Interstitial Fibrosis In Obstructive Nephropathy Research Articles

Expression of Concern: Adenosine A2A Receptor: A Target for Regulating Renal Interstitial Fibrosis in Obstructive Nephropathy.

Expression of Concern: Adenosine A2A Receptor: A Target for Regulating Renal Interstitial Fibrosis in Obstructive Nephropathy.

Myo-Inositol Attenuates Renal Interstitial Fibrosis in Obstructive Nephropathy by Inhibiting PI3K/AKT Activation.

Emerging evidence suggests that myo-inositol (MI) has a critical role in reducing renal inflammatory processes and improving podocyte function and preventing diabetes-related renal damage. We aimed to explore the function and underlying workings of MI in renal interstitial fibrosis (RIF). Based on a mouse model, we explored the effect of MI in unilateral ureteral obstruction (UUO) and in transforming growth factor-β1 (TGF-β1)-treated HK-2 cells. Pathological changes of the kidney tissues were examined following staining of the tissues with hematoxylin, eosin, and Masson's trichrome. The mRNA quantities of fibrosis markers, fibronectin, α-smooth muscle actin (α-SMA), and collagen I, were analyzed by means of real-time polymerase chain reaction, whereas those of protein levels were assessed with Western blotting. We also determined the expression of collagen I by immunofluorescence, and the levels of phosphorylated phosphotidylinositol-3-kinase and protein kinase B (PI3K/AKT) by Western blot. In vivo, histopathological examination in the UUO mice revealed renal tubular epithelial cell necrosis, inflammatory cell infiltration, and RIF. UUO mice showed higher expression levels of collagen I, fibronectin, α-SMA, pPI3K, and pAKT compared with sham-operated mice. However, MI treatment diminished the pathological alterations of RIF in UUO mice and downregulated the expression of fibrosis markers and phosphorylated PI3K/AKT. In vitro, TGF-β1 positively influenced the propagation and differentiation of HK-2 cells and upregulated the levels of α-SMA, fibronectin, collagen I, pPI3K, and pAKT, but these became significantly reversed by MI treatment. In conclusion, MI ameliorates RIF, possibly by negatively regulating TGF-β1-induced epithelial transdifferentiation and PI3K/AKT activation.

MiR-155-5p promotes renal interstitial fibrosis in obstructive nephropathy via inhibiting SIRT1 signaling pathway

Protection against renal fibrosis is important for the management of obstructive nephropathy. We researched the roles and possible mechanism of miR-155-5p in renal interstitial fibrosis, which may provide a potential endogenous target for renal interstitial fibrosis in obstructive nephropathy. Herein, NRK-49F cells were transfected with miR-155-5p mimic, miR-155-5p inhibitor, SIRT1 plasmid and/or SIRT1 siRNA. The unilateral ureteral obstruction (UUO) model was built with male C57 black mice and administrated with SRT1720 by tail vein injection. Levels of miR-155-5p, SIRT1 and relative proteins (TGF-β1, α-SMA, Collage I and fibronectin) in NRK-49F cells or mice kidney tissues were measured with quantitative reverse transcription polymerase chain reaction or Western blot. The target gene of miR-155-5p was analyzed through TargetScan and dual-luciferase reporter assay. Mice kidney tissue was stained with Masson trichrome. It was found that miR-155-5p overexpression promoted the expressions of fibroblast related proteins expression and inhibited the SIRT1 expression in NRK-49F cells, while miR-155-5p silencing had an opposite effect. SIRT1 can bind with miR-155-5p. MiR-155-5p inhibited the level of SIRT1. Fibroblast related proteins were up-regulated by miR-155-5p and down-regulated by SIRT1 in NRK-49F cells, while the up-regulatory effect of miR-155-5p was reversed by SIRT1. MiR-155-5p expression was up-regulated and SIRT1 expression was down-regulated in the kidney tissue of UUO mice. SRT1720 attenuated the fiber deposition, up-regulated SIRT1 level and down-regulated the levels of fibroblast related proteins in UUO model mice. To conclude, miR-155-5p promotes renal interstitial fibrosis in obstructive nephropathy via inhibiting SIRT1 signaling pathway.

Inhibition of α1-adrenoceptor reduces TGF-β1-induced epithelial-to-mesenchymal transition and attenuates UUO-induced renal fibrosis in mice.

Renal fibrosis is a common pathological hallmark of chronic kidney disease (CKD). Renal sympathetic nerve activity is elevated in patients and experimental animals with CKD and contributes to renal interstitial fibrosis in obstructive nephropathy. However, the mechanisms underlying sympathetic overactivation in renal fibrosis remain unknown. Norepinephrine (NE), the main sympathetic neurotransmitter, was found to promote TGF-β1-induced epithelial-mesenchymal transition (EMT) and fibrotic gene expression in the human renal proximal epithelial cell line HK-2. Using both genetic and pharmacological approaches, we identified that NE binds Gαq-coupled α1-adrenoceptor (α1-AR) to enhance EMT of HK-2 cells by activating p38/Smad3 signaling. Inhibition of p38 diminished the NE-exaggerated EMT process and increased the fibrotic gene expression in TGF-β1-treated HK-2 cells. Moreover, the pharmacological blockade of α1-AR reduced the kidney injury and renal fibrosis in a unilateral ureteral obstruction mouse model by suppressing EMT in the kidneys. Thus, sympathetic overactivation facilitates EMT of renal epithelial cells and fibrosis via the α1-AR/p38/Smad3 signaling pathway, and α1-AR inhibition may be a promising approach toward treating renal fibrosis.

Role of bone morphogenetic protein 4 on the progression of renal interstitial fibrosis in mice model of unilateral ureteral obstruction

Objective To observe the effects of bone morphogenetic protein 4 (BMP4) on the progression of renal interstitial fibrosis in mice model of unilateral ureteral obstruction (UUO). Methods C57BL/6 mice were randomly divided into four groups: injection intra-abdominally with saline-sham-operated group (saline-sham, n=8), injection intra-abdominally with saline-UUO-operated group (saline-UUO, n=8), injection intra-abdominally with anti-BMP4-sham-operated group (anti-BMP4-sham, n=8), and injection intra-abdominally with anti-BMP4-UUO-operated group (anti-BMP4-UUO, n=8). Either saline or anti-BMP4 (200 μl/g of body weight per day) were injection intra-abdominally for 7 days after surgery. Mice were sacrificed at 7 day to evaluate the fibrosis by Masson staining. The expression of BMP4 in renal tissue of normal mice was assayed by immunofluorescence. Immunohistochemical staining was used to detect the expression of α-smooth muscle actin (α-SMA), collagen Ⅲ (COL-Ⅲ) and p-Smad3 in each group. Besides, the TNF-α mRNA and MCP-1 mRNA levels were also analyzed by fluorescent quantitative Real-time polymerase chain reaction in four groups. Results The expression of BMP4 was mainly distributed in the renal tubules of mice. The area of renal interstitial fibrosis in anti-BMP4-Sham group and saline-Sham group were (1.01±0.21)% and (0.81±0.19)%, respectively. There was no significant difference in the expression of collagen fibers in 2 Sham groups (t=0.983, P>0.05). A significantly reduced collagen deposition was observed in anti-BMP4-UUO group [(15.08±2.43)%] compared to the saline-UUO group [(21.23±3.19)%, t=3.651, P 0.05; t=0.896, P>0.05; t=0.753, P>0.05). the expression of α-SMA, COL-Ⅲ and p-Smad3 were significantly decreased in anti-BMP4-UUO group than in saline-UUO group [α-SMA: (9.11±1.03)% vs. (16.18±2.15)%, COL-Ⅲ: (7.08±0.83)% vs. (12.55±1.88)%, p-Smad3: (6.14±0.76)% vs. (11.66±1.91)%, t=2.991, P 0.05; t=0.715, P>0.05). The expression of TNF-α mRNA and MCP-1 mRNA were obviously decreased in anti-BMP4-UUO group than in saline-UUO group (t=3.117, P<0.01; t=3.762, P<0.01). Conclusion BMP4 contributes to renal interstitial fibrosis in obstructive nephropathy through activation Smad3 pathway, and inhibition of BMP4 may be a choice for preventing interstitial fibrosis. Key words: Bone morphogenetic protein 4; Ureteral obstruction, unilateral; Fibrosis, renal interstitium

Legumain, an asparaginyl endopeptidase, mediates the effect of M2 macrophages on attenuating renal interstitial fibrosis in obstructive nephropathy

Two distinct macrophage phenotypes contribute to kidney injury and repair during the progression of renal interstitial fibrosis; proinflammatory (M1) and antiinflammatory (M2) macrophages. Legumain, an asparaginyl endopeptidase of the cysteine protease family, is overexpressed in macrophages in some pathological conditions. However, the macrophage subtype and function of macrophage-derived legumain remains unclear. To resolve this we tested whether M2 macrophages contribute to the accumulation of legumain in the unilateral ureteral obstruction model. Legumain-null mice exhibited more severe fibrotic lesions after obstruction compared with wild-type control. Invitro, IL4-stimulated M2 polarization led to the overexpression and secretion of legumain. The levels of fibronectin and collagen I/III, major components of the extracellular matrix, were reduced in the conditioned medium of TGF-β1-stimulated tubular epithelial cells or fibroblasts after treatment with legumain or conditioned medium from IL4-stimulated macrophages. Administration of the legumain inhibitor RR-11a exacerbated fibrotic lesions following obstruction. Therapeutically, adoptive transfer of legumain-overexpressing macrophages or IL4-stimulated macrophages ameliorated the deposition of collagen and fibronectin induced by ureteral obstruction, either in the wild-type mice or in lgmn-/- mice. Thus, M2 macrophages overexpress and secret legumain and legumain mediates the anti-fibrotic effect of M2 macrophages in obstructive nephropathy.

SKLB023 hinders renal interstitial fibrosis in obstructive nephropathy by interfering TGF-β1/Smad3 signaling.

Renal fibrosis is the principal process underlying the progression of chronic kidney disease to end-stage renal disease. It is a relatively uniform response involving glomerulosclerosis, tubulointerstitial fibrosis and changes in renal vasculature. A considerable number of studies have confirmed that inducible nitric oxide synthase (iNOS) was highly expressed in renal interstitial fibrosis and the overexpression of iNOS played a negative role in kidney disease progression. In our previous study, SKLB023 as a novel small-molecule inhibitor of iNOS, blocked joint inflammation and cartilage destruction in arthritis. However, the pharmacological role and function of SKLB023 in renal fibrosis remained poorly understood. In the study, oral administration of SKLB023 (25 and 50 mg per kg per day) for 7 day exhibited potent anti-fibrotic effects against the model UUO using the pathological assessment of H & E and Masson's trichrome staining. SKLB023 inhibited the expression of α-SMA, col I, col IV, fibronectin and further decreased iNOS expression as well as TGF-β1/Smad3 phosphorylation in the injured kidney tissues of UUO mice. Similarly, SKLB023 suppressed in vitro features of fibrosis in TGF-β1-induced NRK-49F by the inhibition of the corresponding fibrotic protein expression. These findings confirmed that SKLB023 hindered renal interstitial fibrosis by interfering with TGF-β1/Smad3 signaling, highlighting that SKLB023 has potential in therapeutic strategies.

QiShenYiQi Attenuates Renal Interstitial Fibrosis by Blocking the Activation of β-Catenin.

Chronic kidney disease (CKD) is becoming a worldwide problem. However, current treatment options are limited. In the current study we showed that QiShenYiQi (QSYQ), a water-ethanol extract from several Chinese medicines, is a potent inhibitor of renal interstitial fibrosis. QSYQ inhibited transforming growth factor-β1 (TGF-β1)-responsive α-smooth muscle actin (α-SMA), collagen I, and fibronectin up-regulation in obstructive nephropathy and cultured cells. Administration of QSYQ also inhibited the established renal interstitial fibrosis in obstructive nephropathy. Interestingly, QSYQ selectively inhibited TGF-β1-induced β-catenin up-regulation and downstream gene transcription. Taken together, our study suggests that QSYQ selectively inhibits TGF-β1-induced β-catenin up-regulation and might have significant therapeutic potential for the treatment of renal fibrosis.

Disruption of Interleukin-17 receptor A (IL-17RA) gene in mice aggravates renal interstitial fibrosis in obstructive nephropathy

Abstract Renal fibrosis is the final outcome of obstructive nephropathy and a major cause of chronic renal failure. Renal fibrosis results from an imbalance between extracellular matrix (ECM) synthesis and degradation, which is regulated by multiple inflammatory mediators in the kidney. Recently, Interleukin-17 (IL-17) emerged as a key cytokine in lung and liver fibrosis. Although IL-17 producing cells were detected in the obstructed kidney, the role of IL-17 in renal fibrosis is unknown. We sought to define the contribution of IL-17 in renal fibrosis in obstructive nephropathy. Mice deficient in IL-17 receptor signaling (IL-17RA−/−) were assessed for renal fibrosis following unilateral ureteral obstruction (UUO), a well-characterized mouse model of obstructive nephropathy. We determined IL-17 receptor signaling is required for protection against renal fibrosis following UUO. IL-17RA−/− mice developed severe morphological injury and displayed increased deposition of collagen in the obstructed kidney compared to controls. We observed a significant decrease in the level of matrix degrading enzymes in the kidney of IL-17RA−/− mice, despite normal ECM synthesis, correlating with increased fibrosis. Overexpression of IL-17 increased the level of matrix degrading enzymes and protected mice from renal fibrosis. We also show that IL-17R signaling in tubular epithelial cells up regulated multiple genes of Kallikrein-kinin system, known to play a critical role in renal protection against kidney fibrosis. Our data clearly indicate a previously unappreciated role of IL-17 in renal protection against fibrosis. These results offer the opportunity for the development of potential therapies in the treatment of chronic kidney diseases.

Simultaneous deletion of Bax and Bak is required to prevent apoptosis and interstitial fibrosis in obstructive nephropathy.

Proximal tubular injury and apoptosis are key mediators of the development of kidney fibrosis, a hallmark of chronic kidney disease. However, the molecular mechanism by which tubular apoptotic cell death leads to kidney fibrosis is poorly understood. In the present study, we tested the roles of Bcl-2-associated X (Bax) and Bcl-2 antagonist/killer (Bak), two crucial proteins involved in intrinsic apoptotic cell death, in the progression of kidney fibrosis. Mice with proximal tubule-specific Bax deletion, systemic deletion of Bak, and dual deletion of Bax and Bak were subjected to unilateral ureteral obstruction (UUO). Dual deficiency of Bax and Bak inhibited tubular apoptosis and atrophy. Consistent with decreased tubular injury, dual ablation of Bax and Bak suppressed UUO-induced inflammation and kidney fibrosis with decreased tubular cell cycle arrest, expression of fibrogenic and inflammatory cytokines, and oxidative stress in the kidney. Bax or Bak deficiency was insufficient to prevent apoptosis and all other aforementioned malevolent effects, suggesting compensatory mediation by each other in the respective signaling pathways. These data suggest that dual ablation of Bax and Bak in the kidney is required to prevent UUO-induced tubular apoptosis and the consequent kidney inflammation and fibrosis.

Urinary Candidate Biomarker Discovery in a Rat Unilateral Ureteral Obstruction Model

Urine has the potential to become a better source of biomarkers. Urinary proteins are affected by many factors; therefore, differentiating between the variables associated with any particular pathophysiological condition in clinical samples is challenging. To circumvent these problems, simpler systems such as animal models should be used to establish a direct relationship between disease progression and urine changes. Obstructive nephropathy is one of the most significant causes of chronic kidney disease, and its predominant end‐stage change is irreversible interstitial fibrosis. To better detect a set of obstructive nephropathy candidate urinary biomarkers, a unilateral ureteral obstruction (UUO) model was used to observe tubular injury and the eventual development of renal fibrosis, as well as to identify differential urinary proteins in this process. In this study, urine samples were collected from the residuary ureter linked to the kidney 1 and 3 weeks after UUO to mimic urine from patients with obstructive nephropathy. Compared with the sham operation group, 7 and 19 significantly changed proteins were identified by LC‐MS/MS in the UUO 1 and 3 week groups, respectively. These proteins identified in rat models of UUO may serve as candidate biomarkers of renal tubular injury and interstitial fibrosis in obstructive nephropathy.

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 A2A receptor (A2AR) emerges as a novel inflammation regulator, therefore manipulation of A2AR 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 A2AR knockout mice and their wild-type littermates, combined with the intervention of a selective A2AR agonist, CGS 21680. On days 3, 7 and 14 post-UUO we evaluated the effects of A2AR 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 A2AR 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 A2AR exacerbated the aforementioned pathological processes of UUO-induced RIF. Together, activation of A2AR effectively alleviated EMT and RIF in mice, suggesting A2AR as a potential therapeutic target for the treatment of RIF.

Preventive Effects and Mechanisms of Rhein on Renal Interstitial Fibrosis in Obstructive Nephropathy

Renal interstitial fibrosis is a common outcome of a variety of chronic renal diseases. Here we evaluated the therapeutic efficacy of rhein on renal interstitial fibrosis induced by unilateral ureteral obstruction (UUO) and investigated the potential mechanisms. Mice underwent UUO, followed by orally administrated rhein (150 mg/kg/d) or control vehicle. Renal interstitial injury and the degree of fibrosis were evaluated by pathological staining and Western blot. The possible mechanisms were studied by Western blot, indirect immune-fluorescence and enzyme-linked immunosorbent assay. Our results showed that rhein therapy markedly ameliorated renal interstitial fibrotic lesions, reduced α-smooth muscle actin (α-SMA) expression, attenuated deposition of fibronectin (FN). Rhein also suppressed transforming growth factor-β1 (TGF-β1) and its type I receptor expression in obstructed kidneys. In vitro, rhein abolished the α-SMA and fibronectin expression of rat kidney interstitial fibroblasts cells (NRK-49F) induced by TGF-β1. These observations strongly suggest that rhein is a potent inhibitor of renal interstitial fibrosis, and its therapeutic mechanism is, at least in part, blocking interstitial fibroblasts cells activation.

Mice lacking the matrix metalloproteinase-9 gene reduce renal interstitial fibrosis in obstructive nephropathy

Matrix metalloproteinase-9 (MMP-9) is one of the major components of the matrix proteolytic network, and its role in the pathogenesis of renal interstitial fibrosis remains largely unknown. Here, we demonstrate that ablation of MMP-9 attenuated renal interstitial fibrotic lesions in obstructive nephropathy. Mice lacking MMP-9 were less likely to develop morphological injury, which was characterized by a reduced disruption of tubular basement membrane (TBM) and expression of fibronectin as well as deposition of total tissue collagen in the kidneys after sustained ureteral obstruction compared with their wild-type counterparts. Deficiency of MMP-9 blocked tubular epithelial-to-myofibroblast transition (EMT) but did not alter the induction of transforming growth factor (TGF)-β1 axis expression in the obstructed kidneys. In vitro, TBM, which was digested by MMP-9 instead of MMP-9 itself, induces EMT and enhances migration of transformed cells. Thus increased MMP-9 is detrimental in renal interstitial fibrogenesis through a cascade of events that leads to TBM destruction and in turn to promotion of EMT. Our findings establish a crucial and definite importance of MMP-9 in the pathogenesis of renal interstitial fibrosis at the whole-animal level.

A novel STAT3 inhibitor, S3I-201, attenuates renal interstitial fibroblast activation and interstitial fibrosis in obstructive nephropathy

Accumulation of both interstitial myofibroblasts and excessive production of extracellular matrix proteins is a common pathway contributing to chronic kidney disease. In a number of tissues, activation of STAT3 (signal transducer and activator of transcription 3) increases expression of multiple profibrotic genes. Here, we examined the effect of a STAT3 inhibitor, S3I-201, on activation of renal interstitial fibroblasts and progression of renal fibrosis. Treatment of cultured rat renal interstitial fibroblasts with S3I-201 inhibited their activation, as evidenced by dose- and time-dependent blockade of alpha-smooth muscle actin and fibronectin expression. In a mouse model of renal interstitial fibrosis induced by unilateral ureteral obstruction, STAT3 was activated, and administration of S3I-201 attenuated both this activation and extracellular matrix protein deposition following injury. S3I-201 reduced infiltration of the injured kidney by inflammatory cells and suppressed the injury-induced expression of fibronectin, alpha-smooth muscle actin, and collagen type-1 proteins, as well as the expression of multiple cytokines. Furthermore, S3I-201 inhibited proliferation and induced apoptosis preferentially in renal interstitial fibroblasts of the obstructed kidney. Thus, our results suggest that increased STAT3 activity mediates activation of renal interstitial fibroblasts and the progression of renal fibrosis. Inhibition of STAT3 signaling with S3I-201 may hold therapeutic potential for fibrotic kidney diseases.

Inhibition of histone deacetylase activity attenuates renal fibroblast activation and interstitial fibrosis in obstructive nephropathy

Activation of renal interstitial fibroblasts is critically involved in the development of tubulointerstitial fibrosis in chronic kidney diseases. In this study, we investigated the effect of trichostatin A (TSA), a specific histone deacetylase (HDAC) inhibitor, on the activation of renal interstitial fibroblasts in a rat renal interstitial fibroblast line (NRK-49F) and the development of renal fibrosis in a murine model of unilateral ureteral obstruction (UUO). alpha-Smooth muscle actin (alpha-SMA) and fibronectin, two hallmarks of fibroblast activation, were highly expressed in cultured NRK-49F cells, and their expression was inhibited in the presence of TSA. Similarly, administration of TSA suppressed the expression of alpha-SMA and fibronectin and attenuated the accumulation of renal interstitial fibroblasts in the kidney after the obstructive injury. Activation of renal interstitial fibroblasts was accompanied by phosphorylation of signal transducer and activator of transcription 3 (STAT3), and TSA treatment also abolished these responses. Furthermore, inhibition of the STAT3 pathway with AG490 inhibited expression of alpha-SMA and fibronectin in NRK-49F cells. Finally, TSA treatment inhibited tubular cell apoptosis and caspase-3 activation in the obstructive kidney. Collectively, we suggest that pharmacological HDAC inhibition may induce antifibrotic activity by inactivation of renal interstitial fibroblasts and inhibition of renal tubular cell death. STAT3 may mediate those actions of HDACs.

HSP72 attenuates renal tubular cell apoptosis and interstitial fibrosis in obstructive nephropathy

Although heat shock protein 72 kDa (HSP72) protects tubular epithelium from a variety of acute insults, its role in chronic renal injury and fibrosis is poorly characterized. In this study, we tested the hypothesis that HSP72 reduces apoptosis and epithelial-to-mesenchymal transition (EMT), important contributors to tubular cell injury in vitro and in vivo. In rats, orally administered geranylgeranylacetone (GGA), an agent that selectively induces HSP72, markedly reduced both apoptosis and cell proliferation in tubular epithelium and decreased both interstitial fibroblast accumulation and collagen I deposition after unilateral ureteric obstruction, a model of chronic renal tubulointerstitial fibrosis and dysfunction. In cultured renal NRK52E cells, exposure to TGF-beta1 induced EMT and apoptosis, major causes of renal fibrosis and tubular atrophy, respectively. Exposure to a pan-caspase inhibitor (ZVAD-FMK) prevented TGF-beta1-induced apoptosis but did not reduce EMT. In contrast, selective HSP72 expression in vitro inhibited EMT caused by TGF-beta1 as indicated by preserving the E-cadherin expression level and alpha-smooth muscle actin induction. Small interfering RNA directed against HSP72 blocked the cytoprotective effects of HSP72 overexpression on EMT in TGF-beta1-exposed cells. Taken together, our data indicate that HSP72 ameliorates renal tubulointerstitial fibrosis in obstructive nephropathy by inhibiting both renal tubular epithelial cell apoptosis and EMT.

Protective role of thrombin activatable fibrinolysis inhibitor in obstructive nephropathy-associated tubulointerstitial fibrosis.

Thrombin-activatable fibrinolysis inhibitor (TAFI) has been reported to affect wound healing and fibrotic processes, but its role in renal tubulointerstitial fibrosis remains unknown. To study its potential role, we compared TAFI-deficient and wild-type mice for the degree of renal fibrosis caused by unilateral ureteral obstruction (UUO). The grade of tubulointerstitial fibrosis, the activity of plasmin, MMP-2 and MMP-9 were evaluated on days 4 and 9 after UUO. The renal content of hydroxyproline and the activity of plasmin, MMP-2 and MMP-9 were significantly increased in kidneys with UUO from TAFI-deficient mice compared with those from wild-type mice. These differences disappeared when animals with UUO from both groups were treated with the plasmin inhibitor tranexamic acid. The renal concentrations of fibrogenic cytokines were also significantly elevated in kidneys with UUO from TAFI-deficient mice compared with those from wild-type mice. The results of this study suggest that increased renal activity of plasmin in TAFI-deficient mice causes increased renal interstitial fibrosis in obstructive nephropathy.

Glomerulotubular disconnection in neonatal mice after relief of partial ureteral obstruction

Ureteropelvic junction obstruction is a common cause of congenital obstructive nephropathy. To study the pathogenesis of nephropathy, a variable-partial, complete or a sham unilateral ureteral obstruction (UUO) was produced in mice within 2 days of birth. The obstruction was released in some animals at 7 days and kidneys harvested at 7-42 days of age for histologic and morphometric study. Renal parenchymal growth was stunted by partial UUO with the impairment proportional to the duration and severity of obstruction. Proximal tubule apoptosis and glomerulotubular disconnection led to nephron loss. Relief of partial UUO arrested glomerulotubular disconnection, resolved tubule atrophy, and interstitial fibrosis with remodeling of the renal architecture. Relief of severe UUO did not result in recovery. Compensatory growth of the contralateral kidney depended on the severity of obstruction. Our studies indicate that relief of moderate UUO will minimize nephron loss. Application of this technique to mutant mice will help develop future therapies to enhance nephron recovery.

A complex, tissue-specific role for plasmin and its regulators in modulating fibrogenic activity

it has long been known that tissue injury often leads to the infiltration of interstitial spaces with plasma, resulting in the polymerization of fibrin as a provisional matrix to support the migration of cells that mediate healing process. When all goes well, during the course of tissue repair the