Images of the month: Crystalglobulin-induced nephropathy.

We report a patient with chronic diabetes and was referred for recent onset proteinuria. Light microscopy of the renal biopsy specimen showed mildly expanded mesangium with mesangial hypercellularity and segmental sclerosis, features compatible with diabetic glomerulosclerosis. However, crystalglobulin-induced nephropathy with crystal deposit was identified on electron microscopy. Renal biopsy is often performed for diabetic patients who present with proteinuria and light microscopy often shows features of diabetic glomerulosclerosis. Additional information may occasionally be revealed on electron microscopy, altering the subsequent plan of management.

Ultrasound-guided synovial Tru-cut biopsy: indications, technique, and outcome in 111 cases.

OBJECTIVE: To investigate the diagnostic performance of ultrasound-guided synovial biopsy. METHODS: Clinical notes, pathology and microbiology reports, ultrasound and other imaging studies of 100 patients who underwent 111 ultrasound-guided synovial biopsies were reviewed. Biopsies were compared with the final clinical diagnosis established after synovectomy (n = 43) or clinical/imaging follow-up (n = 57) (mean 30 months). RESULTS: Other than a single vasovagal episode, no complication of synovial biopsy was encountered. One hundred and seven (96 %) of the 111 biopsies yielded synovium histologically. Pathology ± microbiology findings for these 107 conclusive biopsies comprised synovial tumour (n = 30, 28 %), synovial infection (n = 18, 17 %), synovial inflammation (n = 45, 42 %), including gouty arthritis (n = 3), and no abnormality (n = 14, 13 %). The accuracy, sensitivity, and specificity of synovial biopsy was 99 %, 97 %, and 100 % for synovial tumour; 100 %, 100 %, and 100 % for native joint infection; and 78 %, 45 %, and 100 % for prosthetic joint infection. False-negative synovial biopsy did not seem to be related to antibiotic therapy. CONCLUSION: Ultrasound-guided Tru-cut synovial biopsy is a safe and reliable technique with a high diagnostic yield for diagnosing synovial tumour and also, most likely, for joint infection. Regarding joint infection, synovial biopsy of native joints seems to have a higher diagnostic yield than that for infected prosthetic joints. KEY POINTS: • Ultrasound-guided Tru-cut synovial biopsy has high accuracy (99 %) for diagnosing synovial tumour. • It has good accuracy, sensitivity, and high specificity for diagnosis of joint infection. • Synovial biopsy of native joints works better than biopsy of prosthetic joints. • A negative synovial biopsy culture from a native joint largely excludes septic arthritis. • Ultrasound-guided Tru-cut synovial biopsy is a safe and well-tolerated procedure.

Histopathological correlations of islet amyloidosis with apolipoprotein E polymorphisms in type 2 diabetic Chinese patients.

OBJECTIVE: Islet amyloidosis and arteriosclerosis are histopathological hallmarks in type 2 diabetes. Apolipoprotein E (ApoE) is a common component of amyloidosis. ApoE [Latin Small Letter Open E]4 allele is associated with arteriosclerosis and cerebral amyloidosis in Alzheimer disease. We examined the correlations of ApoE polymorphisms with islet amyloidosis in type 2 diabetes. METHODS: Genomic DNA samples were obtained from 117 autopsy cases with type 2 diabetes and 209 nondiabetic cases. ApoE genotypes and amylin gene mutations were determined by polymerase chain reaction-ligase detection reaction analysis. Islet amyloidosis and arteriosclerosis were evaluated by staining of thioflavin T, amylin, ApoE, and amyloid P component. RESULTS: In the diabetic group, 33.3% in group [Latin Small Letter Open E]2 ([Latin Small Letter Open E]2[Latin Small Letter Open E]2, [Latin Small Letter Open E]2[Latin Small Letter Open E]3), 23.6% in group [Latin Small Letter Open E]3 ([Latin Small Letter Open E]3[Latin Small Letter Open E]3), and 62.5% in group [Latin Small Letter Open E]4 ([Latin Small Letter Open E]4[Latin Small Letter Open E]4, [Latin Small Letter Open E]3[Latin Small Letter Open E]4) had islet amyloidosis. After adjustment for confounders, group [Latin Small Letter Open E]4 had an odds ratio of 7.0 (95% confidence interval, 1.3-38.0; P = 0.023) in having islet amyloidosis compared to group [Latin Small Letter Open E]3. Diabetic cases with islet amyloidosis had more severe arteriosclerosis (P = 0.0111), arteriolar hyalinosis (P = 0.0369), and interstitial fibrosis (P = 0.0188) than those without amyloidosis. Immunoreactivity of both ApoE and amyloid P component was detected in islet amyloid deposits and arteriosclerotic lesions. CONCLUSIONS: In type 2 diabetes, islet amyloidosis and arteriosclerosis share common pathophysiological features with ApoE [Latin Small Letter Open E]4 as a probable linking factor.

Intra-abdominal testicular seminoma in a woman with testicular feminization syndrome.

We report a case of intra-abdominal testicular tumor in a 36-year-old married lady presenting with chief complaints of primary amenorrhea. The patient was later diagnosed with testicular feminization syndrome, a form of male pseudohermaphroditism. This testicular tumor was histologically proven as seminoma. Due to rarity, imaging findings in patients with testicular feminization syndrome and intraabdominal testicular tumor have been poorly documented. So far, only one case report had described the combined role of CT and MR imaging in intraabdominal testicular sex-cord stromal tumor. To our knowledge, this case is first to document USG and MR imaging in addition to MR spectroscopy features in intraabdominal testicular seminoma.

Fatty acids inhibit insulin-mediated glucose transport associated with actin remodeling in rat L6 muscle cells.

In skeletal muscle cells, insulin stimulates cytoskeleton actin remodeling to facilitate the translocation of glucose transporter GLUT4 to plasma membrane. Defect of insulin-induced GLUT4 translocation and actin remodeling may cause insulin resistance. Free fatty acids cause insulin resistance in skeletal muscle. The aim of this study was to investigate the effects of fatty acids on glucose transport and actin remodeling. Differentiated L6 muscle cells expressing c-myc epitope-tagged GLUT4 were treated with palmitic acid, linoleic acid and oleic acid. Surface GLUT4 and 2-deoxyglucose uptake were measured in parallel with the morphological imaging of actin remodeling and GLUT4 immunoreactivity with fluorescence, confocal and transmission electron microscopy. Differentiated L6 cells showed concentration responses of insulin-induced actin remodeling and glucose uptake. The ultrastructure of insulin-induced actin remodeling was cell projections clustered with actin and GLUT4. Acute and chronic treatment with the 3 fatty acids had no effect on insulin-induced actin remodeling and GLUT4 immunoreactivity. However, insulin-mediated glucose uptake significantly decreased by palmitic acid (25, 50, 75, 100 µmol/L), oleic acid (180, 300 µmol/L) and linoleic acid (120, 180, 300 µmol/L). Oleic acid (120, 300 µmol/L) and linoleic acid (300 µmol/L), but not palmitic acid, significantly decreased insulin-mediated GLUT4 translocation. These data suggest that fatty acids inhibit insulin-induced glucose transport associated with actin remodeling in L6 muscle cells.

Up-regulated pancreatic tissue microRNA-375 associates with human type 2 diabetes through beta-cell deficit and islet amyloid deposition.

OBJECTIVES: The aim of this study was to examine correlations of the islet-specific microRNA-375 expression to islet amyloid formation and pancreatic islet damage in human type 2 diabetes. METHODS: Autopsy pancreas samples from 40 type 2 diabetic and 15 nondiabetic patients were used to detect microRNA-375 expression using real-time quantitative polymerase chain reaction. Serial paraffin sections of the corresponding type 2 diabetic and nondiabetic cases were stained by immunofluorescence to evaluate for amylin expression, amyloid formation, and proportions of alpha and beta cells. RESULTS: Pancreatic microRNA-375 expression was increased in type 2 diabetic patients comparing with the nondiabetic patients (median, 4.02 for the diabetic patients vs 0.92 for the nondiabetic patients; P = 0.0001). The median was 6.14 for the diabetic patients with islet amyloid and 3.51 for islet amyloid-free diabetic patients. The expression level of microRNA-375 correlated positively with the frequency and the severity of islet amyloid formation and negatively with proportions of islet beta-cells and amylin-positive area, and islet mitochondria density. CONCLUSIONS: Up-regulated microRNA-375 is associated with type 2 diabetes and pancreatic islet amyloid formation and beta-cell deficit. microRNA-375 may serve as a biomarker for known and novel pathways in the pathogenesis of type 2 diabetes related to islet amyloid deposition and beta-cell dysfunction.

The Oxford IgA nephropathy clinicopathological classification is valid for children as well as adults.

To study the predictive value of biopsy lesions in IgA nephropathy in a range of patient ages we retrospectively analyzed the cohort that was used to derive a new classification system for IgA nephropathy. A total of 206 adults and 59 children with proteinuria over 0.5 g/24 h/1.73 m(2) and an eGFR of stage-3 or better were followed for a median of 69 months. At the time of biopsy, compared with adults children had a more frequent history of macroscopic hematuria, lower adjusted blood pressure, and higher eGFR but similar proteinuria. Although their outcome was similar to that of adults, children had received more immunosuppressants and achieved a lower follow-up proteinuria. Renal biopsies were scored for variables identified by an iterative process as reproducible and independent of other lesions. Compared with adults, children had significantly more mesangial and endocapillary hypercellularity, and less segmental glomerulosclerosis and tubulointerstitial damage, the four variables previously identified to predict outcome independent of clinical assessment. Despite these differences, our study found that the cross-sectional correlation between pathology and proteinuria was similar in adults and children. The predictive value of each specific lesion on the rate of decline of renal function or renal survival in IgA nephropathy was not different between children and adults.

Intrarenal expression of microRNAs in patients with IgA nephropathy.

MicroRNAs (miRNAs) are noncoding, single-stranded RNA molecules that have important roles in a number of physiological and pathological processes. Previous studies have proved that miRNAs targeting ZEB1 and ZEB2 may repress epithelial-to-mesenchymal transition. In this work, we studied the intrarenal expression of miR-200 family, miR-205 and miR-192 in patients with immunoglobulin A (IgA) nephropathy. We studied 43 patients with biopsy-proven IgA nephropathy (IgA group). The intrarenal expression of miRNAs was quantified and compared with that of 15 patients with noninflammatory glomerulosclerosis (GS group) and 20 patients with nephrectomy for kidney cancer as controls (CTL group). The level of intrarenal miR-200c was downregulated, whereas the levels of intrarenal miR-141, miR-205 and miR-192 were upregulated in IgA but not GS group. Proteinuria significantly correlated with the intrarenal expression of miR-200c (r=-0.324, P=0.011) and glomerular filtration rate (GFR) significantly correlated with the intrarenal expression of miR-205 (r=-0.280, P=0.030). The degree of tubulointerstitial scarring correlated with miR-205 expression (r=0.389, P=0.021), whereas glomerulosclerosis correlated with miR-192 expression (r=-0.311, P=0.045). The rate of GFR decline significantly correlated with the intrarenal expression of miR-192 (r=0.373, P=0.015). The intrarenal expression of E-cadherin significantly correlated with the intrarenal expression of miR-200c (r=0.392, P=0.002). The results show that intrarenal expression of miR-200c, miR-141, miR-205 and miR-192 was diversely regulated and correlated with disease severity and progression in patients with IgA nephropathy. These miRNA species may be important in the pathogenesis and progression of IgA nephropathy.

The Oxford classification of IgA nephropathy: pathology definitions, correlations, and reproducibility.

Pathological classifications in current use for the assessment of glomerular disease have been typically opinion-based and built on the expert assumptions of renal pathologists about lesions historically thought to be relevant to prognosis. Here we develop a unique approach for the pathological classification of a glomerular disease, IgA nephropathy, in which renal pathologists first undertook extensive iterative work to define pathologic variables with acceptable inter-observer reproducibility. Where groups of such features closely correlated, variables were further selected on the basis of least susceptibility to sampling error and ease of scoring in routine practice. This process identified six pathologic variables that could then be used to interrogate prognostic significance independent of the clinical data in IgA nephropathy (described in the accompanying article). These variables were (1) mesangial cellularity score; percentage of glomeruli showing (2) segmental sclerosis, (3) endocapillary hypercellularity, or (4) cellular/fibrocellular crescents; (5) percentage of interstitial fibrosis/tubular atrophy; and finally (6) arteriosclerosis score. Results for interobserver reproducibility of individual pathological features are likely applicable to other glomerulonephritides, but it is not known if the correlations between variables depend on the specific type of glomerular pathobiology. Variables identified in this study withstood rigorous pathology review and statistical testing and we recommend that they become a necessary part of pathology reports for IgA nephropathy. Our methodology, translating a strong evidence-based dataset into a working format, is a model for developing classifications of other types of renal disease.

The Oxford classification of IgA nephropathy: rationale, clinicopathological correlations, and classification.

IgA nephropathy is the most common glomerular disease worldwide, yet there is no international consensus for its pathological or clinical classification. Here a new classification for IgA nephropathy is presented by an international consensus working group. The goal of this new system was to identify specific pathological features that more accurately predict risk of progression of renal disease in IgA nephropathy, thus enabling both clinicians and pathologists to improve individual patient prognostication. In a retrospective analysis, sequential clinical data were obtained on 265 adults and children with IgA nephropathy who were followed for a median of 5 years. Renal biopsies from all patients were scored by pathologists blinded to the clinical data for pathological variables identified as reproducible by an iterative process. Four of these variables: (1) the mesangial hypercellularity score, (2) segmental glomerulosclerosis, (3) endocapillary hypercellularity, and (4) tubular atrophy/interstitial fibrosis were subsequently shown to have independent value in predicting renal outcome. These specific pathological features withstood rigorous statistical analysis even after taking into account all clinical indicators available at the time of biopsy as well as during follow-up. The features have prognostic significance and we recommended they be taken into account for predicting outcome independent of the clinical features both at the time of presentation and during follow-up. The value of crescents was not addressed due to their low prevalence in the enrolled cohort.

Urinary FOXP3 mRNA in patients with lupus nephritis--relation with disease activity and treatment response.

OBJECTIVE: Regulatory T lymphocytes (Tregs) probably play an important role in the pathogenesis of SLE. METHODS: We quantified messenger RNA (mRNA) expression of FOXP3, a critical regulator for the development and function of Tregs, in the urinary sediment of 25 subjects with active lupus nephritis (LN), 17 with inactive lupus and 7 healthy subjects. RESULTS: We found that the expression level of FOXP3 was significantly higher in urine from patients with active LN than from subjects with inactive lupus and healthy controls (24.5 +/- 45.8 vs 0.8 +/- 1.0 vs 0.6 +/- 0.8 copy; P < 0.001). In the active group, urinary FOXP3 mRNA expression level was higher in patients with proliferative LN than non-proliferative nephritis (34.6 +/- 56.3 vs 2.7 +/- 2.1 copy; P = 0.019). Urinary FOXP3 mRNA level significantly correlated with SLEDAI (r = 0.668; P < 0.001) and proteinuria (r = 0.414; P = 0.006). In the active group, urinary FOXP3 mRNA level also significantly correlated with histological activity index (r = 0.541; P = 0.009) and marginally with intra-renal FOXP3 mRNA level (r = 0.360; P = 0.08). Urinary FOXP3 mRNA in patients with no response to therapy was higher than those with partial response or complete response (57.6 +/- 69.8 vs 2.4 +/- 1.9 copies; P = 0.02). CONCLUSION: We concluded that urinary FOXP3 mRNA is markedly up-regulated in patients with active LN, and the level of expression is closely correlated with the clinical and histological disease activity. A high urinary FOXP3 mRNA in LN predicts a poor therapeutic response. Measurement of FOXP3 mRNA in urine sediment may be a non-invasive biomarker for assessing the severity and risk stratification in LN.

Progressive increase of genetic alteration in urinary bladder cancer by combined allelotyping analysis and comparative genomic hybridization.

Bladder cancer is the ninth most common cancer in the world. Urothelial carcinoma (formerly known as transitional cell carcinoma) comprises the majority of bladder cancers. In order to decipher the genetic alteration leading to the carcinogenesis of urothelial cancer, we performed genome-wide allelotyping analysis using 384 microsatellite markers spanning 22 autosomes together with comparative genomic hybridization (CGH) in 21 urothelial cancer. High frequency of allelic imbalance was observed in chromosome arm 1q (61.9%), 3p (61.9%), 4q (66.67%), 8p (57.14%), 9p (76.2%) and 9q (66.67%). Allelic imbalance with frequency above average was also observed in chromosome arm 2q, 10p, 10q, 11p, 11q, 12q, 13q, 15q, 17p and 19q. The allelic imbalance of each case and fractional allelic loss for each chromosome was associated with higher tumor grade and stage (P<0.05). We have also delineated several minimal deletion regions on chromosome 3p, 4q, 8p, 9p, 9q, 11p, 13q, 16q and 17p. By CGH analysis, common chromosomal alterations included gain of 1p, 1q, 12q, 16p, 17q and 19p as well as loss of 4q and 9p in most of the cases. Our findings may provide valuable information to locate putative oncogenes and tumor suppressor genes in the carcinogenesis of bladder cancer in this locality.

Apolipoprotein E polymorphism and expression in type 2 diabetic patients with nephropathy: clinicopathological correlation.

BACKGROUND: Diabetic nephropathy represents a heterogeneous group of renal pathologies that may be associated with genetic susceptibility. There have been clinical reports on the risk association of diabetic nephropathy with an apolipoprotein E (ApoE) exon 4 polymorphism although its correlations with renal histopathological changes have not been explored. METHODS: A total of 213 adult autopsies with type 2 diabetes and 111 non-diabetic control cases were analysed. Genomic DNA samples were obtained from spleen tissues. The ApoE genotype was determined by PCR-LDR analysis. Histopathological examination of kidney sections was performed in a subset of 51 diabetic and 111 control cases. ApoE protein expression in diabetic carriers with similar clinical status was examined by immunohistochemical staining. RESULTS: In type 2 diabetes, epsilon2 carriers (P = 0.04; odds ratio = 5.42; 95% CI: 1.10-26.8) and epsilon3/epsilon4 (P = 0.04; odds ratio = 22.5; 95% CI: 1.11-454.90) genotype carriers were more likely to have glomerular hypertrophy than were epsilon3/epsilon3 carriers. The epsilon2 carriers showed an increase in glomerular ApoE protein expression. A correlation between ApoE genotype and nodular glomerulosclerosis was not found. CONCLUSIONS: Our findings confirm the risk association of the ApoE polymorphism with diabetic nephropathy in clinical studies and is the first study demonstrating the correlations between ApoE genotypes, protein expression and structural changes in diabetic nephropathy.

Podocyte injury induced by mesangial-derived cytokines in IgA nephropathy.

BACKGROUND: We have previously documented that human mesangial cell (HMC)-derived tumour necrosis factor-alpha (TNF-alpha) is an important mediator involved in the glomerulo-tubular communication in the development of interstitial damage in IgA nephropathy (IgAN). With the strategic position of podocytes, we further examined the function of podocytes in IgAN. METHODS: Podocyte markers were examined in renal tissues by immunofluorescence. In vitro experiments were conducted with podocytes cultured with polymeric IgA (pIgA) or conditioned medium prepared from HMC incubated with pIgA (IgA-HMC conditioned medium). RESULTS: Glomerular immunostaining for nephrin or ezrin was significantly weaker in patients with IgAN. The immunostaining of IgA and nephrin was distinctly separate with no co-localization. In vitro experiments revealed no effect of pIgA on the expression of these podocyte proteins as IgA from IgAN patients did not bind to podocytes. In contrast, IgA conditioned medium prepared from IgAN patients down-regulated the expression of these podocyte proteins as well as other podocyte markers (podocin and synaptopodin) in cultured podocytes. The mRNA expression of nephrin, erzin, podocin but not synaptopodin correlated with the degree of proteinuria and creatinine clearance. The down-regulation was reproducible in podocytes cultured with TNF-alpha or transforming growth factor-beta (TGF-beta) at concentration comparable to that in the IgA-HMC conditioned medium. The expression of these podocyte proteins was restored partially with a neutralizing antibody against TNF-alpha or TGF-beta and fully with combination of both antibodies. CONCLUSION: Our finding suggests podocyte markers are reduced in IgAN. An in vitro study implicates that humoral factors (predominantly TNF-alpha and TGF-beta) released from mesangial cells are likely to alter the glomerular permeability in the event of proteinuria and tubulointerstitial injury in IgAN.

Amyloid oligomers in diabetic and nondiabetic human pancreas.

The amyloid hypothesis of type 2 diabetes mellitus postulates that elevated levels of normally expressed monomeric proteins of human islet amyloid polypeptide (hIAPP) trigger oligomerization that independently causes fibril formation and disease progression. The aim of this study was to demonstrate the existence of amyloid oligomers in human pancreatic islets. Human pancreas tissues were obtained at autopsy of 8 nondiabetic control subjects (mean age = 75.8 +/- 11.7 years, 4 males), 8 type 2 diabetic cases without islet amyloid (mean age = 78.8 +/- 8.5 years, 4 males), and 8 type 2 diabetic patients with islet amyloid (mean age = 73.7 +/- 14.2 years, 4 males). Several markers for insulin, IAPP, amyloid fibrils (thioflavin T), and apoptosis (cleaved caspase-3) were used in combination with an oligomer-specific antibody. Two distinct forms of oligomers were found in pancreatic islets. Small spherical puncta were found in approximately 3% to 20% of the islet cells of nondiabetic subjects, and large curvilinear structures as extracellular oligomers were identified frequently in diabetic islets. Large oligomers were spatially localized adjacent to amyloid fibrils and were associated with apoptosis. This report demonstrates the presence of 2 morphologic classes of amyloid oligomers in human pancreatic islets. The observations warrant function studies to investigate the clinical implications of the amyloid oligomerization in the pathogenesis of type 2 diabetes.

Higher islet amyloid load in men than in women with type 2 diabetes mellitus.

OBJECTIVES: Type 2 diabetes mellitus is characterized histopathologically by islet amyloid deposits formed from islet amyloid polypeptide. The aim of this study was to investigate sex difference in islet amyloid of type 2 diabetic patients. METHODS: Pancreas specimens were collected from 235 autopsies with type 2 diabetes mellitus. Islet amyloid was identified with Congo red stain. The load of islet amyloid deposits was assessed by prevalence (percentage of cases with islet amyloid deposits), frequency (percentage of islets containing amyloid deposits), and severity (percentage of islet area occupied by amyloid deposits). RESULTS: Women (n = 80) and men (n = 155) had similar age of death, duration of diabetes, body mass index, and hemoglobin (Hb)A1c level. Islet amyloid was found in 30.0% of the women and in 44.5% of the men (P = 0.035). None of 9 women younger than 50 years had islet amyloid. Frequency of amyloid-affected islets was 31.5% +/- 13.1% in women and 41.1% +/- 14.3% in men (P = 0.008). Severity of amyloid-affected islet area was 29.0% +/- 12.5% in women and 38.5% +/- 14.6% in men (P = 0.007). CONCLUSIONS: Sex is a determinant of the development of islet amyloid in type 2 diabetes mellitus. This sex difference in islet amyloid may be related to a potential benefit of female sex hormones.

Fat redistribution and adipocyte transformation in uninephrectomized rats.

Dyslipidemia complicates renal function leading to disturbances of major homeostatic organs in the body. Here we examined the effect of chronic renal dysfunction induced by uninephrectomy on fat redistribution and lipid peroxidation in rats treated with an angiotensin-converting enzyme (ACE) inhibitor (lisinopril) for up to 10 months. Uninephrectomized rats developed fat redistribution and hypercholesterolemia typical of chronic renal failure when compared with sham-operated rats or lisinopril-treated uninephrectomized rats. The weight of the peri-renal fat was significantly less in the untreated compared to the lisinopril-treated uninephrectomized rats or those rats with a sham operation. We also found that there was a shift of heat-protecting unilocular adipocytes to heat-producing multilocular fat cells in the untreated uninephrectomized rats. Similarly in these rats we found a shift of subcutaneous and visceral fat to ectopic fat with excessive lipid accumulation and lipofuscin pigmentation. Lisinopril treatment prevented fat redistribution or transformation and lipid peroxidation. This study shows that ACE inhibition may prevent the fat anomalies associated with chronic renal dysfunction.

Activation of podocytes by mesangial-derived TNF-alpha: glomerulo-podocytic communication in IgA nephropathy.

We have previously documented that human mesangial cell (HMC)-derived TNF-alpha is an important mediator involved in the glomerulo-tubular communication in the development of interstitial damage in IgA nephropathy (IgAN). With the strategic position of podocytes, we further examined the role of mesangial cells in the activation of podocytes in IgAN. There was no binding of IgA from patients with IgAN to podocytes. Podocytes cultured with IgA from patients with IgAN did not induce the release of growth factors or cytokines. Furthermore, podocytes did not express mRNA of known IgA receptors. In contrast, IgA-conditioned medium (IgA-HMC medium) prepared by culturing HMC with IgA from patients with IgAN for 48 h significantly increased the gene expression and protein synthesis of TNF-alpha by podocytes with a 17-fold concentration above that of IgA-HMC medium. The upregulation of TNF-alpha expression by podocyte was only abolished by a neutralizing antibody against TNF-alpha but not by other antibodies. Exogenous TNF-alpha upregulated the synthesis of TNF-alpha by podocytes in an autocrine fashion. IgA-HMC medium prepared with IgA from patients with IgAN also significantly upregulated the expression of both TNF-alpha receptor 1 and 2 in podocytes. Our in vitro finding suggests podocytes may play a contributory role in the development of interstitial damage in IgAN by amplifying the activation of tubular epithelial cells with enhanced TNF-alpha synthesis after inflammatory changes of HMC.