Small interfering RNA inhibition of SPARC attenuates the profibrotic effect of transforming growth factor beta1 in cultured normal human fibroblasts.
OBJECTIVE
SPARC (secreted protein, acidic and rich in cysteine), or osteonectin, is a matricellular protein. Recently, it was observed to be overexpressed in fibroblasts obtained from the skin of patients with scleroderma, as well as in different tissues from patients with several other fibrotic disorders. Moreover, a genetic polymorphism in SPARC has been associated with susceptibility to scleroderma. Transforming growth factor beta1 (TGFbeta1) is a profibrotic cytokine that stimulates excessive collagen production in patients with scleroderma or other fibrotic diseases. The purpose of this study was to examine whether specific inhibition of SPARC can influence the expression of type I collagen and ameliorate the profibrotic activity of TGFbeta1 on normal human fibroblasts.


METHODS
Fibroblasts obtained from the skin of 4 healthy individuals were cultured and transfected with SPARC small interfering RNA (siRNA). TGFbeta was used as a fibrosis stimulus in cultured fibroblasts. Real-time quantitative reverse transcriptase-polymerase chain reaction and Western blotting were used to measure transcription and protein levels of SPARC and type I collagen, respectively.


RESULTS
The fibroblasts transfected with SPARC siRNA showed decreased expression of both SPARC and type I collagen. Exogenous TGFbeta1 induced increased expression of both SPARC and type I collagen in cultured normal human fibroblasts, but this response was significantly blunted in the fibroblasts transfected with SPARC siRNA.


CONCLUSIONS
TGFbeta1 can induce increased expression of both SPARC and type I collagen. Specific inhibition of SPARC led to decreased expression of type I collagen and attenuated the profibrotic effect of TGFbeta1 in cultured normal human fibroblasts. Use of siRNA to silence SPARC represents a potential therapeutic approach to fibrotic disorders such as scleroderma.
Zhou
Xiaodong
X
Division of Rheumatology and Clinical Immunogenetics, Department of Internal Medicine, University of Texas-Houston Health Science Center, 6431 Fannin, Houston, TX 77030, USA. Xiaodong.Zhou@uth.tmc.edu
Tan
Filemon K
FK
Guo
Xinjian
X
Wallis
Debra
D
Milewicz
Dianna M
DM
Xue
Sarah
S
Arnett
Frank C
FC
D002478:Cells, Cultured; D024042:Collagen Type I / Q000037:antagonists & inhibitors; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology; D005355:Fibrosis; D006801:Humans; D015676:Osteonectin / Q000037:antagonists & inhibitors* / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology*; D012867:Skin; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1
D024042:Collagen Type I; D015676:Osteonectin; D034741:RNA, Small Interfering; C508960:TGFB1 protein, human; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1