Long-term peritoneal membrane changes

Increased expression of epimorphin in a peritoneal fibrosis mouse model

BACKGROUND

Long-term peritoneal dialysis results in functional and histopathological alterations of the peritoneal membrane, leading to peritoneal fibrosis (PF). The mechanism of PF has not been fully elucidated, and at present there is no effective therapy for PF. Epimorphin is a mesenchymal protein that not only regulates morphogenesis in organ development but is implicated in tissue repair. However, the role of epimorphin in PF has not yet been clarified.

METHODS

PF was induced in C57/Bl6 mice by intraperitoneal injection of chlorhexidine gluconate (CG-injected mice) three times a week for 3 weeks. The parietal peritoneum was subsequently dissected and assessed by Masson's trichrome staining, and epimorphin expression was analysed by immunohistochemistry and real-time reverse transcription polymerase chain reaction (RT-PCR). Furthermore, epimorphin-positive regions were analysed by multiple immunofluorescence staining using fibrosis-associated markers. In addition, normal rat fibroblast cells (NRK-49F) were treated with transforming growth factor-β (TGF-β) in the presence or absence of epimorphin. The expression of fibrosis-associated markers was assessed by real-time RT-PCR.

RESULTS

In CG-injected mice, Masson's trichrome staining showed marked thickening of the submesothelial compact zone. Weak epimorphin expression was observed in the narrow submesothelial compact zone beneath the mesothelial cells in control mice; however, epimorphin expression was stronger in the submesothelial compact zone in CG-injected mice. Epimorphin expression was observed mainly in α-smooth muscle actin (α-SMA)-positive myofibroblasts. Epimorphin suppressed the TGF-β-induced upregulation of α-SMA and platelet-derived growth factor receptor-β in cultured cells.

CONCLUSIONS

Our results suggest that epimorphin may be a therapeutic target for fibrotic diseases of the peritoneum.

An inhibitor of Krüppel-like factor 5 suppresses peritoneal fibrosis in mice

BACK GROUND

Krüppel-like transcription factor 5 (KLF5) is a transcription factor regulating cell proliferation, angiogenesis and differentiation. It has been recently reported that Am80, a synthetic retinoic acid receptor α-specific agonist, inhibits the expression of KLF5. In the present study, we have examined the expression of KLF5 in fibrotic peritoneum induced by chlorhexidine gluconate (CG) in mouse and evaluated that Am80, as an inhibitor of KLF5, can reduce peritoneal fibrosis.

METHODS

Peritoneal fibrosis was induced by intraperitoneal injection of CG into peritoneal cavity of ICR mice. Am80 was administered orally for every day from the start of CG injection. Control mice received only a vehicle (0.5% carboxymethylcellulose solution). After 3 weeks of treatment, peritoneal equilibration test (PET) was performed and peritoneal tissues were examined by immunohistochemistry.

RESULTS

The expression of KLF5 was less found in the peritoneal tissue of control mice, while KLF5 was expressed in the thickened submesothelial area of CG-injected mice receiving the vehicle. Am80 treatment reduced KLF5 expression and remarkably attenuated peritoneal thickening, accompanied with the reduction of type III collagen expression. The numbers of transforming growth factor β-positive cells, α-smooth muscle actin-positive cells and infiltrating macrophages were significantly decreased in Am80-treated group. PET revealed the increased peritoneal permeability in CG mice, whereas Am80 administration significantly improved the peritoneal high permeability state.

CONCLUSIONS

These results indicate the involvement of KLF5 in the progression of experimental peritoneal fibrosis and suggest that Am80 may be potentially useful for the prevention of peritoneal fibrosis through inhibition of KLF5 expression.

Comparison of Longitudinal Membrane Function in Peritoneal Dialysis Patients According to Dialysis Fluid Biocompatibility

Introduction

Preservation of peritoneal function is essential in long-term peritoneal dialysis. Biocompatible dialysis solutions might prevent or postpone the membrane alteration resulting in ultrafiltration failure and consecutive morbidity and mortality.

Methods

We conducted an observational cohort study in which we made a longitudinal comparison between the course of peritoneal solute and fluid transport during treatment with conventional and biocompatible solutions. Therefore, prospectively collected peritoneal transport data from the yearly standard peritoneal permeability analysis were analyzed in 251 incident patients treated between 1994 and censoring in 2016. Fluid transport included small pore and free water transport. Solute transport was assessed by creatinine mass transfer area coefficient and glucose absorption. Linear mixed models including change point analyses were performed. Interaction with peritonitis was examined.

Results

One hundred thirty-five patients received conventional and 116 biocompatible solutions. Sixty-seven percent (conventional) and 64% (biocompatible) of these underwent minimally three transport measurements. Initially, biocompatible fluids showed higher small solute transport and lower ultrafiltration than conventional fluids up to 3 years. Thereafter, conventional fluids showed an increase in small solute transport (+2.7 ml/min per year; 95% confidence interval [CI]: 0.9 to 4.5) and a decrease of free water transport (−28.0 ml/min per year; 95% CI: −60.4 to 4.4). These were minor or absent in biocompatible treatment. Peritonitis induced a decrease of transcapillary ultrafiltration after 2 years on dialysis with conventional solutions (−291 ml/min per year; 95% CI: −550 to −32) while this was absent in biocompatible treatment.

Conclusion

Despite a higher initial solute transport with biocompatible solutions, these have less influence on functional long-term peritoneal alterations than conventional solutions.

Generation of TNFα and Interleukin-6 by Peritoneal Macrophages after Overnight Dwells with Bicarbonate- or Lactate-Buffered Dialysis Fluid

Objective

In order to evaluate the biocompatibility profile of a newly designed peritoneal dialysis fluid (PDF), we evaluated peritoneal leukocyte (PMΦ) cytokine release following overnight in vivo dwells using standard, lactate-buffered, single-chamber bag PDF (Lac-PDF) and purely bicarbonate-buffered, double-chamber bag PDF containing 34 (Bic-PDF) or 39 (Bic Hi-PDF) mmol/L bicarbonate.

Design

A randomized, open, crossover clinical trial with single weekly test dwells was performed in stable, long-term continuous ambulatory PD patients ( n = 8). During 8-hour overnight dwells, PMΦ were exposed to different PDF containing 1.5% glucose. After drainage, peritoneal cells were isolated and incubated with RPMI 1640 medium for 2 or 3 hours, with and without stimulation by lipopolysaccharide (LPS). Ex vivo release of tumor necrosis factor (TNF)-α and interleukin (IL)-6 was measured by specific ELISA technique.

Results

After pre-exposure to Lac-PDF, PMΦ generated 242 ± 279 pg TNFα/106 cells and 157 ± 105 pg IL-6/106 cells. When pre-exposed to Bic-PDF and Bic Hi-PDF, TNFα and IL-6 production of PMΦ was not significantly different from Lac-PDF. After LPS stimulation (100 ng/mL), PMΦ secretion of TNFα and IL-6 pre-exposed to three PDF revealed no significant differences between groups: TNFα was 2864 ± 1216, 2910 ± 1202, and 3291 ± 558 pg/106 cells after overnight dwells with Lac-PDF, Bic-PDF, and Bic Hi-PDF, respectively. Comparably, LPS-stimulated (100 pg/mL) PMΦ showed IL-6 secretion of 891 ± 335, 1380 ± 1149, and 1442 ± 966 pg/106 cells for Lac-PDF, Bic-PDF, and Bic Hi-PDF.

Conclusion

After long-term overnight dwells, initial pH, the different buffers, and varying glucose degradation product levels of PDF do not strongly affect PMΦ function with respect to cytokine release. The lack of significant differences between fluids may result from the complete dialysate equilibration achieved during the overnight intraperitoneal dwell.

Biocompatibility of Peritoneal Dialysis Fluids: Long-term Exposure of Nonuremic Rats

Objectives

Long-term peritoneal dialysis (PD) leads to structural and functional changes in the peritoneum. The aim of the present study was to investigate the long-term effects of PD fluid components, glucose and glucose degradation products (GDP), and lactate-buffered solution on morphology and transport characteristics in a nonuremic rat model.

Methods

Rats were subjected to two daily intraperitoneal injections (20 mL/day) during 12 weeks of one of the following: commercial PD fluid (Gambrosol, 4%; Gambro AB, Lund, Sweden), commercial PD fluid with low GDP levels (Gambrosol trio, 4%; Gambro AB), sterile-filtered PD fluid (4%) without GDP, or a glucose-free lactate-buffered PD fluid. Punctured and untreated controls were used. Following exposure, the rats underwent a single 4-hour PD dwell (30 mL, 4% glucose) to determine peritoneal function. Additionally, submesothelial tissue thickness, percentage of high mesothelial cells (perpendicular diameter > 2 μm), vascular density, vascular endothelial growth factor (VEGF), and transforming growth factor (TGF) β1mRNA expression were determined. Submesothelial collagen concentration was estimated by van Gieson staining.

Results

Submesothelial tissue thickness and vascular density, mediated by VEGF and TGFβ production, in the diaphragmatic peritoneum increased significantly in rats exposed to any PD fluid. Gambrosol induced a marked increased fibrosis of the hepatic peritoneum. A significant increase in high mesothelial cells was observed in the Gambrosol group only. Net ultrafiltration was reduced in the Gambrosol and in the glucose-free groups compared to untreated controls. Small solute transport was unchanged, but all groups exposed to fluids showed significantly increased lymph flow.

Conclusions

Our results show that long-term exposure to different components of PD fluids leads to mesothelial cell damage, submesothelial fibrosis, and neoangiogenesis. Mesothelial cell damage could be connected to the presence of GDP; the other changes were similar for all fluids. Peritoneal transport characteristics did not change in any consistent way and the neoangiogenesis observed was not paralleled by increased solute transport.

Glucose Degradation Products in Peritoneal Dialysis Fluids May Have Both Local and Systemic Effects: A Study of Residual Fluid and Mesothelial Cells

Objective

When peritoneal dialysis (PD) fluids are heat sterilized, glucose is degraded to carbonyl compounds. These compounds are known to interfere with many cellular functions and to promote the formation of advanced glycation end-products. However, little is known about what actually happens with glucose degradation products (GDPs) after infusion into the peritoneal cavity. The aim of the present study was to investigate possible targets for GDPs in the peritoneal cavity.

Design

In vitro reactions between residual fluid and GDPs were studied by incubating unused PD fluid with overnight dialysate. Confluent monolayer cultures of human mesothelial cells were used as a model to study the reactions of GDPs with the cells lining the peritoneal cavity.

Methods

Samples were analyzed, using high pressure liquid chromatography, for the presence of formaldehyde, acetaldehyde, 5-hydroxymethyl-2-furaldehyde (5-HMF), methylglyoxal, and 3-deoxyglucosone (3-DG). Cytotoxicity was determined as inhibition of proliferation of cultured fibroblasts.

Results

None of the analyzed GDPs reacted with overnight dialysate. Formaldehyde and methylglyoxal, in contrast to 3-DG and 5-HMF, reacted with the cultured mesothelial cells.

Conclusions

Low molecular weight carbonyls such as formaldehyde and methylglyoxal most probably react with the mesothelial cells lining the peritoneal cavity, and could be responsible for the disappearance of these cells during long-term treatment. 3-Deoxyglucosone showed remarkably low reactivity and was most probably transported within the patient.

Effects of SMAD7 Overexpression on Peritoneal Inflammation in a Rat Peritoneal Dialysis Model

Objective

Transforming growth factor-beta (TGF-β) has been shown to play a role in peritoneal complications due to long-term peritoneal dialysis (PD). In this study, we examined the effects of the TGF-β signaling pathway on peritoneal inflammation associated with PD in rats by over-expressing Smad7, an inhibitor of TGF-β/Smad signaling.

Methods

Peritoneal inflammation was induced in male Sprague-Dawley rats by intraperitoneal injections of 4.25% glucose dialysate (100 mg/kg body weight) daily for 4 weeks, with the addition of lipopolysaccharides (0.6 mg/kg body weight) on days 8, 10, 12, 22, 24, and 26. Peritoneal Smad7 gene transfer was achieved using an ultrasound microbubble mediated, doxycycline regulated, Smad7-expressing plasmid on day 0 and day 14 after initiation of PD. An empty vector was used as control. All rats were sacrificed after 4 weeks of PD. Peritoneal inflammatory response, including infiltration of total leukocytes (OX-1 positive) and macrophages (ED-1 positive) and expression of interleukin (IL)-1β) and tumor necrosis factor-alpha (TNF-α), was examined by immunofluorescence and RT-PCR.

Results

After PD, peritoneal inflammation developed in control animals, as demonstrated by an increase in the number of OX-1-positive and ED-1-positive cells and upregulation of IL-1β and TNF-α mRNA and protein expression. In contrast, in animals treated with Smad7 gene transfer, IL-1β and TNF-α expression and OX-1-positive and ED-1-positive cell infiltration were significantly inhibited. Furthermore, prevention of peritoneal inflammation by overexpression of Smad7 was associated with inhibition of phosphorylation of Smad2/3, a downstream of the TGF-β signaling pathway, as well as TGF-β1 expression.

Conclusion

Overexpression of Smad7 suppresses peritoneal inflammation induced by high glucose and lipopolysaccharides. The ability of Smad7 gene transfer to inhibit peritoneal inflammation indicates that targeting TGF-β/Smad signaling may represent a new therapeutic strategy for the treatment of peritoneal complications associated with PD.

Isolation of bacterial DNA followed by sequencing and differing cytokine response in peritoneal dialysis effluent help in identifying bacteria in culture negative peritonitis

AIM

The treatment of peritoneal dialysis related culture negative peritonitis is empirical which increases the cost of therapy and moreover antibiotic resistance. We aimed the study to isolate bacterial DNA from PD effluent and indentify bacteria causing peritonitis in culture negative situations. We have also studied the cytokine response with different bacteria causing peritonitis.

METHODS

We have isolated bacterial DNA from PD effluent of culture negative and culture positive peritonitis patients. Bacterial DNA was subjected to polymerase chain reaction using universal bacteria specific primers and subsequently to Gram type specific primers for the differentiation of the etiologic agents into Gram-positive and Gram-negative. The amplified products were sequenced and subjected to blast search to identify agent at genus/ species level.

RESULTS

Of the 30 molecular method positive samples, 16 (53.33%) samples were positive for Gram-negative bacteria and 4 (13.33%) for Gram-positive, while the remaining10 (33.33%) were positive for both Gram-positive and Gram-negative bacteria. We have found organisms that usually do not grow on normal culture methods. TNF-α was significantly associated with Gram-positive peritonitis and regulatory cytokine IL-10 with Gram-negative peritonitis.

CONCLUSIONS

The molecular techniques are helpful in detecting and identifying organisms from culture negative PD effluent.

Vitamin D can ameliorate chlorhexidine gluconate-induced peritoneal fibrosis and functional deterioration through the inhibition of epithelial-to-mesenchymal transition of mesothelial cells

BACKGROUND

Peritoneal dialysis (PD) can induce fibrosis and functional alterations in PD patients' peritoneal membranes, due to long-term unphysiological dialysate exposure, partially occurring via triggering of epithelial-to-mesenchymal transition (EMT) in peritoneal mesothelial cells (MCs). Vitamin D can ameliorate these negative effects; however, the mechanism remains unexplored. Therefore, we investigated its possible links to MCs EMT inhibition.

METHODS

Peritoneal fibrosis was established in Sprague-Dawley rats by chlorhexidine gluconate (CG) intraperitoneal injection for 21 days, with and without 1α,25(OH)2D3 treatment. Morphological and functional evaluation and western blot analysis of EMT marker were performed upon peritoneum tissue. In vitro study was also performed in a primary human peritoneal MC culture system; MCs were incubated with transforming growth factor-β1 (TGF-β1) in the absence or presence of 1α,25(OH)2D3. EMT marker expression, migration activities, and cytoskeleton redistribution of MCs were determined.

RESULTS

1α,25(OH)2D3 ameliorated CG-induced morphological and functional deterioration in animal model, along with CG-induced upregulation of α-SMA and downregulation of E-cadherin expression. Meanwhile, 1α,25(OH)2D3 also ameliorated TGF-β1-induced decrease in E-cadherin expression, increase in Snai1 and α-SMA expression, intracellular F-actin redistribution, and migration activity in vitro.

CONCLUSION

1α,25(OH)2D3 can ameliorate CG-induced peritoneal fibrosis and attenuate functional deterioration through inhibiting MC EMT.

Treatment for peritoneal dialysis-associated peritonitis

BACKGROUND

Peritonitis is a common complication of peritoneal dialysis (PD) that is associated with significant morbidity including death, hospitalisation, and need to change from PD to haemodialysis. Treatment is aimed to reduce morbidity and recurrence. This is an update of a review first published in 2008.

OBJECTIVES

To evaluate the benefits and harms of treatments for PD-associated peritonitis.

SEARCH METHODS

For this review update we searched the Cochrane Renal Group's Specialised Register to March 2014 through contact with the Trials Search Co-ordinator using search terms relevant to this review. Studies contained in the Specialised Register are identified through search strategies specifically designed for CENTRAL, MEDLINE and EMBASE, and handsearching conference proceedings.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs assessing the treatment of peritonitis in PD patients (adults and children). We included any study that evaluated: administration of an antibiotic by different routes (e.g. oral, intraperitoneal (IP), intravenous (IV)); dose of an antibiotic agent; different schedules of administration of antimicrobial agents; comparisons of different regimens of antimicrobial agents; any other intervention including fibrinolytic agents, peritoneal lavage and early catheter removal.

DATA COLLECTION AND ANALYSIS

Multiple authors independently extracted data on study risk of bias and outcomes. Statistical analyses were performed using the random effects model. We expressed summarised treatment estimates as a risk ratio (RR) with 95% confidence intervals (CI) for dichotomous outcomes and mean difference (MD) with 95% CI for continuous outcomes.

MAIN RESULTS

We identified 42 eligible studies in 2433 participants: antimicrobial agents (36 studies); urokinase (4 studies), peritoneal lavage (1 study), and IP immunoglobulin (1 study). We did not identify any optimal antibiotic agent or combination of agents. IP glycopeptides (vancomycin or teicoplanin) had uncertain effects on primary treatment response, relapse rates, and need for catheter removal compared to first generation cephalosporins, although glycopeptide regimens were more likely to achieve a complete cure (3 studies, 370 episodes: RR 1.66, 95% CI 1.01 to 2.72). For relapsing or persistent peritonitis, simultaneous catheter removal and replacement was better than urokinase at reducing treatment failure rates (RR 2.35, 95% CI 1.13 to 4.91) although evidence was limited to a single small study. Continuous and intermittent IP antibiotic dosing schedules had similar treatment failure and relapse rates. IP antibiotics were superior to IV antibiotics in reducing treatment failure in one small study (RR 3.52, 95% CI 1.26 to 9.81). Longer duration treatment (21 days of IV vancomycin and IP gentamicin) had uncertain effects on risk of treatment relapse compared with 10 days treatment (1 study, 49 patients: RR 1.56, 95% CI 0.60 to 3.95) although may have increased ototoxicity.In general, review conclusions were based on a small number of studies with few events in which risk of bias was generally high; interventions were heterogeneous, and outcome definitions were often inconsistent. There were no RCTs evaluating optimal timing of catheter removal and data for automated PD were absent.

AUTHORS' CONCLUSIONS

Many of the studies evaluating treatment of PD-related peritonitis are small, out-dated, of poor quality, and had inconsistent definitions and dosing regimens. IP administration of antibiotics was superior to IV administration for treating PD-associated peritonitis and glycopeptides appear optimal for complete cure of peritonitis, although evidence for this finding was assessed as low quality. PD catheter removal may be the best treatment for relapsing or persistent peritonitis.Evidence was insufficient to identify the optimal agent, route or duration of antibiotics to treat peritonitis. No specific antibiotic appears to have superior efficacy for preventing treatment failure or relapse of peritonitis, but evidence is limited to few trials. The role of routine peritoneal lavage or urokinase is uncertain.

Predictors of peritonitis and the impact of peritonitis on clinical outcomes of continuous ambulatory peritoneal dialysis patients in Taiwan--10 years' experience in a single center

OBJECTIVE

Peritoneal dialysis (PD) has become more prevalent as a treatment modality for end-stage renal disease, and peritonitis remains one of its most devastating complications. The aim of the present investigation was to examine the frequency and predictors of peritonitis and the impact of peritonitis on clinical outcomes. ♢

METHODS

Our retrospective observational cohort study enrolled 391 patients who had been treated with continuous ambulatory PD (CAPD) for at least 90 days. Relevant demographic, biochemical, and clinical data were collected for an analysis of CAPD-associated peritonitis, technique failure, drop-out from PD, and patient mortality. ♢

RESULTS

The peritonitis rate was 0.196 episodes per patient-year. Older age (>65 years) was the only identified risk factor associated with peritonitis. A multivariate Cox regression model demonstrated that technique failure occurred more often in patients experiencing peritonitis than in those free of peritonitis (p < 0.001). Kaplan-Meier analysis revealed that the group experiencing peritonitis tended to survive longer than the group that was peritonitis-free (p = 0.11). After multivariate adjustment, the survival advantage reached significance (hazard ratio: 0.64; 95% confidence interval: 0.46 to 0.89; p = 0.006). Compared with the peritonitis-free group, the group experiencing peritonitis also had more drop-out from PD (p = 0.03). ♢

CONCLUSIONS

The peritonitis rate was relatively low in the present investigation. Elderly patients were at higher risk of peritonitis episodes. Peritonitis independently predicted technique failure, in agreement with other reports. However, contrary to previous studies, all-cause mortality was better in patients experiencing peritonitis than in those free of peritonitis. The underlying mechanisms of this presumptive "peritonitis paradox" remain to be clarified.

Involvement of leptin in the progression of experimentally induced peritoneal fibrosis in mice

Leptin is a hormone mainly produced by white adipose cells, and regulates body fat and food intake by acting on hypothalamus. Leptin receptor is expressed not only in the hypothalamus but in a variety of peripheral tissues, suggesting that leptin has pleiotropic functions. In this study, we investigated the effect of leptin on the progression of peritoneal fibrosis induced by intraperitoneal injection of chlorhexidine gluconate (CG) every other day for 2 or 3 weeks in mice. This study was conducted in male C57BL/6 mice and leptin-deficient ob/ob mice. Peritoneal fluid, blood, and peritoneal tissues were collected 15 or 22 days after CG injection. CG injection increased the level of leptin in serum and peritoneal fluid with thickening of submesothelial compact zone in wild type mice, but CG-injected ob/ob mice attenuate peritoneal fibrosis, and markedly reduced the number of myofibroblasts, infiltrating macrophages, and blood vessels in the thickened submesothelial area. The 2-week leptin administration induced a more thickened peritoneum in the CG-injected C57BL/6 mice than in the PBS group. Our results indicate that an upregulation of leptin appears to play a role in fibrosis and inflammation during peritoneal injury, and reducing leptin may be a therapeutically potential for peritoneal fibrosis.

Pathophysiological changes to the peritoneal membrane during PD-related peritonitis: the role of mesothelial cells

The success of peritoneal dialysis (PD) is dependent on the structural and functional integrity of the peritoneal membrane. The mesothelium lines the peritoneal membrane and is the first line of defense against chemical and/or bacterial insult. Peritonitis remains a major complication of PD and is a predominant cause of technique failure, morbidity and mortality amongst PD patients. With appropriate antibiotic treatment, peritonitis resolves without further complications, but in some PD patients excessive peritoneal inflammatory responses lead to mesothelial cell exfoliation and thickening of the submesothelium, resulting in peritoneal fibrosis and sclerosis. The detrimental changes in the peritoneal membrane structure and function correlate with the number and severity of peritonitis episodes and the need for catheter removal. There is evidence that despite clinical resolution of peritonitis, increased levels of inflammatory and fibrotic mediators may persist in the peritoneal cavity, signifying persistent injury to the mesothelial cells. This review will describe the structural and functional changes that occur in the peritoneal membrane during peritonitis and how mesothelial cells contribute to these changes and respond to infection. The latter part of the review discusses the potential of mesothelial cell transplantation and genetic manipulation in the preservation of the peritoneal membrane.

A peritoneal dialysis regimen low in glucose and glucose degradation products results in increased cancer antigen 125 and peritoneal activation

BACKGROUND

Glucose and glucose degradation products (GDPs) in peritoneal dialysis fluids (PDFs) are both thought to mediate progressive peritoneal worsening.

METHODS

In a multicenter, prospective, randomized crossover study, incident continuous ambulatory peritoneal dialysis patients were treated either with conventional lactate-buffered PDF (sPD regimen) or with a regimen low in glucose and GDPs: Nutrineal×1, Extraneal×1, and Physioneal×2 (NEPP regimen; all solutions: Baxter Healthcare, Utrecht, The Netherlands). After 6 months, patients were switched to the alternative regimen for another 6 months. After 6 weeks of run-in, before the switch, and at the end of the study, 4-hour peritoneal equilibration tests were performed, and overnight effluents were analyzed for cells and biomarkers. Differences between the regimens were assessed by multivariate analysis corrected for time and regimen sequence.

RESULTS

The 45 patients who completed the study were equally distributed over both groups. During NEPP treatment, D(4)/D(0) glucose was lower (p < 0.01) and D/P creatinine was higher (p = 0.04). In NEPP overnight effluent, mesothelial cells (p < 0.0001), cancer antigen 125 (p < 0.0001), hyaluronan (p < 0.0001), leukocytes (p < 0.001), interleukins 6 (p = 0.001) and 8 (p = 0.0001), and vascular endothelial growth factor (VEGF, p < 0.0001) were increased by a factor of 2-3 compared with levels in sPD effluent. The NEPP regimen was associated with higher transport parameters, but that association disappeared after the addition of VEGF to the model. The association between NEPP and higher effluent levels of VEGF could not be attributed to glucose and GDP loads.

CONCLUSIONS

Study results indicate preservation of the mesothelium and increased peritoneal activation during NEPP treatment. Whether the increase in VEGF reflects an increase in mesothelial cell mass or whether it points to another, undesirable mechanism cannot be determined from the present study. Longitudinal studies are needed to finally evaluate the usefulness of the NEPP regimen for further clinical use.

Immunohistochemical study of pathological alterations of peritoneum in patients with terminal renal insufficiency and on peritoneal dialysis

BACKGROUND/AIM

During peritoneal dialysis (PD) an exchange of substances between blood and dialysate takes place through specific histological structures of peritoneum. Peritoneal double-layered serous membrane has, so far, mostly been studied with electron microscopy on experimental animals. The aim of this study was to assess integrity of peritoneal tissue in end-stage renal disease (ESRD) and PD patients using standard light microscopy and immunohistochemical methods.

METHODS

Peritoneal tissue biopsies were performed on 25 persons: 8 healthy donors during nephrectomy, 9 ESRD patients upon insertion of PD catheter, and 8 PD patients upon removal of the catheter for medical indications. The samples were fixed and prepared routinely for immunocytochemical staining by standardized streptavidin biotin AEC method using a LSAB2 HRP kit (Dako, Denmark) for collagen IV and analyzed by light microscopy.

RESULTS

We observed mesothelial detachment from lamina propria, duplicated basement membrane and much thicker blood vessel walls in ESRD and PD patients, compared to healthy subjects. Differences in histological structure, emphasized with immunostaining, indicated pathological alterations of peritoneal tissue in the renal patients.

CONCLUSIONS

Imunohistochemistry can be used in studying histological alterations of peritoneal tissue in ESRD and PD patients. This method may indicate possible problems in filtration and secretion processes in this tissue.

Peritoneal dialysis-associated peritonitis rates and outcomes in a national cohort are not improving in the post-millennium (2000-2007)

BACKGROUND

Peritoneal dialysis (PD)-related peritonitis remains the leading cause of technique failure and a significant cause of morbidity among PD patients. Rates in the literature vary, reflecting differences in study design and in populations. The objective of the present study was to determine peritonitis incidence and outcomes in Scotland and to compare them with national guidelines.

METHODS

All 10 adult renal units in Scotland prospectively collect data relating to peritonitis for all PD patients in Scotland. Complete audit data between 1 January 2000 and 31 December 2007 were analyzed for the study.

RESULTS

The 1918 peritonitis episodes in 38 106 PD treatment months yielded a national rate of 1 episode every 19.9 months. The UK Renal Association standard was met every year, but is not consistently improving. The median peritonitis-free survival was 526 days (95% confidence interval: 463 to 589 days). The spectrum of causative organisms reflected those in previous reports, with a culture-negative rate of 19.4%. Nationally, the cure rate was 74.6%, the refractory rate was 22.6%, and the death rate was 2.8%. Outcome varied by organism. Recurrences represented 9.3% of episodes, and technique failure occurred in 14.9%. The peritonitis rate was higher for continuous ambulatory PD patients than for automated PD patients (1 episode every 17.6 months vs 1 episode every 22.3 months, p < 0.001, relative risk: 1.27). There were significant differences between renal units.

CONCLUSIONS

This large national PD cohort met targets for peritonitis rates every year during the 8 years covered by the present report, but showed no consistent trend for improvement. Peritonitis remains the main cause of technique failure in Scotland. Peritonitis rates varied widely between the units, which suggests that we should look to the units and countries with lower peritonitis rates to see if we can adopt successful elements of their practice before resigning ourselves to our ongoing peritonitis burden.

Thalidomide prevents the progression of peritoneal fibrosis in mice

Thalidomide is clinically recognized as a therapeutic agent for multiple myeloma and has been known to exert anti-angiogenic actions. Recent studies have suggested the involvement of angiogenesis in the progression of peritoneal fibrosis. The present study investigated the effects of thalidomide on the development of peritoneal fibrosis induced by injection of chlorhexidine gluconate (CG) into the mouse peritoneal cavity every other day for 3 weeks. Thalidomide was given orally every day. Peritoneal tissues were dissected out 21 days after CG injection. Expression of CD31 (as a marker of endothelial cells), proliferating cell nuclear antigen (PCNA), vascular endothelial growth factor (VEGF), α-smooth muscle actin (as a marker of myofibroblasts), type III collagen and transforming growth factor (TGF)-β was examined using immunohistochemistry. CG group showed thickening of the submesothelial zone and increased numbers of vessels and myofibroblasts. Large numbers of VEGF-, PCNA-, and TGF-β-positive cells were observed in the submesothelial area. Thalidomide treatment significantly ameliorated submesothelial thickening and angiogenesis, and decreased numbers of PCNA- and VEGF-expressing cells, myofibroblasts, and TGF-β-positive cells. Moreover, thalidomide attenuated peritoneal permeability for creatinine, compared to the CG group. Our results indicate the potential utility of thalidomide for preventing peritoneal fibrosis.

Differential proteomic characterization between normal peritoneal fluid and diabetic peritoneal dialysate

BACKGROUND

Since the mechanism of comorbidity and mortality in peritoneal dialysis is unclear, a comparison of peritoneal dialysate and normal peritoneal fluid may provide clues to the biological and pathological processes involved in peritoneal damage.

METHODS

Peritoneal dialysate and control samples were collected from five diabetes mellitus (DM) patients and two patients receiving laparoscopic cholecystectomy. Proteins were separated by two-dimensional gel electrophoresis (2D-GE). After image analysis, altered gel spots between these two sample groups were subjected to tryptic digestion and mass spectrometry analysis. The results were searched against the NCBI database.

RESULTS

A total of 26 protein spots were considered altered in 2D-GE between the two sample groups. After western blotting confirmation, vitamin D-binding protein, haptoglobin and alpha-2-microglobulin were at higher levels in the DM samples, while complement C4-A and IGK@ protein were at lower levels compared to the control samples.

CONCLUSION

The loss of vitamin D-binding protein, haptoglobin and alpha-2-microglobulin may be due to a change in the permeability of the peritoneal membrane to middle-sized proteins or leakage from peritoneal inflammation. Lower levels of complement C4-A in dialysate may shed light on the beginning of peritoneal membrane scleroses.

Tissue-type plasminogen activator deficiency attenuates peritoneal fibrosis in mice

Peritoneal fibrosis (PF) is an important complication of peritoneal dialysis therapy. The present study was performed to examine the mechanisms of PF in view of the plasminogen activator (PA)/plasmin/matrix metalloproteinase (MMP) cascade. PF was induced in tissue-type PA (tPA) deficient mice and wild-type mice by intraperitoneal injection of chlorhexidine gluconate. Mice were killed on day 21, and tissue samples were taken. Histopathological studies were performed. Plasmin activity, gelatinases activity, and the levels of tPA, transforming growth factor-β1 (TGF-β1), and MMP-2 mRNA were determined. Protein levels of MMP-3, tissue inhibitor of metalloproteinases (TIMP)-1, -2, and -3, phospho-Smad3, membrane-type 1 (MT1)-MMP, and MT3-MMP were also studied. On day 21, tPA +/+ mice showed severe PF, whereas tPA −/− mice showed milder change. Submesothelial basement membranes were dissolved in tPA +/+ mice while they were relatively preserved in tPA −/− mice. The levels of macrophage infiltration, staining for α-smooth muscle actin (α-SMA) and collagen type III, and vascular density were all significantly lower in tPA −/− mice than in tPA +/+ mice. The levels of plasmin activity, pro- and active MMP-2, mRNA expression of tPA and TGF-β1, and phospho-Smad3 protein were also lower in tPA −/− mice. No difference was observed between the two groups concerning the protein levels of MMP-3, TIMP-1, TIMP-2, TIMP-3, MT1-MMP, or MT3-MMP. These results indicate that the presence of tPA enhances inflammation, angiogenesis, and fibrogenesis in the peritoneum of the PF model mice. Activation of the PA/plasmin/MMP cascade may play a pivotal role in the pathogenesis of PF.

Tissue Factor and Factor V Involvement in Rat Peritoneal Fibrosis

Objective

Fibrin deposition on the peritoneum has been frequently observed in peritoneal fibrosis induced by long-term peritoneal dialysis. The present study was conducted to clarify the contribution of factor Xa through tissue factor and factor V expression in peritoneal fibrosis.

Methods

Wistar rats were intraperitoneally injected with chlorhexidine gluconate (CG) every day. For the interventional study, the factor Xa inhibitor fondaparinux was subcutaneously administered. After 28 days of CG injection, peritoneal specimens were examined by immunohistochemical analyses and in situ hybridization.

Results

The peritoneal submesothelial compact zone was observed to be markedly thicker in the CG-injected groups than in the normal group, and that thickness was dose dependent. Immunohistochemical study revealed massive fibrin, fibronectin, and type IV collagen depositions in the CG-injected groups, which was markedly higher than that in the normal group. Macrophage infiltration and staining for tissue factor, factor V, factor X, and protease-activated receptor-2 were intense in the CG-injected groups and negative/trace in the normal group. Tissue factor and factor V mRNAs were abundant in cells in the thickened peritoneum. A double-labeling experiment revealed that tissue factor was observed mainly in macrophages, and factor V was abundantly distributed in the fibrotic tissue together with macrophages. Fondaparinux treatment decreased the thickness of submesothelial fibrotic tissue, and size and number of CD31-positive vessels.

Conclusion

These results suggest that expression of tissue factor and factor V in infiltrated macrophages, together with factor X deposition, may progress angiogenesis and accumulation of extracellular matrix components, partly via profibrotic and procoagulant mechanisms in the peritoneum after inflammatory stimulation.

Treatment for peritoneal dialysis-associated peritonitis

BACKGROUND

Peritonitis is a common complication of peritoneal dialysis (PD) and is associated with significant morbidity. Adequate treatment is essential to reduce morbidity and recurrence.

OBJECTIVES

To evaluate the benefits and harms of treatments for PD-associated peritonitis.

SEARCH STRATEGY

We searched the Cochrane Renal Group's specialised register, the Cochrane Central Register of Controlled Trials (CENTRAL, in The Cochrane Library), MEDLINE, EMBASE and reference lists without language restriction. Date of search: February 2005

SELECTION CRITERIA

All randomised controlled trials (RCTs) and quasi-RCTs assessing the treatment of peritonitis in peritoneal dialysis patients (adults and children) evaluating: administration of an antibiotic(s) by different routes (e.g. oral, intraperitoneal, intravenous); dose of an antibiotic agent(s); different schedules of administration of antimicrobial agents; comparisons of different regimens of antimicrobial agents; any other intervention including fibrinolytic agents, peritoneal lavage and early catheter removal were included.

DATA COLLECTION AND ANALYSIS

Two authors extracted data on study quality and outcomes. Statistical analyses were performed using the random effects model and the dichotomous results were expressed as relative risk (RR) with 95% confidence intervals (CI) and continuous outcomes as mean difference (WMD) with 95% CI.

MAIN RESULTS

We identified 36 studies (2089 patients): antimicrobial agents (30); urokinase (4), peritoneal lavage (1) intraperitoneal (IP) immunoglobulin (1). No superior antibiotic agent or combination of agents were identified. Primary response and relapse rates did not differ between IP glycopeptide-based regimens compared to first generation cephalosporin regimens, although glycopeptide regimens were more likely to achieve a complete cure (3 studies, 370 episodes: RR 1.66, 95% CI 1.01 to 3.58). For relapsing or persistent peritonitis, simultaneous catheter removal/replacement was superior to urokinase at reducing treatment failure rates (1 study, 37 patients: RR 2.35, 95% CI 1.13 to 4.91). Continuous IP and intermittent IP antibiotic dosing had similar treatment failure and relapse rates. IP antibiotics were superior to IV antibiotics in reducing treatment failure (1 study, 75 patients: RR 3.52, 95% CI 1.26 to 9.81). The methodological quality of most included studies was suboptimal and outcome definitions were often inconsistent. There were no RCTs regarding duration of antibiotics or timing of catheter removal.

AUTHORS' CONCLUSIONS

Based on one study, IP administration of antibiotics is superior to IV dosing for treating PD peritonitis. Intermittent and continuous dosing of antibiotics are equally efficacious. There is no role shown for routine peritoneal lavage or use of urokinase. No interventions were found to be associated with significant harm.

Treatment of peritoneal dialysis-associated peritonitis: a systematic review of randomized controlled trials

BACKGROUND

Peritonitis frequently complicates peritoneal dialysis. Appropriate treatment is essential to reduce adverse outcomes. Available trial evidence about peritoneal dialysis peritonitis treatment was evaluated.

SELECTION CRITERIA FOR STUDIES

The Cochrane CENTRAL Registry (2005 issue), MEDLINE (1966 to February 2006), EMBASE (1985 to February 2006), and reference lists were searched to identify randomized trials of treatments for patients with peritoneal dialysis peritonitis.

INTERVENTIONS

Trials of antibiotics (comparisons of routes, agents, and dosing regimens), fibrinolytic agents, peritoneal lavage, and intraperitoneal immunoglobulin.

OUTCOMES

Treatment failure, relapse, catheter removal, microbiological eradication, hospitalization, all-cause mortality, and adverse reactions.

RESULTS

36 eligible trials were identified: 30 trials (1,800 patients) of antibiotics; 4 trials (229 patients) of urokinase; 1 trial of peritoneal lavage (36 patients); and 1 trial of intraperitoneal immunoglobulin (24 patients). No superior antimicrobial class was identified. In particular, glycopeptides and first-generation cephalosporins were equivalent (3 trials, 387 patients; relative risk [RR], 1.84; 95% confidence interval [CI], 0.95 to 3.58). Simultaneous catheter removal/replacement was superior to urokinase at decreasing treatment failures (1 trial, 37 patients; RR, 2.35; 95% CI, 1.13 to 4.91). Continuous and intermittent intraperitoneal antibiotic dosing were equivalent regarding treatment failure (4 trials, 338 patients; RR, 0.69; 95% CI, 0.37 to 1.30) and relapse (4 trials, 324 patients; RR, 0.93; 95% CI, 0.63 to 1.39). One trial showed superiority of intraperitoneal antibiotics over intravenous therapy.

LIMITATIONS

The method quality of trials generally was suboptimal and outcome definitions were inconsistent. Small patient numbers led to inadequate power to show an effect. Interventions, such as optimal duration of antibiotic therapy, were not evaluated.

CONCLUSIONS

Trials did not identify superior antibiotic regimens. Intermittent and continuous antibiotic dosing are equivalent treatment strategies.

Smad7 transgene attenuates peritoneal fibrosis in uremic rats treated with peritoneal dialysis

Transforming growth factor beta (TGF-beta) plays a critical role in the pathogenesis of the peritoneal fibrosis that complicates long-term peritoneal dialysis (PD). We studied the TGF-beta/Smad signaling pathway in peritoneal fibrosis induced in uremic rats treated with PD and explored the therapeutic potential of Smad7 to prevent fibrogenesis. After subtotal nephrectomy, uremic rats were treated with peritoneal dialysis using 4.25% dextrose-containing fluid. The peritoneum of uremic rats treated with PD demonstrated fibrosis, increased TGF-beta expression, increased Smad2/3 activation, decreased Smad7 expression, and increased expression of fibrogenic and angiogenic factors. In addition, peritoneal function was impaired and its structure was altered, including a thickened submesothelial layer. In rats transfected with a Smad7 transgene using an ultrasound-microbubble-mediated system, peritoneal fibrosis was attenuated, peritoneal function was improved, and Smad2/3 activation was inhibited. We suggest that administration of Smad7 inhibits peritoneal fibrogenesis in uremic rats treated with PD by correcting the imbalance between downregulated Smad7 and activated Smad2/3. Blockade of the TGF-beta/Smad signaling pathway may represent a novel therapeutic approach to prevent peritoneal fibrosis in patients treated with PD.

Peritoneal Dialysis Fluid–Induced Angiogenesis in Rat Mesentery Is Increased by Lactate in the Presence or Absence of Glucose

Angiogenesis may be an important mechanism behind the functional deterioration of the peritoneum leading to ultrafiltration failure in peritoneal dialysis. The present study was designed to compare the angiogenic properties of lactate-, bicarbonate-, and pyruvate-buffered fluids, evaluated separately with and without glucose. Five different fluids (lactate and bicarbonate with and without 2.5% glucose and pyruvate without glucose) were studied for 5 weeks of twice-daily injections in rats. The respective buffers (40 mmol/l) were adjusted to pH 7.2, and sodium, chloride, calcium, and magnesium were present at standard concentrations. The mesenteric window model, based on observation of the translucent peritoneal sections of the small intestine mesentery, was used for immunohistochemical imaging of microvessels (RECA-1 antigen) and macrophages (ED1 and ED2 antigens). All fluids induced angiogenesis as compared with untreated controls. The lactate-buffered fluids induced larger vascularized zones than did their bicarbonate- and pyruvate-buffered counterparts. Angiogenesis was accompanied by a local recruitment of ED1 macrophages from blood. Addition of glucose to the lactate- and bicarbonate-buffered fluids did not seem to alter their pro-angiogenic properties. In conclusion, intraperitoneal exposure to lactate buffer, compared with bicarbonate, stimulates angiogenesis in the presence or absence of glucose.

TNP-470, an angiogenesis inhibitor, suppresses the progression of peritoneal fibrosis in mouse experimental model

BACKGROUND

In patients on long-term peritoneal dialysis (PD), angiogenesis and vasculopathy are observed in the peritoneum, and the degree of vascularization correlates with the area of fibrotic tissue, suggesting the involvement of angiogenesis in the progression of peritoneal fibrosis. The aim of the present study was to evaluate the effect of TNP-470, an anti-angiogenic compound, on the development of peritoneal fibrosis induced by chlorhexidine gluconate (CG).

METHODS

Peritoneal fibrosis was induced by injection of CG into peritoneal cavity of Institute for Cancer Research (ICR) mice. TNP-470 was injected subcutaneously with CG. Mice were sacrificed, and peritoneal tissues were dissected out at days eight and 16 after CG and TNP-470 injection. The expression patterns of CD31 (as a marker of endothelial cells), vascular endothelial cell growth factor (VEGF), alpha-smooth muscle actin (as a marker of myofibroblasts), heat shock protein 47 (HSP47), type III collagen, F4/80 (as a marker of mice macrophages), proliferating cell nuclear antigen (PCNA), and cyclin-dependent kinase 2 (Cdk2) were examined by immunohistochemistry.

RESULTS

CG-injected mice showed thickening of the submesothelial zone and increased number of vessels, myofibroblasts, and infiltrating macrophages. The expression levels of VEGF, type III collagen, and HSP47 were increased, and a large number of PCNA-positive cells and Cdk2-expressing cells were observed in the thickened submesothelial area. Treatment with TNP-470 suppressed the submesothelial zone thickening and reduced collagen III expression as well as angiogenesis. TNP-470 also decreased the number of VEGF-expressing cells, myofibroblasts, macrophages, PCNA-positive cells, and Cdk2-expressing cells.

CONCLUSION

Our results indicate the involvement of angiogenesis in the progression of peritoneal fibrosis, and suggest that TNP-470 may be potentially useful for the prevention of peritoneal fibrosis through inhibition of angiogenesis and suppression of myofibroblast proliferation.

Selective depletion of fibroblasts preserves morphology and the functional integrity of peritoneum in transgenic mice with peritoneal fibrosing syndrome

BACKGROUND

A peritoneal fibrosing syndrome (PFS) can progressively reduce peritoneal ultrafiltration during chronic peritoneal dialysis in patients with renal failure. The pathogenesis of PFS is unclear and the role of peritoneal fibroblasts has not been evaluated experimentally.

METHODS

We followed the fate of fibroblasts producing PFS in a mouse model using fibroblast-specific protein 1 (FSP1) as a marker. PFS was induced by daily peritoneal infusions of chlorhexidine gluconate (CHG) saline into transgenic mice expressing the thymidine kinase (Delta tk) gene under the control of the FSP1 promoter (FSP1.Delta tk mice). To demonstrate the role of fibroblasts in PFS, we treated these FSP1.Delta tk mice with a nucleoside analogue to induce DNA chain termination and fibroblast death.

RESULTS

Mice receiving peritoneal infusions of CHG saline every other day for 2 weeks developed increasing numbers of FSP1+ fibroblasts in the subserosal layers of the visceral peritoneum. Mac-3+ monocytes (macrophages) subsequently accumulated over the next 2 weeks in association with increased deposition of type I collagen and increased endothelial vascularity (CD31+) in these subserosal tissues. Since these peritoneal fibroblasts expressed monocyte chemoattractant protein-1 (MCP-1), heat shock protein 47 (HSP47), and vascular endothelial growth factor (VEGF), we suspect they were partially responsible for macrophage recruitment, matrix production, and the neoangiogenesis in the subserosal tissue. Treatment of PFS in FSP1.Delta tk transgenic mice with a nucleoside analogue selectively reduced the numbers of peritoneal fibroblasts and attenuated the attendant changes in peritoneal histology. Rescuing the peritoneal membrane from chronic thickening and neoangiogenesis by reducing the number of fibroblasts also preserved ultrafiltration.

CONCLUSION

Peritoneal fibroblasts play a pivotal role in PFS, and their deletion using a fibroblasts-specific transgene was effective in preventing peritoneal fibrogenesis.

Regulation of complement C3 and C4 synthesis in human peritoneal mesothelial cells by peritoneal dialysis fluid

Although complement is activated in the peritoneal cavity during chronic peritoneal dialysis (PD), little is known about its role in peritoneal defence and injury related to long-term PD. We examined the impact of glucose and commercial peritoneal dialysis solutions on complement expression in HPMCs obtained by primary culture from omental tissues of consented patients undergoing elective abdominal surgery. Constitutive expression of C3 and C4 mRNA in HPMCs was up-regulated upon exposure to 75 mm glucose in a time-dependent manner. C3 and C4 protein was secreted in both apical and basolateral directions. Glucose doses beyond 100 mm markedly down-regulated C3 and C4 expression, and stimulated LDH release dose-dependently. Such cytotoxic effects were attenuated using equivalent doses of mannitol instead of glucose. Treatment with conventional lactate-buffered dialysis solution gave rise to down-regulation of C3 and C4 expression, and heightened LDH release in HPMCs. These effects correlated with the glucose strength of the solution, persisted despite replacement with a bicarbonate-buffered solution, aggravated by glycated albumin, and were partially abrogated by supplementation with 10% fetal bovine serum in the culture system. Our findings suggest that the artificial conditions imposed by PD lead to alterations in local complement synthesis that have implications for the role of the peritoneal mesothelium in both inflammation and defence.

Antisense oligonucleotides against collagen-binding stress protein HSP47 suppress peritoneal fibrosis in rats

BACKGROUND

Peritoneal fibrosis is a serious complication in patients on continuous ambulatory peritoneal dialysis (CAPD), but the molecular mechanism of this process remains unclear. Heat shock protein 47 (HSP47), a collagen-specific molecular chaperone, is essential for biosynthesis and secretion of collagen molecules, and is expressed in the tissue of human peritoneal fibrosis. In the present study, we examined the effect of HSP47 antisense oligonucleotides (ODNs) on the development of experimental peritoneal fibrosis induced by daily intraperitoneal injections of chlorhexidine gluconate (CG).

METHODS

HSP47 antisense or sense ODNs were injected simultaneously with CG from day 14, after injections of CG alone. Peritoneal tissue was dissected out 28 days after CG injection. The expression patterns of HSP47, type I and type III collagen, alpha-smooth muscle actin (alpha-SMA), as a marker of myofibroblasts, ED-1 (as a marker of macrophages), and factor VIII were examined by immunohistochemistry.

RESULTS

In rats treated with CG alone, the submesothelial collagenous compact zone was thickened, where the expression levels of HSP47, type I and type III collagen and alpha-SMA were increased. Marked macrophage infiltration was also noted and the number of vessels positively stained for factor VIII increased in the CG-treated group. Treatment with antisense ODNs, but not sense ODNs, abrogated CG-induced changes in the expression of HSP47, type I and III collagen, alpha-SMA, and the number of infiltrating macrophages and vessels.

CONCLUSION

Our results indicate the involvement of HSP47 in the progression of peritoneal fibrosis and that inhibition of HSP47 expression might merit further clinical investigation for the treatment of peritoneal fibrosis in CAPD patients.

Connective tissue growth factor and its regulation in the peritoneal cavity of peritoneal dialysis patients

BACKGROUND

Connective tissue growth factor (CTGF) is a fibrogenic cytokine that is highly expressed in wound healing and fibrotic lesions. The role of transforming growth factor-beta (TGF-beta) in fibrosis is well documented, and the emerging understanding that its fibrogenic actions are mediated through CTGF has provided an attractive target molecule for the modulation of matrix overproduction in fibrotic disease. The involvement of CTGF in the pathogenesis of peritoneal membrane fibrosis in peritoneal dialysis (PD) patients has not been investigated, and so the aim of this study was to ascertain whether CTGF is produced in the peritoneal cavity of PD patients and to investigate its regulation by cytokines.

METHODS

Reverse transcription-polymerase chain reaction (RT-PCR), Northern blotting, and Western blotting were used to study CTGF expression by cultured human peritoneal mesothelial cells (HPMC) from peritoneal dialysis patients. Western blotting was used to detect CTGF expression in spent peritoneal dialysate from patients with and without peritonitis.

RESULTS

RT-PCR analysis demonstrated the expression of CTGF mRNA in cultured primay HPMCs isolated from spent peritoneal effluent. The production of the major 36 to 38 kD CTGF protein doublet by HPMC in addition to a 23 to 25 kD proteolytically processed form was confirmed by Western blotting. Several molecular weight forms of CTGF (18 to 38 kD) were also detected by Western blotting in peritoneal dialysate, with levels markedly elevated during episodes of peritonitis. Northern and Western blot analysis revealed that CTGF mRNA and protein production by HPMC was up-regulated by TGF-beta, with mRNA levels significantly increasing above the control (P < 0.01). In contrast, platelet-derived growth factor (PDGF), epidermal growth factor (EGF), and tumor necrosis factor-alpha (TNF-alpha) had no measurable effects on CTGF mRNA expression.

CONCLUSION

These results are the first to demonstrate the production of CTGF by HPMC and its presence in the peritoneal cavity of PD patients. The marked increase in CTGF levels by factors implicated in the development of peritoneal membrane fibrosis suggests its involvement in the underlying pathophysiologic mechanism(s).

3,4-Dideoxyglucosone-3-ene (3,4-DGE): a cytotoxic glucose degradation product in fluids for peritoneal dialysis

BACKGROUND

Bioincompatible glucose degradation products (GDPs) in fluids for peritoneal dialysis (PD) develop during sterilization and storage. Their biological activity has successfully been monitored through the use of various in vitro methods but their molecular and chemical nature is less well understood. Many GDPs are highly reactive carbonyl compounds. Although some of the identified GDPs are extremely cytotoxic, none of them actually possess cytotoxicity at the concentrations found in PD fluids. Thus, the GDP responsible for the toxicity in PD fluids has not yet been identified. The intention of the present work was to investigate to what extent the unsaturated dicarbonyl compound, 3,4-dideoxyglucosone-3-ene (3,4-DGE) was present in PD fluids, and if it could be responsible for the in vitro effects on L-929 fibroblast cells.

METHODS

A commercial preparation of 3,4-DGE and two different liquid chromatography methods were used for the chemical identification and quantification. In vitro bioincompatibility was determined as inhibition of cell growth using the L-929 fibroblast cell line.

RESULTS

3,4-DGE was present in conventionally manufactured PD fluids at a concentration of 9 to 22 micromol/L. In the newly developed PD fluid, Gambrosol trio, the concentrations were 0.3 to 0.7 micromol/L. When added as synthetic 3,4-DGE to cell growth media at the concentrations measured in conventional PD fluids, the inhibition of cell growth was significantly lower than for that seen with the conventional fluids. However, in the conventional PD fluids the total amount of 3,4-DGE available for toxic reactions most probably was higher than that measured, because 3,4-DGE was freshly recruited from a molecular pool when consumed. The speed of this recruitment was high enough to explain most of the growth inhibition seen for heat-sterilized PD fluids.

CONCLUSION

3,4-DGE is present in conventional PD fluids at a concentration between 9 and 22 micromol/L, and is the most biologically active of all GDPs identified to date. Thus, it is the main candidate to be held responsible for the clinical bioincompatibility caused by conventionally manufactured PD fluids.

Hemodynamic effects of peritoneal dialysis solutions on the rat peritoneal membrane: role of acidity, buffer choice, glucose concentration, and glucose degradation products

Conventional peritoneal dialysis fluids (PDF) are unphysiologic because of their hypertonicity, high glucose and lactate concentrations, acidic pH, and presence of glucose degradation products (GDP). Long-term exposure to conventional PDF may cause functional and structural alterations of the peritoneal membrane. New PDF have a neutral pH, a low GDP content, and contain bicarbonate or lactate as the buffer. Intravital microscopy was used to analyze the vasoactive effects of conventional and new PDF on the rat peritoneal membrane. A conventional, acidic pH, lactate-buffered 4.25% glucose PDF induced maximal vasodilation of mesenteric arteries, resulting in a doubling of the arteriolar flow and a 20% increase of the perfused capillary length per area. The hemodynamic effects of conventional PDF were similar after pH-adjustment with NaOH, indicating that acidity per se is not essential for the changes. Superfusion by a pH-neutral, lactate-buffered PDF with low GDP content caused only a transient arterial vasodilation despite continuous exposure, with a commensurate effect on arteriolar flow and capillary recruitment. Application of a pH-neutral, bicarbonate-buffered PDF with low GDP content did not affect the hemodynamic parameters. Resterilization of the bicarbonate solution increased GDP levels and completely restored the vasodilatory capacity. The corresponding 1.5% glucose PDF induced similar but less pronounced changes. Conventional PDF have important vasoactive effects on the peritoneal circulation, mainly because of the presence of GDP and transiently because of high lactate concentrations. Capillary recruitment may increase effective peritoneal vascular surface area. In addition, chronic vasodilation may induce structural adaptations in the blood vessel wall, contributing to vascular sclerosis. PDF with reduced GDP content induce no major hemodynamic effects and may thus have the potential to better preserve peritoneal vascular integrity.