Role of endothelial hyaluronan in peritoneal membrane transport and disease conditions during peritoneal dialysis

Peritoneal membrane dysfunction in peritoneal dialysis (PD) is primarily attributed to angiogenesis; however, the integrity of vascular endothelial cells can affect peritoneal permeability. Hyaluronan, a component of the endothelial glycocalyx, is reportedly involved in preventing proteinuria in the normal glomerulus. One hypothesis suggests that development of encapsulating peritoneal sclerosis (EPS) is triggered by protein leakage due to vascular endothelial injury. We therefore investigated the effect of hyaluronan in the glycocalyx on peritoneal permeability and disease conditions. After hyaluronidase-mediated degradation of hyaluronan on the endothelial cells of mice, macromolecules, including albumin and β2 microglobulin, leaked into the dialysate. However, peritoneal transport of small solute molecules was not affected. Pathologically, hyaluronan expression was diminished; however, expression of vascular endothelial cadherin and heparan sulfate, a core protein of the glycocalyx, was preserved. Hyaluronan expression on endothelial cells was studied using 254 human peritoneal membrane samples. Hyaluronan expression decreased in patients undergoing long-term PD treatment and EPS patients treated with conventional solutions. Furthermore, the extent of hyaluronan loss correlated with the severity of vasculopathy. Hyaluronan on endothelial cells is involved in the peritoneal transport of macromolecules. Treatment strategies that preserve hyaluronan in the glycocalyx could prevent the leakage of macromolecules and subsequent related complications.

Neoadjuvant Chemotherapy plus Interval Cytoreductive Surgery with or without Hyperthermic Intraperitoneal Chemotherapy (NIHIPEC) in the Treatment of Advanced Ovarian Cancer: A Multicentric Propensity Score Study

INTRODUCTION

Epithelial ovarian cancer (EOC) is primarily confined to the peritoneal cavity. When primary complete surgery is not possible, neoadjuvant chemotherapy (NACT) is provided; however, the peritoneum-plasma barrier hinders the drug effect. The intraperitoneal administration of chemotherapy could eliminate residual microscopic peritoneal tumor cells and increase this effect by hyperthermia. Intraperitoneal hyperthermic chemotherapy (HIPEC) after interval cytoreductive surgery could improve outcomes in terms of disease-free survival (DFS) and overall survival (OS).

MATERIALS AND METHODS

A multicenter, retrospective observational study of advanced EOC patients who underwent interval cytoreductive surgery alone (CRSnoH) or interval cytoreductive surgery plus HIPEC (CRSH) was carried out in Spain between 07/2012 and 12/2021. A total of 515 patients were selected. Progression-free survival (PFS) and OS analyses were performed. The series of patients who underwent CRSH or CRSnoH was balanced regarding the risk factors using a statistical analysis technique called propensity score matching.

RESULTS

A total of 170 patients were included in each subgroup. The complete surgery rate was similar in both groups (79.4% vs. 84.7%). The median PFS times were 16 and 13 months in the CRSH and CRSnoH groups, respectively (Hazard ratio (HR) 0.74; 95% CI, 0.58-0.94; p = 0.031). The median OS times were 56 and 50 months in the CRSH and CRSnoH groups, respectively (HR, 0.88; 95% CI, 0.64-1.20; p = 0.44). There was no increase in complications in the CRSH group.

CONCLUSION

The addition of HIPEC after interval cytoreductive surgery is safe and increases DFS in advanced EOC patients.

Measuring peritoneal absorption with the prolonged peritoneal equilibration test from 4 to 8 hours using various glucose concentrations

BACKGROUND

Peritoneal fluid flows such as small-pore ultrafiltration and free water transport can now be calculated by means of the modified peritoneal equilibration test (PET). To calculate peritoneal fluid absorption, volume markers have been used, but that method is not easily applicable in clinical practice. Alternatively, absorption can be estimated using the personal dialysis capacity test. However, a method of measuring overall peritoneal absorption together with the PET is lacking. The aim of the present study was to assess whether overall peritoneal absorption was different when measured from the 4th to 8th hour in a prolonged PET using three different glucose solutions.

METHODS

The study enrolled 32 stable peritoneal dialysis (PD) patients from a tertiary university hospital, who underwent three 8-hour prolonged PETs with 1.36%, 2.27%, and 3.86% glucose solution. The PETs were performed in random order over a period of less than 1 month. During the prolonged PET, the peritoneal volume was emptied and reinfused at 60 and 240 minutes and drained at 480 minutes. Peritoneal absorption was calculated as the volume difference between the 4th and the 8th hour.

RESULTS

The dialysate-to-plasma ratio (D/P) of urea, the D/P creatinine, and the mass transfer area coefficient (MTC) of creatinine at 240 minutes were not significantly different with the three glucose solutions. The end-to-initial (D/D0) glucose, MTC urea, and MTC glucose were significantly different. All water transport parameters were significantly different, except for the 4- to 8-hour absorption volumes and rates. The peritoneal absorption rates were, for 1.36% solution, 1.03 ± 0.58 mL/min [95% confidence interval (CI): 0.83 to 1.24 mL/min]; for 2.27% solution, 0.86 ± 0.71 mL/min (95% CI: 0.61 to 1.11 mL/min); and for 3.86% solution, 1.05 ± 0.78 mL/min (95% CI: 0.77 to 1.33 mL/min). Peritoneal absorption volumes and rates from the 4th to the 8th hour showed good correlations for the various solutions.

CONCLUSIONS

Using any glucose solution, the prolonged PET with voiding and reinfusion at the 4th hour could be a practical method for calculating overall peritoneal absorption from the 4th to the 8th hour in PD patients.

Non-immune hydrops fetalis: a short review of etiology and pathophysiology

Hydrops fetalis is an excessive accumulation of fetal fluid. Hydrops is traditionally classified into either immune or non-immune hydrops (NIHF), but in practice, nowadays in the Western world >90% of hydrops is of non-immune origin. The basis of the disorder is an imbalance in the regulation of fetal fluid movement between the vascular and interstitial space. We previously suggested a diagnostic flow-chart for NIHF. In this short review we describe the main mechanisms leading to NIHF.

The impact of dialysis solution biocompatibility on ultrafiltration and on free water transport in rats

This study compares different peritoneal dialysis fluids (PDF) in rats over a short contact time. For greater accuracy, net ultrafiltration (UF) and peritoneal transport indices, mass transfer area coefficient (MTAC) were scaled for the in vivo peritoneal surface area recruited (ivPSA) measured by microcomputerized tomography. Wistar rats underwent nephrectomy (5/6ths), were randomized into two groups and given 1.5% glucose PDF, either conventional acidic lactate (n = 14) or pH neutral bicarbonate (BicaVera) (n = 13); MTAC and UF were measured using a 90-min peritoneal equilibrium test (PET), fill volume (IPV) of 10 ml/100 g; small pore fluid transport was determined from sodium balance and used to calculate free water transport (FWT). Each ivPSA value was significantly correlated with the actual IPV, which varied from one rat to another. At 90 min of contact, there was no difference in recruited ivPSA in relation to PDFs. There was a difference (p < 0.01) in net UF/ivPSA 0.45 vs. 1.41 cm(2)/ml for bicarbonate versus lactate, as there was in the proportion of FWT with bicarbonate (42 ± 5% of net UF) compared to lactate (29 ± 4% of net UF). Net UF for individual values of ivPSA differs between conventional PDF and more biocompatible solutions, such as bicarbonate PDF. This observed change in UF cannot be fully explained by differences in glucose transport. The changes in FWT may be explained by the impact of the PDF biocompatibility on aquaporin function.

Postmortem image analysis of sheep cortical leptomeningeal space and vasculature: theoretical implications on brain surface dialysis

The vascular surface distribution of the subarachnoid space has not been studied extensively. The aim of our study was to develop a method of computer-assisted estimation of the distribution of the vascular network in the cortical leptomeninges and subarachnoid space and model it to aid the study of the physiology of brain surface dialysis. Nine sheets of leptomeningeal tissue were obtained from adult sheep. Fourteen image sample areas of 4 cm² each were acquired and processed with ImageJ. The vascular and nonvascular areas of the cortical subarachnoid space were identified using a "projected surface" approach. The modeling equations were used to predict the behavior of brain surface dialysis processes. The mean surface area of identified subarachnoid vessels was 0.354 ± 0.02 cm² per 1 cm² of tissue. The mean meningeal area with unidentified vessels was 0.646 ± 0.02 cm²/1 cm², and the difference between these surfaces was significant (p < 0.0001). The modeling equations used predict that modifying the vessel diameter of the subarachnoid space could alter the efficiency of brain surface dialysis. The computer-assisted modeling of the vascular surface of the cortical subarachnoid space may be a useful tool in depicting its morphology and assessing the physiology during brain surface dialysis.