Matrix metalloproteinase-2 in a murine model of infantile-type polycystic kidney disease

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.

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.

Effects of PEP-1-FK506BP on cyst formation in polycystic kidney disease

Polycystic kidney disease (PKD) is one of the most common inherited disorders, involving progressive cyst formation in the kidney that leads to renal failure. FK506 binding protein 12 (FK506BP) is an immunophilin protein that performs multiple functions, including regulation of cell signaling pathways and survival. In this study, we determined the roles of PEP-1-FK506BP on cell proliferation and cyst formation in PKD cells. Purified PEP-1-FK506BP transduced into PKD cells markedly inhibited cell proliferation. Also, PEP-1-FK506BP drastically inhibited the expression levels of p-Akt, p-p70S6K, p-mTOR, and p-ERK in PKD cells. In a 3D-culture system, PEP-1-FK506BP significantly reduced cyst formation. Furthermore, the combined effects of rapamycin and PEP-1-FK506BP on cyst formation were markedly higher than the effects of individual treatments. These results suggest that PEP-1-FK506BP delayed cyst formation and could be a new therapeutic strategy for renal cyst formation in PKD. [BMB Reports 2017; 50(9): 460-465].

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.

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.

Urinary biomarkers of kidney diseases in HIV-infected children

A significant number of children infected with the human immunodeficiency virus 1 (HIV-1) virus all over the world are at risk of developing renal diseases that could have a significant impact on their treatment and quality of life. It is necessary to identify children undergoing the early stages of these renal diseases, as well as the potential renal toxicity that could be caused by antiretroviral drugs, in order to prevent the development of cardiovascular complications and chronic renal failure. This article describes the most common renal diseases seen in HIV-infected children, as well as the value and limitations of the clinical markers that are currently being used to monitor their renal function and histological damage in a noninvasive manner. In addition, we discuss the progress made during the last 10 years in the discovery and validation of new renal biomarkers for HIV-infected children and young adults. Although significant progress has been made during the early phases of the biomarkers discovery, more work remains to be done to validate the new biomarkers in a large number of patients. The future looks promising, however, the new knowledge needs to be integrated and validated in the context of the clinical environment where these children are living.

Cysts and swellings: a systematic review of the association between polycystic kidney disease and abdominal aortic aneurysm

BACKGROUND

Whether abdominal aortic aneurysm (AAA) forms part of the extrarenal manifestations of autosomal-dominant polycystic kidney disease (ADPKD) is unclear. We set out to review the evidence for an association.

MATERIALS AND METHODS

PubMed, Medline, Embase, and Web of Science databases 1960-2011 were searched [abdominal aortic aneurysm OR AAA OR triple A] AND [polycystic kidney disease OR PKD OR ADPKD OR Renal Cysts]. No limitations were placed on article type or language. Reference lists were recursively searched as were pertinent journal contents.

RESULTS

Eighteen papers were included. Since the first documented case of ADPKD and AAA in 1980, there have been 23 case reports. The voluminous kidneys make AAA diagnosis challenging and surgical exposure difficult. Two studies have assessed aortic diameter in patients with ADPKD and controls, one finding increased aortic diameter in ADPKD (2.7 cm vs. 2.3 cm, P < 0.02) and the other finding no difference. A further study identified a higher incidence of renal cysts in patients with AAA compared to controls (54% vs. 30%, P = 0.0006).

CONCLUSION

There is not enough clinical evidence to determine if ADPKD and AAA share a common pathology. Larger multicenter trials are required to determine if a link exists.

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.

Swimming exercise prevents fibrogenesis in chronic kidney disease by inhibiting the myofibroblast transdifferentiation

Background

The renal function of chronic kidney disease (CKD) patients may be improved by a number of rehabilitative mechanisms. Swimming exercise training was supposed to be beneficial to its recovery.

Methodology/Principal Findings

Doxorubicin-induced CKD (DRCKD) rat model was performed. Swimming training was programmed three days per week, 30 or 60 min per day for a total period of 11 weeks. Serum biochemical and pathological parameters were examined. In DRCKD, hyperlipidemia was observed. Active mesangial cell activation was evidenced by overexpression of PDGFR, P-PDGFR, MMP-2, MMP-9, α-SMA, and CD34 with a huge amount collagen deposition. Apparent myofibroblast transdifferentiation implicating fibrogenesis in the glomerular mesangium, glomerulonephritis and glomeruloscelorosis was observed with highly elevated proteinuria and urinary BUN excretion. The 60-min swimming exercise but not the 30 min equivalent rescued most of the symptoms. To quantify the effectiveness of exercise training, a physical parameter, i.e. “the strenuosity coefficient” or “the myokine releasing coefficient”, was estimated to be 7.154×10⁻³ pg/mL-J.

Conclusions

The 60-min swimming exercise may ameliorate DRCKD by inhibiting the transdifferentiation of myofibroblasts in the glomerular mesangium. Moreover, rehabilitative exercise training to rescue CKD is a personalized remedy. Benefits depend on the duration and strength of exercise, and more importantly, on the individual physiological condition.

Ferulic acid is nephrodamaging while gallic acid is renal protective in long term treatment of chronic kidney disease

BACKGROUNDS & AIMS

The long term therapeutic effect of ferulic acid (FA) and gallic acid (GA) in treatment of chronic kidney disease (CKD) has been lacking.

METHODS

Doxorubicin (DR, Adriamycin)-induced CKD rat model was established for this study.

RESULTS

DR significantly reduced levels of serum albumin, GOT, GPT, RBC, TNF-α, and urinary creatinine and elevated serum cholesterol, TG, BUN, creatinine, uric acid, WBC, platelet count, and IL-6. In DRCKD rats, FA and GA significantly increased kidney weight and glomerular volume. FA reduced glomerular filtration rate but GA did not. FA enhanced more collagen deposition than GA in renal cortex and glomeruli. Both FA and GA showed crucial hyperlipidemic activity. The inhibitory effects of FA and GA on MMP-2 were very comparable. GA suppressed MMP-2 more effectively than FA in DRCKD rats. Both FA and GA induced SOD elevation and MDA elimination. In DRCKD rats, Western blot analysis indicated that FA further up-regulated CD34, α-SMA, tissue pDGFR, p-PDGFR, and TGF-β; and down-regulated p-PI3K, and p-Akt. Since both PDGF-BB and TGF-β are considered to induce kidney prefibrosis stage, GA was proved to be more beneficial in this regard.

CONCLUSIONS

GA tends to protect the CKD while FA is not recommended for the long term CKD therapy.

Evaluation of metalloprotease inhibitors on hypertension and diabetic nephropathy

This study examined the effects of two new selective metalloprotease (MMP) inhibitors, XL081 and XL784, on the development of renal injury in rat models of hypertension, Dahl salt-sensitive (Dahl S) and type 2 diabetic nephropathy (T2DN). Protein excretion rose from 20 to 120 mg/day in Dahl S rats fed a high-salt diet (8.0% NaCl) for 4 wk to induce hypertension. Chronic treatment with XL081 markedly reduced proteinuria and glomerulosclerosis, but it also attenuated the development of hypertension. To determine whether an MMP inhibitor could oppose the progression of renal damage in the absence of changes in blood pressure, Dahl S rats were fed a high-salt diet (4.0% NaCl) for 5 wks to induce renal injury and then were treated with the more potent and bioavailable MMP inhibitor XL784 either given alone or in combination with lisinopril and losartan. Treatment with XL784 or the ANG II blockers reduced proteinuria and glomerulosclerosis by ~30% and had no effect on blood pressure. Proteinuria fell from 150 to 30 mg/day in the rats receiving both XL784 and the ANG II blockers, and the degree of renal injury fell to levels seen in normotensive Dahl S rats maintained from birth on a low-salt diet. In other studies, albumin excretion rose from 125 to >200 mg/day over a 4-mo period in 12-mo-old uninephrectomized T2DN rats. In contrast, albumin excretion fell by >50% in T2DN rats treated with XL784, lisinopril, or combined therapy. XL784 reduced the degree of glomerulosclerosis in the T2DN rats to a greater extent than lisinopril, and combined therapy was more effective than either drug alone. These results indicate that chronic administration of a selective MMP inhibitor delays the progression, and may even reverse hypertension and diabetic nephropathy.

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.

A urinary biomarker profile for children with HIV-associated renal diseases

Human immunodeficiency virus (HIV)-infected children are at risk of developing several types of renal diseases, including HIV-associated nephropathy (HIVAN), which is usually seen during late stages of infection in children with a high viral load. This disease is defined by the presence of proteinuria associated with mesangial hyperplasia and/or global-focal segmental glomerulosclerosis combined with microcystic transformation of the renal tubules. Because HIVAN can have an insidious clinical onset, renal biopsy is the only definitive way of establishing a diagnosis. Given the risk of performing this procedure in HIV-infected children with other AIDS-defining illness, we sought to identify informative biomarkers such as growth factors in the urine of 55 HIV-infected children that might be predictive of the extent and activity of the renal lesions characteristic of HIVAN. We found that the levels of epidermal growth factor were lower in the urine of children with renal disease, whereas levels of fibroblast growth factor-2 and metalloproteinase-2 were higher as compared with those levels in infected children without renal disease. Similar changes were observed in HIV-Tg26 mice correlating with the progression of renal disease in this model of HIVAN. Our findings suggest that this urinary growth factor profile may be useful in facilitating the diagnosis of HIV-infected children at risk of developing HIVAN when interpreted in the appropriate clinical setting.

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.

Matrix metalloproteinases synthesized in autosomal dominant polycystic kidney disease play a role in development of a concurrent abdominal aortic aneurysm

Abdominal aortic aneurysm is well known to be associated with autosomal dominant polycystic kidney disease. Kidney tubules of autosomal dominant polycystic kidney disease synthesize and secrete high levels of matrix metalloproteinase 2, 3, and 9, especially matrix metalloproteinase 2, and serum matrix metalloproteinase 1 and plasma matrix metalloproteinase 9 concentrations in the disease are significantly higher than those in healthy controls. On the other hand, matrix metalloproteinases play a crucial role in the pathogenesis of abdominal aortic aneurysm. Inflammatory cell expression of matrix metalloproteinase 9 plays a critical role in an experimental model of aortic aneurysm disease. Macrophage-derived matrix metalloproteinase 9 and mesenchymal cell matrix metalloproteinase 2 are both required and work in concert to produce abdominal aortic aneurysm. The plasma matrix metalloproteinase 9 levels are significantly higher in the patients with abdominal aortic aneurysm than in the patients with aortoiliac occlusive disease or the healthy patients. Remarkably elevated matrix metalloproteinase 2 mRNA and protein levels in abdominal aortic aneurysm tissues as compared with normal and atherosclerotic aortic tissues are detected, and matrix metalloproteinase 2 proteolytic activity is several-fold higher in abdominal aortic aneurysms than in other pathological or normal states. Patients with abdominal aortic aneurysm elevate matrix metalloproteinase 2 levels in the vasculature remote from the aorta, supporting both the systemic nature of aneurysmal disease and a primary role of matrix metalloproteinase 2 in aneurysm formation. The authors propose a novel hypothesis that matrix metalloproteinases, synthesized and secreted by kidney tubules of autosomal dominant polycystic kidney disease, play a critical role in development of a concurrent abdominal aortic aneurysm.

Activation of the MEK5/ERK5 cascade is responsible for biliary dysgenesis in a rat model of Caroli's disease

Polycystic kidney (PCK) rats exhibit a multiorgan cyst pathology similar to human autosomal recessive polycystic kidney disease, and are proposed as an animal model of Caroli's disease with congenital hepatic fibrosis (CHF). This study investigated the expression and function of selected components of the mitogen activated protein kinase (MAPK) pathway in cultured intrahepatic biliary epithelial cells (BECs) of PCK rats. Compared to the proliferative activity of cultured BECs of control rats, those of the PCK rats were hyperresponsive to epidermal growth factor (EGF). The increase in BEC proliferation was accompanied by overexpression of MAPK/extracellular signal-regulated protein kinase (ERK) kinase 5 (MEK5), and subsequent phosphorylation of ERK5 in vitro. The increased proliferative activity was significantly inhibited by the transfection of short interfering RNA against MEK5 mRNA. An EGF receptor tyrosine kinase inhibitor, gefitinib ("Iressa", ZD1839), also significantly inhibited the abnormal growth of cultured BECs of PCK rats. By contrast, treatment with PD98059 and U0126, inhibitors for MEK1/2, was less effective. These results suggest that the activation of the MEK5-ERK5 cascade plays a pivotal role in the biliary dysgenesis of PCK rats, and also provide insights into the pathogenesis of Caroli's disease with CHF. As the MEK5-ERK5 interaction is highly specific, it may represent a potential target of therapy.

Recent advances in understanding the pathogenesis of polycystic kidney disease: therapeutic implications

Hereditary polycystic kidney disease (PKD) is a common cause of renal failure. Increasing knowledge is available regarding mechanisms of cyst development and progression, and renal functional deterioration in PKD. On the basis of this information and theories regarding the pathophysiology of these processes, studies to alter progression and potentially treat PKD have been reported. Cyst development and progression requires epithelial cell proliferation, transepithelial fluid secretion and extracellular matrix remodelling. Several interventions designed to inhibit cell proliferation or alter fluid secretion modify the progression of PKD in selected animal models. Renal functional deterioration appears to involve interstitial inflammation and fibrosis, and tubular apoptosis. Glucocorticoids with anti-inflammatory and antifibrotic properties slow the progression of cystic disease and renal functional deterioration in animal models of PKD. Other interventions, such as dietary modification and angiotensin antagonism, shown to be of benefit in non-PKD models of slowly progressive renal disease, are also of benefit in animal models of PKD. Caution should be used in extrapolating interventional studies in one animal model to another model and certainly to human disease, since examples exist in which treatments in one model of PKD have different effects in another model. Nonetheless, early attempts to determine whether potential treatments are tolerated and of potential benefit in patients with PKD are beginning to appear. Ultimately, treatment of PKD may involve efforts to identify patients at greatest risk for disease progression, thus allowing targeted therapy, use of surrogate markers for disease progression to assist assessment of therapeutic efficacy, and combination therapy to retard disease progression and renal functional deterioration in this common hereditary cause of chronic renal failure.

Angiostatin and matrix metalloprotease expression following ischemic acute renal failure

Ischemic injury to the kidney results in blood vessel loss and predisposition to chronic renal disease. Angiostatin is a proteolytic cleavage product of plasminogen that inhibits angiogenesis, promotes apoptosis of endothelial cells, and disrupts capillary integrity. A combination of lysine-Sepharose enrichment followed by Western blotting was used to study the expression of angiostatin in response to the induction of ischemic renal injury. No angiostatin products were readily detectable in kidneys of sham-operated control rats. In contrast, both 38- and 50-kDa forms of angiostatin were dramatically enhanced in the first 3 days following 45-min ischemia-reperfusion injury. Renal angiostatin levels declined but remained detectable at late time points postrecovery (8–35 days postischemia). Angiostatin-like immunoreactivity was also elevated in the plasma and in urine for up to 35 days following injury. Lysine-Sepharose extracts of either kidney or urine inhibited vascular endothelial cell growth factor-induced proliferation of human aortic endothelial cells in vitro; an effect that was blocked by coincubation with an angiostatin antibody. RT-PCR verified that mRNA of the parent protein plasminogen was produced in the liver, but it was not present in either sham-operated or postischemic kidney. Matrix metalloproteinase (MMP)-2 and MMP-9, which may mediate angiostatin generation, were enhanced in postischemic kidney tissue and were localized to the renal tubules, interstitial cells, and the tubulo-interstitial space. These data indicate the possible local synthesis of angiostatin following acute renal failure (ARF) and suggest a possible role for MMPs in this activity. Renal angiostatin generation following ARF may modulate renal capillary density postischemia and thereby influence chronic renal function.

Matrix metalloproteinase-9 and tissue inhibitor of metalloproteinases-1 in acute pyelonephritis and renal scarring

The aim of the present study was to elucidate the role of matrix metalloproteinase-9 (MMP-9), and its main inhibitor tissue inhibitor of metalloproteinases-1 (TIMP-1), in acute pyelonephritis and the process of renal scarring. Urine samples from 40 children with acute pyelonephritis, 16 children at 6-wk follow-up and 15 children with nonrenal fever were analyzed using ELISA. MMP-9 and TIMP-1 levels were compared with the outcome of pyelonephritis as measured by renal static scintigraphy. A mouse model of acute ascending pyelonephritis was used to localize the sites of production and the kinetics of MMP-9 and TIMP-1 using immunohistochemistry and ELISA. Human renal epithelial A498 cells, primary mesangial cells and monocytic THP-1 cells were stimulated by Escherichia coli. MMP-9 and TIMP-1 mRNA was analyzed by reverse transcription-PCR (RT-PCR) and protein production by ELISA. We demonstrate a significant increase of MMP-9 and TIMP-1 in the urine of children with acute pyelonephritis. Both proteins were produced mainly by leukocytes, and TIMP-1 also by resident kidney cells. Cells reacted differently after stimulation by bacteria. In mesangial cells and monocytes a decreased constitutive TIMP-1 production was found, which was in contrast to epithelial cells. Out of 40 children with pyelonephritis, 23 had higher urinary TIMP-1 than MMP-9 levels. These children had significantly more severe changes in both acute and follow-up scintigraphy scans indicating higher degree of acute tissue damage and renal scarring. Thus, our findings suggest an association between TIMP-1 and the process of renal scarring.

Multiorgan mRNA misexpression in murine autosomal recessive polycystic kidney disease

BACKGROUND

BALB/c mice homozygous for the cpk mutation develop a form of polycystic kidney disease (PKD) with multiorgan pathology similar to human autosomal recessive PKD. Messenger RNA expression in multiple affected organs was analyzed to determine if common gene cascades were misexpressed in the cystic kidney and extrarenal sites of disease. In cystic kidneys, misexpressed mRNAs were found in one of four general groups: proliferation/cell growth, apoptosis, differentiation or extracellular matrix.

METHODS

RNA was isolated from kidney, liver and pancreas of cystic and normal BALB/c-cpk mice. Using Northern blot hybridization and ribonuclease protection assays (RPA), the expression of several genes thought to be associated with PKD, namely c-myc, epidermal growth factor receptor (EGF-R) and PKD-1, were evaluated. RPAs were used to assess mRNA expression of cyclins and members of the bax/bcl-2 family. In addition, kidney, liver and pancreas were immunostained for c-Myc and PCNA.

RESULTS

Cystic kidney, liver and pancreas all exhibited similar patterns of mRNA misexpression of c-myc, EGF-R and PKD-1. In addition, a number of cell proliferation and apoptosis-related mRNAs also were elevated in cystic kidney and pancreas. Renal epithelial cells expressing proliferation-associated proteins [c-Myc and proliferating cell nuclear antigen (PCNA)] were nearly absent in normal kidney; however, cells of cystic and non-cystic renal tubules plus liver and pancreatic cyst exhibited an increased number of nuclei labeled with antibodies to these proteins.

CONCLUSIONS

These data suggest that similar pathologic mechanisms (including the expression of c-myc, EGF-R, PKD-1, cyclin, and bax/bcl-2 family mRNAs) may be responsible for the development of cystic changes in kidney, liver and pancreas in murine autosomal recessive PKD. Treatments targeting these similarly misexpressed mRNAs may be efficacious in ameliorating the cystic pathology in the kidney as well as the other affected organs in ARPKD.

A novel inhibitor of tumor necrosis factor-alpha converting enzyme ameliorates polycystic kidney disease

BACKGROUND

Transforming growth factor-alpha (TGF-alpha) expression is abnormal in polycystic kidney disease. We previously demonstrated that blockade of the epidermal growth factor receptor (EGFR), the receptor for TGF-alpha, significantly slowed disease progression in the bpk murine model of autosomal-recessive kidney disease (ARPKD). In the present study, kidney TGF-alpha expression in this model is characterized, and the therapeutic potential of inhibiting TGF-alpha in ARPKD is examined using a novel inhibitor of tumor necrosis factor-alpha converting enzyme (TACE), the metalloproteinase that cleaves membrane-bound TGF-alpha to release the secreted ligand.

METHODS

Immunohistochemistry (IH) and Western analysis were performed on kidneys from cystic bpk mice and noncystic littermates at postnatal days 7, 14, and 21. Bpk mice and normal controls were treated with WTACE2, a competitive inhibitor of TACE, from day 7 until day 21, and the effects on kidney histology and renal function were assessed.

RESULTS

Increased TGF-alpha expression by IH was demonstrated in the proximal tubules (PT) at postnatal day 7 and collecting tubules (CT) by day 21. A parallel increase in kidney TGF-alpha expression was demonstrated by Western analysis. Treatment of cystic bpk mice with WTACE2 resulted in a 43% reduction in kidney weight to body weight ratio (11.2 vs. 19.7%), improved cystic index (3.2 vs. 4.8), reduced cystic CT to PT ratio (1.2 vs. 8), and a greater than 30% reduction in BUN and serum creatinine.

CONCLUSIONS

These findings support the pathophysiological role of the TGF-alpha/EGFR axis in murine ARPKD and demonstrate that inhibition of TGF-alpha secretion has therapeutic potential in PKD.

Angiogenesis in autosomal-dominant polycystic kidney disease

BACKGROUND

Autosomal-dominant polycystic kidney disease (ADPKD) is a genetic disorder that is responsible for approximately 10% of all cases of end-stage renal disease (ESRD). It is characterized by the formation of epithelial cell cysts, an increase in the extracellullar matrix, and vascular alterations believed to be the result of compression by the cysts. Our recent observations demonstrated a rich vascular network on the surface of the cysts, and thus, we postulated that angiogenesis could be a factor in the progression of ADPKD.

METHODS

Kidneys removed from patients with ADPKD were studied using (1) angiographs, (2) immunostaining [factor VIII-related antigen, vascular endothelial growth factor (VEGF), VEGF receptors 1 and 2 (VEGFR-1 and VEGFR-2), metalloproteinase-2 (MMP-2), and integrin alphavbeta3], and (3) Western blot analysis and enzyme-linked immunosorbent assay. The expression of VEGF165 in ADPKD cells in culture was determined.

RESULTS

There was (1) an extensive capillary network in the cyst wall of ADPKD kidneys, (2) morphological evidence of vascular malformations, (3) expression of VEGF165 in cyst cells of VEGFR-2 in endothelial cells and an absence of VEGFR-1 in endothelial cells, (4) secretion of VEGF165 by ADPKD cyst cells in culture, and (5) coexpression of matrix MMP-2 and integrin alphavbeta3 in vessels from ADPKD.

CONCLUSIONS

There is angiogenesis in ADPKD. This process may be necessary for cyst cells to grow and may be responsible for increased vascular permeability facilitating fluid secretion into the cysts. Neovascularization may result in the formation of aneurysms responsible for the renal bleeding in this disease.

A possible role for metalloproteinases in renal cyst development

The expansion of cysts in polycystic kidneys bears several similarities to the invasion of the extracellular matrix by benign tumors. We therefore hypothesized that cyst-lining epithelial cells produce extracellular matrix-degrading metalloproteinases and that the inhibition of these enzymes may represent a potential target for therapeutic intervention. Using in situ hybridization, we first analyzed the expression of membrane-type metalloproteinase 1 (MMP-14), an essential matrix metalloproteinase, of its inhibitor TIMP-2, and of the cytokine transforming growth factor (TGF)-beta2 in the (cy/+) rat model of autosomal-dominant polycystic kidney disease. Upregulated MMP-14 mRNA was predominantly located in cyst-lining epithelia and distal tubules, whereas TIMP-2 mRNA was confined almost exclusively to fibroblasts. TGF-beta2, a cytokine known to regulate the expression of matrix metalloproteinases and their inhibitors, was also expressed by cyst wall epithelia. We then treated (cy/+) rats with the metalloproteinase inhibitor batimastat for a period of 8 wk. The treatment with the metalloproteinase inhibitor batimastat resulted in a significant reduction of cyst number and kidney weight. Our study suggests that metalloproteinase inhibitors represent a new therapeutic tool against polycystic kidney disease, which should be applicable independently of the background of the disease.