ABSTRACT
Objective To analyze the differences of von Mises stress distribution in knee cartilage and meniscus in female with generalised joint hypermobility (GJH) and healthy female during drop jump landing. Methods The kinematic and ground reaction force (GRF) characteristics of knee joint in female with GJH and healthy female at the moment of peak vertical GRF (VGRF) during loading phase of drop jump landing were collected. The knee joint reaction force was calculated via inverse dynamics, and the combined force of knee joint along long axis of the femur was applied as the load. Based on three-dimensional (3D) finite element model of a female knee joint, numerical simulations were performed separately during drop jump landing of subjects in two groups, and von Mises stresses and stress distribution of knee cartilage and meniscus were calculated. Results At the moment of peak VGRF during drop jump landing, knee flexion and valgus angles in GJH group and control group showed a statistical significance (P<0. 05). Compared with control group, knee flexion angle decreased and valgus angle increased in GJH group. During drop jump landing, GJH group bore larger stress inside the knee joint, and stress distribution in weight-bearing areas of the medial and lateral tibiofemoral compartments was uneven, while the lateral femoral cartilage lateral condyle, the anterior and middle lateral of lateral tibial cartilage, the anterior angle and body lateral margin of lateral meniscus were stress concentration sites. Conclusions For females with GJH, the stability of knee joint decreases and force lines change in jumping events, due to the increased range of motion of knee joint and relaxation of joint capsule, which increases the risk of cartilage and meniscal injury in lateral knee joint. During jumping sports, females with GJH should especially prevent knee joint injury caused by altered force lines in frontal plane of knee joint.
ABSTRACT
<p><b>OBJECTIVE</b>To study the promoter methylation status of SFRP genes and the effect of 5- aza- 2'- deoxycytidine (5- Aza- CdR)induced apoptosis via Wnt/β- catenin pathway by demethylation in Jurkat cells.</p><p><b>METHODS</b>Jurkat cells were treated with different concentrations of 5- Aza- CdR. The cell proliferation level of Jurkat cells was detected by MTT assay. Apoptosis was evaluated by flow cytometry. Methylation- spcific PCR (MSP) was used to determine the methylation status of SFRP genes. The expressions of SFRP genes were detected by real time fluorescence quantitative PCR. The mRNA expression levels of survivin, c- myc and cyclin- D1 were analyzed by RT- PCR. Western blot was used to detect the levels of β-catenin protein.</p><p><b>RESULTS</b>Compared with control group, the different concentrations of 5-Aza-CdR could significantly inhibit the proliferation of Jurkat cells in a time-dose dependent manner (P<0.05). After being treated by 5- Aza- CdR for 48 hours, the cell early apoptosis rate in experiment group was significantly higher than that in control group (P<0.05). The promoters of SFRP1, SFRP2, SFRP4, SFRP5 genes were hypermethylation state in the control group, after being treated by 5-Aza-CdR for 72 hours, the brightness of SFRP1, SFRP2, SFRP4, SFRP5 genes' methylation strips weakened in a dose- dependent manner. SFRP mRNA expression increased (P<0.05) when 5- Aza- CdR concentration increased, and the level of β- catenin protein was dampened in a dose- dependent manner (P<0.05). As compared to the control group, the mRNA expressions of associated apoptosis genes survivin, c-myc and cyclin- D1, respectively were obviously down- regulated in a dose- dependent manner (P<0.05).</p><p><b>CONCLUSION</b>The effect of demethylation could up- regulate SFRP genes expressions by reversing its hypermethylation and induced apoptosis by down-regulation of β-catenin and associated apoptosis genes.</p>