title: Effect of RNA Interference-Mediated Suppression of p75 on the Viability of Rat Notochordal Cells.
abstract: METHODS
  In vitrocell culture model.
  
  
  OBJECTIVE
  To investigate the effects of RNA interference (RNAi) on p75 expression and viability of rat notochordal cells treated with serum deprivation.
  
  
  BACKGROUND
  RNAi enables the inhibition of specific genes by sequence-specific gene silencing using a double-stranded RNA.
  
  
  METHODS
  Notochordal cells were isolated, cultured, and placed in 10% (control) or 0% (apoptosis-promoting) fetal bovine serum (FBS) for 48 hours. The expression of p75, apoptosis, and cell proliferation were determined. To suppress p75 expression, a small interfering RNA (siRNA) was synthesized against p75 (p75 siRNA) and transfected into cells. The suppression of p75 mRNA expression was investigated using the reverse transcription-polymerase chain reaction. The degree of p75 suppression was semiquantitatively analyzed using densitometry. The effect of p75 siRNA on apoptosis and proliferation of cells was determined. Solutions of an unrelated siRNA and transfection agent alone served as controls.
  
  
  RESULTS
  Serum deprivation significantly increased apoptosis by 40.3%, decreased proliferation of notochordal cells by 45.3% (both,p<0.001), and upregulated p75 expression. The p75 siRNA suppressed p75 expression in cells cultured in 0% FBS. The rate of suppression by p75 siRNA of p75 mRNA was 72.9% (p<0.001). Suppression of p75 expression by p75 siRNA inhibited apoptosis by 7% and increased proliferation by 14% in cells cultured in 0% FBS (both,p<0.05).
  
  
  CONCLUSIONS
  siRNA-mediated suppression of p75 inhibited apoptosis and increased proliferation of notochordal cells under conditions of serum deprivation, suggesting that RNAi might serve as a novel therapeutic approach for disc degeneration caused by insufficient viability of disc cells through the suppression of the expression of harmful genes.
authors.affiliation: Department of Orthopaedic Surgery, Uijeongbu St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Uijeongbu, Korea.
authors.forename: Jong-Beom
authors.initials: JB
authors.lastname: Park
authors.affiliation: Department of Orthopaedic Surgery, Sanggye Paik Hospital, Inje University College of Medicine, Seoul, Korea.
authors.forename: Dong-Gune
authors.initials: DG
authors.lastname: Chang
authors.affiliation: Department of Orthopaedic Surgery, Sanggye Paik Hospital, Inje University College of Medicine, Seoul, Korea.
authors.forename: Seung Yeol
authors.initials: SY
authors.lastname: Oh
authors.affiliation: Department of Orthopaedic Surgery, Uijeongbu St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Uijeongbu, Korea.
authors.forename: Eun-Young
authors.initials: EY
authors.lastname: Park
keywords: Notochordal cells; RNA interference; Viability; p75