Objective To study the paracrine effect of hypoxic preconditioned umbilical cord mesenchymal stem cells (UCMSCs) on the proliferation,migration and osteogenic differentiation of osteoblasts.Methods UCMSCs were cultured under hypoxia and normal oxygen condition before two UCMSCs conditioned media were obtained.After that,MG-63 cells were cultured in three groups:hypoxia conditioned medium group,normoxia conditioned medium group and DMEM control group.The proliferation of MG-63 cells was detected by mosmann tetrazoline colorimetry( MTT) method after 1,3 and 5 days.The migratory ability of MG-63 cells was detected by scratch assay .After 21 days′culture , the formation of osteogenic calcium nodules was detected by Alizarin red staining.ELISA method was used to detect the content of vascular endothelial growth factor ( VEGF) in hypoxia and normoxia conditioned medium.Results The MTT test showed that the proliferation ability of MG-63 cells in hypoxia conditioned medium group and normoxia conditioned medium group was greater than in the DMEM control group.The difference was statistically significant ( P <0.05).Furthermore, the proliferation ability of cells in hypoxia conditioned medium group were much greater than cells in normoxia culture medium group.The difference was statistically significant (P<0.05).Scrath assay showed that the migratory ability of MG-63 cells in hypoxia conditioned medium group and normoxia conditioned medium group was greater than cells in DMEM control group,and cells in hypoxia conditioned medium group was much greater than cells in normoxia conditioned medium group. After 21 days′culture,we found that the number of calcium nodules was the largest in hypoxia conditioned medium group, followed by normoxia conditioned medium group and DMEM control group.ELISA showed that the content of VEGF in hypoxia conditioned medium was higher than that in normoxia conditioned medium and the difference was statistically significant (P<0.01).Conclusion The paracrine function of UCMSCs can be enhanced by hypoxia,thus improving the proliferation,migration and osteogenic differentiation of osteoblasts.

Objective: To compare the clinical effects between minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) assisted by Microendoscopic discectomy (MED) and Quadrant for the treatment of degenerative lumbar spinal stenosis (DLSS). Methods: All of 59 patients suffered from DLSS treated surgically from May 2015 to October 2017 were reviewed. According to the surgery method, all cases were divided into MED group (27 cases) and Quadrant channel group (32 cases). All patients were followed up for an average of 18.5 months (11-29 months). Comparison was made on the operative time, intraoperative blood loss, postoperative drainage, postoperative time in bed, postoperative creatine kinase (CK), fusion rate and the degree of muscle fibrosis shown in MRI, as well as visual analogue scale (VAS)score and Oswestry dysfunction index (ODI) score in two groups. Results: The duration of operation in MED group was significantly longer than that in Quadrant group (161.7±22.4 min vs. 145.6±19.4 min, t=4.541, P<0. 01), but less intraoperative blood loss (138.1±26.9 ml vs. 155.6±21.5 ml, t=-2.724, P< 0. 01) and shorter time in bed after surgery (2.3±0.7 d vs. 3.5±1.1 d, t=-4.564, P<0.01). Compared with Quadrant group, CK levels were risen slightly on the first and third postoperative day (P<0.01). CK on the fifth postoperative day in both groups returned to normal. VAS score of lower back pain in MED group was lower than that in Quadrant group on the third day and twelfth month after operation (P<0.05). After 3 months, there was no significant difference in VAS score and ODI between the two groups (P>0.05). ODI was lower in MED group than that in Quadrant group after 6 months and 12 months.The fusion rate was88.9%(24/27) in MED group and 93.8%(30/32) in Quadrant channel group. There was no statistical difference in fusion rate of two groups. 10 patients in MED group and 12 patients in Quadrant group underwent MRI examination of lumbar spine one year after operation. The ratio of postoperative and preoperative atrophy of multiplex muscle area was measured. Muscle atrophy of lower back muscle was lighter in MED group (0.12±0.05 vs. 0.22±0.04, t=-2.428, P<0.05). For intraoperative and postoperative complications, 1 case of dural sac rupture occurred in both groups. Gelatin sponge immediately with fibrin glue was used for plugging up, no postoperative cerebrospinal fluid leakage was found. In Quadrant channel group, 1 case had less blood supply of skin incision edges and epidermal necrosis while the other case had fat liquefaction. Conclusion Compared with the aid of Quadrant, MIS-TLIF assisted with MED had less blood loss, less trauma and faster recovery and could reduce the incidence of postoperative incision complication.