The potential of matrix metalloproteinase-2 as a marker of peritoneal injury, increased solute transport, or progression to encapsulating peritoneal sclerosis during peritoneal dialysis--a multicentre study in Japan

Intraperitoneal MASP-1 Levels are Associated with Peritoneal Solute Transport Rate in Peritoneal Dialysis Patients: A Retrospective Cohort Study

Purpose

A major limitation of long-term peritoneal dialysis (PD) is peritoneal membrane dysfunction characterized by faster peritoneal solute-transport rate (PSTR). This study aimed to identify efficient complement factors in peritoneal effluents of continuous ambulatory peritoneal dialysis (CAPD) patients that can predict the PSTR.

Methods

A multiplex suspension protein array was used to screened related complement pathways in overnight peritoneal effluents among 58 CAPD patients. Then the related complement factors in lectin and classical pathways in effluents were analyzed using ELISA kits among another cohort of 129 CAPD patients. Logistic regression modeling was fitted to predict the PSTR of PD patients.

Results

The multiplex suspension protein array showed complement factors including C2, C4b, C5, C5a, Factor D, Factor I, and MBL were detected in effluents of CAPD patients, and the effluent C2 Appearance rate (Ar) and C4b Ar levels were significantly correlated with D/P Cr and D/D0 glucose. The levels of effluents MASP-1 Ar, M-Ficolin Ar, C2 Ar and C4b Ar, which belong to the lectin pathway were also positively correlated with D/P Cr according the ELISA results and these parameters were expressed higher in the high and high-average (H/HA) groups according to the PET results. Moreover, effluent Masp-1 was independently associated with increased PSTR and adverse events related peritoneal transport function failure.

Conclusion

This study suggested that the lectin pathway may be involved in local complement activation and peritoneal injury of PD patients, intraperitoneal level of Masp-1 was an independent predictor of increased PSTR in PD patients.

BRG1 accelerates mesothelial cell senescence and peritoneal fibrosis by inhibiting mitophagy through repression of OXR1

Peritoneal mesothelial cell senescence promotes the development of peritoneal dialysis (PD)-related peritoneal fibrosis. We previously revealed that Brahma-related gene 1 (BRG1) is increased in peritoneal fibrosis yet its role in modulating peritoneal mesothelial cell senescence is still unknown. This study evaluated the mechanism of BRG1 in peritoneal mesothelial cell senescence and peritoneal fibrosis using BRG1 knockdown mice, primary peritoneal mesothelial cells and human peritoneal samples from PD patients. The augmentation of BRG1 expression accelerated peritoneal mesothelial cell senescence, which attributed to mitochondrial dysfunction and mitophagy inhibition. Mitophagy activator salidroside rescued fibrotic responses and cellular senescence induced by BRG1. Mechanistically, BRG1 was recruited to oxidation resistance 1 (OXR1) promoter, where it suppressed transcription of OXR1 through interacting with forkhead box protein p2. Inhibition of OXR1 abrogated the improvement of BRG1 deficiency in mitophagy, fibrotic responses and cellular senescence. In a mouse PD model, BRG1 knockdown restored mitophagy, alleviated senescence and ameliorated peritoneal fibrosis. More importantly, the elevation level of BRG1 in human PD was associated with PD duration and D/P creatinine values. In conclusion, BRG1 accelerates mesothelial cell senescence and peritoneal fibrosis by inhibiting mitophagy through repression of OXR1. This indicates that modulating BRG1-OXR1-mitophagy signaling may represent an effective treatment for PD-related peritoneal fibrosis.

Melatonin inhibits the formation of chemically induced experimental encapsulating peritoneal sclerosis through modulation of T cell differentiation by suppressing of NF-κB activation in dendritic cells

Encapsulating peritoneal sclerosis (EPS) is a severe complication of peritoneal dialysis (PD). Surgery is a therapeutic strategy for the treatment of complete intestinal obstruction. However, complete intestinal obstruction in long-term PD results in high mortality and morbidity rates after surgery. Immunopathogenesis participates in EPS formation: CD8, Th1, and Th17 cell numbers increased during the formation of EPS. The anti-inflammatory and immunomodulatory effects of melatonin may have beneficial effects on this EPS. In the present study, we determined that melatonin treatment significantly decreases the Th1 and Th17 cell populations in mice with EPS, decreases the production of IL-1β, TNF-α, IL-6, and IFN-γ, and increases the production of IL-10. The suppression of Th1 and Th17 cell differentiation by melatonin occurs through the inhibition of dendritic cell (DC) activation by affecting the initiation of the NF-κB signaling pathway in DCs. Our study suggests that melatonin has preventive potential against the formation of EPS in patients with PD.

Peritoneal Dialysis Guidelines 2019 Part 1 (Position paper of the Japanese Society for Dialysis Therapy)

Approximately 10 years have passed since the Peritoneal Dialysis Guidelines were formulated in 2009. Much evidence has been reported during the succeeding years, which were not taken into consideration in the previous guidelines, e.g., the next peritoneal dialysis PD trial of encapsulating peritoneal sclerosis (EPS) in Japan, the significance of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs), the effects of icodextrin solution, new developments in peritoneal pathology, and a new international recommendation on a proposal for exit-site management. It is essential to incorporate these new developments into the new clinical practice guidelines. Meanwhile, the process of creating such guidelines has changed dramatically worldwide and differs from the process of creating what were “clinical practice guides.” For this revision, we not only conducted systematic reviews using global standard methods but also decided to adopt a two-part structure to create a reference tool, which could be used widely by the society’s members attending a variety of patients. Through a working group consensus, it was decided that Part 1 would present conventional descriptions and Part 2 would pose clinical questions (CQs) in a systematic review format. Thus, Part 1 vastly covers PD that would satisfy the requirements of the members of the Japanese Society for Dialysis Therapy (JSDT). This article is the duplicated publication from the Japanese version of the guidelines and has been reproduced with permission from the JSDT.

Effluent Osteopontin levels reflect the peritoneal solute transport rate

Long-term peritoneal dialysis (PD) is accompanied by low-grade intraperitoneal inflammation and may eventually lead to peritoneal membrane injury with a high solute transport rate and ultrafiltration failure. Osteopontin (OPN) is highly expressed through the stimulation of pro-inflammatory cytokines in many cell types. This study aimed to investigate the potential of OPN as a new indicator of peritoneal deterioration. One hundred nine continuous ambulatory PD patients were analyzed. The levels of OPN and IL-6 in peritoneal effluents or serum were analyzed by ELISA kits. The mean effluent OPN concentration was 2.39 ± 1.87 ng/mL. The OPN levels in drained dialysate were correlated with D/P Cr (p < 0.0001, R = 0.54) and D/D0 glucose (p < 0.0001, R = 0.39). Logistic regression analysis showed that the OPN levels in peritoneal effluents were an independent predictive factor for the increased peritoneal solute transport rate (PSTR) obtained by the peritoneal equilibration test (p < 0.001). The area under the receiver operating characteristic curve of OPN was 0.84 (95% CI: 0.75-0.92) in predicting the increased PSTR with a sensitivity of 86% and a specificity of 67%. The joint utilization of effluent OPN with age, effluent IL-6, and serum albumin further increased the specificity (81%). Thus, OPN may be a useful indicator of peritoneal deterioration in patients with PD.

A Matrix Metalloproteinase-2-Based Nomogram to Assess the Risk of Encapsulating Peritoneal Sclerosis in Peritoneal Dialysis Patients

Background

Encapsulating peritoneal sclerosis (EPS) is a rare but serious complication of peritoneal dialysis (PD). So far, there is no biomarker-based prediction tool available for EPS. Matrix metalloproteinase-2 (MMP-2) is a protein involved in the breakdown of the extracellular matrix, and the effluent MMP-2 can be a potential biomarker of EPS. This study is aimed at developing a nomogram for EPS based on effluent MMP-2 levels. Patients and Methods. We enrolled 18 EPS patients and 90 gender-matched PD patients without EPS in this cross-sectional case-controlled study. The effluent MMP-2 levels and possible risk factors for EPS were analyzed using multivariable logistic regression, and a nomogram was developed. The nomogram was validated using 200 bootstrap resamples to reduce overfit bias.

Results

The effluent MMP-2 levels in EPS patients were significantly higher than those in normal PD patients (p < 0.001, Manny-Whitney U test). Effluent MMP-2 levels and PD duration were independently associated with EPS risks (p < 0.001 and p = 0.001) in multivariate logistic regression. A nomogram based on MMP-2 levels and PD duration was proposed. The AUC of MMP-2 was 0.824, and the AUC of the nomogram was 0.907 (p = 0.05).

Conclusion

A nomogram based on effluent MMP-2 levels and PD duration may predict EPS with high accuracy.

Clinical risk factors and outcomes of massive ascites accumulation after discontinuation of peritoneal dialysis

Background: Encapsulating peritoneal sclerosis (EPS) is a serious complication of peritoneal dialysis (PD), with high morbidity and mortality that requires an early diagnosis for effective treatment. PD withdrawal and bacterial peritonitis are important triggers for the onset of EPS. However, few studies have focused on cases of PD withdrawal without a clinical diagnosis of peritonitis, cirrhosis, or carcinomatosis. We aimed to compare the clinical characteristics and computed tomography (CT) images of patients with or without ascites in such situations and assess clinical outcomes in terms of mortality.Methods: Our retrospective review included 78 patients who withdraw PD between January 2000 and December 2017.Results: Ten patients had ascites, and 68 did not have a significant intra-abdominal collection. The ascites group had a significantly longer PD duration (months; 134.41 [range, 35.43-181.80] vs. 32.42 [733-183.47], p < 0.001) and higher peritoneal membrane transport status based on the dialysate-to-plasma ratios of creatinine (0.78 ± 0.08 vs. 0.68 ± 0.11, p = 0.009) and glucose (0.27 ± 0.07 vs. 0.636 ± 0.08, p = 0.001) than the control group. CT parameters, including peritoneal calcification, thickness, bowel tethering, or bowel dilatation, were not all present in each patient with ascites and EPS. During the 12-month study period, the ascites group had a higher risk for developing EPS (70% vs. 0%, p < 0.001) and a higher 12-month all-cause mortality (30% vs. 0%, p = 0.002).Conclusions: Ascites accumulation was not rare after PD discontinuation. A longer PD duration and high peritoneal membrane transport status could predict subsequent ascites accumulation. Furthermore, patients with ascites were at a higher risk of EPS.

The effect of rituximab on encapsulated peritoneal sclerosis in an experimental rat model

Background/aim

 Peritoneal sclerosis may be observed in varied manifestations. However, the most serious form is the encapsulated peritoneal sclerosis. We researched the effect of rituximab on peritoneal fibrosis in an experimental rat model.

Materials and methods

Twenty-four Wistar Albino rats were divided into 4 equal groups. During weeks 0–3; group I received isotonic saline (IS) solution, group II, group III, and group IV received chlorhexidine gluconate (CG) via intraperitoneal (i.p.) route. In the next 3 weeks nothing adminestred to both group I and group II but IS solution was adminestred to group III via i.p. route and 375 mg/m2/week rituximab was applied intravenously on days 21, 28, and 35 to group IV. Fibrosis, peritoneal thickness, and inflammation were evaluated. Immunohistochemical methods used for the detection of matrix MMP-2, TGF-β1, and VGEF expressions.

Results

  The rituximab (group IV) had significantly lower fibrosis and peritoneal thickness scores than the group II and III (P < 0.001). TGF-β1 and VEGF expressions were significantly lower in the rituximab group than in the group II and III (P < 0.001).Conclusion: We found that rituximab had a significant effect on the peritoneal thickness, total fibrosis, TGF-β1 and VGEF scores which were induced by CG.

The Role of Cathepsin B in Peritoneal Fibrosis due to Peritoneal Dialysis

Glucose-containing peritoneal dialysis (PD) solution causes peritoneal fibrosis (PF) characterized by accumulation of extracellular matrix (ECM) in the submesothelial layer. Cathepsin B is a lysosomal cysteine protease that degrades ECM, but its role in the PF remains unclear. Thus, we investigated the role of cathepsin B in PF. Procathepsin B was measured in the 73 PD effluents of 68 patients. Procathepsin B and cathepsin B after exposure of glucose and the effects of cathepsin B on the expression of matrix metalloproteinases (MMPs), tissue inhibitor of metalloproteinases (TIMPs), and urokinase-type plasminogen activator (uPA) were measured in the supernatant of cultured human peritoneal mesothelial cells (HPMCs). The effect of cathepsin B and its inhibitor, cystatin C, on PF was investigated in the murine model. Procathepsin B was measured at 3.6 μg/L in serum and 5.4 μg/L in PD effluent and positively correlated to the cancer antigen (CA) 125. The treatment with 4.25% glucose increased procathepsin B by 3.1-fold and cathepsin B by 5.9-fold in the HPMCs. Cathepsin B induced the secretion of MMP-1, -2, and -3 and TIMP-1 in the HPMCs, but uPA was not excreted. In the PF murine models, cathepsin B reduced the thickness of the submesothelial layer and cystatin C attenuated the effect of cathepsin B. HPMCs secrete cathepsin B with exposure of PD solution, and cathepsin B might help protect against PF.

Adoptive transfer of DMSO-induced regulatory T cells exhibits a similar preventive effect compared to an in vivo DMSO treatment for chemical-induced experimental encapsulating peritoneal sclerosis in mice

Encapsulating peritoneal sclerosis (EPS) is a severe complication of peritoneal dialysis (PD). This disease leads to intestinal obstruction with or without peritonitis. The imbalance between the populations of Th17 and regulatory T (Treg) cells (higher Th17 cells and lower Treg cells) is part of the pathogenesis of EPS formation. We demonstrated that dimethyl sulfoxide (DMSO) effectively inhibited autoimmune diabetes recurrence in the islet transplantation of NOD mice via the induction of the differentiation of Treg cells. In this study, we investigated the therapeutic potential of DMSO in the inhibition of EPS formation by a mouse model. Under DMSO treatment, the thickening of the parietal and visceral peritoneum was significantly reduced. The populations of CD4, CD8, and IFN-γ-producing CD4 and CD8 T cells were decreased. The populations of IL-4-producing CD4 T lymphocytes, IL-10-producing CD4 T lymphocytes, CD4 CD69 T lymphocytes and Treg lymphocytes were increased. The expression levels of the cytokines IFN-γ, IL-17a, TNF-α and IL-23, in ascites, were significantly decreased following the DMSO treatment. Furthermore, the differentiation of Treg cells was induced by DMSO from naïve CD4 T cells in vitro, and these cells were adoptively transferred into the EPS mice and significantly prevented EPS formation, exhibiting a comparable effect to the in vivo DMSO treatment. We also demonstrated that the differentiation of Treg cells by DMSO occurred via the activation of STAT5 by its epigenetic effect, without altering the PI3K-AKT-mTOR or Raf-ERK pathways. Our results demonstrated, for the first time, that in vivo DMSO treatment suppresses EPS formation in a mouse model. Furthermore, the adoptive transfer of Treg cells that were differentiated from naïve CD4 T cells by an in vitro DMSO treatment exhibited a similar effect to the in vivo DMSO treatment for the prevention of EPS formation.

Longitudinal Changes of PAI-1, MMP-2, and VEGF in Peritoneal Effluents and Their Associations with Peritoneal Small-Solute Transfer Rate in New Peritoneal Dialysis Patients

Patients on peritoneal dialysis (PD) encounter peritoneal functional and structural alterations. It is still unknown whether levels of plasminogen activator inhibitor type 1 (PAI-1), matrix metalloproteinases- (MMP-) 2, and vascular endothelial growth factor (VEGF) exhibit dynamic changes in peritoneal effluents. The aim of the present study was to investigate the longitudinal changes in these biomarkers in PD patients and their association with peritoneal small-solute transfer rate (PSTR). This prospective, single-center cohort study included 70 new PD patients. The presence of PAI-1, MMP-2, and VEGF in peritoneal effluents was measured regularly after PD initiation. The association between those biomarkers and 4-hour effluent:plasma creatinine ratio (PSTR) was analyzed. Longitudinal follow-up showed a tendency for PAI-1 (p < 0.001) and VEGF (p = 0.04) to increase with the duration of PD. Both PSTR at baseline and PSTR at 2 years significantly associated with PAI-1, MMP-2, and VEGF levels at baseline. PSTR at 2 years also associated with the MMP-2 level at 6 months and PAI-1 level at baseline. The present study illustrated a positive association of PSTR with selected biomarkers in peritoneal effluents observed over a 2-year period.

The Effects of Darbepoetin on Peritoneal Fibrosis Induced by Chemical Peritonitis and on Peritoneal Tissue Mmp-2 and Timp-2 Levels in Rats

The aim of this study is to assess the influence of darbepoetin on the development of peritoneal fibrosis in rats induced by Chlorhexidine gluconate (0.1%) and ethanol (15%) and to determine the effect on peritoneal tissue levels of MMP–2 and TIMP–2, possible important factors in progression of peritoneal fibrosis. Twenty-four female Wistar albino rats were divided into three groups. The first group (CH group) received 3 ml/200g daily intraperitoneal injections of Chlorhexidine gluconate (0.1%) and ethanol (15%) dissolved in saline to induce chemical peritonitis; group 2 (ESA group) received 3 ml/200g daily injections of Chlorhexidine gluconate (0.1%) and ethanol (15%) dissolved in saline and also darbepoetin 12.5 microgr/ per kilogram/ day subcutaneously on the first and seventh days; group 3 (Control group) received intraperitoneal 0.9% saline (3 ml/200g/d) through the right lower quadrant by 21 gauge needle. The study duration was fourteen days. On the fifteenth day rats were sacrificed, parietal peritoneum samples were obtained from the left anterior abdominal wall. Pathological samples were examined using Hematoxyline & Eosin (HE) stains. The thickness, vasculpathy, and inflammation were determined by light microscopy. MMP-2 and TIMP-2 were studied immunohistochemically by monoclonal antibody staining. The activity of MMP-2 on peritoneal tissue was studied by gelatin zymography and TIMP–2 protein level was analysed by ELISA, biochemically. The decrease in thickness of parietal peritoneum in group ESA was statistically significant when compared to CH group (p<0.05). Inflammation scores, and vascularization score surfaces were not statistically different between these groups (p>0.05). Immunohistochemically, darbepoetin was shown to decrease MMP-2 expression on parietal peritoneum in CH group (p<0.05), but had no effect on TIMP-2 (p>0.05). Biochemically the ratio of active MMP–2 to proMMP–2 was more significantly increased in the ESA group than in the CH group (p<0.001), however, TIMP- 2 levels in both groups were decreased compared to the control group (p<0.05). Darbepoetin histopathologically reduced peritoneal fibrosis induced by Chlorhexidine gluconate. We can suggest that Darbepoetin does not cause peritoneal fibrosis and may prevent peritoneal fibrosis in rats possibly related to an effect on MMP-2 expression. Further research regarding the utility and dosage should be considered.

Matrix metalloproteinase 9 is associated with peritoneal membrane solute transport and induces angiogenesis through β-catenin signaling

Background

For patients using peritoneal dialysis (PD), the peritoneal membrane can develop fibrosis and angiogenesis, leading to ultrafiltration failure, chronic hypervolemia and increased risk of technique failure and mortality. Matrix metalloproteinases (MMPs), and specifically the gelatinases (MMP2 and MMP9), may be involved in peritoneal membrane injury.

Methods

From stable PD patients, mesothelial cells were assayed for MMP gene expression. MMP9 was overexpressed in mouse peritoneum by adenovirus, and MMP9 -/- mice were subjected to transforming growth factor β (TGF-β)-induced peritoneal fibrosis.

Results

MMP9 mRNA expression correlated with peritoneal membrane solute transport properties. Overexpression of MMP9 in the mouse peritoneum induced submesothelial thickening and angiogenesis. MMP9 induced mesothelial cell transition to a myofibroblast phenotype measured by increased alpha smooth muscle actin and decreased E-cadherin expression. Angiogenesis was markedly reduced in MMP9 -/- mice treated with an adenovirus expressing active TGF-β compared with wild-type mice. TGF-β-mediated E-cadherin cleavage was MMP9 dependent, and E-cadherin cleavage led to β-catenin-mediated signaling. A β-catenin inhibitor blocked the angiogenic response induced by AdMMP9.

Conclusions

Our data suggest that MMP9 is involved in peritoneal membrane injury possibly through cleavage of E-cadherin and induction of β-catenin signaling. MMP9 is a potential biomarker for peritoneal membrane injury and is a therapeutic target to protect the peritoneal membrane in PD patients.

Preventing tissue fibrosis by local biomaterials interfacing of specific cryptic extracellular matrix information

Matrix metalloproteinases (MMPs) contribute to the breakdown of tissue structures such as the basement membrane, promoting tissue fibrosis. Here we developed an electrospun membrane biofunctionalized with a fragment of the laminin β1-chain to modulate the expression of MMP2 in this context. We demonstrate that interfacing of the β1-fragment with the mesothelium of the peritoneal membrane via a biomaterial abrogates the release of active MMP2 in response to transforming growth factor β1 and rescues tissue integrity ex vivo and in vivo in a mouse model of peritoneal fibrosis. Importantly, our data demonstrate that the membrane inhibits MMP2 expression. Changes in the expression of epithelial-to-mesenchymal transition (EMT)-related molecules further point towards a contribution of the modulation of EMT. Biomaterial-based presentation of regulatory basement membrane signals directly addresses limitations of current therapeutic approaches by enabling a localized and specific method to counteract MMP2 release applicable to a broad range of therapeutic targets.

Abatacept as a therapeutic option in the treatment of encapsulated peritoneal sclerosis: an experimental rat model

PURPOSE

Encapsulated peritoneal sclerosis (EPS) is a rare complication of long-term peritoneal dialysis (PD) and is usually associated with mortality. Inflammation is a leading factor for developing EPS. This study aimed to investigate the effect of abatacept on peritoneal fibrosis and inflammation using the EPS rat model.

METHODS

Twenty-four Wistar albino rats were randomly divided into four equal groups. Group I (control group) was administered isotonic saline (IS) via the intraperitoneal (ip) route during weeks 0-3. Chlorhexidine gluconate (CG) ip was administered to group II (CG group) during weeks 0-3. Group III (CG + IS group) received CG for the first 21 days and IS solution for the following 3 weeks. Group IV (abatacept group) received CG during weeks 0-3, and subsequently, 50 mcg/day abatacept during weeks 4-6. Peritoneal thickness, fibrosis, and inflammation were examined using light microscopy. Expressions of matrix metalloproteinase-2 (MMP-2) and transforming growth factor-beta 1 (TGF-β1) were detected by immunohistochemical staining.

RESULTS

Lesser peritoneal thickness and lower inflammation score were observed in the abatacept group than in the CG and CG + IS groups (p < 0.05). Furthermore, the abatacept group had a lower fibrosis score than the CG + IS group (p < 0.05). MMP-2 and TGF-β1 scores were lower in the abatacept group than in the CG + IS group (p < 0.05).

CONCLUSIONS

The results revealed that abatacept had a histopathological beneficial effect on peritoneal fibrosis, inflammation, MMP-2, and TGF-β1 scores, which were induced by CG. Abatacept could be a new therapeutic option for treating EPS.

Basement membrane fragments in the context of the epithelial-to-mesenchymal transition

The epithelial-to-mesenchymal transition (EMT) enables cells of epithelial phenotype to become motile and change to a migratory mesenchymal phenotype. EMT is known to be a fundamental requisite for tissue morphogenesis, and EMT-related pathways have been described in cancer metastasis and tissue fibrosis. Epithelial structures are marked by the presence of a sheet-like extracellular matrix, the basement membrane, which is assembled from two major proteins, laminin and collagen type IV. This specialized matrix is essential for tissue function and integrity, and provides an important barrier to the potential pathogenic migration of cells. The profound phenotypic transition in EMT involves the epithelial cells disrupting the basement membrane. Matrix metalloproteinases (MMPs) are known to cleave components of basement membranes, but MMP-basement membrane crosstalk during EMT in vivo is poorly understood. However, MMPs have been reported to play a role in EMT-related processes and a variety of basement membrane fragments have been shown to be released by specific MMPs in vitro and in vivo exhibiting distinct biological activities. This review discusses general considerations regarding the basement membrane in the context of EMT, a possible role for specific MMPs in EMT and highlights biologically active basement membrane fragments liberated by MMPs.

Effluent Tenascin-C Levels Reflect Peritoneal Deterioration in Peritoneal Dialysis: MAJOR IN PD Study

Peritoneal deterioration causing structural changes and functional decline is a major complication of peritoneal dialysis (PD). The aim of this study was to explore effluent biomarkers reflecting peritoneal deterioration. In an animal study, rats were intraperitoneally administered with PD fluids adding 20 mM methylglyoxal (MGO) or 20 mM formaldehyde (FA) every day for 21 days. In the MGO-treated rats, tenascin-C (TN-C) levels in the peritoneal effluents were remarkably high and a cluster of TN-C-positive mesothelial cells with epithelial-to-mesenchymal transition- (EMT-) like change excessively proliferated at the peritoneal surface, but not in the FA-treated rats. Effluent matrix metalloproteinase-2 (MMP-2) levels increased in both the MGO- and FA-treated rats. In a clinical study at 18 centers between 2006 and 2013, effluent TN-C and MMP-2 levels were quantified in 182 PD patients with end-stage renal disease. Peritoneal function was estimated using the peritoneal equilibration test (PET). From the PET results, the D/P Cr ratio was correlated with effluent levels of TN-C (ρ = 0.57, p < 0.001) and MMP-2 (ρ = 0.73, p < 0.001). We suggest that TN-C in the effluents may be a diagnostic marker for peritoneal deterioration with EMT-like change in mesothelial cells in PD.

The use of mycophenolate mofetil in experimental encapsulating peritoneal sclerosis

INTRODUCTION

Encapsulated peritoneal sclerosis (EPS) is a rare complication of long-term peritoneal dialysis usually associated with the inadequacy and early termination of dialysis modality. Adequate treatment of peritoneal fibrosis has not been achieved by medical intervention so far. Mycophenolate mofetil (MMF), which inhibits inosine monophosphate dehydrogenase reversibly and highly selectively, is the most widely used drug for maintenance immunosupression in renal transplantation. Recent studies have shown that MMF has also antifibrotic effects. In this study, we evaluated the effects of MMF on EPS model in rats based on antifibrotic effects.

MATERIALS AND METHODS

Twenty-four Wistar albino rat have been randomly divided into four groups. Group I (control group) received isotonic saline intraperitoneally (i.p) 2 ml/day for (0-3rd weeks). Group II (chlorhexidine (CG) group) received CG 2 ml/day i.p. for (0-3rd weeks). Group III (chlorhexidine + MMF group) received CG (2 ml/day) i.p. for (0-3rd weeks) plus MMF 30 mg/kg/day peroral (4th-6th weeks). Group IV (resting group) received CG 2 ml/day) i.p. (0-3rd weeks) plus peritoneal resting without any treatment (4th-6th weeks) At the end of the sixth weeks, all of the rats were killed. All of the groups were analyzed in terms of peritoneal thickness, degree of inflammation, vasculopathy, neovascularization and fibrosis. Also, the parietal peritoneal tissue samples were evaluated for matrix metalloproteinase 2 (MMP-2) by using the immunohistochemical analysis.

RESULTS

When the CG group was compared with the MMF group, the medication resulted in a statistically significant reduction in peritoneal thickness, inflammation and fibrosis score (53.23 ± 16.24 vs. 17.22 ± 3.62, 1 ± 1.225 vs. 1 ± 0, 1.6 ± 0.548 vs. 0.2 ± 0.447, respectively, all p < 0.05). In the resting group, no beneficial effects on morphological abnormality of the peritoneum were observed as compared with MMF group. However, according to immunohistochemical analysis of the expression of MMP-2 on peritoneal samples, the highest expression of MMP-2 was observed in the MMF group.

CONCLUSION

MMF was effective for the treatment of encapsulating peritoneal fibrosis in our rat model. Most recently, MMF may be first choice for EPS due to antifibrotic effect.

Ultrafiltration failure in peritoneal dialysis: a pathophysiologic approach

BACKGROUND

Ultrafiltration failure is a significant cause of technique failure for peritoneal dialysis and subsequent transfer to hemodialysis.

SUMMARY

Ultrafiltration failure is defined as failure to achieve at least 400 ml of net ultrafiltration during a 4 h dwell using 4.25% dextrose. Four major causes of ultrafiltration failure have been described. A highly effective peritoneal surface area is characterized by transition to a very rapid transport state with D/P creatinine >0.81. Low osmotic conductance to glucose is characterized by attenuation of sodium sieving and decreased peritoneal free water clearance to <26% of total ultrafiltration in the first hour of a dwell. Low effective peritoneal surface area manifests with decreases in the transport of both solute and water. A high total peritoneal fluid loss rate is the most difficult to diagnose clinically; failure to achieve ultrafiltration with an 8-10 h icodextrin dwell may provide a clue to diagnosis.

KEY MESSAGES

Knowledge of the specific pathophysiology of the various causes of ultrafiltration failure will aid in the diagnosis thereof.

Encapsulating peritoneal sclerosis-a rare but devastating peritoneal disease

Encapsulating peritoneal sclerosis (EPS) is a devastating but, fortunately, rare complication of long-term peritoneal dialysis. The disease is associated with extensive thickening and fibrosis of the peritoneum resulting in the formation of a fibrous cocoon encapsulating the bowel leading to intestinal obstruction. The incidence of EPS ranges between 0.7 and 3.3% and increases with duration of peritoneal dialysis therapy. Dialysis fluid is hyperosmotic, hyperglycemic, and acidic causing chronic injury and inflammation in the peritoneum with loss of mesothelium and extensive tissue fibrosis. The pathogenesis of EPS, however, still remains uncertain, although a widely accepted hypothesis is the "two-hit theory," where, the first hit is chronic peritoneal membrane injury from long standing peritoneal dialysis followed by a second hit such as an episode of peritonitis, genetic predisposition and/or acute cessation of peritoneal dialysis, leading to EPS. Recently, EPS has been reported in patients shortly after transplantation suggesting that this procedure may also act as a possible second insult. The process of epithelial-mesenchymal transition of mesothelial cells is proposed to play a central role in the development of peritoneal sclerosis, a common characteristic of patients on dialysis, however, its importance in EPS is less clear. There is no established treatment for EPS although evidence from small case studies suggests that corticosteroids and tamoxifen may be beneficial. Nutritional support is essential and surgical intervention (peritonectomy and enterolysis) is recommended in later stages to relieve bowel obstruction.

Peritoneal effluent MMP-2 and PAI-1 in encapsulating peritoneal sclerosis

BACKGROUND

Recently, the use of effluent matrix metalloproteinase 2 (MMP-2) and plasminogen activator inhibitor 1 (PAI-1) as potential biomarkers of peritoneal fibrosis has been demonstrated during longitudinal follow-up of incident peritoneal dialysis (PD) patients. This study focuses on effluent MMP-2 and PAI-1 as early diagnostic markers in the preceding years of patients who develop encapsulating peritoneal sclerosis (EPS).

STUDY DESIGN

Diagnostic test study.

SETTINGS & PARTICIPANTS

PD patients who developed EPS were compared with controls using a 1:3 case-control design with a minimum PD duration of 57 months.

INDEX TESTS

Dialysate appearance rates of MMP-2 and PAI-1.

REFERENCE TEST

EPS cases identified by 2 experienced nephrologists and a radiologist based on predefined criteria.

RESULTS

11 patients developed EPS within our center. The time course of MMP-2 appearance rates, studied by means of a linear repeated-measures model 4 years prior to the diagnosis of EPS, showed no difference between long-term controls and patients with EPS. In contrast, higher PAI-1 appearance rates were found in patients with EPS compared with controls (P=0.01). At a lag time of 1 year prior to EPS diagnosis, time-specific receiver operating characteristic curve analyses indicated a discriminative ability for PAI-1 appearance rate of 0.77 (95% CI, 0.63-0.91). A discriminative capacity was absent for those of MMP-2.

LIMITATIONS

Low event rate of EPS prevented independent validation in this single-center study.

CONCLUSIONS

Elevated levels of PAI-1 appearance rates are present in patients who develop EPS, pointing to progressive peritoneal fibrosis and sclerosis. The PAI-1 appearance rate has fair discriminative capacity from 3 years prior to EPS diagnosis. Therefore, effluent PAI-1 may aid in monitoring peritoneal fibrosis and serve as a biomarker for EPS.

Higher Dialysate Matrix Metalloproteinase-2 Levels Are Associated with Peritoneal Membrane Dysfunction

♦

BACKGROUND

Peritoneal dialysis (PD) patients develop progressive and cumulative peritoneal injury with longer time spent on PD. The present study aimed to a) describe the trend of peritoneal injury biomarkers, matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-1 (TIMP-1), in incident PD patients, b) to explore the capacity of dialysate MMP-2 to predict peritoneal solute transport rate (PSTR) and peritonitis, and c) to evaluate the influence of neutral pH, low glucose degradation product (GDP) PD solution on these outcomes. ♦

METHODS

The study included 178 participants from the balANZ trial who had at least 1 stored dialysate sample. Changes in PSTR and peritonitis were primary outcome measures, and the utility of MMP-2 in predicting these outcomes was analyzed using multilevel linear regression and multilevel Poisson regression, respectively. ♦

RESULTS

Significant linear increases in dialysate MMP-2 and TIMP-1 concentrations were observed (p < 0.001), but neither was affected by the type of PD solutions received (MMP-2: p = 0.07; TIMP-1: p = 0.63). An increase in PSTR from baseline was associated with higher levels of MMP-2 (p = 0.02), and the use of standard solutions over longer PD duration (p = 0.001). The risk of peritonitis was independently predicted by higher dialysate MMP-2 levels (incidence rate ratio [IRR] per ng/mL 1.01, 95% confidence interval [CI] 1.005 - 1.02, p = 0.002) and use of standard solutions (Biocompatible solution: IRR 0.45, 95% CI 0.24 - 0.85, p = 0.01). ♦

CONCLUSION

Dialysate MMP-2 and TIMP-1 concentrations increased with longer PD duration. Higher MMP-2 levels were associated with faster PSTR and future peritonitis risk. Administration of biocompatible solutions exerted no significant effect on dialysate levels of MMP-2 or TIMP-1, but did counteract the increase in PSTR and the risk of peritonitis associated with the use of standard PD solutions. This is the first longitudinal study to examine the clinical utility of MMP-2 as a predictor of patient-level outcomes.

Dialysate cytokine levels do not predict encapsulating peritoneal sclerosis

BACKGROUND

Encapsulating peritoneal sclerosis (EPS) is a rare but devastating complication of long-term peritoneal dialysis (PD). There is no well-validated method for predicting which patients will develop the condition, although known risk factors include long duration of PD, high glucose exposure and lack of residual renal function. We have investigated whether dialysate cytokines (MCP-1 (monocyte chemotactic protein-1), CCL18 (pulmonary and activation-regulated cytokine, PARC), IL-6 (interleukin-6), CCL15 (leukotactin) and angiogenin) could be used to predict the onset of EPS more effectively than known clinical risk factors.

METHODS

Samples of dialysate and clinical data were prospectively collected from 151 patients at the West London Renal center between 2003 and 2010. Dialysate cytokine levels were measured using the enzyme-linked immunoabsorbant assay (ELISA) technique. Encapsulating peritoneal sclerosis subsequently developed in 17 patients during a follow-up period of 27 - 113 months. Cytokines found at higher levels in dialysate of pre-EPS patients were investigated as candidate predictors of EPS using logistic regression analysis.

RESULTS

Dialysate IL-6, MCP-1 and CCL15 were significantly higher in patients who subsequently developed EPS; however, a logistic regression model using dialysate cytokines to predict EPS was no better than a model using well-recognized clinical markers (length of time on PD and membrane transport status).

CONCLUSIONS

Although MCP-1, IL-6 and CCL15 were found at higher levels in the dialysate of patients who subsequently developed EPS, dialysate levels of these cytokines do not improve prediction of future EPS above a model using known clinical risk factors.

Can effluent matrix metalloproteinase 2 and plasminogen activator inhibitor 1 be used as biomarkers of peritoneal membrane alterations in peritoneal dialysis patients?

BACKGROUND

Peritoneal effluent contains clinically relevant substances derived from intraperitoneal production or transperitoneal transport, or both. The glycoproteinase matrix metalloproteinase 2 (MMP-2) cleaves denatured collagen and complements other collagenases in the degradation of fibrillar collagens. Elevated intraperitoneal levels of plasminogen activator inhibitor 1 (PAI-1) have been demonstrated to be present in patients with intra-abdominal adhesions. The aim of the present study was therefore to investigate the potential for effluent MMP-2 and PAI-1 to be used as markers of the development of peritoneal alterations. In addition, MMP-2 was analyzed in previously frozen effluent samples from a uremic rat model, in which data concerning the severity of peritoneal fibrosis were available.

METHODS

This prospective, single-center cohort study included 86 incident peritoneal dialysis (PD) patients. All patients were treated solely with biocompatible dialysis solutions and underwent a standard peritoneal permeability analysis (SPA). The presence of local MMP-2 and PAI-1 production and the relationships between those markers and peritoneal transport parameters were analyzed. Furthermore, effluent interleukin 6 was analyzed as a marker of local inflammation.

RESULTS

Median effluent levels of 21.4 ng/mL for MMP-2 and 0.9 ng/mL for PAI-1 were found. The median dialysate appearance rates were 218.8 ng/min for MMP-2 and 9.6 ng/min for PAI-1. Local peritoneal production averaged 90% of effluent MMP-2 concentration and 74% of effluent PAI-1 concentration. Furthermore, correlations between peritoneal transport parameters and MMP-2 and PAI-1 were observed. Longitudinal follow-up showed no change for MMP-2 (p = 0.37), but a tendency for PAI-1 to increase with the duration of PD (p < 0.001). In rats, a significant relationship was present between the extent of peritoneal fibrosis and the appearance rate of MMP-2 (r = 0.64, p = 0.03).

CONCLUSIONS

The foregoing data illustrate the potential of effluent MMP-2 and PAI-1 as biomarkers of peritoneal modifications, especially fibrosis; however, the components of peritoneal transport and local production should be clearly distinguished in every patient.

Persistent sterile peritoneal inflammation after catheter removal for refractory bacterial peritonitis predicts full-blown encapsulating peritoneal sclerosis

BACKGROUND

Encapsulating peritoneal sclerosis (EPS) is the most serious complication of peritoneal dialysis, having high morbidity and mortality. To improve outcomes, early diagnosis is needed to direct treatment during the early inflammatory phase. However, in the early inflammatory phase, clinical features are nonspecific, and no reliable diagnostic criteria have been established. Because bacterial peritonitis and termination of dialysis are two important risk factors triggering the progression of EPS, patients with refractory bacterial peritonitis necessitating dialysis catheter removal are at particularly high risk of developing EPS. Many of these patients might indeed experience non-resolving sterile peritonitis (probably the inflammatory phase of EPS) before progression to full-blown disease (that is, the presence of intestinal obstruction). We undertook a retrospective study to compare, in this particular situation, the clinical characteristics of patients with or without sterile peritoneal inflammation, assessing their clinical outcomes in terms of short-term mortality and the chance of developing full-blown EPS.

METHODS

Our retrospective review included 62 patients whose dialysis catheter was removed because of refractory peritonitis between January 2005 and December 2010.

RESULTS

Of the 62 patients identified, 39 (63%) had persistent sterile peritoneal inflammation ("high-risk" group, n = 39), and 23 (37%) had resolution of inflammation without significant intra-abdominal collection after catheter withdrawal ("control" group, n = 23). Compared with the control group, the high-risk group had a significantly longer PD duration (71.6 ± 43.3 months vs 42.3 ± 29.9 months, p = 0.003), a higher dialysate-to-plasma ratio (D/P) of creatinine (0.768 ± 0.141 vs 0.616 ± 0.091, p = 0.004), and a higher computed tomography score for EPS (7.69 ± 2.98 vs 1.00 ± 1.00, p < 0.001). During the 6-month study period, the high-risk group had a higher chance of developing full-blown EPS (31% vs 0%, p = 0.002) and a higher 6-month all-cause mortality (36% vs 4.3%, p = 0.004).

CONCLUSIONS

Persistent sterile peritoneal inflammation was common after dialysis catheter removal for refractory bacterial peritonitis, and the patients with such inflammation were at high risk of progression to full-blown EPS.

Peritoneal changes in patients on long-term peritoneal dialysis

Long-term peritoneal dialysis can lead to morphological and functional changes in the peritoneum. Although the range of morphological alterations is known for the peritoneal dialysis population as a whole, these changes will not occur in every patient in the same sequence and to the same extent. Longitudinal studies are therefore required to help identify which patients might develop the changes. Although longitudinal studies using peritoneal biopsies are not possible, analyses of peritoneal effluent biomarkers that represent morphological alterations could provide insight. Longitudinal studies on peritoneal transport have been performed, but follow-up has often been too short and an insufficient number of parameters have been investigated. This Review will firstly describe peritoneal morphology and structure and will then focus on peritoneal effluent biomarkers and their changes over time. Net ultrafiltration will also be discussed together with the transport of small solutes. Data on the peritoneal transport of serum proteins show that serum protein levels do not increase to the same extent as levels of small solutes with long-term peritoneal dialysis. Early alterations in peritoneal transport must be distinguished from alterations that only develop with long-term peritoneal dialysis. Early alterations are related to vasoactive mediators, whereas later alterations are related to neoangiogenesis and fibrosis. Modern peritoneal dialysis should focus on the early detection of long-term membrane alterations by biomarkers--such as cancer antigen 125, interleukin-6 and plasminogen activator inhibitor 1--and the improved assessment of peritoneal transport.

Current status and practical use of effluent biomarkers in peritoneal dialysis patients

Long-term peritoneal dialysis therapy can lead to alterations in the function and morphology of the peritoneal membrane. Assessment of the peritoneal dialysis membrane usually is done by investigating the transport of small solutes and fluid. Assessment of morphologic alterations and their development would require repetitive peritoneal biopsies that usually are not feasible. Peritoneal tissues are bathed in dialysis solutions during peritoneal dialysis and may secrete or shed substances that can be recovered in peritoneal effluent. These molecular effluent biomarkers may give insight into morphologic changes. In this review, established and emerging candidate biomarkers in peritoneal dialysis are discussed. Additionally, requirements, challenges, and clinical applications of effluent biomarkers in peritoneal dialysis are addressed.

Periostin: a matricellular protein involved in peritoneal injury during peritoneal dialysis

BACKGROUND

Periostin is a matricellular protein involved in tissue remodeling through the promotion of adhesion, cell survival, cellular dedifferentiation, and fibrogenesis. It can be induced by transforming growth factor beta and high glucose concentrations. We hypothesized that this protein might be expressed in the peritoneal cavity of patients on peritoneal dialysis (PD) and even more in patients with signs of encapsulating peritoneal sclerosis (EPS).

METHOD

In this retrospective study, we included peritoneal biopsies from patients on PD with EPS (n = 7) and without signs of EPS (n = 10), and we compared them with biopsies taken during hernia repair from patients not on PD (n = 11) and during various procedures from uremic patients not on PD (n = 6). Periostin was localized by immunohistochemistry, scored semiquantitatively, and quantified by morphometry. Periostin protein concentrations were measured by ELISA in dialysates from 15 patients. Periostin messenger RNA was quantified in vitro in peritoneal fibroblasts.

RESULTS

In control biopsies, periostin was present in the walls of larger arteries and focally in extracellular matrix in the submesothelial zone. Patients on PD demonstrated interstitial periostin in variable amounts depending on the severity of submesothelial fibrosis. In EPS, periostin expression was very prominent in the sclerosis layer. The area of periostin was significantly larger in EPS biopsies than in control biopsies, and the percentage of periostin-positive area correlated with the thickness of the submesothelial fibrosis zone. Periostin concentrations in dialysate increased significantly with time on PD in patients without signs of EPS; in patients with EPS, periostin concentrations in dialysate were low and demonstrated the smallest increase with time. In vitro, periostin was found to be strongly expressed by peritoneal fibroblasts.

CONCLUSION

Periostin is strongly expressed by fibroblasts and deposited in the peritoneal cavity of patients with EPS and with simple peritoneal fibrosis on PD. This protein might play a role in the progression of peritoneal injury, and low levels of periostin after prolonged time on PD might be a marker of EPS.

Matrix metalloproteinase-2 inhibition by temocapril and its important role in peritoneal transport

1. Matrix metalloproteinase (MMP)-2 plays an important role in tissue remodelling during peritoneal injury caused by peritoneal dialysis (PD), but MMP-2 inhibitors have not yet been used clinically. Recently, it was reported that captopril, an angiotensin-converting enzyme inhibitor (ACEI), can inhibit MMP-2. 2. To investigate the potential usefulness of ACEI during PD, the molecular interaction between the MMP-2 active site and the active form of temocapril (temocaprilat) was investigated using molecular modelling. Furthermore, the effects of temocapril on MMP-2 activity in peritoneal effluents and the peritoneal solute transport rate of PD patients were determined. 3. Temocaprilat bound to the MMP-2 active centre and recognized two hydrophobic substrate-binding sites in the MMP-2 molecular model. Matrix metalloproteinase-2 activity in peritoneal effluents was directly inhibited by temocaprilat (IC(50) 0.47 μmol/L). In one patient given temocapril, the peritoneal solute transport rate decreased gradually during PD. 4. Temocapril may prove to be an important candidate for development as a novel therapeutic agent for MMP-2 inhibition to prevent peritoneal injury caused by PD.

Pentraxin 3 as a new biomarker of peritoneal injury in peritoneal dialysis patients

It is well known that bioincompatible peritoneal dialysate plays a central role in the development of peritoneal fibrosis. Peritoneal inflammation continues even after the cessation of peritoneal dialysate stimulation. It is important to establish the definition of persistent inflammation in the peritoneal cavity at the cessation of peritoneal dialysis (PD). The objective of the present study was to determine whether pentraxin 3 (PTX3) in peritoneal effluent (PE) may be a new biomarker in PD patients. Serum, PE, and peritoneal specimens were obtained from 50 patients with end-stage kidney disease at Juntendo University Hospital. Samples of 19 patients were obtained at the initiation of PD and those of 31 patients at the cessation of PD. PTX3, high-sensitivity CRP, and MMP-2 and IL-6 were analyzed. An immunohistological examination using an anti-PTX3 antibody was performed. Expressions of PTX3 were observed in endothelial cells, fibroblasts, and mesothelial cells in the peritoneum. The PTX3 level in PE at the cessation of PD was significantly higher than that at the initiation of PD. Effluent PTX3 levels in patients with a history of peritonitis or a PD duration of more than 8 years were significantly higher than those in patients without peritonitis or patients with a PD duration of <8 years. The PTX3 level was significantly correlated with MMP-2 and IL-6 levels in PE, as well as the thickness of the submesothelial compact zone and the vasculopathy. It appears that PTX3 may be a new biomarker of peritoneal inflammation and progressive fibrosis.

Twist: a new player in the epithelial-mesenchymal transition of the peritoneal mesothelial cells

BACKGROUND

The peritoneal membrane is a vital structure for peritoneal dialysis (PD) patients. It has been increasingly recognized that the transition of the peritoneal lining mesothelial cells into a more fibroblastic phenotype is a key step in peritoneal membrane injury.

METHODS

Relevant literature was reviewed and summarized.

RESULTS

Epithelial-to-mesenchymal transition (EMT) is a basic cellular process that occurs in a variety of physiologic and pathologic processes. The hallmark of this process is a loss of epithelial markers, and E-cadherin is a prototypical epithelial transmembrane protein. E-cadherin expression is suppressed at many levels and the gene is regulated by a family of transcription factors. Twist is one of the lesser studied E-cadherin regulatory factors, which belongs to a larger family of basic helix-loop-helix DNA-binding proteins. In this issue of Nephrology Dialysis Transplantation, Cuixiang Li reports on in vitro experiments where the expression of Twist led to a decreased expression of E-cadherin and the evidence of EMT. In an in vivo model of dialysate exposure, Li demonstrates that Twist expression is increased in the injured peritoneal tissues.

CONCLUSIONS

These important observations are the first to link Twist to mesothelial cell EMT and peritoneal membrane injury. Like most novel observations, this paper leaves many questions unanswered. Twist is only one of several transcription factors involved in EMT and how these factors interact will require further investigations. Furthermore, the question of whether Twist interacts at multiple levels in the EMT process, or simply gives an initial push to the process, is left unanswered. Finally, to bring these early significant findings to the bedside as potential therapies for PD patients will require further innovation.

Effects of renin-angiotensin-aldosterone system blockade on chlorhexidine gluconate-induced sclerosing encapsulated peritonitis in rats

Sclerosing encapsulated peritonitis (SEP) is a rare complication of long term peritoneal dialysis. Renin-angiotensin-aldosterone system (RAAS) may play a role in the development of peritoneal fibrosis in CAPD patients. We aimed to evaluate the effect of aliskiren, valsartan, and aliskiren + valsartan therapy on SEP. The study included 30 Wistar albino rats which were divided into five groups: I (Control) SF solution i.p.; II (CG group) chlorhexidine gluconate i.p.; III aliskiren oral plus CG i.p.; IV valsartan oral plus CG i.p.; and V aliskiren oral, valsartan oral and CG i.p. On the twenty-first day, all of the rats were sacrificed. All of the groups were analyzed in terms of peritoneal thickness, degree of inflammation, vasculopathy, neovascularization and fibrosis. Also, the parietal peritoneal tissue samples were evaluated for matrix metalloproteinase 2 (MMP-2) using the ELISA method. Peritoneal thickness and fibrosis scores were lower in the valsartan group compared to the CG group (P < 0.05). Peritoneal fibrosis scores were lower in the aliskiren group compared to CG group (P < 0.05) but no difference was observed between the peritoneal thickness scores of the two groups (P > 0.05). Tissue MMP-2 levels were significantly higher in the CG group compared other groups (P < 0.05). There were no statistically significant differences between the aliskiren, valsartan and aliskiren + valsartan groups according to the tissue MMP-2 levels. Due to the antifibrotic properties of valsartan, it is thought to be a possible choice to prevent SEP development. We found no positive impact of aliskiren or aliskiren + valsartan combination compared to valsartan alone.

Effect of sirolimus on the regression of peritoneal sclerosis in an experimental rat model

PURPOSE

Immunosuppressive and anti-inflammatory agents have recently become increasingly popular in the treatment of encapsulating peritoneal sclerosis (EPS). The aim of our study was to investigate the effects of sirolimus on EPS in a rat model.

METHODS

We separated 32 non-uremic rats into four groups: 1 control group, 2 ml isotonic saline injected IP daily for 3 weeks; 2 chlorhexidine gluconate (CG) group, 2 ml 0,1 % CG and 15 % ethanol dissolved in saline injected IP daily for 3 weeks; 3 resting group, CG (weeks 0-3) plus peritoneal rest (weeks 3-6); 4 sirolimus group, CG (weeks 0-3), plus 0.2 ml (1 mg/ml) sirolimus (weeks 3-6). Pathological samples were examined by using hematoxylin eosin (HE) and Masson's trichrome stains. Peritoneal thickness, fibrosis, vascular changes, and inflammation were evaluated by light microscopy. Finally, tissue metalloproteinase (MMP)-2 levels were measured by enzyme-linked immunoassay.

RESULTS

In the CG group, there was a significant increase in peritoneal thickness, inflammatory activity, and fibrosis score compared to the control group (p < 0.05). We also observed a lower fibrosis score and less peritoneal thickening in the sirolimus group compared to the resting and CG groups (p < 0.05). There was no difference in histopathologic findings, except for the inflammatory activity in the sirolimus group, compared to the control group. Although the CG group had higher tissue MMP-2 levels than the control group, the tissue MMP-2 levels were not significantly different from the other groups.

CONCLUSIONS

Sirolimus has a beneficial effect on peritoneal fibrosis induced by CG. This suggests that sirolimus may have therapeutic value in the management of EPS.

Additive effectiveness of everolimus plus tamoxifen therapy in treatment of encapsulating peritoneal sclerosis

Peritoneal dialysis (PD) is one of the commonly used choices of continuous renal replacement therapies. Peritoneal membrane is damaged by using solutions with lower biocompatibility, peritonitis episodes, and vintage of PD therapy. Encapsulating peritoneal sclerosis (EPS) is a rare complication of PD and is presented by progressive fibrosis of the peritoneum. Fibrous tissue entrapment of the intestine, leading to complete intestinal obstruction, is referred to as EPS, the most severe form of sclerosing peritonitis. EPS is irreversible fibrosis of the peritoneal membrane usually associated with high rates of morbidity and mortality. Preventive strategies are the best choice of treatment. Also there is no proven effective therapy for EPS; there are only small-sized trials. Herein we present a case of EPS who improved with everolimus plus tamoxifen therapy.

Level of 8-OHdG in drained dialysate appears to be a marker of peritoneal damage in peritoneal dialysis

PURPOSE

Peritoneal dialysis (PD) is a successful renal replacement therapy; however, long-term PD leads to structural and functional peritoneal damage. Therefore, the monitoring and estimation of peritoneal function are important in PD patients. Oxidative stress has been implicated as one possible mechanism of peritoneal membrane damage. The aim of this study was to evaluate the association between an oxidative stress marker, 8-hydroxydeoxyguanosine (8-OHdG), and peritoneal damage in PD patients.

METHODS

The authors evaluated 8-OHdG in drained dialysate by enzyme immunoassay to investigate the association between 8-OHdG and solute transport rate estimated by peritoneal equilibration test and matrix metalloproteinase-2 (MMP-2) level in 45 samples from 28 PD patients.

RESULTS

The 8-OHdG level was significantly correlated with dialysate:plasma creatine ratio (r = 0.463, P < 0.05) and significantly inversely correlated with D/D0 glucose (where D is the glucose level of peritoneal effluents obtained 4 hours after the injection and D0 is the glucose level obtained immediately after the injection) (r = -0.474, P < 0.05). The 8-OHdG level was also significantly correlated with MMP-2 level (r = 0.551, P < 0.05), but it was not correlated with the age of subjects, the duration of PD, or blood pressure.

CONCLUSION

The level of 8-OHdG in drained dialysate may be a useful novel marker of peritoneal damage in PD.

Encapsulating peritoneal sclerosis: what have we learned?

Encapsulating peritoneal sclerosis (EPS) is a rare complication of peritoneal dialysis (PD), but carries significant morbidity and mortality. We review the clinical features and radiologic and histologic changes found at diagnosis of EPS. Although EPS is strongly associated with the duration of PD, the pathogenesis remains only partly understood. We discuss the mechanisms thought to underlie the abnormally thickened, sclerotic peritoneal membrane seen in long-term PD patients including epithelial to mesenchymal transition and the molecular mediators of fibrosis and angiogenesis. We review how exposure to high-glucose, nonphysiological dialysis fluids, peritonitis, and uremia may be responsible for these changes. Much remains to be learned about optimal management of EPS, both medical and surgical, because the literature lacks controlled studies. Future research challenges include defining the role of surgery, immunosuppression, and antifibrotic agents in the management of EPS. We also need to understand why some patients progress from asymptomatic peritoneal sclerosis to the extreme levels of fibrin deposition and bowel encapsulation seen in EPS. Screening PD patients for potential future EPS remains difficult, and we need strategies for monitoring patients on longer-term PD that enable us to better quantify the risk of EPS for the individual patient.

Encapsulating peritoneal sclerosis: the state of affairs

Encapsulating peritoneal sclerosis (EPS) is a severe complication of long-term peritoneal dialysis (PD) with a 50% mortality rate. EPS is characterized by progressive and excessive fibrotic thickening of the peritoneum, leading to encapsulation of the bowels and intestinal obstruction. At present, EPS cannot be detected with certainty during its early stages; however, a progressive loss of ultrafiltration capacity often precedes its development. Studies that attempted to elucidate the pathogenesis of EPS have shown that the duration of exposure to PD fluids is the most important risk factor for EPS, and that young age and possibly the effects of peritonitis are additional contributory factors. The pathophysiology of EPS is probably best described as a multiple-hit process with a central role for transforming growth factor β. A form of EPS that develops shortly after kidney transplantation has also been recognized as a distinct clinical entity, and may be a common form of EPS in countries with a high transplantation rate. Criteria have been developed to identify EPS by abdominal CT scan at the symptomatic stage, but further clinical research is needed to identify early EPS in asymptomatic patients, to clarify additional risk factors for EPS and to define optimal treatment strategies.

The Effects of Interferon-α2b on Intestinal Flora in Peritoneal Fibrosis

Peritonitis is an important cause of the mortality and morbidity of peritoneal dialysis patients. The present study aims to investigate the effects of ýnterferon (IFN)-α2b on intestinal flora in peritoneal fibrosis. Twenty-four Wistar albino rats were divided into three groups. The control group received 0.9% saline (3 ml/d) intraperitoneally; the Chlorhexidine gluconate (CH) group received 3 ml daily injections of 0.1% CH intraperitoneally; the CH+IFN group received 3 ml daily injections of 0.1% CH intraperitoneally and pegylated IFN-α2b 1.5 μg/kg per week subcutaneously on days 0, 7, 14. On the twenty-first day rats were sacrificed and visseral peritoneum samples were obtained from the liver. Blood samples were obtained from the abdominal aorta and intestinal flora samples were obtained from distal small intestine and transverse colon. Histopathologic control of CH, CH+IFN groups peritoneal thickness were 6.04±2.32, 135.4±22.24, and 42.56±11.6 um, respectively. The decrease in thickness of parietal peritoneum in the CH+IFN group was statistically significant when compared to the CH group. Escherechia coli (E. Coli) had grown in cultures of the small intestine and colon samples of all the rats in the control group, whereas Proteus species (spp) had grown in one and Enterobacter spp. in seven cultures of the CH group. E. Coli had grown in four cultures, Proteus spp in three culture and Enterobacter spp. in one culture obtained from small intestine and transverse colon of the control group. The intestinal flora changed as the peritoneal thickness increased. The intestinal flora in the CH group completely changed compared with the control group (p<0.001). There was no correlation between visceral peritoneal thickness and intestinal flora change in the IFN group (p>0.05). IFN-α2b recovers the intestinal flora and the intestinal motility, thus reducing the experimental peritoneal fibrosis.

2009 Japanese Society for Dialysis Therapy guidelines for peritoneal dialysis

The guidelines for peritoneal dialysis (PD) of the Japanese Society for Dialysis Treatment were prepared at 2009. Upon presenting a concrete frame of PD practiced in Japan, it aims to promote PD as a standardized therapy in Japan. Notably, the guidelines recommended combination therapy of PD and hemodialysis as a part of integrated renal replacement therapy for end-stage renal disease, as well as timely PD withdrawal by peritoneal degeneration in order to prevent progression of encapsulating peritoneal sclerosis.

Update on potential medical treatments for encapsulating peritoneal sclerosis; human and experimental data

Encapsulating peritoneal sclerosis (EPS) is an infrequent but serious complication of peritoneal dialysis (PD). The pathogenesis is unknown but speculation is ongoing. The current management of EPS focuses on prevention and treatment of the inflammatory and fibrotic changes at the level of the peritoneal membrane with immunosuppressive and antifibrotic agents, respectively. This article reviews the currently available human and animal data on potential agents to prevent and/or treat EPS. We propose a strategy for early diagnose EPS in an attempt to avoid the development of the full-blown and potentially life-threatening clinical syndrome of EPS. Future research should focus on studying potential prophylactic and therapeutic agents in humans in large, multicenter, randomized trials but also on early detection of EPS in the inflammatory phase by means of biomarkers and the establishment of a composite EPS score.

Matrix metalloproteinase levels in the drained dialysate reflect the peritoneal solute transport rate: a multicentre study in Japan

BACKGROUND

Long-term peritoneal dialysis (PD) leads to peritoneal injury with high solute transport of the peritoneal membrane. At worst, peritoneal injury leads to encapsulating peritoneal sclerosis with an extremely high mortality rate. To perform PD safely and adequately, it is necessary to monitor peritoneal injury. The aim of this study was to investigate the potential of matrix metalloproteinases (MMPs) as new indicators of peritoneal injury.

METHODS

The subjects included 215 PD patients with end-stage renal disease at 20 centres in Japan. MMPs or tissue inhibitors of MMP (TIMPs) in the drained dialysate were quantified with enzyme-linked immunosorbent assay. The peritoneal solute transport rate was assessed to estimate peritoneal injury and PD efficiency by the peritoneal equilibration test (PET).

RESULTS

MMP-2, MMP-3 and TIMP-1 levels in the drained dialysate obtained by the PET were correlated with the D/P Cr ratios (ρ = 0.69, ρ = 0.52, ρ = 0.55, respectively) and the D/D0 glucose ratios (ρ = -0.60, ρ = -0.47, ρ = -0.48, respectively). The measured D/S ratios of MMP-2 and TIMP-1 were significantly higher than the expected D/S ratios when MMP-2 and TIMP-1 would have been transported from only the circulation. The measured D/S ratios of MMP-3 nearly corresponded to the expected ratios. MMP-1 and TIMP-2 in the drainage were undetected in most patients.

CONCLUSIONS

From these results, most MMP-2 in the drained dialysate may be produced from the peritoneum, and MMP-2 is expected to be a useful marker of peritoneal injury or change in peritoneal solute transport.

Screening for encapsulating peritoneal sclerosis in patients on peritoneal dialysis: role of CT scanning

BACKGROUND

We previously validated a scoring system for abdominal/pelvic CT scans in patients with symptomatic encapsulating peritoneal sclerosis (EPS). CT scans of patients with symptomatic EPS were significantly different from control peritoneal dialysis (PD) or haemodialysis patient scans; scans performed before EPS was clinically evident were near normal in 9 of 13 patients. We have now investigated CT scanning as a screening modality in a larger group of patients on long-term PD.

METHODS

Pre-diagnostic CT scans performed in 20 patients for routine screening or other indications at least 3 months before EPS developed, and later diagnostic scans when EPS was clinically evident, were scored by three radiologists. The control group included CT scans of 20 PD patients who had not developed EPS (median follow-up 2.25 years). Analysis was by non-parametric tests. CT scores ranged from 0 to 22; > 2.5 was considered abnormal.

RESULTS

Clinical EPS only developed after transplantation or transfer to HD. Diagnostic scans scored significantly higher than pre-diagnostic or control scans (median scores 9, 2 and 1; P < 0.001), confirming previous work. The pre-EPS diagnosis of 12 asymptomatic patients had a median CT score = 1.75, similar to the control group. Eight patients had had a limited episode of abdominal symptoms (seven required hospitalization), but did not have the clinical picture of EPS; their median CT score was 4.5 (P = 0.0016 cf control group). The time from pre-diagnostic scan to clinical EPS (median 0.82 years) and duration of PD at time of pre-diagnostic scan (median 7.1 years) did not differ significantly between the symptomatic and asymptomatic groups.

CONCLUSIONS

CT screening of asymptomatic PD patients is not indicated; EPS may occur within a year or less of a normal CT scan. Abdominal symptoms in long-term PD patients can be associated with CT scan abnormalities; these patients are at increased risk of EPS after stopping PD.

Homocysteine and Hypertension in Diabetes: Does PPARgamma Have a Regulatory Role?

Dysfunction of macro- and microvessels is a major cause of morbidity and mortality in patients with cardio-renovascular diseases such as atherosclerosis, hypertension, and diabetes. Renal failure and impairment of renal function due to vasoconstriction of the glomerular arteriole in diabetic nephropathy leads to renal volume retention and increase in plasma homocysteine level. Homocysteine, which is a nonprotein amino acid, at elevated levels is an independent cardio-renovascular risk factor. Homocysteine induces oxidative injury of vascular endothelial cells, involved in matrix remodeling through modulation of the matrix metalloproteinase (MMP)/tissue inhibitor of metalloproteinase (TIMP) axis, and increased formation and accumulation of extracellular matrix protein, such as collagen. In heart this leads to increased endothelial-myocyte uncoupling resulting in diastolic dysfunction and hypertension. In the kidney, increased matrix accumulation in the glomerulus causes glomerulosclerosis resulting in hypofiltration, increased renal volume retention, and hypertension. PPARγ agonist reduces tissue homocysteine levels and is reported to ameliorate homocysteine-induced deleterious vascular effects in diabetes. This review, in light of current information, focuses on the beneficial effects of PPARγ agonist in homocysteine-associated hypertension and vascular remodeling in diabetes.

The Effects of Interferon α2b on Chemically-Induced Peritoneal Fibrosis and on Peritoneal Tissue MMP-2 and TIMP-2 Levels in Rats

This study investigated the effect of interferon α2b on chlorhexidine gluconate (CH)-induced peritoneal fibrosis (PF) in rats and assessed peritoneal tissue levels of metalloproteinase (MMP)-2 and tissue inhibitors of metalloproteinases (TIMP)-2. Wistar albino rats ( n = 8 per group) were treated as follows: control group, 3 ml/day of 0.9% saline intra-peritoneally for 28 days; CH group, 0.1% CH (200 g [3 ml]/day) in 15% ethanol and 0.9% saline intra-peritoneally for 28 days; CH + interferon (IFN) group, CH (as above) plus pegylated IFN-α2b 1.5 μg/kg per week subcutaneously on days 0, 7, 14, 21 and 28; IFN group, pegylated IFN-α2b (as above).

Parietal peritoneum samples were obtained from the left anterior abdominal wall after 35 days. Parietal thickness, degree of vascular proliferation and inflammation, and MMP-2 and TIMP-2 levels were determined. The mean peritoneal thicknesses of the control, CH, CH + IFN and IFN groups were 7.02 ± 3.89, 156.86 ± 29.13, 59.88 ± 22.1, 9.27 ± 2.03 μm, respectively. Pegylated IFN-α2b decreased CH-induced expression of MMP-2 in the parietal peritoneum, but had no effect on TIMP-2 levels. Further studies are needed to determine the optimal dosage and duration for pegylated IFN-α2b treatment.

The effects of low-dose erythropoiesis-stimulating agents on peritoneal fibrosis induced by chemical peritonitis and on peritoneal tissue MMP-2 and TIMP-2 Levels in rats

AIM

The objective of the present study was to investigate the effect of low-dose erytropoesis-stimulating agents (ESA) on the development of peritoneal fibrosis in chlorhexidine gluconate-induced peritoneal sclerosing rats and to assess the peritoneal tissue levels of MMP-2 and TIMP-2, which may be regarded as factors in the development of peritoneal fibrosis.

SUBJECTS AND METHODS

Twenty-four Wistar albino rats were divided into three groups. The control group received 0.9% saline (3 ml/d) intraperitoneally, the CH group received 3 ml daily injections of 0.1% chlorhexidine gluconate (CH) intraperitoneally, and the CH+ESA group received 3 ml daily injections of 0.1% CH intraperitoneally and epoetin beta (3 x 20 IU/kg/week) subcutaneously. On the twenth-first day, rats were sacrificed, and parietal peritoneum samples were obtained from the left anterior abdominal wall. Pathological samples were examined using Hematoxyline & Eosin (HE) stains. The thickness, vascular proliferation, and inflammation were determined by light microscopy. MMP-2 and TIMP-2 were studied immunohistochemically by monoclonal antibody staining.

RESULTS

Inflammation, vascular proliferation, and fibrotic area percentages were not statistically significant between groups. Histopathologically control, CH, CH+ESA groups peritoneal thickness were 8.02 +/- 2.89, 146.74 +/- 26.1, and 48.12 +/- 16.8 micrometers, respectively. The decrease in thickness of parietal peritoneum in CH+ESA group was statistically significant when compared to CH. Immunohistochemically, interferon was shown to decrease MMP-2 expression on parietal peritoneum than group CH, but has no effect on TIMP-2.

DISCUSSION

Low-dose ESA histopatologically reduces peritoneal fibrosis induced by chlorhexidine gluconate. However, from dosage and duration points of view, we need extended clinical and experimental studies.