骨形态发生蛋白4在高糖环境下静脉桥再狭窄进程中的作用及其机制研究

Diabetic patients had an increased propensity for vein graft failure following coronary artery bypass grafting (CABG) compared with patients without diabetes. Although the underlying mechanisms for such a high prevalence of graft failure in the CABG patients with diabetes are not well-characterized, hyperglycemia-induced proliferative disorders within the venous wall is believed to be the primary cause. More recently, bone morphogenic protein-4(BMP4) has been recognized as a pro-proliferative，pro-inflammatory and proatherogenic mediator in the arterial wall. Previously, our study demonstrated a marked increase of BMP4 expression in venous conduits from diabetic patients and in venous endothelial cells (VECs) exposed to high glucose level. Such an increase of BMP4 causally contributes to the impairment of venous endothelial barrier function. Meanwhile, BMP4 antagonist shows no effect on endothelial properties in veins from the normal controls and the non-diabetic patients. Although the biological responses inherent to arterial and venous vessel are different, common cellular and molecular elements may be involved in the post-injury remodeling process of the vascular wall. Moreover,with regard to the important role of VECs dysfunction in the pathogenesis of vein graft failure, we hypothesize that BMP4 might actively participate in the process of neointima formation,smooth muscle cells activation, as well as superimposed atherosclerosis within the venous wall in the setting of diabetes.In the present study, human saphenous vein segments, smooth muscle cells and diabetic rat vein graft model are used to investigate the functional role of BMP4 in the pathogenesis of vein graft failure under hyperglycemic condition. This study may open new horizons in therapeutic interventions aiming at improving long-term vein graft patency in CABG patients with diabetes.

静脉管壁在高糖环境下增殖性重构加剧被认为是冠脉手术后糖尿病患者静脉桥过早失效的根本原因，但机制不祥。近期文献报道，骨形态发生蛋白-4（BMP4）在动脉血管中具有促增殖，促炎性反应和促粥样硬化的作用。前期研究中，我们发现静脉管壁内BMP4表达上调与高糖环境诱导的静脉内皮细胞（VECs）损伤密切相关。由于静脉桥再狭窄进程始于VECs损伤后修复，而静脉与动脉血管损伤后存在着相似的细胞反应机制。我们推测BMP4可能在高糖环境下静脉桥VECs损伤后新生内膜形成，平滑肌细胞 (SMCs) 增殖和粥样硬化形成等环节起了关键性的调控作用。为此本项目拟制备人大隐静脉血管和SMCs高糖培养模型，利用已建立的糖尿病大鼠静脉桥狭窄模型，以及基因沉默，免疫蛋白电泳，RT-PCR等技术，从整体-血管环-细胞层面证实我们的假说。此研究将进一步揭示高糖环境下静脉桥加速失效的潜在机制，为其有效防治提供新思路和新靶点。

高糖环境下静脉桥管壁增殖性重构加剧被认为是冠状动脉旁路移植术（CABG）后糖尿病患者静脉桥过早失效的根本原因，但机制不详。我们推测骨形态发生蛋白-4（BMP4）可能在高糖环境下静脉桥内皮细胞损伤后新生内膜形成、平滑肌细胞（SMCs）增殖和粥样硬化形成等环节起了关键性的调控作用。为此本项目展开了以下研究：1）研究了合并糖尿病的CABG患者原位大隐静脉的形态学变化以及BMP4在其管壁中的表达与分布情况，发现糖尿病患者大隐静脉内膜和中膜较非糖尿病患者明显增厚，且管壁增厚程度与管壁内BMP4的高表达密切相关，提示BMP4在高糖环境下原位静脉桥管壁增殖性改变及静脉移植术后桥血管增殖重构进程中起了重要的促进作用。2）通过构建糖尿病大鼠自体静脉桥模型，应用基因沉默技术特异性抑制BMP4在静脉桥中的表达，观察静脉桥的形态学变化以及BMP4和增殖细胞抗原Ki-67在其管壁中的表达与分布情况，发现BMP4的高表达水平促进了糖尿病大鼠静脉桥Ki-67的阳性表达以及管壁增殖性病变，加速了糖尿病大鼠自体静脉移植术后的桥血管增殖重构进程，靶向沉默BMP4可降低高糖环境下静脉桥中膜SMCs的增殖迁移，从而延缓桥血管再狭窄进程。3）通过制备高糖培养的人大隐静脉SMCs模型，发现高糖环境下BMP4通过介导下游的Smad1-p38MAPK/ERK信号通路参与调控静脉SMCs的增殖和迁移。4）采用lncRNA芯片技术对大鼠静脉桥组织中基因表达谱进行全方位分析，发现了BMP4上游呈时间依赖性下调的lncRNA。综上所述，本研究揭示了高糖环境下静脉桥加速失效的潜在机制，BMP4在高糖环境下静脉桥中膜平滑肌细胞增殖、迁移及管壁增殖重构进程中起了重要的促进作用，以BMP4为靶点的治疗策略将有助于防治高糖环境下静脉桥管壁增殖性重构加剧。本研究为探索高糖环境下静脉桥加速失效的机制提供了新思路，为进一步改善糖尿病患者CABG术后静脉桥近远期通畅率提供了新靶点。