大鼠骨折端两侧骨膜下多点注射pBLAST49-mVEGF质粒、脂质体混合物对骨折愈合的作用不同时间点骨折局部血管内皮生长因子表达的随机、空白对照

背景:研究表明骨折后72h～3周骨折断端血管内皮生长因子呈持续高表达,推测其对骨折愈合有促进作用,通过血管内皮生长因子基因转染的方式诱导治疗性血管生成的研究正受到人们关注。目的:通过局部注射阳离子脂质体转染剂和质粒混合物寻找外源性血管内皮生长因子体内转染的有效途径,以及其基因表达对于骨折愈合的促进作用。设计:随机分组、空白对照实验。单位:四川大学华西医学中心动物实验室。对象:成年雄性SD大鼠40只,体质量230～250g。随机分为实验组和对照组,每组20只。方法:实验于2003-04/12在四川大学华西医学中心动物实验室完成。40只大鼠建立右侧股骨干骨折模型。于股骨中段切断,断端间相距1mm,于髁间倒置入直径1mm的克氏针,固定骨折断端。实验组将脂质体转染剂100μL和pBLAST49-mVEGF100μg质粒混合物两侧骨膜下多点注射,对照组注射等量生理盐水。于术后3,7,14,28,42,56,70d分别处死各组大鼠2只取右侧股骨标本。主要观察指标:两组大鼠各时间点右侧股骨断端标本观察:①大体观察。②X射线摄片结果。③组织学结果。④血管内皮生长因子免疫组织化学染色结果,以胞浆中出现棕黄色颗粒为阳性。结果:两组大鼠7个时间点各选2只,共28只进入结果分析,剩余12只剔除。①不同时间点大鼠骨折端大体标本和X射线片结果观察:实验组骨折端28d软骨骨痂出现并逐渐替代纤维骨痂,骨折线消失,术后56d骨折完全愈合;对照组28d可以看见纤维骨痂,骨折线仍然很清楚,56d才有较多骨痂出现,骨折线开始变模糊。②大鼠骨折端组织学结果观察:骨折端切片后组织细胞经苏木精-伊红染色,实验组术后56d,骨折完全愈合,重新塑形,髓腔再通;对照组术后56d,骨折未完全愈合,髓腔未再通。③不同时间点大鼠骨折端血管内皮生长因子免疫组织化学染色结果:两组表达均于14d达到高峰,28d开始下降。实验组血管内皮生长因子表达明显高于对照组。结论:大鼠骨膜下局部注射阳离子脂质体转染剂和质粒混合物是一种有效的体内转染途径;pBLAST49-mVEGF基因转染能有效促进大鼠骨折的愈合。

Effect of multiple-point injection of the mixture of pBLAST49-mVEGF plasmid and liposomes into the subperiosteum on both sides of the fractured bone of rats on fracture healing: Expression of vascular endothelial growth factor at the local part of the fractured bone at different time points through a randomized blank control trial

BACKGROUND: Research has shown that the vascular endothelial growth factor (VEGF) of the ends of the fractured bone is heavily expressed 72 hours to 3 weeks after the fracture and it is supposed that it has a promoting effect on fracture healing. Inducing angiogenesis through VEGF gene transfection has gradually attracted the attention of the researches.OBJECTIVE: To find an efficient way of exogenous VEGF gene in vivo transfection through injecting the mixture of positive ion liposome transfection agent and plasmid and to study the promoting effect of extra VEGF gene expression on bone fracture healing.DESIGN: A randomly grouping, blank control trial.SETTING: Animal Laboratory of Huaxi Medical Center of Sichuan University MATERIALS: Totally 40 adult male SD rats, weighing 230 to 250 g,were involved. All the animals were randomly divided into the experiment group and the control group with 20 rats in each group.METHODS: The experiment was conducted at the Animal Laboratory of Huaxi Medical Center of Sichuan University from April to December 2003.Altogether 40 rats were involved to establish fractured models of right shaft of femur. Cut the bone in the middle of bone stem, retroplanted a Kirsh' nail with 1 mm diameter through intercondylar part and the fractured bone was fixed. In the experimental group, a mixture of 100 μL of liposome transfection agent and 100 μg of pBLAST49-mVEGF plasmid was injected in multiple points into the subperiosteum of the both sides of the ends of the fractured bone. The same volume of normal saline was injected into the rats in the control group. Then, 2 rats in each group were put to death 3,7,14,28,42,56,70 days after the operation and femoral bone specimen was collected.MAIN OUTCOME MEASURES: Observation of right femoral fractured staining results of VEGF, with the apperance of brown granules as positive.RESULTS: Two rats were selected at 7 time points separately, and altogether 28 rats entered the stage of result analysis. The other 12 rats were fracture at different time points: For the experimental group, 28 days after the operation, cartilage callus appeared and replaced fibrocallus gradually,and the fracture line disappeared. Fifty-six days after the operation, the bone healed completely. For the control group, 28 days after the operation , fibrocallus was observed, and the fracture line was still clear. 56days after the operation, much callus appeared, and the fracture line beof fractured bone was stained with hemotoxylin eosin (HE). In the experiment group, 56 days after the operation, the bone healed completely and trabecular like bones were rebuilt. The bone marrow cavity of the fractured region was open again. In the control group, Fifty-six days after the operation, no mature bone was formed, and the bone marrow cavity was not different time points: The expression in the two group reached to the peak on day 14 and began to decrease on day 28. The expression of VEGF in the experimental group was obviously higher than that in the control group.CONCLUSION: Injection of the mixture of positive ion liposome transfection agent into the subperiosteum of rats is an effective approach for in vivo transfection and pBLAST49-mVEGF gene transfection can effectively facilitate the bone fracture healing of rats.