Pathogenesis of Peritoneal Sclerosis

Inhibition of calpain9 attenuates peritoneal dialysis-related peritoneal fibrosis

Aim: Peritoneal dialysis is a common renal replacement method for end-stage renal disease. Long-term peritoneal dialysis leads to peritoneal dialysis-related peritoneal fibrosis, which leads to a cessation of treatment. Calpain is a protein belonging to calcium-dependent endopeptidase family and plays an important role in extracellular matrix remodeling. Here, we evaluated the effect of calpain in peritoneal dialysis-related peritoneal fibrosis.

Methods: We established two animal models of peritoneal fibrosis and inhibited the activity of Calpain, and then collected peritoneal tissue to evaluate the progress of fibrosis and the changes of Calpain and β-catenin. We obtained Rat peritoneal mesothelial cells and Human peritoneal mesothelial cell line and stimulated with TGF-β to produce extracellular matrix. Next we inhibited Calpain activity or reduced Calpain9 expression, and then assessed changes in extracellular matrix and β-catenin.

Results: Inhibition of calpain activity attenuated chlorhexidine glucose and peritoneal dialysis-induced peritoneal thickening and β-catenin expression in mice. In addition, compared with the control group, when primary rat peritoneal mesothelial cells or human peritoneal mesothelial cells were treated with transforming growth factor beta, down-regulation of calpain activity inhibited the expression of Fibronectin and Collagen I, and increased the expression of E-cadherin. These changes could be adjusted after silencing calpain9. Finally, calpain9 deficiency was associated with down-regulation of Fibronectin and β-catenin in human peritoneal mesothelial cells.

Conclusion: Our results suggest that calpain9 may be a key molecule in mediating peritoneal dialysis-related peritoneal fibrosis.

Role of IGF-1R in epithelial-mesenchymal transdifferentiation of human peritoneal mesothelial cells

BACKGROUND

Peritoneal fibrosis (PF) is caused by epithelial-mesenchymal transdifferentiation (EMT) in the peritoneum under high glucose (HG) conditions. The study aimed to explored the role of Insulin-like growth factor 1 receptor (IGF-1R) in the regulation of EMT in human peritoneal mesothelial cells (HPMCs).

METHODS

We used HG peritoneal dialysis fluid (PDF) to induce in vivo PF in mice, and treated HPMCs with HG in vitro to stimulate EMT.

RESULTS

In the mice, the higher the glucose concentration in the dialysate, the more obvious the peritoneal tissue thickening and the more that collagen was deposited. The in vitro study indicated that the expression of IGF-1R, α-SMA, vimentin was upregulated, while the expression of occludin, ZO-1, and E-cadherin was downregulated in HPMCs under HG and IGF-1R overexpression conditions. Conversely, the expression of IGF-1R, α-SMA, and vimentin was downregulated, while the expression of occludin, ZO-1, and E-cadherin was upregulated in IGF-1R-underexpressed HPMCs under HG conditions. The cell migration abilities were increased, while the cell adhesion abilities were reduced in HPMCs under HG and IGF-1R overexpression conditions. In contrast, cell migration abilities were reduced, while cell adhesion abilities were increased in IGF-1Runderexpressed HPMCs under HG conditions.

CONCLUSIONS

Targeting at IGF-1R may provide novel insights into the prevention and treatment of PF.

Biocompatible dialysis fluids for peritoneal dialysis

BACKGROUND

Biocompatible peritoneal dialysis (PD) solutions, including neutral pH, low glucose degradation product (GDP) solutions and icodextrin, have previously been shown to favourably influence some patient-level outcomes, albeit based on generally sub-optimal quality studies. Several additional randomised controlled trials (RCT) evaluating biocompatible solutions in PD patients have been published recently. This is an update of a review first published in 2014.

OBJECTIVES

This review aimed to look at the benefits and harms of biocompatible PD solutions in comparison to standard PD solutions in patients receiving PD.

SEARCH METHODS

The Cochrane Kidney and Transplant Specialised Register was searched up to 12 February 2018 through contact with the Information Specialist using search terms relevant to this review. Studies in the Specialised Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

All RCTs and quasi-RCTs in adults and children comparing the effects of biocompatible PD solutions (neutral pH, lactate-buffered, low GDP; neutral pH, bicarbonate(± lactate)-buffered, low GDP; glucose polymer (icodextrin)) in PD were included. Studies of amino acid-based solutions were excluded.

DATA COLLECTION AND ANALYSIS

Two authors extracted data on study quality and outcomes. Summary effect estimates were obtained using a random-effects model, and results were expressed as risk ratios and 95% confidence intervals (CI) for categorical variables, and mean differences (MD) or standardised mean differences (SMD) and 95% CI for continuous variables.

MAIN RESULTS

This review update included 42 eligible studies (3262 participants), including six new studies (543 participants). Overall, 29 studies (1971 participants) compared neutral pH, low GDP PD solution with conventional PD solution, and 13 studies (1291 participants) compared icodextrin with conventional PD solution. Risk of bias was assessed as high for sequence generation in three studies, allocation concealment in three studies, attrition bias in 21 studies, and selective outcome reporting bias in 16 studies.Neutral pH, low GDP versus conventional glucose PD solutionUse of neutral pH, low GDP PD solutions improved residual renal function (RRF) preservation (15 studies, 835 participants: SMD 0.19, 95% CI 0.05 to 0.33; high certainty evidence). This approximated to a mean difference in glomerular filtration rate of 0.54 mL/min/1.73 m2 (95% CI 0.14 to 0.93). Better preservation of RRF was evident at all follow-up durations with progressively greater preservation observed with increasing follow up duration. Neutral pH, low GDP PD solution use also improved residual urine volume preservation (11 studies, 791 participants: MD 114.37 mL/day, 95% CI 47.09 to 181.65; high certainty evidence). In low certainty evidence, neutral pH, low GDP solutions may make little or no difference to 4-hour peritoneal ultrafiltration (9 studies, 414 participants: SMD -0.42, 95% CI -0.74 to -0.10) which approximated to a mean difference in peritoneal ultrafiltration of 69.72 mL (16.60 to 122.00 mL) lower, and may increase dialysate:plasma creatinine ratio (10 studies, 746 participants: MD 0.01, 95% CI 0.00 to 0.03), technique failure or death compared with conventional PD solutions. It is uncertain whether neutral pH, low GDP PD solution use led to any differences in peritonitis occurrence, hospitalisation, adverse events (6 studies, 519 participants) or inflow pain (1 study, 58 participants: RR 0.51, 95% CI 0.24 to 1.08).Glucose polymer (icodextrin) versus conventional glucose PD solutionIn moderate certainty evidence, icodextrin probably reduced episodes of uncontrolled fluid overload (2 studies, 100 participants: RR 0.30, 95% CI 0.15 to 0.59) and augmented peritoneal ultrafiltration (4 studies, 102 participants: MD 448.54 mL/d, 95% CI 289.28 to 607.80) without compromising RRF (4 studies, 114 participants: SMD 0.12, 95% CI -0.26 to 0.49; low certainty evidence) which approximated to a mean creatinine clearance of 0.30 mL/min/1.73m2 higher (0.65 lower to 1.23 higher) or urine output (3 studies, 69 participants: MD -88.88 mL/d, 95% CI -356.88 to 179.12; low certainty evidence). It is uncertain whether icodextrin use led to any differences in adverse events (5 studies, 816 participants) technique failure or death.

AUTHORS' CONCLUSIONS

This updated review strengthens evidence that neutral pH, low GDP PD solution improves RRF and urine volume preservation with high certainty. These effects may be related to increased peritoneal solute transport and reduced peritoneal ultrafiltration, although the evidence for these outcomes is of low certainty due to significant heterogeneity and suboptimal methodological quality. Icodextrin prescription increased peritoneal ultrafiltration and mitigated uncontrolled fluid overload with moderate certainty. The effects of either neutral pH, low GDP solution or icodextrin on peritonitis, technique survival and patient survival remain uncertain and require further high quality, adequately powered RCTs.

Rapamycin inhibits epithelial-to-mesenchymal transition of peritoneal mesothelium cells through regulation of Rho GTPases

Epithelial-mesenchymal transition (EMT) of peritoneal mesothelial cells (PMCs) is a key process of peritoneal fibrosis. Rapamycin has been previously shown to inhibit EMT of PMCs and prevent peritoneal fibrosis. In this study, we investigated the undefined molecular mechanisms by which rapamycin inhibits EMT of PMCs. To define the protective effect of rapamycin, we initially used a rat PD model which was daily infused with 20 mL of 4.25% high glucose (HG) dialysis solution for 6 weeks to induce fibrosis. The HG rats showed decreased ultrafiltration volume and obvious fibroproliferative response, with markedly increased peritoneal thickness and higher expression of α-smooth muscle actin (α-SMA) and transforming growth factor-β1. Rapamycin significantly ameliorated those pathological changes. Next, we treated rat PMCs with HG to induce EMT and/or rapamycin for indicated time. Rapamycin significantly inhibited HG-induced EMT, which manifests as increased expression of α-SMA, fibronectin, and collagen I, decreased expression of E-cadherin, and increased mobility. HG increased the phosphorylation of PI3K, Akt, and mTOR. Importantly, rapamycin inhibits the RhoA, Rac1, and Cdc42 activated by HG. Moreover, rapamycin repaired the pattern of F-actin distribution induced by HG, reducing the formation of stress fiber, focal adhesion, lamellipodia, and filopodia. Thus, rapamycin shows an obvious protective effect on HG-induced EMT, by inhibiting the activation of Rho GTPases (RhoA, Rac1, and Cdc42).

Biocompatible dialysis fluids for peritoneal dialysis

BACKGROUND

The longevity of peritoneal dialysis (PD) is limited by high rates of technique failure, some of which stem from peritoneal membrane injury. 'Biocompatible' PD solutions have been developed to reduce damage to the peritoneal membrane.

OBJECTIVES

This review aimed to look at the benefits and harms of biocompatible PD solutions in comparison to standard PD solutions in patients receiving PD.

SEARCH METHODS

We searched the Cochrane Renal Group's Specialised Register (28 February 2013), 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

All randomised controlled trials (RCTs) and quasi-RCTs in adults and children comparing the effects of biocompatible PD solutions (neutral pH, lactate-buffered, low glucose degradation product (GDP); neutral pH, bicarbonate (± lactate)-buffered, low GDP; glucose polymer (icodextrin)) in PD were included. Studies of amino acid-based PD solutions were excluded.

DATA COLLECTION AND ANALYSIS

Two authors extracted data on study quality and outcomes (including adverse effects). The authors contacted investigators to obtain missing information. Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for categorical variables, and mean difference (MD) or standardised mean difference (SMD) and 95% CI for continuous variables.

MAIN RESULTS

Thirty-six eligible studies (2719 patients) were identified: Neutral pH, lactate-buffered/bicarbonate (± lactate)-buffered, low GDP PD solution (24); icodextrin (12). Allocation methods and concealment were generally incompletely reported, and adequate in only ten studies (27.8%). Patients lost to follow-up ranged from 0% to 83.4%. Neutral pH, low GDP versus conventional glucose PD solutionBased on generally sub-optimal quality evidence, the use of neutral pH, low GDP PD solutions was associated with larger urine volumes at the end of the studies, up to three years of therapy duration (7 studies, 520 patients: MD 126.39 mL/d, 95% CI 26.73 to 226.05). Improved preservation of residual renal function was evident in studies with greater than 12 month follow-up (6 studies, 360 patients: SMD 0.31, 95% CI 0.10 to 0.52). There was no significant effect on peritonitis, technique failure or adverse events with the use of neutral pH, low GDP PD solutions. Glucose polymer (icodextrin) versus conventional glucose PD solutionThere was a significant reduction in episodes of uncontrolled fluid overload (2 studies, 100 patients: RR 0.30, 95% CI 0.15 to 0.59) and improvement in peritoneal ultrafiltration (4 studies, 102 patients, MD 448.54 mL/d, 95% CI 289.28 to 607.80) without compromising residual renal function (4 studies, 114 patients: SMD 0.12, 95% CI -0.26 to 0.49) or urine output (3 studies, 69 patients: MD -88.88 mL/d, 95% CI -356.88 to 179.12) with icodextrin use. A comparable incidence of adverse events with the icodextrin (four studies) was reported.

AUTHORS' CONCLUSIONS

Based on generally sub-optimal quality studies, use of neutral pH, low GDP PD solution led to greater urine output and higher residual renal function after use exceeded 12 months. Icodextrin prescription improved peritoneal ultrafiltration and mitigated uncontrolled fluid overload. There were no significant effects on peritonitis, technique survival, patient survival or harms identified with their use. Based on the best available evidence, the use of these 'biocompatible' PD solutions resulted in clinically relevant benefits without added risks of harm.

The impact of neutral-pH peritoneal dialysates with reduced glucose degradation products on clinical outcomes in peritoneal dialysis patients

Neutral-pH peritoneal dialysates, with reduced glucose degradation products (GDPs), have been developed to reduce peritoneal membrane damage. Here our review evaluated the impact of these solutions on clinical outcomes using data from The Cochrane CENTRAL Registry, MEDLINE, Embase, and reference lists for randomized trials of biocompatible solutions. Summary estimates of effect were obtained using a random-effects model of 20 eligible trials encompassing 1383 patients. The quality of studies was generally poor, such that 13 studies had greater than a 20% loss to follow-up and only 3 trials reported adequate concealment of allocation. Use of neutral-pH dialysates with reduced GDPs resulted in larger urine volumes (7 trials; 520 patients; mean difference 126 ml/day, 95% CI 27-226), improved residual renal function after 12 months (6 trials; 360 patients; standardized mean difference 0.31, 95% confidence interval 0.10-0.52), and a trend to reduced inflow pain (1 trial; 58 patients; relative risk 0.51, 95% CI 0.24-1.08). However, there was no significant effect on body weight, hospitalization, peritoneal solute transport rate, peritoneal small-solute clearance, peritonitis, technique failure, patient survival, or adverse events. No significant harms were identified. Thus, based on generally poor quality trials, the use of neutral-pH peritoneal dialysates with reduced GDPs resulted in greater urine volumes and residual renal function after 12 months, but without other clinical benefits. Larger, better-quality studies are needed for accurate evaluation of the impact of these newer dialysates on patient-level hard outcomes.

Inflammation and the peritoneal membrane: causes and impact on structure and function during peritoneal dialysis

Peritoneal dialysis therapy has increased in popularity since the end of the 1970s. This method provides a patient survival rate equivalent to hemodialysis and better preservation of residual renal function. However, technique failure by peritonitis, and ultrafiltration failure, which is a multifactorial complication that can affect up to 40% of patients after 3 years of therapy. Encapsulant peritoneal sclerosis is an extreme and potentially fatal manifestation. Causes of inflammation in peritoneal dialysis range from traditional factors to those related to chronic kidney disease per se, as well as from the peritoneal dialysis treatment, including the peritoneal dialysis catheter, dialysis solution, and infectious peritonitis. Peritoneal inflammation generated causes significant structural alterations including: thickening and cubic transformation of mesothelial cells, fibrin deposition, fibrous capsule formation, perivascular bleeding, and interstitial fibrosis. Structural alterations of the peritoneal membrane described above result in clinical and functional changes. One of these clinical manifestations is ultrafiltration failure and can occur in up to 30% of patients on PD after five years of treatment. An understanding of the mechanisms involved in peritoneal inflammation is fundamental to improve patient survival and provide a better quality of life.

Abdominal cocoon in an adolescent male patient

Abdominal cocoon is a rare cause of bowel obstruction. The condition was first described three decades ago and is found mainly among adolescent females in tropical and sub-tropical countries. It is characterized by a thick fibrous membrane encapsulating the small intestines partially or completely. Patients present with features of intestinal obstruction and diagnosis is usually made intraoperatively. Surgical excision of the membrane and adhesiolysis result in complete recovery. We report on an adolescent male patient who had acute intestinal obstruction due to abdominal cocoon detected at surgery.

Thalidomide suppresses sclerosing encapsulating peritonitis in a rat experimental model

Peritoneal dialysis is an alternative treatment of patients with end-stage renal disease. Sclerosing encapsulating peritonitis is a life-threatening complication of continuous ambulatory peritoneal dialysis. The aim of the present study was to evaluate the effect of thalidomide, which is used for the treatment of various inflammatory and autoimmune diseases, on the development of sclerosing encapsulating peritonitis induced by chlorhexidine gluconate (CG). A peritoneal fibrosis model was established using rats treated intraperitoneally with injections of CG. Thalidomide was administered orally at a dose of 100 mg/kg three times per week. When compared with CG-treated rats, thalidomide (100 mg/kg orally)-treated mice subjected to CG-induced peritoneal fibrosis experienced a significantly lower rate in the extent and severity of histological signs of peritoneal injury. Thalidomide also caused a substantial reduction of 1) the rise in myeloperoxidase activity (mucosa); 2) the expression in the tissue of TNF-alpha, IL-1beta, transforming growth factor-beta, and vascular endothelial growth factor; 3) the increase in staining (immunohistochemistry) for nitrotyrosine and for poly(ADP ribose), as well as 4) the nuclear factor-kappaB activation caused by CG in the peritoneum. Thus, thalidomide treatment reduces the degree of peritoneal fibrosis caused by CG. We propose that this evidence may help clarify the potential therapeutic actions of thalidomide in patients with peritoneal fibrosis.

HGF and BMP-7 ameliorate high glucose-induced epithelial-to-mesenchymal transition of peritoneal mesothelium

Over time, peritoneal dialysis results in functional and structural alterations of the peritoneal membrane, but the underlying mechanisms and whether these changes are reversible are not completely understood. Here, we studied the effects of high levels of glucose, which are found in the dialysate, on human peritoneal mesothelial cells (HPMCs). We found that high concentrations of glucose induced epithelial-to-mesenchymal transition (EMT) of HPMC, suggested by decreased expression of E-cadherin and increased expression of alpha-smooth muscle actin, fibronectin, and type I collagen and by increased cell migration. Normalization of glucose concentration on day 2 reversed the phenotypic transformation, but the changes were irreversible after 7 d of stimulation with high glucose. In addition, exposure of HPMC to high glucose resulted in a decreased expression of the antifibrotic cytokines, hepatocyte growth factor (HGF) and bone morphogenic protein 7 (BMP-7). Exogenous treatment with HGF resulted in a dosage-dependent prevention of high glucose-induced EMT. Both BMP-7 peptide and gene transfection with an adenoviral vector of BMP-7 also protected HPMCs from EMT. Furthermore, adenoviral BMP-7 transfection decreased peritoneal EMT and ameliorated peritoneal thickening in an animal model of peritoneal dialysis. In summary, high concentrations of glucose induce a reversible EMT of HPMCs, associated with decreased production of HGF and BMP-7. Treatment of HPMCs with HGF or BMP-7 blocks high glucose-induced EMT, and BMP-7 ameliorates peritoneal fibrosis in an animal model of peritoneal dialysis.