| Objective: To observe expression changes of Nerve Growth Factor (NCF) and its receptor TrKA in callus of femoral fracture after brain and spinal cord injury in rats, and to investigate the influence and mechanism of Central Nervous System injury on fracture healing.Methods: A total of 48 healthy female adult Wistar rats were selected and randomly assigned to three groups: 16 with simple femoral fracture (control group), 16 with femoral fracture combined with brain injury (intervention group A) and 16 with femoral fracture combined spinal cord injury (intervention group B). Each group was divided into four small groups and observed on 1st day, 4th day, 7th day and 14th day after fracture. The animal model was set up by free fall weight drop. NCF and its receptor TrKA expression changes in callus tissue were tested at each fracture healing time point by immunohistochemical method.Results: 1. Expression of NCF:â‘ control group: The positive expression of NCF in fibroblast and osteoblast began on 1st day after fracture and increased as time progressed. â‘¡ Intervention group A: The callus formed slowly and there was no difference in positive expression of NCF in fibroblast and osteoblast of callus on 1st day, 4th day and 7th day compared with control group. The positive expression of NCF in fibroblast and osteoblast of callus increased significantly on 14th day after fracture (P<0.05). â‘¢ Intervention group B: There was no difference in the positive expression of NCF in fibroblast and osteoblast of callus on 1st day and 4th day after fracture between intervention group B and control group. A lot of fibrocallus and cartilage callus developed on 7th day, and the expression of NCF in fibroblast and osteoblast appeared strongly positive (P<0.01). 2. Expression of NCF receptor TrKA: It was almost consistent with the expression of NCF. According to immunohistochemical test results, NCF receptor TrKA in fibroblast and osteoblast of callus in control group was expressed positively. There was nodifference in positive expression rate of NCF receptor TrKA in fibroblast and osteoblast of calluson 1st day, 4th day and 7th day between intervention group A and control group. The expression ofNCF receptor TrKA increased on 14th day (PO.05). For intervention group B, the expression ofNCF receptor TrKA began to increase significantly on 4th day (P<0.05) and reached a peak from7th day to 14th day (PO.01).Conclusions: Femoral fracture heals faster when combined with brain and spinal cord injury. Itmay be associated with the expression up-regulation of NCF and its receptor TrKA in callus offracture sites.
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