Diagnostic yield of renal biopsies: a retrospective single center review.

BACKGROUND: Previous studies have examined the spectrum of diseases identified with a kidney biopsy and the complications of the procedure. However, few studies have examined the utility of the test to clarify the diagnosis and guide treatment of pediatric patients. This retrospective, single-center chart review was performed to test the hypothesis that at least 80% of native kidney biopsies provide clinically valuable information that rationally guides diagnosis and patient management. METHODS: 200 biopsies performed between January 1, 2000 and June 30, 2008 were reviewed. A scheme composed of six categories was devised to classify the utility of each kidney biopsy. RESULTS: 196 complete case files were available for review. Twenty-four (12.2%) biopsies did not shed light on the diagnosis and were unhelpful in patient management - 21 biopsies (10.7%) were non-diagnostic and 3 (1.5%) failed to yield enough tissue for examination. The number of unhelpful biopsies did not cluster in any specific disease entity. CONCLUSION: Our findings provide guidance to nephrologists about the total risk of a kidney biopsy, including uninformative results, when seeking informed consent for the procedure. The results suggest an appropriate balance has been reached which maximizes the use of kidney biopsies while minimizing the risk of this invasive procedure (word count: 202).

Vancomycin-induced acute granulomatous interstitial nephritis: therapeutic options.

Drug-induced acute renal failure is a commonly encountered mode of renal injury in the hospitalized patient. Vancomycin is a frequently used antibiotic in patients with Gram-positive bacterial infections. In the present study, we evaluated an index case of a patient who developed severe acute granulomatous interstitial nephritis and provided a review of the reported cases of vancomycin-induced acute renal failure in the literature. A Medline search revealed a total of 11 cases of vancomycin-induced interstitial nephritis. In 2 reported cases, interstitial nephritis has been reported with associated granuloma formation. However, the role of T cells in the formation of interstitial nephritis and in the choice of therapeutic modalities in this scenario has not been evaluated in the past. In the index case, we have evaluated the effect of treatment on the basis of the type of cellular infiltrates and provided a follow-up by carrying out the repeat biopsy.

Idiopathic membranous nephropathy in pediatric patients: presentation, response to therapy, and long-term outcome.

BACKGROUND: Idiopathic membranous nephropathy (IMN) is one of the most common causes of primary nephrotic syndrome in adults. However, it is a relatively rare entity in the pediatric population and there is a paucity of data about the incidence, prognosis, and optimal treatment of IMN in children and adolescents. We conducted this study to evaluate pediatric patients with IMN in order to clarify the presentation, response to therapy, and clinical outcome. METHODS: A retrospective chart review was performed on patients identified with biopsy-proven IMN between 1988-2005. Patients with systemic lupus erythematosus or hepatitis-related lesions were excluded. The following data were tabulated: age, gender, ethnicity, presenting clinical and laboratory findings, proteinuria in a first morning urine specimen, estimated glomerular filtration rate (GFRe), histopathology, type and duration of treatment, and clinical status at final evaluation. RESULTS: 13 cases of IMN were identified out of 460 renal biopsies performed for evaluation of primary kidney disease during the study interval. Mean age was 9.6 +/- 4.6, gender 6 M:7 F, ethnicity 8 W:2 B:3 H. At the initial visit hematuria was present in 9 patients, edema in 5, nephrotic-range proteinuria in 5, and hypertension in 3. Mean urinary protein:creatinine ratio 3.3 +/- 2.5 and all patients had a normal GFRe. Classic glomerular findings of IMN were seen in all renal specimens, with concomitant interstitial changes in 2 cases. Treatment included an angiotensin converting enzyme inhibitor or angiotensin receptor blocker in 11 cases. Most patients were also given immunosuppressive medications - prednisone in 10, a calcineurin inhibitor in 5, and mycophenolate mofetil or azathioprine in 3 patients. At the last follow-up, 42 +/- 35 months after the diagnostic biopsy, 7 children were hypertensive and the urine protein:creatinine ratio was 2.3 +/- 3.1. The mean GFRe was 127 +/- 57 mL/min/m2. Three patients had Chronic Kidney Disease Stage 3, all of whom were also hypertensive. CONCLUSION: IMN is a rare but serious glomerulopathy in pediatrics. We estimate that it accounts for approximately 3% of renal biopsies. Long-term prognosis is guarded because approximately 50% of patients may have evidence of progressive kidney disease.

Monoclonal gammopathy presenting as recurrent nephrotic syndrome: therapeutic implications.

Most forms of renal disease associated with monoclonal gammopathy result from deposition of monoclonal immunoglobulins or their subunits in different compartments of the kidney. Renal monoclonal immunoglobulin deposition disease (MIDD) is defined by linear deposits of monoclonal light-chain components in renal basement membranes, often producing a nodular sclerosing glomerulopathy. Clinical features of renal MIDD include proteinuria, with or without renal failure, and an association with dysproteinemias. Three types of renal MIDD have been reported, namely, light-chain deposition disease (LCDD), light- and heavy-chain deposition disease (LHCDD), and heavy-chain deposition disease (HCDD). Reports on LHCDD are rare. At present, follow-up data are limited on the management of renal monoclonal protein deposition disease. We present a case of monoclonal protein deposition in the kidney containing both heavy and light chains with unique characteristics that did not conform to any of the above previous established classes. Its follow-up revealed an unusual relapsing and remitting course in response to treatment.

DEC-205-mediated internalization of HIV-1 results in the establishment of silent infection in renal tubular cells.

HIV-1 infection of renal cells has been proposed to play a role in HIV-1-associated nephropathy. Renal biopsy data further suggest that renal tubular cells may serve as reservoir for HIV-1. The mechanism by which HIV-1 enters these cells has not been identified. Renal tubular cells do not express any of the known HIV-1 receptors, and our results confirmed lack of the expression of CD4, CCR5, CXCR4, DC-SIGN, or mannose receptors in tubular cells. The aim of this study, therefore, was to determine the mechanism that enables viral entry into renal tubular cells. An in vitro model was used to study the HIV-1 infection of human kidney tubular (HK2) cells and to identify the receptor that enables the virus to enter these cells. Results of these studies demonstrate that the C-type lectin DEC-205 acts as an HIV-1 receptor in HK2 cells. Interaction of HIV-1 with DEC-205 results in the internalization of the virus and establishment of a nonproductive infection. HIV-1-specific strong-stop DNA is detected in the infected HK2 cells for at least 7 d, and the virus can be transmitted in trans to sensitive target cells. HIV-1 entry is blocked by pretreatment with specific anti-DEC-205 antibody. Moreover, expression of DEC-205 in cells that lack the DEC-205 receptors renders them susceptible to HIV-1 infection. These findings suggest that DEC-205 acts as an HIV-1 receptor that mediates internalization of the virus into renal tubular cells, from which the virus can be rescued and disseminated by encountering immune cells.

Meprin-alpha in chronic diabetic nephropathy: interaction with the renin-angiotensin axis.

Meprin (MEP) A is a metalloendopeptidase that is present in the renal proximal tubule brush-border membrane (BBM) and that colocalizes with angiotensin-converting enzyme (ACE). The MEP beta-chain gene locus on chromosome 18 has been linked to a heightened risk of diabetic nephropathy (DN) in patients with type 2 diabetes. This study evaluated 1) whether MEP-alpha and MEP-beta gene and protein expression are altered in db/db mice before the onset of DN and 2) the role of MEP-alpha in the pathogenesis of DN and the impact of the renin-angiotensin system on this interaction in two experimental models of diabetes. MEP-alpha and MEP-beta gene and protein expression were evaluated in db/db mice, 13-14 wk of age, compared with lean C57BLKS/J littermate animals. A treatment study was then performed in which db/db mice and controls were assigned to one of three groups: control (C) water, no therapy; ACE inhibitor therapy, enalapril (EN)-treated water, 50 mg/l; ANG II receptor type 1 blocker (ARB) therapy, losartan (LOS)-treated water, 500 mg/l. Treatment was started at 8 wk of age and continued for 52 wk. Male Sprague-Dawley rats with diabetes for 52 wk following a single dose of streptozocin (STZ; 60 mg/kg) were also studied. At 13.5 wk of age, MEP-alpha and MEP-beta kidney mRNA abundance and protein expression were significantly lower in db/db mice compared with lean controls, with greater changes in MEP-beta (P < 0.05). In the treatment study, EN ameliorated and LOS exacerbated DN in db/db mice. BBM MEP A enzymatic activity and MEP-alpha protein content were lower in db/db mice vs. control nonobese mice at 52 wk (P < 0.02). EN-treated db/db mice showed increased MEP A activity, MEP-alpha content in BBM, decreased urinary MEP-alpha excretion, and enhanced BBM staining for MEP-alpha protein vs. C and LOS-treated db/db mice. In nonobese mice, EN and LOS treatment had no effect on MEP-alpha expression. In rats with STZ-induced diabetes for 52 wk, urinary MEP-alpha excretion was increased and MEP A activity and MEP-alpha protein content per milligram of BBM protein were decreased compared with age-matched control animals (P < 0.05). These results indicate that db/db mice manifest decreased MEP-alpha and MEP-beta gene and protein expression, before the development of overt kidney disease. Moreover, in db/db mice with DN and rats with STZ-diabetes, there was an inverse relationship between renal MEP-alpha content and the severity of the renal injury. Treatment with an ACE inhibitor was more effective than ARB in ameliorating DN in db/db mice, a change that correlated with alterations in urinary excretion and BBM content of MEP-alpha. MEP-alpha may play a role in the pathogenesis of DN and the benefits of ACE inhibitor therapy on the progression of diabetic kidney disease may be related, in part, to its impact on renal MEP-alpha expression.

Prevention of renal fibrosis by spironolactone in mice with complete unilateral ureteral obstruction.

PURPOSE: Recent data suggest that aldosterone directly mediates cardiac fibrosis and hypertensive nephrosclerosis. We conducted experiments to determine whether administration of spironolactone, a mineralocorticoid receptor antagonist, reduced renal fibrosis in an experimental model of obstructive uropathy. MATERIALS AND METHODS: Complete unilateral ureteral obstruction (UUO) was created surgically in 8 to 10-week-old male C57BL/6 mice by placing sutures around the right ureter. Spironolactone (50 mg/kg/daily) or 1% dimethyl sulfoxide vehicle was administered by subcutaneous injection for 1 to 2 weeks, and renal fibrosis was assessed by measuring trichrome staining and type I collagen deposition in the kidney. RESULTS: UUO lasting 1 week was associated with minimal parenchymal damage and spironolactone had no demonstrable effect. In contrast, administration of the mineralocorticoid antagonist (8 mice) for a 2-week period significantly reduced renal fibrosis in the obstructed kidney, compared to mice given the dimethyl sulfoxide vehicle (9). The beneficial effect of spironolactone treatment was not associated with any changes in serum potassium or aldosterone concentration, or urinary concentrations of sodium or potassium. CONCLUSIONS: Administration of spironolactone reduced renal fibrosis in mice with UUO. These findings suggest that clinical trials are warranted to determine the efficacy of aldosterone antagonists in conjunction with angiotensin converting enzyme inhibitors and/or angiotensin receptor blockers as renoprotective agents in patients with obstructive uropathy.

Reliability of splenic index to assess splenic involvement in pediatric Hodgkin's disease.

The purpose of this study was to determine the reliability of the splenic index (SI) in children with Hodgkin's disease (HD). Seventeen patients who underwent staging laparotomy for HD were included in this study. Pretreatment computed tomography scans of these patients were reviewed retrospectively to determine the SI. The specificity, sensitivity, positive and negative predictive values, and accuracy of the SI were calculated. The sensitivity and specificity of the SI were 50% and 66%, respectively. The SI alone accurately identified or ruled out involvement with HD in 10 of 17 patients. Positive and negative predictive values of the SI were 57% and 60%, respectively. Even with the use of the SI, computed tomography alone remains unreliable to determine splenic involvement in children with HD. Additional imaging studies, especially fluorodeoxyglucose positron emission tomography, may improve the clinical staging of HD.

Proliferative glomerulonephritis with monoclonal IgG deposits: a distinct entity mimicking immune-complex glomerulonephritis.

BACKGROUND: Renal disease related to the deposition of monoclonal immunoglobulins containing both heavy and light chains can occur in type 1 cryoglobulinemia, Randall type light and heavy chain deposition disease (LHCDD), and immunotactoid glomerulonephritis. We report a novel phenotype of glomerular injury that does not conform to any of the previously described patterns of glomerular involvement by monoclonal gammopathy. METHODS: Ten cases of unclassifiable proliferative glomerulonephritis manifesting glomerular monoclonal immunoglobulin G (IgG) deposits were identified retrospectively from the archives of the Renal Pathology Laboratory of Columbia University over the past 3 years (biopsy incidence 0.21%). RESULTS: The monoclonal immunoglobulins formed granular electron dense deposits in mesangial, subendothelial, and subepithelial sites, mimicking ordinary immune complex-mediated glomerulonephritis and producing a diffuse endocapillary proliferative or membranoproliferative glomerulonephritis. However, by immunofluorescence, the deposits were monoclonal, staining for a single light chain isotype and a single gamma subclass (including two IgG1kappa, one IgG1lambda, one IgG2lambda, four IgG3kappa, and one IgG3lambda). All cases stained for the three constant domains of the gamma heavy chain (CH1, CH2, and CH3), suggesting deposition of a nondeleted immunoglobulin molecule. Tissue fixation of complement was observed in 90% of cases, and 40% of patients had hypocomplementemia. Clinical presentations included renal insufficiency in 80% (mean serum creatinine 2.8 mg/dL, range 0.9 to 8.0), proteinuria in 100% (mean urine protein 5.8 g/day; range 1.9 to 13.0), nephrotic syndrome in 44%, and microhematuria in 60%. A monoclonal serum protein with the same heavy and light chain isotype as that of the glomerular deposits was identified in 50% of cases (including three IgGkappa and two IgGlambda); however, no patient had clinical or laboratory features of type 1 cryoglobulinemia. No patient had overt myeloma or lymphoma at presentation or over the course of follow-up (mean 12 months). CONCLUSION: Glomerular deposition of monoclonal IgG can produce a proliferative glomerulonephritis that mimics immune-complex glomerulonephritis by light and electron microscopy. Proper recognition of this entity requires confirmation of monoclonality by staining for the gamma heavy chain subclasses.

Retroperitoneal neurofibrosarcoma in a patient with neurofibromatosis. 2: A case report and review of the literature.

Neurofibromatosis (NF) type I (NF1) is the most common familial cancer-predisposing syndrome in humans, while type 2 (NF2) accounts for an extremely small percentage of the total cases of NF. Tumors occurring in patients with NF1 are primarily peripheral neurofibromas, while NF2 patients present with central schwannomas. Malignant transformation has been described in NF1 patients; however, in NF2 the risk of malignant transformation is extremely rare. In this case report, the authors document a retroperitoneal neurogenic sarcoma occurring in a 20-year-old woman with NF2 (bilateral acoustic schwannomas, meningioma, and multiple intraspinal tumors).

An adolescent with ovarian osteosarcoma arising in a cystic teratoma.

A 14-year-old girl had an abdominal mass with the characteristics of an ovarian germ cell tumor on computed tomography scan. The mass, arising from the left ovary, was completely resected and found to be osteosarcoma arising from a mature cystic teratoma. A metastatic lesion in the abdomen did not respond to 2 courses of cisplatin, doxorubicin, ifosfamide, and high-dose methotrexate, and was resected. Seven months after completion of chemotherapy, there were simultaneous local recurrence and lung metastases. Previously, 10 cases of ovarian osteosarcoma have been reported in the literature: 5 were primary osteosarcoma of the ovary, 4 were associated with teratomas, and 1 was part of a malignant mixed mesodermal tumor of the ovary. Of the 10, there are only 2 long-term survivors, both of whom were treated with adjuvant chemotherapy following complete resection.

Pulmonary crystal-storing histiocytosis and extranodal marginal zone B-cell lymphoma associated with a fibroleiomyomatous hamartoma.

Crystal-storing histiocytosis (CSH) is a rare disorder occurring in patients with lymphoproliferative diseases, predominantly in cases of multiple myeloma and low-grade B-cell lymphoma. To the best of our knowledge, only three cases of pulmonary CSH have been reported in the English literature and one of them was associated with a low-grade B-cell lymphoma (immunocytoma). We document a case of a 59-year-old man with bilateral lung masses in which a right middle lobe pulmonary lobectomy specimen showed CSH associated with an extranodal marginal-zone B-cell lymphoma. A single nodule showing features of fibroleiomyomatous hamartoma was present in a wedge biopsy specimen from the left lung. Two nodules within the right middle lobe were composed of sheets of histiocytic cells with abundant eosinophilic cytoplasm resembling striated muscle cells. In addition, there were nodular aggregates and a more diffuse infiltrate of small slightly atypical centrocyte-like lymphocytes, as well as bronchial lymphoepithelial lesions. Immunohistochemistry performed on paraffin-embedded sections demonstrated that the histiocytic cells were immunoreactive with the KP-1 (CD68) antibody while the lymphocytic infiltrate was CD20 positive, co-expressed for CD43, and was negative for CD3, CD5, and CD10. Genotypic analysis demonstrated the presence of an immunoglobulin heavy-chain gene rearrangement, indicating the presence of a monoclonal B-cell population. These features were consistent with pulmonary CSH associated with extranodal marginal-zone lymphoma of baltoma type.

Meningioangiomatosis: report of three cases and review of the literature.

Meningioangiomatosis is a rare condition, probably hamartomatous, characterized by proliferation of capillary-sized vessels, meningothelial cells, and fibroblasts within the cortex of the brain. Lesions may be single or diffuse and may be associated with neurofibromatosis type II. Clinically it presents with seizures but may be asymptomatic throughout life. We report 3 cases of meningioangiomatosis, 2 localized and 1 diffuse, all with different clinical manifestations. Differential diagnoses are discussed with a review of the literature. Since this condition is rare, close clinico-pathological correlation is essential. A correct diagnosis avoids further aggressive treatment.

Possible role of high density lipoprotein in the progression of glomerulosclerosis.

The collapsing variant of focal segmental glomerulosclerosis is a fulminant lesion characterized by rapid progression to end-stage renal disease. Substantial in vivo and in vitro evidence suggests that lipids, particularly low density lipoprotein (LDL), can contribute to the progression of glomerulosclerosis as they do in atherosclerosis. The nephrotic syndrome is typically associated with marked elevation of LDL and suppression of high density lipoprotein (HDL), abnormalities which may, accelerate both of these lesions. We report the case of a patient who presented with heavy proteinuria and hypertension and was found to have collapsing focal segmental glomerulosclerosis as well as, surprisingly, a markedly elevated HDL level. Despite the poor prognosis of this lesion, over a 3-year period the patient maintained normal renal function and has experienced a decline in her proteinuria to below-nephrotic levels while maintaining an elevated HDL level. Though this is only a single report, it may nevertheless be worthwhile to consider the possibility that HDL levels could potentially modulate the course of glomerular disease.

Dermoid cysts of the tongue: report of five cases and review of the literature.

Dermoid cysts of the tongue are uncommon. To date, there have been nine reported cases in the English language literature. In this article, we describe five cases accessioned at our institution over a 12-year period, two of which have previously been reported. The prevalence of dermoid cysts at our institution over this period was quite low. Of 324,042 surgical cases, 0.24% (765 cases) were dermoid cysts. Of these, five were from the tongue, representing only 0.7% of the dermoid cysts accessioned and 0.0015% of the total surgical specimens. The literature is reviewed and the possible origin of these lesions is discussed.

Obstructive congenital epulis: prenatal diagnosis and perinatal management.

OBJECTIVE: To describe a multidisciplinary approach for delivery room management of congenital epulis. STUDY DESIGN: Case reports. METHODS: Reporting of two cases of congenital epulis and review of the literature. RESULTS: Antepartum ultrasonography demonstrated massive intraoral masses in two fetuses whereby concerns regarding the patency of the airway at birth necessitated development of a multidisciplinary team of maternal-fetal medicine, neonatal-perinatal medicine, anesthesiology, and otolaryngology. Surgical excision was performed before delivery in one infant and after complete delivery in the other without a need for endotracheal intubation and general anesthesia. Feeding was started early, and both infants were discharged after brief hospital stays. Pathological findings were consistent with congenital epulis. Differential diagnosis and options for surgical intervention are discussed, including ex utero intrapartum treatment. CONCLUSIONS: A multidisciplinary approach to antenatally identified congenital intraoral masses facilitates care at birth. Surgical treatment in this milieu may be simple and complete at the time of delivery.

Nitric oxide in obstructive uropathy: role of endothelial nitric oxide synthase.

PURPOSE: Nitric oxide (NO) ameliorates fibrosis in experimental obstructive uropathy. Previously, we demonstrated that renal fibrosis was decreased after 2 weeks of unilateral ureteral obstruction in inducible nitric oxide synthase (iNOS) knock-out mice given L-arginine supplemented drinking water. We proposed that the 2 constitutive isoforms of nitric oxide synthase (NOS) mediated down-regulation of renal fibrosis in response to prolonged ureteral obstruction. To determine the specific role of endothelial NOS (eNOS) versus neuronal NOS in modulating renal fibrosis due to obstructive uropathy, we evaluated renal injury following unilateral ureteral obstruction in C57BL/6J mice subjected to biochemical inhibition of the constitutive isoforms of NOS and in eNOS knockout mice. MATERIALS AND METHODS: Four groups of C57BL/6J mice were studied. Complete unilateral ureteral obstruction was created by ligating the right ureter at age 8 weeks. A single daily intraperitoneal injection of 30 mg./kg. S-methyl-L-thiocitrulline (SMLT), a selective neuronal and endothelial NOS inhibitor was started 24 hours before ureteral obstruction and administered to half of the study animals. SMLT treated mice and control animals were further subdivided to receive either regular tap water or 1% L-arginine (weight/volume) supplemented water after unilateral ureteral obstruction. Animals were sacrificed on postoperative day 3, 7 or 14. In addition, eNOS knockout mice with unilateral ureteral obstruction were given tap water or L-arginine supplemented water to drink and sacrificed after 14 days. Urine specimens from the bladder and the obstructed renal pelvis along with serum were collected. Nitrite level in each fluid was determined. Renal morphology and cortical thickness were assessed in the normal and obstructed kidneys. Interstitial fibrosis was evaluated using trichrome stain. RESULTS: SMLT was well tolerated by C57BL/6J mice. Serum nitrite levels and nitrite excretion in bladder urine were similar in all SMLT treated groups throughout the duration of unilateral ureteral obstruction. A reduction of pelvic urine nitrite levels by 89%, 68% and 48% versus bladder urine nitrite levels was observed after 3, 7 and 14 days of unilateral ureteral obstruction (p <0.05). Administration of SMLT resulted in a significant increase in bladder urine nitrite level at 7 days and in pelvic urine nitrite levels at 14 days. No significant histological differences in the obstructed kidney were seen after 3, 7 or 14 days of unilateral ureteral obstruction in SMLT treated versus control mice regardless of whether they received tap water or L-arginine supplemented drinking water. In eNOS knockout mice with unilateral ureteral obstruction for 14 days L-arginine supplementation had no effect on pelvic urine nitrite levels and did not alter renal histopathology or cortical thickness. CONCLUSIONS: NO production is decreased in the obstructed kidney in mice with unilateral ureteral obstruction. Biochemical inhibition of constitutive NOS did not modulate renal injury after 14 days of unilateral ureteral obstruction. In contrast to previous findings with iNOS knockout mice, dietary supplementation with L-arginine had no effect on the degree of fibrosis in the obstructed kidney in SMLT treated C57BL/6J or eNOS knockout mice. We conclude that NO derived from eNOS within the kidney has a pivotal role in protecting against renal fibrosis in response to unilateral ureteral obstruction.

Chronic diabetic nephropathy: role of inducible nitric oxide synthase.

Nitric oxide (NO) is a multifunctional mediator that has been implicated in the short-term hemodynamic alterations that occur in acute streptozocin (STZ)-induced diabetes. We investigated the role of NO produced by inducible nitric oxide synthase (iNOS) in chronic STZ diabetic nephropathy. Diabetes was induced in C57BL/6 and iNOS knockout (KO) mice with two intraperitoneal injections of STZ, 100 mg/kg. Animals were maintained without insulin treatment for 40 weeks. There were no significant differences between the strains in blood urea nitrogen (BUN), serum creatinine or glucose concentration, or urinary protein excretion during the entire observation period. Urinary nitrite + nitrate excretion was significantly lower in iNOS KO mice compared to control animals at all time points; in C57 mice, urinary nitrite declined progressively with more prolonged duration of diabetes. Renal hypertrophy (kidney weight/body weight) was noted in both strains of mice. However, histopathological assessment of renal tissue specimens at 16 and 40 weeks demonstrated increased mesangial hypercellularity and expansion as well as more prominent tubulointerstitial fibrosis in iNOS KO versus C57 mice. These changes were accompanied by increased interstitial deposition of type I collagen at 16 and 40 weeks in iNOS KO mice. Glomerular basement membrane staining for type IV collagen was also increased at 40 weeks in diabetic iNOS KO mice. While iNOS protein was undetectable in any of the kidney specimens obtained from either strain, eNOS was present throughout the course of chronic STZ diabetes. Moreover, eNOS expression was significantly increased by approximately 40% at 16 and 40 weeks of observation in iNOS KO versus C57 mice. There was no difference in renal cortical malondialdehyde content between the strains early or late in the disease course. In time control animals, there was no evidence of renal histopathological damage in iNOS KO or C57 mice after 40 weeks. We conclude that iNOS-derived NO modulates glomerulosclerosis and tubulointerstitial fibrosis in chronic STZ nephropathy. This action is probably a result of the direct actions of NO on the synthesis and degradation of extracellular matrix proteins.