Peritoneal Injury by Methylglyoxal in Peritoneal Dialysis

Background

Peritoneal dialysis (PD) is a common treatment for patients with reduced or absent renal function. Long-term PD leads to peritoneal injury with structural changes and functional decline, such as ultrafiltration loss. At worst, peritoneal injury leads to encapsulating peritoneal sclerosis, a serious complication of PD. Glucose degradation products contained in PD fluids contribute to the bioincompatibility of conventional PD fluids. Methylglyoxal (MGO) is an extremely toxic glucose degradation product. The present study examined the injurious effect of MGO on peritoneum in vivo.

Methods

Male Sprague–Dawley rats ( n = 6) were administered PD fluids (pH 5.0) containing 0, 0.66, 2, 6.6, or 20 mmol/L MGO every day for 21 days. On day 22, peritoneal function was estimated by the peritoneal equilibration test. Drained dialysate was analyzed for type IV collagen-7S, matrix metalloproteinase (MMP), and vascular endothelial growth factor (VEGF). Histological analysis was also performed.

Results

In rats receiving PD fluids containing more than 0.66 mmol/L MGO, peritoneal function decreased significantly and levels of type IV collagen-7S and MMP-2 in drained dialysate increased significantly. In the 20-mmol/L MGO-treated rats, loss of body weight, expression of VEGF, thickening of the peritoneum, and formation of abdominal cocoon were induced. MMP-2 and VEGF were produced by infiltrating cells in the peritoneum. Type IV collagen was detected in basement membrane of microvessels.

Conclusion

MGO induced not only peritoneal injury but also abdominal cocoon formation in vivo. The decline of peritoneal function may result from reconstitution of microvessel basement membrane or neovascularization.

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.

Methylglyoxal Induced Basophilic Spindle Cells with Podoplanin at the Surface of Peritoneum in Rat Peritoneal Dialysis Model

Peritoneal dialysis (PD) is a common treatment for patients with reduced or absent renal function. Long-term PD leads to peritoneal injury with structural changes and functional decline. At worst, peritoneal injury leads to encapsulating peritoneal sclerosis (EPS), which is a serious complication of PD. In order to carry out PD safely, it is important to define the mechanism of progression of peritoneal injury and EPS. We prepared rat models of peritoneal injury by intraperitoneal administration of glucose degradation products, such as methylglyoxal (MGO) or formaldehyde (FA), chlorhexidine gluconate (CG), and talc. In rats treated with MGO, peritoneal fibrous thickening with the appearance of basophilic spindle cells with podoplanin, cytokeratin, and α-smooth muscle actin at the surface of the peritoneum was observed. These cells may have been derived from mesothelial cells by epithelial-to-mesenchymal transition. In FA- or CG-treated rats, the peritoneum was thickened, and mesothelial cells were absent at the surface of the peritoneum. The CG- or MGO-treated rats presented with a so-called abdominal cocoon. In the talc-treated rats, extensive peritoneal adhesion and peritoneal thickening were observed. MGO-induced peritoneal injury model may reflect human histopathology and be suitable to analyze the mechanism of progression of peritoneal injury and EPS.

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.

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.

Development of a Peritoneal Sclerosis Rat Model Using a Continuous-Infusion Pump

Objective

Encapsulating peritoneal sclerosis (EPS) is a serious complication of continuous ambulatory peritoneal dialysis. Previous studies have created peritoneal sclerosis rat models using daily intraperitoneal injection of chlorhexidine gluconate (CG), but this technique is cumbersome and thickening of the peritoneum makes it difficult to evaluate the injection site. We therefore aimed to make a rat model using a continuous-infusion pump.

Methods

Various concentrations of CG (5%, 8%, 10%, 12%, and 14%) in ethanol were dissolved in saline within the infusion pumps, each of which was placed in the lower abdominal cavity of a male Wister rat. After a peritoneal equilibration test was performed, the rats were sacrificed and the lower anterior parietal and visceral peritoneum was removed. Each excised peritoneum was analyzed by macroscopic and microscopic examinations, including immunohistochemistry for the expression of transforming growth factor-beta 1 (TGF-β1), vascular endothelial growth factor (VEGF), and alpha-smooth muscle actin (αSMA). The results were compared with those of control rats injected with ethanol dissolved in saline within the infusion pump and with no-pump rats.

Results

Two of the 5 rats in the 12% CG group and 3 of the 5 rats in the 14% CG group died of ileus within 14 days. All the rats in the 5%, 8%, and 10% CG groups survived to 28 days. Macroscopic examination in the 10% CG group showed bowel dilatation, bowel adhesion, and bloody ascites, similar to those seen in human EPS patients. All rats in each CG group showed the same extent of thickening of the submesothelial compact zone, proliferation of collagen fibers, and presence of numerous cells and neovascularization. Within same CG groups, an equal degree of thickening was observed at all sites of the peritoneum. TGF-β1, VEGF, and αSMA were highly expressed in the peritoneum of the 10% CG group.

Conclusion

We developed a novel method of creating a peritoneal sclerosis rat model using a continuous-infusion pump. Our technique is simple and highly reproducible, and will be useful in the study of peritoneal sclerosis mechanisms.

Relationship Between Effluent Levels of ?2-Microglobulin and Peritoneal Injury Markers in 7.5% Icodextrin-Based Peritoneal Dialysis Solution

The removal of low molecular weight proteins such as beta(2)-microglobulin (beta(2)MG) is accelerated by using a 7.5% icodextrin-based peritoneal dialysis solution (ICO) dwell. To examine the possibility of peritoneal injury in ICO, we investigated the relationship between beta(2)MG and the injury markers in effluent. Sixteen ICO-treated patients (11 male and five female, mean age 50.1 +/- 10.9 years) with continuous ambulatory peritoneal dialysis (CAPD; mean duration 54.6 +/- 30.8 months) were studied. The patients were treated with ICO 2 L and 2.27% glucose-based solution 2 L for an 8-h dwell and the effluent was collected. We investigated the correlations between beta(2)MG and the injury markers (e.g. hyaluronic acid [HA], interleukin-6 [IL-6], matrix metalloproteinase-2 [MMP-2]) in each effluent sample. The beta(2)MG level in the ICO effluent was 8978 +/- 2431 microg/L, significantly higher than in the 2.27% glucose-based solution effluent (6454 +/- 2956 microg/L; P = 0.0032). The levels of HA and MMP-2 in ICO effluent were significantly higher than those in the 2.27% glucose-based solution effluent (P = 0.00214, P = 0.0113, respectively). There was a trend toward higher IL-6-values in ICO effluent, although no significant differences were seen. There were positive correlations between levels of various injury markers and beta(2)MG. We propose that the subclinical injury of the peritoneum by ICO treatment may accelerate peritoneal permeability to increase beta(2)MG in effluent. ICO's biocompatibility might not be superior to that of glucose-based solution.

Activation of matrix metalloproteinase-2 causes peritoneal injury during peritoneal dialysis in rats

BACKGROUND

Sclerosing peritonitis (SP) and encapsulating peritoneal sclerosis (EPS) are serious complications of continuous ambulatory peritoneal dialysis. Although we have shown previously that matrix metalloproteinase-2 (MMP-2) is increased in peritoneal injury leading to SP/EPS, most of the MMP-2 in the dialysate drained from the peritoneal cavity was the latent form that was lacking activity. In the present study, we investigated whether MMP-2 causes peritoneal injury.

METHODS

To create an animal model of peritoneal injury, we administered intraperitoneally chlorhexidine gluconate to rats. Dialysate drained from these rats was analysed by gelatin zymography and MMP-2 activity was analysed by an in situ film zymography method. In vitro myofibroblasts were cultured in collagen three-dimensional culture and then MMP-2 in conditioned medium from the culture was analysed by gelatin zymography.

RESULTS

Zymographic analysis revealed that latent form MMP-2 levels were high in the dialysate from peritoneal injury rats, whereas the active form was barely detectable. MMP-2 activity in the peritoneal tissue of the peritoneal injury rats was strongly detected by in situ film zymography. In vitro myofibroblasts were promoted to produce MMP-2 and to activate MMP-2 in collagen three-dimensional culture.

CONCLUSIONS

In the present model, most of the MMP-2 was in the latent form, but activation of MMP-2 was promoted in the peritoneum during peritoneal injury. Activated MMP-2 may be associated with the progression of peritoneal injury.