Objective:To investigate the effects of 5-aza-2′deoxycytidine(5-aza-dC),a DNA methyltransferase (DNMT)inhibitor, on the methylation status of the RECK gene and the invasion of salivary adenoid cystic carcinoma cell lines.Methods:Methylation-specific PCR,Western blot analysis and quantitative real-time PCR were used to investigate the methylation status of RECK gene and the expression of RECK mRNA and protein in SACC cell lines.The invasive ability of SACC cells was examined by transwell assay. Results:Promoter methylation was only found in ACC-Mcell line and not in ACC-2 cell line.Treatment of ACC-Mcells with 5-aza-dC partially reversed the hypermethylation status of the RECK gene and significantly enhanced the expression level of mRNA and pro-tein of RECK,suppressed ACC-Mcell invasive ability.Conclusion:5-aza-dC can inhibit ACC-Mcell invasion by reversal of hyperm-ethylation status of RECK gene.

Objective:To investigate the impact of peak pressure upon different bone densities during autonomous puncture by orthopedic robot on puncture path deviation and bone cement leakage.Methods:A spinal surgery robot system was designed for autonomous vertebral puncture and bone cement injection, and six porcine spine specimens were used for single-segment or double-segment simulated percutaneous vertebral augmentation surgery. The accuracy of puncture path (Gertzbein-Robbins grading), bone cement leakage classification, and peak bone drill pressure were measured to assess the accuracy of autonomous vertebral puncture and bone cement leakage in vertebral cortical and cancellous bone of different densities.Results:A total of 64 porcine vertebrae were simulated for puncture, among which 53 vertebrae were classified as Grade A, 8 as Grade B, and 3 as Grade C according to the Gertzbein-Robbins grading. The cortical bone pressure of Grade A vertebrae was 6.663±0.319 N which was lower than that of Grade B (8.348±0.418 N) and Grade C (11.500±0.600 N), with significant differences ( F=341.000, P<0.001). The cancellous bone pressure of Grade A, B, and C vertebrae were 3.660±0.317, 3.594±0.608, and 4.117±0.257 N, respectively, with no significant difference ( F=2.496, P=0.091). There were 40 cases of no leakage, 20 cases of Type I leakage (leakage into the surrounding vertebrae), and 3 cases of Type II leakage (leakage into the vertebral canal), with an overall leakage rate of 36% (23/64). The peak cortical bone pressure for no leakage, Type I, and Type II leakage was 6.638±0.301, 6.792±0.404, and 6.753±0.473 N, respectively, and the peak cancellous bone pressure was 3.634±0.279, 3.783±0.423, and 3.920±0.255 N, respectively, with no significant difference ( F=1.521, P=0.227; F=2.106, P=0.131). Conclusion:During the autonomous puncture process of the novel orthopedic robot, the accuracy of autonomous puncture path decreased when the puncture pressure through the cortical bone was high, and the probability of invading the pedicle increased. The puncture pressure of cortical and cancellous bone had no significant effect on the occurrence rate of bone cement leakage.