Rafael Sánchez-Villanueva

Epithelial-to-mesenchymal transition of mesothelial cells is an early event during peritoneal dialysis and is associated with high peritoneal transport.

Ultrafiltration (UF) failure is a consequence of long-term peritoneal dialysis (PD). Fibrosis, angiogenesis, and vasculopathy are causes of this functional disorder after 3-8 years on PD. Epithelial-to-mesenchymal transition (EMT) of mesothelial cell (MC) is a key process leading to peritoneal fibrosis with functional deterioration. Our purpose was to study the peritoneal anatomical changes during the first months on PD, and to correlate them with peritoneal functional parameters. We studied 35 stable PD patients for up to 2 years on PD, with a mean age of 45.3+/-14.5 years. Seventy-four percent of patients presented loss of the mesothelial layer, 46% fibrosis (>150 microm) and 17% in situ evidence of EMT (submesothelial cytokeratin staining), which increased over time. All patients with EMT showed myofibroblasts, while only 36% of patients without EMT had myofibroblasts. The number of peritoneal vessels did not vary when we compared different times on PD. Vasculopathy was present in 17% of the samples. Functional studies were used to define the peritoneal transport status. Patients in the highest quartile of mass transfer area coefficient of creatinine (Cr-MTAC) (>11.8 ml min(-1)) showed significantly higher EMT prevalence (P=0.016) but similar number of peritoneal vessels. In the multivariate analysis, the highest quartile of Cr-MTAC remained as an independent factor predicting the presence of EMT (odds ratio 12.4; confidence interval: 1.6-92; P=0.013) after adjusting for fibrosis (P=0.018). We concluded that, during the first 2 PD years, EMT of MCs is a frequent morphological change in the peritoneal membrane. High solute transport status is associated with its presence but not with increased number of peritoneal vessels.

Alternative activation of macrophages in human peritoneum: implications for peritoneal fibrosis

BACKGROUND Depending on the cytokine microenvironment, macrophages (Mϕ) can adopt a proinflammatory (M1) or a profibrotic (M2) phenotype characterized by the expression of cell surface proteins such as CD206 and CD163 and soluble factors such as CC chemokine ligand 18 (CCL18). A key role for Mϕ in fibrosis has been observed in diverse organ settings. We studied the Mϕ population in a human model of peritoneal dialysis in which continuous stress due to dialysis fluids and recurrent peritonitis represent a risk for peritoneal membrane dysfunction reflected as ultrafiltration failure (UFF) and peritoneal fibrosis. METHODS We used flow cytometry and quantitative reverse transcription-polymerase chain reaction to analyse the phenotype of peritoneal effluent Mϕ and tested their ability to stimulate the proliferation of human fibroblasts. Mϕ from non-infected patients were compared with those from patients with active peritonitis. Cytokine production was evaluated by enzyme-linked immunosorbent assay (ELISA) in spent dialysates and cell culture supernatants. RESULTS CD206(+) and CD163(+) M2 were found within peritoneal effluents by flow cytometry analysis, with increased frequencies of CD163(+) cells during peritonitis (P = 0.003). TGFB1, MMP9 and CCL18 messenger RNA (mRNA) levels in peritoneal macrophages (pMϕ) were similar to those found in M2 cells differentiated in vitro. The ability of pMϕ to stimulate fibroblast proliferation correlated with CCL18 mRNA levels (r = 0.924, P = 0.016). CCL18 production by pMϕ was confirmed by immunostaining of cytospin samples and ELISA. Moreover, CCL18 effluent concentrations correlated with decreased peritoneal function, which was evaluated as dialysate to plasma ratio of creatinine (r = 0.724, P < 0.0001), and were significantly higher in patients with UFF (P = 0.0025) and in those who later developed sclerosing peritonitis (P = 0.024). CONCLUSIONS M2 may participate in human peritoneal fibrosis through the stimulation of fibroblast cell growth and CCL18 production as high concentrations of CCL18 are associated with functional deficiency and fibrosis of the peritoneal membrane.

High Stable Serum Adiponectin Levels Are Associated with a Better Outcome in Prevalent Dialysis Patients

Aims: Our aim was to evaluate the prognostic value of 2 measurements of serum adiponectin levels for all-cause mortality and cardiovascular (CV) mortality in uremic patients. Methods: We analyzed 184 patients (19–86 years) undergoing peritoneal dialysis (n = 86) or hemodialysis (n = 98). All patients had 2 measurements of serum adiponectin levels (at baseline and after 1 year). Relationships between adiponectin and mortality were studied by means of survival analysis and Cox regression analysis. Results: During a median follow-up time of 31.2 months, 67 patients (36.4%) died, 26 (14.1%) as a result of CV disease. Mean survival time for CV mortality in patients with 1-year adiponectin values in the upper tertile was significantly higher than that found in patients in the middle and lower tertiles. Hazard ratios (HR) for all-cause mortality per SD change were 0.70 (95% CI, 0.50–0.98; p < 0.05) for baseline adiponectin levels and 0.68 (0.49–0.95; p < 0.05) for mean baseline and 1-year adiponectin levels. Mean adiponectin levels were also negatively related with CV mortality [HR 0.43 (0.21–0.86); p < 0.05] and CV events [HR 0.74 (0.55–0.99); p < 0.05]. Conclusions: In this population of dialysis patients, adiponectin seems to behave as a CV protective factor. Patients with high mean adiponectin levels had a better survival rate.

Higher daily peritoneal protein clearance when initiating peritoneal dialysis is independently associated with peripheral arterial disease (PAD): A possible new marker of systemic endothelial dysfunction?

BACKGROUND Patients starting peritoneal dialysis (PD) with active cardiovascular disease (CVD) show higher protein and albumin levels in peritoneal effluent. Peripheral arterial disease (PAD) is increasingly recognized as an entity particularly associated with higher mortality. METHODS To explore whether higher daily peritoneal protein clearance (PrC) on starting PD is a cardiovascular risk marker, we have formulated the hypothesis that PAD, as an expression of the highest CVD grade, is specifically related to the amount of PrC. RESULTS The average of 24-h effluent peritoneal protein losses (PPL) was 6.88 +/- 3.31 g. The median of PrC was 94.43 ml/day and quartiles 1 and 4 were delimited by 56.25 and 114.18 ml/day, respectively. A significant positive correlation between PrC and peritoneal small solute transport was detected. Patients in the highest quintile of Cr-MTAC (>14.04 ml/min) demonstrated significantly greater PrC than the remainder. An inverse significant correlation with plasma albumin levels was also demonstrated (r = -0.52, P = 0.0001). Eighteen patients with PAD showed significantly higher PrC than patients with no PAD (130.62 +/- 74.89 versus 88.77 +/- 47.56 ml/day; P = 0.033). Other CVDs were not significantly associated with greater PrC. In the univariable logistic regression analysis, PAD was directly and significantly related to PrC, Charlsons index, gender, diabetes and age. Multivariable analysis confirmed that PAD was significantly related to PrC, independent of age (RR: 1.07, IC: 1.02-1.12, P = 0.006) and diabetes (RR: 11.29, IC: 2.9-42.60, P = 0.000). CONCLUSION Our study shows that daily peritoneal PrC on initiating PD is significantly and independently related to the presence of PAD. Peritoneal PrC appears to be a possible new marker of systemic endothelial dysfunction.

Reacciones de hipersensibilidad a membranas sintéticas de hemodiálisis

Undergoing a haemodialysis (HD) session poses a certain risk of hypersensitivity adverse reactions as large quantities of blood are in contact with various synthetic materials. Hypersensitivity reactions to ethylene oxide and non-biocompatible membranes, such as cuprophane, have been described in HD. Cases of hypersensitivity with biocompatible membranes, such as polysulfone, and even polysulfone-polyvinylpyrrolidone, have also been reported. In this article we describe six cases of mostly early-stage hypersensitivity reactions to HD occurring in our department, characterised by malaise, desaturation, bronchospasm and arterial hypotension, with good response to the session’s temporary suspension and with reappearance in subsequent sessions that used a synthetic dialyser. No hypersensitivity reactions reappeared in successive observations when the sessions were carried out using a cellulose membrane.

Análisis repetido de la resistencia insulínica estimada mediante índice HOMAIR en pacientes no diabéticos en diálisis peritoneal y su relación con la enfermedad cardiovascular y mortalidad

Terminal chronic renal failure patients show early insulin resistance (IR), characterised by alterations in the hydrocarbon metabolism and hyperinsulinaemia generally associated with dyslipidaemia and a proinflammatory condition. Cardiovascular disease (CVD) is the main cause of mortality in patients on dialysis. There is a strong association between IR, hyperinsulinism and CV disease. The objective of this study was to evaluate the effect of peritoneal dialysis (PD) on IR and its effects on the subsequent CVD morbidity and mortality in nondiabetic uraemic patients. It involved 69 nondiabetic patients on PD, 35 incident patients (≤ 3 months on PD) and 34 prevalent patients (>3 months on PD), with 2 estimated insulin resistance measurements 12 months apart using the insulin resistance index (HOMAIR). The mean HOMAIR value in incident patients was 1.8 ± 1.3 and 2.2 ± 2.1 at baseline situation and at 12 months respectively (not significant [NS]). In prevalent patients these values were 2.3 ± 1.3 and 2.5 ± 2.2 (NS). In our study, the mean glucose, insulin and IR concentrations measured by the HOMAIR and QUICKI indexes (the latter being a quantitative control for insulin sensitivity control) were similar at baseline situation and the following year, in both incident and prevalent patients. We did not find any significant differences in relation to CVD comorbidity, ischaemic heart disease, heart failure or cerebrovascular or peripheral comorbidity neither in the HOMAIR index or insulin levels. To conclude, nondiabetic patients on PD do not display a significant increase in HOMAIR levels and this remains the case over time when on dialysis. This, in turn, suggests that PD is not an IR risk factor. The fact that the IR indexes are not associated with CVD morbidity or mortality seems to suggest that this is a less significant factor in the field of PD.

An Increase of Plasma Advanced Oxidation Protein Products Levels Is Associated with Cardiovascular Risk in Incident Peritoneal Dialysis Patients: A Pilot Study.

Advanced oxidation protein products (AOPPs) are considered as markers and even mediators of the proinflammatory effect of oxidative stress in uremia. We hypothesized that an increase of oxidative stress associated with peritoneal dialysis (PD), estimated by the variation of plasma AOPPs over time, might be associated with cardiovascular (CV) risk and overall prognosis. In 48 PD patients, blood samples were collected on two occasions: the first one in the first six months after starting PD therapy and the second one, one year after. The plasma AOPPs level variation over the first year on PD was significantly associated with CV antecedents and also with CV prognosis. In those patients in whom the AOPPs levels increased more than 50% above the baseline value, a significant association with past and future CV disease was confirmed. These patients had 4.7 times greater risk of suffering later CV disease than those with a smaller increase, even after adjusting for previous CV history. Our data suggest that the increase of AOPPs plasma level over the first year on PD is conditioned by CV antecedents but also independently predicts CV prognosis. AOPPs plasma levels seem to represent the CV status of PD patients with sufficient sensitivity to identify those with a clearly sustained higher CV risk.

Evaluation of a polynephron dialysis membrane considering new aspects of biocompatibility.

Purpose The biocompatibility of dialyzers may influence the inflammatory state of hemodialysis patients. This study compares the effect of a high-flux polynephron membrane with other high-flux membranes, helixone and polyamide, on some inflammation biomarkers based on the analysis of circulating mononuclear cells (MC). Methods The study included 47 patients on hemodialysis with helixone and polyamide; 9 formed the control group, without changes in their dialyzers throughout the study, and 38 formed the intervention group, in which their dialyzers were replaced by polynephron. In both groups, blood samples were taken at the beginning of the study before and after hemodialysis session, and at the end of the study 4 months later. In each extraction, biochemical parameters were determined, and MC isolated using Ficoll gradient. Production of reactive oxygen species and the percentage of activated MC (CD14+CD16+) were measured by flow cytometry, and protein levels of heat-shock proteins (Hsp70/Hsp90) studied by Western blot. Results After 1 hemodialysis session with different membranes, no significant differences were observed in the different parameters considered. After 4 months of dialysis with polynephron, a significant reduction in the percentage of CD14+CD16+ and in the β2-microglobulin reduction ratio were found, with respect to helixone and polyamide, without changes in the other parameters analyzed. Conclusions The use of polynephron for 4 months reduces the percentage of CD14+CD16+ compared to helixone and polyamide, suggesting a better profile regarding activation of the inflammatory response. These findings could be explained by a better biocompatibility or an increased reduction of medium-sized toxic molecules.

Actinomyces peritonitis: removal of the peritoneal catheter unnecessary for resolution

Peritonitis is one of the most frequent complications in peritoneal dialysis (PD) patients. Most of them have a bacterial origin, especially gram-positive microorganisms. Actinomyces peritonitis is rare in PD patients, in spite of being part of the normal flora in the oral cavity, gastrointestinal and genital tracts [1]. Actinomyces is a filamentous gram-positive bacterium that lives in aerobic and anaerobic conditions [1]. It has a low virulence potential, usually causing opportunistic diseases. Factors that predispose towards abdominal Actinomyces infections include surgery, trauma, neoplasia or a perforated viscus. Penicillin is still the treatment of choice, but there are other effective antibiotics, such as erythromycin, clindamycin or tetracycline [2]. Actinomyces israelii is the major human pathogen of this species. We report a peritoneal infection due to Actinomyces neuii, a microorganism firstly described in 1985. In the present case, the removal of the catheter was not necessary for healing, unlike other cases published in the literature.

Mechanisms Involved in Hypersensitivity Reactions to Polysulfone Hemodialysis Membranes

Several cases of patients with anaphylactic or systemic hypersensitivity reactions to polysulfone (PS) hemodialysis (HD) membranes and tolerance to cellulose triacetate (CTA) membranes have recently been reported. To investigate the mechanisms involved in PS hypersensitivity, basophil, T cell, and complement activation were analyzed in acute-phase samples from two patients with systemic reactions to PS-based membranes. Basophil and T cell activation, as well as higher serum tryptase levels were detected in acute-phase samples compared with basal levels. Complement levels (C3 and C4) were decreased in acute-phase samples from PS-allergic patients to a higher extent than in samples from control donors taken at the same time points, indicating complement activation during the acute reactions. An experimental external circuit was established on pediatric membranes after rinsing with low or high priming volumes of saline solution, to analyze basophils, T cells, and complement activation in blood samples from 10 PS-allergic and 8 nonallergic HD patients upon contact with PS-based or CTA membranes. Predialysis and postdialysis samples were collected. Basophils from PS-allergic patients exhibited increased degranulation, and T cells showed significantly increased activation after contact with PS-based membranes primed with low volumes of saline. No activation was detected in leukocytes from nonallergic patients under the same experimental conditions. Membrane priming with high volumes of saline abrogated activation of basophils and T cells. However, basophils from allergic donors showed significantly higher responses to Fcεc stimulation after contact with PS membranes. Basophil degranulation and elevated serum tryptase levels in allergic patients during acute reactions support the systemic activation of mast cells and basophils during hypersensitivity reactions to PS-based membranes. A leachable component of the membranes might be responsible for cell activation in some patients.