The Expression Of Neurotrophin-3 In Callus During Fracture Healing In Brain Injury Associated With Fracture

Objective:This study set up traumatic brain injury associated with bone fracture rat model and bone fracture rat model. X-ray examination and HE staining were applied verified to verify the phenomenon of traumatic brain injury accelerate bone healing. While immunoh-istochemical staining was applied to detect the expression of NT-3 and TrkC in osteotylus of rats. We also wish this study could contribute to the new strategy for curing bone fracture.Methods:Fifty-six clean-type adult Sprague-Dawley (SD) rats (250-300g) were randomly divided into two groups:(1)fracture group(F n=28),(2) traumatic brain injury associated with fracture group (TBI+F n=28). Simple tibial fracture model was set up by cut off tibial with a wire saw.In second group we cut off tibial with a wire saw and make moderate traumatic brain injury.S-D rats were killed respectively on 1st,2nd,3rd,4th week after operation and intercepted callus specimens about 5mm from the upper and lower fracture.After HE staining and immuno-histochemical staining to detect the expression of NT-3 and TrkC.The animals were killed in 3rd and 4th week after examination. Analyse all dates statistically.Results:1.Gross anatomical observation:TBI+F group has more bony callus than F group.2.X-ray findings:BF group has more bony callus than F group in 3rd week,and its fracture line is more ambiguous in 3rd week.BF group was better than F group in fracture remodeling in 4th week,and fracture line almost disppeared in 4th week.3.HE staining:F Group:HE staining showed the typical fracture healing, During the first week after injury, fibroblasts grew into fracture site and formated granulation tissue connection.During the second week after injury,granulation tissue continued to grow,and fibrous callus and cartilage callus became emergency.During the third week after injury,a small amount of callus trabeculae became to grow.During the forth week,there were small cartilage islands and more mature trabecular bone.TBI+F Group:During the first week after injury,a large number of granulation tissue connection grew into fracture site and formated fiber formation of callus.During the second week after injury,Seen a large number of cartilage cells, cartilage islands, new bone trabecular were seen. During the third week,there were a large number of fibrous callus^ cartilage callus and woven bone. At the forth weeks the number of woven bone and mature trabecular ncreased.There was only a few scattered hypertrophic chondrocytes.4.1mmunohistochemical staining:expression of NT-3:①F group:NT-3 expression is detected in osteoblast, chondrocyte and fibroblast in bony callus, and the number of positive cells was small;TBI+F group:The expression of NT-3 in osteoblast, chondrocyte and fibroblast was increased during the first week after surgery, and achieved peak during the second week,then decreased in 3rd and 4th week.②There is significant difference of the expression of NT-3 in osteoblast, chondrocyte and fibroblast between TBI+F group and F group during the first and second week. However, the expression of NT-3 in osteoblast, chondrocyte and fibroblast decrease during the third and fourth week with time, and the difference between TBI+F group and F group disappeared.expression of Trk-C:①F gup:Trk-C expression is detected in osteoblast, chondrocyte and fibroblast in bony callus, and the number of positive cells is small;TBI+F group:The expression of Trk-C in osteoblast, chondrocyte and fibroblast was increased during the first week after surgery,and achieved peak during the second week,then decreased in 3rd and 4th week.②There is significant difference of the expression of Trk-C in osteoblast, chondrocyte and fibroblast between TBI+F group and F group during the first and second week. However, the expression of NT-3 in osteoblast, chondrocyte and fibroblast decrease during the third and fourth week with time, and the difference between TBI+F group and F group disappeared. Conclusion:Tibial fracture heals faster when combined with brain injury.It may be associated with the expression up-regulation of NT-3 and its receptor TrkC in callus of fracture sites.