PAI-1 deficiency attenuates the fibrogenic response to ureteral obstruction

BACKGROUND: Progressive renal disease is characterized by the induction of plasminogen activator inhibitor-1 (PAI-1), suggesting that impaired activity of the renal plasmin cascade may play a role in renal fibrosis. METHODS: To test this hypothesis, the severity of renal fibrosis caused by unilateral ureteral obstruction (UUO) was compared in PAI-1 wild-type (+/+) and PAI-1 deficient (-/-) mice. The extent of interstitial inflammation and fibrosis, renal plasminogen activator and plasmin activity, and renal expression of profibrotic genes was evaluated after 3, 7, and 14 days of UUO. RESULTS: Renal PAI-1 mRNA levels increased 8- to 16-fold in the +/+ mice after UUO surgery, and PAI-1 protein was detected in kidney homogenates. Interstitial fibrosis was significantly attenuated in -/- mice compared with +/+ mice at day 7 and day 14, based on the interstitial area stained with picrosirius red and total kidney collagen content. However, neither the mean renal plasminogen activator nor plasmin activities were increased in -/- mice compared with +/+ mice. The number of interstitial macrophages were significantly lower in the -/- mice three and seven days after UUO; interstitial myofibroblasts were significantly fewer at three days. At the same time points, this altered interstitial cellularity was associated with a significant reduction in renal mRNA levels for transforming growth factor-beta and procollagens alpha 1(I) and alpha 1(III). CONCLUSIONS: These studies establish an important fibrogenic role for PAI-1 in the renal fibrogenic response. The results demonstrate that one important fibrosis-promoting function of PAI-1 is its role in the recruitment of fibrosis-inducing cells, including myofibroblasts and macrophages.     

Osteopontin regulates renal apoptosis and interstitial fibrosis in neonatal chronic unilateral ureteral obstruction

Congenital obstructive nephropathy is a major cause of renal insufficiency in children. Osteopontin (OPN) is a phosphoprotein produced by the kidney that mediates cell adhesion and migration. We investigated the role of OPN in the renal response to unilateral ureteral obstruction (UUO) in neonatal mice. OPN null mutant (-/-) and wild-type (+/+) mice were subjected to sham operation or UUO within the first 2 days of life. At 7 and 21 days of age, fibroblasts (fibroblast-specific protein (FSP)-1), myofibroblasts (alpha-smooth muscle actin (SMA)), and macrophages (F4/80) were identified by immunohistochemical staining. Apoptotic cells were detected by terminal deoxy transferase uridine triphosphate nick end-labeling technique and interstitial collagen by Masson trichrome or picrosirius red stain. Compared to sham-operated or contralateral kidneys, obstructed kidneys showed increases in all parameters by 7 days, with further increases by 21 days. After 21 days UUO, there was an increase in tubular and interstitial apoptosis in OPN -/- mice as compared to +/+ animals (P<0.05). However, FSP-1- and alpha-SMA-positive cells and collagen in the obstructed kidney were decreased in OPN -/- compared to +/+ mice (P<0.05), whereas the interstitial macrophage population did not differ between groups. We conclude that OPN plays a significant role in the recruitment and activation of interstitial fibroblasts to myofibroblasts in the progression of interstitial fibrosis in the developing hydronephrotic kidney. However, OPN also suppresses apoptosis. Future approaches to limit the progression of obstructive nephropathy in the developing kidney will require targeting of specific renal compartments.     

Rapamycin attenuates unilateral ureteral obstruction-induced renal fibrosis

Unilateral ureteral obstruction (UUO) is a well-characterized hydronephrosis model exhibiting interstitial inflammatory-cell infiltration and tubular dilatation followed by tubulointerstitial fibrosis of the obstructed kidney. Our recent report indicates that rapamycin is effective for 50% of transplant recipients with chronic allograft nephropathy. In this study, we investigate the effect of rapamycin on UUO-induced renal fibrosis. UUO or sham-operated rats were randomly assigned to rapamycin or vehicle and were killed on days 7 and 14 after UUO or sham operation. Rapamycin decreased cross-sectional and gross-morphology changes in the obstructed kidney significantly. Rapamycin markedly blunted the increase in weight of the obstructed kidney, obstructed kidney length, and the obstructed/non-obstructed kidney weight ratio (by 74.6, 42.8, and 61.6% on day 14, respectively, all P<0.01). The scores for tubular dilatation, interstitial volume, interstitial collagen deposition, and alpha-smooth muscle actin (alpha-SMA) after UUO were significantly reduced by rapamycin. Rapamycin also decreased the number of infiltrative anti-ED1-positive cells and the gene expression of transforming growth factor (TGF)-beta1 (84.8 and 80.2% on day 7) after UUO (both P<0.01). By double immunostaining and Western analysis, rapamycin blocked the TGF-beta1-induced loss of E-cadherin expression and de novo increase of the expression of alpha-SMA in a dose-dependent manner. In conclusion, rapamycin significantly attenuated tubulointerstitial damage in a UUO-induced rat model of renal fibrosis, suggesting that rapamycin may have the potential to delay the progression of tubulointerstitial renal fibrosis.     

Signaling mechanism of renal fibrosis in unilateral ureteral obstructive kidney disease in ROCK1 knockout mice

It has been shown that blockade of Rho kinase with pharmacologic inhibitors inhibits renal fibrosis. This study examined the role of Rho kinase in renal fibrosis in the unilateral ureteral obstruction (UUO) model in mice that do not express the ROCK1 gene, a critical downstream mediator of Rho GTPase. Unexpected, real-time PCR, Western blot, and immunohistochemistry demonstrated that, compared with the wild-type mice, mice with ROCK1 knockout (KO) were not protected against renal fibrosis at both the early (day 5) and late (day 10) UUO, as determined by histology and expression of both mRNA and protein levels of alpha-smooth muscle actin, collagen types I and III, and fibronectin within the diseased kidney. Then the mechanisms of loss of protective effect on renal fibrosis in ROCK1 KO mice were investigated. It is interesting that mice that lacked ROCK1 did not have altered expression of ROCK2 but significantly increased TGF-beta expression and Smad2/3 activation (phosphorylation and nuclear translocation) in the diseased kidney at day 5, which remained high at day 10 of UUO. Similarly, primary cultures of kidney fibroblasts that were obtained from both ROCK1 wild-type and KO mice showed that deletion of ROCK1 did not prevent TGF-beta-induced activation of Smad2/3 and collagen I expression. This also was observed in the presence of Rho kinase inhibitor Y-27632. Taken together, results from this study suggest that Rho/Rho kinase may not be a necessary or a central pathway for renal fibrosis in the UUO model. The interplay between the Rho/Rho kinase pathway and the Smad signaling pathway may be a key mechanism by which loss of ROCK1 does not prevent renal fibrosis in the UUO model.     

Antibody to transforming growth factor-beta ameliorates tubular apoptosis in unilateral ureteral obstruction

BACKGROUND: Unilateral ureteral obstruction (UUO) is characterized by progressive renal atrophy, renal interstitial fibrosis, an increase in renal transforming growth factor-beta (TGF-beta), and renal tubular apoptosis. The present study was undertaken to determine the effect of a monoclonal antibody to TGF-beta (1D11) in UUO. METHODS: Mechanical stretch was applied to tubular epithelial cells (NRK-52E) by a computer-assisted system. Three doses of 1D11 (either 0.5, 2, or 4 mg/rat) were administered to rats one day prior to UUO and every two days thereafter, and kidneys were harvested at day 13. Fibrosis was assessed by measuring tissue hydroxyproline and mRNA for collagen and fibronectin. Apoptosis was assessed with the terminal deoxy transferase uridine triphosphate nick end-labeling assay. TGF-beta levels were determined by bioassay. Western blot and immunostaining were used to identify proliferating cell nuclear antigen (PCNA), p53, bcl-2, and inducible nitric oxide synthase (iNOS). RESULTS: Stretch significantly induced apoptosis in NRK-52E cells, which was accompanied by an increased release of TGF-beta; 1D11 (10 microg/mL) totally inhibited stretch-induced apoptosis. Control obstructed kidney contained 20-fold higher TGF-beta as compared with its unobstructed kidney; 1D11 neutralized tissue TGF-beta of the obstructed kidney. Control obstructed kidney exhibited significantly more fibrosis and tubular apoptosis than its unobstructed counterpart, which was blunted by 1D11. In contrast, 1D11 significantly increased tubular proliferation. p53 immunostaining was localized to renal tubular nuclei of control obstructed kidney and was diminished by 1D11. In contrast, bcl-2 was up-regulated in the 1D11-treated obstructed kidney. Total NOS activity and iNOS activity of the obstructed kidney were increased by 1D11 treatment. CONCLUSION: The present study strongly suggests that an antibody to TGF-beta is a promising agent to prevent renal tubular fibrosis and apoptosis in UUO.     

Genetic or pharmacologic blockade of EGFR inhibits renal fibrosis

Although enhanced activation of the EGF receptor (EGFR) associates with the development and progression of renal fibrosis, the mechanisms linking these observations are not completely understood. Here, after unilateral ureteral obstruction (UUO), wild-type mice exhibited sustained EGFR phosphorylation in the kidney and developed renal fibrosis that was more severe than the renal fibrosis observed in waved-2 mice, which have reduced EGFR tyrosine kinase activity. Waved-2 mice also showed fewer renal tubular cells arrested at G2/M, reduced expression of α-smooth muscle actin (α-SMA), downregulation of multiple genes encoding profibrogenic cytokines, including TGF-β1, and dephosphorylation of Smad3, STAT3, and ERK1/2. Administration of the specific EGFR inhibitor gefitinib recapitulated this phenotype in wild-type mice after UUO. Furthermore, inactivation of either EGFR or STAT3 reduced UUO-induced expression of lipocalin-2, a molecule associated with the pathogenesis of CKD. In cultured renal interstitial fibroblasts, inhibition of EGFR also abrogated TGF-β1- or serum-induced phosphorylation of EGFR, STAT3, ERK1/2, and Smad3 as well as expression of α-SMA and extracelluar matrix proteins. Taken together, these data suggest that EGFR may mediate renal fibrogenesis by promoting transition of renal epithelial cells to a profibrotic phenotype, increased production of inflammatory factors, and activation of renal interstitial fibroblasts. Inhibition of EGFR may have therapeutic potential for fibrotic kidney disease.     

IN-1130, a novel transforming growth factor-beta type I receptor kinase (ALK5) inhibitor, suppresses renal fibrosis in obstructive nephropathy

The transforming growth factor-beta (TGF-beta) plays a central role in the progression of renal fibrosis. TGF-beta transduces its signal through the activin receptor-like kinase (ALK)5. IN-1130, a novel small molecule ALK5 inhibitor, inhibited the purified kinase domain of ALK5-mediated Smad3 phosphorylation with an IC(50) value of 5.3 nM. IN-1130 proved to be highly selective in a panel of 27 serine/threonine and tyrosine kinases including p38alpha mitogen-activated protein kinase. We evaluated the efficacy of IN-1130 to block renal fibrogenesis induced by unilateral ureteral obstruction (UUO) in rats. Either vehicle (saline) or IN-1130 (10 and 20 mg/kg/day) was intraperitoneally administered to UUO rats for 7 and 14 days. Phosphorylated Smad2 (pSmad2) and markers of fibrosis were analyzed in kidney tissues. In UUO control kidneys, interstitial fibrosis including tubular atrophy, loss and dilation, inflammatory cell infiltration, and fibroblast cell proliferation was prominent. These morphological changes were notably reduced by IN-1130 treatment. IN-1130 decreased levels of TGF-beta1 messenger RNA (mRNA), type I collagen mRNA, and pSmad2, compared to UUO control rats. As determined by measuring the hydroxyproline content, total kidney collagen amount was increased in UUO control kidneys, but significantly reduced by IN-1130 treatment, which was comparable to results of histochemical staining for collagen. IN-1130 also suppressed the expression of alpha-smooth muscle actin (alpha-SMA) and fibronectin in UUO kidneys. Our results show that IN-1130 suppressed the fibrogenic process of UUO, further underscoring the potential clinical benefits of IN-1130 in the treatment of renal fibrosis.     

Role of nitric oxide in renal tubular apoptosis of unilateral ureteral obstruction

BACKGROUND: The obstructed kidney in unilateral ureteral obstruction (UUO) is characterized by renal atrophy and tissue loss, which is mediated by renal tubular apoptosis. We sought to determine whether NO is involved in renal tubular apoptosis in vitro and in vivo. METHODS: Rat renal tubular epithelial cells (NRK-52E) were subjected to mechanical stretch, and apoptosis and cell size were analyzed by flow cytometry. Furthermore, we studied UUO in mice lacking the gene for inducible nitric oxide synthase (iNOS-/-) and their wild-type littermates. Tubular apoptosis and proliferation were detected by immunostaining. NOS activity and NOS expression were assessed by a citrulline assay and Western blot, respectively. RESULTS: Stretching-induced apoptosis in NRK-52E, which was reduced when NO was increased; conversely, stretch-induced apoptosis was increased when a NOS inhibitor was added to the cells. Stretched cells are larger and more apoptotic than unstretched cells. In UUO, the obstructed kidney of iNOS-/- mice exhibited more apoptotic renal tubules than the wild-type mice through 14 days of UUO. The obstructed kidney of iNOS-/- mice at day 3 showed more proliferative tubules compared with wild type. The obstructed kidney of wild-type mice exhibited higher total NOS activity until day 7 after UUO compared with iNOS-/- mice. However, the obstructed kidney of day 14 wild-type mice exhibited significantly lower iNOS activity and protein compared with the day 0 kidney. CONCLUSION: These results suggest that mechanical stretch is related to renal tubular apoptosis and that NO plays a protective role in this system in UUO.     

Macrophage infiltration and renal damage are independent of matrix metalloproteinase 12 in the obstructed kidney

Aim: To determine whether matrix metalloproteinase‐12 (MMP‐12) plays a functional role in renal interstitial macrophage accumulation, interstitial fibrosis or tubular apoptosis in the unilateral ureteric obstruction (UUO) model. Background: MMP‐12 is an enzyme that can cleave a number of extracellular matrix proteins and plays a role in macrophage‐mediated injury in experimental models of emphysema and antibody‐dependent glomerular disease. Macrophages are thought to promote renal fibrosis and tubular damage in the obstructed kidney. Furthermore, upregulation of MMP‐12 expression by infiltrating macrophages in the obstructed kidney has been described, but the potential role of MMP‐12 in renal injury induced by this non‐immune insult is unknown. Methods: Groups of eight MMP‐12 gene deficient (MMP‐12^?/?) and wild type (WT) C57BL/6J mice were killed 3, 7 or 14 days after UUO. Results: Analysis of three different lineage markers found no difference in the degree of interstitial macrophage accumulation between MMP‐12^?/? and WT UUO groups at any time point. Examination of renal fibrosis by total collagen staining, α‐SMA + myofibroblast accumulation, and TGF‐β1, PAI‐1 and collagen IV mRNA levels showed no difference between MMP‐12^?/? and WT UUO groups. Finally, tubular damage (KIM‐1 levels) and tubular apoptosis (cleaved caspase‐3) in the obstructed kidney was not affected by MMP‐12 gene deletion. Conclusion: In contrast to lung injury and antibody‐dependent glomerular injury, MMP‐12 is not required for renal interstitial macrophage accumulation, interstitial fibrosis or tubular damage in the obstructed kidney.     

染料木黄酮在减轻肾间质纤维化中的作用

目的 探讨染料木黄酮(Genistein)在减轻单侧输尿管结扎模型(UUO)诱导肾间质纤维化中的作用及可能机制.方法 将30只SD大鼠随机分为5组,A组:假手术+DMSO 1 ml/d×14 d;B组:假手术+Genistein每日20 mg/ks体重×14 d;C组:UUO+DMSO 1 ml/d×14 d;D组:UUO+Genistein 5mg/kg体重每日×14d;E组:UUO+Genistein 20mg/kg体重每日×14d.术后14d比较各组大鼠左/右肾重量和长度的比值;酶联免疫吸附实验(ELISA)法检测血清INF-y和TGFa1表达;病理观察肾小管扩张和肾间质增生的程度,免疫组织化学观察肾脏á-SMA和ED-1表达.结果 C、D、E组左/右肾重量及长度比值均明显高于A、B组,但E组左/右肾重量及长度比值、血清TGF-a1及INF-y浓度、肾小管扩张分数和肾小管容量分数、á-SMA和ED-1的表达均低于C组.结论 染料木黄酮可明显降低由单侧输尿管结扎模型所导致的肾间质纤维化的病理改变,其可能机制是染料木黄酮抑制TGF-a1及INF-y的表达,从而抑制肾小管上皮细胞向成纤维细胞转化.     

三七总皂苷对单侧输尿管梗阻大鼠肾组织BMP-7及TGF-β1/samds信号传导通路的影响

目的:观察三七总皂苷(PNS)对单侧输尿管梗阻(UUO)大鼠肾组织骨形成蛋白-7(BMP-7)及TGF-β1/Smads信号传导通路的影响。方法:将50只雄性Wistar大鼠随机分为5组:假手术组、模型组、肾康注射液组(对照组)、PNS低剂量组(低剂量组)、PNS高剂量组(高剂量组),每组10只,除假手术组,其余各组用UUO法建立肾间质纤维化动物模型,术前1d起各组给予相应浓度和剂量的药物,术后第14天处死所有大鼠,检测大鼠血肌酐(Scr)和尿素氮(BUN)变化,梗阻侧肾组织行HE染色、PAS染色和Masson染色,观察肾组织病理变化并半定量计算肾小管损伤指数(TII),免疫组化法检测BMP-7、TGF-β1、Smad2、Smad7在肾组织的表达。结果:与模型组相比,PNS和肾康注射液能明显降低UUO大鼠术后14dScr、BUN(P<0.05);对梗阻侧肾组织HE染色、PAS染色进行TII评分发现,2个试验组大鼠肾小管损伤指数显著低于模型组(P<0.01);Masson染色观察发现,2个实验组大鼠肾小管间质病变明显轻于模型组;免疫组化法染色并对其灰度值测定发现,与模型组相比,2个试验组大鼠TGF-β1、Smad2在肾组织的表达下调(P<0.01),BMP-7、Smad7在肾脏组织的表达上调(P<0.01)。结论:PNS可能通过干预BMP-7/Smads/TGF-β1信号转导通路抑制了TGF-β1信号的细胞内转导,而起到抗肾间质纤维化的作用。     

Effect of renal fibrosis after macrophage depletion in C3-deficient unilateral ureteral obstruction mice

Objective To investigate the effect and mechanism of renal fibrosis after macrophage depletion in C3-deficient unilateral ureteral obstruction mice. Methods Renal interstitial fibrosis model was established by unilateral ureteral obstruction (UUO) in male C3-deficient mice and age-matched C57BL/6 WT mice (8-12 weeks of age). Mice were randomly divided into 4 groups, including sham operation in wild type group（WT/sham）(n=18), UUO operation in wild type group（WT/UUO）(n=18), sham operation in C3-deficient group（C3KO/sham）(n=18), and UUO operation in C3-deficient group（C3KO/UUO）(n=18). The expression of complement C3 was detected by immunohistochemical staining and renal interstitial macrophages were assessed by immunofluorescence staining. Tubulointerstitial fibrosis was observed by both HE staining and Masson staining after 14 days of UUO. Collagen accumulation and score of tubulointerstitial injury were obtained. Wild type and C3-deficient UUO mice were treated by liposome clodronate in early or late stage respectively and then interstitially infiltrated macrophages and renal fibrosis were analysed. Mice were sacrificed randomly at 3,7,14 days after UUO and obstructed kidneys were collected. Macrophage phenotype was detected by double-labeling immunofluorescence with F4/80 and iNOS for the M1, F4/80 and CD206 for the M2 macrophage subpopulation. iNOS, Arg-1 and CD206 were also detected by western blot. Results C3 deficient mice exhibited attenuated renal fibrosis, reduced collagen accumulation and tubulointerstitial injury score compared with WT mice (P＜0.01). Meanwhile, macrophage depletion in early or late stage of UUO reduced renal fibrosis in WT mice, but had no effect on C3-deficient UUO mice. Decreased accumulation of M1 macrophages and expression of iNOS, increased accumulation of M2 macrophages and expression of Arg-1, CD206 were found in C3 deficient mice compared with WT mice in early stage of UUO (P＜0.01). Conclusion Renal fibrosis is not reduced after depletion of macrophages in C3 deficient UUO mice due to the altered macrophage polarization.     

Selectins mediate macrophage infiltration in obstructive nephropathy in newborn mice

BACKGROUND: Urinary tract obstruction during development leads to tubular atrophy and causes interstitial fibrosis. Macrophage infiltration into the interstitium plays a central role in this process. Selectins, a family of three adhesion molecules, are involved in leukocyte recruitment to sites of inflammation and immune activity. We investigated the role of selectins in obstructive nephropathy in newborn mice. METHODS: Triple selectin-deficient mice (EPL-/-), L-selectin deficient mice (L-/-) and wild type mice (WT) were subjected to complete unilateral ureteral obstruction (UUO) or sham operation within the first 48 hours of life, and were sacrificed 5 and 12 days later. Kidneys were removed, and sections were stained for macrophage infiltration (mAb F4/80), apoptosis (TUNEL), tubular atrophy (periodic acid-Schiff) and interstitial fibrosis (Masson trichrome). RESULTS: Selectin deficient mice showed a marked reduction in macrophage infiltration into the obstructed kidney compared to WT at day 5 and day 12 after UUO. Tubular apoptosis was strongly reduced in EPL-/- at day 5 after UUO, and in EPL-/- and L-/- at day 12 after UUO when compared to WT. The number of apoptotic tubular cells was correlated with macrophage infiltration, suggesting that macrophages stimulate tubular apoptosis in obstructive nephropathy. In addition, tubular atrophy and interstitial fibrosis were significantly diminished in EPL-/- and L-/- compared to WT at day 12 after UUO. CONCLUSION: Following UUO, selectins mediate macrophage infiltration into the obstructed kidney, which in turn may induce tubular apoptosis, tubular atrophy and interstitial fibrosis.     

虫草多糖对单侧输尿管梗阻小鼠肾小管上皮-间充质转化的影响

目的：观察虫草多糖对单侧输尿管梗阻（UUO）小鼠肾小管上皮一间充质转化（EMT）的影响。方法：建立小鼠UUO模型，虫草多糖干预7d。观察模型及治疗组在第7天时肾间质纤维化程度及肾小管α-平滑肌肌动蛋白（α—SMA）、肾小管上皮表型标记物（E—cadherin）、整合素连接激酶（integrin—linked protein kinase，Iu〈）的表达分布。结果：治疗组的肾间质纤维化程度明显改善，同时α—SMA、ILK蛋白的表达显著低于对照组（P〈0.01）。而E—cadherin的表达显著高于对照组（P〈0．01）。结论：虫草多糖可显著减轻E—cadherin的丢失和α—SMA的表达，并明显抑制ILK的表达，提示其可能通过下调ILK，抑制EMT，从而减轻肾小管间质纤维化。     

CD44 deficiency increases tubular damage but reduces renal fibrosis in obstructive nephropathy

CD44 is a glycoprotein involved in inflammation and cell-cell/cell-matrix interactions. CD44 is upregulated in the kidney upon injury; however, its role in the pathogenesis of renal damage and fibrosis remains largely unknown. The authors show that mice lacking CD44 developed more tubular damage, associated with decreased proliferation and increased apoptosis of tubular epithelial cells, but less renal fibrosis after unilateral ureteral obstruction. In addition, impaired influx of macrophages and decreased accumulation of myofibroblasts was observed in the obstructed kidney of CD44(-/-) mice compared with CD44(+/+) mice. Hepatocyte growth factor (HGF) and transforming growth factor-beta1 (TGF-beta1) exert reciprocal functions in the progression of renal diseases and interact with CD44 in vitro. For the first time, the authors establish diminished HGF-signaling, via its high affinity receptor c-Met, in the absence of CD44 in vivo. In parallel, the signaling of TGF-beta1 reflected by the relative phosphorylation and nuclear translocation of Smad-2 and Smad-3 was reduced in the obstructed kidney of CD44(-/-) mice. In conclusion, CD44 exerts protective effects on tubuli but contributes to renal fibrogenesis at least in part through enhancement of HGF and TGF-beta1 signaling pathway in obstructive nephropathy.     

单侧输尿管梗阻大鼠肾脏转化生长因子β受体亚型表达的变化

目的 探讨转化生长因子β（TGF-β）Ⅰ型受体（RⅠ）、Ⅱ型（RⅡ）受体以及下游Smad蛋白在单侧输尿管梗阻（UUO）大鼠模型肾脏中表达及意义。 方法 90只雌性Wistar大鼠随机分为正常对照组（CON组）、假手术组（SOR组）和单侧输尿管梗阻组（UUO组）,分别于术后1、3、7、14、21 d处死,检测各组大鼠肾功能;PAS与Masson染色观察大鼠肾间质病理形态改变;实时定量PCR基因芯片分析正常大鼠和肾间质纤维化大鼠肾组织TGF-βⅠ、Ⅱ、Ⅲ型受体及Smad蛋白家族表达。筛选出差异表达的受体亚型,进一步应用实时荧光定量PCR、蛋白免疫印迹法、免疫荧光法检测和验证筛选出的差异受体亚型在不同分期肾间质纤维化大鼠肾组织的分布和表达。 结果 与CON组相比,UUO组大鼠的Scr及BUN于术后3 d开始升高（P < 0.05）,第21天达峰值（P < 0.01）;UUO组术后3 d肾间质可见明显炎性细胞浸润;14 d后出现明显肾小管萎缩;21 d可见明显肾间质纤维化。UUO组肾组织TGF-βⅠ型受体ALK-5、ALK-7和TGF-βRⅡ的mRNA表达于术后3 d上升并随梗阻时间延长逐渐增加（P < 0.05）,于14 d达到峰值（均P < 0.01）;ALK-6的mRNA表达于术后3 d下降（P < 0.05）并随梗阻时间延长逐渐减少,于14 d达谷值（P < 0.01）。ALK-5、ALK-6、ALK-7和TGF-βRⅡ蛋白表达与基因表达一致。Smad2/3及磷酸化（p）-Smad2/3的蛋白表达于术后3 d上升（均P < 0.05）并随梗阻时间延长逐渐增加,于14 d达到峰值（均P < 0.01）。 结论 在肾间质纤维化进展中不同TGF-β受体亚型存在不同的变化规律并与肾间质纤维化进展密切关联。     

Renal structural and functional repair in a mouse model of reversal of ureteral obstruction

The end point of immune and nonimmune renal injury typically involves glomerular and tubulointerstitial fibrosis. Although numerous studies have focused on the events that lead to renal fibrosis, less is known about the mechanisms that promote cellular repair and tissue remodeling. Described is a model of renal injury and repair after the reversal of unilateral ureteral obstruction (UUO) in male C57bl/6J mice. Male mice (20 to 25 g) underwent 10 d of UUO with or without 1, 2, 4, or 6 wk of reversal of UUO (R-UUO). UUO resulted in cortical tubular cell atrophy and tubular dilation in conjunction with an almost complete ablation of the outer medulla. This was associated with interstitial macrophage infiltration; increased hydroxyproline content; and upregulated type I, III, IV, and V collagen expression. The volume density of kidney occupied by renal tubules that exhibited a brush border was measured as an assessment of the degree of repair after R-UUO. After 6 wk of R-UUO, there was an increase in the area of kidney occupied by repaired tubules (83.7 +/- 5.9%), compared with 10 d UUO kidneys (32.6 +/- 7.3%). This coincided with reduced macrophage numbers, decreased hydroxyproline content, and reduced collagen accumulation and interstitial matrix expansion, compared with obstructed kidneys from UUO mice. GFR in the 6-wk R-UUO kidneys was restored to 43 to 88% of the GFR in the contralateral unobstructed kidneys. This study describes the regenerative potential of the kidney after the established interstitial matrix expansion and medullary ablation associated with UUO in the adult mouse.     

Obstructive uropathy in the mouse: role of osteopontin in interstitial fibrosis and apoptosis.

BACKGROUND: Osteopontin is a macrophage adhesive protein that is expressed by renal tubules in tubulointerstitial disease. METHODS: To investigate the function of OPN, we induced tubulointerstitial disease in OPN null mutant (OPN-/-) and wild-type (OPN+/+) mice by unilateral ureteral ligation. Tissue was analyzed for macrophages (ED-1), types I and IV collagen deposition, TGF-beta expression, and for tubular and interstitial cell apoptosis. RESULTS: Obstructed kidneys from both OPN-/- and OPN+/+ mice developed hydronephrosis, tubular atrophy, interstitial inflammation and fibrosis. OPN was absent in OPN-/- kidneys but was increased in obstructed OPN+/+ kidneys. Macrophage influx, measured by computer-assisted quantitative immunostaining, was less in OPN-/- mice compared to OPN+/+ mice at day 4 (threefold, P < 0.02), day 7 (fivefold, P < 0.02), but not at day 14. Interstitial deposition of types I and IV collagen were also two- to fourfold less in obstructed OPN-/- kidneys (P < 0.02). There was also a reduction of TGF-beta mRNA expression in the interstitium at day 7 (by in situ hybridization) and a near significant 34% reduction in cortical TGF-beta activity (P = 0.06) compared to obstructed OPN+/+ kidneys at day 14. Obstructed kidneys from OPN-/- mice also had more interstitial and tubular apoptotic cells (TUNEL assay) compared to obstructed OPN+/+ mice at all time points. The ability of OPN to act as a cell survival factor was also documented by showing that the apoptosis of serum-starved NRK52E renal epithelial cells was markedly enhanced in the presence of neutralizing anti-OPN antibody. CONCLUSION: OPN mediates early interstitial macrophage influx and interstitial fibrosis in unilateral ureteral obstruction. OPN may also function as a survival factor for renal tubulointerstitial cells.