microRNA与肾间质纤维化的研究进展

小分子核糖核酸（microRNA）是一类约20个核苷酸单链,在转录后水平调节基因的表达。microRNA广泛分布于人体各个组织器官内,但同时也有显著的组织特异性,不同的组织器官中miRNA的表达强度有显著差异,某些microRNAs在肾脏组织中呈特异性的高表达。肾间质纤维化是各种慢性肾脏病进展至终末期,最终导致器官功能丢失的共同的病理过程和特征。通过多年累积的研究表明,一些特定的microRNAs与肾间质纤维化的进程密切相关,在这个过程中体现出极其复杂的调控机制,发挥多方面的作用。近年来,随着对microRNA的研究进一步深入,本文就microRNAs在肾间质纤维化进程中的表达特点、作用靶点及相关调控机制的研究进展进行如下综述。     

microRNA与肾间质纤维化的研究进展

小分子核糖核酸(microRNA)是一类约20个核苷酸单链,在转录后水平调节基因的表达。microRNA广泛分布于人体各个组织器官内,但同时也有显著的组织特异性,不同的组织器官中miRNA的表达强度有显著差异,某些microRNAs在肾脏组织中呈特异性的高表达。肾间质纤维化是各种慢性肾脏病进展至终末期,最终导致器官功能丢失的共同的病理过程和特征。通过多年累积的研究表明,一些特定的microRNAs与肾间质纤维化的进程密切相关,在这个过程中体现出极其复杂的调控机制,发挥多方面的作用。近年来,随着对microRNA的研究进一步深入,本文就microRNAs在肾间质纤维化进程中的表达特点、作用靶点及相关调控机制的研究进展进行如下综述。     

Effect of Interleukin 6 Deficiency on Renal Interstitial Fibrosis

Our recent studies have shown that bone marrow-derived fibroblast precursors contribute significantly to the pathogenesis of renal fibrosis. However, the molecular mechanisms underlying the recruitment and activation of bone marrow-derived fibroblast precursors are incompletely understood. We found that interleukin 6 was induced in the kidney in a murine model of renal fibrosis induced by unilateral ureteral obstruction. Therefore, we investigated if interleukin 6 play a role in the recruitment and maturation of bone marrow-derived fibroblast precursors in the kidney during the development of renal fibrosis. Wild-type and interleukin 6 knockout mice were subjected to unilateral obstructive injury for up to two weeks. Interleukin 6 knockout mice accumulated similar number of bone marrow-derived fibroblast precursors and myofibroblasts in the kidney in response to obstructive injury compared to wild-type mice. Furthermore, IL-6 knockout mice expressed comparable α-SMA in the obstructed kidney compared to wild-type mice. Moreover, targeted disruption of Interleukin 6 did not affect gene expression of profibrotic chemokine and cytokines in the obstructed kidney. Finally, there were no significant differences in renal interstitial fibrosis or expression of extracellular matrix proteins between wild-type and interleukin 6 knockout mice following obstructive injury. Our results indicate that interleukin 6 does not play a significant role in the recruitment of bone marrow-derived fibroblast precursors and the development of renal fibrosis.     

BMP-7在抑制肾脏纤维化中的作用

肾脏纤维化过程十分复杂,受到多种因素的作用,但总体上可以归结为两方面,一方面是促进纤维化的因素,为正调节因素;另一方面是抗纤维化的因素,为负调节因素。近年来,发现了一些肾脏纤维化的内源性负调节因素,比较公认的有肝细胞生长因子、骨形态发生蛋白、核心蛋白聚糖和过氧化物酶体增殖物激活受体等。该文介绍骨形态发生蛋白-7（BMP-7）在抑制肾脏纤维化方面的研究进展。     

羟苯磺酸钙通过抑制Ⅰ型胶原表达减轻肾间质纤维化

目的:研究羟苯磺酸钙对小鼠肾间质纤维化、Ⅰ型胶原表达的影响。方法:将C57小鼠随机分为假手术组(Sham组,n=4)、肾间质纤维化模型组(UUO组,n=5)及羟苯磺酸钙治疗组(CDT组,n=4);采用单侧输尿管梗阻制备肾间质纤维化模型,CDT组给予羟苯磺酸钙灌胃、Sham组和UUO组给予双蒸水灌胃;采用HE染色、Masson染色、免疫组化、实时定量PCR以及蛋白免疫印迹观察单侧输尿管梗阻术后14 d小鼠术侧肾脏的肾间质纤维化程度和Ⅰ型胶原表达情况。结果:与Sham组比较,UUO组小鼠术后14 d术侧肾脏肾发生显著肾间质纤维化,Ⅰ型胶原表达显著增强(Ⅰ型胶原基因相对表达量:Sham组:1.00000,UUO组:114.92289,P0.0001)。与UUO组比较,CDT组小鼠术后14 d术侧肾间质纤维化程度显著减轻,Ⅰ型胶原表达显著减弱(Ⅰ型胶原基因相对表达量:UUO组:114.92289,CDT组:45.33516,P0.005)。结论:羟苯磺酸钙通过抑制小鼠肾间质Ⅰ型胶原表达从而减轻单侧输尿管结扎小鼠肾间质纤维化。     

Norcantharidin Inhibits Renal Interstitial Fibrosis by Blocking the Tubular Epithelial-Mesenchymal Transition

Epithelial–mesenchymal transition (EMT) is thought to contribute to the progression of renal tubulointerstitial fibrosis. Norcantharidin (NCTD) is a promising agent for inhibiting renal interstitial fibrosis. However, the molecular mechanisms of NCTD are unclear. In this study, a unilateral ureteral obstruction (UUO) rat model was established and treated with intraperitoneal NCTD (0.1 mg/kg/day). The UUO rats treated with NCTD showed a reduction in obstruction-induced upregulation of α-SMA and downregulation of E-cadherin in the rat kidney (P<0.05). Human renal proximal tubule cell lines (HK-2) stimulated with TGF-β₁ were treated with different concentrations of NCTD. HK-2 cells stimulated by TGF-β₁ in vitro led to downregulation of E-cadherin and increased de novo expression of α-SMA; co-treatment with NCTD attenuated all of these changes (P<0.05). NCTD reduced TGF-β₁-induced expression and phosphorylation of Smad2/3 and downregulated the expression of Snail1 (P<0.05). These results suggest that NCTD antagonizes tubular EMT by inhibiting the Smad pathway. NCTD may play a critical role in preserving the normal epithelial phenotype and modulating tubular EMT.     

参麦注射液对单侧输尿管梗阻大鼠肾间质纤维化作用的研究

目的 探讨参麦注射液在单侧输尿管梗阻(UUO)大鼠肾间质纤维化进程中的可能作用.方法 成年SD大鼠54只,随机分为假手术组、模型组和参麦注射液治疗组.假手术组仅完成开腹过程,不结扎输尿管;模型组和参麦注射液治疗组行开腹左侧输尿管结扎术,术后参麦治疗组每天腹腔注射参麦注射液3 mL/(kg·d),假手术组与模型组则每天腹腔注射等量生理盐水.分别于实验的第7、14、21天各组处死动物6只,取左肾组织进行HE染色和α-平滑肌肌动蛋白(α-SMA)免疫组化检查,并测定梗阻侧肾组织中SOD和MDA含量.结果 与模型组比较,参麦注射液治疗组肾小管间质病理改变明显减轻,肾间质α-SMA表达减少;肾组织中SOD活性增加,MDA含量下降.结论 参麦注射液可通过减少氧化应激,减少肾间质α-SMA表达而抑制肾间质纤维化进程.     

Induced Autologous Stem Cell Transplantation for Treatment of Rabbit Renal Interstitial Fibrosis

Introduction

Renal interstitial fibrosis (RIF) is a significant cause of end-stage renal failure. The goal of this study was to characterize the distribution of transplanted induced autologous stem cells in a rabbit model of renal interstitial fibrosis and evaluate its therapeutic efficacy for treatment of renal interstitial fibrosis.

Methods

A rabbit model of renal interstitial fibrosis was established. Autologous fibroblasts were cultured, induced and labeled with green fluorescent protein (GFP). These labeled stem cells were transplanted into the renal artery of model animals at 8 weeks.

Results

Eight weeks following transplantation of induced autologous stem cells, significant reductions (P < 0.05) were observed in serum creatinine (SCr) (14.8 ± 1.9 mmol/L to 10.1 ± 2.1 mmol/L) and blood urea nitrogen (BUN) (119 ± 22 µmol/L to 97 ± 13 µmol/L), indicating improvement in renal function.

Conclusions

We successfully established a rabbit model of renal interstitial fibrosis and demonstrated that transplantation of induced autologous stem cells can repair kidney damage within 8 weeks. The repair occurred by both inhibition of further development of renal interstitial fibrosis and partial reversal of pre-existing renal interstitial fibrosis. These beneficial effects lead to the development of normal tissue structure and improved renal function.     

Epigallocatechin-3-Gallate Attenuates Unilateral Ureteral Obstruction-Induced Renal Interstitial Fibrosis in Mice

The severity of tubulointerstitial fibrosis is regarded as an important determinant of renal prognosis. Therapeutic strategies targeting tubulointerstitial fibrosis have been considered to have potential in the treatment of chronic kidney disease. This study aims to evaluate the protective effects of (-)-epigallocatechin-3-gallate (EGCG), a green tea polyphenol, against renal interstitial fibrosis in mice. EGCG was administrated intraperitoneally for 14 days in a mouse model of unilateral ureteral obstruction (UUO). The results of our histological examination showed that EGCG alleviated glomerular and tubular injury and attenuated renal interstitial fibrosis in UUO mice. Furthermore, the inflammatory responses induced by UUO were inhibited, as represented by decreased macrophage infiltration and inflammatory cytokine production. Additionally, the expression of type I and III collagen in the kidney were reduced by EGCG, which indicated an inhibition of extracellular matrix accumulation. EGCG also caused an up-regulation in α-smooth muscle actin expression and a down-regulation in E-cadherin expression, indicating the inhibition of epithelial-to-mesenchymal transition. These changes were found to be in parallel with the decreased level of TGF-β1 and phosphorylated Smad. In conclusion, the present study demonstrates that EGCG could attenuate renal interstitial fibrosis in UUO mice, and this renoprotective effect might be associated with its effects of inflammatory responses alleviation and TGF-β/Smad signaling pathway inhibition.     

口服氯化汞对大鼠肾间质纤维化的作用

目的口服氯化汞(HgCl2)造成大鼠的肾间质纤维化模型并探讨相关机制。方法用不同剂量HgCl2[(A组为5mg/(kg·bw)、B组为10mg/(kg·bw)、C组为20mg/(kg·bw)]给大鼠灌胃1周,观察大鼠一般状况、肾功能和肾组织病理变化,免疫组化法观察肾组织纤维连接蛋白(FN)和α-平滑肌肌动蛋白(α-SMA)表达。结果模型大鼠体重下降,肾体比增加,肾功能损害和肾组织Hyp含量呈剂量依赖性升高,肾间质炎性细胞浸润,肾间质胶原沉积增加,肾间质FN和α-SMA表达增强,以C组病变最重。结论20mg/(kg·bw)剂量HgCl2灌胃1周可造成大鼠的肾间质纤维化病变,其部分机制在于HgCl2促使肾间质肌成纤维细胞活化和细胞外基质的生成沉积。     

单侧输尿管梗阻法制作大鼠肾间质纤维化模型的改进

目的建立改良的大鼠肾间质纤维化模型。方法用单侧输尿管结扎术建立大鼠肾纤维化模型,动态观察4周。治疗的第12、、3周末检测血肌酐、尿素氮含量等指标,观察肾功能变化;4周末采用HE染色、六胺银(periodic acid-silver methenamine,PASM)染色和丽春红染色观察肾组织病理变化。结果模型组大鼠血肌酐、尿素氮均有明显上升;模型组大鼠大部分肾小球呈玻璃样变,硬化的肾小球周围所属肾小管萎缩、基底膜增厚,部分肾小管消失;少数残存的肾小球肥大并周围肾小管扩张严重;肾间质胶原纤维增生和大量炎细胞浸润。结论该模型有明显的肾间质纤维化特征,且死亡率低,适合肾间质纤维化的实验研究。     

Overexpression of Heme Oxygenase-1 Prevents Renal Interstitial Inflammation and Fibrosis Induced by Unilateral Ureter Obstruction

Renal fibrosis plays an important role in the onset and progression of chronic kidney diseases. Many studies have demonstrated that heme oxygenase-1 (HO-1) is involved in diverse biological processes as a cytoprotective molecule, including anti-inflammatory, anti-oxidant, anti-apoptotic, antiproliferative, and immunomodulatory effects. However, the mechanisms of HO-1 prevention in renal interstitial fibrosis remain unknown. In this study, HO-1 transgenic (TG) mice were employed to investigate the effect of HO-1 on renal fibrosis using a unilateral ureter obstruction (UUO) model and to explore the potential mechanisms. We found that HO-1 was adaptively upregulated in kidneys of both TG and wild type (WT) mice after UUO. The levels of HO-1 mRNA and protein were increased in TG mice compared with WT mice under normal conditions. HO-1 expression was further enhanced after UUO and remained high during the entire experimental process. Renal interstitial fibrosis in the TG group was significantly attenuated compared with that in the WT group after UUO. Moreover, overexpression of HO-1 inhibited the loss of peritubular capillaries. In addition, UUO-induced activation and proliferation of myofibroblasts were suppressed by HO-1 overexpression. Furthermore, HO-1 restrained tubulointerstitial infiltration of macrophages and regulated the secretion of inflammatory cytokines in UUO mice. We also found that high expression of HO-1 inhibited reactivation of Wnt/β-catenin signaling, which could play a crucial role in attenuating renal fibrosis. In conclusion, these data suggest that HO-1 prevents renal tubulointerstitial fibrosis possibly by regulating the inflammatory response and Wnt/β-catenin signaling. This study provides evidence that augmentation of HO-1 levels may be a therapeutic strategy against renal interstitial fibrosis.     

Circulating TNF Receptors 1 and 2 Are Associated with the Severity of Renal Interstitial Fibrosis in IgA Nephropathy

The current study aimed to examine whether the levels of TNF receptors 1 and 2 (TNFR1 and TNFR2) in serum and urine were associated with other markers of kidney injury and renal histological findings, including TNFR expression, in IgA nephropathy (IgAN). The levels of the parameters of interest were measured by immunoassay in 106 biopsy-proven IgAN patients using samples obtained immediately before renal biopsy and in 34 healthy subjects. Renal histological findings were evaluated using immunohistochemistry. The levels of serum TNFRs were higher in IgAN patients than in healthy subjects. The levels of both TNFRs in serum or urine were strongly correlated with each other (r > 0.9). Serum TNFR levels were positively correlated with the urinary protein to creatinine ratio (UPCR) and four markers of tubular damage of interest (N-acetyl-β-D-glucosaminidase [NAG], β2 microglobulin [β2m], liver-type fatty acid-binding protein [L-FABP], and kidney injury molecule-1 [KIM-1]) and negatively correlated with estimated glomerular filtration rate (eGFR). Patients in the highest tertile of serum TNFR levels showed more severe renal interstitial fibrosis than did those in the lowest or second tertiles. The tubulointerstitial TNFR2-, but not TNFR1-, positive area was significantly correlated with the serum levels of TNFRs and eGFR. Stepwise multiple regression analysis revealed that elevated serum TNFR1 or TNFR2 levels were a significant determinant of renal interstitial fibrosis after adjusting for eGFR, UPCR, and other markers of tubular damage. In conclusion, elevated serum TNFR levels were significantly associated with the severity of renal interstitial fibrosis in IgAN patients. However, the source of TNFRs in serum and urine remains unclear.     

Endothelial Dysfunction Exacerbates Renal Interstitial Fibrosis through Enhancing Fibroblast Smad3 Linker Phosphorylation in the Mouse Obstructed Kidney

Endothelial dysfunction and enhanced transforming growth factor-β (TGF-β)/Smad3 signalling are common features of progressive renal fibrosis. This study investigated a potential link between these mechanisms. In unilateral ureteric obstruction (UUO) we observed an acute (6 hr) down-regulation of nitric oxide synthase 3 (NOS3/eNOS) levels and increased phosphorylation of the linker region of Smad3 at T179 and S208 in Smad3/JNK complexes. These events preceded Smad3 C-terminal domain phosphorylation and the induction of myofibroblast proliferation at 48 hrs. Mice deficient in NOS3 showed enhanced myofibroblast proliferation and collagen accumulation compared to wild type mice in a 7 day UUO model. This was associated with enhanced phosphorylation of Smad3 T179 and S208 by 92% and 88%, respectively, whereas Smad3-C-terminal phosphorylation was not affected. Resolvin D1 (RvD1) can suppress renal fibrosis in the UUO model, and further analysis herein showed that RvD1 protected against endothelial dysfunction and suppressed Smad3/JNK complex formation with a consequent reduction in phosphorylation of Smad3 T179 and S208 by 78% and 65%, respectively, while Smad3 C-terminal phosphorylation was unaltered. In vitro, conditioned media from mouse microvascular endothelial cells (MMEC) treated with a general inhibitor of nitric oxide synthase (L-NAME) augmented the proliferation and collagen production of renal fibroblasts (NRK49F cells) compared to control MMEC media and this was associated with increased phosphorylation of JNK and Smad3 T179 and S208, whereas Smad3-C-terminal domain phosphorylation was unaffected. The addition of RvD1 to L-NAME treated MMEC abrogated these effects of the conditioned media on renal fibroblasts. Finally, Smad3 T179/V and S208/A mutations significantly inhibit TGF-β1 induced up-regulation collagen I promoter. In conclusion, these data suggest that endothelial dysfunction can exacerbate renal interstitial fibrosis through increased fibroblast proliferation and collagen production via enhanced Smad3 linker phosphorylation.     

Adenosine A2A Receptor: A Target for Regulating Renal Interstitial Fibrosis in Obstructive Nephropathy

Renal interstitial fibrosis (RIF) is the common pathological process of chronic kidney diseases leading inevitably to renal function deterioration. RIF and its preceding epithelial-mesenchymal transition (EMT) are commonly triggered by an early occurring renal inflammation. However, an effective approach to prevent EMT and RIF is still lacking and of urgent need. Recently, the adenosine A_2A receptor (A_2AR) emerges as a novel inflammation regulator, therefore manipulation of A_2AR may suppress the EMT process and as such protect against RIF. To test this hypothesis we applied a unilateral ureteral obstruction (UUO) model of RIF on A_2AR knockout mice and their wild-type littermates, combined with the intervention of a selective A_2AR agonist, CGS 21680. On days 3, 7 and 14 post-UUO we evaluated the effects of A_2AR manipulation on the molecular pathological progresses of RIF, including the cellular component of interstitial infiltration, expression of profibrotic factors, cellular biomarkers of EMT, and collagen deposition of extracellular matrix. Our data demonstrated that activation of A_2AR significantly suppressed the deposition of collagen types I and III, reduced the infiltration of CD4+ T lymphocytes, and attenuated the expression of TGF-β1 and ROCK1, which in turn inhibited and postponed the EMT progress. Conversely, genetic inactivation of A_2AR exacerbated the aforementioned pathological processes of UUO-induced RIF. Together, activation of A_2AR effectively alleviated EMT and RIF in mice, suggesting A_2AR as a potential therapeutic target for the treatment of RIF.     

Amniotic Fluid Derived Stem Cells with a Renal Progenitor Phenotype Inhibit Interstitial Fibrosis in Renal Ischemia and Reperfusion Injury in Rats

Objectives

Mesenchymal stem cells derived from human amniotic fluid (hAFSCs) are a promising source for cellular therapy, especially for renal disorders, as a subpopulation is derived from the fetal urinary tract. The purpose of this study was to evaluate if hAFSCs with a renal progenitor phenotype demonstrate a nephroprotective effect in acute ischemia reperfusion (I/R) model and prevent late stage fibrosis.

Methods

A total of 45 male 12-wk-old Wistar rats were divided into three equal groups;: rats subjected to I/R injury and treated with Chang Medium, rats subjected to I/R injury and treated with hAFSCs and sham-operated animals. In the first part of this study, hAFSCs that highly expressed CD24, CD117, SIX2 and PAX2 were isolated and characterized. In the second part, renal I/R injury was induced in male rats and cellular treatment was performed 6 hours later via arterial injection. Functional and histological analyses were performed 24 hours, 48 hours and 2 months after treatment using serum creatinine, urine protein to creatinine ratio, inflammatory and regeneration markers and histomorphometric analysis of the kidney. Statistical analysis was performed by analysis of variance followed by the Tukey’s test for multiple comparisons or by nonparametric Kruskal-Wallis followed by Dunn. Statistical significance level was defined as p <0.05.

Results

hAFSCs treatment resulted in significantly reduced serum creatinine level at 24 hours, less tubular necrosis, less hyaline cast formation, higher proliferation index, less inflammatory cell infiltration and less myofibroblasts at 48h. The treated group had less fibrosis and proteinuria at 2 months after injury.

Conclusion

hAFSCs contain a renal progenitor cell subpopulation that has a nephroprotective effect when delivered intra-arterially in rats with renal I/R injury, and reduces interstitial fibrosis on long term follow-up.     

CD4+ Cells Regulate Fibrosis and Lymphangiogenesis in Response to Lymphatic Fluid Stasis

Introduction

Lymphedema is a chronic disorder that occurs commonly after lymph node removal for cancer treatment and is characterized by swelling, fibrosis, inflammation, and adipose deposition. Although previous histological studies have investigated inflammatory changes that occur in lymphedema, the precise cellular make up of the inflammatory infiltrate remains unknown. It is also unclear if this inflammatory response plays a causal role in the pathology of lymphedema. The purpose of this study was therefore to characterize the inflammatory response to lymphatic stasis and determine if these responses are necessary for the pathological changes that occur in lymphedema.

Methods

We used mouse-tail lymphedema and axillary lymph node dissection (ANLD) models in order to study tissue inflammatory changes. Single cell suspensions were created and analyzed using multi-color flow cytometry to identify individual cell types. We utilized antibody depletion techniques to analyze the causal role of CD4+, CD8+, and CD25+ cells in the regulation of inflammation, fibrosis, adipose deposition, and lymphangiogenesis.

Results

Lymphedema in the mouse-tail resulted in a mixed inflammatory cell response with significant increases in T-helper, T-regulatory, neutrophils, macrophages, and dendritic cell populations. Interestingly, we found that ALND resulted in significant increases in T-helper cells suggesting that these adaptive immune responses precede changes in macrophage and dendritic cell infiltration. In support of this we found that depletion of CD4+, but not CD8 or CD25+ cells, significantly decreased tail lymphedema, inflammation, fibrosis, and adipose deposition. In addition, depletion of CD4+ cells significantly increased lymphangiogenesis both in our tail model and also in an inflammatory lymphangiogenesis model.

Conclusions

Lymphedema and lymphatic stasis result in CD4+ cell inflammation and infiltration of mature T-helper cells. Loss of CD4+ but not CD8+ or CD25+ cell inflammation markedly decreases the pathological changes associated with lymphedema. In addition, CD4+ cells regulate lymphangiogenesis during wound repair and inflammatory lymphangiogenesis.