BACKGROUND:Orthopedists should pay more attentions to nonunion prevention in view of nonunion treatment, that is, active interventions should be taken to avoid bone delayed union and nonunion. OBJECTIVE:To explore the effect of composite tissue-engineered scaffold constructed by nano-hydroxyapatite/polyamide 66 (nHA/PA 66) combined with bone marrow mesenchymal stem cels to repair a femoral fracture with severe nonunion. METHODS:Rat bone marrow mesenchymal stem cels were isolated and culturedin vitro, and then they were divided into three groups: bone marrow mesenchymal stem cels without osteogenic induction, with osteogenic induction or combined with nHA/PA 66 folowed by osteogenic induction as control group, test group or composite group, respectively. Then osteogenic differentiation of bone marrow mesenchymal stem celsin vitrowas analyzed by measuring alkaline phosphatase activity and alizarin red staining, cel adhesion on the nHA/PA 66 was observed using scanning electron microscopy, and the celgrowth and proliferation were detected by MTT assay. In the meanwhile, established Sprague-Dawley rat femur nonunion models were randomly divided into three groups: the areas of nonunion were implanted with nothing as blank control group,those were with nHA/PA 66 as simple scaffold group, and the others were with nHA/PA 66 combined with bone marrow mesenchymal stem cels as composite scaffold group. Afterwards, X-ray examination, micro-CT and Masson staining were used to evaluate the femoral healing. RESULTS AND CONCLUSION:At 6 and 12 days after osteogenic induction, alkaline phosphatase activity in the test group was significantly higher than that in the control group; at 14 days, compared with the control group, the amount of mineralized nodules in the test group was significantly higher, which indicated that bone marrow mesenchymal stem cels after osteogenic induction could differentiate into osteoblasts. Attached cels spread wel on the scaffold with good proliferation activity, suggesting that nHA/PA 66 is suitable for cel adherence, proliferation and osteogenic differentiation. Besides, at 12 weeks after modeling, in the blank control group, no calus appeared in the nonunion region. In the simple scaffold group, the broken femur did not heal at 8 and 12 weeks after surgery. In the composite scaffold group, the broken femur did not heal at 8 weeks, but a lot of calus appeared; at 12 weeks, bone healing achieved and the scaffold was encased and absorbed.These findings demonstrate that the tissue-engineered bone scaffolds constructed by bone marrow mesenchymal stem cels and nHA/PA 66 effectively prevent bone nonunion by accelerating femoral healing in a rat femur nonunion model.