急性肾损伤是体外循环（CPB）后主要并发症及死亡原因，与CPB引起的血管内皮细胞损伤密切相关，而损伤后24小时内是修复内皮细胞、减轻肾损伤的"最佳时间"。我们的前期研究发现，循环内皮祖细胞（EPC）可能对肾血管修复起重要作用，然而CPB后24小时EPC及其动员因子显著下降，提示这种修复主要依赖于术前产生的EPC。因此如在CPB前增加EPC（我们称为预动员）可能通过促进肾血管修复而改善肾功能。为此本项目拟研究粒细胞集落刺激因子对EPC预动员的时效关系；使用三维立体培养模型，研究预动员对EPC功能的影响；利用业已建立的小鼠CPB模型，研究预动员EPC对肾脏的保护作用；利用GFP-荧光小鼠、清髓小鼠模型，以及基因沉默技术，研究EPC是否通过直接分化作用和/或旁分泌作用而紧急修复肾血管。本课题的顺利实施为临床预防和治疗急性肾损伤，从而改善CPB后患者预后提供新的理论和实验依据。

Acute kidney injury is one of the major complications after cardiopulmonary bypass (CPB). Currently, vascular endothelial cell injury induced by CPB is taken as one of the main causes related with kidney injury, and the "best time" for vascular endothium repairment may be the first 24 hours after injury. Our pilot studies have shown that circulating endothelial progenitor cell (EPC) may play an important role in repairing renal vascular endothelium via selectively homing to kidney. Unfortuately, we also found that the counts of EPC, as well as EPC stimulator levels, were significantly decreased after CPB, suggesting the repairing of renal vascular endothelium most depends on EPC produced before CPB. We, therefore, hypothesized that increasing EPC counts preoperatively (which we named pre-mobilization) would enhance renal vascular endothelium repairing and thereafter improve renal function. Based on these results, in the project, EPC mobilization via Granulocyte Colony Stimulating Factor (G-CSF) will be observed, and the function of the mobilized EPC will be tested in 3D cell culture system. Then the protective effect of pre-mobilized EPC on kidney will be observed in the established novel mouse CPB model. Using EPC VEGF/HGF gene silencing, GFP-mouse and myeloablative mouse model, the mechanisms whereby will also be elucidated to determine whether the protective effects were through EPC direct differentiation and/or paracine cytokines to urgently repair the renal blood vessel. Obviously, the present project will provide novel theoretical and experimental bases to prevent and treat acute kidney injury associated with CPB, and thus improve the outcomes after CPB for the short terms and the long terms.