VEGF、TGF-β1在骨缺损不愈合中表达的实验研究

目的观察骨缺损不愈合和骨折愈合过程中血管内皮细胞生长因子(vascularendotheligrowthfactor,VEGF)和转化生长因子β1(transforminggrowthfactor,TGF-βl)的表达差异,研究骨缺损不愈合的分子机理,进一步探讨VEGF和TGF-β1对骨折愈合的影响。方法建立兔桡骨干骨缺损不愈合模型和骨折愈合模型,术后1、2、4、6、8、12周取标本,进行组织学观察,采用免疫组织化学的方法(SP法)检测两种模型中VEGF和TGF-β1的表达和变化。结果组织学观察发现,骨缺损组骨折断端只有少量膜内成骨过程,形成的血肿和肉芽组织明显增多,只有靠近骨折断端的一部分形成软骨细胞,其中的一部分在分化到肥大软骨细胞阶段时则停止分化,出现肥大软骨细胞区的增加,并向纤维结缔组织转化,未转化成软骨细胞的肉芽组织在后期也形成了纤维结缔组织。与骨折愈合模型相比,软骨内成骨过程中血管生成的量也明显减少,而且在骨缺损组的各时段,骨折断端间都有肌纤维侵入。免疫组织化学检查发现,VEGF和TGF-β1在骨缺损不愈合中仍有表达,但与正常骨折愈合相比,表达的量明显减少(P<0.05),VEGF和TGF-β1的表达呈同步关系,即在TGF-β1强表达时,VEGF的表达程度也很强,TGF-β1的表达弱时,VEGF的表达也明显减少。结论由于造成较大段的骨缺损,骨膜缺损很多,造成膜

An experimental study of vascular endothelial growth factor and transforming growth factor β1 expression in bone defect resulted from non-union

Objective To observe the expression of vascular endothelia l growth factor (VEGF)and transforming growth factor a 1 (TGF-a 1 )in callus of non-union,bone defect for investigation of the molecular mechanisms of bone defect resulted from non-union,and further explore the co rrelative influences of VEGF and TGF-a 1 in fracture healing.Methods The bone defect resulted from non-union model and the fracture healing model were established in the radius of rabbit.The sp ecimens of callus and soft tissue were collected postoperatively at1,2,4, 6,8and12weeks.The expressions of VEGF and TGF-a 1 were in-vestigated by means of immunohistochemistry(SP method).Results There was no sign of subperiosteal healing except a large segment filled with hemorrhage and granulation tissue in bone defect area.There was only a little amount of granulation tissues transforming into chondrocytes.Some chondrocyt es stopped prolif-erating after reaching hyper-trophic chondrocyte stage but changed into fibrous connective tissues.Most of the granulation tissue finally changed to fibrous connective tissues in the fracture gap.In addition,there w ere a large number blood vessels invading the normal fracture healing site than that in non-union.In im muno-histochemistry observation,there were significa nt decreasing expressions of VEGF and TGF-a 1 in callus of different period of non-union comparing to union(P<0.0 5).Furthermore,both TGF-a 1 and VEGF ex-pressed the same trend in the different period.Conclusion Th e most important mechanism of nonunion derived from large bone defect is the s evere damage of the periosteum which is most responsible for fracture repair. Since the micro-environment of fracture is expanded in large bone defect area ,the large mass of clots and tissues between the fracture ends can not develo pe into chondrocytes totally due to the poor working concentration of bone gro wth factors as a result of the granulation tissues changing to the fibrous conn ective tis sues;and eventually some hypertrophic chondrocytes transformed into fibrous connective tissues.On the oth er hand,The loss of an environment of hypoxia caused poor expression of VEGF and subsequently lead-ing to poor a ngio genesis.This is another factor causing non-union in cases with large bon e defect.