Small Interfering RNA–Mediated Suppression of Fas Modulate Apoptosis and Proliferation in Rat Intervertebral Disc Cells

STUDY DESIGN: In vitro cell culture model. PURPOSE: To investigate the effect of small interfering RNA (siRNA) on Fas expression, apoptosis, and proliferation in serum-deprived rat disc cells. OVERVIEW OF LITERATURE: Synthetic siRNA can trigger an RNA interference (RNAi) response in mammalian cells and precipitate the inhibition of specific gene expression. However, the potential utility of siRNA technology in downregulation of specific genes associated with disc cell apoptosis remains unclear. METHODS: Rat disc cells were isolated and cultured in the presence of either 10% fetal bovine serum (FBS) (normal control) or 0% FBS (serum deprivation to induce apoptosis) for 48 hours. Fas expression, apoptosis, and proliferation were determined. Additionally, siRNA oligonucleotides against Fas (Fas siRNA) were transfected into rat disc cells to suppress Fas expression. Changes in Fas expression were assessed by reverse transcription-polymerase chain reaction and semiquantitatively analyzed using densitometry. The effect of Fas siRNA on apoptosis and proliferation of rat disc cells were also determined. Negative siRNA and transfection agent alone (Mock) were used as controls. RESULTS: Serum deprivation increased apoptosis by 40.3% (p<0.001), decreased proliferation by 45.3% (p<0.001), and upregulated Fas expression. Additionally, Fas siRNA suppressed Fas expression in serum-deprived cultures, with 68.5% reduction at the mRNA level compared to the control cultures (p<0.001). Finally, Fas siRNA–mediated suppression of Fas expression significantly inhibited apoptosis by 9.3% and increased proliferation by 21% in serum-deprived cultures (p<0.05 for both). CONCLUSIONS: The observed dual positive effect of Fas siRNA might be a powerful therapeutic approach for disc degeneration by suppression of harmful gene expression.

Effects of Different Magnitudes of Mechanical Stretch on Human Intervertebral Disc Cells / 天津医药

Objective To investigate the effects of different magnitudes of mechanical stress on human interverte-bral disc degeneration. Methods The human intervertebral disc cells were subjected to different magnitudes of mechanical stress (0, 6%, 12%, or 18%elongation) for 24 h using a Flexercell Strain Unit. The mRNA expressions of anabolic genes (col-lagen-1A1, collagen-2A1, aggrecan and versican) and catabolic genes (MMP-3, MMP-13, ADAMTS-4 and ADAMTS-5) were examined by real-time PCR and Western blot methods. Results The expression levels of collagen-1A1 and collagen-2A1 were increased at 12%of mechanical stress, and collagen-2A1 was decreased at 18%of mechanical stress compared with those of control. The mRNA expressions of catabolic genes, MMP-13 and ADAMTS-5, were increased at 12%and 18%of mechanical stress than those of control. The mechanical stretch induced a magnitude-dependent increase in ADAMTS-4 synthesis, which was finely tuned by stretching-triggered activation of distinct mitogen-activated protein kinase cascades. Specifically, an ERK1/2 specific inhibitor, U0126, significantly inhibited the stretching-induced ADAMTS-4 expression, whereas the inhibitors of p38 and JNK, SP6000125 and SB203580, showed only slightly effect on the stretching-induced ADAMTS-4 expression. Conclusion The different magnitudes of mechanical stretch exhibited different effects on the bio-logical behavior of intervertebral disc cells, which profoundly affects the intervertebral disc degeneration.

High Glucose Accelerates Autophagy in Adult Rat Intervertebral Disc Cells

STUDY DESIGN: In vitro cell culture. PURPOSE: The purpose of this study was to investigate the effect of high glucose on autophagy in adult rat intervertebral disc cells. OVERVIEW OF LITERATURE: Diabetes mellitus is considered to be an important etiologic factor for intervertebral disc degeneration, resulting in degenerative disc diseases. A glucose-mediated increase of autophagy is a major causative factor for the development of diseases associated with diabetes mellitus. However, no information is available for the effect of high glucose on autophagy in adult intervertebral disc cells. METHODS: Nucleus pulposus and annulus fibrosus cells were isolated from 24-week-old adult rats, cultured and placed in either 10% fetal bovine serum (normal control) or 10% fetal bovine serum plus two different high glucose concentrations (0.1 M and 0.2 M) (experimental conditions) for one and three days, respectively. The expressions of autophagy markers, such as beclin-1, light chain 3-I (LC3-I) and LC3-II, autophagy-related gene (Atg) 3, 5, 7 and 12, were identified and quantified. RESULTS: Two high glucoses significantly increased the expressions of beclin-1, LC3-II, Atg3, 5, 7, and 12 in adult rat nucleus pulposus and annulus fibrosus cells in a dose- and time-dependent manner. The ratio of LC3-II/LC3-I expression was also increased in a dose-respectively time-dependent manner. CONCLUSIONS: The results suggest that autophagy of adult nucleus pulposus and annulus fibrosus cells might be a potential mechanism for the intervertebral disc degeneration in adult patients with diabetes mellitus. Thus, the prevention of autophagy in adult intervertebral disc cells might be considered as a novel therapeutic target to prevent or to delay the intervertebral disc degeneration in adult patients with diabetes mellitus.