Increased survival of mesothelial cells from the peritoneum in peritoneal dialysis fluid

Peritonitis remains the most important factor in patient morbidity and technical failure associated with continuous ambulatory peritoneal dialysis (CAPD). In vitro examination of bacterial infection of cultured human peritoneal mesothelial cells (HPMC) is an attractive approach to the study of peritonitis in CAPD, yet there are few reports on this subject. Previous studies have shown two limitations: (i) cell cultures of HPMC lasted for days only when incubated in culture medium and (ii) short-term studies of <30 min were done in HPMC when incubated with peritoneal dialysis fluid (PDF). Human peritoneal mesothelial cells, maintained in a conventional single chamber culture system with PDF alone, were unable to survive more than 40 min. The present study was designed to prolong the viability of HPMC cultured in PDF, with the object of using cells under different conditions, such as that of simulating CAPD. HPMC were cultured using plastic microtiter plates, where they were grown to confluence and growth was arrested. PDF containing different concentrations of NaHCO3and human serum albumin was added. Cell viability after exposure for up to 24 h was measured by trypan blue, Cell Death Detection ELISA and Annex-V flow cytometry. The data confirmed the 'toxic' effect of PDF, with cell viability being <40% after 2 h incubation in 4.25% glucose in PDF. However, the survival time of HPMC increased significantly in 4.25% glucose PDF at a physiological pH and even further after the addition of human albumin. These experimental conditions simulating CAPD may allow future in vitro studies of mesothelial physiology and peritonitis related to CAPD treatment.     

Expression of matrix metalloproteinases-2 and -9 by cells isolated from the peritoneal fluid of women with ovarian carcinoma

OBJECTIVE: To investigate the level of expression of matrix metalloproteinases (MMP)-2 and -9 by cells isolated from the peritoneal fluid of women with ovarian carcinoma. STUDY DESIGN: Tumor tissue specimens and cells isolated from peritoneal fluid from 20 patients with epithelial ovarian carcinoma were examined for MMP-2 and -9 expression using immunostaining. Six benign peritoneal effusions containing mesothelial cells were also included in the study. RESULTS: Expression of both MMP-2 and -9 was noted in cancer cells in peritoneal fluid of all cases studied. Peritoneal fluid cancer cells showed increased expression of both MMP-2 and -9 relative to mesothelial cell expression of these MMPs. Positive immunoreactivity of these MMPs in primary tumor tissues was confirmed by immunohistochemistry. CONCLUSION: Our findings suggest that both MMP-2 and -9 are frequently overexpressed in ovarian cancer cells disseminated in the peritoneal cavity and that determination of cellular MMP-2 and -9 expression could be useful in distinguishing cancer cells from mesothelial cells in peritoneal fluid cytologic specimens from women with ovarian epithelial carcinoma.     

The Spectrum of Podoplanin Expression in Encapsulating Peritoneal Sclerosis

Encapsulating peritoneal sclerosis (EPS) is a life threatening complication of peritoneal dialysis (PD). Podoplanin is a glycoprotein expressed by mesothelial cells, lymphatic endothelial cells, and myofibroblasts in peritoneal biopsies from patients with EPS. To evaluate podoplanin as a marker of EPS we measured podoplanin mRNA and described the morphological patterns of podoplanin-positive cells in EPS. Included were 20 peritoneal biopsies from patients with the diagnosis of EPS (n = 5), patients on PD without signs of EPS (n = 5), and control patients (uremic patients not on PD, n = 5, non-uremic patients n = 5). EPS patient biopsies revealed significantly elevated levels of podoplanin mRNA (p<0.05). In 24 peritoneal biopsies from patients with EPS, podoplanin and smooth muscle actin (SMA) were localized by immunohistochemistry. Four patterns of podoplanin distribution were distinguishable. The most common pattern (8 of 24) consisted of organized, longitudinal layers of podoplanin-positive cells and vessels in the fibrotic zone (“organized” pattern). 7 of 24 biopsies demonstrated a diffuse distribution of podoplanin-positive cells, accompanied by occasional, dense clusters of podoplanin-positive cells. Five biopsies exhibited a mixed pattern, with some diffuse areas and some organized areas ("mixed"). These contained cuboidal podoplanin-positive cells within SMA-negative epithelial structures embedded in extracellular matrix. Less frequently observed was the complete absence of, or only focal accumulations of podoplanin-positive fibroblasts outside of lymphatic vessels (podoplanin “low”, 4 of 24 biopsies). Patients in this group exhibited a lower index of systemic inflammation and a longer symptomatic period than in EPS patients with biopsies of the "mixed" type (p<0.05). In summary we confirm the increased expression of podoplanin in EPS, and distinguish EPS biopsies according to different podoplanin expression patterns which are associated with clinical parameters. Podoplanin might serve as a useful adjunct to the morphological workup of peritoneal biopsies.     

Flow in the well: computational fluid dynamics is essential in flow chamber construction

A perfusion system was developed to generate well defined flow conditions within a well of a standard multidish. Human vein endothelial cells were cultured under flow conditions and cell response was analyzed by microscopy. Endothelial cells became elongated and spindle shaped. As demonstrated by computational fluid dynamics (CFD), cells were cultured under well defined but time varying shear stress conditions. A damper system was introduced which reduced pulsatile flow when using volumetric pumps. The flow and the wall shear stress distribution were analyzed by CFD for the steady and unsteady flow field. Usage of the volumetric pump caused variations of the wall shear stresses despite the controlled fluid environment and introduction of a damper system. Therefore the use of CFD analysis and experimental validation is critical in developing flow chambers and studying cell response to shear stress. The system presented gives an effortless flow chamber setup within a 6-well standard multidish.     

Endothelial actin cytoskeleton remodeling during mechanostimulation with fluid shear stress

Fluid shear stress stimulation induces endothelial cells to elongate and align in the direction of applied flow. Using the complementary techniques of photoactivation of fluorescence and fluorescence recovery after photobleaching, we have characterized endothelial actin cytoskeleton dynamics during the alignment process in response to steady laminar fluid flow and have correlated these results to motility. Alignment requires 24 h of exposure to fluid flow, but the cells respond within minutes to flow and diminish their movement by 50%. Although movement slows, the actin filament turnover rate increases threefold and the percentage of total actin in the polymerized state decreases by 34%, accelerating actin filament remodeling in individual cells within a confluent endothelial monolayer subjected to flow to levels used by dispersed nonconfluent cells under static conditions for rapid movement. Temporally, the rapid decrease in filamentous actin shortly after flow stimulation is preceded by an increase in actin filament turnover, revealing that the earliest phase of the actin cytoskeletal response to shear stress is net cytoskeletal depolymerization. However, unlike static cells, in which cell motility correlates positively with the rate of filament turnover and negatively with the amount polymerized actin, the decoupling of enhanced motility from enhanced actin dynamics after shear stress stimulation supports the notion that actin remodeling under these conditions favors cytoskeletal remodeling for shape change over locomotion. Hours later, motility returned to pre-shear stress levels but actin remodeling remained highly dynamic in many cells after alignment, suggesting continual cell shape optimization. We conclude that shear stress initiates a cytoplasmic actin-remodeling response that is used for endothelial cell shape change instead of bulk cell translocation. atherosclerosis; cytoskeletal dynamics; endothelial cells; mechanotransduction     

Impacts of icodextrin on integrin-mediated wound healing of peritoneal mesothelial cells

AimsExposure to glucose and its metabolites in peritoneal dialysis fluid (PDF) results in structural alterations of the peritoneal membrane. Icodextrin-containing PDF eliminates glucose and reduces deterioration of peritoneal membrane function, but direct effects of icodextrin molecules on peritoneal mesothelial cells have yet to be elucidated. We compared the impacts of icodextrin itself with those of glucose under PDF-free conditions on wound healing processes of injured mesothelial cell monolayers, focusing on integrin-mediated cell adhesion mechanisms.Main methodsRegeneration processes of the peritoneal mesothelial cell monolayer were investigated employing an in vitro wound healing assay of cultured rat peritoneal mesothelial cells treated with icodextrin powder- or glucose-dissolved culture medium without PDF, as well as icodextrin- or glucose-containing PDF. The effects of icodextrin on integrin-mediated cell adhesions were examined by immunocytochemistry and Western blotting against focal adhesion kinase (FAK).Key findingsCell migration over fibronectin was inhibited in conventional glucose-containing PDF, while icodextrin-containing PDF exerted no significant inhibitory effects. Culture medium containing 1.5% glucose without PDF also inhibited wound healing of mesothelial cells, while 7.5% icodextrin-dissolved culture medium without PDF had no inhibitory effects. Glucose suppressed cell motility by inhibiting tyrosine phosphorylation of FAK, formation of focal adhesions, and cell spreading, while icodextrin had no effects on any of these mesothelial cell functions.SignificanceOur results demonstrate icodextrin to have no adverse effects on wound healing processes of peritoneal mesothelial cells. Preservation of integrin-mediated cell adhesion might be one of the molecular mechanisms accounting for the superior biocompatibility of icodextrin-containing PDF.     

Hydrodynamic thickening of lubricating fluid layer beneath sliding mesothelial tissues

The delicate mesothelial surfaces of the pleural space and other serosal cavities slide relative to each, lubricated by pleural fluid. In the absence of breathing motion, differences between lung and chest wall shape could eventually cause the lungs and chest wall to come into contact. Whether sliding motion keeps lungs and chest wall separated by a continuous liquid layer is not known. To explore the effects of hydrodynamic pressures generated by mesothelial sliding, we measured the thickness of the liquid layer beneath the peritoneal surface of a 3-cm disk of rat abdominal wall under a normal stress of 2 cm H2O sliding against a glass plate rotating at 0-1 rev/s. Thickness of the lubricating layer was determined microscopically from the appearance of fluorescent microspheres adherent to the tissue and glass. Usually, fluid thickness near the center of the tissue disk increased with the onset of glass rotation, increasing to 50-200 microm at higher rotation rates, suggesting hydrodynamic pumping. However, thickness changes often differed substantially among tissue samples and between clockwise and counter-clockwise rotation, and sometimes thickness decreased with rotation, suggesting that topographic features of the tissue are important in determining global hydrodynamic effects. We conclude that mesothelial sliding induces local hydrodynamic pressure gradients and global hydrodynamic pumping that typically increases the thickness of the lubricating fluid layer, moving fluid against the global pressure gradient. A similar phenomenon could maintain fluid continuity in the pleural space, reducing frictional force and shear stress during breathing.     

Peritoneal dialysis fluid activates calcium signaling and apoptosis in mesothelial cells

A larger diffusion of peritoneal dialysis (PD) is limited by the progressive deterioration of the dialysis membrane structure and function, characterized in vitro and in vivo by mesothelial cell loss and closely related to the use of bioincompatible dialysis solutions. The apoptosis rate of rat and human mesothelial cells incubated in commercial PD fluid (PDF, 4.25 g/dL dextrose) became significant as early as 1 h after PDF addition and reached a plateau at 4–5 h. This pattern was unchanged after exposure to 1.5 g/dL dextrose PDF or freshly prepared PDF, indicating that effects were independent on the dextrose strength and manufacturing procedures but strictly dependent on PDF composition. Molecular studies revealed that PDF exposure inactivated the physiological volume recovery from hypertonic shrinkage, accompanied by an abnormal Ca²⁺ signaling: a progressive intracellular Ca²⁺ ([Ca²⁺]_i) rise resulting from an increased Ca²⁺ entry. PDF also affected cytoskeleton integrity: early dissolution of actin filaments occurred well before the appearance of typical apoptosis features. Lastly, the PDF dependent apoptosis was almost completely prevented by the contemporary Ca²⁺ concentration decrease and K⁺ addition. This study suggests that the PDF dependent apoptosis arises from the extreme volume perturbations in mesothelial cells, turned out unable to regulate their volume back once exposed to a hyperosmolal medium containing high Ca²⁺ levels in the absence of K⁺, such PDF.     

Histological Criteria for Encapsulating Peritoneal Sclerosis – A Standardized Approach

Background

The two most relevant pathologies of long-term peritoneal dialysis (PD) are simple sclerosis and encapsulating peritoneal sclerosis (EPS). The histological differentiation of those two entities is difficult. The Aim of the study was to establish a method to standardize and facilitate the differentiation between simple sclerosis and EPS

Methods

We investigated 58 peritoneal biopsies - 31 EPS patients and 27 PD patients. Two blinded investigators analyzed 20 histological characteristics in EPS and PD patients.

Results

The following findings were significantly more common in EPS than in patients on PD without EPS: fibroblast like cells (FLC) (p<0.0001), mesothelial denudation (p<0.0001), decreased cellularity (p = 0.008), fibrin deposits (p<0.03), Fe deposits (p = 0.05), podoplanin vascular (p<0.0001), podoplanin avascular (p<0.0001). Using all predictor variables we trained the classification method Random Forest to categorize future cases. Podoplanin vascular and avascular were taken together (p<0.0001), FLC (p<0.0001), mesothelial denudation (p = 0.0005), calcification (p = 0.0026), acellular areas (p = 0.0094), and fibrin deposits (p = 0.0336) showed up as significantly important predictor variables. Estimated misclassification error rate when classifying new cases turned out to be 14%.

Conclusion

The introduced statistical method allows discriminating between simple sclerosis and EPS. The misclassification error will likely improve with every new case added to the database.     

Lesion of leukocytes, erythrocytes, and mesothelial cells by the cœlomic fluid ofEisenia fœtida earthworms

Cœlomic fluid ofEisenia fœtida earthworms is known to exert strong proteolytic, hemolytic, bacteriostatic, and cytolytic properties. Ultrastructural observations revealed that cœlomic fluid causes multiple ruptures and defects in the erythrocyte membrane as well as in the membrane of murine peritoneal leukocytes. Incubation of peritoneal cells in cœlomic fluid resulted in a disorganization of the macrophage surface microvilli, changes in the organization of cytoplasmic organelles and disruption and degranulation of mast cells. Severe mesothelial damage was observed after intraperitoneal administration of the cœlomic fluid.     

Tamoxifen Ameliorates Peritoneal Membrane Damage by Blocking Mesothelial to Mesenchymal Transition in Peritoneal Dialysis

Mesothelial-to-mesenchymal transition (MMT) is an auto-regulated physiological process of tissue repair that in uncontrolled conditions such as peritoneal dialysis (PD) can lead to peritoneal fibrosis. The maximum expression of peritoneal fibrosis induced by PD fluids and other peritoneal processes is the encapsulating peritoneal sclerosis (EPS) for which no specific treatment exists. Tamoxifen, a synthetic estrogen, has successfully been used to treat retroperitoneal fibrosis and EPS associated with PD. Hence, we used in vitro and animal model approaches to evaluate the efficacy of Tamoxifen to inhibit the MMT as a trigger of peritoneal fibrosis. In vitro studies were carried out using omentum-derived mesothelial cells (MCs) and effluent-derived MCs. Tamoxifen blocked the MMT induced by transforming growth factor (TGF)-β1, as it preserved the expression of E-cadherin and reduced the expression of mesenchymal-associated molecules such as snail, fibronectin, collagen-I, α-smooth muscle actin, and matrix metalloproteinse-2. Tamoxifen-treatment preserved the fibrinolytic capacity of MCs treated with TGF-β1 and decreased their migration capacity. Tamoxifen did not reverse the MMT of non-epitheliod MCs from effluents, but it reduced the expression of some mesenchymal molecules. In mice PD model, we demonstrated that MMT progressed in parallel with peritoneal membrane thickness. In addition, we observed that Tamoxifen significantly reduced peritoneal thickness, angiogenesis, invasion of the compact zone by mesenchymal MCs and improved peritoneal function. Tamoxifen also reduced the effluent levels of vascular endothelial growth factor and leptin. These results demonstrate that Tamoxifen is a therapeutic option to treat peritoneal fibrosis, and that its protective effect is mediated via modulation of the MMT process.     

Peritoneal repairing cells: a type of bone marrow derived progenitor cells involved in mesothelial regeneration

The peritoneal mesothelium exhibits a high regenerative ability. Peritoneal regeneration is concomitant with the appearance, in the coelomic cavity, of a free‐floating population of cells whose origin and functions are still under discussion. We have isolated and characterized this cell population and we have studied the process of mesothelial regeneration through flow cytometry and confocal microscopy in a murine model lethally irradiated and reconstituted with GFP‐expressing bone marrow cells. In unoperated control mice, most free cells positive for mesothelin, a mesothelial marker, are green fluorescent protein (GFP). However, 24 hrs after peritoneal damage, free mesothelin⁺/ GFP⁺ cells appear in peritoneal lavages. Cultured lavage peritoneal cells show colocalization of GFP with mesothelial (mesothelin, cytokeratin) and fibroblastic markers. Immunohistochemical staining of the peritoneal wall also revealed colocalization of GFP with mesothelial markers and with procollagen‐1 and smooth muscle α‐actin. This was observed in the injured area as well as in the surrounding not‐injured peritoneal surfaces. These cells, which we herein call peritoneal repairing cells (PRC), are very abundant 1 week after surgery covering both the damaged peritoneal wall and the surrounding uninjured area. However, they become very scarce 1 month later, when the mesothelium has completely healed. We suggest that PRC constitute a type of monocyte‐derived cells, closely related with the tissue‐repairing cells known as ‘fibrocytes’ and specifically involved in peritoneal reparation. Thus, our results constitute a synthesis of the different scenarios hitherto proposed about peritoneal regeneration, particularly recruitment of circulating progenitor cells and adhesion of free‐floating coelomic cells.     

Evaluation of different culture techniques of osteoblasts on 3D scaffolds

Bones adjust their structure to withstand the mechanical demands they experience. It is suggested that flow-derived shear stress may be the most significant and primary mediator of mechanical stimulation. In this study, we designed and fabricated a fluid flow cell culture system that can load shear stress onto cells cultured on 3D scaffolds. We evaluated the effect of different culture techniques, namely, (1) continuous perfusion fluid flow, (2) intermittent perfusion fluid flow, and (3) static condition, on the proliferation of osteoblasts seeded on partially deproteinized bones. The flow rate was set at 1 ml/min for all the cells cultured using flow perfusion and the experiment was conducted for 12 days. Scanning electron microscopy analysis indicated an increase in cell proliferation for scaffolds subjected to fluid shear stress. In addition, the long axes of these cells lengthened along the flowing fluid direction. Continuous perfusion significantly enhanced cell proliferation compared to either intermittent perfusion or static condition. All the results demonstrated that fluid shear stress is able to enhance the proliferation of cells and change the form of cells.     

ST2 blockade mitigates peritoneal fibrosis induced by TGF‐β and high glucose

Peritoneal fibrosis (PF) is an intractable complication of peritoneal dialysis (PD) that leads to peritoneal membrane failure. This study investigated the role of suppression of tumorigenicity (ST)2 in PF using patient samples along with mouse and cell‐based models. Baseline dialysate soluble (s)ST2 level in patients measured 1 month after PD initiation was 2063.4 ± 2457.8 pg/mL; patients who switched to haemodialysis had elevated sST2 levels in peritoneal effluent (1576.2 ± 199.9 pg/mL, P = .03), which was associated with PD failure (P = .04). Baseline sST2 showed good performance in predicting PD failure (area under the receiver operating characteristic curve = 0.780, P = .001). In mice with chlorhexidine gluconate‐induced PF, ST2 was expressed in fibroblasts and mesothelial cells within submesothelial zones. In primary cultured human peritoneal mesothelial cells (HPMCs), transforming growth factor‐β treatment increased ST2, fibronectin, β‐galactosidase and Snail protein levels and decreased E‐cadherin level. Anti‐ST2 antibody administration reversed the up‐regulation of ST2 and fibronectin expression; it also reduced fibrosis induced by high glucose (100 mmol/L) in HPMCs. Thus, high ST2 level in dialysate is a marker for fibrosis and inflammation during peritoneal injury, and blocking ST2 may be an effective therapeutic strategy for renal preservation.     

Connective tissue growth factor is a positive regulator of epithelial–mesenchymal transition and promotes the adhesion with gastric cancer cells in human peritoneal mesothelial cells

Connective tissue growth factor (CTGF) is involved in human cancer development and progression. Epithelial to mesenchymal transition (EMT) plays an important role in many biological processes. In this study, we wished to investigate the role of CTGF in EMT of peritoneal mesothelial cells and the effects of CTGF on adhesion of gastric cancer cells to mesothelial cells. Human peritoneal mesothelial cells (HPMCs) were cultured with TGF-β₁ or various concentrations of CTGF for different time. The EMT process was monitored by morphology. Real-time RT-PCR and Western blot were used to evaluate the expression of vimentin, α-SMA , E-cadherin and β-catenin. RNA interference was used to achieve selective and specific knockdown of CTGF. We demonstrated that CTGF induced EMT of mesothelial cells in a dose- and time-dependent manner. HPMCs were exposed to TGF-β₁ also underwent EMT which was associated with the induction of CTGF expression. Transfection with CTGF siRNA was able to reverse the EMT partially after treatment of TGF-β₁. Moreover, the induced EMT of HPMCs was associated with an increased adhesion of gastric cancer cells to mesothelial cells. These findings suggest that CTGF is not only an important mediator but a potent activator of EMT in peritoneal mesothelial cells, which in turn promotes gastric cancer cell adhesion to peritoneum.     

Arterial shear stress stimulates surface expression of the endothelial glycoprotein Ib complex

Exposure to shear stress has been shown to alter the expression of a number of surface components of cultured endothelial cells (EC). However, relatively few studies have examined the status of human EC surface proteins after prolonged flow, more closely corresponding to the steady state in vivo. Since the promoter region of glycoprotein (Gp) Ib alpha contains several copies of a putative shear stress response element, 5'-GAGACC-3', we investigated the response of cultured human umbilical vein EC (HUVEC) GpIb alpha to shear stress over a 72 h time period. In response to 30 dynes/cm2 of shear stress, total cell content of GpIb alpha protein was markedly increased above static levels at 7 and 24 h, as determined immunohistochemically. Western blot analysis of whole cell lysates after 24, 48, and 72 h of shear treatment demonstrated a 2.4-, 4.1-, and 3.2-fold increase in total GpIb alpha protein, respectively. Cell surface protein expression of GpIb alpha increased 2.5-fold at 7 h, as measured by quantitative immunofluorescence, and remained at that level at 24 h. After 48 h of shear stress, cell surface GpIb alpha, GpIX, and GpV, analyzed by flow cytometric analysis, were further increased over the levels observed at 24 h. The increase in cell surface membrane expression of GPIb alpha at 24, 48, and 72 h was confirmed by immunoprecipitation of biotinylated surface proteins. No upregulation of GpIb alpha was noted after exposure to shear stress of 1-3 dynes/cm2. These observations imply that under steady-state arterial shear conditions endothelial expression of the GpIb complex is significantly greater than observed in static EC cultures, and raise the possibility of a more important role for this complex under flow, rather than static conditions.     

The biased lamellipodium development and microtubule organizing center position in vascular endothelial cells migrating under the influence of fluid flow*

Summary— To analytically study the morphological responses of vascular endothelial cells (ECs) to fluid flow, we designed a parallel plate flow culture chamber in which cells were cultured under fluid shear stress ranging from 0.01 to 2.0 Pa for several days. Via a viewing window of the chamber, EC responses to known levels of fluid shear stress were monitored either by direct observations or by a video-enhanced time-lapse microscopy. Among the responses of cultured ECs to flow, morphological responses take from hours to days to be fully expressed, except for the fluid shear stress-dependent motility pattern change we reported earlier which could be detected within 30 min of flow changes. We report here that ECs exposed to more than 1.0 Pa of fluid shear shear stress have developed lamellipodia in the direction of flow in 10 min. This is the fastest structurally identifiable EC response to fluid shear stress. This was a reversible response. When the flow was stopped or reduced to the level which exerted less than 0.1 Pa of fluid shear stress, the biased lamellipodium development was lost within several minutes. The microtubule organizing center was located posterior to the nucleus in ECs under the influence of flow. However, this position was established only in ECs responding to fluid shear stress for longer than 1 h, indicating that positioning of the microtubule organizing center was not the reason for, but rather the result of, the biased lamellipodium response. Colcemid-treated ECs responded normally to flow, indicating that microtubules were not involved in both flow sensing and the flow-induced, biased lamellipodium development.     

Aliskiren prevents the toxic effects of peritoneal dialysis fluids during chronic dialysis in rats

The benefits of long-term peritoneal dialysis (PD) in patients with end-stage renal failure are short-lived due to structural and functional changes in the peritoneal membrane. In this report, we provide evidence for the in vitro and in vivo participation of the renin-angiotensin-aldosterone system (RAAS) in the signaling pathway leading to peritoneal fibrosis during PD. Exposure to high-glucose PD fluids (PDFs) increases damage and fibrosis markers in both isolated rat peritoneal mesothelial cells and in the peritoneum of rats after chronic dialysis. In both cases, the addition of the RAAS inhibitor aliskiren markedly improved damage and fibrosis markers, and prevented functional modifications in the peritoneal transport, as measured by the peritoneal equilibrium test. These data suggest that inhibition of the RAAS may be a novel way to improve the efficacy of PD by preventing inflammation and fibrosis following peritoneal exposure to high-glucose PDFs.     

Effect of fluid force on vascular cell function

Endothelial cells (ECs) that line the inner surface of blood vessels are continuously exposed to fluid frictional force (shear stress) induced by blood flow, and shear stress affects the intracellular calcium ([Ca2+]i), which initiates cellular responses. Here, we studied the effect of long-term exposure of shear stress on [Ca2+]i responses in cultured ECs by using a confocal laser microscope and calcium indicator. At the initiation of shear stress of 20 dyn/cm2 (0 hr), 27% of the cells exhibited [Ca2+]i responses. This percentage gradually decreased with increasing exposure time, reaching about 4% after 24 hr of exposure. These data indicate that long-term shear-stress exposure affects [Ca2+]i responses in cultured ECs. Furthermore, we studied the effect of magnitude of shear stress on macromolecule uptake. For the low shear-stress, the uptake was enhanced, whereas the uptake was inhibited for higher shear-stress.