Effects of peritoneal hyaluronidase treatment on transperitoneal solute and fluid transport in the rat

Replacement of Glucose with N-Acetylglucosamine in Peritoneal Dialysis Fluid—Experimental Study in Rats

Background

Glucose is still used as an osmotic solute in peritoneal dialysis fluids, despite evidence of its local (peritoneal) and systemic toxicities. However a constant search is underway for a new, more biocompatible osmotic solute for peritoneal dialysis fluids.

Objective

The present study evaluated N-acetylglucosamine (NAG) in a concentration of 220 mmol/ L as an alternative to glucose for the osmotic solute in peritoneal dialysis fluid, during chronic peritoneal dialysis in rats.

Methods

For 8 weeks, male Wistar rats were infused with glucose-based or NAG-based dialysis fluid. Intraperitoneal inflammation and peritoneal permeability and morphology were evaluated in all rats during the study.

Results

Repeated intraperitoneal infusion of the NAG-based dialysis fluid resulted in a weaker intra-abdominal inflammatory reaction as compared with the reaction in rats infused with glucose-based dialysis solution. At the end of the study, the concentration of hyaluronan in the peritoneal interstitium obtained from NAG-treated rats was higher than that found in the interstitium taken from animals exposed to dialysis fluid containing glucose. Also, peritoneal permeability to total protein was lower in NAG-treated rats.

Conclusion

As an alternative to glucose, NAG used for the osmotic solute in peritoneal dialysis solution decreases the intraperitoneal inflammatory reaction induced by the process of peritoneal dialysis and, indirectly (owing to the increased hyaluronan content in the peritoneal interstitium), diminishes peritoneal permeability to protein.

3,4-DGE in Peritoneal Dialysis Fluids Cannot be Found in Plasma after Infusion into the Peritoneal Cavity

Objective

Glucose degradation products (GDPs) are important in the outcome of peritoneal dialysis (PD) treatment. 3,4-dideoxyglucosone-3-ene (3,4-DGE) is the most cytotoxic GDP found in conventionally manufactured fluids and may, in addition, be recruited from 3-deoxyglucosone (3-DG). It is not known what happens with those GDPs in patients during PD. The aim of this study was to investigate if the 3,4-DGE and 3-DG in PD fluids can be found in plasma during treatment.

Design

PD patients were dialyzed with a conventional PD fluid containing 43 μmol/L 3,4-DGE and 281 μmol/L 3-DG. Parallel experiments were performed in rats as well as in vitro with human plasma. The rats were dialyzed with a PD fluid containing 100 μmol/L 3,4-DGE and 200 μmol/L 3-DG.

Results

The concentration of 3,4-DGE in the peritoneum decreased at a much higher rate than 3-DG during the dwell. 3,4-DGE was not, however, detected in the plasma of patients or rats during dialysis. The concentration of 3-DG in plasma peaked shortly after infusion of the fluid to the peritoneal cavity. The concentration of 3,4-DGE during experimental incubation in plasma decreased rapidly, while the concentration of 3-DG decreased only 10% as rapidly or less.

Conclusion

3,4-DGE could not be detected in plasma from either PD patients or rats during dialysis. This is presumably due to its high reactivity. 3-DG may, on the other hand, pass through the membrane and be detected in the blood.

Physiological Properties of the Peritoneum in an Adult Peritoneal Dialysis Population over a Three-Year Period

Objectives

To describe the physiological properties of the peritoneal membrane in adult patients treated with peritoneal dialysis (PD) and to analyze the effects of patient characteristics and time.

Design

Observational study.

Setting

Department of Nephrology at the Sahlgrenska University Hospital.

Method

Peritoneal function was analyzed by the Personal Dialysis Capacity (PDC) test, based on the three-pore theory of capillary transport. The functional PDC variables are absorption, large-pore flow, and the area parameter (A0/Δx), which determines the diffusion of small solutes. The ultra-filtration (UF) coefficient is determined mainly by A0/Δx.

Patients

All patients ( n = 280) who had at least one PDC test done between September 1990 and August 1999.

Results

In 249 patients examined soon after start of PD, area was 19000 (SD 7100) cm2/cm/1.73 m2, large-pore flow 0.112 (SD 0.052) mL/min/1.73 m2, and the UF coefficient 0.071 (SD 0.032) mL/minute/mmHg/1.73 m2. Absorption was 1.54 (SD +2.64, –0.97) mL/min/1.73 m2. Large-pore flow was greater in patients with severe comorbidity than in patients with fewer comorbid conditions. Elderly patients had a lower UF coefficient than did younger patients ( p < 0.05). Repeated PDC tests were performed in 208 patients during a mean observation time of 18.4 months. There was a slight increase in the slope of the area-versus-time curve of 54 cm2/cm/1.73 m2 per month (approximately 10% after 3 years, p < 0.01); all other parameters remained constant.

Conclusion

Patient characteristics have an impact on peritoneal performance already at the start of dialysis. Peritoneal function can remain essentially stable during medium long-term PD.

Biodegradable hyaluronan hydrogel coatings on acellular dermis grafts-A potential strategy to improve biologic graft durability in hernia repair application

Biologic grafts used in hernia repair undergo rapid cellular infiltration and remodeling, but their premature degradation often results in hernia recurrence. We hypothesize that a temporary barrier that prevents infiltration of acute inflammatory cells into the graft during the initial 4 weeks of implantation could mitigate graft degradation. The purpose of this study is to design tyramine-substituted hyaluronan (THA) hydrogel coatings with tunable degradation properties, as a means to develop a resorbable barrier for human acellular dermis grafts (HADM). THA plugs prepared at different cross-linking densities, by varying cross-linking agent concentration (0.0001-0.0075% H₂ O₂ ), demonstrated varying rates of in vitro degradation (25 U/mL hyaluronidase, 48 h). Based on these results, HADM grafts were coated with THA at three cross-linking densities (0.0001%, 0.00075%, and 0.003% H₂ O₂ ) and THA coating degradation was evaluated in vitro (25 U/mL hyaluronidase, 48 h) and in vivo (rat intraperitoneal implantation, 1-4 weeks). THA coatings degraded in vitro and in vivo with the lowest cross-linking density (0.0001% H₂ O₂ ), generally showing greater degradation as evidenced by significant decrease in coating cross-sectional area. However, all three coatings remained partially degraded after 4 weeks of in vivo implantation. Alternate strategies to accelerate in vivo degradation of THA coatings are required to allow investigation of the study hypothesis. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2664-2672, 2019.

Regulation of synthesis and roles of hyaluronan in peritoneal dialysis

Hyaluronan (HA) is a ubiquitous extracellular matrix glycosaminoglycan composed of repeated disaccharide units of alternating D-glucuronic acid and D-N-acetylglucosamine residues linked via alternating β-1,4 and β-1,3 glycosidic bonds. HA is synthesized in humans by HA synthase (HAS) enzymes 1, 2, and 3, which are encoded by the corresponding HAS genes. Previous in vitro studies have shown characteristic changes in HAS expression and increased HA synthesis in response to wounding and proinflammatory cytokines in human peritoneal mesothelial cells. In addition, in vivo models and human peritoneal biopsy samples have provided evidence of changes in HA metabolism in the fibrosis that at present accompanies peritoneal dialysis treatment. This review discusses these published observations and how they might contribute to improvement in peritoneal dialysis.

3,4-Dideoxyglucosone-3-Ene in Peritoneal Dialysis Fluids Infused into the Peritoneal Cavity Cannot be Found in Plasma

Objective

Glucose degradation products (GDPs) are important for the outcome of peritoneal dialysis (PD) treatment. The most cytotoxic GDP found in conventionally manufactured fluids, 3,4-dideoxyglucosone-3-ene (3,4-DGE), may in addition be recruited from 3-deoxyglucosone (3-DG). What happens with the GDPs in the fluid infused into patients during PD is not known. We investigated whether 3,4-DGE and 3-DG in PD fluid can be found in plasma during treatment.

Design

Patients on PD were dialyzed with a conventional PD fluid containing 43 μmol/L 3,4-DGE and 281 μmol/L 3-DG. Parallel experiments were performed in rats and in vitro with human plasma. The rats were dialyzed with a PD fluid containing 100 μmol/L 3,4-DGE and 200 μmol/L 3-DG.

Results

The 3,4-DGE concentration in the peritoneum declined at a much higher rate during the dwell than did the 3-DG concentration. However, 3,4-DGE was not detected in the plasma of patients or of rats during dialysis. The 3-DG concentration in plasma peaked shortly after infusion of fluid into the peritoneal cavity. The 3,4-DGE concentration during experimental incubation in plasma declined rapidly; the 3-DG concentration declined only 10% as rapidly (or less).

Conclusion

During dialysis, 3,4-DGE could not be detected in plasma of either PD patients or rats, presumably because of its high reactivity. On the other hand, 3-DG may pass through the membrane and be detected in the blood.

Similitude of transperitoneal permeability in different rodent species

Transgenic mice facilitate mechanistic studies of altered peritoneal transport, but the majority of transport studies have been carried out in rats. We hypothesized that mouse transport parameters, normalized to the peritoneal contact area, would be similar to those of the rat. To address this, we affixed small (∼10-mm diameter) plastic chambers to the serosa of the abdominal wall of anesthetized CD1 and C57BL mice. The chamber constrained transfer across the area of the chamber base and facilitated mixing, volumetric, and concentration measurements vs. time for mannitol, serum albumin, and osmotic and hydrostatic pressure-driven convection. The mass transfer coefficient of mannitol (MTCM) and of serum albumin (MTCBSA), hydrostatic pressure-driven flux ( JP), and osmotic filtration ( Josm) were calculated from the time-dependent volume and concentration data. The units of all parameters (μl·min−1·cm−2) were compared with previously derived parameters from SD rats with a one-way ANOVA. Results indicated small but significant differences in MTCBSA(x102): CD1, 9.72 ± 1.97, n = 6; C57BL, 7.13 ± 1.52, n = 10; rat, 12.5 ± 1.6, n = 17 ( P = 0.03). ANOVAs of all other parameters were not significant and confirmed our hypothesis: MTCM(CD1, 3.20 ± 0.38, n = 7; C57BL, 2.34 ± 0.41, n = 6; rat, 2.72 ± 0.23 n = 19), JP(CD1, 0.77 ± 0.15, n = 10; C57BL, 0.33 ± 0.13, n = 15; rat, 0.51 ± 0.16, n = 9), or Josm(CD1, 0.92 ± 0.35, n = 6; C57BL, 0.49 ± 0.35, n = 6; rat 1.72 ± 0.35, n = 6). We conclude that elimination of the variable peritoneal transfer area normalizes calculated transport characteristics and facilitates comparison between species.

Transvascular protein transport in mice lacking endothelial caveolae

Caveolae are Ω-shaped vesicular structures postulated to play a role in transvascular protein transport. Studies on mice lacking endothelial caveolae, caveolin-1 knockout (Cav-1-KO) mice, indicate increased macromolecular transport rates. This was postulated to be due to the appearance of an alternative pathway. The present study tested whether an alternative pathway had appeared in Cav-1-KO mice. Male Cav-1-KO ( n = 12) and male control mice ( n = 13) were intubated and anesthetized using 2% isoflurane.125I-labeled albumin,131I-labeled immunoglobulin M (IgM), and polydisperse FITC-Ficoll were administered intravenously. During tracer administration, a 90-min peritoneal dialysis dwell was performed. Clearance of tracers to dialysate and permeability-surface area product for glucose were assessed. Transvascular protein transport was higher in Cav-1-KO compared with control mice. Albumin clearance from plasma to peritoneum was 0.088 ± 0.008 μl/min in control and 0.179 ± 0.012 μl/min in Cav-1-KO ( P = 0.001) mice. IgM clearance was 0.049 ± 0.003 and 0.083 ± 0.010 μl/min in control and Cav-1-KO mice, respectively ( P = 0.016). Ficoll clearance was increased in Cav-1-KO mice. In conclusion, the lack of caveolae in Cav-1-KO mice resulted in a marked increase in macromolecular transport. A two-pore analysis of the Ficoll clearance data revealed that the higher transport rate in Cav-1-KO mice was not compatible with the appearance of an alternative pathway for macromolecular transport. In contrast, the higher transperitoneal protein and Ficoll clearance is consistent with passive porous transport through an unperturbed two-pore system, presumably at an elevated capillary hydraulic pressure. Alternatively, the data may be explained by reductions in the selectivity of the endothelial glycocalyx, leading to an increased capillary hydraulic conductivity and large solute filtration.

The transport barrier in intraperitoneal therapy

The peritoneal cavity is important in clinical medicine because of its use as a portal of entry for drugs utilized in regional chemotherapy and as a means of dialysis for anephric patients. The barrier between the therapeutic solution in the cavity and the plasma does not correspond to the classic semipermeable membrane but instead is a complex structure of cells, extracellular matrix, and blood microvessels in the surrounding tissue. New research on the nature of the capillary barrier and on the orderly array of extracellular matrix molecules has provided insights into the physiological basis of osmosis and the alterations in transport that result from infusion of large volumes of fluid. The anatomic peritoneum is highly permeable to water, small solutes, and proteins and therefore is not a physical barrier. However, the cells of the mesothelium play an essential role in the immune response in the cavity and produce cytokines and chemokines in response to contact with noncompatible solutions. The process of inflammation, which depends on the interaction of mesothelial, interstitial, and endothelial cells, ultimately leads to angiogenesis and fibrosis and the functional alteration of the barrier. New animal models, such as the transgenic mouse, will accelerate the discovery of methods to preserve the functional peritoneal barrier.

Blood flow limitation in vivo of small solute transfer during peritoneal dialysis in rats

The aim of this study was to determine whether or to what extent transperitoneal flux of small solutes is reduced at low blood flows during peritoneal dialysis (PD) in rats. Peritoneal blood flow reductions were achieved by bleeding anesthetized (300 g) rats by 25% of their blood volume. After bleeding, a 2 h PD dwell was started using standard PD fluid. The permeability-surface area product (PS) for (51)Cr-EDTA and glucose were assessed, as well as the transperitoneal clearance (Cl) of albumin. Control animals were not bled. After bleeding, peritoneal blood flow declined from 145 +/- 17 perfusion units (PU) to 59 +/- 12 PU (P = 0.001). Concomitant with this reduction, PS for (51)Cr-EDTA fell from 0.284 +/- 0.01 ml/min to 0.216 +/- 0.01 ml/min (P = 0.006) and PS for glucose from 0.338 +/- 0.02 ml/min to 0.294 +/- 0.01 ml/min (P = 0.046). Mean arterial BP (MAP) dropped from 133 +/- 4 mmHg to 61 +/- 5 mmHg (P = 0.008). Cl of albumin fell largely in proportion to the estimated capillary hydrostatic pressure drop, i.e., from 6.1 +/- 0.7 microl/min to 2.3 +/- 0.3 microl/min (P = 0.001). The results demonstrate that the transperitoneal clearances of small solutes are blood flow limited during PD, when peritoneal perfusion is markedly reduced. The level of flow limitation was, however, much lower than expected and observed in other tissues. Albumin transport, which is not blood flow limited, was reduced largely in proportion to the calculated capillary hydrostatic pressure decrease.