Arthur H. Cohen

Pathologic Classification of Diabetic Nephropathy

Although pathologic classifications exist for several renal diseases, including IgA nephropathy, focal segmental glomerulosclerosis, and lupus nephritis, a uniform classification for diabetic nephropathy is lacking. Our aim, commissioned by the Research Committee of the Renal Pathology Society, was to develop a consensus classification combining type1 and type 2 diabetic nephropathies. Such a classification should discriminate lesions by various degrees of severity that would be easy to use internationally in clinical practice. We divide diabetic nephropathy into four hierarchical glomerular lesions with a separate evaluation for degrees of interstitial and vascular involvement. Biopsies diagnosed as diabetic nephropathy are classified as follows: Class I, glomerular basement membrane thickening: isolated glomerular basement membrane thickening and only mild, nonspecific changes by light microscopy that do not meet the criteria of classes II through IV. Class II, mesangial expansion, mild (IIa) or severe (IIb): glomeruli classified as mild or severe mesangial expansion but without nodular sclerosis (Kimmelstiel-Wilson lesions) or global glomerulosclerosis in more than 50% of glomeruli. Class III, nodular sclerosis (Kimmelstiel-Wilson lesions): at least one glomerulus with nodular increase in mesangial matrix (Kimmelstiel-Wilson) without changes described in class IV. Class IV, advanced diabetic glomerulosclerosis: more than 50% global glomerulosclerosis with other clinical or pathologic evidence that sclerosis is attributable to diabetic nephropathy. A good interobserver reproducibility for the four classes of DN was shown (intraclass correlation coefficient = 0.84) in a test of this classification.

The effect of pravastatin on acute rejection after kidney transplantation--a pilot study.

Hyperlipidemia is an important complication of kidney transplantation affecting up to 74% of recipients. HMG-CoA reductase inhibitors are reported to provide safe and effective treatment for this problem. A recent study suggests that pravastatin, an HMG-CoA reductase inhibitor, also decreases the incidence of both clinically severe acute rejection episodes and natural killer cell cytotoxicity after orthotopic heart transplantation. We have performed a prospective randomized pilot study of the effect of pravastatin on these same parameters after cadaveric kidney transplantation. Graft recipients were randomized to receive pravastatin after transplantation or no pravastatin (24 patients in each group) in addition to routine cyclosporine and prednisone immunosuppression. Lipid levels, acute rejection episodes and serial natural killer cell cytotoxicities were followed for 4 months after the transplant. At the end of the study period, pravastatin had successfully controlled mean total cholesterol levels (202.6 +/- 9.3 vs. 236.5 +/- 11.9 mg/dl, P < 0.02), LDL levels (107.9 +/- 6.6 vs.149.6 +/- 10.7 mg/dl, P < 0.002), and triglyceride levels (118.8 +/- 14.2 vs. 157.2 +/- 13.8 mg/dl, P < 0.05). In addition, the pravastatin-treated group experienced a reduction in the incidence of biopsy-proven acute rejection episodes (25% vs. 58%, P = 0.01), the incidence of multiple rejections episodes (P < 0.05), and the use of both pulse methylprednisolone (P = 0.01) and OKT3 (P = 0.02). Mean natural killer cell cytotoxicity was similarly reduced (11.3 +/- 1.6 vs. 20.0 +/- 2.0% lysis of K562 target cells, P < 0.002). These data suggest that pravastatin exerts an additional immunosuppressive effect in kidney transplant recipients treated with cyclosporine-based immunosuppression.

Induction of Membranous Nephropathy in Rabbits by Administration of an Exogenous Cationic Antigen: DEMONSTRATION OF A PATHOGENIC ROLE FOR ELECTRICAL CHARGE

We examined the role of antigenic electrical charge as a determinant of glomerular immune complex localization in the rabbit. Serum sickness nephritis was induced in groups of New Zealand white rabbits by daily 25-mg intravenous injections of bovine serum albumin (BSA) chemically modified to be cationic (pI > 9.5) or more anionic (pI, 3.5-4.6); an additional group received unmodified native BSA (pI, 4.5-5.1). Factors known to influence immune complex localization, e.g., molecular size of the administered antigen and resulting circulating immune complexes, immunogenicity, and disappearance time from the circulation were examined and found to be similar for both anionic and cationic BSA. Charge modification did increase the nonimmune clearance of cationic and anionic BSA compared with native BSA. Injected cationic BSA was shown in paired label experiments to bind directly to glomeruli compared with native BSA. The renal lesion produced by cationic BSA was markedly different from that found in rabbits given anionic or native BSA. Animals receiving cationic BSA uniformly developed generalized diffuse granular capillary wall deposits of IgG, C3, and BSA detected after 2 wk of injections and increasing until death at 6 wk. Qualitatively similar deposits were produced by the administration of low doses of cationic BSA of only 1 or 10 mg/d. In contrast, the injection of both anionic and native BSA resulted in mesangial deposits at 2 and 4 wk with capillary wall deposits appearing by 6 wk. Ultrastructural examination of animals receiving cationic BSA revealed pure, extensive formation of dense deposits along the lamina rara externa of the glomerular basement membrane whereas such deposits were absent or rare in animals injected with the anionic or native BSA. Albuminuria was significantly greater at 6 wk in the groups receiving cationic BSA with a mean of 280 mg/24 h compared with 53 mg/24 h in the combined groups injected with anionic or native BSA. Blood urea nitrogen values were similar in all groups at 2 and 4 wk but higher in the animals receiving cationic BSA at 6 wk. These experiments describe the reproducible induction of epimembranous immune deposits by administration of an exogenous cationic antigen. They suggest that antigenic charge can play an important role in the pathogenesis of membranous nephropathy by permitting direct glomerular binding of an antigen and predisposing to in situ immune complex formation.

Human Immunodeficiency Virus (HIV) Infection and the Kidney

Since the first report on the acquired immunodeficiency syndrome (AIDS) in 1981, organ involvement of AIDS has increased. We discuss the effect of human immunodeficiency virus (HIV) infection, the causative agent of AIDS, on the field of nephrology. Hyponatremia, the commonest fluid and electrolyte abnormality, is caused by various pathophysiologic mechanisms, including adrenal insufficiency. The renal parenchymal complications are diverse, but a new entity, HIV-associated nephropathy, is becoming recognized because of its characteristic clinical and pathologic features, including the fact that it causes irreversible renal failure. HIV infection in patients with end-stage renal failure, both before and after initiation of maintenance dialysis, is a significant problem. The present methods of preventing spread of virus in dialysis units seem successful. Few patients who are infected with HIV or who have AIDS have had renal transplantation, although unsuspected viral infection of cadaveric organs remains a concern.

Early hepatic nodular hyperplasia and submicroscopic fibrosis associated with 6-thioguanine therapy in inflammatory bowel disease

Background6-Thioguanine (6-TG) has been used as an alternative thiopurine for inflammatory bowel disease (IBD) patients not responsive to or intolerant of azathioprine (AZA) and 6-mercaptopurine (6-MP). 6-TG-related hepatotoxicity, including liver biochemistry value elevations, sinusoidal collagen deposition on electron microscopy, and veno-occlusive disease, have been described related to its use as therapy for neoplastic disease. MethodsWe studied 38 liver biopsies from patients treated with 6-TG, almost all of whom (n = 125) received 6-TG for 1 to 3 years at the Inflammatory Bowel Disease Center at Cedars-Sinai Medical Center. All biopsies were fixed in 4% buffered formalin and prepared in the usual manner. Hematoxylin and eosin, Masson’s trichrome (trichrome), and reticulin silver impregnation (reticulin) stained slides were studied. In 23 cases, tissue was also prospectively fixed in glutaraldehyde and processed for electron microscopy. ResultsIn 20 of the 37 patients studied (53%), nodular regeneration of varying degree was seen with reticulin. In only 4 of these 20 instances (11% of the total) were the changes seen with hematoxylin and eosin and in 3 of the 4, only in retrospect after studying the reticulin preparation. Minimal fibrosis was seen with trichrome in only 13 biopsies (34%), but sinusoidal collagen deposition was observed in 14 of the 23 cases studied with electron microscopy (60%). The biopsy from the 1 patient with nodular hyperplasia obvious with hematoxylin and eosin also demonstrated changes of venous outflow obstruction. Conclusions6-TG-treated IBD patients are at significant risk for nodular hyperplasia, early fibrosis and, less often, venous outflow disease (Budd-Chiari). The natural history of these changes is unknown and follow-up biopsies are needed to determine histologic and clinical sequela. Patients not demonstrating nodular hyperplasia or fibrosis who continue with 6-TG because there are no better therapeutic choices should be periodically rebiopsied.

Evaluation of Renal Transplant Dysfunction by Duplex Doppler Sonography: A Prospective Study and Review of the Literature

A disconcertingly wide variation exists in the literature as to the accuracy of duplex Doppler sonography in the detection of acute renal transplant rejection. Sensitivities range from 9% to 76%. In an attempt to explain the disparity of results, we undertook a double-blind prospective study of the accuracy of duplex Doppler ultrasound in the detection of acute rejection in renal transplants. We scanned 49 consecutive patients with a total of 65 biopsies; 46 biopsies in 33 consecutive patients were included in our study. In our population, the prevalence of acute rejection was 61% (28/46). Using a resistive index (RI) cutoff of greater than 0.90 based on the main renal artery flow pattern, the sensitivity of our test was 43%, with a 67% specificity. The positive predictive value was 67%. Our results are contrasted and compared with the published data from other groups in a critical survey of the literature. We conclude that duplex Doppler sonography alone is inadequate to evaluate acute rejection in renal transplants.

Plasma exchange for recurrent nephrotic syndrome following renal transplantation.

Patients with steroid-resistant nephrotic syndrome and focal segmental glomerulosclerosis (FGS) who develop end-stage renal disease are at risk for recurrence of the disease following renal transplantation. Recurrence of the nephrotic syndrome in renal allografts of two children with primary FGS was successfully controlled by plasma exchange. This report suggests that plasma exchange instituted early in the course of recurrent nephrotic syndrome may be beneficial in some patients with steroid-resistant nephrotic syndrome and FGS.

Electrical Charge. ITS ROLE IN THE PATHOGENESIS AND PREVENTION OF EXPERIMENTAL MEMBRANOUS NEPHROPATHY IN THE RABBIT

Intravenous cationic bovine serum albumin (BSA, pI > 9.5) induces membranous nephropathy in immunized rabbits. In this study, unimmunized rabbits received intravenous injections of cationic (n = 3) or native (n = 3) or native (n = 3) BSA, followed by ex vivo isolated left renal perfusions with sheep anti-BSA antibody. Capillary wall deposits of IgG and C3 were seen exclusively in the group receiving cationic BSA, confirming an in situ pathogenesis for cationic, BSA-induced membranous nephropathy, and demonstrating the importance of a cationic antigen for its production. We then explored whether membranous nephropathy in this model is prevented by the concomitant injection of protamine sulfate, a filterable, relatively non-immunogenic polycation. An in vitro study demonstrated that protamine sulfate incubated with glomerular basement membrane (GBM) decreased the subsequent binding of radiolabeled cationic BSA (P < 0.05). In vivo, protamine sulfate was shown to bind to anionic sites in the glomerular capillary wall after intravenous injection.Groups of rabbits received 3 wk of daily intravenous injections of cationic BSA alone (n = 15) or cationic BSA and protamine (n = 18). After 2 wk of injection of cationic BSA alone, typical membranous nephropathy developed. Granular deposits of IgG and C3 were present along the GBM associated with subepithelial dense deposits, foot process effacement, and marked albuminuria. Protamine significantly reduced or prevented the formation of deposits (P < 0.001) and in6 of 18 protamine-treated animals, existing deposits decreased or disappeared between 2 and 3 wk of injection. Albuminuria was significantly reduced in protamine-treated animals with a mean of 124+/-55 mg/24 h compared to 632+/-150 mg/24 h in the control group receiving cationic BSA alone. No significant differences between the groups were noted in serum lev9lsof IgG, C3, anti-BSA antibody, or circulating immune complex size. Studies in additional animals (n = 5) given radiolabeled cationic BSA showed that protamine did not alter the clearance of cationic BSA from serum. Control experiments showed that protamines beneficial effects were not related to its weak anticoagulant property or toits theoretical ability to deplete tissue histamine. The administration of heparin (n = 6) or diphenhydramine (n = 6) had no effect on the development of the epimembranous lesion compared to the group receiving cationic BSA alone. In addition, homogenized whole kidney histamine content was not significantly different in the group receiving cationic BSA alone compared to the group receiving cationic BSA and protamine. This work shows that a cationic BSA-induced glomerular lesion can be produced by a renal perfusion technique involving in situ complex formation and that this process requires a cationic antigen for its development. We believe that the demonstrated beneficial effects of protamine are due to its ability to bind to glomerular anionic sites, and that this electrostatic interaction results in inhibition for the further binding of the cationic antigen, thereby limiting the severity of glomerulonephritis in this model.

Surrogate markers for long-term renal allograft survival.

Progressive improvement in kidney transplant survival rates and reduction in acute rejection rates have ironically restricted our ability to evaluate newer therapy. Current short‐term endpoints such as acute rejection rates have reduced utility in predicting long‐term survival. Long‐term graft survival is an ideal endpoint, but is limited by longer follow‐up requirements and the large cohort of patients required for such studies. Newer short‐term surrogate markers should be identified and these markers should correlate with long‐term graft failure. Hence, identification of short‐term surrogate markers is critical to test newer immunosuppressive strategies over current therapies, and should also predict long‐term transplant outcome. Potential surrogate markers are clinical parameters such as renal function, renal histological findings of fibrosis and immunological markers. Post‐transplant renal function estimated by serum creatinine within 1 year has been shown to correlate with long‐term survival. Alternative evaluation of renal function such as clearance studies and cystatin C, which are more accurate, could potentially be useful in clinical trials. Renal histological indices such as fibrosis measured as Chronic Allograft Disease Index score or Banff score correlate with long‐term graft survival. Immunological markers such as antidonor antibodies, levels of blood and urine cytokines, real time PCR, ELISPOT and microarrays are attractive surrogates to consider. Measurement of morbidity and mortality after transplantation is critical to further enhance long‐term survival. Thus, there are many potential surrogate markers and these individually or in combination with conventional endpoints should be implemented in clinical trials and validated in long‐term studies.

Sjögren's syndrome with immune-complex tubulointerstitial renal disease.

Abstract Renal functional abnormalities and evidence of interstitial nephritis are common in Sjogrens syndrome, and it has been suggested that the interstitial changes may be on an immunologic basis. We report a patient with the sicca complex variety of Sjogrens syndrome who presented with renal functional insufficiency and intense interstitial nephritis. Focal tubular basement membrane (TBM) deposits were observed, and immunofluorescence showed focal TBM deposits of IgG and C3. Glomeruli contained no deposits. Therapy with prednisone and cyclophosphamide was associated with marked clinical improvement and regression of tissue leukocyte infiltration. We propose local or in situ formation of immune complexes, as in the rabbit model of autologous immune-complex interstitial nephritis, and suggest that this mechanism may be operative in some patients with Sjogrens syndrome and tubulointerstitial renal disease. Immunosuppressive therapy may have helped to preserve renal function.