脑外伤后血小板衍生生长因子及血管内皮生长因子对骨折愈合影响的实验研究

Study on the Effects of Platelet-derived Growth Factor (PDGF) and Vascular Endothelial Growth Factor(VEGF)

目的观察比较SD大鼠在骨折合并脑外伤以及在单纯骨折时,骨折愈合过程中骨痂内血小板衍生生长因子(platelet-derived growth factor,PDGF)及血管内皮细胞生长因子(vascular endothelial growth factor,VEGF)表达的变化;探讨VEGF和PDGF在大鼠骨折合并脑外伤后的加速骨折愈合中的作用机制,以期为临床治疗难治性骨折提供理论依据。方法将204只大鼠分为4组∶A组(正常对照组)、B组(脑外伤组)、C组(骨折组)和D组(骨折合并脑外伤组),其中A组12只,B组56只、C、D组各68只。建立大鼠脑外伤和骨折模型。术后分别于1 d、4 d、1周、2周、3周、4周和5周将B组、C组及D组大鼠各处死8只,在距离骨折断端大约1 cm处截取骨痂标本,进行免疫组化染色。4周、5周时C组和D组处死的大鼠需进行X线摄片。C组和D组大鼠于术后6周各处死12只,进行X线摄片,并取整根桡骨进行生物力学实验,A组大鼠于实验开始后1周处死,并取整根桡骨进行生物力学实验。结果1)X线观察:C组:4周和5周时,骨折线较清晰,有少量骨痂形成。6周时,骨折线模糊,仍隐约可见。D组:4周时,骨折线较清晰,5周时,骨折线模糊,6周时骨折线消失,骨折基本愈合。2)生物力学实验:6周时,D组桡骨可承受的最大负荷与A组基本相同,差异无统计学意义(P>0.05),而与C组相比,差异有统计学意义(P<0.05)。3)免疫组织化学染色:PDGF:C组PDGF表达从1 d开始出现,2周左右达到高峰;D组PDGF表达从1 d开始出现,1周时接近高峰,2周达到高峰。在1 d、4 d、1周时,D组PDGF表达较C组显著增高(P<0.01)。C组VEGF表达从1周开始出现,持续到3周左右达高峰;D组VEGF表达4 d开始出现,2周达高峰,并持续到3周左右。在4 d、1周和2周时,D组VEGF表达较C组显著增高,差异有统计学意义(P(0.01)。结论1)根据X线观察结果及生物力学实验结果,D组大鼠骨折愈合速度快于C组。2)单纯骨折后2周左右为PDGF的表达高峰,脑外伤合并骨折后1～2周为PDGF的表达高峰。单纯骨折后3周左右为VEGF表达的高峰期,脑外伤合并骨折后2～3周为VEGF表达的高峰期。其表达高峰提前且持续时间较长。3)脑外伤后骨折愈合加速,这可能与大鼠体内生长因子,特别是VEGF和PDGF表达高峰提前且持续时间较长有关。

Objective To explore the mechanism of platelet-derived growth factor（PDGF） and vascular endothelial growth factor （VEGF） enhanced osteogenesis on SD rats fracture healing after cerebral trauma by investigating the distinct expressions of PDGF and VEGF in fracture only and in fracture with brain injury. Theory basis was afforded for the treatment of refractoriness fracture for clinical selectivity. Methods Two hundred and four rats were divided into four groups randomly： group A, negative control（ n = 12） ; group B, cerebral trauma group （n = 56 ） ; group C, fracture group （n = 68 ） ; and group D fracture with cerebral trauma group （n = 68 ）. The rat models of fracture and cerebral trauma were established. 8 rats in each of group B, C and D were put to death in the first day, fourth day, first week, second week, third week, fourth week and fifth week after the operation. Osteotylus samples were obtained about one centimeter away from broken ends of fractured bone for immunohistochemistry staining. The rats which were put to death in the fourth and fifth week were examined with X-rays to observe the reparative process. And then , 12 rats of group C and D were put to death at the sixth week. They were examined with X-rays and taken the whole left radial bone for biomechanical experiment. Results （1） X-rays ： group C ： In the fourth and fifth week, there were some existing callus and fracture lines were clear. In the sixth week, the fracture lines were not clear but still can be seen. group D： In the fourth week, fracture lines were clear. In the fifth week, the fracture lines were not clear. And in the sixth week, the fracture lines were disappeared. （2） Biomechanical experiment： In the sixth week, the maximum load that radial bones in group A and D can be accepted were nearly the same. When comparing to group C, there was statistical significance（ P 〈 0.01 ）. （3） Immunohistochemistry staining image analysis： PDGF： the expression in group C started to appear in the first day and rose to the peak about in the second week. The expression of PDGF in group D started to appear in the first day, but the first week it was close to the peak, reaching it by the second week in the first day, fourth day and the first week, there was statistical significance between group C and group D（P 〈0.01 ）. VEGF： the expressions of group C appeared in the first week and rose to the peak by about the third week. The expression of VEGF in group D started to appear in the fourth day, reached the peak about the third week. In the fourth day , the first week and the second week, there was statistical significance between group C and D （ P 〈 0.01 ）. Conclusions （1） According to the results of the X-ray and biomechanics experiment, the fracture healing speed in group D is faster than group C. （2） According to the results of immunohistochemistry staining image analysis, the persistence time of the expression of PDGF and VEGF of group D is longer than group C. And the crest-time of group D comes earlier than group C. （3） The acceleration of fracture healing after cerebral trauma may be relevant to longer persistence time and ahead of schedule in expression crest-time of PDGF and VEGF.