Dnmt3a regulates myeloproliferation and liver-specific expansion of hematopoietic stem and progenitor cells

DNMT3A mutations are observed in myeloid malignancies, including myeloproliferative neoplasms (MPN), myelodysplastic syndromes (MDS), and acute myeloid leukemia (AML). Transplantation studies have elucidated an important role for Dnmt3a in stem cell self-renewal and in myeloid differentiation. Here we investigated the impact of conditional hematopoietic Dnmt3a loss on disease phenotype in primary mice. Mx1-Cre-mediated Dnmt3a ablation led to the development of a lethal, fully penetrant myeloproliferative neoplasm with myelodysplasia (MDS/MPN) characterized by peripheral cytopenias and by marked, progressive hepatomegaly. We detected expanded stem/progenitor populations in the liver of Dnmt3a-ablated mice. The MDS/MPN induced by Dnmt3a ablation was transplantable, including the marked hepatomegaly. Homing studies showed that Dnmt3a-deleted bone marrow cells preferentially migrated to the liver. Gene expression and DNA methylation analyses of progenitor cell populations identified differential regulation of hematopoietic regulatory pathways, including fetal liver hematopoiesis transcriptional programs. These data demonstrate that Dnmt3a ablation in the hematopoietic system leads to myeloid transformation in vivo, with cell autonomous aberrant tissue tropism and marked extramedullary hematopoiesis (EMH) with liver involvement. Hence, in addition to the established role of Dnmt3a in regulating self-renewal, Dnmt3a regulates tissue tropism and limits myeloid progenitor expansion in vivo.

Preserving the left arm vein in cases of hemodialysis access generating left internal mammary artery steal syndrome

In patients undergoing chronic hemodialysis (HD) through an arm arteriovenous fistula (AVF), coronary insufficiency can occur if the patient undergoes a coronary artery bypass graft (CABG) using the ipsilateral internal mammary artery (1-4). Therefore, the creation of a new AVF after CABG should avoid using the arm ipsilateral to the side where the internal thoracic artery was used. In cases where coronary syndrome appears when this advice is not followed, treatment should be offered aimed at overcoming the hemodynamic interference between the diminished coronary supply through the left or right internal mammary artery by closure of the existing fistula, with or without temporary central venous line insertion until the maturation of a new fistula. We suggest a different approach by moving only the arterial inflow site of the AVF to the controlateral subclavian artery, but in addition, leaving the well functioning venous outflow tract intact. In cases of left internal mammary steal it is achieved by creating a conduit running from the right subclavian artery to the left cephalic vein; therefore, creating a new arterial inflow source, connected to the existing functioning old venous outflow tract to maintain an immediately functioning new fistula without a coronary steal.

Detection of HCV salivary antibodies by a simple and rapid test

Hepatitis C (HCV) is common in developing countries, where blood sampling and expensive sophisticated methods for detection are less available. Hemodialysis patients have high prevalence of HCV and may resemble sick populations in developing countries in relation to immunosuppression and antibodies production. For these reasons anti-HCV antibodies were assayed in saliva of hemodialysis patients by ImmunoComb II assay that is less laborious, relatively inexpensive and easy to perform If the findings are confirmed by larger studies this method may be useful especially in developing countries. Serum and saliva samples were obtained from 37 hemodialysis patients and assayed by ImmunoComb II kit. In positive PCR patients the saliva test had 100% sensitivity, which was as good as serum anti-HCV Axsym testing. Saliva testing had a similar or better specificity than the serum method.

Surveillance of chronic haemodialysis-associated infections in southern Israel

During a 12-month surveillance period, haemodialysis (HD) patients in southern Israel were categorised according to the type of vascular access site (VAS), i.e., arteriovenous (AV) fistula, synthetic AV graft, and cuffed or non-cuffed vascular catheters. Endpoints, expressed as cases/100 patient-months, were: incidence of hospital admission; antibiotic therapy; bloodstream infection (BSI); and VAS infection. These were compared to Centers for Disease Control (CDC) surveillance data, overall and by VAS type. In total, 2568 patient-months were analysed. The VAS distribution differed significantly from CDC data for fistulas (72% vs. 31%), grafts (12% vs. 41%), cuffed catheters (11% vs. 25%) and non-cuffed catheters (5% vs. 3%) (p < 0.0001 in all cases). Of 151 admissions, 32% resulted from infection, for which 112 antibiotic courses (22% vancomycin) were given. There were 16 BSIs, three involving resistant strains. The incidences of admission, antibiotic therapy, BSI and VAS infection were significantly lower overall, compared to CDC rates, as were most VAS-specific endpoints. These differences may be explained by VAS type distribution, although other factors may also be involved. Reporting regional or national surveillance data may allow a standardised comparison of the incidence of HD-associated infections.

Intraocular pressure during haemodialysis: a review

OBJECTIVES

Although several works in the past have examined the effect of haemodialysis (HD) on intraocular pressure (IOP), reported findings, theories, and conclusions are very different. The objectives of this article are to resume the reported evidence of IOP changes during HD, to review the proposed hypothesis of HD influence on IOP, and to determine if ophthalmic examination is imperative in HD patients.

METHODS

We analysed the peer-reviewed English literature and selected all possible relevant articles.

RESULTS

The influence of HD on IOP is not clear, and even in recent studies opposite findings can be found.

CONCLUSIONS

Future studies are needed to clarify the effects of HD on IOP. In patients with glaucoma or with predisposed narrow angles, or eyes with impaired aqueous outflow, the possibility of acute IOP rise during HD could be much more frequent than in normal patients. So in these patients, a more strict ophthalmic scheduled examination seems to be feasible.

Hepatitis C virus infection in renal failure patients in the absence of anti-hepatitis C virus antibodies

The magnitude and clinical significance of Hepatitis C virus (HCV) infection in dialysis patients is controversial and underestimated. This study was conducted in order to evaluate the correlation between HCV replication and antibody response to HCV in dialysis patients. HCV infection in dialysis patients was evaluated over a period of 3 years and compared to HCV infection in Liver Clinic patients. Sera were collected from 310 dialysis patients and tested for anti-HCV and HCV-RNA. In addition, HCV genotype and HCV viral load were determined in HCV-RNA-positive sera. Anti-HCV was detected in 43 (14%) of the dialysis patients. Of these, 37 (86%) were HCV-RNA-positive. Among the 267 HCV-seronegative dialysis patients, 25 (9%) were found to be HCV-RNA-positive in more than one sample during the study. These patients were characterized by low viral load; at least two orders of magnitude lower than in the group of HCV-seropositives. In contrast, in the Liver Clinic patients, HCV-RNA was found exclusively in HCV-seropositive patients. Comparison of the genotype pattern in the two groups did not reveal a difference. Our results suggest that HCV infection in dialysis units may be underestimated due to cases of low viral load, depending on the method of RNA extraction and sensitivity of the test used. Low viral load might contribute to the lack of humoral immune response seen in some dialysis patients.

Intradialytic hypercapnic respiratory failure managed by noninvasive assisted ventilation

We report a hemodialysis patient with acute hypercapnic respiratory failure managed on noninvasive intermittent positive pressure ventilation and progressive metabolic acidosis. Dialysate bicarbonate concentration of 25 mEq/l was associated with exacerbation of metabolic acidosis, while higher dialysate bicarbonate concentration of 30 mEq/l induced a dangerous increase in PCO(2) level. Excessive bicarbonate buffering and CO(2) production induced by severe metabolic acidosis, malnourishment and tissue hypoxia, could explain inadequate correction of metabolic acidosis and worsening of hypercapnia in this patient. Our findings suggest the need for close monitoring of blood gases and cautious modulation of dialysate bicarbonate concentration in the presence of progressive metabolic acidosis in hypercapnic hemodialysis patients.

High incidence of severe twin hemodialysis catheter infections in elderly women. Possible roles of insufficient nutrition and social support

BACKGROUND

Cuffed-tunneled hemodialysis (HD) catheters are recommended as a bridging therapy until peripheral access is available, but their long-term use is controversial.

AIM

To evaluate the complications and lifetime of twin-tunneled HD catheters and to identify parameters which could predict their outcome.

METHODS

29 chronic HD patients (19 female and 10 male) were inserted with twin hemodialysis catheters (28 Tesio, 1 Schon Duoflow), followed for up to 9 months or until catheter loss, and evaluated for severe catheter-related complications necessitating catheter removal. Since the most common severe complication was catheter-related infection, we retrospectively examined whether parameters such as age, gender, duration of end-stage renal disease, delivered dose of dialysis, nutrition, diabetes and indices of social support correlate with this outcome.

RESULTS

Severe catheter infection requiring catheter removal occurred in 11 patients (10 female). Of these infected female patients, 9 were elderly (> or =67 years) and in 6 of those, catheter infection was fatal (54% of infected cases). At 9 months, severe catheter infection and related patient death rates were 38 and 21%, respectively. Severe catheter infection was significantly related to less social support (p < 0.005), older age, female gender, lower nPCR (all p < 0.05), and tended to be related to shorter end-stage renal disease duration prior to catheter insertion (p = 0.06).

CONCLUSION

This study demonstrated that twin HD catheters are associated with a high incidence of severe catheter-related infections which was most significantly related to social-support as well as inadequate nutrition, older age and female gender. Therefore, we suggest early removal of the catheter, enhancement of social support and dietary counseling for the elderly and lonely HD patients using this type of catheter.

Renal transplant dysfunction due to severe aorto-iliac atherosclerosis in the presence of patent renal transplant artery

We report a case of progressive deterioration in renal function and decreased renal graft perfusion induced by extensive aorto-iliac atherosclerotic lesions proximal to a patent renal graft artery. Significant improvement in kidney graft function followed left axillo-femoral bypass graft surgery, which to the best of our knowledge, has never been performed previously for permanent maintenance of renal transplant perfusion.

Pediatric urolithiasis in southern Israel: the role of uricosuria

We describe three cases of severe obstructive uropathy in children under 2 years of age, due to radiolucent renal stones. Metabolic work-up revealed only normouricemic hyperuricosuria (HU) as the single identifiable risk factor for urolithiasis (UL) in these infants. We reviewed records of 66 cases of pediatric UL seen in our service over an 8-year period. UL prevalence was greater for Bedouin than for Jewish children (1.02 vs. 0.13 cases/1,000 inhabitants at risk respectively, P<0.01). HU (>0.6 mg uric acid/dl GFR) was the only biochemical risk factor that differed between Bedouin and Jewish children (mean uric acid excretion index 0.8+/-0.39 vs. 0.55+/-0.26 mg/dl GFR respectively, P<0.05). Bedouin children comprised 85% of patients in the HU group versus 59% in the non-hyperuricosuric group (P<0.05). The mean age of onset of UL was 38+/-44 months and 93+/-52 months in the HU and the non-HU group, respectively (P<0.05). The UA excretion index in the HU group was inversely correlated with age (r=0.41, P<0.01) and its slope and constant were different from an age-matched non-UL control population. In conclusion, pediatric UL in southern Israel is predominant in Bedouin toddlers. HU was the only identifiable biochemical risk factor that could explain this difference.

Effectiveness of erythropoiesis on supervised intradialytic oral iron and vitamin C therapy is correlated with Kt/V and patient weight

BACKGROUND

Poor compliance to oral medication and diet is common in hemodialysis (HD) patients and limits the ability of oral iron therapy to support erythropoiesis. Intravenous (i.v.) iron may be associated with undesirable and sometimes life-threatening complications.

PATIENTS AND METHODS

We hypothesized that intradialytic oral iron therapy can overcome compliance problems and support effective maintenance erythropoiesis, which will keep Hct in the range of 33% to 36% and EPO requirements up to 50 units/week/kg. In a prospective observational study, SC EPO-treated hospital-based HD patients without conditions known to cause EPO resistance, were managed on intradialytic oral administration of iron and vitamin C. The primary endpoints were EPO requirements and resistance to EPO which standardized EPO requirements by the Hct level. Secondary endpoints included parameters that might affect the primary endpoints. Exclusion criteria were refusal to take oral medication, prestudy Hct < 27%, recent i.v. iron therapy or transfusions, bleeding, clinical conditions obligating Hct > 30% and known causes of EPO resistance. Twelve patients completed minimal follow-up period of 9 months.

RESULTS

Mean Hct was 34.4% (range: 31.8% - 40.2%). EPO requirements were 61.7 +/- 28.2 units/kg and below 52.5 units/kg in 50% of patients. Patients were classified into equal groups according to resistance to EPO, which was positively correlated (r = 0.71 p < 0.01) with body weight and Kt/V (r = -0.38, p < 0.05).

CONCLUSION

In conclusion, intradialytic oral iron therapy can support effective maintenance erythropoiesis in 50% of patients without known causes for EPO resistance. High response to EPO and low EPO requirement are correlated with lower body weight and possibly improved dialysis.

Unilateral acute renal cortical necrosis: correlative imaging

Bilateral acute cortical necrosis is a rare form of acute renal failure characterized by necrosis of the renal cortex and sparing of the medulla. Little information on the imaging presentation of bilateral acute renal cortical necrosis is available. The enhanced CT appearance is pathognomonic and diagnostic. The unilateral presentation of acute cortical necrosis is extremely rare, and no imaging methods have been described. The authors chose to apply scintigraphic evaluation to this unique condition complementary to CT to confirm the diagnosis. Mercaptoacetylglycine (T3) was selected to assess tubular damage, in contrast to the pure glomerular agent DTPA. Evidence of some tubular function and clear delineation of the shrunken kidney was found. Conversely, in the DTPA study the kidney was not visualized. A DMSA scan was performed for assessment of viability of the renal cortex and showed a photopenic halo around the small area of the viable cortex of the upper pole. The halo sign represents a cortical loss. The visualization of the upper pole as evidence of cortical viability as a consequence of collateral blood flow from capsular vessels was seen on angiography. Radiographic and scintigraphic correlation of this rare condition may be an effective means to confirm the diagnosis and to establish the extent of involvement. However, contrast CT remains the preferred method in the diagnosis of acute cortical necrosis.

Severe interstitial nephritis in a patient with renal amyloidosis and exacerbation of Crohn's disease

A 57-year-old man with long-term untreated Crohn's disease presented with exacerbation of his bowel disease, volume depletion, nephrotic syndrome and rapid decline in renal function. Renal biopsy revealed amyloidosis and extensive interstitial infiltration. Initiation of steroid therapy was associated with improvement in renal function and postponement of dialysis, suggesting that control of interstitial inflammation might have a therapeutic role in renal amyloidosis. We hypothesize that volume depletion could magnify toxicity of proteinuria, thus augmenting interstitial inflammation and accelerating the deterioration in renal function.

[Transmission of hepatitis C in hemodialysis patients--does one-time exposure result in chronic hepatitis?]

Acquired infection with hepatitis C virus (HCV) in hemodialysis patients has been described lately. In dialysis units in Italy and France, the prevalence and incidence of HCV are 20-60% and 1-2%, respectively. Most infected patients develop chronic hepatitis. The clinical presentation of acute HCV in hemodialysis patients is very mild and therefore the diagnosis is often made only by laboratory tests. Acute infection is usually followed by mild elevation of liver enzymes and the presence of HCV-RNA and anti-HCV in serum. We report a 48-year-old man on hemodialysis who developed acute hepatitis C. The diagnosis was made by finding mild elevation of liver enzymes and the presence of HCV-RNA in his serum. A few months later, he developed severe hepatitis which was followed by rapid deterioration in liver function. However, the virus was eradicated and liver function tests became normal. Surprisingly, serum anti-HCV antibodies were detected 5 months later.

Media acidification inhibits TGF beta-mediated growth suppression in cultured rabbit proximal tubule cells

Chronic metabolic acidosis induces both hyperplastic and hypertrophic renal growth and is associated with progressive loss of renal function. These studies examine the direct effect of media acidification on the growth of rabbit proximal tubule cells in primary culture. The results demonstrate that media acidification has a direct antiproliferative (hypoplastic) effect on both quiescent and mitogen-stimulated [epidermal growth factor (EGF)-stimulated] cells and does not induce hypertrophy. This direct antiproliferative effect of acid is associated with inhibition of EGF-induced phosphorylation of the retinoblastoma protein (pRB), which maintains pRB activity and inhibits cell cycle progression from G1 to S phase. Transforming growth factor-beta (TGF-beta) alone has an antiproliferative effect in these cells. TGF-beta converts EGF-induced hyperplasia to hypertrophy and inhibits EGF-induced pRB phosphorylation. Media acidification inhibits both the antiproliferative effect of TGF-beta and the ability of TGF-beta to convert EGF-induced hyperplasia to hypertrophy. This activity is associated with inhibition of TGF-beta-mediated retention of pRB in the active, hypophosphorylated state. These results demonstrate that metabolic acidosis has a direct growth-suppressive effect on renal epithelial cells but inhibits the growth-suppressive effects of TGF-beta. Inhibition of the antiproliferative effect of cytokines, such as TGF-beta, may be responsible for acidosis-induced hyperplasia in vivo.

Adriamycin nephropathy: a model to study effects of pregnancy on renal disease in rats

The influence of pregnancy on the evolution of primary renal disease is still a matter of controversy. Hypertension and derangement of renal function may occur. The pathophysiology of these complications is poorly understood. In the present study, we assessed the influence of pregnancy on the evolution of adriamycin (Adr) nephropathy. Four groups of animals were studied: 1) control virgin rats (C), 2) normal pregnant rats (NP), 3) virgin rats with nephropathy (Adr), and 4) pregnant rats with nephropathy (Adr-P). Inulin clearance measured at the end of pregnancy in awake rats was similar in NP (1.68 +/- 0.20 ml/min) and C (1.39 +/- 0.03 ml/min). In Adr-P rats, it tended to decrease (1.22 +/- 0.7 vs. 1.93 +/- 0.44 ml/min in Adr rats). Mean arterial pressure was increased in Adr-P rats (137 +/- 2.5 vs. 95 +/- 3.2 mmHg in NP; P < 0.001). Urinary protein excretion was 216 +/- 61 mg/day in Adr-P compared with 28.7 +/- 18 mg/day in Adr (P < 0.001). A significant increase in the glomerular thromboxane B2-to-prostaglandin E2 ratio was found in Adr-P rats (1.15 +/- 0.26 vs. 0.52 +/- 0.12 in Adr rats; P < 0.03). In NP rats, no change was observed. Kidneys and placentas were normal on light and electron microscopy. Thus pregnant rats with adriamycin nephropathy developed a clinical picture with several features of preeclampsia. Changes in glomerular prostanoid synthesis might play a role in the development of this complication.

Bile salts, hypotension and obstructive jaundice

We have examined the effects of bile duct ligation on vascular and extravascular smooth muscle responsiveness to noradrenaline and tyramine using isolated rat hindlimb perfusion, and portal vein and vas deferens preparations. Bile duct ligation reduced the contractile responses to noradrenaline of vascular and extravascular smooth muscle. Exposure of smooth muscle to some bile salts caused a reduction in contractility. This effect was dependent upon bile salt type and concentration. These studies in vitro suggest that the reduced total peripheral resistance and hypotension seen in obstructive jaundice cannot be explained by a spasmolytic effect of some of the bile salts on smooth muscle.