Rat Model Of Peritoneal Dialysis Research Articles

Relationship between fill volume and transport in peritoneal dialysis-from bench to bedside.

Larger fill volumes in peritoneal dialysis (PD) typically improve small solute clearance and water removal, and vice versa-but the relationship between intraperitoneal volume and the capacities for solute and water transport in PD has been little studied. Here, it is proposed that this relative relationship is described by a simple ratio (Volumenew/Volumeold)2/3 up to a critical break-point volume, beyond which further volume increase is less beneficial in terms of solute and water removal. To scrutinize this hypothesis, experiments were conducted in a rat model of PD alongside a retrospective analysis of data from a prior clinical study. Rats underwent PD with either three consecutive fills of 8 + 8 + 8 mL (n = 10) or 12 + 12 + 12 mL (n = 10), with 45-minute dwell time intervals. This approach yielded 60 estimations of water and solute transport, characterized by osmotic conductance to glucose and solute diffusion capacities, respectively. Comparative analysis of the predictive efficacy of the two models-the simple ratio versus the break-point model-was performed using Monte Carlo cross-validation. The break-point model emerged as a superior predictor for both water and solute transfer, demonstrating its capability to characterize both experimental data from rats and clinical data from patients. The present analysis indicates that relatively simple calculations can be used to approximate clinical effects on solute and water removal when prescribing a lower or higher fill volume to patients with PD.

Mechanism of Fushen Granules treat peritoneal dialysis-related peritonitis by regulating TLR4/NF-κB pathway:based on network pharmacology and animal experiments

Network pharmacology was employed to probe into the mechanism of Fushen Granules in treating peritoneal dialysis-rela-ted peritonitis(PDRP) in rats. The main active components of Fushen Granules were searched against the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform, and their targets were predicted. PDRP-related targets were retrieved from DisGeNET and other databases. The common targets shared by the drug and the disease were identified by the online tool, and protein-protein interaction(PPI) network of the common targets. The obtained 276 common targets were imported into DAVID for GO function enrichment and KEGG pathway enrichment. The main signaling pathway of Fushen Granules in the treatment of PDRP was predicted as Toll-like receptor 4(TLR4)/nuclear factor(NF)-κB. The rat model of uremia was induced by 5/6 nephrectomy. From two weeks after operation, the rat model of peritoneal dialysis(PD) was established by intraperitoneal injection of 20 mL dialysate with 1.25% glucose every day. The sham operation group and model group received 2 mL normal saline by gavage every day. The rats in Fushen Gra-nules groups were administrated with 2 mL solutions of low-(0.54 g·kg~(-1)), medium-(1.08 g·kg~(-1)) and high-dose(2.16 g·kg~(-1)) Fushen Granules every day. The bifico group received 2 mL(113.4 mg·kg~(-1)) of bifico solution every day. At the end of the 8th week, the levels of serum creatinine(Scr) and blood urea nitrogen(BUN) in each group were measured. The serum levels of hypersensitive C reactive protein(hs-CRP), tumor necrosis factor(TNF)-α, and interleukin(IL)-6 were measured, and the pathological changes in the colon tissue were observed by hematoxylin-eosin(HE) staining. The serum levels of lipopolysaccharide(LPS) and lipopolysaccharide-binding protein(LBP) of rats were measured, and the expression levels of LBP, TLR4, NF-κB p65, inhibitor of κB kinase α(IκBα), TNF-α, and IL-1β in the colon tissue were determined. Compared with sham operation group, the model group had abnormal structure of all layers of colon tissue, sparse and shorter intestinal villi, visible edema in mucosal layer, wider gap, obvious local inflammatory cell infiltration, significantly decreased body weight(P<0.01), and significantly increased kidney function index(Scr, BUN) content(P<0.01). Serum levels of inflammatory cytokines(hs-CRP, TNF-α, IL-6), LPS and LBP were significantly increased(P<0.01), protein expressions of LBP, TLR4, NF-κB p65, TNF-α and IL-1β were significantly increased(P<0.01), and protein expressions of IκBα were significantly decreased(P<0.01). Compared with model group, intestinal villi damage in colonic tissue of rats in low-, medium-and high-dose Fushen Granules groups and bifico group were alleviated to different degrees, edema in submucosa was alleviated, space was narrowed, and inflammatory cell infiltration in lamina propria was reduced. The contents of renal function index(Scr, BUN) and serum inflammatory factors(hs-CRP, TNF-α, IL-6) were significantly decreased(P<0.05 or P<0.01) in medium-and high-dose Fushen Granules groups and bifico group(P<0.05 or P<0.01). Serum LPS and LBP contents in Fushen Granules group and bifico group were significantly decreased(P<0.01), protein expressions of LBP, TLR4, NF-κB p65, TNF-α and IL-1β in Fushen Granules group were significantly decreased(P<0.05 or P<0.01), and protein expressions of IκBα were significantly increased(P<0.01). The expression of LBP protein in bifico group was significantly decreased(P<0.01). The results suggest that Fushen Granules can protect the residual renal function of PD rats, reduce the inflammatory response, and protect the colon tissue. Based on network pharmacology, TLR4/NF-κB pathway may be the main signaling pathway of Fushen granule in the treatment of PDRP. The results showed that Fushen Granules could improve intestinal inflammation and protect intestinal barrier to prevent PDRP by regulating the expression of key factors in TLR4/NF-κB pathway in colon of PD rats.

Glucose Induces ER Stress Response-Mediated Peritoneal Mesothelial Cell Death.

Peritoneal dialysis (PD) fluid, which contains a high concentration of glucose, is involved in peritoneal damage after long-term use. The mechanisms through which glucose induces damage to the mesothelium have not been clearly elucidated. Although, endoplasmic reticulum (ER) stress response is associated with several diseases, the involvement of ER stress in peritoneal damage has not yet been demonstrated. Primary-cultured rat peritoneal mesothelial cells (RPMCs) and rat PD model were used to investigate the influence of glucose on the peritoneum. Cells treated with glucose were examined for cytotoxicity, induction of apoptosis, and activation of the ER stress pathway. Glucose treatment of RPMCs induced cell death at concentrations higher than 3%. Annexin V positive, that is a feature of apoptosis, occurred in dead cells. Treatment with glucose led to the activation of protein kinase R-like ER kinase (PERK) and eukaryotic translation initiation factor-2α (eIF-2α). Glucose also induced the expression and nuclear translocation of homologous protein C/EBP. Cell death was rescued by the integrated stress response inhibitor, ISRIB, which suppresses the integrated stress response pathway, including ER stress. Glucose in PD fluid induces PERK/eIF-2α-mediated ER stress in RPMCs, resulting in apoptosis. This cellular stress may cause peritoneal damage in patients receiving PD.

Transcriptomic analysis identifies novel candidates in cardiorenal pathology mediated by chronic peritoneal dialysis

Peritoneal dialysis (PD) is associated with increased cardiovascular (CV) risk. Studies of PD-related CV pathology in animal models are lacking despite the clinical importance. Here we introduce the phenotypic evaluation of a rat model of cardiorenal syndrome in response to chronic PD, complemented by a rich transcriptomic dataset detailing chronic PD-induced changes in left ventricle (LV) and kidney tissues. This study aims to determine how PD alters CV parameters and risk factors while identifying pathways for potential therapeutic targets. Sprague Dawley rats underwent Sham or 5/6 nephrectomy (5/6Nx) at 10 weeks of age. Six weeks later an abdominal dialysis catheter was placed in all rats before random assignment to Control or PD (3 daily 1-h exchanges) groups for 8 days. Renal and LV pathology and transcriptomic analysis was performed. The PD regimen reduced circulating levels of BUN in 5/6Nx, indicating dialysis efficacy. PD did not alter blood pressure or cardiovascular function in Sham or 5/6Nx rats, though it attenuated cardiac hypertrophy. Importantly PD increased serum triglycerides in 5/6Nx rats. Furthermore, transcriptomic analysis revealed that PD induced numerous changed transcripts involved with inflammatory pathways, including neutrophil activation and atherosclerosis signaling. We have adapted a uremic rat model of chronic PD. Chronic PD induced transcriptomic changes related to inflammatory signaling that occur independent of 5/6Nx and augmented circulating triglycerides and predicted atherosclerosis signaling in 5/6Nx LV tissues. The changes are indicative of increased CV risk due to PD and highlight several pathways for potential therapeutic targets.

Effects of sitagliptin on peritoneal membrane: The potential role of mesothelial cell tight junction proteins.

The roles of tight junction (TJ) proteins in peritoneal membrane transport and peritoneal dialysis (PD) require further characterisation. Dipeptidyl peptidase-4 is expressed in mesothelial cells, and its activity may affect peritoneal membrane function and morphology. Human peritoneal mesothelial cells (HPMCs) were isolated and cultured from omentum obtained during abdominal surgery, and paracellular transport functions were evaluated by measuring transmesothelial electrical resistance (TMER) and dextran flux. Sprague-Dawley rats were infused daily with 4.25% peritoneal dialysate with and without sitagliptin administration for 8 weeks. At the end of this period, rat peritoneal mesothelial cells (RPMCs) were isolated to evaluate TJ protein expression. In HPMCs, the protein expression of claudin-1, claudin-15, occludin and E-cadherin was decreased by TGF-β treatment but reversed by sitagliptin co-treatment. TMER was decreased by TGF-β treatment but improved by sitagliptin co-treatment. Consistent with this, dextran flux was increased by TGF-β treatment and reversed by sitagliptin co-treatment. In the animal experiment, sitagliptin-treated rats had a lower D2/D0 glucose ratio and a higher D2/P2 creatinine ratio than PD controls during the peritoneal equilibration test. Protein expression of claudin-1, claudin-15 and E-cadherin decreased in RPMCs from PD controls but was not affected in those from sitagliptin-treated rats. Peritoneal fibrosis was induced in PD controls but ameliorated in sitagliptin-treated rats. The expression of TJ proteins including claudin-1 and claudin-15 was associated with transport function both in HPMCs and in a rat model of PD. Sitagliptin prevents peritoneal fibrosis in PD and can potentially restore peritoneal mesothelial cell TJ proteins.

Blockade of prostaglandin E2 receptor 4 ameliorates peritoneal dialysis-associated peritoneal fibrosis.

Inflammatory responses in the peritoneum contribute to peritoneal dialysis (PD)-associated peritoneal fibrosis. Results of our previous study showed that increased microsomal prostaglandin E synthase-1-mediated production of prostaglandin E2 (PGE2) contributed to peritoneal fibrosis. However, the role of its downstream receptor in the progression of peritoneal fibrosis has not been established. Here, we examined the role of PGE2 receptor 4 (EP4) in the development of peritoneal fibrosis. EP4 was significantly upregulated in peritoneal tissues of PD patients with ultrafiltration failure, along with the presence of an enhanced inflammatory response. In vitro experiments showed that exposure to high glucose concentrations enhanced EP4 expression in rat peritoneal mesothelial cells (RPMCs). High-glucose-induced expression of inflammatory cytokines (monocyte chemoattractant protein-1, tumour necrosis factor α, and interleukin 1β) was significantly reduced in RPMCs treated with ONO-AE3-208, an EP4 receptor antagonist. ONO-AE3-208 also significantly decreased the expression of extracellular matrix proteins induced by high glucose concentrations. Furthermore, ONO-AE3-208 blunted activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome and phosphorylation of nuclear factor kappa B (NF-κB) (p-p65). To further investigate the functional role of EP4, ONO-AE3-208 was administrated for 4weeks in a rat model of PD, the results of which showed that ONO-AE3-208 inhibited peritoneal fibrosis and improved peritoneal dysfunction. Additionally, inflammatory cytokines in the peritoneum of PD rats treated with ONO-AE3-208 were downregulated, in line with inhibition of the NLRP3 inflammasome and NF-κB phosphorylation. In conclusion, an EP4 antagonist reduced the development of peritoneal fibrosis, possibly by suppressing NLRP3 inflammasome- and p-p65-mediated inflammatory responses. Our findings suggest that an EP4 antagonist may be therapeutically beneficial for PD-associated peritoneal fibrosis.

Phloretin Improves Ultrafiltration and Reduces Glucose Absorption during Peritoneal Dialysis in Rats.

Harmful glucose exposure and absorption remain major limitations of peritoneal dialysis (PD). We previously showed that inhibition of sodium glucose cotransporter 2 did not affect glucose transport during PD in rats. However, more recently, we found that phlorizin, a dual blocker of sodium glucose cotransporters 1 and 2, reduces glucose diffusion in PD. Therefore, either inhibiting sodium glucose cotransporter 1 or blocking facilitative glucose channels by phlorizin metabolite phloretin would reduce glucose transport in PD. We tested a selective blocker of sodium glucose cotransporter 1, mizagliflozin, as well as phloretin, a nonselective blocker of facilitative glucose channels, in an anesthetized Sprague-Dawley rat model of PD. Intraperitoneal phloretin treatment reduced glucose absorption by >30% and resulted in a >50% higher ultrafiltration rate compared with control animals. Sodium removal and sodium clearances were similarly improved, whereas the amount of ultrafiltration per millimole of sodium removed did not differ. Mizagliflozin did not influence glucose transport or osmotic water transport. Taken together, our results and previous results indicate that blockers of facilitative glucose channels may be a promising target for reducing glucose absorption and improving ultrafiltration efficiency in PD.

Dual SGLT1/SGLT2 inhibitor phlorizin reduces glucose transport in experimental peritoneal dialysis.

Glucose absorption during peritoneal dialysis (PD) is commonly assumed to occur via paracellular pathways. We recently showed that SGLT2 inhibition did not reduce glucose absorption in experimental PD, but the potential role of glucose transport into cells is still unclear. Here we sought to elucidate the effects of phlorizin, a non-selective competitive inhibitor of sodium glucose co-transporters 1 and 2 (SGLT1 and SGLT2), in an experimental rat model of PD. A 120-min PD dwell was performed in 12 anesthetised Sprague-Dawley rats using 1.5% glucose fluid with a fill volume of 20 mL with (n = 6) or without (n = 6) intraperitoneal phlorizin (50 mg/L). Several parameters for peritoneal water and solute transport were monitored during the treatment. Phlorizin markedly increased the urinary excretion of glucose, lowered plasma glucose and increased plasma creatinine after PD. Median glucose diffusion capacity at 60 min was significantly lower (p < 0.05) being 196 µL/min (IQR 178-213) for phlorizin-treated animals compared to 238 µL/min (IQR 233-268) in controls. Median fractional dialysate glucose concentration at 60 min (D/D 0) was significantly higher (p < 0.05) in phlorizin-treated animals being 0.65 (IQR 0.63-0.67) compared to 0.61 (IQR 0.60-0.62) in controls. At 120 min, there was no difference in solute or water transport across the peritoneal membrane. Our findings indicate that a part of glucose absorption during the initial part of the dwell occurs via transport into peritoneal cells.

MiR-122-5p promotes peritoneal fibrosis in a rat model of peritoneal dialysis by targeting Smad5 to activate Wnt/β-catenin pathway

Peritoneal fibrosis (PF) is the main reason leading to declining efficiency and ultrafiltration failure of peritoneum, which restricts the application of peritoneal dialysis (PD). We aimed to investigate the effects and mechanisms of miR-122-5p on the PF. Sprague-Dawley (SD) rats were infused with glucose-based standard PD fluid to establish PF model. HE staining was performed to evaluate the extent of PF. Real-time fluorescence quantitative polymerase chain reaction (RT-qPCR) and fluorescence in situ hybridization (FISH) were performed to measure the expression level of miR-122-5p. Western blot was used to test the expression of transforming growth factor (TGF)-β1, platelet-derived growth factor (PDGF)-A, Fibronectin 1 (FN1), extracellular matrix protein 1 (ECM1), Smad5, α-smooth muscle actin (SMA), collagen type 1(COL-1), Vimentin, E-Cadherin, Wnt1, β-catenin, p-β-catenin, c-Myc, c-Jun, and Cyclin D1. Immunohistochemistry (IHC) staining was used to detect type I collagen alpha 1 (Col1α1), α-SMA, and E-Cadherin expression. We found PF was glucose concentration-dependently enhanced in peritoneum of PD rat. The PD rats showed increased miR-122-5p and decreased Smad5 expression. MiR-122-5p silencing improved PF and epithelial–mesenchymal transition (EMT) process in PD rats. MiR-122-5p silencing attenuated the activity of the Wnt/β-catenin signaling pathway. Importantly, dual-luciferase reporter assay showed Smad5 was a target gene of miR-122-5p. Smad5 overexpression significantly reversed the increases of PF and EMT progression induced by miR-122-5p overexpression. Moreover, miR-122-5p mimic activated Wnt/β-catenin activity, which was blocked by Smad5 overexpression. Overall, present results demonstrated that miR-122-5p overexpression showed a deterioration effect on PD-related PF by targeting Smad5 to activate Wnt/β-catenin pathway.

Comparison of mesenchymal stromal cells from peritoneal dialysis effluent with those from umbilical cords: characteristics and therapeutic effects on chronic peritoneal dialysis in uremic rats

BackgroundA long-term of peritoneal dialysis (PD) using a hypertonic PD solution (PDS) leads to patient’s peritoneal membrane (PM) injury, resulting in ultrafiltration failure (UFF) and PD drop-out. Our previous study shows that PD effluent-derived mesenchymal stromal cells (pMSCs) prevent the PM injury in normal rats after repeated exposure of the peritoneal cavity to a PDS. This study was designed to compare the cytoprotection between pMSCs and umbilical cord-derived MSCs (UC-MSCs) in the treatment of both PM and kidney injury in uremic rats with chronic PD.Methods5/6 nephrectomized (5/6Nx) Sprague Dawley rats were intraperitoneally (IP) injected Dianeal (4.25% dextrose, 10 mL/rat/day) and were treated with pMSCs or umbilical cord (UC)-MSCs (approximately 2 × 106/rat/week, IP). Ultrafiltration was determined by IP injection of 30 mL of Dianeal (4.25% dextrose) with 1.5-h dewell time, and kidney failure by serum creatinine (SCr) and blood urea nitrogen (BUN). The structure of the PM and kidneys was assessed using histology. Gene expression was examined using quantitative reverse transcription PCR, and protein levels using flow cytometric and Western blot analyses.ResultsWe showed a slight difference in the morphology between pMSCs and UC-MSCs in plastic dishes, and significantly higher expression levels of stemness-related genes (NANOG, OCT4, SOX2, CCNA2, RAD21, and EXO1) and MSCs surface markers (CD29, CD44, CD90 and CD105) in UC-MSCs than those in pMSCs, but no difference in the differentiation to chondrocytes, osteocytes or adipocytes. pMSC treatment was more effective than UC-MSCs in the protection of the MP and remnant kidneys in 5/6Nx rats from PDS-induced injury, which was associated with higher resistance of pMSCs than UC-MSCs to uremic toxins in culture, and more reduction of peritoneal mesothelial cell death by the secretome from pMSCs than from UC-MSCs in response to PDS exposure. The secretome from both pMSCs and UC-MSCs similarly inactivated NOS2 in activated THP1 cells.ConclusionsAs compared to UC-MSCs, pMSCs may more potently prevent PDS-induced PM and remnant kidney injury in this uremic rat model of chronic PD, suggesting that autotransplantation of ex vivo-expanded pMSCs may become a promising therapy for UFF and deterioration of remnant kidney function in PD patients.

Correction: Effects of RNA interference-mediated gene silencing of VEGF on the ultrafiltration failure in a rat model of peritoneal dialysis.

Correction: Effects of RNA interference-mediated gene silencing of VEGF on the ultrafiltration failure in a rat model of peritoneal dialysis.

Fushen Granule, A Traditional Chinese Medicine, ameliorates intestinal mucosal dysfunction in peritoneal dialysis rat model by regulating p38MAPK signaling pathway.

Fushen Granule (FSG) is a Chinese medicinal formular prepared in hospital to treat intestinal mucosal dysfunction induced by peritoneal dialysis (PD). However, the mechanisms of this formular has not been studied yet. The present study was designed to investigate the effect of FSG against intestinal dysfunction during PD treatment and explore the potential mechanisms using a rat PD model. In the present study, the effect of FSG on improving intestinal mucosal architecture injury was intuitively shown by hematoxylin-eosin staining, the serum levels of DAO and D-lactate were measured to evaluate the intestinal permeability by the DAO Assay Kit and D-Lactic Acid ELISA Kit. The expression of the intestinal mucosal barrier related inflammation factor by real-time PCR. The main effective constituents of FSG were characterized by UPLC/Q-TOF analysis, and the targets and pathways of the constituents were predicted via TCMSP database and IPA. the activation of p38MAPK signaling pathway by western blotting. HE staining results showed that FSG protected against intestinal mucosal injury in pathology in PD rats. FSG decreased the intestinal mucosal permeability by increasing the transepithelial electrical resistance (TER) level and decreasing the intestinal clearance of fluorescein-isothiocyanate dextran (FD4) and the level of D-lactate and diamine oxidase (DAO). FSG significantly decreased the expression of ICAM-1, IL-1β, iNOS and TNF-α, and further inhibited the activation of p38MAPK signaling pathway via down-regulating the expression of P-p38MAPK and up-regulating the expression of DUSP1, occludin, and ZO-1. This study demonstrates that FSG ameliorated intestinal mucosal dysfunction in PD by decreasing expression of pro-inflammatory cytokines and inhibiting the activation of p38MAPK signaling pathway. The results provide a promising basis for the alternative medicine treatment of intestinal mucosal dysfunction in PD.

Curcumin ameliorates peritoneal fibrosis via inhibition of transforming growth factor-activated kinase 1 (TAK1) pathway in a rat model of peritoneal dialysis

BackgroundPeritoneal fibrosis (PF) remains a serious complication of long-term peritoneal dialysis (PD). The goal of this study was to investigate the anti-fibrotic effects of curcumin on the PF response to PD and its’ mechanism.MethodsMale Sprague–Dawley rats were infused with 20 mL of 4.25% glucose-based standard PD fluid for 8 consecutive weeks to establish PF model and then divided into five groups: Control, received sham operation and 0.9% physiological saline; PD, received 4.25% standard PD fluid; Curcumin, PD rats injected intraperitoeally with curcumin for 8 weeks at doses of 10, 20 or 40 mg/kg. Masson’s staining was performed to evaluate the extent of PF. Peritoneal Equilibration Test (PET) was conducted to assess ultrafiltration volume (UFV) and mass transfer of glucose (MTG), quantitative RT-PCR, and immunohistochemistry or western blotting were performed to measure the expression levels of inflammation and fibrosis-associated factors. We also detected the TGF-β1 in peritoneal fluid by ELISA.ResultsCompared with the control group, the PD rats showed decreased UFV (2.54 ± 0.48 to 9.87 ± 0.78 mL, p < 0.05] and increased MTG (18.99 ± 0.86 to 10.85 ± 0.65 mmol/kg, p < 0.05) as well as obvious fibroproliferative response, with markedly increased peritoneal thickness (178.33 ± 4.42 to 25.26 ± 0.32um, p < 0.05) and higher expression of a-SMA, collagen I and TGF-β1. Treatment with curcumin significantly increased UFV, reduced MTG and peritoneal thickness of PD rats. The elevated TGF-β1 in peritoneal fluid of PD rats was significantly decreased by curcumin. It attenuated the increase in protein and mRNA of TGF-β1, α-SMA and collagen I in peritoneum of PD rats. The mRNA expressions of TAK1, JNK and p38, as well as the protein expressions of p-TAK1, p-JNK and p-p38 in peritoneum of PD rats were reduced by curcumin.ConclusionsPresent results demonstrate that curcumin showed a protective effect on PD-related PF and suggest an implication of TAK1, p38 and JNK pathway in mediating the benefical effects of curcumin.

MiR-200a ameliorates peritoneal fibrosis and functional deterioration in a rat model of peritoneal dialysis

Peritoneal fibrosis is recognised as the main cause of the technical failure of peritoneal dialysis (PD), and currently, there are no specific and effective anti-fibrosis therapies. We have found that miR-200a is down-regulated in a rat model of PD-related peritoneal fibrosis (PF) and could inhibit transforming growth factor beta 1 (TGF-β1)-induced epithelial-mesenchymal transition (EMT) in peritoneal mesothelial cells by target ZEB1/2. However, its treatment role in vivo is still largely unclear. In this study, we examined the therapeutic potential for miR-200a on PD-related PF in a rat model of PD induced by daily infusion of 4.25% dextrose-containing dialysate. Male Sprague–Dawley rats were divided into four groups: control group, PD group, PD + miR-agomir-NC group, and PD + miR-200a-agomir group (n = 5 in each group). MiR-200a agomir was delivered into the peritoneum by intra-peritoneal injection on days 10 and 20 after PD. We found that treatment with miR-200a agomir significantly reduced the collagen volume fraction (CVF) of the peritoneum and prevented peritoneal dysfunction. The up-regulation of the EMT marker (decreased E-cadherin and increased α-smooth muscle actin) and extracellular matrix (fibronectin and collagen I) was significantly ameliorated by miR-200a in the PD + miR-200a-agomir group. Furthermore, we demonstrated that miR-200a inhibition of PF in vivo was associated with the suppression of ZEB1 and 2, which were proved to be the target of miR-200a in our previous study. In conclusion, results from the present study suggest that treatment with miR-200a may represent a novel and effective therapy for PD-related PF.

MiR-200a negatively regulates TGF-β1-induced epithelial-mesenchymal transition of peritoneal mesothelial cells by targeting ZEB1/2 expression.

Although epithelial-mesenchymal transition (EMT) of peritoneal mesothelial cells was recognized as the key process of peritoneal fibrosis, which is a major cause of peritoneal failure related to peritoneal dialysis (PD), mechanisms underlying these processes remain largely unknown. In this study, we found that miR-200a was significantly downregulated in peritoneal tissues with fibrosis in a rat model of PD. In vitro, transforming growth factor (TGF)-β1-induced EMT, identified by de novo expression of α-smooth muscle actin and a loss of E-cadherin in human peritoneal mesothelial cells (HPMCs), was associated with downregulation of miR-200a but upregulation of zinc finger E-box-binding homeobox 1/2 (ZEB1/2), suggesting a close link between miR-200a and ZEB1/2 in TGF-β1-induced EMT. It was further demonstrated that miR-200a was able to bind to the 3'UTR of ZEB1/2, and overexpression of miR-200a blocked TGF-β1-induced upregulation of ZEB1/2 and, therefore, inhibited EMT and collagen expression. In contrast, overexpression ZEB1/2 blocked miR-200a inhibition of EMT and collagen expression in HMPCs. In conclusion, miR-200a could negatively regulate TGF-β1-induced EMT by targeting ZEB1/2 in peritoneal mesothelial cells. Blockade of EMT in HPMCS indicates the therapeutic potential of miR-200a as a treatment for peritoneal fibrosis associated with PD.

Biologically active form of vitamin B1 in human peritoneal effluent.

Supplementation with vitamin B1 protects the peritoneal membrane from inflammatory and oxidative insults and preserves residual kidney function in rat models of peritoneal dialysis (PD). It is assumed that an active form of vitamin B1, thiamin diphosphate (ThDP), is responsible for this protective effect. However, it has never been shown whether ThDP, a compound known not to cross cellular membranes, is actually detectable in human peritoneal effluent. This study was designed to investigate the concentration, appearance rate, and daily loss of ThDP in the peritoneal effluent of patients treated with PD. We performed 24-hour effluent collection as well as the peritoneal equilibration test (PET) and analyzed the relation between the transport characteristics of the peritoneal membrane and appearance rate of ThDP in a cohort of 26 PD patients. ThDP was detectable in peritoneal effluent in humans. ThDP appearance rate was independent of the transport characteristic of peritoneal membrane, and was not associated with peritoneal transport of other small solutes. We conclude that ThDP can be found in detectable concentrations in the peritoneal effluent in humans and is transported through the peritoneal membrane in a pattern independent of other small solutes. Our finding opens novel opportunities in further research on the protection of peritoneal membrane in humans.

Effects of RNA interference-mediated gene silencing of VEGF on the ultrafiltration failure in a rat model of peritoneal dialysis

We investigated the effects of RNAi-mediated gene silencing of vascular endothelial growth factor (VEGF) on ultrafiltration failure (UFF) in rats with peritoneal dialysis (PD). Sprague–Dawley (SD) male rats were classified into normal, sham operation, and uremic model groups. Uremic rats were subcategorized into uremia, PD2, VEGF shRNA-2, vector-2, PD2 + Endostar, PD4, VEGF shRNA-4, Vector-4, and PD4 + Endostar groups. Peritoneal Equilibration Test (PET) was conducted to assess ultrafiltration volume (UFV) and mass transfer of glucose (MTG). mRNA and protein expressions of VEGF were detected using quantitative real-time PCR (qRT-PCR) and Western blotting. Immunohistochemistry was performed to detect microvessel density (MVD). Compared with the normal group, decreased UFV and increased MTG were observed in rest of the groups. Compared with the uremia group, UFV decreased, while MTG, expression of VEGFs, and number of new blood capillaries increased in the PD2, Vector-2, PD4, and Vector-4 groups. The PD4 and Vector-4 groups exhibited lower UFV and higher MTG than the PD2 group. In the VEGF shRNA-2, PD2 + Endostar, VEGF shRNA-4, and in PD4 + Endostar group increased UFV, reduced MTG and expression of VEGF, and decreased number of new blood capillaries were detected. Compared with the PD4 group, in the VEGF shRNA-4 and PD4 + Endostar groups, UFV increased, MTG and expression of VEGF decreased, and number of new blood capillaries reduced. VEGF expression was negatively correlated with UFV, but positively correlated with MTG. The results obtained in the study revealed that down-regulation of VEGF by RNAi could be a novel target approach for the treatment of UFF.

Pharmacological inhibition of heparin-binding EGF-like growth factor promotes peritoneal angiogenesis in a peritoneal dialysis rat model.

Molecular mechanisms of peritoneal dialysis (PD) ultrafiltration failure, peritoneal neo-angiogenesis, and fibrosis remain to be determined. We aimed to determine the role of heparin-binding EGF-like growth factor (HB-EGF) inhibition on angiogenesis of peritoneal membrane in a PD rat model. 32 male Wistar rats were assigned into (1) control group; (2) uremic non-PD group: subtotal nephrectomy-induced uremic rats without PD; (3) uremic rats subjected to PD: uremic rats that were dialyzed with Dianeal® for 4weeks; (4) CRM 197 group: dialyzed uremic rats were supplemented with CRM197, a specific HB-EGF inhibitor. Peritoneal transport function was examined by peritoneal equilibration test. Expression of HB-EGF and EGFR in peritoneal samples were examined by real-time PCR, immunohistochemical staining, and western blot. Progressive angiogenesis and fibrosis were observed in uremic PD rats, and there were associated with decreased net ultrafiltration (nUF), increased permeability of peritoneal membrane, and reduced expression of HB-EGF and EGFR protein and mRNA in uremic PD rats compared to uremic non-PD or control groups (both p<0.05). CRM197 significantly induced peritoneal membrane permeability, decreased nUF, increased higher vessel density, and reduced pericyte count compared to that of uremic PD rats. The levels of HB-EGF and EGFR expression negatively correlated with vessel density in peritoneal membrane (both p<0.001). PD therapy was associated with peritoneal angiogenesis, functional deterioration, and downregulation of HB-EGF/EGFR. Pharmacological inhibition of HB-EGF promoted PD-induced peritoneal angiogenesis and fibrosis and ultrafiltration decline, suggesting that HB-EGF downregulation contributes to peritoneal functional deterioration in the uremic PD rat model.

The MicroRNA-199a/214 Cluster Targets E-Cadherin and Claudin-2 and Promotes High Glucose-Induced Peritoneal Fibrosis.

Serum response factor (SRF) was found to be involved in the phenotypic transition and fibrosis of the peritoneal membrane during treatment with peritoneal dialysis (PD), but the exact mechanism remains unclear. SRF regulates microRNAs (miRNAs) that contain the SRF-binding consensus (CArG) element in the promoter region. Therefore, we investigated whether the miR-199a/214 gene cluster, which contains a CArG element in its promoter, is directly regulated by SRF. High-glucose (HG) treatment significantly unregulated the expression of the miR-199a-5p/214-3p gene cluster in human peritoneal mesothelial cells (HPMCs). By chromatin immunoprecipitation and reporter assays, we found that SRF binds to the miR-199a-5p/214-3p gene cluster promoter after HG stimulation. In vitro, in HPMCs, silencing of miR-199a-5p or miR-214-3p inhibited the HG-induced phenotypic transition and cell migration but enhanced cell adhesion, whereas ectopic expression of mimic oligonucleotides had the opposite effects. Both miR-199a-5p and miR-214-3p targeted claudin-2 and E-cadherin mRNAs. In a PD rat model, treatment with an SRF inhibitor silenced miR-199a-5p and miR-214-3p and alleviated HG-PD fluid-induced damage and fibrosis. Overall, this study reveals a novel SRF-miR-199a/miR-214-E-cadherin/claudin-2 axis that mediates damage and fibrosis in PD.

Erythrocytes as Volume Markers in Experimental PD Show that Albumin Transport in the Extracellular Space Depends on PD Fluid Osmolarity.

♦ Macromolecules, when used as intraperitoneal volume markers, have the disadvantage of leaking into the surrounding tissue. Therefore, (51)Cr-labeled erythrocytes were evaluated as markers of intraperitoneal volume and used in combination with (125)I-labeled bovine serum albumin to study albumin transport into peritoneal tissues in a rat model of peritoneal dialysis (PD). ♦ Single dwells of 20 mL of lactate-buffered filter-sterilized PD fluid at glucose concentrations of 0.5%, 2.5%, and 3.9% were performed for 1 or 4 hours. Tissue biopsies from abdominal muscle, diaphragm, liver, and intestine, and blood and dialysate samples, were analyzed for radioactivity. ♦ The dialysate distribution volume of labeled erythrocytes, measured after correction for lymphatic clearance to blood, was strongly correlated with, but constantly 3.3 mL larger than, drained volumes. Erythrocyte activity of rinsed peritoneal tissue biopsies corresponded to only 1 mL of dialysate, supporting our utilization of erythrocytes as markers of intraperitoneal volume. The difference between the distribution volumes of albumin and erythrocytes was analyzed to represent the albumin loss into the peritoneal tissues, which increased rapidly during the first few minutes of the dwell and then leveled out at 2.5 mL. It resumed when osmotic ultrafiltration turned into reabsorption and, at the end of the dwell, it was significantly lower for the highest osmolarity PD fluid (3.9% glucose). Biopsy data showed the lowest albumin accumulation and edema formation in abdominal muscle for the 3.9% fluid. ♦ Labeled erythrocytes are acceptable markers of intraperitoneal volume and, combined with labeled albumin, provided novel kinetic data on albumin transport in peritoneal tissues.