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BACKGROUND:Heterotopic ossification of skeletal muscle is a clinically serious complication.For heterotopic ossification of skeletal muscles,the cells involved in the process of heterotopic ossification remain unclear. OBJECTIVE:To investigate the involvement of myocytes,fascia cells,and endothelial cells in the process of heterotopic ossification in skeletal muscle and to observe the cell origin of heterotopic ossification in skeletal muscle induced by bone morphogenetic protein 4. METHODS:Both C2C12 cells and the myotubes formed by the C2C12 cells in the induction medium were cultured,and 500 ng/mL bone morphogenetic protein 4 was added to the medium respectively,and whether the C2C12 cells and myotubes continued to proliferate within 10 days under the treatment were observed under a microscope.Myogenic cells(L6,derived from rats)and fibroblast-derived cells(derived from human)were co-cultured.After treatment with 500 ng/mL bone morphogenetic protein 4 and 10 ng/mL transforming growth factor-β,osteogenic and chondrogenic differentiation potential within 21 days were observed using Safranine O staining and Alcian blue staining.Using transgenic animal FVB/N-TgN(TIE2-LacZ)182Sato mice,15 μL of adeno-associated virus-bone morphogenetic protein 4(5×1010 PFU/mL)were implanted in the thigh muscle space of genetic mice for 10 and 14 days.X-gal staining was used to observe the formation of new blood vessel endothelium in the differentiated bone. RESULTS AND CONCLUSION:(1)Bone morphogenetic protein 4 caused myotube breakdown and increased C2C12 cell proliferation.Compared with other groups,the pure fibroblast-derived cell group had a higher area of positive alcian blue and safarin O staining(P<0.05)and a lower area of alkaline phosphatase staining(P<0.05),while the pure L6 group had a bigger area of alkaline phosphatase staining(P<0.05)but a smaller area of positive alcian blue and safarin O staining(P<0.05).(2)Transplantation of adeno-associated virus-bone morphogenetic protein 4-adsorbed gelatin sponge into FVB/N-TgN(TIE2-LacZ)182Sato mice resulted in heterotopic ossification.(3)X-gal staining results demonstrated that there was no obvious staining in chondrocytes and differentiated bones and Tie2+ endothelial cells did not participate in the formation of the alienated bone.(4)These findings verify that fibroblasts are the primary source of osteoblasts during the adeno-associated virus-bone morphogenetic protein 4-induced ectopic endochondral ossification in skeletal muscle,but myogenic cells are the main source of osteoblasts.Tie2+ endothelial cells might not be the cell source for cartilage and bone.
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Objective To investigate the effect of neuropeptide Y (NPY) on the osteoblastic differentiation of murine MC3T3-E1 cells and its mechanism related to the Wnt signaling pathway.Methods The murine MC3T3-E1 cells were divided into 4 groups according to the stimulators added:phosphate buffered saline (PBS) (control) and different concentrations of NPY (10-8 mol/L,10-10 mol/L and 10-12 mol/L).The cellular proliferation was detected with MTT assay after 1,3,5,7 and 9 days.The cells were identified with cell immunochemistry and Western Blot to find out the most effective concentration of NPY at different time points under osteoblastic condition.The cells were then divided into 4 groups:PBS,NPY,NPY + NPY receptor antagonist,and NPY + DKK1.Western blot was used to determine the expression of β3-catenin and p-GSK-3β in each group.Nuclear signaling activity of β3-catenin was observed using immunofluorescence staining.Results NPY significantly improved the proliferation of MC3T3-E1 cells at 7 and 9 days (P ＜0.05).NPY (10s mol/L and 10-10 mol/L) groups and NPY (10-10 mol/L and 10-12 mol/L) groups significantly improved the ALP activity at 4 and 14 days respectively (P ＜ 0.05).At 4 days,the expression of ALP protein was significantly decreased in the NPY + DKK1 group and the NPY + NPY receptor antagonist group compared with that in the NPY group (P ＜ 0.05).Although the expression levels of [β-catenin and p-GSK-3β protein were uninfluenced in either case,NPY significantly stimulated the nuclear signaling activity of β3-catenin.Conclusions NPY may significantly increase the expression of ALP protein in MC3T3-E1 ceils during osteoblastic differentiation.This effect might be mediated through the canonical Wnt signaling pathway.
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Objective To explore the clinical effects of variable angle locking plate ( VLP ) in the treatment of pediatric subtrochanteric femoral fractures. Methods Between January 2012 and November 2014, 9 pre-school children were treated at our department for subtrochanteric femoral fractures. They were 6 boys and 3 girls, with an average age of 4. 8 years ( from 4 to 6 years ) . By the Seinsheimer classification, 5 cases were of typeⅡB and 2 of typeⅡC and 2 of typeⅢA. The intervals between injury and surgery averaged 3 days ( from 2 to 5 days ) . All of them were treated with open reduction and VLP internal fixation. Results All the wounds healed well without any infection. All the stitches were removed within 12 days. They were followed up for 8 to 26 months ( average, 16 months ) . All the fractures united within 3 months after operation. Follow-ups revealed no plate or screw loosening, or refracture at the same site. According to the Beaty imaging criteria, the early outcomes were all satisfactory. At the final follow-ups, all the children gained normal gait after full-weight rehabilitation. The affected and normal hips are nearly identical in range of motion and muscle strength. All the children recovered their pre-injury status. By the Sanders scoring for function of the affected hip, 7 cases were rated as excellent and 2 as good. Conclusion VLP can be an effective option for treatment of subtrochanteric femoral fractures in preschool children patients.