Matrix Metalloproteinase-2 Knockout and Heterozygote Mice Are Protected from Hydronephrosis and Kidney Fibrosis after Unilateral Ureteral Obstruction

Fibrosis in Chronic Kidney Disease: Pathophysiology and Therapeutic Targets

Chronic kidney disease (CKD) is a slowly progressive condition characterized by decreased kidney function, tubular injury, oxidative stress, and inflammation. CKD is a leading global health burden that is asymptomatic in early stages but can ultimately cause kidney failure. Its etiology is complex and involves dysregulated signaling pathways that lead to fibrosis. Transforming growth factor (TGF)-β is a central mediator in promoting transdifferentiation of polarized renal tubular epithelial cells into mesenchymal cells, resulting in irreversible kidney injury. While current therapies are limited, the search for more effective diagnostic and treatment modalities is intensive. Although biopsy with histology is the most accurate method of diagnosis and staging, imaging techniques such as diffusion-weighted magnetic resonance imaging and shear wave elastography ultrasound are less invasive ways to stage fibrosis. Current therapies such as renin-angiotensin blockers, mineralocorticoid receptor antagonists, and sodium/glucose cotransporter 2 inhibitors aim to delay progression. Newer antifibrotic agents that suppress the downstream inflammatory mediators involved in the fibrotic process are in clinical trials, and potential therapeutic targets that interfere with TGF-β signaling are being explored. Small interfering RNAs and stem cell-based therapeutics are also being evaluated. Further research and clinical studies are necessary in order to avoid dialysis and kidney transplantation.

Matrix gla protein, a potential marker of tissue remodelling and physiological ageing of the gut in crohn's disease

BACKGROUND

The inactive dephosphorylated and uncarboxylated form of the matrix Gla protein (dp-ucMGP) has been shown to be increased in plasma of inflammatory bowel disease (IBD) patients. Our aim was to assess if the plasmatic level of dp-ucMGP could reflect disease endoscopic activity, presence of strictures and cumulative structural bowel damage in Crohn's disease (CD) patients.

METHODS

The plasmatic level of dp-ucMGP was measured in a monocentric cohort of prospectively recruited patients. The analysis was done by chemiluminescent immunoassay on blood samples collected the day of a planned ileocolonoscopy. In addition to classical clinical data (gender, age, body mass index (BMI), disease duration, current treatment), endoscopic data (disease location, Crohn's Disease Endoscopic Index of Severity (CDEIS), mucosal healing (MH), presence of 9 CD lesion types) and biological markers (faecal calprotectin and C-reactive protein (CRP)) were collected. The association between dp-ucMGP level and Lémann index was also investigated. Univariate linear regression was used to investigate the relationship between dp-ucMGP level and different parameters collected.

RESULTS

A total of 82 ileocolonoscopies and dp-ucMGP assays were performed in 75 CD patients (45 females; 37 ileocolonic, 19 ileal and 19 colonic diseases) between October 2012 and November 2019. A total of 24 patients (29.3%) showed MH. The dp-ucMGP levels were not associated with MH, CDEIS, faecal calprotectin or CRP levels. Plasmatic dp-ucMGP levels increased significantly with age (p = 0.0032), disease duration (p = 0.0033), corticosteroids use (p = 0.019) and tended to increase in patients with intestinal strictures (p = 0.086) but not with the Lémann index.

CONCLUSION

The significant increase of plasmatic dp-ucMGP levels with age, disease duration and the trend observed in patients with non-ulcerated strictures may suggest that this extracellular matrix protein could be a marker of tissue remodelling and physiological ageing of the gut.

Expression of tissue fibrosis genes in congenitally obstructed pyeloureteral junction and biomarkers of renal damage

Introduction

The aim of this study was to investigate the expression of fibrosis-related genes in obstructed ureteral tissue and determine its relationship with biomarkers of renal damage and preoperative renal scan findings.

Material and methods

In all cases, bladder urine and blood samples were collected preoperatively. They were analysed for serum cystatin C, urinary albumin, urinary beta 2 microglobulin, and urinary neutrophil gelatinase-associated lipocalin concentrations, as well as their concentrations standardised by urine creatinine. Pyeloureteral junction obstruction tissue specimens were frozen in liquid nitrogen upon harvesting. RNA was extracted from the samples using TRIzol reagent. qPCR was performed, and the relative expressions of TGFβ1, MMP1, TIMP1, PAI1, CTGF, and VEGFA in stenotic ureteral tissue were calculated. Spearman's rank correlation test was used to calculate the correlation between the relative expression of investigated genes, urine, and blood biomarkers of renal damage and preoperative renal scan findings.

Results

A total of 20 pyeloureteral junctions of 20 patients were harvested at the time of dismembered pyeloplasty. The median age of the patients at the time of the operation was 15.2 [9.07, 66.2] months. There was a significant negative correlation between urinary albumin concentration and relative TGFβ1 expression in pyeloureteral junction tissue (rho = -0.45, p = 0.047), as well as between uAlb and relative VEGFA expression (rho = -0.575, p = 0.008). No correlation with other urine biomarkers of renal damage or renal scan findings was found.

Conclusions

Expression of fibrosis-related genes in the obstructive tissue of the pyeloureteral junction have no direct correlation with biomarkers of renal damage.

Knockout of Matrix Metalloproteinase 2 Opposes Hypertension- and Diabetes-induced Nephropathy

ABSTRACT

The progression of chronic kidney disease results from the accumulation of extracellular matrix leading to end-stage renal disease. We previously demonstrated that a broad-spectrum matrix metalloproteinase (MMP) inhibitor reduced renal injury in rat models of hypertension and diabetes. However, the isoforms and mechanisms involved are unclear. This study examined the role of MMP2 during the development of proteinuria and renal injury after induction of hypertension or diabetes in Dahl salt-sensitive (SS) and MMP2 knockout (KO) rats. Mean arterial pressure rose from 115 ± 2 to 145 ± 2 mm Hg and 116 ± 1 to 152 ± 3 mm Hg in MMP2 KO and SS rats fed a high-salt (8% NaCl) diet for 3 weeks. The degree of proteinuria, glomerular injury, renal fibrosis, and podocyte loss was lower in MMP2 KO rats than in SS rats. Blood glucose and HbA1c levels, and mean arterial pressure rose to the same extent in streptozotocin-treated SS and MMP2 KO rats. However, the degree of proteinuria, glomerulosclerosis, renal fibrosis, renal hypertrophy, glomerular permeability to albumin, and the renal expression of MMP2 and TGFβ1 were significantly reduced in MMP2 KO rats. Glomerular filtration rate fell by 33% after 12 weeks of diabetes in streptozotocin-treated SS rats compared with time-control rats, but glomerular filtration rate only fell by 12% in MMP2 KO rats. These results indicate that activation of MMP2 plays an essential role in the pathogenesis of hypertensive and diabetic nephropathy and suggests that an MMP2 inhibitor might slow the progression of chronic kidney disease.

Therapeutic mechanism of baicalein in peritoneal dialysis-associated peritoneal fibrosis based on network pharmacology and experimental validation

Baicalein (5,6,7-trihydroxyflavone) is a traditional Chinese medicine with multiple pharmacological and biological activities including anti-inflammatory and anti-fibrotic effects. However, whether baicalein has a therapeutic impact on peritoneal fibrosis has not been reported yet. In the present study, network pharmacology and molecular docking approaches were performed to evaluate the role and the potential mechanisms of baicalein in attenuating peritoneal dialysis-associated peritoneal fibrosis. The results were validated in both animal models and the cultured human mesothelial cell line. Nine intersection genes among baicalein targets and the human peritoneum RNA-seq dataset including four encapsulating peritoneal sclerosis samples and four controls were predicted by network analysis. Among them, MMP2, BAX, ADORA3, HIF1A, PIM1, CA12, and ALOX5 exhibited higher expression in the peritoneum with encapsulating peritoneal sclerosis compared with those in the control, which might be crucial targets of baicalein against peritoneal fibrosis. Furthermore, KEGG and GO enrichment analyses suggested that baicalein played an anti-peritoneal fibrosis role through the regulating cell proliferation, inflammatory response, and AGE-RAGE signaling pathway. Moreover, molecular docking analysis revealed a strong potential binding between baicalein and MMP2, which was consistent with the predictive results. Importantly, using a mouse model of peritoneal fibrosis by intraperitoneally injecting 4.25% glucose dialysate, we found that baicalein treatment significantly attenuated peritoneal fibrosis, as evident by decreased collagen deposition, protein expression of α-SMA and fibronectin, and peritoneal thickness, at least, by reducing the expression of MMP2, suggesting that baicalein may have therapeutic potential in suppressing peritoneal dialysis-related fibrosis.

Role of MMP-2 and CD147 in kidney fibrosis

Matrix metalloproteinase-2 (MMP-2) and cluster of differentiation 147 (CD147) both play important roles in the development of kidney fibrosis, and CD147 can induce the production and activation of MMP-2. In the early stage of kidney fibrosis, MMP-2 promotes extracellular matrix (ECM) production and accelerates the development of kidney fibrosis, while in the advanced stage, MMP-2 activity decreases, leading to reduced ECM degradation and making it difficult to alleviate kidney fibrosis. The reason for the decrease in MMP-2 activity in the advanced stage is still unclear. On the one hand, it may be related to hypoxia and endocytosis, which lead to changes in the expression of MMP-2-related active regulatory molecules; on the other hand, it may be related to insufficient CD147 function. At present, the specific process by which CD147 is involved in the regulation of MMP-2 activity is not completely clear, and further in-depth studies are needed to clarify the roles of both factors in the pathophysiology of kidney fibrosis.

Role of matrix metalloprotease-2 and MMP-9 in experimental lung fibrosis in mice

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a diffuse parenchymal lung disease characterized by exuberant deposition of extracellular matrix (ECM) proteins in the lung interstitium, which contributes to substantial morbidity and mortality in IPF patients. Matrix metalloproteinases (MMPs) are a large family of zinc-dependent endopeptidases, many of which have been implicated in the regulation of ECM degradation in lung fibrosis. However, the roles of MMP-2 and -9 (also termed gelatinases A and B) have not yet been explored in lung fibrosis in detail.

METHODS

AdTGF-β1 was applied via orotracheal routes to the lungs of WT, MMP-2 KO, MMP-9 KO and MMP-2/-9 dKO mice on day 0 to induce lung fibrosis. Using hydroxyproline assay, FlexiVent based lung function measurement, histopathology, western blot and ELISA techniques, we analyzed MMP-2 and MMP-9 levels in BAL fluid and lung, collagen contents in lung and lung function in mice on day 14 and 21 post-treatment.

RESULT

IPF lung homogenates exhibited significantly increased levels of MMP-2 and MMP-9, relative to disease controls. Enzymatically active MMP-2 and MMP-9 was increased in lungs of mice exposed to adenoviral TGF-β1, suggesting a role for these metalloproteinases in lung fibrogenesis. However, we found that neither MMP-2 or MMP-9 nor combined MMP-2/-9 deletion had any effect on experimental lung fibrosis in mice.

CONCLUSION

Together, our data strongly suggest that both gelatinases MMP-2 and MMP-9 play only a subordinate role in experimental lung fibrosis in mice.

Evaluation of PGP 9.5, NGFR, TGFβ1, FGFR1, MMP-2, AT2R2, SHH, and TUNEL in Primary Obstructive Megaureter Tissue

Primary obstructive megaureter (POM) morphogenesis is not fully known. The aim of the study was to evaluate the appearance of different factors that might take part in the pathogenesis of POM. Megaureter tissues of 14 children were stained with hematoxylin and eosin as well as with immunohistochemistry for protein gene product 9.5, nerve growth factor receptor, transforming growth factor beta 1 (TGFβ1), fibroblast growth factor receptor 1 (FGFR1), matrix metalloproteinase 2 (MMP-2), angiotensin 2 receptor type 2, and sonic hedgehog (SHH) protein. Apoptosis was detected by terminal dUTP nick-end labeling reaction. POM tissues revealed transitional epithelium with scattered vacuolization, submucosa with inflammatory cells, and focally vacuolized and chaotically organized muscle layers. Apoptosis, appearance of MMP-2, FGFR1, and SHH prevailed, but TGFβ1 positive cell number was lower in patients. Correlation between MMP-2 in epithelium and endothelium, FGFR1 and MMP-2 in epithelium, and TGFβ1 in epithelium and connective tissue in patients was detected. POM morphopathogenesis involves an apoptotic cell death of epithelium and smooth muscle as well as tissue degradation in epithelium and connective tissue of the ureter wall. The decrease of tissue growth through diminished TGFβ1 expression and stimulation of FGFR1 and MMP-2 suggests a disbalance of tissue remodelation in the megaureter wall.

Inflammatory response and matrix metalloproteinases in chronic kidney failure: Modulation by adropin and spexin

Chronic kidney disease is a major global public health problem. The peptide hormones adropin and spexin modulate many physiological functions such as energy balance and glucose, lipid and protein metabolism. However, it is unclear whether these peptides may exert effects on renal damage, tissue remodeling, and inflammatory conditions. In view of the limited information, we aimed to investigate the effect of adropin and spexin on matrix metalloproteinase and inflammatory response genes a rat model of adenine-induced chronic kidney failure. Chronic kidney failure was induced in rats by administering adenine hemisulfate. Renal function was determined in an autoanalyzer. Histopathological modifications were assessed by H&E staining. mRNA expression levels of ALOX 15, COX 1, COX 2, IL-1β, IL-10, IL-17A, IL-18 IL-21, IL-33, KIM-1, MMP-1, MMP-2, MMP-3, MMP-7, MMP-9, MMP-13, NGAL, TGFβ1, TIMP-1, and TNFα in kidney tissue were measured by qPCR. Our results showed an increase of 24-h urine volume, serum creatinine, BUN, and urine protein levels in group with adenine-induced CKF. Adropin and spexin treatments decreased urine protein and 24-h urine volume. Renal damage, TIMP-1, IL-33, and MMP-2 increased after CKF induction, while COX 1, MMP-9, and MMP-13 levels were significantly reduced. Furthermore, KIM-1, TIMP-1, IL-33, and MMP-2 were downregulated by spexin treatment. Renal damage, NGAL, TIMP-1 IL-17A, IL-33, MMP-2, and MMP-3 decreased after adropin treatment, while MMP-13 levels were upregulated. Treatment with adropin+spexin decreased KIM-1, NGAL, TIMP-1, IL-1β, IL-17A, IL-18, IL-33, ALOX 15, COX 1, COX 2, TGFβ1, TNFα, MMP-2, MMP-3, and MMP-7, but increased MMP-13 levels. Our findings revealed that inflammatory response and MMP genes were modulated by adropin and spexin. These peptides may have protective effects on inflammation and chronic kidney damage progression.

Identification of novel therapeutic targets for contrast induced acute kidney injury (CI-AKI): alpha blockers as a therapeutic strategy for CI-AKI

Iodinated contrast is used for imaging and invasive procedures and it can cause contrast induced acute kidney injury (CI-AKI), which is the third leading hospital-acquired health problem. The purpose of the present study was to determine the effect of α-adrenergic receptor-1b (Adra1b) inhibition by using terazosin on change in kidney function, gene, and protein expression in C57BL/6J male mice, 6-8 weeks with chronic kidney disease (CKD). CKD was induced by surgical nephrectomy. Twenty eight days later, 100-µL of iodinated contrast (CI group) or saline (S group) was given via the carotid artery. Whole-transcriptome RNA-sequencing (RNA-Seq) analysis of the kidneys was performed at day 2. Mice received either 50-µL of saline ip or terazosin (2 mg/kg) in 50-µL of saline ip 1 hour before contrast administration which was continued every 12 hours until the animals were euthanized 2 and 7 days later. The kidneys were removed for gene expression, immunohistochemical analysis, and blood serum analyzed for kidney function. Differential gene expression analysis identified 21 upregulated and 436 downregulated genes (fold change >2; P < 0.05) that were common to all sample (n = 3 for both contrast and saline). We identified Adra1b using bioinformatic analysis. Mice treated with terazosin had a significant decrease in serum creatinine, urinary Kim-1 levels, HIF-1α, apoptosis, and downstream Adrab1 genes including Ece1, Edn1, pMAPK14 with increased cell proliferation. Contrast exposure upregulated Adra1b gene expression in HK-2 cells. Inhibition of Adra1b with terazosin abrogated Ece1, Edn1, and contrast-induced Fsp-1, Mmp-2, Mmp-9 expression, and caspase-3/7 activity in HK-2 cells.

Serum Matrix Metalloproteinase 7 and accelerated GFR decline in a general non-diabetic population

BACKGROUND

Age-related reduction of glomerular filtration rate (GFR) is a major contributor to the global chronic kidney disease (CKD) epidemic. We investigated whether baseline serum levels of the pro-fibrotic matrix metalloproteinase 2 (MMP2), MMP7 and their inhibitor, tissue inhibitor of metalloproteinase 1 (TIMP1), which mediates fibrosis development in aging animals, were associated with GFR decline in a general nondiabetic population.

METHODS

In the Renal Iohexol Clearance Survey (RENIS), we measured GFR using iohexol clearance in 1627 subjects aged 50-64 without self-reported diabetes, kidney or cardiovascular disease. After a median of 5.6 years, 1324 had follow-up GFR measurements. Using linear mixed models and logistic regression analyses, we evaluated the association of MMP7, MMP2 and TIMP1 with the mean GFR decline rate, risk of accelerated GFR decline (defined as subjects with the 10% steepest GFR slopes: ≥1.8 ml/min/1.73 m2/year) and incident CKD (GFR <60 ml/min/1.73 m2 and/or urinary albumin to creatinine ratio (ACR) ≥3.0 mg/mmol).

RESULTS

Higher MMP7 levels (per SD increase of MMP7) were associated with steeper GFR decline rates (-0.23 ml/min/1.73m2/year [95% confidence interval, -0.34 to -0.12]) and increased risk of accelerated GFR decline and incident CKD, (odds ratios; 1.58 (1.30-1.93) and 1.45 (1.05-2.01), respectively, in a model adjusted for age, sex, baseline GFR, ACR and cardiovascular risk factors). MMP2 and TIMP1 showed no association with GFR decline or incident CKD.

CONCLUSION

The pro-fibrotic biomarker MMP7, but not MMP2 or TIMP1, is associated with increased risk of accelerated GFR decline and incident CKD in middle-aged persons from the general population.

Urinary extracellular matrix proteins as predictors of the severity of ureteropelvic junction obstruction in children

INTRODUCTION

Ureteropelvic junction obstruction (UPJO) particularly represents a challenge in regard to management, as not all hydronephrosis (HN) represent a kidney-damaging state. Urinary biomarkers have been proposed as noninvasive tools. Extracellular matrix (ECM) proteins are associated with tissue fibrosis in the setting of UPJO and is poorly explored.

OBJECTIVE

To investigate whether urinary ECM proteins are useful to discriminate the severity of urinary obstruction on unilateral UPJO.

STUDY DESIGN

Children with unilateral UPJO were prospective enrolled. Urinary (u) matrix metalloproteinases (MMP-1,-2,-9 and TIMP-1,-2) as well as clinical characteristics were measured in the following groups: 26 children with obstructive HN at initial diagnosis and after six months of dismembered pyeloplasty; 22 children with non-obstructive HN at diagnosis and after six months of observation; 26 children without any urinary tract condition, as the control group. Results were assessed statistically using for homogenous groups, a one-way analysis of variances (ANOVA) and for nonparametric groups, Mann-Whitney test or Kruskal-Wallis test was performed. ROC curves were performed.

RESULTS

Baseline samples demonstrated a higher concentration of uMMP-1/Cr, uMMP-2/Cr, u-TIMP-1/Cr and u-TIMP-2/Cr in obstructive HN group; uMMP-9/Cr levels were higher in non-obstructive HN group and all studied biomarkers had lower concentrations for the control group. On follow-up, for the obstructive HN group, urinary concentration of uTIMP-1/Cr and uTIMP-2/Cr decreased, and uMMP-1/Cr, uMMP-2/Cr and uMMP-9/Cr increased when comparing preoperative to postoperative values. In the non-obstructive HN group, all proteins analyzed were stable after six months of observation. ROC curves analysis showed a promising diagnostic profile for the detection of obstructive HN for uTIMP-1/Cr (area under the curve -AUC-; of 0.692), uTIMP-2/Cr (AUC of 0.678) and for uMMP-2/Cr (AUC of 0.655).

DISCUSSION

The severity of kidney obstruction could correlate with the urinary ECM proteins concentration in this study. This is concordant with prior studies demonstrating that a disruption of the balance of accumulation/degradation of the ECM proteins occur on obstructive uropathy. Limitations of our study include the older age of our patients and that these markers had no influence at all on the surgical decision.

CONCLUSION

We demonstrate that obstructive HN have significantly higher uMMP-2, uTIMP-1 and uTIMP-2 concentrations. Particularly, uTIMP-2 levels were correlated to severity of obstruction and therefore, it might be a useful urinary biomarker to correctly allocate children with HN between surgical management vs follow-up. After pyeloplasty, uTIMP-1 and uTIMP-2 presented a progressive decrease postoperatively, which is also highly desirable for urinary markers.

Key metalloproteinase-mediated pathways in the kidney

Matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinases (ADAMs) belong to the metzincin family of zinc-containing multidomain molecules, and can act as soluble or membrane-bound proteases. These enzymes inactivate or activate other soluble or membrane-expressed mediator molecules, which enables them to control developmental processes, tissue remodelling, inflammatory responses and proliferative signalling pathways. The dysregulation of MMPs and ADAMs has long been recognized in acute kidney injury and in chronic kidney disease, and genetic targeting of selected MMPs and ADAMs in different mouse models of kidney disease showed that they can have detrimental and protective roles. In particular, MMP-2, MMP-7, MMP-9, ADAM10 and ADAM17 have been shown to have a mainly profibrotic effect and might therefore represent therapeutic targets. Each of these proteases has been associated with a different profibrotic pathway that involves tissue remodelling, Wnt-β-catenin signalling, stem cell factor-c-kit signalling, IL-6 trans-signalling or epidermal growth factor receptor (EGFR) signalling. Broad-spectrum metalloproteinase inhibitors have been used to treat fibrotic kidney diseases experimentally but more targeted approaches have since been developed, including inhibitory antibodies, to avoid the toxic side effects initially observed with broad-spectrum inhibitors. These advances not only provide a solid foundation for additional preclinical studies but also encourage further translation into clinical research.

You Say You Want a Resolution (of Fibrosis)

In pathological fibrosis, aberrant tissue remodeling with excess extracellular matrix leads to organ dysfunction and eventual morbidity. Diseases of fibrosis create significant global health and economic burdens and are often deadly. Although fibrosis has traditionally been thought of as an irreversible process, a growing body of evidence demonstrates that organ fibrosis can reverse in certain circumstances, especially if an underlying cause of injury can be removed. This body of evidence has uncovered more and more contributors to persistent and nonresolving tissue fibrosis. Here, we review the present knowledge on resolution of organ fibrosis and restoration of near-normal tissue architecture. We emphasize three critical areas of tissue homeostasis that are necessary for fibrosis resolution, namely, the elimination of matrix-producing cells, the clearance of excess matrix, and the regeneration of normal tissue constituents. In so doing, we also highlight how profibrotic pathways interact with one another and where there may be therapeutic opportunities to intervene and remediate pathological persistent fibrosis.

Selected Metal Matrix Metalloproteinases and Tissue Inhibitors of Metalloproteinases as Potential Biomarkers for Tubulointerstitial Fibrosis in Children with Unilateral Hydronephrosis

Renal tubulointerstitial fibrosis caused by congenital ureteropelvic junction obstruction (UPJO) may lead to the development of obstructive nephropathy (ON) and the impairment of kidney function. Hence, the identification of early biomarkers of this condition might be of assistance in therapeutic decisions. This study evaluates serum and urinary metalloproteinases MMP-1, MMP-2, and MMP-9 and tissue inhibitors of metalloproteinases TIMP-1 and TIMP-2 as potential biomarkers of ON in children with congenital unilateral hydronephrosis (HN) caused by UPJO. Forty-five (45) children with congenital HN of different grades of severity and twenty-one (21) healthy controls were enrolled in the study. Urinary and serum concentrations of MMP-1, MMP-2, MMP-9, TIMP-1 and TIMP-2 were measured using specific ELISA kits. The urinary excretions were expressed as biomarker/creatinine (Cr) ratios. To evaluate the extracellular matrix remodelling process activity, the serum and urinary MMP-1, -2, -9/TIMP-1, -2 ratios were also calculated. In comparison with the controls, patients with HN, independent of the grade, showed significantly increased median serum MMP-9, TIMP-1, and TIMP-2, median urinary MMP-9/Cr, and TIMP-2/Cr ratios. Lower median values of serum MMP-2/TIMP-1, MMP-9/TIMP-1 in patients with HN were also revealed. Additionally, higher urinary MMP-2/Cr, lower urinary MMP-2/TIMP-2, and lower serum MMP-9/TIMP-2 ratios were observed in patients with HN grades 3 and 4. Patients with ON diagnosed by renal scintigraphy had a significantly higher median serum MMP-9 concentration and lower median serum MMP-9/TIMP-1, -2 ratios in comparison with those without this condition. Patients with nonglomerular proteinuria had a significantly higher median serum TIMP-1 concentration, a higher median urinary TIMP-2/Cr ratio, and a lower serum MMP-9/TIMP-1 ratio compared to those without this symptom. The relationship between the measured biomarkers and the relative function of the obstructed kidney showed no correlations. The ROC curve analysis showed a promising diagnostic profile for the detection of ON for serum MMP-9 and the serum MMP-9/TIMP-1 and MMP-9/TIMP-2 ratios. In conclusion, the results of this study suggest that patients with HN, particularly with grades 3 and 4, are at higher risk of renal tubulointerstitial fibrosis. The noninvasive markers of this condition considered are urinary MMP-2/Cr and MMP-9/Cr, serum MMP-9, serum and urinary MMP-2, MMP-9/TIMP-1, -2. Additionally, serum MMP-9 and MMP-9/TIMP-1, -2 may become promising markers of ON.

FoxM1 inhibition ameliorates renal interstitial fibrosis by decreasing extracellular matrix and epithelial-mesenchymal transition

FoxM1 is a transcriptional regulator involved in tumor development, pulmonary fibrosis, and cardiac fibrosis. However, its role in renal interstitial fibrosis (RIF) has yet to be elucidated. We established a TGF-β1-stimulated human proximal tubular epithelial cell (HK-2) model in vitro and a unilateral ureteral obstruction (UUO)-induced rat RIF model in vivo. FoxM1 inhibition was achieved by siRNA interference in vitro and by injecting thiostrepton into UUO-induced RIF rats in vivo. The degree of renal damage and fibrosis were determined by histological assessment via hematoxylin and eosin (H&E) staining. Immunohistochemistry, western blots, and qPCR were used to determine the expression levels of FoxM1, Collagen I, E-cadherin, α-SMA, and Snail1. Our results showed that FoxM1 inhibition could ameliorate RIF and reduce the deposition of Collagen I. H&E staining revealed that renal structural damage, inflammatory cell infiltration, and ECM deposition were significantly attenuated by thiostrepton treatment in the UUO rats. Furthermore, FoxM1 downregulation significantly suppressed epithelial-to-mesenchymal transition, as evidenced by decreased protein and mRNA expression levels of α-SMA and Snail1 and a significant increase in protein and mRNA expression levels of E-cadherin. Collectively, these results suggested that FoxM1 inhibition could be a novel therapeutic strategy for the treatment of RIF.

Tyrphostin AG490 reduces inflammation and fibrosis in neonatal obstructive nephropathy

BACKGROUND

Congenital obstructive nephropathy is the main cause of end-stage renal disease in infants and children. Renal insufficiency is due to impaired growth and maturation in the developing kidney with obstruction. Congenital obstructive nephropathy leads to cytokine mediated inflammation and the development of interstitial fibrosis. The Janus kinase-2 (JAK-2) and Signal Transducer and Activator of Transcription'-3 (STAT3) are involved in cytokine production, inflammation, and interstitial fibrosis.

METHODS

We studied the role of JAK2/STAT3 in a model of congenital obstructive nephropathy using unilateral ureteral obstruction (UUO) in neonatal mice at the second day of life. Cytokine production, inflammation, and interstitial fibrosis were analyzed in obstructed and sham operated kidneys of neonatal mice treated with or without JAK2/STAT3 inhibitor Tyrphostin AG490. To mimic obstruction and distension, proximal tubular cells were stretched in vitro.

RESULTS

We show that STAT3 is highly activated in the developing kidney with obstruction and in proximal tubular cells following stretch. JAK2/STAT3 activation mediates cytokine release and leukocyte recruitment into neonatal kidneys after UUO. Pharmacological blockade of JAK2/STAT3 by Tyrphostin AG490 reduced inflammation, tubular apoptosis, and interstitial fibrosis. JAK2/STAT3 blockade decreased pro-inflammatory and profibrotic mediators in tubular cells.

CONCLUSION

Our findings provide evidence that JAK2/STAT3 mediates inflammation and fibrosis in the developing kidney with obstruction. Blocking JAK2/STAT3 may prove beneficial in congenital obstructive nephropathy in children.

Genetic or pharmacologic blockade of enhancer of zeste homolog 2 inhibits the progression of peritoneal fibrosis

Dysregulation of histone methyltransferase enhancer of zeste homolog 2 (EZH2) has been implicated in the pathogenesis of many cancers. However, the role of EZH2 in peritoneal fibrosis remains unknown. We investigated EZH2 expression in peritoneal dialysis (PD) patients and assessed its role in peritoneal fibrosis in cultured human peritoneal mesothelial cells (HPMCs) and murine models of peritoneal fibrosis induced by chlorhexidine gluconate (CG) or high glucose peritoneal dialysis fluid (PDF) by using 3-deazaneplanocin A (3-DZNeP), and EZH2 conditional knockout mice. An abundance of EZH2 was detected in the peritoneum of patients with PD associated peritonitis and the dialysis effluent of long-term PD patients, which was positively correlated with expression of TGF-β1, vascular endothelial growth factor, and IL-6. EZH2 was found highly expressed in the peritoneum of mice following injury by CG or PDF. In both mouse models, treatment with 3-DZNeP attenuated peritoneal fibrosis and inhibited activation of several profibrotic signaling pathways, including TGF-β1/Smad3, Notch1, epidermal growth factor receptor and Src. EZH2 inhibition also inhibited STAT3 and nuclear factor-κB phosphorylation, and reduced lymphocyte and macrophage infiltration and angiogenesis in the injured peritoneum. 3-DZNeP effectively improved high glucose PDF-associated peritoneal dysfunction by decreasing the dialysate-to-plasma ratio of blood urea nitrogen and increasing the ratio of dialysate glucose at 2 h after PDF injection to initial dialysate glucose. Moreover, delayed administration of 3-DZNeP inhibited peritoneal fibrosis progression, reversed established peritoneal fibrosis and reduced expression of tissue inhibitor of metalloproteinase 2, and matrix metalloproteinase-2 and -9. Finally, EZH2-KO mice exhibited less peritoneal fibrosis than EZH2-WT mice. In HPMCs, treatment with EZH2 siRNA or 3-DZNeP suppressed TGF-β1-induced upregulation of α-SMA and Collagen I and preserved E-cadherin. These results indicate that EZH2 is a key epigenetic regulator that promotes peritoneal fibrosis. Targeting EZH2 may have the potential to prevent and treat peritoneal fibrosis. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

AXL targeting reduces fibrosis development in experimental unilateral ureteral obstruction

The AXL receptor tyrosine kinase (RTK) is involved in partial epithelial-to-mesenchymal transition (EMT) and inflammation - both main promoters of renal fibrosis development. The study aim was to investigate the role of AXL inhibition in kidney fibrosis due to unilateral ureteral obstruction (UUO). Eight weeks old male C57BL/6 mice underwent UUO and were treated with oral AXL inhibitor bemcentinib (n = 22), Angiotensin-converting enzyme inhibitor (ACEI, n = 10), ACEI and bemcentinib (n = 10) or vehicle alone (n = 22). Mice were sacrificed after 7 or 15 days and kidney tissues were analyzed by immunohistochemistry (IHC), western blot, ELISA, Sirius Red (SR) staining, and hydroxyproline (Hyp) quantification. RNA was extracted from frozen kidney tissues and sequenced on an Illumina HiSeq4000 platform. After 15 days the ligated bemcentinib-treated kidneys showed less fibrosis compared to the ligated vehicle-treated kidneys in SR analyses and Hyp quantification. Reduced IHC staining for Vimentin (VIM) and alpha smooth muscle actin (αSMA), as well as reduced mRNA abundance of key regulators of fibrosis such as transforming growth factor (Tgfβ), matrix metalloproteinase 2 (Mmp2), Smad2, Smad4, myofibroblast activation (Aldh1a2, Crlf1), and EMT (Snai1,2, Twist), in ligated bemcentinib-treated kidneys was compatible with reduced (partial) EMT induction. Furthermore, less F4/80 positive cells, less activity of pathways related to the immune system and lower abundance of MCP1, MCP3, MCP5, and TARC in ligated bemcentinib-treated kidneys was compatible with reduction in inflammatory infiltrates by bemcentinib treatment. The AXL RTK pathway represents a promising target for pharmacologic therapy of kidney fibrosis.

Osthole Ameliorates Renal Fibrosis in Mice by Suppressing Fibroblast Activation and Epithelial-Mesenchymal Transition

Renal fibrosis is a common pathway of virtually all progressive kidney diseases. Osthole (OST, 7-Methoxy-8-(3-methylbut-2-enyl)-2-chromenone), a derivative of coumarin mainly found in plants of the Apiaceae family, has shown inhibitory effects on inflammation, oxidative stress, fibrosis and tumor progression. The present study investigated whether OST mediates its effect via suppressing fibroblast activation and epithelial-mesenchymal transition (EMT) in unilateral ureteral obstruction (UUO)-induced renal fibrosis in mice. Herein, we found that OST inhibited fibroblast activation in a dose-dependent manner by inhibiting the transforming growth factor-β1 (TGFβ1)-Smad pathway. OST also blocked fibroblast proliferation by reducing DNA synthesis and downregulating the expressions of proliferation- and cell cycle-related proteins including proliferating cell nuclear antigen (PCNA), CyclinD1 and p21 Waf1/Cip1. Meanwhile, in the murine model of renal interstitial fibrosis induced by UUO, myofibroblast activation with increased expression of α-smooth muscle actin (α-SMA) and proliferation were attenuated by OST treatment. Additionally, we provided in vivo evidence suggesting that OST repressed EMT with preserved E-cadherin and reduced Vimentin expression in obstructed kidney. UUO injury-induced upregulation of EMT-related transcription factors, Snail family transcriptional repressor-1(Snail 1) and Twist family basic helix-loop-helix (BHLH) transcription factor (Twist) as well as elevated G2/M arrest of tubular epithelial cell, were rescued by OST treatment. Further, OST treatment reversed aberrant expression of TGFβ1-Smad signaling pathway, increased level of proinflammatory cytokines and NF-kappaB (NF-κB) activation in kidneys with obstructive nephropathy. Taken together, these findings suggest that OST hinder renal fibrosis in UUO mouse mainly through inhibition of fibroblast activation and EMT.

Deubiquitinase inhibitor PR-619 reduces Smad4 expression and suppresses renal fibrosis in mice with unilateral ureteral obstruction

Deubiquitinating enzymes (DUBs) remove ubiquitin from their substrates and, together with ubiquitin ligases, play an important role in the regulation of protein expression. Although transforming growth factor (TGF)-β1-Smad signaling is a central pathway of renal fibrosis, the role of DUBs in the expression of TGF-β receptors and Smads during the development of renal fibrosis remains unknown. In this study, we investigated whether PR-619, a pan-DUB inhibitor, suppresses fibrosis in mice with unilateral ureteral obstruction (UUO) and TGF-β1-stimulated normal rat kidney (NRK)-49F cells, a rat renal fibroblast cell line. Either the vehicle (dimethyl sulfoxide) or PR-619 (100 μg) was intraperitoneally administered to mice after UUO induction once a day for 7 days. Administration of PR-619 attenuated renal fibrosis with downregulation of mesenchymal markers, extracellular matrix proteins, matrix metalloproteinases, apoptosis, macrophage infiltration, and the TGF-β1 mRNA level in UUO mice. Although type I TGF-β receptor (TGF-βRI), Smad2, Smad3, and Smad4 protein expression levels were markedly increased in mice with UUO, administration of PR-619 suppressed only Smad4 expression but not TGF-βRI, Smad2, or Smad3 expression. PR-619 also had an inhibitory effect on TGF-β1-induced α-smooth muscle actin expression and reduced Smad4 levels in NRK-49F cells. Our results indicate that PR-619 ameliorates renal fibrosis, which is accompanied by the reduction of Smad4 expression.

CERA Attenuates Kidney Fibrogenesis in the db/db Mouse by Influencing the Renal Myofibroblast Generation

Tubulointerstitial fibrosis (TIF) is a pivotal pathophysiological process in patients with diabetic nephropathy (DN). Multiple profibrotic factors and cell types, including transforming growth factor beta 1 (TGF-β1) and interstitial myofibroblasts, respectively, are responsible for the accumulation of extracellular matrix in the kidney. Matrix-producing myofibroblasts can originate from different sources and different mechanisms are involved in the activation process of the myofibroblasts in the fibrotic kidney. In this study, 16-week-old db/db mice, a model for type 2 DN, were treated for two weeks with continuous erythropoietin receptor activator (CERA), a synthetic erythropoietin variant with possible non-hematopoietic, tissue-protective effects. Non-diabetic and diabetic mice treated with placebo were used as controls. The effects of CERA on tubulointerstitial fibrosis (TIF) as well as on the generation of the matrix-producing myofibroblasts were evaluated by morphological, immunohistochemical, and molecular biological methods. The placebo-treated diabetic mice showed significant signs of beginning renal TIF (shown by picrosirius red staining; increased connective tissue growth factor (CTGF), fibronectin and collagen I deposition; upregulated KIM1 expression) together with an increased number of interstitial myofibroblasts (shown by different mesenchymal markers), while kidneys from diabetic mice treated with CERA revealed less TIF and fewer myofibroblasts. The mechanisms, in which CERA acts as an anti-fibrotic agent/drug, seem to be multifaceted: first, CERA inhibits the generation of matrix-producing myofibroblasts and second, CERA increases the ability for tissue repair. Many of these CERA effects can be explained by the finding that CERA inhibits the renal expression of the cytokine TGF-β1.

Comparison of acute kidney injury of different etiology reveals in-common mechanisms of tissue damage

Acute kidney injury (AKI) is a syndrome of reduced glomerular filtration rate and urine production caused by a number of different diseases. It is associated with renal tissue damage. This tissue damage can cause tubular atrophy and interstitial fibrosis that leads to nephron loss and progression of chronic kidney disease (CKD). This review describes the in-common mechanisms behind tissue damage in AKI caused by different underlying diseases. Comparing six high-quality microarray studies of renal gene expression after AKI in disease models (gram-negative sepsis, gram-positive sepsis, ischemia-reperfusion, malignant hypertension, rhabdomyolysis, and cisplatin toxicity) identified 5,254 differentially expressed genes in at least one of the AKI models; 66% of genes were found only in one model, showing that there are unique features to AKI depending on the underlying disease. There were in-common features in the form of four genes that were differentially expressed in all six models, 49 in at least five, and 215 were found in common between at least four models. Gene ontology enrichment analysis could be broadly categorized into the injurious processes hypoxia, oxidative stress, and inflammation, as well as the cellular outcomes of cell death and tissue remodeling in the form of epithelial-to-mesenchymal transition. Pathway analysis showed that MYC is a central connection in the network of activated genes in-common to AKI, which suggests that it may be a central regulator of renal gene expression in tissue injury during AKI. The outlining of this molecular network may be useful for understanding progression from AKI to CKD.

Protective outcomes of low-dose doxycycline on renal function of Wistar rats subjected to acute ischemia/reperfusion injury

Renal ischemia-reperfusion injury (IRI) is a major cause of acute renal failure. Doxycycline (Dc) belongs to the tetracycline-class of antibiotics with demonstrated beneficial molecular effects in the brain and heart, mainly through matrix metalloproteinases inhibition (MMP). However, Dc protection of renal function has not been demonstrated. We determined whether low doses of Dc would prevent decreases in glomerular filtration rate (GFR) and maintain tubular Na⁺ handling in Wistar rats subjected to kidney I/R. Male Wistar rats underwent bilateral kidney ischemia for 30min followed by 24h reperfusion (I/R). Doxycycline (1, 3, and 10mg/kg, i.p.) was administered 2h before surgery. Untreated I/R rats showed a 250% increase in urine volume and proteinuria, a 60% reduction in GFR, accumulation of urea-nitrogen in the blood, and a 60% decrease in the fractional Na⁺ excretion due to unbalanced Na⁺ transporter activity. Treatment with Dc 3mg/kg maintained control levels of urine volume, proteinuria, GFR, blood urea-nitrogen, fractional Na⁺ excretion, and equilibrated Na⁺ transporter activities. The Dc protection effects on renal function were associated with kidney structure preservation and prevention of TGFβ and fibronectin deposition. In vitro, total MMP activity was augmented in I/R and inhibited by 25 and 50μM Dc. In vivo, I/R augmented MMP-2 and -9 protein content without changing their activities. Doxycycline treatment downregulated total MMP activity and MMP-2 and -9 protein content. Our results suggest that treatment with low dose Dc protects from IRI, thereby preserving kidney function.

Haploinsufficiency of the Transcription Factor Ets-1 Is Renoprotective in Dahl Salt-Sensitive Rats

Studies using Dahl salt-sensitive (SS) rats identified specific quantitative trait loci that predispose animals to hypertension-associated albuminuria and kidney injury. We explored the hypothesis that kidney-specific expression of the transcription factor Ets-1, located within one of these loci on chromosome 8, mediates glomerular injury in SS hypertension. During the first week on a high-salt diet, SS rats and SS rats with only one functioning Ets-1 gene (ES rats) demonstrated similar increases in BP. However, serum creatinine concentration, albuminuria, and glomerular expression of ETS-1 and two ETS-1 targets, MCP-1 and MMP2, did not increase as substantially in ES rats as in SS rats. Mean BP subsequently increased further in SS rats and remained higher than that of ES rats for the rest of the study. After 4 weeks of high-salt intake, ES rats still showed a lower mean serum creatinine concentration and less albuminuria, as well as less histologic evidence of glomerular injury and kidney fibrosis, than SS rats did. To investigate the specific contribution of renal Ets-1, we transplanted kidneys from ES or SS rats into salt-resistant SS-Chr 13^BN/McwiCrl (SS-13BN) rats. Within 10 days on a high-salt diet, BP increased similarly in ES and SS allograft recipients, becoming significantly higher than the BP of control isograft recipients. However, mean serum creatinine concentration and albuminuria remained lower in ES allograft recipients than in SS allograft recipients at 2 weeks, and ES allografts showed less glomerular injury and interstitial fibrosis. In conclusion, reduced renal expression of ETS-1 prevented hypertension-associated kidney injury in SS rats.