肝细胞生长因子抑制MRC-5成纤维细胞所致的纤维化作用

本研究采用人胎儿肺来源的成纤维细胞株MRC－5，作为体外研究肝细胞生长因子（HGF）抗组织纤维化的模型。成纤维细胞MRC－5被转化生长因子β1（TGF－β1）转化为肌成纤维细胞后，应用外源人重组HGF修饰细胞，检测细胞中分子表达水平的变化。研究发现，TGF－β1在诱导成纤维细胞株MRC－5转化为肌成纤维细胞的同时，上调HGF受体/c-Met在肌成纤维细胞中的表达。而且，应用外源人重组HGF修饰细胞后，内源性TGF－β1的表达水平被降低，内源性HGF的表达水平上调，基质金属蛋白酶I（MMP－I）mRNA表达增加，从而加速了细胞外基质主要成分－胶原蛋白I[Col(I)]的水解。结果显示在组织纤维经过程中，HGF通过其受体c-Met直接作用于肌成纤维细胞，抑制细胞内TGF－β1的表达，在一定程度上抑制组织纤维化的发生和发展。研究中我们还发现，肝素结合表皮生长因子样生长因子（HB－EGF）上调肌成纤维细胞中HGF的表达，是其抑制肌成纤维细胞形成、抑制组织纤维化的可能机制之一。     

氨基胍降低肺纤维化大鼠肺成纤维细胞表达仅α-平滑肌肌动蛋白

摘要：目的 探讨氨基胍（Aminoguanidine, AG）对转化生长因子-β1（Transforming growth factor -beta1, TGF-β1）诱导大鼠纤维化肺成纤维细胞表达 -平滑肌肌动蛋白（ -smooth muscle actin, α-SMA）的影响。方法 用MTT法选择药物浓度。应用免疫细胞化学技术测定α-SMA阳性细胞百分率，用Motic图象分析系统测定其平均积光灰度值。应用流式细胞技术测定单个细胞表达α-SMA的均道值。结果 α-SMA阳性细胞百分率、平均积光灰度值及均道值AG单独刺激组与对照组比无明显差异，TGF-β1单独刺激组（10ng/ml）明显高于对照组（P＜0.01）；AG（500μM）+ TGF-β1（10ng/ml）联合刺激组低于TGF-β1单独刺激组（P＜0.05）。结论 AG单独作用不影响大鼠纤维化肺成纤维细胞表达α-SMA，但是AG能够削弱TGF-β1诱导大鼠纤维化肺成纤维细胞表达α-SMA的能力。     

肌成纤维细胞在肺纤维化中的来源和作用

目前对于肺纤维化（pulmonary fibrosis ,PF）中肌成纤维细胞的来源还不是很清楚,主要有3种假说：肺部原有成纤维细胞转化成为肌成纤维细胞、肺泡上皮细胞穿越基底膜到达纤维化病灶,经上皮-间充质细胞转化为肌成纤维细胞、血液中的纤维细胞到达纤维化病灶转化为肌成纤维细胞等。肌成纤维细胞在PF的病理进程中扮演着重要的角色,其胶原合成能力强可造成细胞外基质的异常沉积、具收缩性使肺顺应性下降、分泌多种炎性介质加重肺泡上皮损伤。     

血小板反应蛋白1在转化生长因子β1诱导的大鼠心肌成纤维细胞中的作用

目的:观察血小板反应蛋白1(TSP-1)在转化生长因子β1(TGF-β1)诱导大鼠心肌成纤维细胞中的作用.方法:差速贴壁法分离新生Sprague-Dawley(SD)大鼠心肌成纤维细胞(CFs).MTT法测CFs生长,羟脯氨酸法测CFs胶原含量,RT-PCR法测TSP-1mRNA表达.结果:TGF-β1诱导CFs TSP-l的表达呈浓度一时间依赖性增加(P<0.01).TGF-β1(20ug/L)作用下24 h可诱导CFs增殖和胶原合成(P<0.01).TSP-l反义寡核苷酸作用后的CFs的MTTA值、胶原含量减少(P<0.01).结论:TGF-β1可诱导新生大鼠CFs TSP-1表达,TSP-1反义寡核苷酸对TGF-β1诱导大鼠CFs增殖与胶原合成具有明显的抑制作用,TSP-1在TGF-β1诱导大鼠心肌纤维化中可能具有重要的作用.     

低氧对人胚肺成纤维细胞转化生长因子β1表达的影响

应用核酸原位杂交及增强化学发光免疫斑点法,观察常氧（Ｎ）、低氧（Ｈ）、常氧和低氧猪肺动脉内皮细胞条 件培养液（ＮＥＣＣＭ和 ＨＥＣＣＭ）对人胚肺成纤维细胞转化生长因子β_１（ＴＧＦβ_１） ｍＲＮＡ和蛋白表达的影响。结果表 明：Ｈ组ＴＧＦβ_１ｍＲＮＡ表达为Ｎ组的１．３６倍（Ｐ＜０．０１）,同时在其培养上清液中,ＴＧＦβ_１蛋白含量也明显升高为Ｎ 组的１．８倍。ＨＥＣＣＭ组ＴＧＦβ_１ｍＲＮＡ和蛋白表达较ＮＥＣＣＭ组均下降,ｍＲＮＡ为ＮＥＣＣＭ组的９０％,Ｐ＜０．０１。蛋 白含量为后者的６２．２％。提示：（１）低氧促进入胚肺成纤维细胞合成和分泌ＴＧＦβ_１。（２）在低氧条件下,肺动脉内皮 细胞可能合成某种因子,抑制成纤维细胞ＴＧＦβ_１基因转录和蛋白表达。     

上皮-间质转化的信号转导机制

上皮-间质转化(epithelial-mesenchymal transition,EMT)出现在各种生理和病理情况下,在胚胎发生与器官发育、肿瘤形成和转移以及纤维化过程中均有表现。TGF-β是EMT的一个重要诱导因素,其通过Smad和非Smad依赖通路对EMT的发生进行调节,对肿瘤的形成、转移和扩散起到了重要的作用。本文综述了近年来EMT信号转导机制的研究进展。     

乳腺癌原发灶成纤维细胞活化蛋白α表达与患者预后相关

目的本研究旨在探讨乳腺癌原发灶成纤维细胞活化蛋白α(FAP-α)表达与临床病理特征以及预后的关系。方法回顾性收集2000-01-01/2002-12-31期间在解放军总医院手术的130例Ⅰ-Ⅲ期乳腺癌患者的临床资料及石蜡切片,免疫组织化学染色检测乳腺癌原发灶FAP-α表达,分析FAP-α表达与转化生长因子β1(TGF-β1)表达强度的关系,并分析FAP-α表达与乳腺癌预后的关联性以及与临床病理特征的相关性。结果 FAP-α表达在肿瘤细胞和间质成纤维细胞的细胞质,FAP-α阳性纤维细胞密度与TGF-β1阳性间质细胞密度正相关。FAP-α肿瘤细胞质强度与TGF-β1阳性肿瘤细胞质表达正相关。在雌激素受体和孕激素受体均阴性患者中,FAP-α阳性纤维细胞密度是无病生存(DFS)和总生存(OS)的独立不良预后因素;FAP-α阳性肿瘤细胞质强度是DFS和OS的独立不良预后因素。结论激素受体阴性乳腺癌患者中,原发灶FAP-α高表达与不良预后相关。乳腺癌原发灶TGF-β1的表达与FAP-α的表达正相关。     

肾小管间质纤维化中成纤维细胞的转化生长因子β1及其Ⅰ型受体蛋白及基因表达检测

目的 :研究腺嘌呤致大鼠肾小管间质纤维化模型的肾组织成纤维细胞中转化生长因子 β1(TGF β1)及其Ⅰ型受体的表达。方法 :腺嘌呤灌胃法建立大鼠肾小管间质纤维化模型 ,由模型肾组织培养肾间质成纤维细胞 ,应用免疫组化、逆转录PCR分别检测TGF β1及其Ⅰ型受体蛋白及mRNA的表达。结果 :成纤维细胞TGF β1、TGF β1I型受体免疫组化阳性 ;逆转录PCR可见 2 94bp的TGF β1及 34 5bp的TGF β1的Ⅰ型受体mRNA特异扩增带。结论 :在肾小管间质纤维化进程中 ,肾间质成纤维细胞是TGF β1的一个来源 ,而且也是其效应细胞 ,从而在TGF β1的作用下出现增生和合成细胞外基质的效应。     

RNA干扰对人瘢痕疙瘩成纤维细胞TGF-β1刺激后胶原合成的影响

目的 体外构建结缔组织生长因子(CTGF)序列特异性小干扰RNA表达载体,转染导人后研究其对人瘢痕疙瘩成纤维细胞(HKFs)胶原蛋白分泌的影响.方法 体外构建CTGF序列特异性小干扰RNA质粒表达载体,Dosper脂质体转染人瘢痕疙瘩成纤维细胞后,观察加入10 ng/mL剂量的转化生长因子(TCF-β1)刺激前后胶原蛋白水平的变化.结果 转染小干扰RNA质粒后,胶原蛋白分泌水平降为正常表达的51.6%;经TGF-β1刺激后,蛋白表达仍无明显变化.结论 小干扰RNA质粒表达载体可抑制瘢痕疙瘩成纤维细胞胶原蛋白分泌,为临床上瘢痕疙瘩的基因治疗提供理论依据.     

碱性成纤维细胞生长因子对瘢痕成纤维细胞生物学行为的影响

目的探讨碱性成纤维细胞生长因子（bFGF）对瘢痕成纤维细胞生物学特性的影响。方法采用细胞培养、MTT、ELISA法、氯胺T和RT—PCR法检测bFGF在不同作用剂量下对瘢痕来源的成纤维细胞生长增殖和细胞外基质（ECM）合成的影响。结果（1）MTT检测bFGF对瘢痕成纤维细胞有明确的促增殖作用，并具有剂量相关性；（2）氯胺T法显示实验组和对照组HPr含量无显著性差异，RT—PCR法显示各组Ⅰ、Ⅲ型胶原蛋白mRNA表达水平无明显变化；说明bFGF对瘢痕成纤维细胞胶原蛋白的合成无促进作用；（3）ELISA法表明随着bFGF作用浓度的升高，FN的表达表现为增高趋势，且以100ng／ml浓度下作用最显著。结论bFGF可以促进创面愈合，但不引起瘢痕的过度形成。     

氧化苦参碱抑制高糖诱导的大鼠肾小管上皮-间充质转化及其机制研究

 目的：探讨氧化苦参碱(OM)对高糖诱导的大鼠肾小管上皮-间充质转化（EMT）的抑制作用及其可能机制。方法：体外培养大鼠近端肾小管上皮NRK52E细胞,随机分为：对照组、高糖组、高糖+OM不同浓度组和高糖+0.50 g/L OM动态观察组。采用real-time PCR和Western blotting方法检测转化生长因子β1（TGF-β1）、Smad7、α-平滑肌肌动蛋白（α-SMA）、E-钙黏素（E-cadherin）mRNA和蛋白的表达。结果：（1）与对照组相比,高糖组TGF-β1、α-SMA mRNA和蛋白表达水平均进行性增高,Smad7蛋白表达进行性降低,E-cadherin mRNA和蛋白表达进行性降低,呈时间依赖性（P＜0.05）,而Smad7 mRNA表达进行性增高（P＜0.05）;（2）与高糖组相比,高糖+ OM不同浓度组随OM剂量增加,TGF-β1、α-SMA mRNA和蛋白表达均逐渐降低,Smad7蛋白表达水平逐渐增高,E-cadherin mRNA和蛋白表达水平逐渐增高,且呈剂量依赖性（P＜0.05）,而Smad7 mRNA表达无明显差异;（3）与高糖组相比,高糖+0.50 g/L OM动态观察组TGF-β1、α-SMA mRNA和蛋白表达持续降低,Smad7蛋白表达持续增高,E-cadherin mRNA和蛋白表达持续增高（P＜0.05）,而Smad7 mRNA表达无明显差异。结论：OM可抑制高糖诱导的NRK52E细胞发生EMT,其机制可能与OM下调TGF-β1表达及上调Smad7蛋白表达,进而抑制TGF-β1/Smads信号通路的致纤维化效应有关。     

Inhibitory effect of rapamycin on proliferation of human umbilical arterial smooth muscle cells

Abstract

Objective: Rapamycin has a protective cardiovascular effect and inhibits proliferation and migration of vascular smooth muscle cells. We investigated the effects of rapamycin on proliferation of cultured human umbilical arterial smooth muscle cells (HUASMCs) by determining interleukin-6 (IL-6) levels.

Materials and methods: Adherent third-generation primary-cultured HUASMCs were used in the study, and MTT assay was used to measure the effects of different rapamycin concentrations on cell proliferation at various time points (3–96?h). RT-PCR was used to measure IL-6 mRNA expression and ELISA was used to measure IL-6 protein expression.

Results: After three passages, HUASMCs displayed >90% confluence. Inhibition of cell proliferation by rapamycin was both time and dose dependent. When the action concentration of rapamycin was 100?ng·mL^–1, the inhibitory effect was strongest after 48?h (30.25?±?2.40)%, and the follow-up study was conducted after 48?h. When the action time of rapamycin was 48?h, the inhibitory effect of 150?ng·mL^–1 at the action concentration was the strongest, and the inhibitory rate was (42.88?±?3.84)%. There was no significant difference between the inhibitory effect and the action concentration of 100?ng·mL^–1 (p>.05). Moreover, low (2?ng·mL^–1), moderate (10?ng·mL^–1), and high (100?ng·mL^–1) rapamycin concentrations down-regulated both IL-6 mRNA and expression factor in a dose-dependent manner.

Discussion and conclusions: Rapamycin inhibits proliferation of HUASMCs in vitro and through down-regulation of IL-6 expression.     

The effect of gentamicin on human renal proximal tubular cells

Human renal proximal tubular cells were exposed to gentamicin (0, 0.1, 0.5, 1.0, 5.0, 10.0 mg/ml medium) for 3, 7, 10, and 14 days. Cells were counted and cell viability was estimated by lactate dehydrogenase release. In addition, brush border-associated (gamma-glutamyltransferase) and lysosomal (acid phosphatase, N-acetyl-beta-glucosaminidase, and sphingomyelinase) enzyme activities were measured (0.01, 1.0, 3.3 mg/ml gentamicin for 3, 7, 10 and 14 days). The number of cells did not change significantly after gentamicin treatment. Cell viability, however, significantly decreased after 3 and 7 days exposure to 5 and 10 mg/ml gentamicin. Total lactate dehydrogenase activity was significantly decreased at 7, 10, and 14 days exposure to gentamicin greater than or equal to 5.0 mg/ml. gamma-Glutamyltransferase, acid phosphatase, and sphingomyelinase were decreased at 3, 7, and 10 days exposure to gentamicin greater than or equal to 1.0 mg/ml. Continued exposure to gentamicin less than or equal to 1.0 mg/ml appeared to have little or no effect on the activity of these enzymes at 14 days. N-Acetyl-beta-glucosaminidase activity, in contrast, was elevated (120-140% control) in the gentamicin-treated (greater than or equal to 1.0 mg/ml) groups at all time periods studied. Thus, gentamicin exposure resulted in changes in some of the enzyme activities in human renal proximal tubular cell cultures, but longer exposure (14 days) to gentamicin (less than or equal to 1.0 mg/ml) resulted in a return to control levels of some activities.     

肾小管上皮细胞转分化过程中ILK的表达变化及大黄素对其的干预效应

目的:研究信号蛋白ILK在IL-1β诱导的肾小管上皮细胞-肌成纤维细胞转分化(TEMT)中的表达变化以及大黄素是否是通过抑制ILK的表达而影响IL-1β诱导的肾小管上皮细胞-肌成纤维细胞转分化.方法:以体外培养的正常大鼠肾小管上皮细胞株(NRK52E)为研究对象,分为空白对照组、大黄素对照组、IL-1β诱导组、IL-1β加大黄素组.在倒置相差显微镜下观察细胞形态变化;免疫双标法检测a-平滑肌肌动蛋白(a-SMA)和E-钙黏连素(E-cadherin)的表达;免疫单染检测ILK的表达;ELISA法测定培养细胞分泌的纤维连接蛋白(FN)含量.结果:IL-1β诱导细胞转变为明显类似成纤维细胞形态,增加a-SMA的表达[(65.5±1.7)vs(140.4±3.0),P<0.05],减少E-cadherin的表达[(82.5±1.0)vs(36.0±2.8),P<0.05),促进ILK的表达[(36.1±3.1)vs(82.4±1.2),P<0.05],促进FN的合成[(54.6±3.1)mg/Lvs(124.8±3.2)mg/L,P<0.05],加入大黄素后上述变化受到明显抑制.结论:在IL-1β诱导的TEMT中ILK的表达是明显上调的,大黄素可能通过下调ILK的表达而抑制IL-1β诱导的TEMT.     

Polarized M2c macrophages have a promoting effect on the epithelial-to-mesenchymal transition of human renal tubular epithelial cells

This study planned to explore the effects of M2c macrophages on epithelial-to-mesenchymal transition (EMT) of human renal proximal tubular epithelial cells (HK-2). Human monocytic leukaemia cells were induced by TPA and IL-10 to differentiate M2c macrophages. Subsequently HK-2 cells were co-cultured with the M2c macrophages in Transwell chamber. After 48?h of co-culturing the HK-2 cells were detected in the mRNA and protein expression of E-cadherin, α-SMA and vimentin with RT-PCR, immunofluorescence and Western blot respectively. Besides, the migration ability of the HK-2 cells was estimated with Transwell migration assay. ANOVA was used to compare the difference between groups and Student's t-test to conduct multiple comparisons of two groups. P?<?0.05 was considered statistically significant. The results showed that the mRNA and protein expression of α-SMA and vimentin of the HK-2 cells were increased but the E-cadherin decreased significantly after 48?h co-culturing with the M2c macrophages (P?<?0.05 or P?<?0.01). And the migration ability of HK-2 cells were also increased significantly (P?<?0.05). It may be concluded that polarized M2c macrophages may have a promoting effect on the EMT of HK-2 cells.     

Advanced glycation end products induce tubular epithelial-myofibroblast transition through the RAGE-ERK1/2 MAP kinase signaling pathway

Advanced glycation end products (AGEs) have been shown to play a role in tubular epithelial-myofibroblast transdifferentiation (TEMT) in diabetic nephropathy, but the intracellular signaling pathway remains unknown. We report here that AGEs signal through the receptor for AGEs (RAGE) to induce TEMT, as determined by de novo expression of a mesenchymal marker (alpha-smooth muscle actin, alpha-SMA) and loss of epithelial marker (E-cadherin), directly through the MEK1-ERK1/2 MAP kinase pathway, which is TGF-beta independent. This is supported by the following findings: AGEs induced de novo alpha-SMA mRNA expression as early as 2 hours followed by a loss of E-cadherin before TGF-beta mRNA expression at 24 hours and occurred in the absence of TGF-beta and AGE-induced activation of ERK1/2 MAP kinase at 15 minutes and TEMT at 24 hours were completely blocked by a neutralizing RAGE antibody, a soluble RAGE receptor, an ERK1/2 MAP kinase inhibitor (PD98059), and DN-MEK1, but not by a neutralizing TGF-beta antibody. Thus, this study demonstrates that AGEs activate the RAGE-ERK1/2 MAP kinase pathway to mediate the early TEMT process. The findings from this study suggest that targeting the RAGE or the ERK MAP kinase pathway may provide new therapeutic strategies for diabetic nephropathy and shed new light on the pathogenesis of diabetic nephropathy.     

Effects of rapamycin on the epithelial-to-mesenchymal transition of human peritoneal mesothelial cells

The preservation of the peritoneal membrane is crucial for long-term survival in peritoneal dialysis. Epithelial-to-mesenchymal transition (EMT) is a process demonstrated in mesothelial cells (MC), responsible for negative peritoneal changes and directly related to PD. EMT enables neovascularization and fibrogenic capabilities in MC. Vascular endothelial growth factor (VEGF) is the mediator for neo-vascularization. Rapamycin is a potent immunosuppressor with antifibrotic action in renal allografts and has a demonstrated anti-VEGF effect. We performed this study with the hypothesis that rapamycin may regulate the EMT of MC. MC from human omentum were cultured. When mesothelial cells reached confluence, some of them were stimulated with r-TGF-beta (1 ng/mL) to induce EMT, co-administered with rapamycin (0.2, 2, 4, 20 and 40 nM). Other groups of cells received similar doses of rapamycin or r-TGF-beta, separately. Cells were analyzed at 6, 24, 48 hours and 7 days. As markers of EMT we included alfa -SMA, E-cadherin and snail nuclear factor by quantitative RT-PCR. EMT markers and regulators demonstrated the following changes with rapamycin: E-cadherin (a protective gene for EMT) increased 2.5-fold relative to controls under 40 nM, at 24h. Importantly, rapamycin inhibited snail expression induced by TGF-beta at 6h, whereas TGF-beta increased snail 10-fold. At day 7, rapamycin showed no anti-EMT properties. An important decrease in alfa -SMA expression by MC after rapamycin addition was observed. In conclusion, rapamycin shows a mild protective effect on EMT, as it increases E-cadherin and decreases alfa -SMA expression. Consequently, rapamycin might partially regulate the epithelial-to-mesenchymal transition of mesothelial cells.     

Inhibitory effect of angiotensin on renal sodium reabsorption

Zusammenfassung Am isolierten Frosch-Sartorius wurde die isometrische Spannungsentwicklung und die Konzentration an Phosphorylkreatin (PKr) in isotonischer KCl-Lösung in Funktion der Zeit gemessen. Dabei sollte die Ursache für das spontane Einsetzen der Erschlaffung und der Regeneration der Bestände an PKr während der Dauerdepolarisation aufgeklärt werden.Vorbehandlung des Muskels in Ringer-Lösung mit 4,5 mM Ca⁺⁺ (statt normal 1,8 mM) unterdrückte die schnelle Phase der KCl-Kontraktur und führte zur Verlängerung der Kontrakturdauer. Der Wiederanstieg der Konzentration an PKr vollzog sich dabei langsamer als in KCl-Lösung mit normalem Ca⁺⁺-Gehalt.Kühlung des Muskels von 20° C auf 0° C bewirkte eine auffällige Erschlaffungs-verzögerung in isotonischer KCl-Lösung bei gleichzeitiger Hemmung der Regeneration der Bestände an PKr.In Gegenwart bekannter in vitro-Inhibitoren der Ca⁺⁺-Aufnahme in die Vesikel des sarkoplasmatischen Reticulums (wie SCN^–, Thymol und Coffein) kam es zu einer Verstärkung der KCl-Kontraktur hinsichtlich Höhe und Dauer sowie zur Ausbildung eindeutiger Verkürzungsrückstände. Die Regeneration der Bestände an PKr verlief dabei stark verzögert und war bei gleichzeitiger Anwesenheit von SCN^– und Thymol vollständig blockiert.Die Untersuchungen zeigen, daß bei funktioneller Ausschaltung der Oberflächenmembran durch K⁺-Depolarisation das Einsetzen der Erschlaffung und der Regeneration der Bestände an PKr abhängt von der Ca⁺⁺-Rückbindung in die Vesikel des sarkoplasmatischen Reticulums. Der Prozeß der Erschlaffung würde demnach kontrolliert durch die Funktion intracellulärer Membranstrukturen und nicht durch den elektrischen Zustand der Oberflächenmembran.Die Frage der Funktion einzelner Membranabschnitte sowie die Frage der morphologischen Komponenten des intracellulären Ca⁺⁺-Turnovers werden im Hinblick auf die Kompartmentierung der Muskelzelle diskutiert.Wesentliche Teile der vorliegenden Arbeit wurden von Fräulein Ch. Petzoldt der Medizinischen Fakultät Freiburg i. Br. als Dissertation vorgelegt.     

Actin filaments in human renal tubulo-interstitial fibrosis: significance for the concept of epithelial-myofibroblast transformation

Epithelial-myofibroblast transformation has been argued as playing a role in tubulo-interstitial fibrosis. To investigate this hypothesis, we examined 9 renal biopsy specimens from patients with chronic renal disease by light and electron microscopy. In all cases, electron microscopy confirmed light microscope observations in relation to tubulo-interstitial fibrosis-tubular atrophy, accumulation of extracellular matrix and of mesenchymal interstitial cells, and infiltration by inflammatory cells. Tubular epithelial cells (TECs) contained bundles of actin filaments: mostly lacking the focal densities typical of smooth-muscle myofilaments. The interstitium contained collagen and inflammatory cells. Some endothelial cells showed bundles of myofilaments. Free mesenchymal cells in the matrix were spindled and had sparse rough endoplasmic reticulum (rER), small attachment plaques, few actin filaments and no lamina. In one case, myofibroblasts (defined by abundant rER, myofilaments and fibronexuses) were present. Most of the mesenchymal cells, therefore, did not correspond to myofibroblasts, nor to classical fibroblasts because of the sparse rER and the presence of actin filaments. We therefore called these cells myoid stromal cells, regarding them as stromal mesenchymal elements showing partial activation towards a smooth-muscle phenotype. This paper demonstrates a greater phenotypic complexity of actin-containing stromal cells in the interstitium than previously appreciated, with only a minority conforming to true or fully differentiated myofibroblasts. The widespread presence of actin (as filaments or immunoreactivity) in both TECs and interstitial cells, combined with the absence of evidence of intermediate forms or of migration from epithelium into interstitium, may point to epithelium and interstitium as separate targets for actin upregulation as an alternative hypothesis to epithelial-myofibroblast transformation.     

The roles of Arkadia in renal tubular epithelial to mesenchymal transition

The ubiquitin-proteasome pathway (UPP) can regulate the stability of proteins, which is regarded as an important mechanism in controlling various biological processes. In the pathway, E3 ubiquitin ligases play critical roles in the recognition of target proteins and degradation by 26S proteasomes. Arkadia is one of the E3 ubiquitin ligases, and recent research has shown that Arkadia amplifies TGF-beta signalling through degradation of Smad7. The cellular level of Smad7 plays an important role in the regulation of Smad-mediated TGF-beta signalling during progression of organ fibrosis. Studies indicate that the level of Smad7 protein expression is decreased in progression of tubulointerstitial fibrosis. Moreover, growing evidence suggests renal tubular epithelial to mesenchymal transition (EMT) plays a key role in renal tubulointerstitial fibrosis and transforming growth factor-beta(1) (TGF-beta(1)) is the most potent inducer that is capable of initiating and completing the entire EMT course. Therefore, the activation of Smad signalling induced by TGF-beta(1) plays a key role in the mechanism of renal tubular EMT, and in this process, Arkadia may has an important influence on the mechanism above mentioned through degradation of Smad7.