Dong Cheol Han

Uremia induces functional incompetence of bone marrow-derived stromal cells

BACKGROUND Chronic kidney disease (CKD) is associated with increased risk for cardiovascular diseases (CVD). We hypothesized that inadequate angiogenic response in uremic patients could result from dysfunction of bone marrow-derived stromal cells [mesenchymal stem cells (MSCs)]. METHODS We investigated whether MSCs are functionally competent in uremia induced by partial kidney ablation in C57Bl/6J mice. RESULTS Uremic MSCs showed decreased expression of vascular endothelial growth factor (VEGF), VEGF receptor (VEGFR)1 and stromal cell-derived factor (SDF)-1α, increased cellular senescence, decreased proliferation, defects in migration in response to VEGF and SDF-1α and in vitro tube formation. Interestingly, the expression of fibroblast-specific protein-1 was higher in uremic MSCs. Uremia decreased hypoxia-inducible factor-1α, VEGF and VEGFR1 expression under hypoxia and Akt phosphorylation in both basal and VEGF-stimulated states. A diminished mitogenic effect on endothelial proliferation was observed in conditioned media from uremic MSCs. In addition, intravital microscopic analysis showed decreased angiogenesis in uremic MSCs. CONCLUSION These results clearly demonstrate the functional incompetence in MSCs under uremic conditions and may significantly contribute to the disproportionately high risk for CVD in patients with CKD.

Validation of the Oxford classification of IgA nephropathy: a single-center study in Korean adults.

Background/Aims The recently published Oxford classification of IgA nephropathy (IgAN) proposed a split system for histological grading, based on prognostic pathological features. This new classification system must be validated in a variety of cohorts. We investigated whether these pathological features were applicable to an adult Korean population. Methods In total, 69 adult Korean patients with IgAN were analyzed using the Oxford classification system at Soonchunhyang University Hospital, Seoul, Korea. All cases were categorized according to Lees classification. Renal biopsies from all patients were scored by a pathologist who was blinded to the clinical data for pathological variables. Inclusion criteria were age greater than 18 years and at least 36 months of follow-up. We excluded cases with secondary IgAN, diabetic nephropathy combined other glomerulopathies, less than 36 months of follow-up, and those that progressed rapidly. Results The median age of the patients was 34 years (range, 27 to 45). Mean arterial blood pressure was 97 ± 10 mmHg at the time of biopsy. The median follow-up period was 85 months (range, 60 to 114). Kaplan-Meier analysis showed significant prognostic predictions for M, E, and T lesions. A Cox proportional hazard regression analysis also revealed prognostic predictions for E and T lesions. Conclusions Using the Oxford classification in IgAN, E, and T lesions predicted renal outcome in Korean adults after taking clinical variables into account.

Effect of Prolonged Subcutaneous Implantation of Peritoneal Catheter on Peritonitis Rate during CAPD: A Prospective Randomized Study

We conducted a prospective randomized controlled study to confirm our earlier observation that prolonged subcutaneous implantation of peritoneal catheter reduced peritonitis rate when compared to retrospective data from patients with catheters placed by conventional access technique. A total of 60 patients were randomized into two groups: 30 patients had catheters left implanted subcutaneously for 6 weeks (I) and the other 30 patients had catheters inserted by conventional technique and had 6 weeks of break-in period (C). Subgroups of 15 patients each with new and conventional techniques used Y-connector (IY, CY) and remaining patients used standard spikes (IS, CS).Mean age was 47.7 years (range 16–71); 61.0% were male and 44.1% diabetics. Peritonitis, exit site infection, simultaneous peritonitis and exit site infection, and complication related to Staphylococcus or Pseudomonas infections were observed for up to 2 years in each patient after initiation of bag exchange or until termination of CAPD by transfer to hemodialysis or by death.Total duration of observation was 493.2 patient-months for new access technique and 409.6 patient-months for conventional technique. Patients in IY group had the lowest incidence of peritonitis (1/14.9 patient-months) and exit site infection (1/16.8 patient-months) among four subgroups. Peritonitis rate in IY was significantly lower compared to CY or CS. The total peritonitis-free period in those patients who did not experience peritonitis during the observation period was also significantly longer in IY (120 patient-months) than in CY (26 patient-months), IS (10.6 patient-months), or CS (10.4 patient-months). Simultaneous peritonitis and exit site infection was observed in none of IY group but 3 episodes in CY, 4 episodes in IS, and 3 episodes in CS. The rates of complications related to Staphylococcus aureus and Pseudomonas infections were also significantly lower in IY than in CY, IS, or CS. Technique survival did not differ between the two groups.The present results confirm our previous observation that the new access technique reduces the incidence of peritonitis probably by reducing infection via periluminal route. The Y-connector system further reduces peritonitis rate by reducing infection via intraluminal route.

Risk factors for mortality in diabetic peritoneal dialysis patients

BACKGROUND It is well established that the survival rate of diabetic end-stage renal disease patients remains the lowest among all primary diagnoses probably because of higher prevalence of cardiovascular diseases (CVD) associated with diabetes. This study was designed to evaluate the impact of CVD and other risk factors individually or in combination on mortality in diabetic peritoneal dialysis (PD) patients. METHODS In a retrospective study, 213 incident PD patients [118 had diabetes mellitus (DM), 94 were female, mean age 55 ± 13 years] underwent initial assessment of nutritional status, comorbid disease (CMD) survey, residual renal function (RRF), dialysis adequacy and peritoneal transport characteristics at a mean of 9 days (range, 3-24 days) after start of PD and were then followed for 30 ± 24 months (range, 3-115 months). Of 213 patients, 154 patients were reassessed after a mean of 11 months (range, 6-19 months). Nutritional status was assessed by subjective global assessment and other methods. CMD was graded by Davies index and included DM, CVD, liver disease and respiratory disease. RESULTS On Kaplan-Meier analysis, patient survival was significantly lower in female DM patients compared to other groups. The 3-year patient survival rate was 46, 70, 82 and 83% for female DM, male DM, male non-DM and female non-DM, respectively (P = 0.003). On Cox proportional hazards multivariate analysis including all patients, old age, presence of CVD or protein-energy wasting (PEW), low serum albumin concentration and low RRF were independent predictors of mortality but not DM per se or female gender. In DM patients, old age, female gender, presence of CVD or PEW and low RRF were independent predictors of mortality while old age was the only risk factor in non-DM patients. After adjustment for age, gender and RRF, DM patients with both CVD and PEW had a risk of mortality that was 3.3 times that of DM patients without CVD and PEW. In DM patients without CVD and PEW, patient survival was not different from that of non-DM patients without CVD and PEW. CONCLUSIONS DM per se was not a risk factor for mortality in this group of PD patients. Instead, the higher mortality rate in diabetic PD patients, in particular among female patients, was mainly attributable to concurrent morbidity such as CVD and PEW, together with low RRF.

An Assessment of AKIN Criteria for Hospital-Acquired Acute Kidney Injury: A Prospective Observational Cohort Study

Background and Aims: The Acute Kidney Injury Network (AKIN) criteria assert a new definition for acute kidney injury (AKI). We investigated the incidence of hospital-acquired AKI, along with the clinical characteristics and outcomes in hospitalized patients according to AKIN stage. Methods: We performed a prospective, observational, single-center study. We monitored serum creatinine everyday for all patients using a hospital data survey system during the study period from September 2007 to February 2008. Results: Hospital-acquired AKI occurred in 1.2% of all hospitalized patients during the study period. Among patients with AKI, 29.2% were in stage 1, 36.5% were in stage 2 and 34.4% were in stage 3. A significantly higher rate of renal recovery was observed in patients with lower-stage injuries (71.4, 60.0, and 21.2% for stages 1, 2, and 3, respectively). Mortality for patients with stage 3 AKI (51.5%) was significantly higher than that for patients with stages 1 or 2 (p < 0.013). Independent risk factors for mortality in patients with AKI included malignancy, stage 3 AKI, diuretic use, and intensive care unit admission prior to AKI. Conclusions: Our findings support the utility of the AKIN criteria for hospital-acquired AKI, and demonstrate that stage 3 AKI poses a significant risk for poor patient and renal outcomes.

In situ detection of hepatitis C virus RNA in liver tissue using a digoxigenin-labeled probe created during a polymerase chain reaction

The cellular localization of hepatitis C virus (HCV) RNA in liver tissue was studied by nonisotopic in situ hybridization using a digoxigenin‐labeled cDNA probe created during a polymerase chain reaction on samples from 16 patients with chronic HCV infection. Hybridization signals were recognized in the cytoplasm of the hepatocytes, and a few hepatocytes had hybridization signals in the nucleus as well. HCV RNA positive hepatocytes were found in 1 of 9 patients with chronic persistent hepatitis, 2 of 5 patients with chronic active hepatitis, and in each of 2 patients with chronic active hepatitis and cirrhosis. Positive signals were found in many hepatocytes within the lobule in liver sections of patients with advanced chronic active hepatitis. A number of HCV RNA positive hepatocytes were found in nodules, but not in the area of fibrosis. On the other hand, positive signals were found in a few hepatocytes scattered in the lobule in a patient with chronic persistent hepatitis. The mean ALT levels in the patients with positive signal (175.6 ± 44.2 U/L) were significantly higher than in those without a signal (70.27 ± 16.1 U/L) (P < 0.05). The findings suggest that a larger amount of HCV may be present during the advanced than during the early stages of type C hepatitis and nonisotopic in situ hybridization using a digoxigenin‐labeled HCV cDNA probe created during a polymerase chain reaction deserves wider application for the detection of HCV replication in specimens.

Screening and study enrolment in the Randomized Evaluation of Normal vs. Augmented Level (RENAL) Replacement Therapy Trial

Background and Objectives: Aspects of trial design, screening and study efficiency can affect recruitment and the findings of the trial itself. A clear understanding of the screening and study inclusion process will assist clinicians in interpreting trial results. Design: Prospective observational data collection on all patients screened for possible inclusion in a randomized controlled trial of normal vs. augmented renal replacement therapy in critically ill patients (the RENAL Trial). Setting: 35 hospitals in Australia and New Zealand. Participants: All patients screened for the RENAL Trial. Results: We screened 4,551 patients. Of these patients, 767 were ineligible because of lack of inclusion criteria and 2,085 because of exclusion criteria. Of the remaining 1,699, 1,508 (88.7%) were enrolled. The three most common exclusion criteria which prevented recruitment of potentially eligible patients were that the patient had end-stage kidney failure and was already on chronic dialysis (484; 23.2%), the patient’s body weight was either <60 or >120 kg (456; 21.8%), and the fact that the patient had already received renal replacement therapy during the index admission. Important modifiable impediments to recruitment were inability to obtain consent in 191 cases, unavailability of research staff in 124 cases, physician objection in 89 cases, and inability to deliver the trial protocol in 78 cases. Conclusion: The RENAL Trial’s enrolment efficiency was high and compared favourably with previous large intensive care units trials and with that of trials in patients with acute renal failure. The high rate of enrolment suggests that the results can be applied with confidence to most patients with de novo acute renal failure. The loss of close to 1.5% of patients due to consent issues highlights a common problem in critical care trials. The low rate of physician objection suggests clinical equipoise.

Subtle change of cystatin C, with or without acute kidney injury, associated with increased mortality in the intensive care unit ☆ ☆☆

PURPOSE Recent epidemiologic studies suggest a significant association between small increases in serum creatinine (sCr) and adverse outcomes. The Acute Kidney Injury Network (AKIN) sought to increase the sensitivity of the AKIN criteria for acute kidney injury (AKI) by recommending the use of small changes in sCr for the diagnosis of AKI. Several recent studies have reported that serum cystatin C (cysC) is more accurate than sCr as a surrogate for the glomerular filtration rate. This study was performed to determine whether small increases in cysC (≥0.3 mg/L within 48 hours) are associated with clinical outcomes in critically ill patients. MATERIALS AND METHODS This was a prospective study of 274 consecutive patients admitted to the intensive care unit. Clinical data, including urine output, sCr, cysC, and outcomes, were collected for up to 3 months. Kaplan-Meier curves were used to determine the 90-day survival rate. Mortality was adjusted according to the Cox proportional hazards model. RESULTS Acute kidney injury developed in 84 (30.7%) patients based on the AKIN criteria. Among these patients, 42 (50%) had stage 1; 8 (9.5%), stage 2; and 34 (40.4%), stage 3 disease. Fourteen patients with increased cysC did not have AKI by AKIN criteria. The overall 90-day mortality was 20.8%. When mortality was stratified by group, it was 5.7% for the no-AKI-without-cysC-increment group, 28.6% for the no-AKI-with-increased-cysC group, 33.3% for the AKIN stage 1 group, 62.5% for the AKIN stage 2 group, and 70.6% for the AKIN stage 3 group (P < .001). Kaplan-Meier curves were constructed for each group based on stage and 90-day survival. The Cox analysis showed that patients who met AKIN criteria and patients with increases of cysC without AKI had associated mortality. In addition, patients with increases in cysC without AKI had outcomes similar to the patients with stage 1 AKI. CONCLUSIONS Small increases of cysC were associated with increased mortality in intensive care unit patients independent of diagnosis of AKI by AKIN criteria.

Uremic Toxin p‐Cresol Induces Akt‐Pathway‐Selective Insulin Resistance in Bone Marrow‐Derived Mesenchymal Stem Cells

We reported a functional incompetence in mesenchymal stem cells (MSCs) under uremia, but the mechanisms have not been explored. To study the mechanisms of dysfunctional MSCs induced by uremia, we characterized insulin signaling in MSCs and investigated the effect of uremic toxin, p‐cresol, on the proangiogenic actions of insulin. In MSCs, insulin induced hypoxia‐inducible factor (HIF)−1α, vascular endothelial growth factor, and stromal cell‐derived factor 1α expressions via PI3K/Akt‐dependent pathway. MSCs treated with p‐cresol exhibited altered insulin signaling in a selective manner for insulin receptor substrate‐1/PI3K/Akt pathway, whereas ERK pathway remained active. The insulin‐induced increase of HIF‐1α was blunted by p‐cresol treatment. This Akt‐selective insulin resistance was also observed in MSCs isolated from chronic kidney disease (CKD) mice. In mice model of hindlimb ischemia, blood flow recovery, capillary density, and local production of angiogenic factors in the ischemic limb treated with CKD MSCs were significantly inferior to those promoted by control MSCs. However, modifying CKD MSCs by overexpression of HIF‐1α restored all of these changes. Taken together, these data suggest that p‐cresol contributes to insulin resistance in a selective manner for Akt pathway. This might be a biological explanation for the functional incompetence of MSCs under uremia through defects in the insulin‐induced elevation of HIF‐1α protein expression. Stem Cells 2014;32:2443–2453

Impact of incremental risk factors on peritoneal dialysis patient survival: proposal of a simplified clinical mortality risk score.

Background/Aim: Peritoneal dialysis (PD) patient survival is influenced by many factors and there is no consensus on the relative importance of these predictors, independently or combined. This study was designed to evaluate how these independent factors, alone or in various combinations, may influence PD patient survival. Methods: A peritoneal equilibration test, subjective global assessment (SGA), and comorbid diseases (CMD) were assessed. Results: On multivariate analysis, age (>60 years), CMD, malnutrition, and low RRF (≤2 ml/min) were independent predictors of mortality. Three-year patient survival was 100, 95, 75, 49, and 0%, and the risk ratio for mortality was 1.0, 6.6, 21.9, and 85.9 in patients with none, one, two, three, and four of these risk factors, respectively. Conclusions: The combination of independent predictors of mortality in PD patients leads to a markedly increasing risk for mortality. Evaluation of a single risk factor underestimates the true impact of risk factors.