitutively active TGF-β receptor I. Skin and lung fibrosis induced by bleomycin was markedly reduced by treatment with SPARC siRNA. The anti-fibrotic effect of SPARC siRNA in vivo was accompanied by an inhibition of Ctgf expression in these same tissues.
Specific inhibition of SPARC effectively reduced fibrotic changes in vitro and in vivo. SPARC inhibition may represent a potential therapeutic approach to fibrotic diseases.