Measurement of Hemodynamic and Anatomic Parameters in a Swine Arteriovenous Fistula Model

Purpose

Although arteriovenous fistulae (AVFs) are currently the preferred mode of permanent hemodialysis access they do have significant problems due to initial non-maturation and a later venous stenosis. These problems appear to have been exacerbated following a push to increase AVF prevalence in the US. The reasons for both AVF non-maturation and the later venous stenoses are unclear but are thought to be related to abnormal hemodynamic wall shear stress (WSS) profiles. This technical note aims to describe the successful development of measurement techniques that can be used to establish a complete hemodynamic profile in a pig model with two different configurations of AVF.

Methods and results

The curved and straight AVF configurations were created in an in vivo pig model. Flow and pressure in the AVFs were measured using the perivascular flow probes and Doppler flow wires while the pressure was recorded using a pressure transducer. The anatomical configuration was obtained using two different approaches: a) combination of intravascular ultrasound (IVUS) and angiograms, (b) 64 slice CT angiography. 3D models were reconstructed using image processing and computer modeling techniques. Numerical calculations were then performed by applying the measured flow and pressure data into the configurations to obtain the hemodynamic WSS profiles.

Conclusion

The described methodologies will allow the calculation and optimization of WSS profiles in animal models. This information could then be translated to the clinical setting where it would have a positive impact on improving the early maturation rates of AVFs as well as reducing the late venous stenoses.

Prospective iterative trial of proteasome inhibitor-based desensitization

A prospective iterative trial of proteasome inhibitor (PI)-based therapy for reducing HLA antibody (Ab) levels was conducted in five phases differing in bortezomib dosing density and plasmapheresis timing. Phases included 1 or 2 bortezomib cycles (1.3 mg/m(2) × 6-8 doses), one rituximab dose and plasmapheresis. HLA Abs were measured by solid phase and flow cytometry (FCM) assays. Immunodominant Ab (iAb) was defined as highest HLA Ab level. Forty-four patients received 52 desensitization courses (7 patients enrolled in multiple phases): Phase 1 (n = 20), Phase 2 (n = 12), Phase 3 (n = 10), Phase 4 (n = 5), Phase 5 (n = 5). iAb reductions were observed in 38 of 44 (86%) patients and persisted up to 10 months. In Phase 1, a 51.5% iAb reduction was observed at 28 days with bortezomib alone. iAb reductions increased with higher bortezomib dosing densities and included class I, II, and public antigens (HLA DRβ3, HLA DRβ4 and HLA DRβ5). FCM median channel shifts decreased in 11/11 (100%) patients by a mean of 103 ± 54 mean channel shifts (log scale). Nineteen out of 44 patients (43.2%) were transplanted with low acute rejection rates (18.8%) and de novo DSA formation (12.5%). In conclusion, PI-based desensitization consistently and durably reduces HLA Ab levels providing an alternative to intravenous immune globulin-based desensitization.

Combining novel technologies with improved logistics to reduce hemodialysis vascular access dysfunction

Hemodialysis (HD) vascular access dysfunction is currently a huge clinical problem for which there are no effective therapies. There are, however, a number of promising technologies that are currently at the experimental or clinical trial stage. We believe that the application of these novel technologies in combination with better clinical protocols for vascular access care could significantly reduce the current problems associated with HD vascular access.

Reducing de novo donor-specific antibody levels during acute rejection diminishes renal allograft loss

The effect of de novo DSA detected at the time of acute cellular rejection (ACR) and the response of DSA levels to rejection therapy on renal allograft survival were analyzed. Kidney transplant patients with acute rejection underwent DSA testing at rejection diagnosis with DSA levels quantified using Luminex single-antigen beads. Fifty-two patients experienced acute rejection with 16 (31%) testing positive for de novo DSA. Median follow-up was 27.0 +/- 17.4 months postacute rejection. Univariate analysis of factors influencing allograft survival demonstrated significance for African American race, DGF, cytotoxic PRA >20% (current) and/or >50% (peak), de novo DSA, C4d and repeat transplantation. Multivariate analysis showed only de novo DSA (6.6-fold increased allograft loss risk, p = 0.017) to be significant. Four-year allograft survival was higher with ACR (without DSA) (100%) than mixed acute rejection (ACR with DSA/C4d) (65%) or antibody-mediated rejection (35%) (p < 0.001). Patients with >50% reduction in DSA within 14 days experienced higher allograft survival (p = 0.039). De novo DSAs detected at rejection are associated with reduced allograft survival, but prompt DSA reduction was associated with improved allograft survival. DSA should be considered a potential new end point for rejection therapy.

Measurement of hemodynamic and anatomic parameters in a swine arteriovenous fistula model

PURPOSE

Although arteriovenous fistulae (AVFs) are currently the preferred mode of permanent hemodialysis access they do have significant problems due to initial non-maturation and a later venous stenosis. These problems appear to have been exacerbated following a push to increase AVF prevalence in the US. The reasons for both AVF non-maturation and the later venous stenoses are unclear but are thought to be related to abnormal hemodynamic wall shear stress (WSS) profiles. This technical note aims to describe the successful development of measurement techniques that can be used to establish a complete hemodynamic profile in a pig model with two different configurations of AVF.

METHODS AND RESULTS

The curved and straight AVF configurations were created in an in vivo pig model. Flow and pressure in the AVFs were measured using the perivascular flow probes and Doppler flow wires while the pressure was recorded using a pressure transducer. The anatomical configuration was obtained using two different approaches: a) combination of intravascular ultrasound (IVUS) and angiograms, (b) 64 slice CT angiography. 3D models were reconstructed using image processing and computer modeling techniques. Numerical calculations were then performed by applying the measured flow and pressure data into the configurations to obtain the hemodynamic WSS profiles.

CONCLUSION

The described methodologies will allow the calculation and optimization of WSS profiles in animal models. This information could then be translated to the clinical setting where it would have a positive impact on improving the early maturation rates of AVFs as well as reducing the late venous stenoses.

The native arteriovenous fistula in 2007. Research needs

Several research questions are open in the field of vascular access for hemodialysis. The present paper reviews both prognostic issues, such as the identification of factors for patient stratification before access insertion, and intervention questions, such as comparison of the advantages and disadvantages of different surgical solutions, the effects of different medications on vascular pathology, the different cannulation practices to prevent vessel wall lesions and technologies for early diagnosis of access dysfunction. Given that the quality of the available literature in nephrology is often suboptimal, nephrologists need to pay special attention to methodology issues before embarking on expensive multicenter studies.

The native arteriovenous fistula in 2007. Surveillance and monitoring

In the past 5 years, some clinical trials have questioned the value of surveillance in managing vascular accesses. Although prolongation of access life span is an important end point, reduction of thrombotic events reduces patient risks resulting from loss of access patency. Most of the available evidence suggests that detection of stenosis and prevention of thrombosis is valuable. When a test indicates the likely presence of a stenosis, then venography or fistulography should be used to definitively establish the presence and degree of the stenosis. In most but not all cases, angioplasty should be performed if the stenosis is greater than 50% by diameter. The value of routine use of any surveillance technique for detecting anatomic stenosis alone, without concomitant functional assessment by measurement of access flow, venous pressure, recirculation or other physiologic parameters, has not been established. Stenotic lesions should not be repaired merely because they are present. If such correction is performed, then intraprocedural or periprocedural measurement of access flow (QA) or intra-access pressure should be conducted to demonstrate a functional improvement with a successful percutaneous transluminal angioplasty.

In vitro Paclitaxel and Radiation Effects on the Cell Types Responsible for Vascular Stenosis: A Preliminary Analysis

Hemodialysis vascular access dysfunction as a result of venous neointimal hyperplasia in dialysis access grafts and fistulae is currently a huge clinical problem. The aim of this study was to assess the effects of paclitaxel and radiation, both singly and in combination on the proliferation of cell types present within the lesion of venous neointimal hyperplasia (vascular smooth muscle cells, fibroblasts and endothelial cells within the neointimal microvessels). Vascular smooth muscle cells, fibroblasts and endothelial cells were plated onto 96-well plates and exposed to different concentrations and doses of paclitaxel and radiation, respectively (both individually and in combination). Growth inhibition was assessed with an MTT assay. Both paclitaxel and radiation resulted in significant growth inhibition of all three cell types. However, even small doses of paclitaxel appeared to attenuate the antiproliferative effect of radiation on these cell types. Further experiments to elucidate the mechanism behind these findings could result in a better understanding of combination antiproliferative therapies.

BRAVO I: A pilot study of vascular brachytherapy in polytetrafluoroethylene dialysis access grafts

Hemodialysis vascular access dysfunction owing to stenosis and thrombosis in polytetrafluoroethylene dialysis access grafts is a huge clinical problem for which there are currently no long lasting durable therapies. Vascular brachytherapy has been used successfully for the prevention of coronary restenosis following angioplasty and stent placement. The Beta Radiation for Treatment of Arterial-Venous Graft Outflow I study was a pilot study of vascular brachytherapy in hemodialysis patients with patent but dysfunctional grafts. Twenty-five patients were randomized to receive either radiation therapy (a single dose of 18.4 Gy) or sham radiation, following angioplasty. The primary efficacy end point of the study was target lesion primary patency at 6 months. The primary safety end point was a composite of death, emergency surgery on the graft, venous rupture, or aneurysm formation. Forty-two percent of the radiated grafts achieved the target lesion primary patency end point at 6 months as compared to 0% of the control group (P = 0.015), but this did not translate into an improvement in secondary patency at either 6 or 12 months. Radiation therapy was found to be safe in the setting of hemodialysis vascular access dysfunction. Our results suggest that vascular brachytherapy is an intervention that is worthy of further examination in the setting of non-thrombosed dialysis access grafts.

Histocompatibility testing predicts acute rejection risk in early corticosteroid withdrawal regimens

Histocompatibility testing has been shown to predict acute rejection risk in steroid-based immunosuppression. However, little evidence exists of its ability to predict acute rejection risk in corticosteroid-free patients, with no evidence in early corticosteroid withdrawal (CSWD) under modern immunosuppression. The purpose of this study was to evaluate the ability of histocompatibility testing to identify patients at high risk for acute rejection after early CSWD.

METHODS

One hundred eighty-one patients were entered into six IRB-approved early CSWD regimens. Histocompatibility testing included serologic PRA, flow cytometric PRA testing by Class I and Class II MHC beads, and B cell crossmatching with pronase treatment. All rejection episodes were biopsy proven, and grading was assigned using Banff criteria. Influence of individual tests was examined using Chi square univariate and multivariate logistic regression analysis.

RESULTS

Median follow-up was 23.5 months (range 7-48 months). Of 181 patients, 16% were repeat transplant recipients, 36% received deceased donor renal transplants, 48% received living related donor renal transplants, and 16% received living unrelated transplants. Overall patient survival was 97%, and death-censored graft survival was 96.5%. Acute rejection rates in the entire follow-up period were 17.7%. 12.4% in primary transplant recipients and 37% in repeat transplant recipients. Multivariate analysis revealed that HLA AB and DR locus mismatching were associated with increased acute rejection risk. Similarly, serologic PRA analysis predicted acute rejection risk; however, flow cytometry crossmatching did not predict acute rejection risk. The greatest single influence on acute rejection risk appeared to be a flow cytometric B cell crossmatch (7.94-fold increased risk). In conclusion, histocompatibility testing can identify patients at high risk for acute rejection following early CSWD. HLA matching, serologic PRA testing, and flow cytometry-based B cell crossmatching can all be used to predict acute rejection risk.

Posttransplant lymphoproliferative disorder: significance of central nervous system involvement

BACKGROUND

Few data exist regarding central nervous system (CNS) involvement in patients with posttransplant lymphoproliferative disorder (PTLD). The purpose of this study was to review the Israel Penn International Transplant Tumor Registry (IPITTR) experience with CNS involvement by PTLD.

METHODS

Nine hundred ten PTLD cases from the United States were reported to the IPITTR and reviewed for CNS involvement.

RESULTS

One hundred thirty-six transplant recipients with PTLD (15%) had CNS involvement. The highest incidence of CNS involvement occurred in pancreas (3 of 11; 27%) and kidney transplant recipients (76 of 429; 18%). Fifteen cases occurred in children and 121 cases in adults. For both children and adults, isolated CNS disease was associated with better survival when compared with multiple-site involvement (children: 29% vs 0%; adults: 12% vs 6%; P < .05). Three-year survival in PTLD patients with CNS involvement was 9.4% and without CNS involvement was 49.4% (P < .01). Radiation therapy alone appeared to provide the best survival rates (25%).

CONCLUSIONS

CNS involvement in transplant recipients with PTLD carries an ominous prognosis; however, isolated CNS involvement has a better prognosis than CNS plus extracranial involvement. Radiation therapy alone provides the best results, but this may be a reflection of isolated CNS disease.

Early steroid withdrawal does not increase risk for recurrent focal segmental glomerulosclerosis

Experience with early corticosteroid withdrawal (CSWD) in renal transplant recipients with focal segmental glomerulosclerosis (FSGS) has not been previously reported. Since corticosteroids are used to treat primary FSGS, concern exists as to whether early CSWD regimens will be associated with an increased risk of FSGS recurrence posttransplant. The purpose of the present study was to evaluate the results of early CSWD in FSGS recipients and compare these results to a historic control group of FSGS patients who underwent renal transplantation under corticosteroid-based immunosuppression.

METHODS

Forty-three patients with FSGS underwent renal transplantation with early CSWD. Results in these patients were compared to FSGS patients that underwent renal transplantation with chronic corticosteroid therapy. All rejection episodes were biopsy proven with grading by Banff criteria. Statistical analyses included Student's t test and chi square tests.

RESULTS

Results in 43 patients with a median follow-up of 569 days were analyzed and compared to control patients. There was no significant difference in recurrent FSGS, time to recurrence, or graft loss.

CONCLUSION

CSWD does not increase risk for recurrence of FSGS. These observations indicate that ECSW can be achieved in FSGS patients, thereby affording them the benefits of steroid elimination.

A prospective, pilot study of early corticosteroid cessation in high-immunologic-risk patients: the Cincinnati experience

BACKGROUND

The first prospective trial of steroid withdrawal dedicated to high-immunologic-risk patients is reported herein.

METHODS

Twenty-five patients were enrolled prospectively in an IRB-approved HIPAA-compliant protocol. Immunosuppression included corticosteroid withdrawal (CSWD) at 7 days, tacrolimus (target trough level 4 to 8 ng/mL), sirolimus (target trough level 8 to 12 ng/mL), and Mycophenolate Mofetil (2 g/d). Induction with daclizumab (2 mg/kg) on posttransplant days (PTD) 0 and 14 was administered to the first 10 patients. The protocol for the next 15 patients was modified because of high acute rejection rates to include received T-cell-depleting antibody induction therapy with thymoglobulin (1.5 mg/kg) on PTDs 0 and 2 followed by daclizumab on Postoperative day (POD) 14. Recipient inclusion criteria included: (1) repeat transplant recipients; or (2) patients with a peak PRA > or =25%. All rejection episodes were diagnosed by biopsy and graded using Banff '97 criteria.

RESULTS

Twenty-five patients were enrolled and median follow-up was 402 days. Forty percent of recipients were black, 68% of patients were repeat transplant recipients, 68% received deceased donor kidneys, and 36% had a peak flow PRA >25%. Overall acute rejection, graft survival, and patient survival rates of 40%, 88%, and 96%, respectively, were observed for the duration of the study. Acute rejection occurred in 6 of 10 patients (60%) with daclizumab induction; however, acute rejection rates fell to 27% when thymoglobulin was introduced (P = .1).

CONCLUSIONS

This study supports our previous observations in a multivariate analysis of early CSWD patients, wherein polyclonal antibody induction therapy reduced acute rejection. High-immunologic-risk patients may be able to undergo early CSWD with acceptable rates of acute rejection.

Corticosteroid avoidance ameliorates lymphocele formation and wound healing complications associated with sirolimus therapy

INTRODUCTION

Sirolimus (RAPA) and corticosteroids (CS) both inhibit wound healing. To evaluate the possibility that RAPA and CS have additive effects on wound healing, we evaluated the effects of corticosteroid avoidance (CSAV) on wound healing complications in patients treated with RAPA.

METHODS

One hundred nine patients treated with a CSAV regimen (no pretransplantation or posttransplantation CS) were compared with a historical control group (n = 72) that received cyclosporine (CsA), mycophenolate mofetil (MMF), and CS. The CSAV group received low-dose CsA, MMF, RAPA, and thymoglobulin induction. Complications were classified as follows: wound healing complications (WHC) or infectious wound complications (IWC). WHC included lymphocele, hernia, dehiscence, diastasis, and skin edge separation. IWC included wound abscess and empiric antibiotic therapy for wound erythema.

RESULTS

The CSAV group was largely CS-free: 11% of patients received CS for rejection, 12% of patients received CS for recurrent disease, and 85% of patients are currently off CS. The CSAV group had a significantly lower incidence of WHC (13.7% vs 28%; P = .03) and lymphoceles (5.5% vs 16%; P = .02) than the control group. There was no difference in the incidence of IWC between the 2 groups. Patients who received CSAV were 18% less likely (P = .57) to develop any type of complication, 41% less likely (P = .20) to develop a WHC, and 71% less likely (P = .018) to develop a lymphocele.

CONCLUSIONS

CSAV in a RAPA-based regimen results in a marked reduction in WHC and lymphoceles. Therefore, CSAV provides a promising approach for addressing WHC associated with RAPA therapy.

Early corticosteroid withdrawal under modern immunosuppression in renal transplantation: multivariate analysis of risk factors for acute rejection

Early corticosteroid withdrawal has been shown to be effective in low-risk patient populations in a number of US and European multicenter trials. However, patient populations traditionally considered to be at high risk for acute rejection (eg, African Americans, repeat transplant recipients, sensitized patients) are usually excluded from these trials. Since our initial experience with early withdrawal almost 10 years ago, we have included high-immunologic-risk patients. We have accumulated enough high-risk patients with early withdrawal to allow the first multivariate analysis of risk factors for acute rejection in early withdrawal under modern immunosuppression.

METHODS

Early withdrawal was performed under prospective IRB-approved protocols. Statistical analysis included chi square test and logistic regression. All rejection episodes were biopsy proven and graded by Banff 1997 criteria.

RESULTS

A total of 164 patients underwent early withdrawal: 82% had at least one mismatched DR antigen, 17% had delayed graft function, 33% were African American, and 18% were repeat transplant recipients. Multivariate analysis of risk factors for acute rejection indicated that two factors induced a statistically significant alteration in acute rejection risk: repeat transplant recipients (4.3-fold increased risk) and thymoglobulin induction (0.30 risk (ie, 70% reduction in risk compared to patients not receiving thymoglobulin induction). Sensitized recipients and African Americans were also at increased risk but did not quite reach statistical significance. These data strongly support the use of T-cell depleting antibody induction therapy in high-risk patients undergoing early withdrawal under modern immunosuppression.

Body Weight Alterations Under Early Corticosteroid Withdrawal and Chronic Corticosteroid Therapy With Modern Immunosuppression

Weight gain is a well-known complication of corticosteroid maintenance therapy. The purpose of our study was to compare patterns of weight gain under chronic corticosteroid therapy (CCST) to those observed under early corticosteroid withdrawal (CSWD) in renal transplant recipients.

METHODS

Renal transplant recipients who underwent early CSWD in IRB-approved prospective trials were compared to a historical control group of patients receiving CCST who were matched for age, sex, and race.

RESULTS

One hundred sixty-nine patients with early CSWD were compared to 132 patients who received CCST. Mean population weight gain was significantly higher in CCST patients at 12 months (5.52 kg vs 3.05 kg, P < .05) posttransplant. Caucasian CSWD patients demonstrated a greater reduction in weight gain with CSWD than African Americans (mean weight decrease 2.9 vs 1.9 kg/patient, P < .05). Patients who were overweight (body mass index [BMI] 25-30) or obese (BMI > 30) demonstrated a greater reduction in weight gain with CSWD at 1 year (mean reduction in weight gain with CSWD 5.3 kg/patient and 4.4 kg/patient) than did patients of normal weight (BMI < 25; 0.1 kg/patient, P < .01 and <.05 versus BMI < 25).

CONCLUSIONS

Early CSWD patients gain significantly less weight than CCST patients following transplantation. Marked variations in the effect of early CSWD on weight gain may be observed due to race and pretransplant BMI. Caucasians and overweight patients demonstrate greater benefits from CSWD than African Americans and patients with normal BMI.

Global Cardiovascular Risk Under Early Corticosteroid Cessation Decreases Progressively in the First Year Following Renal Transplantation

A primary reason to eliminate corticosteroids from immunosuppressive regimens in solid organ transplant recipients is improved cardiovascular risk profiles. Although a number of studies have documented that corticosteroid withdrawal (CSWD) regimens reduce hypertension, hyperlipidemia, diabetes, and weight gain, global assessments of cardiovascular risk under CSWD have not been reported. The purpose of this study was to document cardiovascular risk under CSWD using a global risk assessment by Framingham risk assessment.

METHODS

Framingham global cardiovascular risk assessments were performed at baseline and 3, 6, and 12 months posttransplant on patients enrolled in prospective, IRB-approved early (<7 days of corticosteroids) CSWD trials. Framingham score was based on age, sex, presence of diabetes, HDL and total cholesterol, and systolic blood pressure. All patients were nonsmokers. Left ventricular hypertrophy assessment by EKG criteria was not available at all time points and therefore were not included.

RESULTS

One hundred eighty-three patients were included in the analysis. Fourteen percent of patients had evidence of coronary heart disease (prior MI, CABG, PTCA, or significant cardiovascular disease as evidenced by angiography) prior to transplant. Complete information was available for 160 patients at baseline, 132 at 1, 3, and 6 months, and 93 at 12 months posttransplant. Mean 10-year risk (expressed as percent) for developing coronary heart disease decreased over time: 8.03 at baseline, 8.31 at 3 months, 7.40 at 6 months, and 7.20 at 12 months, indicating that global cardiovascular risk fell at 1 year posttransplant by about 10% in renal transplant recipients undergoing early CSWD.

CONCLUSIONS

Estimation of cardiovascular risk by Framingham risk factor assessment allows incorporation of several cardiovascular risk factors into a single estimate, thereby accounting for differential effects of each individual factor on global cardiovascular risk. This experience indicates that global cardiovascular risk decreases by approximately 10% at 1 year posttransplant in renal transplant recipients who undergo early corticosteroid withdrawal (CSWD).

Pilot Study of Early Corticosteroid Elimination After Pancreas Transplantation

Early corticosteroid withdrawal has recently been shown to be possible in recipients of simultaneous pancreas kidney transplants; however, its feasibility in solitary pancreas recipients has not been documented. In the present study, we provide evidence that early withdrawal can be achieved in pancreas as well as pancreas-kidney recipients.

METHODS

Twenty type I diabetics underwent 13 pancreas-kidney transplants and 7 pancreas-only transplants with early withdrawal (methylprednisone 6-day taper). Additional immunosuppression consisted of tacrolimus, mycophenolate mofetil, and thymoglobulin induction (five doses).

RESULTS

Transplants included 13 pancreas-kidney, 6 pancreas after kidney transplant, and 1 pancreas after islet transplant. Overall mean follow-up was 7.3 months. One episode of pancreas transplant rejection after pancreas-only transplant was detected on protocol biopsy without biochemical abnormalities. One renal allograft rejection occurred 65 days posttransplant in a pancreas-kidney recipient and was graded as a Banff IA rejection. A single pancreas graft loss occurred due to thrombosis 6 days after pancreas-kidney transplantation.

CONCLUSIONS

These results indicate that relatively short thymoglobulin induction (five doses) with tacrolimus and mycophenolate mofetil can allow early withdrawal in both pancreas-kidney and pancreas-only transplant recipients.

Outcomes of Patients With Rejection Post–Polyomavirus Nephropathy

INTRODUCTION

We sought to determine the effects of rejection in renal transplant recipients with polyomavirus nephropathy (PVN).

METHODS

SCr, biopsy findings, BKV serum and urine loads (Taqman PCR), and BKV antibody titers (HA inhibition assay) were analyzed by two-sample median tests and z tests in 11 patients with median follow-up of 7.3 (2.0 to 31.5) months post-PVN. All patients underwent immunosuppression reduction (ISR) as PVN treatment.

RESULTS

Post-PVN, 3 (27%) patients had five rejection episodes, with 80% being mild. Median time to rejection was 18 (2 to 60) weeks. One hundred percent of patients who experienced post-PVN rejection also experienced rejection pre-PVN. Rejection episode treatments consisted of: none in one, increased tacrolimus in two, IVIG in one, IVIG and increased tacrolimus in one. Median viral loads in patients with post-PVN rejection versus those without rejection were not different in serum (2.01 x 10(4) vs 9.00 x 10(4) BKV copies/mL; P = .22) or urine (5.37 x 10(5) vs 8.93 x 10(6) BKV copies/mL; P = .28). Median BKV antibody titers were slightly lower (16384 vs 32768 HA units; P = .02) and median SCr values were significantly higher (2.7 vs 1.9 mg/dL, P = .0003) in patients who had experienced post-PVN rejection. Graft losses occurred in one rejection-free patient (chronic allograft nephropathy) and in one patient who experienced multiple acute rejection episodes, humoral rejection, and worsening PVN.

CONCLUSIONS

Patients who experience rejection prior to PVN are at high risk of developing rejection post-ISR and post-PVN; however, low graft loss rates may still be achieved.

African American Renal Transplant Recipients Benefit From Early Corticosteroid Withdrawal Under Modern Immunosuppression

African Americans have historically been considered high-risk renal transplant recipients due to increased rejection rates and reduced long-term graft survival. Modern immunosuppression has reduced rejections and improved graft survival in African Americans and may allow successful corticosteroid withdrawal. Outcomes in 56 African Americans were compared to 56 non-African Americans enrolled in early withdrawal protocols. Results are reported as African American versus non-African American. Acute rejection at 1 year was 23% and 18% (P = NS), while patient and graft survival was 96% versus 98% and 91% versus 91% (P = NS), respectively. In conclusion, early withdrawal in African Americans is associated with acceptable rejection rates and excellent patient and graft survival, indicating that the risks and benefits of early withdrawal are similar between African Americans and non-African Americans. Additional followup is needed to determine long-term renal function, graft survival, and cardiovascular risk in African Americans with early steroid withdrawal.

Venous neointimal hyperplasia in polytetrafluoroethylene dialysis grafts

BACKGROUND

Vascular access dysfunction is the most important cause of morbidity and hospitalization in the hemodialysis population in the United States at a cost of $1 billion per annum. Venous neointimal hyperplasia (VNH) characterized by stenosis and subsequent thrombosis accounts for the overwhelming majority of pathology resulting in polytetrafluoroethylene (PTFE) dialysis graft failure. Despite the magnitude of the problem and the enormity of the cost ($1 billion), there are currently no effective therapies for the prevention or treatment of venous neointimal hyperplasia in PTFE dialysis grafts.

METHODS

Tissue samples were collected from the graft-vein anastomosis of stenotic PTFE grafts during surgical revision. Specimens were graded using standard light microscopy and immunohistochemistry for the magnitude of neointimal hyperplasia and for the expression of specific cell types, cytokines, and matrix proteins.

RESULTS

VNH was characterized by the (1) presence of smooth muscle cells/myofibroblasts, (2) accumulation of extracellular matrix components, (3) angiogenesis within the neointima and adventitia, and (4) presence of an active macrophage cell layer lining the PTFE graft material. Platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), and vascular endothelial growth factor (VEGF) were expressed by smooth muscle cells/myofibroblasts within the venous neointima, by macrophages lining both sides of the PTFE graft, and by vessels within the neointima and adventitia.

CONCLUSIONS

Our results suggest that macrophages, specific cytokines (bFGF, PDGF, and VEGF), and angiogenesis within the neointima and adventitia are likely to contribute to the pathogenesis of VNH in PTFE dialysis grafts. Interventions aimed at these specific mediators and processes may be successful in reducing the very significant human and economic costs of vascular access dysfunction.

Interleukin-2 and interferon-gamma double knockout mice reject heterotopic cardiac allografts

BACKGROUND

Several studies suggest that MHC-mismatched allografts reject with a Th1 or Th2 immune response, but these models all have low-level expression of the Th1 cytokines interleukin (IL)-2 and interferon-gamma (IFN-gamma).

METHODS

We interbred mice with single targeted gene disruptions for IL-2 and IFN-gamma to establish IL-2 + IFN-gamma double knockout (DKO) mice. Heterotopic cardiac allografts from DBA/2j (H2d) donors were transplanted WT, IL-2 knockout (KO), IFN-gamma KO, and DKO recipients (C57BL/6x129; H2b). Cytokine transcripts from allografts and DKO splenocytes were analyzed by reverse transcription polymerase chain reaction.

RESULTS

DKO mice had a cytokine profile and IgG1/ IgG2a isotype ratio characteristic of Th2 deviation. DKO recipients rejected heterotopic cardiac allografts faster than IL-2 KO mice, but significantly slower than WT and IFN-gamma KO mice (P<0.01). Analysis of the rejecting DKO recipients showed intragraft Th2 cytokine expression.

CONCLUSION

The combined absence of IL-2 and IFN-gamma in the setting of Th2 deviation does not prevent allograft rejection.

IL-2 and IL-4 double knockout mice reject islet allografts: a role for novel T cell growth factors in allograft rejection

T cell growth factors (TCGFs) play a critical role in allograft rejection by promoting the activation and proliferation of alloreactive T cells. To determine whether IL-2 and IL-4 are of quintessential importance in allograft rejection and to identify possible alternative TCGFs, we have bred IL-2(-/-) and IL-4(-/-) double knockout (DKO) mice and studied islet allograft rejection using the DKO mice as allograft recipients. Although mononuclear leukocytes from DKO mice did not mount a proliferative response in vitro in response to anti-CD3 stimulation, crude islet allografts were vigorously rejected by DKO mice (mean survival time 17 +/- 7, n = 8) as compared with wild-type controls (mean survival time 13 +/- 4, n = 7). Treatment of DKO mice with anti-CD3 or rapamycin markedly prolonged the islet allograft survival. An analysis of intragraft cytokine gene transcripts showed robust expression of IL-7 and IL-15. In contrast, intragraft IL-9 gene transcripts were not detected in either wild-type or DKO mice. Provision of exogenous IL-2, IL-4, IL-7, or IL-15, but not IL-9, supports the proliferation of anti-CD3 activated DKO splenic leukocytes in vitro. Blocking the common gamma c of IL-2 receptor, a shared essential signaling component by receptors for IL-2, IL-4, IL-7, IL-9, and IL-15, prolonged the survival of islet allografts in DKO mice. Hence, a T cell dependent allograft rejection enabled by rapamycin-sensitive signals or signals mediated by binding of the gamma c chain occurs in the absence of both IL-2 and IL-4. Non-T cell-derived TCGFs, especially IL-7 and IL-15, may play an active role in supporting allograft rejection.

CTLA4Ig attenuates accelerated rejection (presensitization) in the mouse islet allograft model

BACKGROUND

Sensitization to donor antigens is a problem of growing magnitude in clinical transplantation. At a molecular level, this is due to the interaction between antigen bearing antigen-presenting cells and recipient T cells and involves both antigen presentation and co-stimulation.

METHODS

Allogeneic islet transplantation was performed using DBA/2J donors and B6AF1 recipients. Four weeks before transplantation, recipient animals were given donor-specific transfusion (DST) alone, DST + CTLA4Ig, DST + control IgG, or no treatment. Graft loss was defined as a blood glucose >300 mg/100 ml.

RESULTS

Administration of DST + control IgG 4 weeks before transplantation resulted in accelerated rejection due to presensitization (median survival time of 8 days, compared with 14.5 days for the no-treatment group). Animals treated with CTLA4Ig in combination with DST had a median survival time of 12 days, compared with 8 days for DST + IgG.

CONCLUSIONS

CTLA4Ig attenuates the tempo of accelerated rejection in this islet allograft model of presensitization, but does not prolong allograft survival as compared with no treatment.

Importance of the tubulointerstitium in human glomerulonephritis. II. Distribution of integrin chains beta 1, alpha 1 to 6 and alpha V

Accumulation of extracellular matrix is important in the progression of glomerulonephritis. Since adherent cell types utilize integrins to bind and organize extracellular matrix proteins, we have assessed expression of the beta 1 integrins in sequential sections from 85 human renal biopsies and 4 normal kidneys by immunohistochemical staining. Our results demonstrate strong correlations between expression of the alpha 5 chain within the interstitium, the alpha V chain on proximal and distal tubular epithelium and the presence of chronic histological damage. Moreover, staining for interstitial alpha 5 and proximal and distal tubular alpha V were also strongly associated with expression of certain adhesion molecules (ICAM-1, VCAM-1, E-selectin and L-selectin) and the presence of macrophages within the interstitium, which have been linked, in an earlier study, with the degree of chronic histological damage and disease progression. However, in contrast to our earlier study of adhesion molecules, there were also associations between expression of integrin chains within the glomerulus and tubulointerstitium. For example, there were strong positive associations between staining for alpha 5 on glomerular endothelium and its expression on extraglomerular vascular endothelium and between both mesangial alpha 1 and podocyte alpha 3 and tubular staining for the common beta 1 subunit. While the functional significance of these associations is obscure, they suggest some kind of communication between cells in different sites in the kidney. There were also positive associations between staining for different integrins within the glomerulus, notably mesangial cell staining for alpha 2, glomerular endothelial cells staining for alpha 5 and glomerular epithelial cell alpha 3. These results suggest that there is a coordinated upregulation of integrin expression both within the tubulointerstitium and the glomerulus and that at least some of these integrins (interstitial alpha 5 and distal tubular alpha V) are associated with the expression of other adhesion molecules, macrophage infiltration and the presence of markers of disease progression (interstitial fibrosis and tubular atrophy).

Combined gastric and ileocecal toxicity (serpiginous ulcers) after oral kayexalate in sorbital therapy

Kayexalate (Roxane Labs, Columbus, OH) in sorbitol is commonly administered by the oral and rectal route for the treatment of hyperkalemia in patients with renal failure. It is believed to have minimal toxicity because it functions as a cation exchanger and is not absorbed. We herein report on a patient who developed identical serpiginous ulcers in the stomach and the terminal ileum after the use of Kayexalate. We believe that this drug could have significant gastrointestinal toxicity in specific patient groups and suggest tentative guidelines, both for the identification of such patients and for the safer use of Kayexalate in these circumstances.

Expression of beta 1 integrins in IgA nephropathy

AIM

To compare the expression of beta 1 integrins in renal biopsies from patients with IgA nephropathy with that found in normal human kidney.

METHODS

Thirty renal biopsies from patients with IgA disease plus six control specimens were stained with monoclonal antibodies directed against the alpha 1, alpha 2, alpha 3, alpha 4, alpha 5, alpha 6, alpha v, and beta 1 integrin chains using the alkaline phosphatase anti-alkaline phosphatase (APAAP) technique. The intensity of integrin expression was graded semiquantitatively by a pathologist unaware of the antibody used.

RESULTS

Glomerular crescents stained strongly for alpha 3, alpha v, and beta 1, but integrin expression was greatly reduced or absent in fibrotic glomeruli. There were no alterations in the intensity of mesangial cell staining for any of the integrins tested. There was accentuated staining for the alpha 2, alpha 5, alpha v, and beta 1 chains in areas of interstitial scarring plus alpha 2, alpha 3, alpha v, and beta 1 on damaged tubules. Inflammatory cells expressed alpha 4, alpha 5, and beta 1.

CONCLUSIONS

In IgA nephropathy the interstitium is the main site of altered beta 1 integrin expression. Glomerular crescents also express several beta 1 integrins, but we found no differences in the intensity of integrin expression on mesangial cells. Altered beta 1 integrin expression may play a role in tubulointerstitial scarring in IgA disease. Thus modulation of integrin expression might attenuate this process.

A noncytolytic IL-10/Fc fusion protein prevents diabetes, blocks autoimmunity, and promotes suppressor phenomena in NOD mice

We have been successful in our efforts to develop a long lived noncytolytic murine IL-10/Fc fusion protein. In the nonobese diabetic mouse (NOD) model, administration of IL-10/Fc from 5 to 25 wk of age completely prevented the occurrence of diabetes. Moreover, these mice remained disease-free long after cessation of IL-10/Fc therapy. Immunohistochemistry studies show that IL-10/Fc treatment inhibits expression of TNF-alpha, proinflammatory cytokine, as well as Th1-type cytokines, IL-2 and IFN-gamma, but promotes expression of IL-4 and IL-10, Th2-type cytokines, by islet-infiltrating leukocytes. In an adoptive transfer model of diabetes in NOD mice, we found that: 1) IL-10/Fc treated hosts bear leukocytes that block expression of diabetes and 2) these leukocytes persisted even 8 wk after cessation of IL-10/Fc treatment. The potent antidiabetogenic effects provided by IL-10/Fc in the NOD model, together with its apparent lack of systemic toxicity, are notable.

A noncytolytic IL-10/Fc fusion protein prevents diabetes, blocks autoimmunity, and promotes suppressor phenomena in NOD mice

We have been successful in our efforts to develop a long lived noncytolytic murine IL-10/Fc fusion protein. In the nonobese diabetic mouse (NOD) model, administration of IL-10/Fc from 5 to 25 wk of age completely prevented the occurrence of diabetes. Moreover, these mice remained disease-free long after cessation of IL-10/Fc therapy. Immunohistochemistry studies show that IL-10/Fc treatment inhibits expression of TNF-alpha, proinflammatory cytokine, as well as Th1-type cytokines, IL-2 and IFN-gamma, but promotes expression of IL-4 and IL-10, Th2-type cytokines, by islet-infiltrating leukocytes. In an adoptive transfer model of diabetes in NOD mice, we found that: 1) IL-10/Fc treated hosts bear leukocytes that block expression of diabetes and 2) these leukocytes persisted even 8 wk after cessation of IL-10/Fc treatment. The potent antidiabetogenic effects provided by IL-10/Fc in the NOD model, together with its apparent lack of systemic toxicity, are notable.

Endoglin, a transforming growth factor-beta-binding protein, is upregulated in chronic progressive renal disease

Endoglin is a non-signalling receptor for TGF-beta. In view of the importance of transforming growth factor-beta (TGF-beta) in the pathogenesis of renal disease, we have determined the distribution of TGF-beta in human glomerulonephritis. Endoglin was present within the glomerular mesangium and interstitium in normal kidneys. In diseased biopsies, there was a weak but significant correlation between staining for endoglin in the interstitium and the extent of chronic histological damage (r = 0.3343, p = 0.003). This was supported by division of biopsies into those showing mild damage and those with moderate to severe damage, where the latter group had significantly increased interstitial staining for endoglin (p = 0.0035). However, there was no correlation between mesangial staining for endoglin and specific types of glomerular pathology, such as IgA nephropathy, suggesting that the interstitial expression of endoglin is associated with increased renal damage independent of the specific type of glomerular lesion which initiates the process. There was also a positive correlation between mesangial cell staining for endoglin and interstitial endoglin expression (r = 0.3104, p = 0.003), although the former was not independently associated with chronic histological damage. These data suggest that the response of interstitial fibroblasts and mesangial cells may be linked in glomerulonephritis. Both could contribute to renal scarring by increased binding of TGF-beta which would be independent of the type of initial glomerular damage.

The Th1/Th2 paradigm and the allograft response

Although Th1- and Th2-type cytokine profiles have been associated with rejection and tolerance respectively, this paradigm may not be completely accurate. Instead, recent studies suggest that there could be a hierarchy of T-cell growth factors with regard to their ability to block tolerance and induce rejection (rather than a polarized Th1/Th2 demarcation).

CD44 in glomerulonephritis: expression in human renal biopsies, the Thy 1.1 model, and by cultured mesangial cells

CD44 is a transmembrane proteoglycan that serves as a cell adhesion receptor and is involved in cell-cell and cell-matrix interactions, both key events in the pathogenesis of clinical and experimental glomerulonephritis. In addition, recent evidence suggests that the binding of cytokines to proteoglycans could regulate cytokine function. We have, therefore, studied the expression of CD44 by mesangial cells in culture and in experimental (Thy 1.1 model) and human glomerulonephritis. Mesangial expression of CD44 detected by immunohistochemistry was markedly increased four days after induction of the Thy 1.1 model, coinciding with the peak of mesangial cell proliferation and macrophage infiltration. Analysis of 92 human renal biopsies by immunohistochemistry showed that CD44 expression by infiltrating cells within the glomerulus, in focal interstitial infiltrates and within the interstitium (interstitial fibroblasts, and extracellular matrix), was significantly increased in biopsies with a greater degree of histological damage. There was, however, no increase in mesangial staining in diseased kidneys as compared with control sections. In contrast, cultured human mesangial cells expressed CD44 strongly when assayed by immunohistochemistry, immunoprecipitation and Northern blotting. CD44, therefore, is an example of a protein strongly expressed by mesangial cells in vitro and weakly or not at all in vivo, but which is up-regulated in a disease model. In human disease, however, little expression was detected within the glomerular mesangium, which may be related to the greater proliferation and more profound disruption of mesangial architecture seen in the Thy 1.1 model. CD44 expression by infiltrating cells and by components of the interstitium could, however, play an important role in the pathogenesis of chronic progressive renal disease in humans.

Prolonged islet allograft acceptance in the absence of interleukin 4 expression

Murine CTLA4/Fc therapy leads to permanent engraftment of islet allografts in interleukin 4 (IL-4) knockout (IL-4-/- mice. Interestingly, IL-4+/- hosts were more resistant to tolerance induction than IL-4-/- mice. An IL-2/Fc fusion protein abrogates the effect of CTLA4/Fc therapy while an IL-4/Fc fusion protein tends to inhibit rather than enhance the effect of CTLA/Fc treatment in IL-4-/- recipients. We conclude that allograft acceptance requires principally a blockade of T cell activation rather than 'immune deviation' of the T cell activation program to Th2 cytokines (i.e. IL-4).

Adhesion molecule interactions in human glomerulonephritis: importance of the tubulointerstitium

Infiltration of leukocytes into glomerular and interstitial regions of the kidney is a key event in the pathogenesis of human glomerulonephritis. This process is mediated by specific adhesion molecules, some of which are expressed in a coordinated fashion following endothelial cell activation. We have assessed the pattern of expression of the selectins (E, P and L), and the counter-receptors (LFA-1 and ICAM-1, and VLA-4 and VCAM-1 in 119 renal biopsies using sequential sections, and have correlated this with the degree of histological damage (tubular atrophy and interstitial fibrosis) and the intensity of the macrophage infiltrate. Sections were stained with the monoclonal antibodies using a standard alkaline phosphatase anti-alkaline phosphatase (APAAP) technique. There were strong correlations between the following: (1) expression of LFA-1, VLA-4, and L-selectin in the periglomerular region, interstitium and in focal interstitial infiltrates and the presence of macrophages in these regions; (2) de novo tubular expression of ICAM-1 and VCAM-1; (3) staining for ICAM-1 and VCAM-1 on focal cellular infiltrates within the interstitium; and (4) staining for E- and P-selectin on extraglomerular endothelium. These are also strongly correlated with the degree of chronic histological damage. There was, however, no correlation between glomerular expression of adhesion molecules or glomerular macrophage infiltration and chronic histological damage. Although expression of VCAM-1 by the glomerular mesangium was strongly correlated with the presence of cells staining for VLA-4 within the glomerulus, glomerular expression of adhesion molecules correlated poorly with their expression in other sites. These results show that coordinated up-regulation of adhesion molecule expression in the tubulointerstitium is associated with interstitial fibrosis and tubular atrophy and may contribute, therefore, to the progression of renal disease.