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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.
RESUMO
Objective:To investigate the clinical treatment of large segmental humeral defects with unilateral external fixation and bone transport.Methods:A retrospective study was conducted of the 9 patients who had been treated at Department of Orthopedics, Shenzhen People's Hospital for large segmental humeral defects from September 2017 to June 2019. They were 5 males and 4 females with an average age of 29 years (from 21 to 41 years). Their defects were caused by trauma in 2 cases, by chronic osteomyelitis in 6 cases and by bone tumor in one case. The length of bone defect ranged from 4.2 to 9.0 cm, with an average of 5.9 cm. A unilateral external fixator was placed in operation, and adjusted regularly 7 to 10 days after operation for bone transport and bone lengthening to restore the length of humerus gradually. The external fixation bracket was removed after 3 to 4 layers of cortex were observed on X-ray films. Recorded were length and rate of humeral lengthening, fracture healing time, time for carrying external fixator and complications; the Disabilities of the Arm, Shoulder and Hand (DASH) scores were compared between preoperation and 15 months postoperation.Results:All the patients were followed up for 15 to 36 months (mean, 19 months). The length of lengthening averaged 5.9 cm (from 4.2 to 9.0 cm) with an average lengthening rate of 26%, the healing index 31 d/cm, the bone healing time 8.3 months, and the time for carrying external fixator 10.8 months(from 8.0 to 13.5 months). Their average DASH scores improved significantly from 25.0 ± 2.4 preoperation to 12.0 ± 1.8 at 15 months postoperation ( P<0.05). Good correction of large humeral defects was achieved in all but one case who reported temporary radial nerve paralysis. There were no such complications as neurovascular injury. The shoulder and elbow functions were basically normal after operation. Conclusions:In the treatment of large segmental humeral defects, unilateral external fixation plus bone transport can quickly repair the defects and recover the upper limb function of the patients.