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.

Surgical Usage of a Cortical Bone Trajectory Pedicle Screw to Treat Lumbar Pyogenic Spondylodiscitis: Preliminary Report

STUDY DESIGN: Retrospective clinical study. OBJECTIVES: To assess the efficacy of a cortical bone trajectory pedicle screw (CBT-PS) for the treatment of lumbar pyogenic spondylodiscitis. SUMMARY OF LITERATURE REVIEW: Pedicle screws were used for surgical treatment of pyogenic spondylodiscitis to prevent instability and deformity. CTB-PS are typically inserted from the inferomedial to superolateral direction of the pedicle and have yielded satisfactory results in degenerative or osteoporotic spinal disorders. MATERIALS AND METHODS: Eight patients with single segment lumbar pyogenic spondylodiscitis were analyzed. At first, anterior debridements and interbody fusions were perfomed with autogenous strut bone grafts, followed by posterior fixations and fusions with CBT-PS. The lordotic angles of operated levels were checked at the preoperative, postoperative, and final follow-ups. Visual analogue scales (VAS) were checked at the preoperative and final follow-ups. RESULTS: Lesion sites were found at four L3-4, three L4-5, and one L2-3. Follow-ups were held at 26.13±8.23 months. The lordotic angles at preoperative, postoperative, and final follow-ups were 12.13±3.09°, 14.63±3.16°, and 12.75±3.99°, retrospectively. There were significant differences between results from the preoperative-postoperative and postoperative-final follow ups. There was no difference in the preoperative-final follow up. There was a significant difference between the VAS at the preoperative and final follow-ups (8.13±0.83 and 2.38±0.92, retrospectively). Complete bony unions of were observed at the final follow-up in all cases. CONCLUSIONS: The advantages of using a CBT-PS for lumbar pyogenic spondylodiscitis included the ability to minimize damage from the screw for both the posterior structure damage and the operated anterior area to prevent instability and deformity, and to achieve rigid bone union. CBT-PS is a potential surgical option for pyogenic spondylodiscitis.