A possible role for metalloproteinases in renal cyst development

Matrix Metalloproteinase-7 in Urinary Extracellular Vesicles Identifies Rapid Disease Progression in Autosomal Dominant Polycystic Kidney Disease

SIGNIFICANCE STATEMENT

There is an unmet need for biomarkers of disease progression in autosomal dominant polycystic kidney disease (ADPKD). This study investigated urinary extracellular vesicles (uEVs) as a source of such biomarkers. Proteomic analysis of uEVs identified matrix metalloproteinase 7 (MMP-7) as a biomarker predictive of rapid disease progression. In validation studies, MMP-7 was predictive in uEVs but not in whole urine, possibly because uEVs are primarily secreted by tubular epithelial cells. Indeed, single-nucleus RNA sequencing showed that MMP-7 was especially increased in proximal tubule and thick ascending limb cells, which were further characterized by a profibrotic phenotype. Together, these data suggest that MMP-7 is a biologically plausible and promising uEV biomarker for rapid disease progression in ADPKD.

BACKGROUND

In ADPKD, there is an unmet need for early markers of rapid disease progression to facilitate counseling and selection for kidney-protective therapy. Our aim was to identify markers for rapid disease progression in uEVs.

METHODS

Six paired case-control groups ( n =10-59/group) of cases with rapid disease progression and controls with stable disease were formed from two independent ADPKD cohorts, with matching by age, sex, total kidney volume, and genetic variant. Candidate uEV biomarkers were identified by mass spectrometry and further analyzed using immunoblotting and an ELISA. Single-nucleus RNA sequencing of healthy and ADPKD tissue was used to identify the cellular origin of the uEV biomarker.

RESULTS

In the discovery proteomics experiments, the protein abundance of MMP-7 was significantly higher in uEVs of patients with rapid disease progression compared with stable disease. In the validation groups, a significant >2-fold increase in uEV-MMP-7 in patients with rapid disease progression was confirmed using immunoblotting. By contrast, no significant difference in MMP-7 was found in whole urine using ELISA. Compared with healthy kidney tissue, ADPKD tissue had significantly higher MMP-7 expression in proximal tubule and thick ascending limb cells with a profibrotic phenotype.

CONCLUSIONS

Among patients with ADPKD, rapid disease progressors have higher uEV-associated MMP-7. Our findings also suggest that MMP-7 is a biologically plausible biomarker for more rapid disease progression.

Identifying Tumor Microenvironment Biomarkers in Adherent and Cystic Vestibular Schwannomas

OBJECTIVE

A subset of vestibular schwannomas (VSs), including cystic tumors, have higher postoperative morbidity because of the presence of adhesions between the tumor, facial nerve (FN), and brainstem. We identify tumor microenvironment (TME) biomarkers to better classify these tumors and predict the degree of tumor adherence.

STUDY DESIGN

Retrospective case series.

SETTING

Tertiary skull base referral center.

METHODS

Adult patients with cystic and solid VS matched in tumor size who underwent surgical resection were included. Expressions of seven biomarkers of extracellular matrix remodeling and tumor immune response were quantified via immunohistochemistry. The distribution of CD45+ immune cells was evaluated in intratumoral and perivascular compartments. The degree of tumor adherence was categorized as none, adherent to FN, or adherent to both FN and brainstem.

RESULTS

Twenty-eight patients were included. Cystic VSs were significantly more adherent than solid VSs ( p = 0.02). Patients with adherent VS had shorter duration of symptoms and were more likely to undergo subtotal resection. In solid tumors, matrix metalloproteinase (MMP)-2 expression ( p = 0.02) and CD163+ macrophage infiltration ( p = 0.007) were correlated with tumor size. Linear discriminant analyses (LDAs) demonstrated MMP-2, MMP-14, CD80, CD163, and perivascular CD45 to be individually predictive of the degree of tumor adherence (all p < 0.05), with perivascular CD45 being the best independent predictor ( p = 0.005). An LDA model including these biomarkers demonstrated 100% accurate discrimination of all three levels of tumor adherence ( p = 0.04).

CONCLUSIONS

Adherent VS have a distinct proinflammatory TME characterized by elevated MMP expression, enrichment of tumor-associated macrophages, and perivascular immune cell infiltration.

Cleavage of periostin by MMP9 protects mice from kidney cystic disease

The matrix metalloproteinase MMP9 influences cellular morphology and function, and plays important roles in organogenesis and disease. It exerts both protective and deleterious effects in renal pathology, depending upon its specific substrates. To explore new functions for MMP9 in kidney cysts formation and disease progression, we generated a mouse model by breeding juvenile cystic kidney (jck) mice with MMP9 deficient mice. Specifically, we provide evidence that MMP9 is overexpressed in cystic tissue where its enzymatic activity is increased 7-fold. MMP9 deficiency in cystic kidney worsen cystic kidney diseases by decreasing renal function, favoring cyst expansion and fibrosis. In addition, we find that periostin is a new critical substrate for MMP9 and in its absence periostin accumulates in cystic lining cells. As periostin promotes renal cyst growth and interstitial fibrosis in polycystic kidney diseases, we propose that the control of periostin by MMP9 and its associated intracellular signaling pathways including integrins, integrin-linked kinase and focal adhesion kinase confers to MMP9 a protective effect on the severity of the disease.

Proteomic Approaches and Potential Applications in Autosomal Dominant Polycystic Kidney Disease and Fabry Disease

Although rare, hereditary diseases, such as autosomal dominant polycystic kidney disease (ADPKD) and Fabry disease (FD) may significantly progress towards severe nephropathy. It is crucial to characterize it accurately, predict the course of the illness and estimate treatment effectiveness. A huge effort has been undertaken to find reliable biomarkers that might be useful for an early prevention of the disease progression and/or any invasive diagnostic procedures. The study of proteomics, or the small peptide composition of a sample, is a field of study under continuous development. Over the past years, several strategies have been created to study and define the proteome of samples from widely varying origins. However, urinary proteomics has become essential for discovering novel biomarkers in kidney disease. Here, the extracellular vesicles in human urine that contain cell-specific marker proteins from every segment of the nephron, offer a source of potentially valuable urinary biomarkers, and may play an essential role in kidney development and kidney disease. This review summarizes the relevant literature investigating the proteomic approaches and potential applications in the regular studies of ADPKD and FD.

Matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases in kidney disease

Matrix metalloproteinases (MMPs) are a group of zinc and calcium endopeptidases which cleave extracellular matrix (ECM) proteins. They are also involved in the degradation of cell surface components and regulate multiple cellular processes, cell to cell interactions, cell proliferation, and cell signaling pathways. MMPs function in close interaction with the endogenous tissue inhibitors of matrix metalloproteinases (TIMPs), both of which regulate cell turnover, modulate various growth factors, and participate in the progression of tissue fibrosis and apoptosis. The multiple roles of MMPs and TIMPs are continuously elucidated in kidney development and repair, as well as in a number of kidney diseases. This chapter focuses on the current findings of the significance of MMPs and TIMPs in a wide range of kidney diseases, whether they result from kidney tissue changes, hemodynamic alterations, tubular epithelial cell apoptosis, inflammation, or fibrosis. In addition, the potential use of these endopeptidases as biomarkers of renal dysfunction and as targets for therapeutic interventions to attenuate kidney disease are also explored in this review.

A Multitubular Kidney-on-Chip to Decipher Pathophysiological Mechanisms in Renal Cystic Diseases

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a major renal pathology provoked by the deletion of PKD1 or PKD2 genes leading to local renal tubule dilation followed by the formation of numerous cysts, ending up with renal failure in adulthood. In vivo, renal tubules are tightly packed, so that dilating tubules and expanding cysts may have mechanical influence on adjacent tubules. To decipher the role of this coupling between adjacent tubules, we developed a kidney-on-chip reproducing parallel networks of tightly packed tubes. This original microdevice is composed of cylindrical hollow tubes of physiological dimensions, parallel and closely packed with 100-200 μm spacing, embedded in a collagen I matrix. These multitubular systems were properly colonized by different types of renal cells with long-term survival, up to 2 months. While no significant tube dilation over time was observed with Madin-Darby Canine Kidney (MDCK) cells, wild-type mouse proximal tubule (PCT) cells, or with PCT Pkd1 +/- cells (with only one functional Pkd1 allele), we observed a typical 1.5-fold increase in tube diameter with isogenic PCT Pkd1 -/- cells, an ADPKD cellular model. This tube dilation was associated with an increased cell proliferation, as well as a decrease in F-actin stress fibers density along the tube axis. With this kidney-on-chip model, we also observed that for larger tube spacing, PCT Pkd1 -/- tube deformations were not spatially correlated with adjacent tubes whereas for shorter spacing, tube deformations were increased between adjacent tubes. Our device reveals the interplay between tightly packed renal tubes, constituting a pioneering tool well-adapted to further study kidney pathophysiology.

Association of Abdominal Aortic Aneurysm and Simple Renal Cysts: A Systematic Review and Meta-Analysis

BACKGROUND-OBJECTIVE

Prior studies have suggested a higher prevalence of simple renal cysts (SRC) among patients with aortic disease, including abdominal aortic aneurysms (AAA). Thus, the aim of this study was to systematically review all currently available literature and investigate whether patients with AAA are more likely to have SRC.

METHODS

This study was performed according to the PRISMA guidelines. A meta-analysis was conducted with the use of random effects modeling and the I-square was used to assess heterogeneity. Odds ratios (OR) and the corresponding 95% confidence intervals (CI) were synthesized to compare the prevalence of several patients' characteristics between AAA vs. no-AAA cases.

RESULTS

Eleven retrospective studies, 9 comparative (AAA vs. no-AAA groups) and 3 single-arm (AAA group), were included in this meta-analysis, enrolling patients (AAA: N = 2,297 vs. no-AAA: N = 35,873) who underwent computed tomography angiography as part of screening or preoperative evaluation for reasons other than AAA. The cumulative incidence of SRC among patients with AAA and no-AAA was 55% (95% CI: 49%-61%) and 32% (95% CI: 22%-42%) respectively, with a statistically higher odds of SRC among patients with AAA (OR: 3.02; 95% CI: 2.01-4.56; P< 0.001). The difference in SRC prevalence remained statistically significant in a sensitivity analysis, after excluding the study with the largest sample size (OR: 2.71; 95% CI: 1.91-3.84; P< 0.001).

CONCLUSIONS

Our meta-analysis demonstrated a 3-fold increased prevalence of SRC in patients with AAA compared to no-AAA cases, indicating that the pathogenic processes underlying SRC and AAA could share a common pathophysiologic mechanism. Thus, patients with SRC could be considered at high risk for AAA formation, potentially warranting an earlier AAA screening.

Immunohistochemical Profiles of Matrix Metalloproteinases and Vascular Endothelial Growth Factor Overexpression in the Antoni B Area of Vestibular Schwannomas

OBJECTIVE

To evaluate the clinical manifestations of cystic vestibular schwannomas (VSs), investigate the immunohistochemical profiles of matrix metalloproteinases (MMPs) and vascular endothelial growth factor (VEGF) expression in Antoni A and B areas, and speculate the pathogenesis of cystic formation and intratumoral hemorrhage.

METHODS

Clinical features and outcomes of 24 cases of cystic VSs and 38 cases of solid VSs were retrospectively compared. Immunohistochemical studies were conducted to evaluate the characteristics of MMPs and VEGF in cystic and solid VSs.

RESULTS

The tumor size was 38.92 ± 1.86 mm and 31.95 ± 1.74 mm in the cystic and solid VSs group, respectively (P = 0.011). Cystic VSs were rich in the Antoni B area. MMP-9 expression was low in the Antoni A and B areas. MMP-2 was moderately expressed. No significant difference in MMP-2 expression existed between the Antoni A and B areas (P > 0.05). VEGF and MMP-14 expression were moderate in the Antoni A area and intense in the Antoni B area, and the expression of both was significantly greater in the Antoni B area than in the Antoni A area (P < 0.001).

CONCLUSIONS

MMP-14 and VEGF expression were significantly greater in the Antoni B area than in the Antoni A area. Upregulated MMP-14 may degrade loose collagen in the Antoni B area and contribute to cystic formation. MMP-14 can enhance VEGF activity, which may induce extravasation of a plasma ultrafiltrate, cystic expansion, and intratumoral hemorrhage. Therefore, MMP-14 inhibition may be a therapeutic strategy for treating cystic VSs.

Simple Renal Cysts Are Associated With 24-Month Prognosis of Patients With Type B Aortic Dissection and Hypertension

BACKGROUND

The association of simple renal cyst (SRC) with type B aortic dissection (BAD) has recently been established. However, no studies have examined adverse events after BAD hospitalization among patients with SRC. In this study, we assessed the prognostic value of SRC in BAD patients with hypertension after thoracic endovascular aortic repair (TEVAR).

METHODS

We studied all BAD patients with hypertension who were admitted for TEVAR (n = 238; age 56.1 ± 9.8 years, 84.0% male). Aortic-related adverse events (ARAE) were evaluated as outcomes at 3 months and 24 months after TEVAR.

RESULTS

Among the total number of patients, 104 (43.7%) had at least 1 SRC. Patients with SRC were significantly older than those without (59.6 ± 8.8 vs 53.3 ± 9.7; P < 0.001). Patients with SRC were also more likely to suffer from peripheral arterial disease (55.8% vs 40.3%; P = 0.018) and cerebrovascular accidents (47.1% vs 29.9%; P = 0.006) than those without. Median follow-up for the 238 patients was 18.5 (range 6.4-24.0) months. Cumulative ARAE-free rates were 94.5 ± 1.5% at the 3-month follow-up and 81.5 ± 2.8% at the 24-month follow-up. Independent predictors of 3-month ARAE were found to be insertion of ≥ 2 stents (hazard ratio [HR] 3.977, 95% confidence interval [CI] 1.224-12.920; P = 0.022). For 24-month follow-up, SRC (HR 1.962, 95% CI 1.023-3.764; P = 0.043) was evaluated as the only independent predictive factor. SRC (HR 8.841, 95% CI 1.726-45.294; P = 0.009) was also evaluated as an independent predictive factor for 24-month ARAEs in the chronic group, but not in the acute or the subacute group.

CONCLUSIONS

SRC could predict 24-month ARAE in BAD patients with hypertension after TEVAR, especially in the chronic group.

Hydrogen sulphide mitigates homocysteine-induced apoptosis and matrix remodelling in mesangial cells through Akt/FOXO1 signalling cascade

Cellular damage and accumulation of extracellular matrix (ECM) protein in the glomerulo-interstitial space are the signatures of chronic kidney disease (CKD). Hyperhomocysteinemia (HHcy), a high level of homocysteine (Hcy) is associated with CKD and further contributes to kidney damage. Despite a large number of studies, the signalling mechanism of Hcy-mediated cellular damage and ECM remodelling in kidney remains inconclusive. Hcy metabolizes to produce hydrogen sulphide (H2S), and a number of studies have shown that H2S mitigates the adverse effect of HHcy in a variety of diseases involving several signalling molecules, including forkhead box O (FOXO) protein. FOXO is a group of transcription factor that includes FOXO1, which plays important roles in cell growth and proliferation. On the other hand, a cell survival factor, Akt regulates FOXO under normal condition. However, the involvement of Akt/FOXO1 pathway in Hcy-induced mesangial cell damage remains elusive, and whether H2S plays any protective roles has yet to be clearly defined. We treated mouse mesangial cells with or without H2S donor, GYY4137 and FOXO1 inhibitor, AS1842856 in HHcy condition and determined the involvement of Akt/FOXO1 signalling cascades. Our results indicated that Hcy inactivated Akt and activated FOXO1 by dephosphorylating both the signalling molecules and induced FOXO1 nuclear translocation followed by activation of the FOXO1 transcription factor. These led to the induction of cellular apoptosis and synthesis of excessive ECM protein, in part, due to increased ROS production, loss of mitochondrial membrane potential (ΔΨm), reduction in intracellular ATP concentration, increased MMP-2, -9, -14 mRNA and protein expression, and Col I, IV and fibronectin protein expression. Interestingly, GYY4137 or AS1842856 treatment prevented these changes by modulating Akt/FOXO1 axis in HHcy. We conclude that GYY4137 and/or AS1842856 mitigates HHcy induced mesangial cell damage and ECM remodelling by regulating Akt/FOXO1 pathway.

Urine peptidome analysis predicts risk of end-stage renal disease and reveals proteolytic pathways involved in autosomal dominant polycystic kidney disease progression

Background

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by slowly progressive bilateral renal cyst growth ultimately resulting in loss of kidney function and end-stage renal disease (ESRD). Disease progression rate and age at ESRD are highly variable. Therapeutic interventions therefore require early risk stratification of patients and monitoring of disease progression in response to treatment.

Methods

We used a urine peptidomic approach based on capillary electrophoresis-mass-spectrometry (CE-MS) to identify potential biomarkers reflecting the risk for early progression to ESRD in the Consortium of Radiologic Imaging in Polycystic Kidney Disease (CRISP) cohort.

Results

A biomarker-based classifier consisting of 20 urinary peptides allowed the prediction of ESRD within 10-13 years of follow-up in patients 24-46 years of age at baseline. The performance of the biomarker score approached that of height-adjusted total kidney volume (htTKV) and the combination of the biomarker panel with htTKV improved prediction over either one alone. In young patients (<24 years at baseline), the same biomarker model predicted a 30 mL/min/1.73 m 2 glomerular filtration rate decline over 8 years. Sequence analysis of the altered urinary peptides and the prediction of the involved proteases by in silico analysis revealed alterations in distinct proteolytic pathways, in particular matrix metalloproteinases and cathepsins.

Conclusion

We developed a urinary test that accurately predicts relevant clinical outcomes in ADPKD patients and suggests altered proteolytic pathways involved in disease progression.

CTGF Is Expressed During Cystic Remodeling in the PKD/Mhm (cy/+) Rat Model for Autosomal-Dominant Polycystic Kidney Disease (ADPKD)

Connective tissue growth factor (CTGF, also named CCN2) plays an important role in the development of tubulointerstitial fibrosis, which most critically determines the progression to end-stage renal failure in autosomal-dominant polycystic kidney disease (ADPKD), the most common genetically caused renal disease. We determined CTGF expression in a well-characterized animal model of human ADPKD, the PKD/Mhm (cy/+) rat. Kidneys of 12 weeks old (cy/+) as well as (+/+) non-affected rats were analyzed for CTGF RNA and protein expression by RT-PCR, Northern and Western blot analyses, in situ hybridization, and IHC. Besides the established expression of CTGF in glomerular cells in kidneys of wild-type (+/+) animals, in (cy/+) rats, CTGF mRNA and protein were robustly expressed in interstitial, stellate-shaped cells, located in a scattered pattern underlying the cystic epithelium and in focal areas of advanced tubulointerstitial remodeling. Renal CTGF mRNA and protein expression levels were significantly higher in (cy/+) rats compared with their (+/+) littermates. Detection of CTGF expression in cells adjacent to cystic epithelium and in areas of marked fibrosis suggests a role in the local response to cyst development and indicates that CTGF may be a relevant factor contributing to tubulointerstitial fibrosis in polycystic kidney disease.

Inflammation and Fibrosis in Polycystic Kidney Disease

Polycystic kidney disease (PKD) is a commonly inherited disorder characterized by cyst formation and fibrosis (Wilson, N Engl J Med 350:151-164, 2004) and is caused by mutations in cilia or cilia-related proteins, such as polycystin 1 or 2 (Oh and Katsanis, Development 139:443-448, 2012; Kotsis et al., Nephrol Dial Transplant 28:518-526, 2013). A major pathological feature of PKD is the development of interstitial inflammation and fibrosis with an associated accumulation of inflammatory cells (Grantham, N Engl J Med 359:1477-1485, 2008; Zeier et al., Kidney Int 42:1259-1265, 1992; Ibrahim, Sci World J 7:1757-1767, 2007). It is unclear whether inflammation is a driving force for cyst formation or a consequence of the pathology (Ta et al., Nephrology 18:317-330, 2013) as in some murine models cysts are present prior to the increase in inflammatory cells (Phillips et al., Kidney Blood Press Res 30:129-144, 2007; Takahashi et al., J Am Soc Nephrol JASN 1:980-989, 1991), while in other models the increase in inflammatory cells is present prior to or coincident with cyst initiation (Cowley et al., Kidney Int 43:522-534, 1993, Kidney Int 60:2087-2096, 2001). Additional support for inflammation as an important contributor to cystic kidney disease is the increased expression of many pro-inflammatory cytokines in murine models and human patients with cystic kidney disease (Karihaloo et al., J Am Soc Nephrol JASN 22:1809-1814, 2011; Swenson-Fields et al., Kidney Int, 2013; Li et al., Nat Med 14:863-868, 2008a). Based on these data, an emerging model in the field is that disruption of primary cilia on tubule epithelial cells leads to abnormal cytokine cross talk between the epithelium and the inflammatory cells contributing to cyst growth and fibrosis (Ta et al., Nephrology 18:317-330, 2013). These cytokines are produced by interstitial fibroblasts, inflammatory cells, and tubule epithelial cells and activate multiple pathways including the JAK-STAT and NF-κB signaling (Qin et al., J Am Soc Nephrol JASN 23:1309-1318, 2012; Park et al., Am J Nephrol 32:169-178, 2010; Bhunia et al., Cell 109:157-168, 2002). Indeed, inflammatory cells are responsible for producing several of the pro-fibrotic growth factors observed in PKD patients with fibrosis (Nakamura et al., Am J Nephrol 20:32-36, 2000; Wilson et al., J Cell Physiol 150:360-369, 1992; Song et al., Hum Mol Genet 18:2328-2343, 2009; Schieren et al., Nephrol Dial Transplant 21:1816-1824, 2006). These growth factors trigger epithelial cell proliferation and myofibroblast activation that stimulate the production of extracellular matrix (ECM) genes including collagen types 1 and 3 and fibronectin, leading to reduced glomerular function with approximately 50% of ADPKD patients progressing to end-stage renal disease (ESRD). Therefore, treatments designed to reduce inflammation and slow the rate of fibrosis are becoming important targets that hold promise to improve patient life span and quality of life. In fact, recent studies in several PKD mouse models indicate that depletion of macrophages reduces cyst severity. In this chapter, we review the potential mechanisms of interstitial inflammation in PKD with a focus on ADPKD and discuss the role of interstitial inflammation in progression to fibrosis and ESRD.

Matrix Metalloproteinases in Kidney Disease: Role in Pathogenesis and Potential as a Therapeutic Target

Matrix metalloproteinases (MMPs) are large family of proteinases. In addition to a fundamental role in the remodeling of the extracellular matrix, they also cleave a number of cell surface proteins and are involved in multiple cellular processes. MMP activity is regulated via numerous mechanisms, including inhibition by endogenous tissue inhibitors of metalloproteinases (TIMPs). Similar to MMPs, a role for TIMPs has been established in multiple cell signaling pathways. Aberrant expression of MMPs and TIMPS in renal pathophysiology has long been recognized, and with the generation of specific knockout mice, the mechanistic role of several MMPs and TIMPs is becoming more understood and has revealed both pathogenic and protective roles. This chapter will focus on the expression and localization of MMPs and TIMPs in the kidney, as well as summarizing the current information linking these proteins to acute kidney injury and chronic kidney disease. In addition, we will summarize studies suggesting that MMPs and TIMPs may be biomarkers of renal dysfunction and represent novel therapeutic targets to attenuate kidney disease.

Diverticular disease is associated with benign intra-abdominal cystic disease

BACKGROUND

Diverticular disease (DD) and hepatic and renal cysts have been linked with defects in collagen and dysfunctional matrix metalloproteinases.

METHODS

Consecutive abdominal computed tomography scans between January-July 2015 were prospectively studied to determine a correlation between visceral cysts and DD. Patients with a sigmoid colectomy for pathology other than DD and scans in which DD and/or solid organs were not fully visualized were excluded. A subgroup analysis was performed on youthful DD patients (<55 years of age, n = 32) vs. older controls (>55, n = 213).

RESULTS

238 DD patients (50.8% male) and 369 controls (40.5% male, p = .02) were included. Incidence of visceral cystic disease in DD patients vs. controls was 71.4% vs. 22.5% (p < 0.00001). Renal cysts, present in 53.4% of the DD patients and 18.7% of the controls (p < .00001), were more common than hepatic cysts in both groups. Hepatic cyst prevalence was 8.8 vs. 2.4% (p = .0008). In the subgroup analysis, cystic disease was present in 56.2% of youthful DD patients vs. 29.1% of older controls (p = .004).

CONCLUSIONS

A significant association between cystic disease and DD was demonstrated overall and in subgroup analysis inclusive of youthful DD patients and older controls. These findings suggest a global defect in connective tissue integrity in DD patients.

Identification of MMP1 as a novel risk factor for intracranial aneurysms in ADPKD using iPSC models

Cardiovascular complications are the leading cause of death in autosomal dominant polycystic kidney disease (ADPKD), and intracranial aneurysm (ICA) causing subarachnoid hemorrhage is among the most serious complications. The diagnostic and therapeutic strategies for ICAs in ADPKD have not been fully established. We here generated induced pluripotent stem cells (iPSCs) from seven ADPKD patients, including four with ICAs. The vascular cells differentiated from ADPKD-iPSCs showed altered Ca(2+) entry and gene expression profiles compared with those of iPSCs from non-ADPKD subjects. We found that the expression level of a metalloenzyme gene, matrix metalloproteinase (MMP) 1, was specifically elevated in iPSC-derived endothelia from ADPKD patients with ICAs. Furthermore, we confirmed the correlation between the serum MMP1 levels and the development of ICAs in 354 ADPKD patients, indicating that high serum MMP1 levels may be a novel risk factor. These results suggest that cellular disease models with ADPKD-specific iPSCs can be used to study the disease mechanisms and to identify novel disease-related molecules or risk factors.

The renal protective effects of Anoectochilus roxburghii polysaccharose on diabetic mice induced by high-fat diet and streptozotocin

ETHNOPHARMACOLOGICAL RELEVANCE

Anoectochilus roxburghii (Wall.) Lindl. 1832 is an herbal medicine used to treat diabetes in China. Considering that Anoectochilus roxburghii polysaccharose (ARP) is the main constituent of Anoectochilus roxburghii, the present study is aimed to investigate the renal protection of ARP and its possible mechanism in diabetic mice.

MATERIALS AND METHODS

Institute of Cancer Research (ICR) mice were induced to diabetes with high-fat diet (HFD) and low-dose streptozotocin (STZ). ARP (100, 300 mg/kg) was orally administrated to diabetic mice once a day for consecutive 15 days. The fasting glucose level, expressions of key proteins of p38 MAP kinase cascade, inflammatory factors, fibronectin (FN) and the activities of matrix metalloproteinases (MMPs) were measured. Furthermore, the histological examination of the separated kidneys was also carried out.

RESULTS

Compared with the diabetic mice, ARP administration induced a significant decrease in blood glucose level and improved the body weight of diabetic mice. In addition, ARP inhibited the expression of renal p38 MAP kinase cascade and its downstream inflammatory factors including tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), FN as well as MMP2/9. Moreover, the histological examination showed an apparent reduction of mesangial matrix deposition and damage of microvascular structure after ARP administration.

CONCLUSIONS

The protective effects of ARP on diabetic renal damage may be attributed to the inhibition of p38 MAP kinase cascade and then attenuating the inflammatory responses and high glucose-induced renal damage.

Simple Renal Cysts as Markers of Thoracic Aortic Disease

Background

Thoracic aortic aneurysm is usually a clinically silent disease; timely detection is largely dependent upon identification of clinical markers of thoracic aortic disease (TAD); (bicuspid aortic valve, intracranial aortic aneurysm, bovine aortic arch, or positive family history). Recently, an association of simple renal cysts (SRC) with abdominal aortic aneurysm and aortic dissection was established. The aim of our study was to evaluate the prevalence of SRC in patients with TAD in order to assess whether the presence of SRC can be used as a predictor of TAD.

Methods and Results

We evaluated the prevalence of SRC in 842 patients with TAD (64.0% males) treated at our institution from 2004 to 2013 and compared to a control group of patients (n=543; 56.2% males). Patients were divided into 4 groups: ascending aortic aneurysm (456; 54.2%); descending aortic aneurysm (86; 10.2%); type A aortic dissection (118; 14.0%); and type B aortic dissection (182; 21.6%). SRC were identified by abdominal computed tomography or magnetic resonance imaging of these patients. Prevalence of SRC is 37.5%, 57.0%, 44.1%, and 47.3% for patients with ascending aneurysm, descending aneurysm, type A dissection, and type B dissection, respectively. Prevalence of SRC in the control group was 15.3%. Prevalence of SRC was not significantly different between male and female aortic disease patients, despite reported general male predominance (2:1), which was also observed in our control group (1.7:1).

Conclusions

This study establishes an increased prevalence of SRC in patients with TAD. SRC can potentially be used as a marker for timely detection of patients at risk of TAD.

Inflammation and Fibrosis in ADPKD

Diverse signaling pathways have been reported to be associated with polycystic kidney disease (PKD). Cell proliferation is widely known to be an important pathway related to this disease. However, studies on the interactions of inflammation and fibrosis with polycystic kidney disease have been limited. Inflammation is one of the protective systems involved in the response to foreign molecules. In PKD, it was reported that the activity of signaling pathways associated with inflammation is increased. Also, fibrosis is the development of excess fibrous tissue in organ or tissue. It is an abnormal phenomenon in which the extent of fibrous connective tissues is increased. In PKD, increases in the activity of molecules such as growth factor and TGF-β have been reported to occur and promote fibrosis. Therefore, the inflammation and fibrosis responses have been suggested as therapeutic targets for PKD. In order to guide further studies, this review indicates the roles of inflammatory and fibrosis signaling in PKD.

Inhibition of metalloprotease hyperactivity in cystic cholangiocytes halts the development of polycystic liver diseases

OBJECTIVE

Polycystic liver diseases (PCLDs) are genetic disorders characterised by progressive bile duct dilatation and/or cyst development. Their pathogenesis is a consequence of hyperproliferation, hypersecretion and microRNA alterations in cholangiocytes. Here we evaluate the role of matrix metalloproteases (MMPs) in the hepatic cystogenesis of PCLDs.

DESIGN

Metalloprotease activity was measured by microfluorimetric assays in normal and polycystic cholangiocyte cultures from humans and rats, and gene expression by real time quantitative PCR. The role of cytokines, oestrogens and growth factors present in the cystic fluid of PCLD patients was evaluated for MMP activity. The MMP inhibitor marimastat was examined for cystic expansion in vitro and in polycystic kidney (PCK) rats.

RESULTS

Polycystic human and rat cholangiocytes displayed increased MMP activity, which was associated with increased mRNA levels of different MMPs. Interleukin (IL)-6 and IL-8, and 17β-oestradiol, all stimulated MMP activity in human cholangiocytes. The presence of antibodies against IL-6 and/or IL-8 receptor/s inhibited baseline MMP hyperactivity of polycystic human cholangiocytes but had no effect on normal human cholangiocytes. MMP-3 was overexpressed in cystic cholangiocytes from PCLD human and PCK rat livers by immunohistochemistry. Marimastat reduced MMP hyperactivity of polycystic human and rat cholangiocytes and blocked the cystic expansion of PCK cholangiocytes cultured in three-dimensions. Chronic treatment of 8-week-old PCK rats with marimastat inhibited hepatic cystogenesis and fibrosis.

CONCLUSIONS

PCLDs are associated with cholangiocyte MMP hyperactivity resulting from autocrine/paracrine stimulation by IL-6 and IL-8. Inhibition of this MMP hyperactivity with marimastat decreased hepatic cystogenesis in vitro and in an animal model of PCLD, offering a potential therapeutic tool.

Presence of Renal Simple Cysts Is Associated With Increased Risk of Abdominal Aortic Aneurysms

We compared the incidence of renal simple cysts in 271 patients with abdominal aortic aneurysm (AAA) and 1387 patients without AAA (controls) using computed tomography (CT) angiography and abdominal CT, as a health screening program. The AAA group had significantly higher prevalence of renal simple cysts (55% vs 19%, P = .001) and chronic obstructive pulmonary disease (COPD; 12% vs 1%, P = .011) than the controls. After propensity score matching (n = 164), the prevalence of renal simple cysts was still significantly higher in the AAA group. In multivariate analysis, independent predictors of AAA were age, male gender, smoking history, hypertension, high-sensitivity C-reactive protein, creatinine, COPD, and renal simple cysts. The structural weakness predisposing for renal simple cysts may be associated with the initiation of AAA formation. More studies are needed to determine whether the presence of renal simple cysts can be considered as a risk factor for AAA.

Gpr48 deficiency induces polycystic kidney lesions and renal fibrosis in mice by activating Wnt signal pathway

G protein-coupled receptor 48 (Gpr48/Lgr4) is essential to regulate the development of multiple tissues in mice. The notion that Gpr48 functions in renal development prompted us to investigate the relation between Gpr48 and renal diseases. Using a Gpr48 knockout mice model, we observed that 66.7% Gpr48 null mice developed polycystic lesions in the kidney, while no cysts were observed in the kidneys of wild-type mice. Polycystic kidney disease 1 (PKD1) and PKD2 expressions were also markedly decreased in the Gpr48 knockout mice. Abnormal expressions of exra-cellular matrix protein lead to the progression of polycystic kidney disease and the formation of renal fibrosis in the Gpr48 null mice. The expressions of several Wnt molecules and its receptors were increased and marked β-catenin nuclear accumulation was observed in the Gpr48 null mice. The inhibitors of Wnt/β-catenin signal pathway such as GSK3β and axin2 were loss of function. The Wnt/PCP signaling pathway is also activated in Gpr48 null mice. However, TGF-β expression and phosphorylated Smad2/3 levels were not altered. Collectively, our results showed that Gpr48 null mice are at a greater risk of suffering from polycystic lesions and renal fibrosis. Moreover, the formation of polycystic lesions and renal fibrosis induced by Gpr48 deficiency involves the activation of Wnt signaling pathway but not the TGF-β/Smad pathway.

Parallel analysis of mRNA and microRNA microarray profiles to explore functional regulatory patterns in polycystic kidney disease: using PKD/Mhm rat model

Autosomal polycystic kidney disease (ADPKD) is a frequent monogenic renal disease, characterised by fluid-filled cysts that are thought to result from multiple deregulated pathways such as cell proliferation and apoptosis. MicroRNAs (miRNAs) are small non-coding RNAs that regulate the expression of many genes associated with such biological processes and human pathologies. To explore the possible regulatory role of miRNAs in PKD, the PKD/Mhm (cy/+) rat, served as a model to study human ADPKD. A parallel microarray-based approach was conducted to profile the expression changes of mRNAs and miRNAs in PKD/Mhm rats. 1,573 up- and 1,760 down-regulated genes were differentially expressed in PKD/Mhm. These genes are associated with 17 pathways (such as focal adhesion, cell cycle, ECM-receptor interaction, DNA replication and metabolic pathways) and 47 (e.g., cell proliferation, Wnt and Tgfβ signaling) Gene Ontologies. Furthermore, we found the similar expression patterns of deregulated genes between PKD/Mhm (cy/+) rat and human ADPKD, PKD1^L3/L3, PKD1^−/−, Hnf1α-deficient, and Glis2^lacZ/lacZ models. Additionally, several differentially regulated genes were noted to be target hubs for miRNAs. We also obtained 8 significantly up-regulated miRNAs (rno-miR-199a-5p, −214, −146b, −21, −34a, −132, −31 and −503) in diseased kidneys of PKD/Mhm rats. Additionally, the binding site overrepresentation and pathway enrichment analyses were accomplished on the putative targets of these 8 miRNAs. 7 out of these 8 miRNAs and their possible interactions have not been previously described in ADPKD. We have shown a strong overlap of functional patterns (pathways) between deregulated miRNAs and mRNAs in the PKD/Mhm (cy/+) rat model. Our findings suggest that several miRNAs may be associated in regulating pathways in ADPKD. We further describe novel miRNAs and their possible targets in ADPKD, which will open new avenues to understand the pathogenesis of human ADPKD. Furthermore they could serve as a useful resource for anti-fibrotic therapeutics.

Increasing extracellular matrix collagen level and MMP activity induces cyst development in polycystic kidney disease

Background

Polycystic Kidney Disease (PKD) kidneys exhibit increased extracellular matrix (ECM) collagen expression and metalloproteinases (MMPs) activity. We investigated the role of these increases on cystic disease progression in PKD kidneys.

Methods

We examined the role of type I collagen (collagen I) and membrane bound type 1 MMP (MT1-MMP) on cyst development using both in vitro 3 dimensional (3D) collagen gel culture and in vivo PCK rat model of PKD.

Results

We found that collagen concentration is critical in controlling the morphogenesis of MDCK cells cultured in 3D gels. MDCK cells did not form 3D structures at collagen I concentrations lower than 1 mg/ml but began forming tubules when the concentration reaches 1 mg/ml. Significantly, these cells began to form cyst when collagen I concentration reached to 1.2 mg/ml, and the ratios of cyst to tubule structures increased as the collagen I concentration increased. These cells exclusively formed cyst structures at a collagen I concentration of 1.8 mg/ml or higher. Overexpression of MT1-MMP in MDCK cells significantly induced cyst growth in 3D collagen gel culture. Conversely, inhibition of MMPs activity with doxycycline, a FDA approved pan-MMPs inhibitor, dramatically slowed cyst growth. More importantly, the treatment of PCK rats with doxycycline significantly decreased renal tubule cell proliferation and markedly inhibited the cystic disease progression.

Conclusions

Our data suggest that increased collagen expression and MMP activity in PKD kidneys may induce cyst formation and expansion. Our findings also suggest that MMPs may serve as a therapeutic target for the treatment of human PKD.

Matrix metalloproteinases in kidney homeostasis and diseases

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases that have been increasingly linked to both normal physiology and abnormal pathology in the kidney. Collectively able to degrade all components of the extracellular matrix, MMPs were originally thought to antagonize the development of fibrotic diseases solely through digestion of excessive matrix. However, increasing evidence has shown that MMPs play a wide variety of roles in regulating inflammation, epithelial-mesenchymal transition, cell proliferation, angiogenesis, and apoptosis. We now have robust evidence for MMP dysregulation in a multitude of renal diseases including acute kidney injury, diabetic nephropathy, glomerulonephritis, inherited kidney disease, and chronic allograft nephropathy. The goal of this review is to summarize current findings regarding the role of MMPs in kidney diseases as well as the mechanisms of action of this family of proteases.

Fibrosis and progression of autosomal dominant polycystic kidney disease (ADPKD)

The age on onset of decline in renal function and end-stage renal disease (ESRD) in autosomal polycystic kidney disease (ADPKD) is highly variable and there are currently no prognostic tools to identify patients who will progress rapidly to ESRD. In ADPKD, expansion of cysts and loss of renal function are associated with progressive fibrosis. Similar to the correlation between tubulointerstitial fibrosis and progression of chronic kidney disease (CKD), in ADPKD, fibrosis has been identified as the most significant manifestation associated with an increased rate of progression to ESRD. Fibrosis in CKD has been studied extensively. In contrast, little is known about the mechanisms underlying progressive scarring in ADPKD although some commonality may be anticipated. Current data suggest that fibrosis associated with ADPKD shares at least some of the "classical" features of fibrosis in CKD (increased interstitial collagens, changes in matrix metalloproteinases (MMPs), over-expression of tissue inhibitor of metalloproteinase-1 (TIMP-1), over-expression of plasminogen activator inhibitor-1 (PAI-1) and increased transforming growth factor beta (TGFβ) but that there are also some unique and stage-specific features. Epithelial changes appear to precede and to drive interstitial changes leading to the proposal that development of fibrosis in ADPKD is biphasic with alterations in cystic epithelia precipitating changes in interstitial fibroblasts and that reciprocal interactions between these cell types drives progressive accumulation of extracellular matrix (ECM). Since fibrosis is a major component of ADPKD it follows that preventing or slowing fibrosis should retard disease progression with obvious therapeutic benefits. The development of effective anti-fibrotic strategies in ADPKD is dependent on understanding the precise mechanisms underlying initiation and progression of fibrosis in ADPKD and the role of the intrinsic genetic defect in these processes. This article is part of a Special Issue entitled: Polycystic Kidney Disease.

Drug discovery for polycystic kidney disease

In polycystic kidney disease (PKD), a most common human genetic diseases, fluid-filled cysts displace normal renal tubules and cause end-stage renal failure. PKD is a serious and costly disorder. There is no available therapy that prevents or slows down the cystogenesis and cyst expansion in PKD. Numerous efforts have been made to find drug targets and the candidate drugs to treat PKD. Recent studies have defined the mechanisms underlying PKD and new therapies directed toward them. In this review article, we summarize the pathogenesis of PKD, possible drug targets, available PKD models for screening and evaluating new drugs as well as candidate drugs that are being developed.

Rosiglitazone attenuates development of polycystic kidney disease and prolongs survival in Han:SPRD rats

Although pioglitazone, a PPAR-gamma (peroxisome-proliferator-activated receptor-gamma) agonist, has been shown to prolong survival in two rapidly progressive pkd1 (polycystic kidney disease 1)-knockout mice models through disparate mechanisms, these studies lacked data on therapeutic potential and long-term safety because of a short observation period. In the present study, we have used another potent PPAR-gamma agonist, rosiglitazone, to treat Han:SPRD rats, a slowly progressive ADPKD (autosomal dominant PKD) animal model, and confirmed that short-term treatment was able to delay the progression of kidney cysts and protect renal function, which may relate to down-regulating the abnormally activated beta-catenin signalling pathway and its anti-inflammatory and anti-fibrosis effects. Long-term administration significantly prolonged the survival of Han:SPRD rats. Moreover, early therapy in rats with normal renal function had a better outcome than delayed therapy, while initiating therapy in rats with mild impaired renal function still protected renal function. The efficacy of rosiglitazone depended on continuous drug administration; withdrawal of the drug caused accelerated deterioration of renal function in effectively treated rats and shortened their survival to an untreated state. Long-term administration led to cardiac enlargement, probably due to rosiglitazone-mediated sodium re-absorption. In conclusion, these results indicate that rosiglitazone was able to effectively delay the progression of kidney disease and protect renal function in Han:SPRD rats, but its adverse effect of inducing cardiac enlargement should also be monitored closely.

Novel targets for the treatment of autosomal dominant polycystic kidney disease

IMPORTANCE OF THE FIELD

Autosomal dominant (AD) polycystic kidney disease (PKD) is the most common life-threatening hereditary disorder. There is currently no therapy that slows or prevents cyst formation and kidney enlargement in humans. An increasing number of animal studies have advanced our understanding of molecular and cellular targets of PKD.

AREAS COVERED IN THE REVIEW

The purpose of this review is to summarize the molecular and cellular targets involved in cystogenesis and to update on the promising therapies that are being developed and tested based on knowledge of these molecular and cellular targets.

WHAT THE READER WILL GAIN

Insight into the pathogenesis of PKD and how a better understanding of the pathogenesis of PKD has led to the development of potential therapies to inhibit cyst formation and/or growth and improve kidney function.

TAKE HOME MESSAGE

The results of animal studies in PKD have led to the development of clinical trials testing potential new therapies to reduce cyst formation and/or growth. A vasopressin V2 receptor antagonist, mTOR inhibitors, blockade of the renin-angiotensin system and statins that reduce cyst formation and improve renal function in animal models of PKD are being tested in interventional studies in humans.

Renal cysts as strongest association with abdominal aortic aneurysm in elderly

OBJECTIVE

The aim of this study is to investigate the positive association between the presence of renal cysts and AAA.

PATIENTS AND METHODS

A retrospective chart review on the clinical data of 396 consecutive patients, who underwent CT scans for preoperative evaluation of thoracic and cardiovascular surgery in Sapporo Medical University from the period of January 2007 to December 2008, was conducted.

RESULTS

When comparing patients with renal cysts (n = 164) to those without (n = 233), there was a statistically significant difference between the presence of renal cysts and male gender (p = 0.007), hypertension (p = 0.003), and AAA (p < 0.001) on univariate analysis. In addition, when comparing patients with AAA to those without, although COPD but not AAA was associated with renal cysts in less than 65 years old, the presence of renal cysts was the strongest association with AAA among patients belonging to the 65 to 74 years old group and over 75 years old group on multivariate analysis.

CONCLUSIONS

There is a statistically higher incidence of renal cysts in patients with AAA compared to patients without AAA in the group of elder cardiovascular patients. It is likely that AAA and renal cysts share a common pathogenesis.

Identification of a unique urinary biomarker profile in patients with autosomal dominant polycystic kidney disease

To gain some insight into early disease progression in human autosomal dominant polycystic kidney disease (ADPKD), we analyzed the urine proteome of 41 young patients with ADPKD whose renal function was relatively preserved. Using capillary electrophoresis and mass spectrometry, we compared these results to those from age-matched healthy controls and patients with other renal diseases. There were 197 proteins with significantly altered urinary excretion; and 38 of them could be sequenced, most of which were collagen fragments. This suggests that there is high turnover of extracellular matrix proteins. Uromodulin peptides, previously implicated in tubular injury, were also found in the urine specimens. These marker proteins were found to distinguish patients from controls with a high degree of accuracy. The sensitivity and specificity of this marker set remained high in an independent validation cohort of 24 patients with ADPKD and 35 healthy controls, and even in comparisons of patients with a variety of other renal diseases or patients with kidney or bladder cancer. These findings present a potential hypothesis for the mechanisms of disease progression in ADPKD which will need to be confirmed by further studies.

Microarray-based approach identifies microRNAs and their target functional patterns in polycystic kidney disease

Background

MicroRNAs (miRNAs) play key roles in mammalian gene expression and several cellular processes, including differentiation, development, apoptosis and cancer pathomechanisms. Recently the biological importance of primary cilia has been recognized in a number of human genetic diseases. Numerous disorders are related to cilia dysfunction, including polycystic kidney disease (PKD). Although involvement of certain genes and transcriptional networks in PKD development has been shown, not much is known how they are regulated molecularly.

Results

Given the emerging role of miRNAs in gene expression, we explored the possibilities of miRNA-based regulations in PKD. Here, we analyzed the simultaneous expression changes of miRNAs and mRNAs by microarrays. 935 genes, classified into 24 functional categories, were differentially regulated between PKD and control animals. In parallel, 30 miRNAs were differentially regulated in PKD rats: our results suggest that several miRNAs might be involved in regulating genetic switches in PKD. Furthermore, we describe some newly detected miRNAs, miR-31 and miR-217, in the kidney which have not been reported previously. We determine functionally related gene sets, or pathways to reveal the functional correlation between differentially expressed mRNAs and miRNAs.

Conclusion

We find that the functional patterns of predicted miRNA targets and differentially expressed mRNAs are similar. Our results suggest an important role of miRNAs in specific pathways underlying PKD.

Expression of matrix metalloproteinase 1 and 2 in congenital choledochal cyst and its clinical significance

BACKGROUND

The pathogenesis of congenital choledochal cyst (CCC) is still not well elucidated. This study was conducted to detect the expression of matrix metalloproteinase-1 and 2 (MMP-1 and MMP-2) in CCC. The roles of MMP-1 and MMP-2 in CCC formation were also discussed.

METHODS

Specimens of CCC and gallbladders were taken from 53 patients with CCC, including 21 boys and 32 girls aged from 4 months to 17 years (mean: 6.5 years old). Twenty-eight normal gallbladders served as controls. Immunohistochemical method was used to detect the expressions of MMP-1 and MMP-2. Image analysis was made to quantitatively analyze the protein expression.

RESULTS

The expressions of MMP-1 and MMP-2 were located in epithelial cells, matrix cells, and inflammatory cells of the CCC wall. Various expressions were also found in the mucosa membrane cells of the CCC gallbladder. The expressions of MMP-1 and MMP-2 were low in the control group. Quantitatively, the expressions of MMP-1 and MMP-2 in the CCC wall were markedly higher than in the CCC gallbladder and the control group (P<0.01). There was no significant difference between the CCC gallbladder and the control group (P>0.05).

CONCLUSIONS

The expression of MMP-1 and MMP -2 in the CCC wall is higher than in the CCC gallbladder and controls. The over-expression of MMP-1 and MMP-2 may be involved in the pathogenesis of CCC.

Autosomal dominant polycystic kidney disease: recent advances in pathogenesis and treatment

Autosomal dominant polycystic kidney disease (ADPKD) is a common genetic disorder affecting 1 in 1,000 people in the general population and accounts for up to 10% of all patients on renal replacement therapy. Numerous fluid-filled epithelial cysts arise from different nephron segments as spherical dilatations or small out-pouchings, enlarge progressively and eventually become disconnected from the rest of the renal tubule. The development of cysts is accompanied by destruction of the renal parenchyma, interstitial fibrosis, cellular infiltration and loss of functional nephrons. ADPKD is not only a kidney disease but also a systemic disorder associated with intracranial arterial aneurysms, cardiac valvular defects, colonic diverticulosis and cyst formation in other organs such as the liver, spleen and pancreas. The identification of PKD1 and PKD2 together with the drive to elucidate the functions of their encoded proteins, polycystin-1 (PC1) and polycystin-2 (PC2), has led to an explosion of clinical and scientific interest in this common disorder. The aim of this review is to highlight recent advances in our understanding of ADPKD pathogenesis which are leading to exciting new treatment strategies.

Polycystic kidney disease and renal injury repair: common pathways, fluid flow, and the function of polycystin-1

The root cause for most cases of autosomal-dominant polycystic kidney disease (ADPKD) is mutations in the polycystin-1 (PC1) gene. While PC1 has been implicated in a perplexing variety of protein interactions and signaling pathways, what its normal function is and why its disruption leads to the proliferation of renal epithelial cells are unknown. Recent results suggest that PC1 is involved in mechanotransduction by primary cilia measuring the degree of luminal fluid flow. PC1 has also recently been shown to regulate the mTOR and signal transducers and activators of transcription (STAT) 6 pathways. These two pathways are normally dormant in the healthy kidney but are activated in response to injury and appear to drive a proliferative repair response. This review develops the idea that a critical function of PC1 and primary cilia in the adult kidney may be to sense renal injury by detecting changes in luminal fluid flow and to trigger proliferation. Constitutive activation of these pathways in ADPKD would lead to the futile attempt to repair a nonexisting injury, resulting in cyst growth. The existence of many known cellular and molecular similarities between renal repair and ADPKD supports this model.

Increased expression of intracystic matrix metalloproteinases in brain tumors: relationship to the pathogenesis of brain tumor-associated cysts and peritumoral edema

Although several types of brain tumors are commonly associated with cyst formation, the pathogenesis of tumor-associated cysts (TAC) is unknown. We investigated the matrix metalloproteinase (MMP) expression of cyst fluids to elucidate the pathogenesis of TAC in brain tumors. We also examined the relationship between the severity of peritumoral edema and the expression of intracystic MMP. We collected 40 cyst fluid samples from 34 patients with TAC and studied the expression of MMP-2 and -9 in the cyst fluid using gelatin zymography. Radiological studies were used to estimate the severity of the peritumoral edema and to determine the presence of TAC. Although gelatin zymography of the cyst fluid showed high levels of MMPs, there was no correlation between the expression of MMPs in the cyst fluid and that in the tumor tissue. The level of MMP expression in the cyst fluid did not reflect the pathologic grade of the individual tumors. However, the total and activated MMP-9 levels were significantly associated with the severity of the peritumoral edema (p<0.05). These results suggest that MMPs may be partly involved in the pathogenesis of TAC and peritumoral edema in brain tumors.

Cystic vestibular schwannomas: a possible role of matrix metalloproteinase-2 in cyst development and unfavorable surgical outcome

OBJECT

The authors evaluated the clinical manifestations and surgical results in patients with cystic vestibular schwannoma (VS), and investigated the matrix metalloproteinase (MMP) expression of the cyst fluid and wall in an attempt to elucidate the pathogenesis and characteristics of this disease.

METHODS

The clinical and neuroimaging features, perioperative findings, and surgical outcomes in 24 cases of cystic VS and 82 cases of solid VS, all of which were treated using the suboccipital approach, were retrospectively compared. To evaluate the role of MMP in cystic VS, gelatin zymography and immunohistochemical studies of the cyst fluid, wall, and solid portion were performed in nine cases of this disease. The mean duration of symptoms was shorter (14.0 months compared with 26.1 months; p = 0.04) and the mean size of the tumor was larger (43.8 mm compared with 34.2 mm; p = 0.048) in the cystic than the solid VS group. Although gross-total resection was easier to accomplish in this group (100% compared with 84.1%), adhesion to the facial nerve was more frequent (62.5% compared with 48.8%; p = 0.042). On gelatin zymography studies, MMP-2 expression was ubiquitously observed in all cyst fluids. Immunohistochemical analysis of the cyst wall showed that MMP-2 was apparently localized to the tumor cells on the luminal inner surface, adjacent to the cyst cavity.

CONCLUSIONS

Resection of cystic VS is complicated by severe adhesion of the tumor capsule to the facial nerve and the large size of the lesion. The authors believe that MMP-2 may be involved in the pathogenesis of cyst formation or in its enlargement and may aggravate adhesion to the facial nerve, either by promoting the enlargement of the tumor or engendering the degradation of the tumor-nerve barrier proteolytically.

Endothelin B receptor blockade accelerates disease progression in a murine model of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic disease that causes kidney failure and accounts for 10% of all patients who are on renal replacement therapy. However, the marked phenotypic variation between patients who carry the same PKD1 or PKD2 mutation suggests that nonallelic factors may have a greater influence on the cystic phenotype. Endothelin-1 (ET-1) transgenic mice have been reported to develop profound renal cystic disease and interstitial fibrosis without hypertension. The hypothesis that ET-1 acts as a modifying factor for cystic disease progression was tested in an orthologous mouse model of ADPKD (Pkd2(WS25/-)). Four experimental groups (n = 8 to 11) were treated from 5 to 16 wk of age with the highly selective orally active receptor antagonists ABT-627 (ETA) and A-192621 (ETB) singly or in combination. Unexpected, ETB blockade led to accelerated cystic kidney disease. Of significance, this was associated with a reduction in urine volume and sodium excretion and increases in urine osmolarity and renal cAMP and ET-1 concentrations. The deleterious effect of chronic ETB blockade was neutralized by simultaneous ETA blockade. ETA blockade alone resulted in a significant increase in tubular cell proliferation but did not alter the cystic phenotype. It is concluded that the balance between ETA and ETB signaling is critical for maintaining tubular structure and function in the cystic kidney. These results implicate ET, acting via vasopressin-dependent and independent pathways, as a major modifying factor for cystic disease progression in human ADPKD.

Role of matrix metalloproteinases in renal pathophysiologies

Matrix metalloproteinases (MMPs) are a large family of proteinases that remodel extracellular matrix (ECM) components and cleave a number of cell surface proteins. MMP activity is regulated via a number of mechanisms, including inhibition by tissue inhibitors of metalloproteinases (TIMPs). Originally thought to cleave only ECM proteins, MMP substrates are now known to include signaling molecules (growth factor receptors) and cell adhesion molecules. Recent data suggest a role for MMPs in a number of renal pathophysiologies, both acute and chronic. This review will focus on the expression and localization of MMPs and TIMPs in the kidney, as well as summarizing the current information linking these proteins to acute kidney injury, glomerulosclerosis/tubulointerstitial fibrosis, chronic allograft nephropathy, diabetic nephropathy, polycystic kidney disease, and renal cell carcinoma.

Transcriptome analysis of a rat PKD model: Importance of genes involved in extracellular matrix metabolism

Transcriptome analysis of a rat polycystic kidney disease (PKD) model: importance of genes involved in extracellular matrix metabolism. PKD is a common genetic cause of chronic renal failure, and is characterized by the accumulation of fluid-filled cysts in the kidneys and other organs. Abnormalities in the expression of selected genes thought to be involved in cystogenesis have been described, but no systematic analysis of the global transcriptomal pattern has been reported. With this aim, a rat oligomicroarray was used to identify variations in gene expression in Han:Sprague-Dawley Cy/Cy rats, an animal model presenting a severe PKD phenotype. Some upregulated genes were validated using real-time polymerase chain reaction in Cy/Cy and Cy/+ rats. Among the 350 genes identified as being upregulated, we found about 30 genes involved in extracellular matrix metabolism. These genes encoded proteins or peptides that could be implicated into two different biological processes: molecules involved in fibrosis and proteins involved in adhesion to the extracellular matrix. In heterozygotes, some genes (glypican 3, fibronectin 1) were already upregulated in early stages of the disease. We conclude that differential regulation of genes linked to extracellular matrix metabolism may be one of the first events leading to tubule enlargement and subsequent cyst formation in PKD.

Ischemia-induced cleavage of cadherins in NRK cells requires MT1-MMP (MMP-14)

Ischemia is a leading cause of acute renal failure (ARF), a disease associated with high morbidity and mortality. Disruption of intercellular adhesion in the proximal tubules is linked to ARF, although the molecular mechanism(s) remains unclear. Our previous studies showed that ischemia is associated with cadherin cleavage and loss in NRK cells, putatively due to a matrix metalloproteinase (MMP) ( 7 ). In the current studies, a MMP required for E-cadherin cleavage and N-cadherin loss was identified. Chemical inhibitors against a number of soluble MMPs ( 1 , 2 , 3 , 8 , 9 ) failed to completely attenuate ischemia-induced cadherin loss. Under ischemic conditions, there was an increase in active membrane-type (MT)1-MMP but a decrease in MMP-2 protein expression. Plating cells on fibronectin protected against ischemia-induced loss of cadherins and, interestingly, no increase in active MT1-MMP levels was seen in ischemic cells on fibronectin-coated dishes. In addition, L cells stably expressing E- (LE) or N-cadherin (LN), but lacking MT1-MMP expression, were resistant to ischemia-induced cadherin loss. The role of MT1-MMP in ischemia-induced cadherin loss was confirmed by either blocking MT1-MMP activity with a neutralizing antibody or expression with shRNA constructs which protected full-length E- and N-cadherin during ischemia. Using shRNA constructs to suppress MT1-MMP expression, ischemia-induced disruption of cadherin function was ablated, and cell-cell contacts were preserved. These results demonstrate that ischemia induces increased expression of active MT1-MMP and subsequent disruption of cadherin/catenin complexes, implying that MT1-MMP plays a role in ischemia-induced ARF.

Matrix metalloproteinases and their function in myocardium

A significant number of myocardial diseases are accompanied by increased synthesis and degradation of the extracellular matrix (ECM) as well as by changed maturation and incorporation of ECM components. Important groups of enzymes responsible for both normal and pathological processes in ECM remodeling are matrix metaloproteinases (MMPs). These enzymes share a relatively conserved structure with a number of identifiable modules linked to their specific functions. The most important function of MMPs is the ability to cleave various ECM components; including such rigid molecules as fibrillar collagen molecules. The amount and activity of MMPs in cardiac tissue are regulated by a range of activating and inhibiting processes. Although MMPs play multifarious roles in many myocardial diseases, here we have focused on their function in ischemic cardiac tissue, dilated cardiomyopathy and hypertrophied cardiac tissue. The inhibition of MMPs by means of synthetic inhibitors seems to be a promising strategy in cardiac disease treatment. Their effects on diseased cardiac tissue have been successfully tested in several experimental studies.