Hyperbranched polyglycerol is an efficacious and biocompatible novel osmotic agent in a rodent model of peritoneal dialysis

Controlled Synthesis of Dendrite-like Polyglycerols Using Aluminum Complex for Biomedical Applications

This work describes a one-pot synthesis of dendrite-like hyperbranched polyglycerols (HPGs) via a ring-opening multibranching polymerization (ROMBP) process using a bis(5,7-dichloro-2-methyl-8-quinolinolato)methyl aluminum complex (1) as a catalyst and 1,1,1-tris(hydroxymethyl)propane/trimethylol propane (TMP) as an initiator. Single-crystal X-ray diffraction (XRD) analysis was used to elucidate the molecular structure of complex 1. Inverse-gated (IG)¹³C NMR analysis of HPGs showed degree of branching between 0.50 and 0.57. Gel permeation chromatography (GPC) analysis of the HPG polymers provided low, medium, and high-molecular weight (M _n) polymers ranging from 14 to 73 kDa and molecular weight distributions (M _w/M _n) between 1.16 and 1.35. The obtained HPGs exhibited high wettability with water contact angle between 18 and 21° and T _g ranging between -39 and -55 °C. Notably, ancillary ligand-supported aluminum complexes as catalysts for HPG polymerization reactions have not been reported to date. The obtained HPG polymers in the presence of the aluminum complex (1) can be used for various biomedical applications. Here, nanocomposite electrospun fibers were fabricated with synthesized HPG polymer. The nanofibers were subjected to cell culture experiments to evaluate cytocompatibility behavior with L929 and MG63 cells. The cytocompatibility studies of HPG polymer and nanocomposite scaffold showed high cell viability and spreading. The study results concluded, synthesized HPG polymers and composite nanofibers can be used for various biomedical applications.

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

Background

A 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.

Methods

5/6 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.

Results

We 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.

Conclusions

As 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.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02473-9.

Removal of Protein-Bound Uremic Toxins by Liposome-Supported Peritoneal Dialysis

Background:Protein-bound uremic toxins (PBUTs) are poorly cleared by peritoneal dialysis (PD). This study aimed to enhance PBUT removal in PD by adding a binder to the peritoneal dialysate and to evaluate the feasibility and efficacy of liposome-supported PD (LSPD) to increase the removal of PBUTs compared with albumin PD.Methods:Removal of p-cresyl sulfate (PCS), indoxyl sulfate (IS), and indole-3-acetic acid (3-IAA) was first evaluated in an in vitro PD model using artificial plasma preloaded with test solutes. Male Sprague-Dawley rats (n = 24) were then subjected to 5/6 nephrectomy and fed for 16 weeks to establish end-stage renal failure, after which they were treated with either conventional glucose-based PD, albumin-based PD, or liposome-based PD. Removal of PBUTs and small water-soluble solutes was determined during a 6-hour PD dwell.Results:In vitro experiments showed that adding albumin as a toxin binder to the dialysate markedly increased the removal of PCS, IS, and 3-IAA compared with the control. The uptake capacity of liposomes was comparable with that of albumin for PCS and 3-IAA, though slightly inferior for IS. In vivo PD in uremic rats demonstrated that LSPD resulted in higher intraperitoneal concentrations and more total mass removal for PBUTs than the conventional glucose-based PD, which was comparable with albumin PD.Conclusions:Supplementing conventional glucose-based PD solutions with a binder could efficiently increase the removal of PBUTs. This preliminary study suggested that LSPD may be a promising alternative to albumin PD for increasing PBUT removal in the development of next-generation PD solutions for PD patients.

The osmo-metabolic approach: a novel and tantalizing glucose-sparing strategy in peritoneal dialysis

Peritoneal dialysis (PD) is a viable but under-prescribed treatment for uremic patients. Concerns about its use include the bio-incompatibility of PD fluids, due to their potential for altering the functional and anatomical integrity of the peritoneal membrane. Many of these effects are thought to be due to the high glucose content of these solutions, with attendant issues of products generated during heat treatment of glucose-containing solutions. Moreover, excessive intraperitoneal absorption of glucose from the dialysate has many potential systemic metabolic effects. This article reviews the efforts to develop alternative PD solutions that obviate some of these side effects, through the replacement of part of their glucose content with other osmolytes which are at least as efficient in removing fluids as glucose, but less impactful on patient metabolism. In particular, we will summarize clinical studies on the use of alternative osmotic ingredients that are commercially available (icodextrin and amino acids) and preclinical studies on alternative solutions under development (taurine, polyglycerol, carnitine and xylitol). In addition to the expected benefit of a glucose-sparing approach, we describe an ‘osmo-metabolic’ approach in formulating novel PD solutions, in which there is the possibility of exploiting the pharmaco-metabolic properties of some of the osmolytes to attenuate the systemic side effects due to glucose. This approach has the potential to ameliorate pre-existing co-morbidities, including insulin resistance and type-2 diabetes, which have a high prevalence in the dialysis population, including in PD patients.

Sodium toxicity in peritoneal dialysis: mechanisms and "solutions"

The major trials in peritoneal dialysis (PD) have demonstrated that increasing peritoneal clearance of small solutes is not associated with any advantage on survival, whereas sodium and fluid overload heralds higher risk of death and technique failure. On the other hand, higher sodium and fluid overload due to loss of residual kidney function (RKF) and higher transport membrane is associated with poor patient and technique survival. Recent experimental studies also show that, independently from fluid overload, sodium accumulation in the peritoneal interstitium exerts direct inflammatory and angiogenetic stimuli, with consequent structural and functional changes of peritoneum, while in patients with Chronic Kidney Disease sodium stored in interstitial skin acts as independent determinant of left ventricular hypertrophy. Noteworthy, this tissue pool of sodium is modifiable being removed by dialysis. Therefore, novel PD strategies to optimize sodium removal, including the use of bimodal and/or low-sodium solutions, are actively tested. Nonetheless, a holistic approach aimed at preserving peritoneal function and the kidney may represent the key of therapy success in the hard task of preserving adequate sodium balance in PD patients. In this review, we describe the available evidence on sodium toxicity in PD, either related or unrelated to fluid overload, and we also discuss about possible "solutions" to preserve or restore sodium balance in PD patients.

Protection of the Peritoneal Membrane by Peritoneal Dialysis Effluent-Derived Mesenchymal Stromal Cells in a Rat Model of Chronic Peritoneal Dialysis

Peritoneal dialysis (PD) is a renal replacement option for patients with end-stage renal disease. However, a long-term exposure to hypertonic PD solutions leads to peritoneal membrane (PM) injury, resulting in ultrafiltration (UF) failure. This study was designed to primarily evaluate efficacy of PD effluent-derived mesenchymal stromal cells (pMSCs) in the prevention of PM injury in rats. The pMSCs were isolated from PD effluent. Male Wistar rats received daily intraperitoneal (IP) injection of 10 mL of Dianeal (4.25% dextrose) and were treated with pMSCs (1.2‐1.5 × 10⁶/rat/wk, IP). UF was determined by IP injection of 30 mL of Dianeal (4.25% dextrose) with dwell time of 1.5 h, and PM injury was examined by histology. Apoptosis was quantitated by using flow cytometric analysis, and gene expression by using the PCR array and Western blot. Here, we showed that as compared to naive control, daily IP injection of the Dianeal PD solution for 6 weeks without pMSC treatment significantly reduced UF, which was associated with an increase in both PM thickness and blood vessel, while pMSC treatment prevented the UF loss and reduced PM injury and blood vessels. In vitro incubation with pMSC-conditioned medium prevented cell death in cultured human peritoneal mesothelial cells (HPMCs) and downregulated proinflammatory (i.e., CXCL6, NOS2, IL1RN, CCL5, and NR3C1) while upregulated anti-inflammatory (i.e., CCR1, CCR4, IL9, and IL-10) gene expression in activated THP1 cells. In conclusion, pMSCs prevent bioincompatible PD solution-induced PM injury and UF decline, suggesting that infusing back ex vivo-expanded pMSCs intraperitoneally may have therapeutic potential for reduction of UF failure in PD patients.

Transcriptome analysis of signaling pathways of human peritoneal mesothelial cells in response to different osmotic agents in a peritoneal dialysis solution

Background

Glucose is a primary osmotic agent in peritoneal dialysis (PD) solutions, but its long-term use causes structural alteration of the peritoneal membrane (PM). Hyperbranched polyglycerol (HPG) is a promising alternative to glucose. This study was designed to compare the cellular responses of human peritoneal mesothelial cells (HPMCs) to these two different osmotic agents in a hypertonic solution using transcriptome analysis.

Methods

Cultured HPMCs were repeatedly exposed to HPG-based or Physioneal 40 (PYS, glucose 2.27%) hypertonic solutions. Transcriptome datasets were produced using Agilent SurePrint G3 Human GE 8 × 60 microarray. Cellular signaling pathways were examined by Ingenuity Pathway Analysis (IPA). Protein expression was examined by flow cytometry analysis and Western blotting.

Results

The HPG-containing solution was better tolerated compared with PYS, with less cell death and disruption of cell transcriptome. The levels of cell death in HPG- or PYS- exposed cells were positively correlated with the number of affected transcripts (HPG: 128 at day 3, 0 at day 7; PYS: 1799 at day 3, 212 at day 7). In addition to more affected “biosynthesis” and “cellular stress and death” pathways by PYS, both HPG and PYS commonly affected “sulfate biosynthesis”, “unfolded protein response”, “apoptosis signaling” and “NRF2-mediated oxidative stress response” pathways at day 3. PYS significantly up-regulated HLA-DMB and MMP12 in a time-dependent manner, and stimulated T cell adhesion to HPMCs.

Conclusion

The lower cytotoxicity of hypertonic HPG solution is in agreement with its transient and minimal impact on the pathways for the “biosynthesis of cell constituents” and the “cellular stress and death”. The significant up-regulation of HLA-DMB and MMP12 by PYS may be part of its initiation of immune response in the PM.

Biocompatible Peritoneal Dialysis: The Target Is Still Way Off

Peritoneal dialysis (PD) is a cost-effective, home-based therapy for patients with end-stage renal disease achieving similar outcome as compared to hemodialysis. Still, a minority of patients only receive PD. To a significant extend, this discrepancy is explained by major limitations regarding PD efficiency and sustainability. Due to highly unphysiological composition of PD fluids, the peritoneal membrane undergoes rapid morphological and long-term functional alterations, which limit the treatment and contribute to adverse patient outcome. This review is focused on the peritoneal membrane ultrastructure and its transformation in patients with kidney disease and chronic PD, underlying molecular mechanisms, and potential systemic sequelae. Current knowledge on the impact of conventional and second-generation PD fluids is described; novel strategies and innovative PD fluid types are discussed.

Peritoneal and Systemic Responses of Obese Type II Diabetic Rats to Chronic Exposure to a Hyperbranched Polyglycerol-Based Dialysis Solution

Metabolic syndrome (MetS) is commonly observed among peritoneal dialysis (PD) patients, and hyperbranched polyglycerol (HPG) is a promising glucose-sparing osmotic agent for PD. However, the biocompatibility of a HPG-based PD solution (HPG) in subjects with MetS has not been investigated. This study compared the local and systemic effects of a HPG solution with conventional physioneal (PYS) and icodextrin (ICO) PD solutions in rats with MetS. Obese type 2 diabetic ZSF1 rats received a daily intraperitoneal injection of PD solutions (10 mL) for 3 months. The peritoneal membrane (PM) function was determined by ultrafiltration (UF), and the systemic responses were determined by profiling blood metabolic substances, cytokines and oxidative status. Tissue damage was assessed by histology. At the end of the 3-month treatment with PD solutions, PM damage and UF loss in both the PYS and ICO groups were greater than those in the HPG group. Blood analyses showed that compared to the baseline control, the rats in the HPG group exhibited a significant decrease only in serum albumin and IL-6 and a minor glomerular injury, whereas in both the PYS and ICO groups, there were more significant decreases in serum albumin, antioxidant activity, IL-6, KC/GRO (CXCL1) and TNF-α (in ICO only) as well as a more substantial glomerular injury compared to the HPG group. Furthermore, PYS increased serum creatinine, serum glucose and urine production. In conclusion, compared to PYS or ICO solutions, the HPG solution had less adverse effects locally on the PM and systemically on distant organs (e.g. kidneys) and the plasma oxidative status in rats with MetS.

Oncotically Driven Control over Glycocalyx Dimension for Cell Surface Engineering and Protein Binding in the Longitudinal Direction

Here we present a simple technique for re-directing reactions on the cell surface to the outermost region of the glycocalyx. Macromolecular crowding with inert polymers was utilized to reversibly alter the accessibility of glycocalyx proteoglycans toward cell-surface reactive probes allowing for reactivity control in the longitudinal direction (‘z’-direction) on the glycocalyx. Studies in HUVECs demonstrated an oncotically driven collapse of the glycocalyx brush structure in the presence of crowders as the mechanism responsible for re-directing reactivity. This phenomenon is consistent across a variety of macromolecular agents including polymers, protein markers and antibodies which all displayed enhanced binding to the outermost surface of multiple cell types. We then demonstrated the biological significance of the technique by increasing the camouflage of red blood cell surface antigens via a crowding-enhanced attachment of voluminous polymers to the exterior of the glycocalyx. The accessibility to Rhesus D (R_hD) and CD47 proteins on the cell surface was significantly decreased in crowding-assisted polymer grafting in comparison to non-crowded conditions. This strategy is expected to generate new tools for controlled glycocalyx engineering, probing the glycocalyx structure and function, and improving the development of cell based therapies.

Visions in a Crystal Ball: The Future of Peritoneal Dialysis

BACKGROUND

Peritoneal dialysis (PD) is one of the corner stones of renal replacement therapy and should be strongly considered if preemptive kidney transplantation is not available.

SUMMARY

There are several initiatives that may help the growth in the use of PD around the world. First, PD is an underused and valuable option in patients with heart failure and the chronic cardiorenal syndrome, especially in those with frequent hospitalizations despite optimal medical therapy. To identify these patients, an interdisciplinary approach of nephrologists and cardiologists is needed. These patients and other CKD patients with significant residual kidney function may do well with a regimen employing fewer than the usual number of bag exchanges, referred to as "incremental" dialysis. Second, acute kidney injury (AKI) is a worldwide burden with high morbidity and mortality, especially in low income countries. To reach the goal of zero preventable deaths caused by AKI by 2025 endorsed by the International Society of Nephrology, PD is the therapy of choice for treatment in this setting. Third, although dextrose has served well as the osmotic agent in PD solutions, there has been a continuous search for alternative agents. Hyperbranched polyglycerol might be such an osmole. Finally, to obviate the need for production and delivery of bags of PD solution, the development of home-generated dialysate is of interest. Key Message: The future of PD lies not only in accruing experience from the past decades, but also in staying open to other uses.

"Biocompatible" Neutral pH Low-GDP Peritoneal Dialysis Solutions: Much Ado About Nothing?

Adverse outcomes in peritoneal dialysis (PD), including PD related infections, the loss of residual kidney function (RKF), and longitudinal, deleterious changes in peritoneal membrane function continue to limit the long-term success of PD therapy. The observation that these deleterious changes occur upon exposure to conventional glucose-based PD solutions fuels the search for a more biocompatible PD solution. The development of a novel PD solution with a neutral pH, and lower in glucose degradation products (GDPs) compared to its conventional predecessors has been labeled a "biocompatible" solution. While considerable evidence in support of these novel solutions' biocompatibility has emerged from cell culture and animal studies, the clinical benefits as compared to conventional PD solutions are less clear. Neutral pH low GDP (NpHLGDP) PD solutions appear to be effective in reducing infusion pain, but their effects on other clinical endpoints including peritoneal membrane function, preservation of RKF, PD-related infections, and technique and patient survival are less clear. The literature is limited by studies characterized by relatively few patients, short follow-up time, heterogeneity with regards to the novel PD solution type under study, and the different patient populations under study. Nonetheless, the search for a more biocompatible PD solution continues with emerging data on promising non glucose-based solutions.

Direct Macromolecular Drug Delivery to Cerebral Ischemia Area using Neutrophil-Mediated Nanoparticles

Delivery of macromolecular drugs to the brain is impeded by the blood brain barrier. The recruitment of leukocytes to lesions in the brain, a typical feature of neuroinflammation response which occurs in cerebral ischemia, offers a unique opportunity to deliver drugs to inflammation sites in the brain. In the present study, cross-linked dendrigraft poly-L-lysine (DGL) nanoparticles containing cis-aconitic anhydride-modified catalase and modified with PGP, an endogenous tripeptide that acts as a ligand with high affinity to neutrophils, were developed to form the cl PGP-PEG-DGL/CAT-Aco system. Significant binding efficiency to neutrophils, efficient protection of catalase enzymatic activity from degradation and effective transport to receiver cells were revealed in the delivery system. Delivery of catalase to ischemic subregions and cerebral neurocytes in MCAO mice was significantly enhanced, which obviously reducing infarct volume in MCAO mice. Thus, the therapeutic outcome of cerebral ischemia was greatly improved. The underlying mechanism was found to be related to the inhibition of ROS-mediated apoptosis. Considering that neuroinflammation occurs in many neurological disorders, the strategy developed here is not only promising for treatment of cerebral ischemia but also an effective approach for various CNS diseases related to inflammation.

Cold preservation with hyperbranched polyglycerol-based solution improves kidney functional recovery with less injury at reperfusion in rats

Minimizing donor organ injury during cold preservation (including cold perfusion and storage) is the first step to prevent transplant failure. We recently reported the advantages of hyperbranched polyglycerol (HPG) as a novel substitute for hydroxyethyl starch in UW solution for both cold heart preservation and cold kidney perfusion. This study evaluated the functional recovery of the kidney at reperfusion after cold preservation with HPG solution. The impact of HPG solution compared to conventional UW and HTK solutions on tissue weight and cell survival at 4°C was examined using rat kidney tissues and cultured human umbilical vein endothelial cells (HUVECs), respectively. The kidney protection by HPG solution was tested in a rat model of cold kidney ischemia-reperfusion injury, and was evaluated by histology and kidney function. Here, we showed that preservation with HPG solution prevented cell death in cultured HUVECs and edema formation in kidney tissues at 4°C similar to UW solution, whereas HTK solution was less effective. In rat model of cold ischemia-reperfusion injury, the kidneys perfused and subsequently stored 1-hour with cold HPG solution showed less leukocyte infiltration, less tubular damage and better kidney function (lower levels of serum creatinine and blood urea nitrogen) at 48 h of reperfusion than those treated with UW or HTK solution. In conclusion, our data show the superiority of HPG solution to UW or HTK solution in the cold perfusion and storage of rat kidneys, suggesting that the HPG solution may be a promising candidate for improved donor kidney preservation prior to transplantation.

Hyperbranched polyglycerols: recent advances in synthesis, biocompatibility and biomedical applications

Hyperbranched polyglycerol is one of the most widely studied biocompatible dendritic polymer and showed promising applications. Here, we summarized the recent advancements in the field.

Is there such a thing as biocompatible peritoneal dialysis fluid?

Introduction of the so-called biocompatible peritoneal dialysis (PD) fluids was based on a large body of experimental evidence and various clinical trials suggesting important clinical benefits. Of these, until now, only preservation of residual renal function-likely due to lower glucose degradation product load and, in case of icodextrin, improved fluid and blood pressure control-have consistently been proven, whereas the impact on important clinical endpoints such as infectious complications, preservation of PD membrane transport function, and patient outcome, are still debated. In view of the high morbidity and mortality rates of PD patients, novel approaches are warranted and comprise the search for alternative osmotic agents and enrichment of PD fluids with specific pharmacologic agents, such as alanyl-glutamine, potentially counteracting local but also systemic sequelae of uremia and PD.

Hyperbranched polyglycerol is superior to glucose for long-term preservation of peritoneal membrane in a rat model of chronic peritoneal dialysis

Background

Replacing glucose with a better biocompatible osmotic agent in peritoneal dialysis (PD) solutions is needed in PD clinic. We previously demonstrated the potential of hyperbranched polyglycerol (HPG) as a replacement for glucose. This study further investigated the long-term effects of chronic exposure to HPG as compared to a glucose-based conventional PD solution on peritoneal membrane (PM) structure and function in rats.

Methods

Adult male Wistar rats received once-daily intraperitoneal injection of 10 mL of HPG solution (1 kDa, HPG 6%) compared to Physioneal™ 40 (PYS, glucose 2.27%) or electrolyte solution (Control) for 3 months. The overall health conditions were determined by blood chemistry analysis. The PM function was determined by ultrafiltration, and its injury by histological and transcriptome-based pathway analyses.

Results

Here, we showed that there was no difference in the blood chemistry between rats receiving the HPG and the Control, while PYS increased serum alkaline phosphatase, globulin and creatinine and decreased serum albumin. Unlike PYS, HPG did not significantly attenuate PM function, which was associated with smaller change in both the structure and the angiogenesis of the PM and less cells expressing vascular endothelial growth factor, α-smooth muscle actin and MAC387 (macrophage marker). The pathway analysis revealed that there were more inflammatory signaling pathways functioning in the PM of PYS group than those of HPG or Control, which included the signaling for cytokine production in both macrophages and T cells, interleukin (IL)-6, IL-10, Toll-like receptors, triggering receptor expressed on myeloid cells 1 and high mobility group box 1.

Conclusions

The results from this experimental study indicate the superiority of HPG to glucose in the preservation of the peritoneum function and structure during the long-term PD treatment, suggesting the potential of HPG as a novel osmotic agent for PD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-1098-z) contains supplementary material, which is available to authorized users.

Advantages of replacing hydroxyethyl starch in University of Wisconsin solution with hyperbranched polyglycerol for cold kidney perfusion

BACKGROUND

Efficient and effective perfusion during organ procurement is required for the best prevention of donor organ injury preceding transplantation. However, current organ preservation solutions, including hydroxyethyl starch (HES)-based University of Wisconsin (UW) solution, do not always yield the best outcomes. Our previous study demonstrated that replacing HES with hyperbranched polyglycerol (HPG) reduced donor heart injury during cold storage. The current research was designed to examine the advantages of HPG-based solution for cold kidney perfusion.

METHODS

Perfusion efficiency of HPG versus UW solution was tested using mouse kidneys at 4°C. The blood washout was evaluated by using a semiquantitative scoring system and tissue damage by histologic analysis. The interaction of HPG or UW solution with human red blood cells (RBCs) was examined by measuring RBC sedimentation and aggregation.

RESULTS

The lower viscosity of HPG solution was correlated with faster and more efficient perfusion through donor kidneys as compared with UW. HPG solution was also more effective than UW in removing RBCs from the kidney and was associated with less tissue damage to donor kidneys. In vitro UW solution caused significant RBC sedimentation and hyperaggregation, whereas HPG showed minimal impact on RBC sedimentation and prevented RBC aggregation.

CONCLUSIONS

This experimental study demonstrated that compared with UW, HPG solution was more efficient and effective in the removal of the blood from donor kidneys and offered better protection from donor tissue damage, suggesting that the HPG solution is a promising candidate to supplant standard UW solution for donor kidney perfusion in transplantation.

A toolset of functionalized porphyrins with different linker strategies for application in bioconjugation

Polar, functionalized A₃B-porphyrins are conjugated to hyperbranched polyglycerol (hPG) as an example of a biocompatible carrier system for photodynamic therapy.

Hyperbranched polyglycerol as a colloid in cold organ preservation solutions

Hydroxyethyl starch (HES) is a common colloid in organ preservation solutions, such as in University of Wisconsin (UW) solution, for preventing graft interstitial edema and cell swelling during cold preservation of donor organs. However, HES has undesirable characteristics, such as high viscosity, causing kidney injury and aggregation of erythrocytes. Hyperbranched polyglycerol (HPG) is a branched compact polymer that has low intrinsic viscosity. This study investigated HPG (MW-0.5 to 119 kDa) as a potential alternative to HES for cold organ preservation. HPG was synthesized by ring-opening multibranching polymerization of glycidol. Both rat myocardiocytes and human endothelial cells were used as an in vitro model, and heart transplantation in mice as an in vivo model. Tissue damage or cell death was determined by both biochemical and histological analysis. HPG polymers were more compact with relatively low polydispersity index than HES in UW solution. Cold preservation of mouse hearts ex vivo in HPG solutions reduced organ damage in comparison to those in HES-based UW solution. Both size and concentration of HPGs contributed to the protection of the donor organs; 1 kDa HPG at 3 wt% solution was superior to HES-based UW solution and other HPGs. Heart transplants preserved with HPG solution (1 kDa, 3%) as compared with those with UW solution had a better functional recovery, less tissue injury and neutrophil infiltration in syngeneic recipients, and survived longer in allogeneic recipients. In cultured myocardiocytes or endothelial cells, significantly more cells survived after cold preservation with the HPG solution than those with the UW solution, which was positively correlated with the maintenance of intracellular adenosine triphosphate and cell membrane fluidity. In conclusion, HPG solution significantly enhanced the protection of hearts or cells during cold storage, suggesting that HPG is a promising colloid for the cold storage of donor organs and cells in transplantation.

A review of rodent models of peritoneal dialysis and its complications

This article reviews the available rodent models of peritoneal dialysis (PD) that have been developed over the past 20 years and the complications associated with their use. Although there are several methods used in different studies, the focus of this article is not to review or provide detailed summaries of these methods. Rather, this article reviews the most common methods of establishing a dialysis model in rodents, the assays used to observe function of the peritoneum in dialysis, and how these models are adapted to study peritonitis and peritoneal fibrosis. We compared the advantages and disadvantages of different methods, which should be helpful in studies of PD and may provide valuable data for further clinical studies.

Alterations of intercellular junctions in peritoneal mesothelial cells from patients undergoing dialysis: effect of retinoic Acid

BACKGROUND

Dialysis patients are classified according to their peritoneal permeability as low transporter (LT, low solute permeability) or high transporter (HT, high solute permeability). Tight junction (TJ) proteins are critical to maintain ions, molecules and water paracellular transport through peritoneum. Exposure to peritoneal dialysis solutions causes damage to TJ in human peritoneal mesothelial cells (HPMCs). We analyzed the quantity, distribution and function of TJ proteins: claudin-1, -2 and -8, ZO-1 and occludin, in HPMC cultures from LT and HT patients. Since all-trans retinoic acid (ATRA) might modify the expression of TJ proteins, we studied its effect on HPMCs.

METHODS

Control HPMCs were isolated from human omentum, while HT or LT cells were obtained from dialysis effluents. Cells were cultured in presence of ATRA 0, 50 or 100 nM. Transepithelial electrical resistance (TER) measurement, immunostaining and Western blot analyses were performed.

RESULTS

HT exhibited lower TER than control and LT monolayers. Immunofluorescence for TJ was weak and discontinuous along the cell contour, in LT and HT. Furthermore, claudin-1, occludin and ZO-1 expressions were decreased. In all groups, claudin-2 was localized at nuclei. We observed that ATRA improved TJ distribution and increased TJ expression in HT. This retinoid did not modify claudin-2 and -8 expressions. All-trans retinoic acid decreased TER in HT, but had no effect in LT.

CONCLUSIONS

Tight junctions were altered in HPMCs from dialyzed patients. The HT monolayer has lower TER than LT, which might be associated with the peritoneal permeability in these patients. ATRA might be a therapeutic alternative to maintain mesothelial integrity, since it improved TJ localization and expression.