| Objective :1.To design knee prostheses for rabbits, and study the concentration of Staphylococcus aureus 25923 to cause the Prosthetic-joint modal infection.2. To study the effect of additional cathelicidin antimicrobial peptide PR-39 in Prosthetic-Joint Infections,and turnover of BMSCs in vivo.Methods:1. Thirty-six rabbits were divided into 3 groups randomly,12 animals in each group.and all of the animal were implanted the 3mm Kirschner wire for the length of 15mm as the prosthesis into stem to the distal femoral through intercondylar fossa. Immediately after the surgery,0.5ml 1×107 CFU of Staphylococcus aureus ATCC25923 was injected into the joints of group A, 0.5ml 1×106 CFU in group B and 0.5ml 1×105 CFU in group C. the animals were sacrificed 2 weeks after injections, and wounds situation were observed and X-ray films were taken. levels of serum CRP and ESR were determined, pathological changes were observed and bacteria cultures was performed.2. To study the effect of additional cathelicidin antimicrobial peptide PR-39 in Prosthetic-Joint Infections,and turnover of BMSCs in vivo.2.1.Twenty-four rabbits were divided into 2 groups randomly,12 animals in each group.and all of the animal were implanted the 3mm Kirschner wire for the length of 15mm as the prosthesis into stem to the distal femoral through intercondylar fossa. Immediately after the surgery. 0.5ml 1×108 /ml the BMSc infected pLV/PR-39 was planted into the joints of experimental group, 0.5ml 1×108 /ml the BMSc only carried GFP gene was planted into the joints of control group. 0.5ml 1×106 CFU of Staphylococcus aureus ATCC25923 was injected into the joints in each group,when close the wound. The animals were sacrificed 2 weeks after injectio ns, and wounds were observed and X-ray films were taken. levels of serum temperature,PMN, CRP and ESR were determined ,pathological changes were observed and viable total count was performed in 7 and 14 day later of operations; The push-out test was used to m easure the impant-bone in tegrate strength 14 day later of operations.2.2 Six rabbits were injected 2×105 BMSCs infected with lentivirus vector two tibia periosteum. Four weeks later, lump was observed on the tibia. It was analyzed with histopathological detection.Results:1.After staphylococcus aureus was injected into the joints right after the surgery for 14 day. (1)One animal died in group A,all of others were survival;but the fuction of the knees were better in group B and C.(2)100% knee joint infection in group A and100% in group B, 83.3% in group C .(3) A great amount of inflammatory cells infiltration were found in the infected samples,(4)CRP and ESR kept a high level(P﹤0.05),(5) In the infected samples, a great amount of osteoporosis were found around of the implant and the periphery of the implant were vague.2. To study the effect of additional cathelicidin antimicrobial peptide PR-39 in Prosthetic-Joint Infections,and turnover of BMSCs in vivo.2.1 Fourteen days later ;(1) The wound were much better in experimental group and the fuction of the knees were better too, the temperation of all animal were elevated after the operation but more obviously in control group(P﹤0.05).(2) The levels of serum PMN, CRP and ESR were elevated after the operation(P﹤0.05), but more obviously in control group(P﹤0.05).(3) A great amount of inflammatory cells infiltration were found in each sample, through the microscopic organization.(4) The animal in experimental group, the periphery of the implant were distinct in the X-ray films,and The bone density of femoral metaphysis enhance enhanced.(5) Bacteria were far less in of per gram organization of experimental group(P﹤0.01)in 7 day and 14 day later operation , especially at 14 day(P<0.0001)。2.2 A great amount of bone trabecula were found in the tissue ,which from tibial tubercle 4 week later, and this tissue appearance fluorescence under fluorescence microscopeConclusion:1.An animal model of TKA infection can be established successfully 2 weeks by 1×106 CFU staphylococcus aureus 25923 injecting into the joints immediately after the surgery.2.Targeted gene transfer of a cathelicidin antimicrobial peptide PR-39 confers could resistance against infection in orthopedic and suggested the divergence in the evolution of management for Prosthetic-Joint Infections.3.The BMSc could differentiate to bone issue, it may be to reduce prosthesis loosening caused by postoperative infection.
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