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1.  First Real-World Insights into Belimumab Use and Outcomes in Routine Clinical Care of Systemic Lupus Erythematosus in Germany: Results from the OBSErve Germany Study 
Rheumatology and Therapy  2016;3(2):271-290.
OBSErve Germany was the first observational study of belimumab as add-on treatment for systemic lupus erythematosus (SLE) in routine clinical care in Germany, retrospectively collecting data from 102 SLE patients, 6 months before and after belimumab initiation. Most patients had moderate or severe SLE and several SLE manifestations. After 6 months of belimumab treatment, 78% of patients showed an improvement in overall disease activity of at least 20% in their physician’s judgment and for 42% of patients the improvement was at least 50%. Similar results were observed for the most common manifestations: arthritis, fatigue, rash, alopecia, increased anti-dsDNA antibody levels, and low complement. The SLE Disease Activity Index (SLEDAI/SELENA-SLEDAI) decreased from 10.6 to 5.6 (n = 65), with other indices also showing improvement. A notable dose reduction was seen for concomitant oral corticosteroids, from 13.7 to 7.6 mg/day overall (n = 91), and from 17.5 to 8.6 mg/day in patients with a high corticosteroid dose at belimumab initiation (≥7.5 mg; n = 63). Six patients discontinued belimumab therapy within 6 months. Overall, belimumab showed promising results for SLE patients in real-world settings. After 6 months of belimumab treatment, disease activity and corticosteroid use were reduced. The discontinuation rate was low and belimumab appeared to be well tolerated.
Funding GlaxoSmithKline UK.
PMCID: PMC5127971  PMID: 27804088
B cell targeted therapy; Belimumab; Observational study; SLE; Systemic lupus erythematosus
2.  A Phase 3, Randomized, Placebo-Controlled Study of Belimumab, a Monoclonal Antibody That Inhibits BLyS, in Patients With Systemic Lupus Erythematosus 
Arthritis and rheumatism  2011;63(12):3918-3930.
To assess the efficacy/safety of the B-lymphocyte stimulator inhibitor belimumab/standard-of-care (SOC) versus placebo/SOC in active systemic lupus erythematosus (SLE).
In a multicenter, randomized, controlled, phase 3 trial, 819 antinuclear antibody- or anti-dsDNA-positive SLE patients with Safety of Estrogens in Lupus Erythematosus National Assessment–SLE Disease Activity Index (SELENA-SLEDAI) ≥ 6 were randomized (1:1:1 ratio) to receive intravenous belimumab 1 or 10 mg/kg, or placebo on days 0, 14, and 28, and then every 28 days for 72 weeks. Primary efficacy analyses: SLE Responder Index (SRI) at week 52 (≥ 4-point reduction in SELENA-SLEDAI; no new British Isles Lupus Assessment Group A and < 2 new B organ domain scores; no worsening in Physician’s Global Assessment).
Belimumab 10 mg/kg plus SOC met the primary efficacy endpoint: significantly greater SRI response at week 52 than placebo (43.2% versus 33.5%; P = 0.017); the rate with belimumab 1 mg/kg was 40.6% (P = 0.089). Week-76 response rates: 32.4%, 39.1%, and 38.5% with placebo, and belimumab 1 and 10 mg/kg, respectively. In post-hoc sensitivity analyses evaluating higher SELENA-SLEDAI thresholds, belimumab 10 mg/kg achieved better discrimination at weeks 52/76. Risk of severe SELENA-SLEDAI flares over 76 weeks was reduced with belimumab 1 mg/kg (34%; P = 0.023) and 10 mg/kg (23%; P = 0.13). Serious and severe adverse events including infections, laboratory abnormalities, malignancies, and deaths, were comparable across groups.
Belimumab plus SOC significantly improved SRI response rate, reduced SLE disease activity and severe flares, and was generally well-tolerated in SLE.
PMCID: PMC5007058  PMID: 22127708
3.  Clinical Spectrum Time Course in Anti Jo-1 Positive Antisynthetase Syndrome 
Medicine  2015;94(32):e1144.
Anti Jo-1 antibodies are the main markers of the antisynthetase syndrome (ASSD), an autoimmune disease clinically characterized by the occurrence of arthritis, myositis, and interstitial lung disease (ILD). These manifestations usually co-occur (for practical purpose complete forms) in the same patient, but cases with only 1 or 2 of these findings (for practical purpose incomplete forms) have been described. In incomplete forms, the ex novo occurrence of further manifestations is possible, although with frequencies and timing not still defined. The aim of this international, multicenter, retrospective study was to characterize the clinical time course of anti Jo-1 positive ASSD in a large cohort of patients. Included patients should be anti Jo-1 positive and with at least 1 feature between arthritis, myositis, and ILD. We evaluated the differences between complete and incomplete forms, timing of clinical picture appearance and analyzed factors predicting the appearance of further manifestations in incomplete ASSD. Finally, we collected 225 patients (58 males and 167 females) with a median follow-up of 80 months. At the onset, complete ASSD were 44 and incomplete 181. Patients with incomplete ASSD had frequently only 1 of the classic triad findings (110 cases), in particular, isolated arthritis in 54 cases, isolated myositis in 28 cases, and isolated ILD in 28 cases. At the end of follow-up, complete ASSD were 113, incomplete 112. Only 5 patients had an isolated arthritis, only 5 an isolated myositis, and 15 an isolated ILD. During the follow-up, 108 patients with incomplete forms developed further manifestations. Single main feature onset was the main risk factor for the ex novo appearance of further manifestation. ILD was the prevalent ex novo manifestation (74 cases). In conclusion, ASSD is a condition that should be carefully considered in all patients presenting with arthritis, myositis, and ILD, even when isolated. The ex novo appearance of further manifestations in patients with incomplete forms is common, thus indicating the need for an adequate clinical and instrumental follow-up. Furthermore, the study clearly suggested that in ASSD multidisciplinary approach involving Rheumatology, Neurology, Pneumology, and Internal Medicine specialists is mandatory.
PMCID: PMC4616698  PMID: 26266346
4.  Impact of switching from mycophenolate mofetil to enteric-coated mycophenolate sodium on gastrointestinal side effects in patients with autoimmune disease: a Phase III, open-label, single-arm, multicenter study 
The purpose of this study was to assess changes in gastrointestinal symptom severity in patients with autoimmune disease who were switched from mycophenolate mofetil to enteric-coated mycophenolate sodium (EC-MPS).
In this national, explorative, single-arm study, 111 patients were enrolled and switched to equimolar EC-MPS at baseline. The primary endpoint was change in the Gastrointestinal Symptom Rating Scale (GSRS) total score after 6–8 weeks of treatment (Visit 2). The optional follow-up visit was 6–12 weeks after completion of the study (Visit 2). Secondary endpoints were changes in GSRS subscale score; changes in gastrointestinal-related quality of life measured by the Gastrointestinal Quality of Life Index (GIQLI); and general health-related quality of life (HRQoL) measured by Psychological General Well-Being Index and assessment of overall treatment effect (OTE). Change was evaluated by paired t-tests.
At Visit 2, the mean ± standard deviation GSRS total score improved from 2.28±1.13 to 2.02±0.93 points. The change (−0.28±0.92 points, P=0.002) was statistically significant. The change at the follow-up visit (−0.36±0.94 points, P=0.001) was statistically significant and more than the minimal clinical important difference. GSRS subscores showed statistically significant and clinically relevant improvement for abdominal pain (−0.51±1.2 points, P<0.001) and indigestion (−0.42±1.33 points, P=0.002). Overall GIQLI score showed significant improvement from baseline to Visit 2 (−5.8±18.6 points, P=0.002). Per OTE, improvement was reported in 44.1% and 34.2% patients as rated by physicians and patients, respectively. The majority of patients (55%) reported OTE-HRQoL as unchanged. Diarrhea and nausea were the commonly reported adverse events.
Patients switched to EC-MPS experienced less gastrointestinal symptom burden and showed improvement in HRQoL.
PMCID: PMC4516030  PMID: 26229499
mycophenolate mofetil; enteric-coated mycophenolate sodium; autoimmune disease; patient-reported outcome; health-related quality of life
5.  Epigenetic Aspects of Systemic Lupus Erythematosus 
Rheumatology and Therapy  2015;2(1):33-46.
Autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis, multiple sclerosis, autoimmune hepatitis, and inflammatory bowel disease have complex pathogeneses and the courses of events leading to these diseases are not well understood. The immune surveillance is a delicate balance between self and foreign as well as between tolerance and immune response. Exposure to certain environmental factors may impair this equilibrium, leading to autoimmune diseases, cancer, and the so-called “lifestyle diseases” such as atherosclerosis, heart attack, stroke, and obesity, among others. These external stimuli may also alter the epigenetic status quo and may trigger autoimmune diseases such as SLE in genetically susceptible individuals. This review aims to highlight the role of epigenetic (dys-)regulation in the pathogenesis of SLE.
Electronic supplementary material
The online version of this article (doi:10.1007/s40744-015-0014-y) contains supplementary material, which is available to authorized users.
PMCID: PMC4883254  PMID: 27747498
Epigenetics; Gene imprinting; Histone modifications; Methylation; Non-coding RNA; Nucleosome remodeling; Systemic lupus erythematosus (SLE)
7.  Irritable bowel syndrome and organic diseases: A comparative analysis of esophageal motility 
AIM: To assess the esophageal motility in patients with irritable bowel syndrome (IBS) and to compare those with patients with autoimmune disorders.
METHODS: 15 patients with IBS, 22 with systemic lupus erythematosus (SLE) and 19 with systemic sclerosis (SSc) were prospectively selected from a total of 115 patients at a single university centre and esophageal motility was analysed using standard manometry (Mui Scientific PIP-4-8SS). All patients underwent esophago-gastro-duodenoscopy before entering the study so that only patients with normal endoscopic findings were included in the current study. All patients underwent a complete physical, blood biochemistry and urinary examination. The grade of dysphagia was determined for each patient in accordance to the intensity and frequency of the presented esophageal symptoms. Furthermore, disease activity scores (SLEDAI and modified Rodnan score) were obtained for patients with autoimmune diseases. Outcome parameter: A correlation coefficient was calculated between amplitudes, velocity and duration of the peristaltic waves throughout esophagus and patients’ dysphagia for all three groups.
RESULTS: There was no statistical difference in the standard blood biochemistry and urinary analysis in all three groups. Patients with IBS showed similar pathologic dysphagia scores compared to patients with SLE and SSc. The mean value of dysphagia score was in IBS group 7.3, in SLE group 6.73 and in SSc group 7.56 with a P-value > 0.05. However, the manometric patterns were different. IBS patients showed during esophageal manometry peristaltic amplitudes at the proximal part of esophagus greater than 60 mmHg in 46% of the patients, which was significant higher in comparison to the SLE (11.8%) and SSc-Group (0%, P = 0.003). Furthermore, IBS patients showed lower mean resting pressure of the distal esophagus sphincter (Lower esophageal sphincter, 22 mmHg) when compared with SLE (28 mmHg, P = 0.037) and SSc (26 mmHg, P = 0.052). 23.5% of patients with SLE showed amplitudes greater as 160 mmHg in the distal esophagus (IBS and SSc: 0%) whereas 29.4% amplitudes greater as 100 mmHg in the middle one (IBS: 16.7%, SSc: 5.9% respectively, P = 0.006). Patients with SSc demonstrated, as expected, in almost half of the cases reduced peristalsis or even aperistalsis in the lower two thirds of the esophagus. SSc patients demonstrated a negative correlation coefficient between dysphagia score, amplitude and velocity of peristaltic activity at middle and lower esophagus [r = -0.6, P < 0.05].
CONCLUSION: IBS patients have comparable dysphagia-scores as patients with autoimmune disorders. The different manometric patterns might allow differentiating esophageal symptoms based on IBS from other organic diseases.
PMCID: PMC3801311  PMID: 24151359
Irritable bowel syndrome; Systemic lupus erythematosus; Systemic sclerosis; Esophageal manometry; Dysphagia
8.  Autocrine CSF-1 and CSF-1 Receptor Co-expression Promotes Renal Cell Carcinoma Growth 
Cancer research  2011;72(1):187-200.
Renal cell carcinoma is increasing in incidence but the molecular mechanisms regulating its growth remain elusive. Co-expression of the monocytic growth factor CSF-1 and its receptor CSF-1R on renal tubular epithelial cells (TEC) will promote proliferation and anti-apoptosis during regeneration of renal tubules. Here we show that a CSF-1-dependent autocrine pathway is also responsible for the growth of renal cell carcinoma (RCC). CSF-1 and CSF-1R were co-expressed in RCC and TEC proximally adjacent to RCC. CSF-1 engagement of CSF-1R promoted RCC survival and proliferation and reduced apoptosis, in support of the likelihood that CSF-1R effector signals mediate RCC growth. In vivo CSF-1R blockade using a CSF-1R tyrosine kinase inhibitor decreased RCC proliferation and macrophage infiltration in a manner associated with a dramatic reduction in tumor mass. Further mechanistic investigations linked CSF-1 and EGF signaling in RCC. Taken together, our results suggest that budding RCC stimulates the proximal adjacent microenvironment in the kidney to release mediators of CSF-1, CSF-1R and EGF expression in RCC. Further, our findings imply that targeting CSF-1/CSF-1R signaling may be therapeutically effective in RCC.
PMCID: PMC3251714  PMID: 22052465
Tubular epithelial cells; Macrophages; Renal carcinoma; CSF-1R; CSF-1
9.  Role of MHC-Linked Susceptibility Genes in the Pathogenesis of Human and Murine Lupus 
Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the production of autoantibodies against nuclear antigens and a systemic inflammation that can damage a broad spectrum of organs. SLE patients suffer from a wide variety of symptoms, which can affect virtually almost any tissue. As lupus is difficult to diagnose, the worldwide prevalence of SLE can only be roughly estimated to range from 10 and 200 cases per 100,000 individuals with dramatic differences depending on gender, ethnicity, and location. Although the treatment of this disease has been significantly ameliorated by new therapies, improved conventional drug therapy options, and a trained expert eye, the underlying pathogenesis of lupus still remain widely unknown. The complex etiology reflects the complex genetic background of the disease, which is also not well understood yet. However, in the past few years advances in lupus genetics have been made, notably with the publication of genome-wide association studies (GWAS) in humans and the identification of susceptibility genes and loci in mice. This paper reviews the role of MHC-linked susceptibility genes in the pathogenesis of systemic lupus erythematosus.
PMCID: PMC3385965  PMID: 22761632
10.  Targeting transcription factor Stat4 uncovers a role for interleukin-18 in the pathogenesis of severe lupus nephritis in mice 
Kidney international  2010;79(4):452-463.
Polymorphisms in the transcription factor Stat4 gene have been implicated as risk factors for systemic lupus erythematosus. Although some polymorphisms have a strong association with autoantibodies and nephritis, their impact on pathophysiology is still unknown. To explore this further we used signal transducers and activators of transcription 4 (Stat4) knockout MRL/MpJ-Faslpr/Faslpr (MRL-Faslpr) mice and found that they did not differ in survival or renal function from Stat4-intact MRL-Faslpr mice. Circulating interleukin (IL)-18 levels, however, were elevated in Stat4-deficient compared to Stat4-intact mice, suggesting that this interleukin might contribute to the progression of lupus nephritis independent of Stat4. In a second approach, Stat4 antisense or missense oligonucleotides or vehicle were given to MRL-Faslpr mice with advanced nephritis. Each of these treatments temporarily ameliorated disease, although IL-18 was increased in each setting. Based on these findings, studies using gene transfer to overexpress IL-18 in MRL-Faslpr and IL-12p40/IL-23 knockout MRL-Faslpr mice reveal a critical role for IL-18 in mediating disease. Thus, the Stat4 and IL-12 (an activator of Stat4)-independent factor, IL-18, can drive autoimmune lupus nephritis in MRL-Faslpr mice. Temporarily blocking Stat4 during advanced nephritis ameliorates disease, suggesting a time-dependent compensatory proinflammatory mechanism.
PMCID: PMC3197226  PMID: 20980973
chronic glomerulonephritis; chronic inflammation; lupus nephritis
11.  Safety and clinical outcomes of rituximab therapy in patients with different autoimmune diseases: experience from a national registry (GRAID) 
Evidence from a number of open-label, uncontrolled studies has suggested that rituximab may benefit patients with autoimmune diseases who are refractory to standard-of-care. The objective of this study was to evaluate the safety and clinical outcomes of rituximab in several standard-of-care-refractory autoimmune diseases (within rheumatology, nephrology, dermatology and neurology) other than rheumatoid arthritis or non-Hodgkin's lymphoma in a real-life clinical setting.
Patients who received rituximab having shown an inadequate response to standard-of-care had their safety and clinical outcomes data retrospectively analysed as part of the German Registry of Autoimmune Diseases. The main outcome measures were safety and clinical response, as judged at the discretion of the investigators.
A total of 370 patients (299 patient-years) with various autoimmune diseases (23.0% with systemic lupus erythematosus, 15.7% antineutrophil cytoplasmic antibody-associated granulomatous vasculitides, 15.1% multiple sclerosis and 10.0% pemphigus) from 42 centres received a mean dose of 2,440 mg of rituximab over a median (range) of 194 (180 to 1,407) days. The overall rate of serious infections was 5.3 per 100 patient-years during rituximab therapy. Opportunistic infections were infrequent across the whole study population, and mostly occurred in patients with systemic lupus erythematosus. There were 11 deaths (3.0% of patients) after rituximab treatment (mean 11.6 months after first infusion, range 0.8 to 31.3 months), with most of the deaths caused by infections. Overall (n = 293), 13.3% of patients showed no response, 45.1% showed a partial response and 41.6% showed a complete response. Responses were also reflected by reduced use of glucocorticoids and various immunosuppressives during rituximab therapy and follow-up compared with before rituximab. Rituximab generally had a positive effect on patient well-being (physician's visual analogue scale; mean improvement from baseline of 12.1 mm).
Data from this registry indicate that rituximab is a commonly employed, well-tolerated therapy with potential beneficial effects in standard of care-refractory autoimmune diseases, and support the results from other open-label, uncontrolled studies.
PMCID: PMC3218885  PMID: 21569519
12.  CSF-1 signals directly to renal tubular epithelial cells to mediate repair in mice 
The Journal of Clinical Investigation  2009;119(8):2330-2342.
Tubular damage following ischemic renal injury is often reversible, and tubular epithelial cell (TEC) proliferation is a hallmark of tubular repair. Macrophages have been implicated in tissue repair, and CSF-1, the principal macrophage growth factor, is expressed by TECs. We therefore tested the hypothesis that CSF-1 is central to tubular repair using an acute renal injury and repair model, ischemia/reperfusion (I/R). Mice injected with CSF-1 following I/R exhibited hastened healing, as evidenced by decreased tubular pathology, reduced fibrosis, and improved renal function. Notably, CSF-1 treatment increased TEC proliferation and reduced TEC apoptosis. Moreover, administration of a CSF-1 receptor–specific (CSF-1R–specific) antibody after I/R increased tubular pathology and fibrosis, suppressed TEC proliferation, and heightened TEC apoptosis. To determine the contribution of macrophages to CSF-1–dependent renal repair, we assessed the effect of CSF-1 on I/R in mice in which CD11b+ cells were genetically ablated and determined that macrophages only partially accounted for CSF-1–dependent tubular repair. We found that TECs expressed the CSF-1R and that this receptor was upregulated and coexpressed with CSF-1 in TECs following renal injury in mice and humans. Furthermore, signaling via the CSF-1R stimulated proliferation and reduced apoptosis in human and mouse TECs. Taken together, these data suggest that CSF-1 mediates renal repair by both a macrophage-dependent mechanism and direct autocrine/paracrine action on TECs.
PMCID: PMC2719924  PMID: 19587445
13.  Proteinase-3 as the major autoantigen of c-ANCA is strongly expressed in lung tissue of patients with Wegener's granulomatosis 
Arthritis Research  2002;4(3):220-225.
Proteinase-3 (PR-3) is a neutral serine proteinase present in azurophil granules of human polymorphonuclear leukocytes and serves as the major target antigen of antineutrophil cytoplasmic antibodies with a cytoplasmic staining pattern (c-ANCA) in Wegener's granulomatosis (WG). The WG disease appears as severe vasculitis in different organs (e.g. kidney, nose and lung). Little is known about the expression and distribution of PR-3 in the lung. We found that PR-3 is expressed in normal lung tissue and is upregulated in lung tissue of patients with WG. Interestingly, the parenchymal cells (pneumocytes type I and II) and macrophages, and not the neutrophils, express PR-3 most strongly and may contribute to lung damage in patients with WG via direct interaction with antineutrophil cytoplasmic antobodies (ANCA). These findings suggest that the PR-3 expression in parenchymal cells of lung tissue could be at least one missing link in the etiopathogenesis of pulmonary pathology in ANCA-associated disease.
PMCID: PMC111026  PMID: 12010574
granuloma; in situ hybridization; pneumocytes; proteinase-3; Wegener's granulomatosis
14.  Monocyte Chemoattractant Protein 1–Dependent Leukocytic Infiltrates Are Responsible for Autoimmune Disease in Mrl-Faslpr Mice 
The Journal of Experimental Medicine  1999;190(12):1813-1824.
Infiltrating leukocytes may be responsible for autoimmune disease. We hypothesized that the chemokine monocyte chemoattractant protein (MCP)-1 recruits macrophages and T cells into tissues that, in turn, are required for autoimmune disease. Using the MRL-Faslpr strain with spontaneous, fatal autoimmune disease, we constructed MCP-1–deficient MRL-Faslpr mice. In MCP-1–intact MRL-Faslprmice, macrophages and T cells accumulate at sites (kidney tubules, glomeruli, pulmonary bronchioli, lymph nodes) in proportion to MCP-1 expression. Deleting MCP-1 dramatically reduces macrophage and T cell recruitment but not proliferation, protects from kidney, lung, skin, and lymph node pathology, reduces proteinuria, and prolongs survival. Notably, serum immunoglobulin (Ig) isotypes and kidney Ig/C3 deposits are not diminished in MCP-1–deficient MRL-Faslpr mice, highlighting the requirement for MCP-1–dependent leukocyte recruitment to initiate autoimmune disease. However, MCP-1–deficient mice are not completely protected from leukocytic invasion. T cells surrounding vessels with meager MCP-1 expression remain. In addition, downstream effector cytokines/chemokines are decreased in MCP-1–deficient mice, perhaps reflecting a reduction of cytokine-expressing leukocytes. Thus, MCP-1 promotes MRL-Faslpr autoimmune disease through macrophage and T cell recruitment, amplified by increasing local cytokines/chemokines. We suggest that MCP-1 is a principal therapeutic target with which to combat autoimmune diseases.
PMCID: PMC2195716  PMID: 10601356
mouse; kidney; lung; chemokine; gene disruption
15.  Monocyte chemoattractant protein-1 promotes macrophage-mediated tubular injury, but not glomerular injury, in nephrotoxic serum nephritis 
Monocyte chemoattractant protein-1 (MCP-1) is upregulated in renal parenchymal cells during kidney disease. To investigate whether MCP-1 promotes tubular and/or glomerular injury, we induced nephrotoxic serum nephritis (NSN) in MCP-1 genetically deficient mice. Mice were analyzed when tubules and glomeruli were severely damaged in the MCP-1–intact strain (day 7). MCP-1 transcripts increased fivefold in MCP-1–intact mice. MCP-1 was predominantly localized within cortical tubules (90%), and most cortical tubules were damaged, whereas few glomerular cells expressed MCP-1 (10%). By comparison, there was a marked reduction (>40%) in tubular injury in MCP-1–deficient mice (histopathology, apoptosis). MCP-1–deficient mice were not protected from glomerular injury (histopathology, proteinuria, macrophage influx). Macrophage accumulation increased adjacent to tubules in MCP-1–intact mice compared with MCP-1–deficient mice (70%, P < 0.005), indicating that macrophages recruited by MCP-1 induce tubular epithelial cell (TEC) damage. Lipopolysaccharide-activated bone marrow macrophages released molecules that induced TEC death that was not dependent on MCP-1 expression by macrophages or TEC. In conclusion, MCP-1 is predominantly expressed by TEC and not glomeruli, promotes TEC and not glomerular damage, and increases activated macrophages adjacent to TEC that damage TEC during NSN. Therefore, we suggest that blockage of TEC MCP-1 expression is a therapeutic strategy for some forms of kidney disease.
PMCID: PMC407867  PMID: 9884336
16.  New perspectives on the renal slit diaphragm protein podocin 
Modern Pathology  2011;24(8):1101-1110.
Podocin is a critical component of the glomerular filtration barrier, its mutations causing recessive steroid-resistant nephrotic syndrome. A GenBank analysis of the human podocin (NPHS2) gene resulted in the possible existence of a new splice variant of podocin in the kidney, missing the in-frame of exon 5, encoding the prohibitin homology domain. Using RT–polymerase chain reaction and immunoblotting followed by sequence analysis, we are for the first time able to prove the expression of a novel podocin isoform (isoform 2), exclusively and constitutively expressed in human podocytes. Furthermore, we reveal singular extrarenal podocin expression in human and murine testis. Our data show the Sertoli cells of the seminiferous tubules to be the origin of testicular podocin. Confocal laser microscopy illustrates the co-localization of podocin with filamentous actin within Sertoli cells, suggesting a role of podocin in the blood/testis barrier. These results led to the rationale to examine podocin expression in testes of men with Sertoli cell-only syndrome, a disorder characterized by azoospermia. Interestingly, we observed a complete down-regulation of podocin mRNA in Sertoli cell-only syndrome, indicating a possible role of podocin in the pathogenesis of this germinal aplasia. Men with Sertoli cell-only syndrome show normal renal podocin expression, suggesting an alternate regulation of the testicular promoter. Our findings may change the perception of podocin and give new insights into the ultrastructure of glomerular slit diaphragm and the blood/testis barrier.
PMCID: PMC3182839  PMID: 21499232
isoform; kidney; podocin; Sertoli cell-only syndrome; Sertoli cells; testis; WT-1

Results 1-16 (16)