足细胞标志蛋白及足细胞疾病

肾小球内有三种固有细胞：系膜细胞、内皮细胞、足细胞。不同的病因可导致不同固有细胞的损伤，在临床上表现为不同类型的肾小球疾病。其中足细胞受损后，临床主要表现为蛋白尿，典型的表现为大量蛋白尿。蛋白漏出是肾小球疾病的常见表现，反过来也是加速肾小球硬化的一个重要因素。随着近年来对足细胞生物学研究的深入，尤其是在发现足细胞表达的一些特异性蛋白分子之后，足细胞现已被认为是参与各种原发或继发性肾小球疾病进展的关键细胞。     

糖尿病肾病足细胞损伤研究进展

糖尿病肾病（diabetic nephropathy,DN）是糖尿病的微血管并发症之一,临床上以持续性蛋白尿和进行性肾功能减退并最终进展至终末期肾衰竭为特征。既往研究认为,DN的主要病理特征是肾小球细胞外基质堆积、系膜增宽、肾小球基底膜（glomerular basement membrane,GBM）增厚,肾小球硬化及间质纤维化,然而这些因素仅能解释30％～50％的尿蛋白排泄率和肾小球滤过率的变化。     

足细胞损伤与蛋白尿发病机理研究进展

肾小球疾病常见临床表现是血尿、蛋白尿、水肿、血压高或正常。蛋白尿是各种肾脏病最重要、最直观的临床表现,其可引起一系列危害如易发生血栓及栓塞,出现低蛋白血症及营养不良,免疫力下降,易并发感染;继发高脂血症,引起有效血容量减少,诱发氮质血症,引起急性肾衰竭。尿蛋白通过刺激肾小管产生活性氧,释放氧自由基,直接破坏肾组织,也可诱导肾小管上皮细胞纤维化因子及炎症因子上调,持续的炎症刺激促进肾小球硬化,诱导肾小管间质纤维化,最终会进入终末期肾衰竭。     

足细胞与糖尿病肾病

糖尿病(diabetes mellitus,DM)的发生率在世界范围内迅速上升[1],而糖尿病肾病(diabetic nephropathy,DN)是糖尿病最严重的慢性并发症之一.在西方国家,需行肾脏替代治疗的患者中,约35%为DN患者[2].我国目前约有4 000万人面临糖尿病危胁,DN占终末期肾衰竭患者的15%[3].DN的主要病理特征是肾小球细胞外基质(extracellular matrix,ECM)堆积,系膜增宽、基底膜(glomerular basement membrane,GBM)增厚,肾小球硬化及伴肾间质纤维化.DN的发病机制仍未完全明确,近年来,肾小球滤过屏障的结构和功能改变,尤其是作为肾小球滤过屏障结构成分的足细胞在DN发生发展中的作用,成为研究热点.本文拟就这方面的研究进展做一综述.     

IgA肾病中足细胞损伤机制的研究进展

IgA肾病（IgAN）是一种常见的原发性肾小球疾病,在我国占原发性肾炎患者的25%～33%,是引起终末期肾衰竭最常见的原因之一[1]。IgAN在诊断后5～25年内,约有15%～40%患者进入终末期肾衰竭而不得不接受肾脏替代治疗[2]。近年来足细胞在IgAN中的损伤成为研究热点,现将足细胞的损伤机制阐述如下。     

发病时的蛋白尿和足突融合在IgA肾病预后判断上的价值

目的：探讨发病时的蛋白尿〉1．0g／d和广泛足突融合在IgA肾病预后判断上的价值。方法：以1998年1月～2005年1月间肾活检诊断为IEA肾病-局灶硬化性肾小球肾炎（IgAN-FSGN）99例为研究对象，分析广泛足突融合和蛋白尿〉1．0g／d与肾小球硬化及小管间质病变的相关性。结果：电镜下显示肾小球脏层上皮细胞足突广泛融合24例（24．2％），足细胞无明显改变（包括足突细胞部分融合）75例（75．8％）。广泛足突融合组的重度肾小球硬化发生率为54．2％（13／24例）明显高于足细胞无明显改变组的28．0％（21／75例）；临床表现尿蛋白〉1．0g／d组44例（44．4％），尿蛋白〈0．5g／d组23例（23．2%）。尿蛋白〉1．0g／d组足突广泛融合的发生率为29．5％（13／44例）明显高于尿蛋白〈0．5g／d组的4．3％（1／23例），尿蛋白〉1．0g／d组的重度肾小球硬化发生率为40．9％（18／44例）明显高于尿蛋白〈0．5g／d组的13．0％（3／23例）。结论：广泛足突融合或蛋白尿〉1．0g／d均与IgAN-FSGN肾小球硬化的加重呈正相关，广泛足突融合可作为IgAN-FSGN病变进展的一个病理学标志，尿蛋白〉1．0g／d可作为反映IgAN—FSGN病变进展的一个临床标志。     

糖尿病肾病足细胞损伤的研究进展

糖尿病肾病（diabetic nephropathy，DN）是糖尿病患者最常见的慢性并发症之一，是导致终末期肾衰竭的重要原因。蛋白尿是DN最常见的临床表现之一，与DN的严重程度密切相关。研究表明，肾小球滤过屏障的结构与功能改变，尤其是作为肾小球滤过屏障结构成分的足细胞在DN发生发展过程中起重要作用。nephrin等足细胞相关蛋白在肾小球裂隙隔膜丢失，可以增加肾小球的某些成分，活化促凋亡通道，进而破坏裂隙膜完整性，使得肾小球滤过电荷屏障减弱，促进蛋白尿的发生，加速了DN进展。有效地控制血糖以及抑制肾素一血管紧张素一醛固酮系统，可起到调节足细胞某种蛋白表达的作用，阻止足细胞的丢失，进而减少蛋白尿的产生。为此本文就足细胞在DN中的作用，以及DN时以足细胞为靶点，减轻DN蛋白尿的治疗作一综述。     

IgA肾病中足细胞损伤及其与蛋白尿的关系

目的 观察 IgA肾病（IgAN）患者足细胞损伤的各种表现，探讨其与蛋白尿的关系。 方法 收集35例伴有明显蛋白尿[尿蛋白量（24 h）>1.0 g]的IgAN患者肾活检组织作研究；以8例肾错构瘤患者术后切除肾和肾癌患者术后远离癌旁肾组织为正常对照。免疫组化方法观察肾组织细胞周期调节蛋白（p21、p27）、足细胞结构蛋白（nestin）、足细胞数目 （WT1）。用显微切割方法取出肾小球，通过实时定量PCR方法检测整合素（integrin）β1、nephrin和α辅肌动蛋白4（α-actinin 4）水平。电镜观察足细胞超微结构的改变。根据足细胞数目密度(Nv, n×106/μm3)将35例IgAN患者分为足细胞数目减少组（ Nv<52.49×106/μm3，n = 15）和足细胞数目正常组（Nv≥52.49×106/μm3，n = 20）。随访蛋白尿的转归情况，共18个月。 结果 （1）与正常对照组比较，IgAN患者肾小球内个别足细胞重新表达p21，而足细胞p27的表达明显降低（0.71±0.12比0.91±0.07，P < 0.05）。（2）IgAN患者足细胞nestin 蛋白表达比正常对照显著降低（13.40%±0.04%比 17.60%±0.04%，P < 0.05）；肾小球内integrin-β1 mRNA表达显著升高（12.54±5.20比1.02±0.30，P < 0.05），而nephrin及α-actinin4 mRNA无明显改变。（3）电镜下观察到明显的足突融合和足细胞从基底膜脱落。（4）IgAN患者足细胞数目密度比正常对照组显著减少(161.27±225.92比323.22±138.12，P < 0.05)，且与Lee氏分级相关。（5）足细胞数目密度、integrin-β1 mRNA与肾穿刺当时的尿蛋白量（24 h）呈负相关(r = -0.4483、-0.840, 均P < 0.05)。足细胞数目减少组较足细胞数目正常组的蛋白尿下降程度明显减少（P < 0.05）。 结论 伴蛋白尿的IgAN中存在足细胞的损伤，表现为足细胞周期调节蛋白、结构蛋白的改变，足突的融合及足细胞数目的减少，而足细胞损伤及足细胞数目减少会影响蛋白尿的发生和发展。     

足细胞与肾小球损伤

随着体外培养技术的发展，已认识到肾小球足突细胞具有其特殊的结构和性质。它参加了初期及进行性肾上球损伤过程，其具有的多种表面抗原及受体结构成份亦可能涉及肾小球免疫损伤的病理过程，已获得的信息资料从根本上改变了人们对它的看法。     

足细胞表型的改变与肾脏疾病

足细胞是一种高度分化的上皮细胞，它的作用包括支持血管球，参与基底膜的合成，调控肾小球的选择通透性，这些都依赖于足细胞的分化成熟并获得表面特殊蛋白分子的表达；研究证实，对足细胞正常结构的维持起重要作用的蛋白分子，它们的突变或缺失，导致足细胞结构的改变，引起蛋白尿和肾小球硬化的发生。本文重点对足细胞表型改变与肾脏疾病相互关系做一综述。     

Angiotensin II-dependent persistent podocyte loss from destabilized glomeruli causes progression of end stage kidney disease

Podocyte depletion is a major mechanism driving glomerulosclerosis. Progression is the process by which progressive glomerulosclerosis leads to end stage kidney disease (ESKD). In order to determine mechanisms contributing to persistent podocyte loss, we used a human diphtheria toxin transgenic rat model. After initial diphtheria toxin-induced podocyte injury (over 30% loss in 4 weeks), glomeruli became destabilized, resulting in continued autonomous podocyte loss causing global podocyte depletion (ESKD) by 13 weeks. This was monitored by urine mRNA analysis and by quantitating podocytes in glomeruli. Similar patterns of podocyte depletion were found in the puromycin aminonucleoside and 5/6 nephrectomy rat models of progressive end-stage disease. Angiotensin II blockade (combined enalapril and losartan) restabilized the glomeruli, and prevented continuous podocyte loss and progression to ESKD. Discontinuing angiotensin II blockade resulted in recurrent glomerular destabilization, podocyte loss, and progression to ESKD. Reduction in blood pressure alone did not reduce proteinuria or prevent podocyte loss from destabilized glomeruli. The protective effect of angiotensin II blockade was entirely accounted for by reduced podocyte loss. Thus, an initiating event resulting in a critical degree of podocyte depletion can destabilize glomeruli and initiate a superimposed angiotensin II-dependent podocyte loss process that accelerates progression resulting in eventual global podocyte depletion and ESKD. These events can be monitored noninvasively in real-time through urine mRNA assays.     

From placenta to podocyte: vascular and podocyte pathophysiology in preeclampsia

Preeclampsia is a disorder of hypertension and proteinuria that affects 6 - 8% of normal pregnancies. Recent research has revealed many molecular mechanisms that may contribute to systemic endothelial dysfunction, glomerular capillary endotheliosis, dysregulation of the glomerular filtration apparatus, and podocyte loss. An ischemic placenta elaborates soluble FMS-like tyrosine kinase 1 (sFlt-1), a soluble receptor for vascular endothelial growth factor (VEGF). A variety of mediators, including nitric oxide, Angiotensin II receptor autoantibodies (AT1AA), and endothelin-1 may serve to maintain placental ischemia and systemic endothelial dysfunction. Endothelin-1 and decreased vascular endothelial growth factor may adversely affect overall expression and distribution of podocyte foot process proteins, leading to proteinuria. Podocyte derangements may lead to podocyte apoptosis and loss, as evidenced by the detection of live podocytes and podocyte products in the urine of preeclamptic women. In this review, we explore recent research elucidating the interactions of placenta, endothelium, and podocyte leading to the clinical syndrome of preeclampsia.     

足细胞骨架蛋白相关分子网络在足细胞损伤和蛋白尿发生中的作用

足细胞,即肾小球脏层上皮细胞,具有复杂的细胞形态和结构,包括胞体以及从胞体依次伸出的主足突和次级足突(foot process)[1]".毗邻足细胞的足突之间形成的裂孔隔膜(slit diaphragm,SD)构成肾小球滤过的最后一道屏障.近来SD组成分子如nepbrin、podocin和CD2AP以及离子通道蛋白TRPC6的发现进一步证实足细胞足突及其SD结构和功能异常是蛋白尿发生的重要原因[2].     

足细胞损伤与糖尿病及其肾病的最新研究进展

近年来糖尿病发病率逐年上升,而糖尿病肾病是糖尿病患者最常见的慢性并发症之一,也是导致终末期肾衰竭的重要原因.近来研究发现,足细胞在保持肾小球滤过屏障的完整性及预防蛋白尿的产生中具有重要作用,足细胞损伤可影响糖尿病肾病的发生发展和预后.本文将就糖尿病中高糖环境和胰岛素抵抗对足细胞生物学功能产生的影响进行综述.     

Aldosterone and glomerular podocyte injury

Aldosterone is traditionally viewed as a hormone regulating electrolyte and blood pressure homeostasis by acting on the distal nephron. Accumulating evidence suggests that aldosterone also plays pathogenetic roles in cardiovascular and renal injury. For example, aldosterone is a potent inducer of proteinuria. We demonstrated that podocyte injury underlies the pathogenesis of proteinuria in aldosterone-infused rats on a high salt diet. Mineralocorticoid receptor was detected in the podocytes in vivo and in vitro, and aldosterone caused induction of its effector kinase Sgk1, activation of NADPH oxidase and generation of reactive oxygen species. Selective aldosterone blocker eplerenone, as well as antioxidant tempol, ameliorated aldosterone-induced podocyte injury and proteinuria. Aldosterone was also involved in the podocyte damage and proteinuria of metabolic syndrome model SHR/NDmcr-cp. Adipocyte-derived aldosterone releasing factors were suggested to contribute to the aldosterone excess of this model. Furthermore, high salt diet markedly worsened the renal injury of SHR/NDmcr-cp. Although salt lowered serum aldosterone levels, it caused MR activation in the kidney. Accordingly, eplerenone dramatically improved the salt-evoked nephropathy. Taken together, aldosterone blockers can be an excellent therapeutic strategy for the treatment of podocyte injury, proteinuria, and cardiovascular and renal complications, not only in high aldosterone states but also in patients with activated MR signaling in the target tissue, whose circulating aldosterone level is not necessarily high. Addition of aldosterone blockers in patients treated with ACEIs or ARBs are also promising, because of "aldosterone breakthrough" phenomenon. Careful monitoring of hyperkalemia is necessary, especially in patients with impaired renal function.     

The effect of acteoside on puromycin nephropathy and podocyte injury model

Objective To explore the effect of acteoside (one of the ingredients of Total Glycosides Extracted from Rehmannia capsules) on treatment of proteinuria and protection of podocytes. Methods In this study, puromycin nephropathy rat model was successfully established. After detecting the degree of proteinuria, the expression of podocyte injury markers and the degree of podocyte foot process fusion were investigated by electron microscope. In addition, puromycin treated podocyte injury model was also successfully established in vitro. Podocyte viability, migration, cytoskeleton and injury marker were detected. Results In vivo study showed that acteoside could effectively reduce proteinuria (P＜0.05), restore the expression of podocyte injury markers such as nephrin and synaptopodin (all P＜0.05), and alleviate the degree of podocyte foot process fusion. In vitro study showed that acteoside could effectively restored podocyte viability (P＜0.05), reduce abnormal migration ability (P＜0.05), protecte cytoskeleton and restore the expression of podocyte injury marker nephrin (P＜0.05). Conclusions This study confirms that acteoside can reduce the degree of proteinuria in puromycin nephropathy rat model in vivo and alleviate the degree of podocyte injury in vitro as well as enrich the molecular mechanism of Total Glycosides Extracted from Rehmannia capsules in treatment of proteinuria.     

Enzymatic disease of the podocyte

Proteinuria is an early sign of kidney disease and has gained increasing attention over the past decade because of its close association with cardio-vascular and renal morbidity and mortality. Podocytes have emerged as the cell type that is critical in maintaining proper functioning of the kidney filter. A few genes have been identified that explain genetic glomerular failure and recent insights shed light on the pathogenesis of acquired proteinuric diseases. This review highlights the unique role of the cysteine protease cathepsin L as a regulatory rather than a digestive protease and its action on podocyte structure and function. We provide arguments why many glomerular diseases can be regarded as podocyte enzymatic disorders.