A chronic intermittent haemodialysis pig model for functional evaluation of dialysis membranes

Performance evaluation of new dialysis membranes is primarily performed in vitro, which can lead to differences in clinical results. Currently, data on dialysis membrane performance and safety are available only for haemodialysis patients. Herein, we aimed to establish an in vivo animal model of dialysis that could be extrapolated to humans. We created a bilateral nephrectomy pig model of renal failure, which placed a double-lumen catheter with the hub exposed dorsally. Haemodialysis was performed in the same manner as in humans, during which clinically relevant physiologic data were evaluated. Next, to evaluate the utility of this model, the biocompatibility of two kinds of membranes coated with or without vitamin E used in haemodiafiltration therapy were compared. Haemodialysis treatment was successfully performed in nephrectomized pigs under the same dialysis conditions (4 h per session, every other day, for 2 weeks). In accordance with human clinical data, regular dialysis alleviated renal failure in pigs. The vitamin E-coated membrane showed a significant reduction rate of advanced oxidation protein products during dialysis than non-coated membrane. In conclusion, this model mimics the pathophysiology and dialysis condition of patients undergoing haemodialysis. This dialysis treatment model of renal failure will be useful for evaluating the performance and safety of dialysis membranes.

Clotting Propensity of Surface-Treated Membranes in a Hemodialysis Set-up That Avoids Systemic Anticoagulation

The development of biocompatible membranes, aiming to limit the inflammatory response, oxidative stress, and coagulability during hemodialysis, has been an important step in reducing dialysis-related adverse outcomes. This includes a reduction in the risk of clotting of the extracorporeal circuit, thus enabling hemodialysis with a reduced dose or even without systemic anticoagulant drugs in patients with an increased bleeding risk. In this article, we summarize the in vitro research and clinical evidence on the antithrombotic properties of vitamin E- and heparin-coated membranes.

The effect of vitamin E-bonded polysulfone membrane dialyzer on a new oxidative lipid marker

The use of vitamin E-bonded cellulose membrane dialyzers has been reported to cause a decrease in oxidative lipid marker levels (Nakai et al., Ther Apher Dial 14:505-540, 1; Nakai et al., J Jpn Soc Dial Ther 45:1-47, 2; Mashiba et al., Arterioscler Thromb Vasc Biol 21:1801-1808, 3). However, few studies have identified this effect with vitamin E-bonded polysulfone membranes, and no studies report the same effect on alpha (1) antitrypsin-LDL complex, a new oxidative lipid marker. This prompted us to examine the influence of use of VPS-HA vitamin E-bonded polysulfone high-flux membrane dialyzers on this new oxidative lipid marker. The subjects were 17 patients who had been dialyzed with VPS-HA for 12 months. The subjects' baseline characteristics were as follows. Their average age was 65.6 ± 13.1 years, comprising 8 males and 9 females; hemodialysis vintage was 83.8 ± 85.4 months. Eight had chronic glomerular nephropathy and five had diabetic nephropathy. The primary outcome was defined as alpha (1) antitrypsin-LDL complex level after 12 months, as a post-study using VPS-HA. Secondary outcomes included triglycerides, total cholesterol, HDL cholesterol and LDL cholesterol levels. The data were analyzed pre-study and after 3, 6, 9 and 12 months for alpha (1) antitrypsin-LDL complex, and pre-study and post-study for the other indicators. Twelve months after switching to VPS-HA, alpha (1) antitrypsin-LDL complex, total cholesterol and LDL cholesterol had significantly decreased. Triglycerides and HDL cholesterol had not significantly changed. Hemodialysis therapy with VPS-HA was shown to decrease alpha (1) antitrypsin-LDL complex, an index of oxidative stress, and also to decrease some lipid markers.

Improvement of intradialytic hypotension in diabetic hemodialysis patients using vitamin E-bonded polysulfone membrane dialyzers

Currently, there are no detailed reports on the effects of vitamin E-bonded polysulfone (PS) membrane dialyzers on intradialytic hypotension (IDH) in diabetic hemodialysis (HD) patients. This study was designed to evaluate changes in intradialytic systolic blood pressure (SBP) using "VPS-HA" vitamin E-bonded super high-flux PS membrane dialyzers. The subjects were 62 diabetic HD patients whose intradialytic SBP fell by more than 20%. Group A comprised patients who required vasopressors to be able to continue treatment or who had to discontinue therapy due to their lowest intradialytic SBP being observed at 210 min (28 patients). Group B comprised patients who showed no symptoms and required no vasopressors but showed a gradual reduction in blood pressure, with the lowest intradialytic SBP seen at the end of dialysis (34 patients). The primary outcome was defined as the lowest intradialytic SBP after 3 months using VPS-HA. Secondary outcomes included changes in the following: lowest intradialytic diastolic blood pressure, pulse pressure, pulse rate, plasma nitric oxide and peroxynitrite, serum albumin, and hemoglobin A1c. Group A's lowest intradialytic SBP had significantly improved at 3 months (128.0 ±  25.1 mm Hg vs. 117.1 ± 29.2 mm Hg; P = 0.017). Group B's lowest intradialytic SBP had significantly improved at 1 month (134.4 ± 13.2 mm Hg vs. 121.5 ± 25.8 mm Hg; P =  0.047) and 3 months (139.1 ± 20.9 mm Hg vs. 121.5 ±  25.8 mm Hg; P = 0.011). We conclude that VPS-HA may improve IDH in diabetic HD patients.

Improved management of intradialytic hypotension (IDH) using vitamin E-bonded polysulfone membrane dialyzer

BACKGROUND

Intradialytic hypotension (IDH) is a common clinical trait in hemodialysis (HD) which is caused by poor biocompatibility of the dialyzer membrane. Aiming to improve IDH, vitamin E-bonded polysulfone dialyzer (VPS-H) was evaluated in a pilot study.

METHODS

Eight IDH patients on standard HD were switched from their conventional high-flux dialyzers to VPS-H, and intradialytic blood pressure (BP) was monitored regularly for 10 months.

RESULTS

The results showed that hypotension of systolic BP (SBP), diastolic BP (DBP) and pulse pressure (PP) during the session were improved after changing the dialyzer. Notably, almost all the values recorded from 120 minutes into the session until the end of the treatment in the period between the second and tenth month after treatment were significantly different from the corresponding baseline values. Moreover, after 8 to 10 months, the SBP prior to a dialysis session was significantly reduced compared with baseline values. On the other hand, the pulse rate showed no difference throughout the study period.

CONCLUSIONS

This study provides early evidence of the beneficial role that vitamin E-bonded dialyzers may have in preventing IDH. Larger controlled trials are needed to confirm this original finding.

uPAR (CD87) as a biocompatibility marker of dialysis membrane

BACKGROUND/AIMS

Hemodialysis (HD) therapy may lead to functional changes in patient leukocytes. For example, the upregulation of inflammatory cytokines, such as IL-1beta and TNFalpha, has been well characterized. However, these findings do not explain the entire response of leukocytes in HD. In this study, we carried out a comprehensive gene expression analysis in leukocytes treated with various dialysis membranes using DNA microarrays. The identified gene has the potential to be a new marker for testing dialysis membrane biocompatibility.

METHODS

Gene expression profiles were compared between a group of leukocytes treated with various dialysis membranes and an untreated group by using DNA microarray analysis. Expression was confirmed by quantitative RT-PCR. The expression of the gene product (leukocyte surface protein) was examined in 20 chronic HD patients by flow cytometry.

RESULTS

In addition to the inflammatory cytokines, the urokinase plasminogen activator receptor (uPAR or CD87) gene was induced in leukocytes treated with each dialysis membrane. The extent of induction depended on the membrane's material composition. The expression of the uPAR (CD87) protein on leukocytes was markedly increased in patients undergoing dialysis therapy. The magnitude of uPAR (CD87) protein expression was correlated with clinical findings, i.e., the degree of leukopenia and the expression of adhesion molecules.

CONCLUSIONS

The gene and protein expression of uPAR (CD87) depended on the dialysis membrane material and correlated closely with clinical findings. These results suggest that uPAR has the potential to serve as a marker not only for clinical use but also for the development of new dialysis membranes.

In vivo expansion of transduced murine hematopoietic cells with a selective amplifier gene

BACKGROUND

Hematopoietic stem-cell-directed gene transfer has achieved limited success in transducing clinically relevant levels of target cells. The expansion of gene-modified cells is one way to circumvent the problem of inefficient transduction with current vectors. To this end, we have developed 'selective amplifier genes' (SAGs) that encode chimeric proteins that are a fusion of granulocyte colony-stimulating factor receptor and the steroid-binding domain. Prototype SAGs conferred estrogen-responsive growth on murine hematopoietic progenitors.

METHODS

We constructed a retroviral vector coexpressing an SAG for 4-hydroxytamoxifen (Tm)-specific proliferation and the enhanced green fluorescent protein (EGFP). Murine bone marrow cells were transduced with this vector and transplanted into myeloablated mice. Subsequently, recipients were challenged with Tm, and EGFP(+) cells were enumerated.

RESULTS

The challenge induced a significant increase in EGFP(+) leukocytes (21 +/- 4% to 27 +/- 5%), while EGFP(+) cells decreased in untreated animals (21 +/- 5% to 10 +/- 3%). Three months later, bone marrow cells were transplanted from the unchallenged mice to secondary hosts. Again the administration of Tm resulted in an increase of EGFP(+) cells (16 +/- 4% to 35 +/- 3%), contrasting to a decrease in controls (22 +/- 4% to 12 +/- 4%), and the difference was significant for more than 3 months. A detailed study of lineage showed a preferential expansion of EGFP(+) cells in granulocytes and monocytes following Tm administration.

CONCLUSIONS

Long-term repopulating cells were transduced with the SAG, and the transduced granulocyte/monocyte precursors were most likely to be expandable in vivo upon Tm stimulation.

Selective growth advantage of wild-type lymphocytes in X-linked SCID recipients

The cytokine receptor common gamma chain (gamma c) plays a pivotal role in multiple interleukin signaling, and gamma c gene mutations cause an X-linked form of SCID (X-SCID). Recently, gamma c gene transfer into the autologous X-SCID BM achieved appreciable lymphocyte reconstitution, contrasting with the limited success in previous gene therapy trials targeting hematopoietic stem cells. To understand the mechanisms underlying this success, we examined the repopulating potential of the wild-type (WT) BM cells using an X-SCID mouse model. Limited numbers of WT cells were infused into non-ablated WT and X-SCID hosts. Whereas no appreciable engraftment was observed in WT recipients, donor-derived lymphocytes repopulated well in X-SCID, reaching 37% (10(6)cells given) and 53% (10(7) cells given) of the normal control value 5 months post BMT. A lineage analysis showed a predominance of the donor-derived lymphocytes (CD4(+) T, CD8(+) T, B and NK cells) in X-SCID while the donor-derived granulocytes and monocytes engrafted poorly. These results showed a selective advantage of WT cells in X-SCID, and that the advantage was restricted to lymphocytes. In human gene therapy for X-SCID, an analogous growth advantage would greatly enhance the repopulation of lymphocytes derived from a very small number of gamma c gene-supplemented precursors.

Human homologues of Delta-1 and Delta-4 function as mitogenic regulators of primitive human hematopoietic cells

Delta-mediated Notch signaling controls cell fate decisions during invertebrate and murine development. However, in the human, functional roles for Delta have yet to be described. This study reports the characterization of Delta-1 and Delta-4 in the human. Human Delta-4 was found to be expressed in a wide range of adult and fetal tissues, including sites of hematopoiesis. Subsets of immature hematopoietic cells, along with stromal and endothelial cells that support hematopoiesis, were shown to express Notch and both Delta-1 and Delta-4. Soluble forms of human Delta-1 (h Delta-1) and h Delta-4 proteins were able to augment the proliferation of primitive human hematopoietic progenitors in vitro. Intravenous transplantation of treated cultures into immune-deficient mice revealed that h Delta-1 is capable of expanding pluripotent human hematopoietic repopulating cells detected in vivo. This study provides the first evidence for a role of Delta ligands as a mitogenic regulator of primitive hematopoietic cells in the human. (Blood. 2001;97:1960-1967)

The notch ligand jagged-1 represents a novel growth factor of human hematopoietic stem cells

The Notch ligand, Jagged-1, plays an essential role in tissue formation during embryonic development of primitive organisms. However, little is known regarding the role of Jagged-1 in the regulation of tissue-specific stem cells or its function in humans. Here, we show that uncommitted human hematopoietic cells and cells that comprise the putative blood stem cell microenvironment express Jagged-1 and the Notch receptors. Addition of a soluble form of human Jagged-1 to cultures of purified primitive human blood cells had modest effects in augmenting cytokine-induced proliferation of progenitors. However, intravenous transplantation of cultured cells into immunodeficient mice revealed that human (h)Jagged-1 induces the survival and expansion of human stem cells capable of pluripotent repopulating capacity. Our findings demonstrate that hJagged-1 represents a novel growth factor of human stem cells, thereby providing an opportunity for the clinical utility of Notch ligands in the expansion of primitive cells capable of hematopoietic reconstitution.

Large amount of vitamin A has no major effects on thyroidal hormone synthesis in two-stage rat thyroid carcinogenesis model using N-bis(2-hydroxypropyl)nitrosamine and thiourea

In our previous investigation, which focused on two-stage carcinogenicity in the thyroid, rats were administered N-bis(2-hydroxypropyl)nitrosamine (DHPN), followed by thiourea (TU) over an experimental period of 19 weeks. Simultaneous treatment with a high level of vitamin A (VA) enhanced the induction of proliferative lesions that originated from the thyroidal follicular epithelium. To examine whether hormone synthesis in the thyroid could be inhibited by simultaneous treatment with a large amount of VA and TU, all of the rats were initially given a single subcutaneous injection of 2,800 mg DHPN/kg followed by a supply of 0% TU + 0% VA (DHPN only, control group), 0.2% TU in their drinking water (DHPN/TU group), 0.1% VA in their diet (DHPN/VA group), or 0.2% TU + 0.1% VA (DHPN/TU + VA group) during an experimental period of 4 weeks. Results obtained indicate that the iodine uptake and organification, namely iodination of tyrosine residue in thyroglobulin, of the thyroid, were significantly decreased in the DHPN/TU group compared to the DHPN control group. The variation in these values was attributable to the inhibitory effect of TU upon thyroid hormone synthesis. Results obtained from the DHPN/TU + VA and DHPN/TU groups were comparable. Therefore, the possibility that modification of hormone synthesis contributes to the enhancing effect of simultaneous treatment with a large amount of VA on thyroidal tumor induction by TU is considered to be very minimal.