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。     

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。     

蛋白尿形成相关足细胞的结构蛋白

蛋白尿是肾小球疾病的基本表现之一,是促使肾脏疾病进展的重要因素。足细胞损伤和结构蛋白改变被认为是蛋白尿形成的主要原因。目前有关蛋白尿形成相关足细胞的结构蛋白的进一步研究,揭示了足细胞的结构蛋白性质、定位、功能等方面的部分特性,使我们对它们有了初步了解,本文就近年来蛋白尿形成相关足细胞的结构蛋白相关文献进行总结希望对今后的研究有所帮助。     

足细胞与Alport综合征蛋白尿的关系

目的 探讨足细胞与Alport综合征（AS）蛋白尿的关系。 方法 AS 患者21例,男13例,女8例,根据24 h尿蛋白量将患者分3组, 10例<30 mg/kg为轻度蛋白尿组, 4例30~50 mg/kg为中度蛋白尿组,7例>50 mg/kg为重度蛋白尿组。正常肾组织对照3例。电镜下根据平均足突宽度=л/4×（Σ基底膜长度/Σ足突个数）,计算每例患者足突宽度。分析足突宽度与蛋白尿关系。用免疫组化方法分析肾组织中裂孔隔膜分子nephrin、podocin和细胞骨架分子synaptopodin的表达。 结果 AS患者肾小球足细胞足突宽度（420~2270 nm）与24 h尿蛋白量呈正相关（r = 0.765,P < 0.01）。轻度蛋白尿组足突宽度[475（420~900 nm）]显著低于重度蛋白尿组[1520（480~2270） nm]（P < 0.05）。重度蛋白尿组患儿nephrin和podocin表达分布发生改变;表现为弥漫足突融合者synaptopodin表达分布发生改变。2例蛋白尿病程较短（1年）患儿无弥漫足突融合,synaptopodin分布正常,但nephrin和podocin分布异常。 结论 肾小球足细胞足突融合、裂孔隔膜及足细胞骨架分子参与AS患儿大量蛋白尿的发生,裂孔隔膜损伤似乎早于足细胞骨架改变。对蛋白尿早期干预可能有助于延缓疾病进展。     

足细胞损伤与肾小球硬化

足细胞是肾脏固有细胞之一，近几年随着多种足细胞标记蛋白的发现，足细胞损伤在蛋白尿和肾小球硬化中的作用越来越受到重视。本文就足细胞近几年的研究进展及足细胞损伤与肾小球硬化的关系作一综述。     

肾小球足突细胞裂隙隔膜与蛋白尿发生机制

从蛋白水平和基因水平探明GPSD蛋白分子Tnephrin、Podocin、CD2AP、α肌动蛋白4(α-actnin-4)以及其它与QPSD相关蛋白分子并进一步确立GPSD的“拉链式”结构使人们认识到GPSD是肾小球滤过屏障的关键结构，是真正的“分子筛”滤过屏障。上述蛋白分子组成改变和戚相关基因的突变可以导致蛋白尿和肾病综合征。     

肾小球足突细胞裂隙隔膜与蛋白尿发生机制

从蛋白水平和基因水平探明GPSD蛋白分子nephrin、Podocin、CD2AP、α肌动蛋白4(α-actnin-4)以及其它与GPSD相关蛋白分子并进一步确立GPSD的"拉链式"结构使人们认识到GPSD是肾小球滤过屏障的关键结构,是真正的"分子筛"滤过屏障.上述蛋白分子组成改变和/或相关基因的突变可以导致蛋白尿和肾病综合征.     

足细胞损伤与肾小球硬化

足细胞是肾脏固有细胞之一 ,近几年随着多种足细胞标记蛋白的发现 ,足细胞损伤在蛋白尿和肾小球硬化中的作用越来越受到重视。本文就足细胞近几年的研究进展及足细胞损伤与肾小球硬化的关系作一综述。     

维生素D受体在糖尿病肾病足细胞损伤及蛋白尿缓解中的作用

目的探讨维生素D受体(VDR)在糖尿病肾病(DKD)足细胞中的表达水平及在足细胞损伤及蛋白尿缓解中的作用。方法(1)本研究纳入了65例诊断患有2型糖尿病(伴或不伴蛋白尿)的患者,并纳入了25例年龄和性别相匹配的健康体检者为对照组。根据白蛋白/肌酐(ACR)的尿排泄比例对2型糖尿病患者进行分组,分别为无蛋白尿(ACR<30 mg/g,n=24)、微量白蛋白尿(ACR 30~300 mg/g,n=18)和临床蛋白尿(ACR>300 mg/g,n=23)。另选择25例经肾活检确诊的DKD患者作为DKD组。正常肾脏组织标本均取自泌尿外科同一时期肾脏肿瘤切除患者10例。将各组检测指标进行对比,同时采用实时定量PCR、ELISA法和免疫组化法检测VDR在各组患者的血液、尿液样本和肾脏组织中的表达情况,以及使用Pearson相关分析分析VDR与尿蛋白的相关性。(2)在2型糖尿病肾病小鼠模型中对上述结果进行验证,将遗传背景均为C57BLKs/J的雄性db/db小鼠及同窝出生的db/m小鼠,随机分为正常对照组(A组)、DKD对照组(B组)、DKD二甲基亚砜处理组(C组)、DKD帕立骨化醇(VDR激动剂)处理组(D组),C、D组连续腹腔注射处理8周,对照组不做任何处理。小鼠10周龄时开始连续干预8周,在小鼠22周龄(开始干预后12周)检测各组小鼠体重、血、尿生化指标对比;Western印迹法检测β⁃catenin、VDR的变化;免疫荧光观察足细胞标志蛋白podocin及足细胞损伤蛋白α⁃SMA的表达变化。结果(1)与正常健康对照组相比,无蛋白尿组、微量白蛋白尿组和临床蛋白尿组的糖尿病患者血浆中VDR的mRNA和蛋白水平均较低(均P<0.05);与无蛋白尿组的糖尿病患者相比,微量白蛋白尿组和临床蛋白尿组的糖尿病患者血浆中VDR的mRNA和蛋白水平均较低(均P<0.05)。(2)与正常健康对照组相比,无蛋白尿糖尿病组和DKD组患者血浆中VDR的mRNA和蛋白水平均较低(均P<0.05);与无蛋白尿糖尿病组患者相比,DKD组患者血浆中VDR的mRNA和蛋白水平亦较低(均P<0.05)。(3)免疫组化结果显示,DKD组肾组织中VDR的表达明显少于正常对照组。(4)DKD患者血浆中VDR mRNA相对水平与ACR呈负相关(r=-0.342,P<0.05)。(5)各组尿液上清液中VDR的水平与血浆中的水平呈相反趋势。(6)Western印迹结果显示,B组、C组肾小球足细胞β⁃catenin蛋白表达高于D组(均P<0.05),VDR蛋白的表达低于D组(均P<0.05);免疫荧光结果显示,B组、C组肾小球足细胞podocin的表达低于D组(均P<0.05),α⁃SMA的表达高于D组(均P<0.05)。结论VDR高表达缓解DKD足细胞损伤及蛋白尿。     

miRNAs与足细胞损伤的关系及研究进展

微小RNA(miRNAs)广泛参与了基因表达和转录、表观遗传调节、细胞周期控制、分化和免疫反应等生物学过程,其异常表达与癌症、心血管、神经病学及代谢性疾病等多种疾病相关,其中也包括了足细胞损伤。本文就miRNAs的结构和功能、足细胞损伤在肾脏疾病中的作用、miRNAs在各种疾病导致的足细胞损伤等病理生理过程中的作用及其...     

Inhibition of Podocyte FAK Protects against Proteinuria and Foot Process Effacement

Focal adhesion kinase (FAK) is a nonreceptor tyrosine kinase that plays a critical role in cell motility. Movement and retraction of podocyte foot processes, which accompany podocyte injury, suggest focal adhesion disassembly. To understand better the mechanisms by which podocyte foot process effacement leads to proteinuria and kidney failure, we studied the function of FAK in podocytes. In murine models, glomerular injury led to activation of podocyte FAK, followed by proteinuria and foot process effacement. Both podocyte-specific deletion of FAK and pharmacologic inactivation of FAK abrogated the proteinuria and foot process effacement induced by glomerular injury. In vitro, podocytes isolated from conditional FAK knockout mice demonstrated reduced spreading and migration; pharmacologic inactivation of FAK had similar effects on wild-type podocytes. In conclusion, FAK activation regulates podocyte foot process effacement, suggesting that pharmacologic inhibition of this signaling cascade may have therapeutic potential in the setting of glomerular injury.The glomerulus forms the filtration barrier of the kidney and is composed of a fenestrated endothelium, glomerular basement membrane (GBM), and the podocytes that interdigitate to form slit diaphragms.^1,2 When the podocytes are damaged, foot process fusion occurs. This process involves the rearrangement of the actin cytoskeleton and retraction of the foot processes toward the cell body, allowing mechanical forces and signaling events to be transmitted into the cell. Since the identification that mutations of the podocyte slit diaphragm specific NPHS1 gene cause congenital nephrotic syndrome,^3–5 podocytes have been recognized as critical regulators of glomerular injury. Other podocyte slit diaphragm proteins such as podocin, synaptopodin, and CD2AP have generated further interest in the regulation of the kidney filtration barrier^6–8; however, little is still known about cell–matrix interactions in podocytes. Mice lacking the focal adhesion protein integrin-linked kinase (ILK), specifically in the podocytes, also develop proteinuria, resulting in renal failure and death.⁹ Moreover, mice lacking α3β1 integrin have demonstrated inability to form mature foot processes.¹⁰ These cell–matrix interactions, which seem important in podocyte development, may also play a critical role after podocyte injury, because the process of podocyte effacement requires cell process retraction and movement, processes that suggest focal adhesion disassembly.Focal adhesion kinase (FAK) is a nonreceptor tyrosine kinase, in which integrin- or growth factor–induced autophosphorylation at tyrosine 397 results in activation of critical signaling pathways required for focal adhesion turnover.^11–16 It has been demonstrated that cell spreading and migration are significantly diminished in cells lacking FAK.¹⁷ This inhibition in motility has brought excitement in cancer therapeutics, resulting in the development and use of FAK inhibitors.^18–21 In a recent study, inhibition of urokinase plasminogen activator (uPAR), a glycosylphosphatidylinositol-anchored protein that is important for cell invasion and metastasis, has been demonstrated to reduce proteinuria and podocyte effacement significantly, suggesting that this dynamic podocyte cell movement may mimic the molecular signaling events observed in cancer cell invasion.²²In this study, we demonstrated that after podocyte injury in vivo and in vitro, FAK activation was significantly increased in wild-type (WT) mice, prompting us to address whether inhibition or loss of FAK activation would reduce podocyte cell motility by inhibiting focal adhesion turnover, thereby preventing proteinuria and effacement. Because complete FAK gene deletion results in lethality at embryonic day 8.5, a time point before glomerular development has been initiated, the ability to study this protein''s role in podocyte development as well as repair after injury has been limited.¹⁷ Hence, selective loss of FAK expression in the podocytes of the kidney was achieved using a Cre-loxP approach.^23,24 These mice were born without evidence of podocyte/glomerular developmental defects but were resistant to the foot process fusion and subsequent proteinuria that typically accompany LPS and rabbit anti-mouse GBM-induced podocyte damage. We postulate this inhibition of foot process effacement is due to diminished podocyte spreading and motility, supported by our in vitro data. In addition, pharmacologic treatment of WT mice using the FAK inhibitor TAE-226 significantly reduced proteinuria and podocyte effacement, raising the possibility for therapeutic use in glomerular diseases.     

足细胞损伤与IgA肾病

近年来,许多不同的病因基本是通过足细胞的损伤而启动IgA肾病的进程,尤其对足细胞多种蛋白分子的研究可进一步了解IgA肾病的发病机制.     

足细胞损伤与IgA肾病

近年来,许多不同的病因基本是通过足细胞的损伤而启动IgA肾病的进程,尤其对足细胞多种蛋白分子的研究可进一步了解IgA肾病的发病机制.     

Urine Podocyte mRNAs,Proteinuria, and Progression in Human Glomerular Diseases

Model systems demonstrate that progression to ESRD is driven by progressive podocyte depletion (the podocyte depletion hypothesis) and can be noninvasively monitored through measurement of urine pellet podocyte mRNAs. To test these concepts in humans, we analyzed urine pellet mRNAs from 358 adult and pediatric kidney clinic patients and 291 controls (n=1143 samples). Compared with controls, urine podocyte mRNAs increased 79-fold (P<0.001) in patients with biopsy-proven glomerular disease and a 50% decrease in kidney function or progression to ESRD. An independent cohort of patients with Alport syndrome had a 23-fold increase in urinary podocyte mRNAs (P<0.001 compared with controls). Urinary podocyte mRNAs increased during active disease but returned to baseline on disease remission. Furthermore, urine podocyte mRNAs increased in all categories of glomerular disease evaluated, but levels ranged from high to normal, consistent with individual patient variability in the risk for progression. In contrast, urine podocyte mRNAs did not increase in polycystic kidney disease. The association between proteinuria and podocyturia varied markedly by glomerular disease type: a high correlation in minimal-change disease and a low correlation in membranous nephropathy. These data support the podocyte depletion hypothesis as the mechanism driving progression in all human glomerular diseases, suggest that urine pellet podocyte mRNAs could be useful for monitoring risk for progression and response to treatment, and provide novel insights into glomerular disease pathophysiology.Human glomerular diseases are heterogeneous but can collectively be viewed as a spectrum of podocytopathies.¹ Podocyte depletion per se causes glomerulosclerosis in model systems^2–5 and is associated with progressive glomerulosclerosis in humans.^6–12 Podocyte damage causes damage to other podocytes¹³ and activation of the renin-angiotensin system (RAS), which, in turn, drives angiotensin II–dependent further podocyte detachment from destabilized glomeruli.¹⁴ In model systems glomerulosclerosis is initiated when >30% of podocytes have been lost from glomeruli.¹⁴ Quantitative podocyte depletion from glomeruli results in mesangial expansion (10%–20% depletion), adhesions to the Bowman capsule (30% depletion), FSGS (30%–50% depletion), and then global sclerosis (70%–90% depletion) associated with interstitial fibrosis.^4,14 Model systems demonstrate that throughout the progression process podocytes continue to detach and appear in the urine, where they can be monitored noninvasively through quantitation of urine pellet mRNAs.^14–17 Collectively, these findings describe key elements of the podocyte depletion hypothesis for progression of glomerular diseases, whereby progressive depletion of podocytes leads through a series of stages to glomerulosclerosis and ultimately to ESRD.Although increased urine podocyte excretion has also been documented in some inflammatory and noninflammatory glomerular diseases in humans,^12,18–35 the role of podocyte depletion in progression remains unproven. We therefore used urine pellet mRNAs to test the hypothesis that progression to ESRD in human glomerular diseases would also be associated with increased urine podocyte mRNAs, regardless of the underlying cause of glomerular injury. Because proteinuria is a well established marker of kidney disease progression^36,37 but varies in extent and relationship to progression in different diseases, we also examined the relationship between proteinuria and rate of podocyte detachment. Establishing that human glomerular diseases follow the rules defined in model systems of progression would provide a foundation for understanding the progression mechanism in human glomerular diseases and the potential for urine podocyte mRNAs to be clinically useful.