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SPARC, an upstream regulator of connective tissue growth factor in response to transforming growth factor beta

X D Zhou1, M M Xiong, F K Tan

  • 1University of Texas-Houston Health Science Center, TX 77030, USA. xiaodong.zhou@uth.tmc.edu

Arthritis and Rheumatism
|November 30, 2006
PubMed
Abstract

Insights

Secreted protein, acidic and rich in cysteine (SPARC) has a greater regulatory effect on extracellular matrix genes than connective tissue growth factor (CTGF) in human fibroblasts. SPARC positively regulates CTGF, while CTGF may negatively feedback on SPARC.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Extracellular matrix (ECM) production is regulated by complex signaling pathways.
  • Secreted protein, acidic and rich in cysteine (SPARC) and connective tissue growth factor (CTGF) are key regulators of ECM remodeling.
  • Understanding the interplay between SPARC and CTGF is crucial for comprehending fibroblast function in tissue homeostasis and disease.

Purpose of the Study:

  • To compare the inhibitory effects of SPARC and CTGF small interfering RNA (siRNA) on human fibroblast gene expression.
  • To elucidate the interrelationship between SPARC and CTGF in regulating ECM components.

Main Methods:

  • Human fibroblasts were transfected with siRNA targeting SPARC or CTGF.
  • Cells were stimulated with transforming growth factor beta1 (TGFβ1) +/- siRNA.
  • Gene expression levels of ECM components were quantified using real-time quantitative reverse transcription-polymerase chain reaction (RT-qPCR).
  • Genetic network modeling was employed to analyze regulatory relationships.

Main Results:

  • Both SPARC and CTGF inhibition protected against collagen gene overexpression following TGFβ1 stimulation.
  • SPARC inhibition led to a greater reduction in collagen gene expression compared to CTGF inhibition.
  • SPARC positively regulated CTGF, COL1A2, COL3A1, COL11A1, and TIMP3 expression.
  • CTGF showed a weaker positive regulatory effect on these genes and a minor negative effect on SPARC.

Conclusions:

  • SPARC exerts a more significant regulatory influence on major ECM structural components than CTGF in cultured human fibroblasts.
  • SPARC predominantly positively regulates CTGF.
  • CTGF may function as a negative feedback regulator of SPARC activity post-TGFβ stimulation.

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