Nebivolol, a ß1-adrenergic blocker, protects from peritoneal membrane damage induced during peritoneal dialysis.

UNLABELLED: Peritoneal dialysis (PD) is a form of renal replacement treatment, which employs the peritoneal membrane (PM) to eliminate toxins that cannot be removed by the kidney. The procedure itself, however, contributes to the loss of the PM ultrafiltration capacity (UFC), leading consequently to the technique malfunction. ß-blockers have been considered deleterious for PM due to their association with loss of UFC and induction of fibrosis. Herein we analyzed the effects of Nebivolol, a new generation of ß1-blocker, on PM alterations induced by PD fluids (PDF).In vitro: We found that mesothelial cells (MCs) express ß1-adrenergic receptor. MCs were treated with TGF-ß to induce mesothelial-to-mesenchymal transition (MMT) and co-treated with Nebivolol. Nebivolol reversed the TGF-ß effects, decreasing extracellular matrix synthesis, and improved the fibrinolytic capacity, decreasing plasminogen activator inhibitor-1 (PAI-1) and increasing tissue-type plasminogen activator (tPA) supernatant levels. Moreover, Nebivolol partially inhibited MMT and decreased vascular endothelial growth factor (VEGF) and IL-6 levels in supernatants.In vivo: Twenty-one C57BL/6 mice were divided into 3 groups. Control group carried a catheter without PDF infusion. Study group received intraperitoneally PDF and oral Nebivolol during 30 days. PDF group received PDF alone. Nebivolol maintained the UFC and reduced PM thickness, MMT and angiogenesis promoted by PDF. It also improved the fibrinolytic capacity in PD effluents decreasing PAI-1 and IL-8 and increased tPA levels. CONCLUSION: Nebivolol protects PM from PDF-induced damage, promoting anti-fibrotic, anti-angiogenic, anti-inflammatory and pro-fibrinolytic effects.

Reflexiones sobre la entrada y la retirada de diálisis / Thoughts on the start and withdrawal of dialysis

El aumento de las expectativas de vida y la disponibilidad de tratamientos proporcionados por la medicina actual han dado lugar a nuevas situaciones en las que se puede prolongar la supervivencia en condiciones de calidad de vida inaceptables. El tratamiento sustitutivo renal (TSR) para el tratamiento de la enfermedad renal crónica avanzada (ERCA) puede implicar el uso de técnicas agresivas, diseñadas para mejorar y prolongar la vida, a pacientes con elevada comorbilidad y expectativas de supervivencia muy limitadas a corto plazo. Con frecuencia, el inicio de TSR implica un empeoramiento de la calidad de vida de los pacientes y una importante sobrecarga familiar, con una limitada supervivencia. Los pacientes deben participar activamente en la toma de decisiones, pero para ello han de disponer de una información más completa sobre el pronóstico de su enfermedad y cómo va a influir el tratamiento en su calidad de vida. Los nefrólogos podremos contribuir mejor en la toma de decisiones perfeccionando las herramientas pronósticas y participando de forma colegiada con el paciente y su familia en la decisión final. Es necesario ofrecer a los pacientes que opten por el tratamiento conservador una adecuada asistencia mediante la implantación de equipos multidisciplinarios dentro de las unidades de ERCA (AU)

Increased life expectancy and the availability of treatments provided by modern medicine have given rise to a new situation in which survival may be prolonged without the patient having an acceptable quality of life. Renal replacement therapy (RRT) to treat End Stage Renal Disease (ESRD) may involve the use of aggressive techniques designed to improve and prolong the lives of patients with high comorbidity and very low short term survival expectancy. RRT often means lowering patients' quality of life, it is a significant burden on families and survival expectancy is low. Patients must actively participate in decision-making, but to do so, the information about the prognosis of their disease and how the treatment will affect their quality of life must be more comprehensive. As nephrologists, we will be able to contribute better to decision-making by improving prognostic tools and participating collectively with the patient and their family in the final decision. It is necessary to offer appropriate care to patients who opt for conservative treatment by implementing multidisciplinary teams within ESRD units (AU)

Thoughts on the start and withdrawal of dialysis.

Increased life expectancy and the availability of treatments provided by modern medicine have given rise to a new situation in which survival may be prolonged without the patient having an acceptable quality of life. Renal replacement therapy (RRT) to treat End Stage Renal Disease (ESRD) may involve the use of aggressive techniques designed to improve and prolong the lives of patients with high comorbidity and very low short term survival expectancy. RRT often means lowering patients’ quality of life, it is a significant burden on families and survival expectancy is low. Patients must actively participate in decision-making, but to do so, the information about the prognosis of their disease and how the treatment will affect their quality of life must be more comprehensive. As nephrologists, we will be able to contribute better to decision-making by improving prognostic tools and participating collectively with the patient and their family in the final decision. It is necessary to offer appropriate care to patients who opt for conservative treatment by implementing multidisciplinary teams within ESRD units.

Oral paricalcitol as antiproteinuric agent in chronic kidney disease.

BACKGROUND: Vitamin D has an important regulatory effect on the renin-angiotensin-aldosterone system, playing a central role in the regulation of proteinuria. We therefore studied the antiproteinuric effect of paricalcitol. METHODS: 36 patients with an estimated GFR of 30-90 mL/min/1.73 m² and proteinuria >400 mg/d with a stable dose of ACE inhibitor or ARB for at least 3 months were recruited. Patients received oral paricalcitol 1 µg/day for 12 months. Primary endpoint was decrease in proteinuria from baseline. Secondary endpoints were changes in creatinine, eGFR, serum levels of calcium, phosphorus, iPTH, 25(OH)vitD, C-Reactive Protein and blood presure. RESULTS: Mean proteinuria was 2806 mg/d and fell to 2199 mg/d at month 6 (p<.0001) and 1931.5 mg/d at month 12 (P<.0001). Patients with >3000 mg/d baseline proteinuria (n=12) saw smaller relative reductions in proteinuria (5956.9±2492.6 mg/d to 4220.4±2613 mg/d at 12 months) than patients with <3000 mg/d baseline proteinuria (1371±627.5 mg/d to 821.3±491.5mg/d at 12 months). There were no changes in BP, eGFR and CRP. We observed significant changes in serum levels of calcium, phosphorus, iPTH, 25(OH) vitamin D. CONCLUSION: Our study shows an important reduction in proteinuria with a low dose of oral paricalcitol in CKD, that is particularly robust with baseline proteinuria between 1-3 g/d.

Oral paricalcitol as antiproteinuric agent in chronic kidney disease

Background: Vitamin D has an important regulatory effect on the renin-angiotensin-aldosterone system, playing a central role in the regulation of proteinuria. We therefore studied the antiproteinuric effect of paricalcitol. Methods: 36 patients with an estimated GFR of 30-90mL/min/1.73m2 and proteinuria >400mg/d with a stable dose of ACE inhibitor or ARB for at least 3 months were recruited. Patients received oral paricalcitol 1µg/day for 12 months. Primary endpoint was decrease in proteinuria from baseline. Secondary endpoints were changes in creatinine, eGFR, serum levels of calcium, phosphorus, iPTH, 25(OH)vitD, C-Reactive Protein and blood presure. Results: Mean proteinuria was 2806mg/d and fell to 2199mg/d at month 6 (p<.0001) and 1931.5mg/d at month 12 (p<.0001). Patients with >3000mg/d baseline proteinuria (n=12) saw smaller relative reductions in proteinuria (5956.9±2492.6mg/d to 4220.4±2613mg/d at 12 months) than patients with <3000mg/d baseline proteinuria (1371±627.5 mg/d to 821.3±491.5mg/d at 12 months). There were no changes in BP, eGFR and CRP. We observed significant changes in serum levels of calcium, phosphorus, iPTH, 25(OH) vitamin D. Conclusion: Our study shows an important reduction in proteinuria with a low dose of oral paricalcitol in CKD, that is particularly robust with baseline proteinuria between 1-3g/d (AU)

Introducción: La vitamina D posee un efecto regulatorio del eje renina-angiotensina-aldosterona, jugando, por lo tanto, un papel importante en cuanto a proteinuria se refiere. Presentamos nuestra experiencia en el uso de paricalcitol como antiproteinúrico. Métodos: Incluimos 36 pacientes con un eGFR of 30-90 ml/min/1,73 m2 y proteinuria > 400 mg/d con dosis estables de inhibidores del SRAA durante 3 meses. Se le admistró durante 12 meses 1 µg/día de paricalcitol. Como objetivo primario estudiamos el descenso de proteinuria; como secundarios cambios en Cr, eFG, calcio, fósforo, iPTH, 25(OH)vitD, PCR y tension arterial. Resultados: La proteinuria media fue 2806 mg/d cayendo hasta 2199 mg/d en el mes 6 (p < 0,0001) y 1931,5 mg/d a los 12 meses (p < 0,0001). Aquellos con una proteinuria basal > 3000 mg/d (n=12) sufrieron una menor disminución (5956,9 ± 2492,6 mg/d a 4220,4 ± 2613 mg/d en mes 12) respecto a aquellos con una proteinuria < 3000 mg/d (1371 ± 627,5 mg/d a 821,3 ± 491,5 mg/d en mes 12). No se objetivaron cambios en tension arterial, eGFR y PCR. Los cambios en calcio, fósforo, iPTH y vitamina D 25(OH) fueron estadísticamente significativos. Conclusión: Nuestro estudio demuestra una reducción importante de proteinuria con dosis bajas de paricalcitol en pacientes con IRC, que es de particular importancia en aquellos con porteinuria basal entre 1-3 g/d (AU)

Tablas de ratio fósforo/proteína de alimentos para población española. Utilidad en la enfermedad renal crónica / Table showing dietary phosphorus/protein ratio for the Spanish population. Usefulness in chronic kidney disease

Antecedentes: Las guías K/DOQI recomiendan el uso del ratio fósforo/proteína de los alimentos para un buen control del fósforo de la dieta. Existe evidencia de tablas con el ratio fósforo/proteína. No existe hasta el momento una tabla de alimentos habituales en la población española con la estimación del ratio. Objetivos: Estimar el ratio fósforo/proteína de alimentos de uso general en la población española y establecer su utilidad en la selección de alimentos para los pacientes con enfermedad renal crónica. Método: Las tablas con el ratio fósforo/proteína se han elaborado a partir de dos fuentes de datos de composición de alimentos españolas. Se ha considerado la composición química por cada 100 g de alimento crudo. Las tablas no incluyen el fósforo de los aditivos. No se eliminaron los alimentos con ratio fósforo/proteína elevado para poder establecer una comparación entre los distintos alimentos de cada grupo. Resultados: Se encuentran comprendidos en las tablas. Conclusiones: La prescripción dietética de los pacientes con enfermedad renal crónica debería tener en consideración no solo el valor absoluto de fósforo del alimento en cuestión, sino también el ratio fósforo/proteína de cada alimento y el total de la dieta. Cuanto más «natural» sea la dieta, más fácil será que alcance un ratio fósforo/proteína aceptable y mayor probabilidad de ser menor de 16 mg/g, no aumentando la morbimortalidad. Resulta evidente la necesidad de establecer un programa educativo sobre fuentes de fósforo y nutrición en el que la tabla pueda ser una herramienta útil para el equipo multidisciplinar que atiende al enfermo renal (AU)

Background: The K/DOQI guidelines recommend the use of phosphorus/protein food ratios for proper control of dietary phosphorus. Evidence exists from tables with phosphorus to protein ratios for common foods. No such table exists for common foods consumed by the Spanish population with ratio estimations. Objectives: To estimate the phosphorus to protein ratio in foods commonly used by the Spanish population and to establish its usefulness in the selection of foods for patients with chronic kidney disease. Method: Tables with the phosphorus to protein ratio were prepared from two data sources concerning Spanish food composition. We evaluated chemical composition per 100g of raw food. The tables do not include phosphorus additives. No foods with high ratio of phosphorus to protein were eliminated in order to allow comparisons between different foods from each group. Results: Shown in the tables. Conclusions: The dietary prescription for patients with chronic kidney disease should take into consideration not only the absolute phosphorus value of food consumed, but also the phosphorus to protein ratio of each food and the total amount of phosphorus in the diet. The more "natural" a diet is, the more likely that the patient will reach an acceptable phosphorus to protein ratio of less than 16mg/g, which does not increase mortality. There is clearly a need for an educational program on nutrition and phosphorus sources in which food ratio tables could be a useful tool for the multidisciplinary teams caring for renal patients (AU)

Table showing dietary phosphorus/protein ratio for the Spanish population. Usefulness in chronic kidney disease.

BACKGROUND: The K/DOQI guidelines recommend the use of phosphorus/protein food ratios for proper control of dietary phosphorus. Evidence exists from tables with phosphorus to protein ratios for common foods. No such table exists for common foods consumed by the Spanish population with ratio estimations. OBJECTIVES: To estimate the phosphorus to protein ratio in foods commonly used by the Spanish population and to establish its usefulness in the selection of foods for patients with chronic kidney disease. METHOD: Tables with the phosphorus to protein ratio were prepared from two data sources concerning Spanish food composition. We evaluated chemical composition per 100g of raw food. The tables do not include phosphorus additives. No foods with high ratio of phosphorus to protein were eliminated in order to allow comparisons between different foods from each group. RESULTS: Shown in the tables. CONCLUSIONS: The dietary prescription for patients with chronic kidney disease should take into consideration not only the absolute phosphorus value of food consumed, but also the phosphorus to protein ratio of each food and the total amount of phosphorus in the diet. The more "natural" a diet is, the more likely that the patient will reach an acceptable phosphorus to protein ratio of less than 16mg/g, which does not increase mortality. There is clearly a need for an educational program on nutrition and phosphorus sources in which food ratio tables could be a useful tool for the multidisciplinary teams caring for renal patients.

Costes comparativos entre los conciertos de hemodiálisis y diálisis peritoneal / Cost comparison between haemodialysis and peritoneal dialysis outsourcing agreements

No disponible

PPAR-γ agonist rosiglitazone protects peritoneal membrane from dialysis fluid-induced damage.

Exposure to non-physiological solutions during peritoneal dialysis (PD) produces structural alterations to the peritoneal membrane and ultrafiltration dysfunction. The high concentration of glucose and glucose degradation products in standard PD fluids induce a local diabetic environment, which leads to the formation of advanced glycation end products (AGEs) that have an important role in peritoneal membrane deterioration. Peroxisome proliferator-activated receptor γ (PPAR-γ) agonists are used to treat type II diabetes and they have beneficial effects on inflammation, fibrosis, and angiogenesis. Hence, we evaluated the efficacy of the PPAR-γ agonist rosiglitazone (RSG) in ameliorating peritoneal membrane damage in a mouse PD model, and we analyzed the mechanisms underlying the protection offered by RSG. Exposure of the peritoneum to PD fluid resulted in AGEs accumulation, an inflammatory response, the loss of mesothelial cell monolayer and invasion of the compact zone by mesothelial cells, fibrosis, angiogenesis, and functional impairment of the peritoneum. Administration of RSG diminished the accumulation of AGEs, preserved the mesothelial monolayer, decreased the number of invading mesothelial cells, reduced fibrosis and angiogenesis, and improved peritoneal function. Interestingly, instead of reducing the leukocyte recruitment, RSG administration enhanced this process and specifically, the recruitment of CD3+ lymphocytes. Furthermore, RSG treatment augmented the levels of the anti-inflammatory cytokine interleukin (IL)-10 and increased the recruitment of CD4+ CD25+ FoxP3+ cells, suggesting that regulatory T cells mediated the protection of the peritoneal membrane. In cell-culture experiments, RSG did not prevent or reverse the mesothelial to mesenchymal transition, although it decreased mesothelial cells apoptosis. Accordingly, RSG appears to produce pleiotropic protective effects on the peritoneal membrane by reducing the accumulation of AGEs and inflammation, and by preserving the mesothelial cells monolayer, highlighting the potential of PPAR-γ activation to ameliorate peritoneal deterioration in PD patients.

Epithelial to mesenchymal transition and peritoneal membrane failure in peritoneal dialysis patients: pathologic significance and potential therapeutic interventions.

Peritoneal dialysis (PD) is a form of renal replacement and is based on the use of the peritoneum as a semipermeable membrane across which ultrafiltration and diffusion take place. Nevertheless, continuous exposure to bioincompatible PD solutions and episodes of peritonitis or hemoperitoneum cause acute and chronic inflammation and injury to the peritoneal membrane, which progressively undergoes fibrosis and angiogenesis and, ultimately, ultrafiltration failure. The pathophysiologic mechanisms that are involved in peritoneal functional impairment have remained elusive. Resident fibroblasts and infiltrating inflammatory cells have been considered the main entities that are responsible for structural and functional alterations of the peritoneum. Recent findings, however, demonstrated that new fibroblastic cells may arise from local conversion of mesothelial cells (MC) by epithelial-to-mesenchymal transition (EMT) during the inflammatory and repair responses that are induced by PD and pointed to MC as protagonists of peritoneal membrane deterioration. Submesothelial myofibroblasts, which participate in inflammatory responses, extracellular matrix accumulation, and angiogenesis, can originate from activated resident fibroblasts and from MC through EMT. This heterogeneous origin of myofibroblasts reveals new pathogenic mechanisms and offers novel therapeutic possibilities. This article provides a comprehensive review of recent advances on understanding the mechanisms that are implicated in peritoneal structural alterations, which have allowed the identification of the EMT of MC as a potential therapeutic target of membrane failure.

Inherent high peritoneal transport and ultrafiltration deficiency: their mid-term clinical relevance.

BACKGROUND: High peritoneal transport has been associated with poorer outcome in peritoneal dialysis (PD) patients, but not necessarily because of PD-dependent conditions. Our primary objective was to analyse the influences of baseline peritoneal small solute transport and ultrafiltration (UF) capacity on patient and technique survival, after adjusting for comorbid conditions. A secondary objective was to determine whether high transport was associated with basal comorbidity. METHODS: In this prospective observational patient/technique survival study, we followed 410 patients who started PD. At the baseline, we collected data to define comorbidities, tally the Charlson index, determine the baseline mass transfer area coefficients (MTAC) of urea and creatinine, net UF, plasma albumin and residual renal function (RRF). No data other than the information on patient and technique survival were recorded after baseline. RESULTS: The mean follow-up was 33 +/- 28 months. Dropouts during the study were due to renal transplantation in 140 cases, death in 142 cases and transfer to haemodialysis (HD) in 77 cases. Patients with inherent UF deficiency, high transport rate or both were not significantly different in the survival analysis from the rest. In the Cox hazards analysis, only age, Charlson index and a lower RRF were the significant mortality risk factors. None of the baseline parameters studied was a predictor of technique failure. High transporter patients had lower plasma albumin and UF capacity, comorbidity and more frequent liver diseases than the rest. Moderate to severe liver disease (n = 14) was significantly associated with the inherent high transport status, but was never accompanied by UF failure (UFF). UFF patients showed higher RRF, creatinine-MTAC and age. CONCLUSIONS: Neither the high transport nor the inherent UFF status has any influence on patient and technique survival. The inherent high small solute transport status is associated with hypoalbuminaemia and a greater comorbidity index. The Charlson index, age and lower RRF are the only independent predictors of mortality. Technique dropout is not predicted by any of the variables studied at the baseline.

Mast cell quantification in normal peritoneum and during peritoneal dialysis treatment.

CONTEXT: Mast cells (MCs) have been implicated in fibrogenesis, angiogenesis, and immunity against bacteria. These 3 mechanisms participate in the peritoneal pathology secondary to peritoneal dialysis (PD) treatment. Despite their potential relevance to PD-related pathology, few studies have focused on MCs. OBJECTIVE: To evaluate possible variations in the number of MCs during PD treatment. DESIGN: A quantitative study of tissue MCs in normal and pathologic peritoneum. Parietal peritoneal biopsies were collected from 4 groups: (1) normal controls (n = 9), (2) uremic non-PD patients (n = 16), (3) uremic patients on PD (n = 26), and (4) non-renal patients with inguinal hernia (n = 20). MCs were evaluated using immunohistochemistry for the detection of tryptase. The total number of cross sections of vessels per peritoneal field was examined in 22 of the 26 peritoneal biopsies of PD patients. RESULTS: PD tissue samples showed fibrosis, mesothelial cell loss, and variable hyalinizing vasculopathy. The number of MCs was similar in normal controls and non-PD uremic patients (mean +/- SE: 7.13 +/- 0.67 and 7.74 +/- 0.74 MCs/mm2, respectively). Peritoneal dialysis patients showed a reduction (4 +/- 0.38 MCs/mm2, P < .001), whereas hernia sac samples showed an increase (10.59 +/- 3.48 MCs/mm2). MC reduction showed no correlation with time on dialysis, fibrosis, number of vessels, or previous episodes of peritonitis. CONCLUSIONS: The peritoneum of patients receiving PD treatment shows a reduction of MCs. Despite such a reduction, fibrosis takes place, suggesting that MCs do not play a critical role in fibrosis genesis. Mast cell loss may be a contributory factor to peritonitis episodes in PD patients.

Epithelial-to-mesenchymal transition of the mesothelial cell--its role in the response of the peritoneum to dialysis.

Peritoneal membrane fibrosis, ranging from mild inflammation to severe sclerosing peritonitis, is one of the complications of peritoneal dialysis (PD). In parallel with fibrosis, the peritoneum shows a progressive increase of capillaries and vasculopathy, involved in increased small solute transport across the membrane and ultrafiltration failure. Glucose and glucose degradation products from PD solutions are responsible of stimulating transforming growth factor-beta (TGF-beta) and vascular endothelial growth factor (VEGF) production by mesothelial cells (MCs). TGF-beta is a potent pro-fibrotic factor and inducer of epithelial-to-mesenchymal transition (EMT) of the MC. Local production of VEGF by transitional MC appears to play a central role in the processes leading to peritoneal angiogenesis. This review addresses the mechanism involved in peritoneal structural alteration by dialysis and points to the EMT of MC as the initiating mechanism of peritoneal injury. Information from multiple origins about TGF-beta and VEGF is integrated into EMT process in a comprehensive manner. Regulation and new targets for inhibition of EMT or its deleterious effects are discussed.

Ex vivo analysis of dialysis effluent-derived mesothelial cells as an approach to unveiling the mechanism of peritoneal membrane failure.

During peritoneal dialysis (PD), the peritoneum is exposed to bioincompatible dialysis fluids, which causes progressive fibrosis and angiogenesis and, ultimately, ultrafiltration failure. In addition, repeated episodes of peritonitis or hemoperitoneum may accelerate all these processes. Fibrosis has been classically considered the main cause of peritoneal membrane functional decline. However, in parallel with fibrosis, the peritoneum also displays increases in capillary number (angiogenesis) and vasculopathy in response to PD. Nowadays, there is emerging evidence pointing to peritoneal microvasculature as the main factor responsible for increased solute transport and ultrafiltration failure. However, the pathophysiologic mechanism(s) involved in starting and maintaining peritoneal fibrosis and angiogenesis remain(s) elusive. Peritoneal stromal fibroblasts have been considered (for many years) the cell type mainly involved in structural and functional alterations of the peritoneum; whereas mesothelial cells have been considered mere victims of peritoneal injury caused by PD. Recently, ex vivo cultures of effluent-derived mesothelial cells, in conjunction with immunohistochemical analysis of peritoneal biopsies from PD patients, have identified mesothelial cells as culprits, at least in part, in peritoneal membrane deterioration. This review discusses recent findings that suggest new peritoneal myofibroblastic cells may arise from local conversion of mesothelial cells by epithelial-to-mesenchymal transition during the repair responses that take place in PD. The transdifferentiated mesothelial cells may retain a permanent mesenchymal state, as long as initiating stimuli persist, and contribute to PD-induced fibrosis and angiogenesis, and hence to membrane failure. Future therapeutic interventions could be designated in order to prevent or reverse epithelial-to-mesenchymal transition of mesothelial cells, or its pernicious effects.

Mesenchymal conversion of mesothelial cells as a mechanism responsible for high solute transport rate in peritoneal dialysis: role of vascular endothelial growth factor.

BACKGROUND: During peritoneal dialysis (PD), the peritoneum is exposed to bioincompatible dialysis fluids that cause epithelial-to-mesenchymal transition of mesothelial cells, fibrosis, and angiogenesis. Ultrafiltration failure is associated with high transport rates and increased vascular surface, indicating the implication of vascular endothelial growth factor (VEGF). Sources of VEGF in vivo in PD patients remain unclear. We analyzed the correlation between epithelial-to-mesenchymal transition of mesothelial cells and both VEGF level and peritoneal functional decline. METHODS: Effluent mesothelial cells were isolated from 37 PD patients and analyzed for mesenchymal conversion. Mass transfer coefficient for creatinine (Cr-MTC) was used to evaluate peritoneal function. VEGF concentration was measured by using standard procedures. Peritoneal biopsy specimens from 12 PD patients and 6 controls were analyzed immunohistochemically for VEGF and cytokeratin expression. RESULTS: Nonepithelioid mesothelial cells from effluent produced a greater amount of VEGF ex vivo than epithelial-like mesothelial cells (P < 0.001). Patients whose drainage contained nonepithelioid mesothelial cells had greater serum VEGF levels than those with epithelial-like mesothelial cells in their effluent (P < 0.01). VEGF production ex vivo by effluent mesothelial cells correlated with serum VEGF level (r = 0.6; P < 0.01). In addition, Cr-MTC correlated with VEGF levels in culture (r = 0.8; P < 0.001) and serum (r = 0.35; P < 0.05). Cr-MTC also was associated with mesothelial cell phenotype. VEGF expression in stromal cells, retaining mesothelial markers, was observed in peritoneal biopsy specimens from high-transporter patients. CONCLUSION: These results suggest that mesothelial cells that have undergone epithelial-to-mesenchymal transition are the main source of VEGF in PD patients and therefore may be responsible for a high peritoneal transport rate.

Pathogenic significance of hypertrophic mesothelial cells in peritoneal effluent and ex vivo culture.

The presence of hypertrophic mesothelial cells (HMCs) in peritoneal effluent (PE) has been considered a possible marker for peritoneal sclerosis. We conducted the present study to evaluate if the presence of HMCs in PE or in culture was related to peritoneal function alterations or to the development of sclerosing peritonitis. We prospectively studied 32 new peritoneal dialysis (PD)patients every 4 months, determining the presence of HMCs in culture (completing 129 studies in total). We isolated mesothelial cells from nocturnal PE and cultured them ex vivo in T-25 flasks. Cell morphology was estimated using the May-Grünwald/Giemsa method. We also examined the histories of a large patient group to determine HMCs directly in PE, and we evaluated 4 of those patients (6%) who showed persistent HMCs. In 10 of 32 prospectively studied patients, we found HMCs during the culture phase. The cells appeared in the first evaluation in 4 patients and in subsequent cultures in the remaining 6 patients. Ultrafiltration (UF) and solute transport capacity in the 10 patients were similar to those of patients who did not show HMCs. Demographic parameters were not different between the two groups. None of the prospectively studied patients showed any clinical or peritoneal functional abnormality during the study. Cultures performed after the observation of HMCs showed very poor growth capacity. The evolution of the 4 patients in the historic group occurred as follows: We 1 patient transferred to hemodialysis 2 years after the observation of HMCs. 1 patient died of an unrelated cause after 1 year on PD. 1 patient received a successful kidney graft 5 years after the observation of HMCs. 1 patient developed type I UF failure 10 years after the first observation.

Ghrelin plasma levels and appetite in peritoneal dialysis patients.

Anorexia-associated malnutrition is a severe complication that increases mortality in peritoneal dialysis (PD) patients. Ghrelin is a recently-discovered orexigenic hormone with actions in brain and stomach. We analyzed, in 42 PD patients, the possible relationship between ghrelin and appetite regulation with regard to other orexigens [neuropeptide Y (NPY), NO3] and anorexigens [cholecystokinin (CCK), leptin, glucose-dependent insulinotropic peptide (GIP), tumor necrosis factor alpha (TNFalpha)]. All orexigens and anorexigens were determined in plasma. Eating motivation was evaluated using a visual analog scale (VAS). The patients were divided into three groups: those with anorexia (n = 12), those with obesity associated with high intake (n = 12), and those with no eating behavior disorders (n = 18). A control group of 10 healthy volunteers was also evaluated. Mean plasma levels of ghrelin were high (3618.6 +/- 1533 mg/mL), with 36 patients showing values above the normal range (< 2600 mg/mL). Patients with anorexia had lower ghrelin and NPY levels and higher peptide-C, CCK, interleukin-1 (IL-1), TNFalpha, and GIP levels than did the other patients. Patients with anorexia also had an early satiety score and low desire and pleasure in eating on the VAS and diet survey. We observed significant positive linear correlations between ghrelin and albumin (r = 0.43, p < 0.05), prealbumin (r = 0.51, p < 0.05), transferrin (r = 0.4, p < 0.05), growth hormone (r = 0.66, p < 0.01), NO3 (r = 0.36, p < 0.05), and eating motivation (VAS). At the same time, negative relationships were observed between blood ghrelin and GIP (r = -0.42, p < 0.05), insulin (r = -0.4, p < 0.05), leptin (r = -0.45, p < 0.05), and creatinine clearance [r = -0.33, p = 0.08 (nonsignificant)]. Ghrelin levels were not related to Kt/V or to levels of CCK and cytokines. Ghrelin plasma levels are elevated in PD patients. Uremic patients with anorexia show relatively lower ghrelin plasma levels than the levels seen in obese patients or in patients with normal appetite. The role of ghrelin in appetite modulation is altered in uremic PD patients, and that alteration is possibly associated with disorders in insulin and growth hormone metabolism.

Immunohistochemical characterization of fibroblast subpopulations in normal peritoneal tissue and in peritoneal dialysis-induced fibrosis.

Peritoneal fibrosis is one of the most common morphological changes observed in continuous ambulatory peritoneal dialysis (CAPD) patients. Both resident fibroblasts and new fibroblast-like cells derived from the mesothelium by epithelial-to-mesenchymal transition are the main cells involved fibrogenesis. In order to establish markers of peritoneal impairment and pathogenic clues to explain the fibrogenic process, we conducted an immunohistochemical study focused on peritoneal fibroblasts. Parietal peritoneal biopsies were collected from four patient groups: normal controls ( n = 15), non-CAPD uremic patients ( n = 17), uremic patients on CAPD ( n = 27) and non-renal patients with inguinal hernia ( n = 12). To study myofibroblastic conversion of mesothelial cells, alpha-smooth muscle actin (SMA), desmin, cytokeratins and E-cadherin were analyzed. The expression of CD34 by fibroblasts was also analyzed. Fibroblasts from controls and non-CAPD uremic patients showed expression of CD34, but no myofibroblastic or mesothelial markers. The opposite pattern was present during CAPD-related fibrosis. Expression of cytokeratins and E-cadherin by fibroblast-like cells and alpha-SMA by mesothelial and stromal cells supports that mesothelial-to-myofibroblast transition occurs during CAPD. Loss of CD34 expression correlated with the degree of peritoneal fibrosis. The immunophenotype of fibroblasts varies during the progression of fibrosis. Myofibroblasts seem to derive from both activation of resident fibroblasts and local conversion of mesothelial cells.