Jaeseok Yang

Chronic asymptomatic pyuria precedes overt urinary tract infection and deterioration of renal function in autosomal dominant polycystic kidney disease

BackgroundUrinary tract infection (UTI) occurs in 30%-50% of individuals with autosomal dominant polycystic kidney disease (ADPKD). However, the clinical relevance of asymptomatic pyuria in ADPKD patients remains unknown.MethodsWe retrospectively reviewed medical records of 256 ADPKD patients who registered to the ADPKD clinic at Seoul National University Hospital from Aug 1999 to Aug 2010. We defined the asymptomatic pyuria as more than 5-9 white blood cells in high-power field with no related symptoms or signs of overt UTI. Patients were categorized into 2 groups depending on its duration and frequency: Group A included non-pyuria and transient pyuria patients; Group B included recurrent and persistent pyuria patients. The association between asymptomatic pyuria and both the development of overt UTI and the deterioration of renal function were examined.ResultsWith a mean follow-up duration of 65.3 months, 176 (68.8%) out of 256 patients experienced 681 episodes of asymptomatic pyuria and 50 episodes of UTI. The annual incidence of asymptomatic pyuria was 0.492 episodes/patient/year. The patients in group B showed female predominance (58.5% vs. 42.0%, P=0.01) and experienced an upper UTI more frequently (hazard ratio: 4.612, 95% confidence interval: 1.735-12.258; P=0.002, adjusted for gender and hypertension). The annual change in estimated glomerular filtration rate (ΔeGFR) was significantly larger in magnitude in group B than in group A (-2.7±4.56 vs. -1.17±5.8, respectively; P=0.01). Age and Group B found to be the independent variables for ΔeGFR and developing end-stage renal disease (16.0% vs. 4.3%, respectively; P=0.001).ConclusionsChronic asymptomatic pyuria may increase the risk of developing overt UTI and may contribute to declining renal function in ADPKD.

IL-2/Anti-IL-2 Complex Attenuates Renal Ischemia-Reperfusion Injury through Expansion of Regulatory T Cells

Regulatory T cells (Tregs) can suppress immunologic damage in renal ischemia-reperfusion injury (IRI), but the isolation and ex vivo expansion of these cells for clinical application remains challenging. Here, we investigated whether the IL-2/anti-IL-2 complex (IL-2C), a mediator of Treg expansion, can attenuate renal IRI in mice. IL-2C administered before bilateral renal IRI induced Treg expansion in both spleen and kidney, improved renal function, and attenuated histologic renal injury and apoptosis after IRI. Furthermore, IL-2C administration reduced the expression of inflammatory cytokines and attenuated the infiltration of neutrophils and macrophages in renal tissue. Depletion of Tregs with anti-CD25 antibodies abrogated the beneficial effects of IL-2C. However, IL-2C-mediated renal protection was not dependent on either IL-10 or TGF-β. Notably, IL-2C administered after IRI also enhanced Treg expansion in spleen and kidney, increased tubular cell proliferation, improved renal function, and reduced renal fibrosis. In conclusion, these results indicate that IL-2C-induced Treg expansion attenuates acute renal damage and improves renal recovery in vivo, suggesting that IL-2C may be a therapeutic strategy for renal IRI.

Generation and Characterization of Human Heme Oxygenase-1 Transgenic Pigs

Xenotransplantation using transgenic pigs as an organ source is a promising strategy to overcome shortage of human organ for transplantation. Various genetic modifications have been tried to ameliorate xenograft rejection. In the present study we assessed effect of transgenic expression of human heme oxygenase-1 (hHO-1), an inducible protein capable of cytoprotection by scavenging reactive oxygen species and preventing apoptosis caused by cellular stress during inflammatory processes, in neonatal porcine islet-like cluster cells (NPCCs). Transduction of NPCCs with adenovirus containing hHO-1 gene significantly reduced apoptosis compared with the GFP-expressing adenovirus control after treatment with either hydrogen peroxide or hTNF-α and cycloheximide. These protective effects were diminished by co-treatment of hHO-1 antagonist, Zinc protoporphyrin IX. We also generated transgenic pigs expressing hHO-1 and analyzed expression and function of the transgene. Human HO-1 was expressed in most tissues, including the heart, kidney, lung, pancreas, spleen and skin, however, expression levels and patterns of the hHO-1 gene are not consistent in each organ. We isolate fibroblast from transgenic pigs to analyze protective effect of the hHO-1. As expected, fibroblasts derived from the hHO-1 transgenic pigs were significantly resistant to both hydrogen peroxide damage and hTNF-α and cycloheximide-mediated apoptosis when compared with wild-type fibroblasts. Furthermore, induction of RANTES in response to hTNF-α or LPS was significantly decreased in fibroblasts obtained from the hHO-1 transgenic pigs. These findings suggest that transgenic expression of hHO-1 can protect xenografts when exposed to oxidative stresses, especially from ischemia/reperfusion injury, and/or acute rejection mediated by cytokines. Accordingly, hHO-1 could be an important candidate molecule in a multi-transgenic pig strategy for xenotransplantation.

Immunosuppressive mechanisms of embryonic stem cells and mesenchymal stem cells in alloimmune response.

Although both embryonic stem cells (ESCs) and mesenchymal stem cells (MSCs) are known to have immunosuppressive effects, the mechanisms of immunosuppression are still controversial. Both types of stem cells suppressed not only the proliferation but also survival of CD4(+) T cells in vitro. They suppressed secretion of various cytokines (IL-2, IL-12, IFN-γ, TNF-α, IL-4, IL-5, IL-1β, and IL-10), whereas there was no change in the levels of TGF-β or IDO. Classic and modified transwell experiments demonstrated that immunosuppressive activities were mainly mediated by cell-to-cell contact. Granzyme B in the ESCs played a significant role in their immunosuppression, whereas PDL-1, Fas ligand, CD30 or perforin was not involved in the contact-dependent immunosuppression. However, none of the above molecules played a significant role in the immunosuppression by the MSCs. Interestingly, both stem cells increased the proportion of Foxp3(+) regulatory T cells. Our results showed that both ESCs and MSCs suppressed the survival as well as the proliferation of T cells by mainly contact-dependent mechanisms and increased the proportion of regulatory T cells. Granzyme B was involved in immunosuppression by the ESCs in a perforin-independent manner.

In situ induction of dendritic cell–based T cell tolerance in humanized mice and nonhuman primates

Administration of an ICAM-1–specific antibody arrests dendritic cells in a semi-immature state and facilitates antigen-specific T cell tolerance to islet allografts in humanized mice and Rhesus monkeys.

Impact of polymorphisms of TLR4/CD14 and TLR3 on acute rejection in kidney transplantation

Background. Organ transplantation itself inevitably activates the innate immune system by toll-like receptors (TLRs), potentially leading to allograft rejection and graft failure. We evaluated the possible association between the TLR4/CD14 and TLR3 polymorphisms of donor-recipient pairs, and acute rejection after living donor kidney transplantation. Methods. TLR4 −1607T/C (rs10759932), −2026A/G (rs1927914); CD14 −159C/T (rs2569190); and TLR3 rs3775290, rs3775291, and rs3775296 were genotyped using DNA samples from 216 donor-recipient pairs of adult living donor kidney transplantation between January 1996 and July 2006. Dual luciferase reporter assay was performed to determine the functional significance of promoter single-nucleotide polymorphisms (SNPs) of TLR4. Results. Acute rejection occurred in 42 recipients (19.4%) of 216 adult transplant patients within 1 year. The genotype distributions of both recipient and donor TLR4 rs10759932 differed significantly between the control (no rejection) and acute rejection groups. For recipient rs10759932, the adjusted odds ratio for the TC+CC over TT genotype was 0.25 (95% confidence interval, 0.11–0.57; P =0.001). When the rs10759932 CC genotype was present in the recipient or donor, no episode of acute rejection occurred (Fisher’s exact test, P =0.023). The presence of the rs10759932 C allele was associated with higher rejection-free survival rates (log-rank test, P =0.0053). However, there was no difference in transcriptional activity between wild-type and variant promoters of TLR4. In contrast to TLR4, SNPs of TLR3 or CD14 had no influence on acute rejection. Conclusion. These findings suggest the importance of TLR4 in the pathogenesis of acute rejection in kidney transplantation.

Factors associated with aortic stiffness and its change over time in peritoneal dialysis patients

BACKGROUND An increase in aortic stiffness, as reflected by an increase in pulse wave velocity (PWV), is an important predictor of cardiovascular mortality in dialysis patients. Decreased serum concentration of calcification inhibitor, such as fetuin-A, is inversely related to mortality in haemodialysis patients. Our aim is to investigate the factors associated with aortic stiffness and its change over time in peritoneal dialysis (PD) patients. METHODS As a prospective observational study, we analysed 67 PD patients, aged 50 ± 14 years (mean ± SD) and with dialysis duration of 26 (5-58) months (median, interquartile range). At baseline, age, mean arterial pressure (MAP), left ventricular mass (LVM) index, diabetes, serum albumin, calcium (Ca), phosphorus (P) and intact parathyroid hormone (iPTH), uric acid, total bilirubin, high-sensitivity C-reactive protein (hsCRP), fetuin-A, and residual renal function were included in association analysis with aortic stiffness represented by heart-to-femoral PWV (hfPWV). We also evaluated simple vascular calcification score (SVCS) with plain radiograph of the pelvis and both hands. PWV was measured both at baseline and at 1 year. Change of aortic stiffness was determined by △PWV (difference between 1-year PWV and baseline PWV). Time-averaged concentrations were used to evaluate the relation between biologic markers and changes of aortic stiffness. RESULTS hfPWV was 1022 ± 276 cm/s at baseline, and hfPWV determined at 1 year was 1069 ± 317 cm/s. Mean serum fetuin-A concentration was 0.34 ± 0.08 g/L. At baseline, aortic PWV positively correlated with age, smoking status, diabetes, MAP, total cholesterol and LDL cholesterol. On the other hand, aortic PWV inversely correlated with fetuin-A, log PTH, haemoglobin and albumin. In a multiple regression model, association of serum fetuin-A (β = -0.329, P = 0.003) with aortic PWV remained significant, along with age (β = 0.512, P < 0.001), MAP (β = 0.215, P = 0.047) and log PTH (β = -0.269, P = 0.025). At follow-up, △MAP (β = 0.500, P < 0.001) and time-averaged TG (aTG) (β = 0.259 P = 0.019) were determinants of △PWV. CONCLUSIONS For our PD patients, serum fetuin-A was an independent determinant of aortic stiffness, as well as age, MAP and log PTH. Although 1 year is not sufficient to observe the change of aortic stiffness, some patients exhibited >15% increase of PWV during this period. △MAP and aTG were factors affecting the change of PWV. Follow-up over a longer period is necessary to elucidate factors that determine changes of aortic stiffness over time from PD patients.

Effect of multidisciplinary pre-dialysis education in advanced chronic kidney disease: Propensity score matched cohort analysis.

Aim:  The mortality and morbidity of end‐stage renal failure patients remains high despite recent advances in pre‐dialysis care. Previous studies suggesting a positive effect of pre‐dialysis education were limited by unmatched comparisons between the recipients and non‐recipients of education. The present study aimed to clarify the roles of the multidisciplinary pre‐dialysis education (MPE) in chronic kidney disease patients.

Inducible nitric oxide synthase inhibitors prolonged the survival of skin xenografts through selective down-regulation of pro-inflammatory cytokine and CC-chemokine expressions.

To elucidate the possible immunoregulatory role of nitric oxide (NO) in cellular xenograft rejection we performed rat-to-mouse skin xenotransplantation. The rat skin engrafted mice were treated with the inducible NO synthase (iNOS) inhibitors, aminoguanidine (AMG, 200 mg/kg) and NG-nitro-L-arginine methyl ester (L-NAME, 60 mg/kg) every other day until rejection. Skin xenograft survival was monitored and immune cell infiltration and intragraft cytokine and chemokine mRNA expressions were analyzed 7 days after grafting. Compared with the control mice, the AMG- and L-NAME treated mice showed delayed xenograft rejection by approximately 3 days (8.9 +/- 0.7 days vs. 11.7 +/- 1.2 and 12.0 +/- 0.9 days, respectively). Infiltrations of CD11b+, MOMA-2+ cells and neutrophils were significantly reduced in both AMG- and L-NAME treated graft but CD4+ and CD8+ cells were not. The expression of cytokines such as IL-1beta, IL-2, IL-6, IL-12 and IFN-gamma in AMG- and L-NAME treated grafts were significantly decreased (P<0.01), whereas IL-10, TNF-alpha and TGF-beta1 were unchanged or enhanced. Additionally, the expressions of CC-chemokines, such as RANTES and MIP-1alpha, were significantly reduced (P<0.01) whereas the expressions of CXC-chemokines, such as IP-10 and MIG, were unchanged. These results imply that prolonged rat-to-mouse skin xenograft survival by iNOS inhibitors may be due to the selective inhibition of pro-inflammatory cytokines and chemokines and suggest the possible regulatory role of NO in cytokine and chemokine expressions during xenotransplant rejection.

Impact of tacrolimus intraindividual variability and CYP3A5 genetic polymorphism on acute rejection in kidney transplantation.

Background: Wide variation in tacrolimus concentrations and low tacrolimus exposure have been reported to be associated with poor renal graft outcomes in non-Asians. The CYP3A5 polymorphism is a representative genetic factor that might affect this association, together with environmental factors. We investigated whether tacrolimus variability or the mean tacrolimus trough concentration can influence kidney allograft outcomes in Asians and whether the CYP3A5 polymorphism (rs776746) can affect this relationship. Methods: Data from renal transplant patients between 2000 and 2010 were analyzed retrospectively. The tacrolimus intraindividual variability (IIV) and the mean tacrolimus trough concentration were calculated from the tacrolimus concentrations between 6 and 12 months after transplantation. Results: A total of 249 renal transplant patients were enrolled. The patients with higher tacrolimus IIV had shorter rejection-free survival (P = 0.002). However, there was no difference in rejection-free survival between CYP3A5 expressers and nonexpressers. The tacrolimus IIV was not associated with the CYP3A5 polymorphism. High IIV of tacrolimus was an independent risk factor of biopsy-proven acute rejection after adjusting for mean tacrolimus concentration, HLA mismatch, induction therapy, donor type, and CYP3A5 polymorphism (hazard ratio 2.655, 95% confidence interval 1.394–5.056). Interestingly, the impact of tacrolimus IIV on acute rejection was significant in CYP3A5 expressers, whereas it was not in CYP3A5 nonexpressers. Conclusions: The IIV of tacrolimus trough concentrations had a significant impact on rejection-free survival. The effect was influenced by CYP3A5 polymorphism, although the tacrolimus variability itself was not determined by the CYP3A5 polymorphism.