Glomerular Endothelial Cell-Derived microRNA-192 Regulates Nephronectin Expression in Idiopathic Membranous Glomerulonephritis

BackgroundAutoantibodies binding to podocyte antigens cause idiopathic membranous glomerulonephritis (iMGN). However, it remains elusive how autoantibodies reach the subepithelial space because the glomerular filtration barrier (GFB) is size selective and almost impermeable for antibodies.MethodsKidney biopsies from patients with iMGN, cell culture, zebrafish, and mouse models were used to investigate the role of nephronectin (NPNT) regulating microRNAs (miRs) for the GFB.ResultsGlomerular endothelial cell (GEC)-derived miR-192-5p and podocyte-derived miR-378a-3p are upregulated in urine and glomeruli of patients with iMGN, whereas glomerular NPNT is reduced. Overexpression of miR-192-5p and morpholino-mediated npnt knockdown induced edema, proteinuria, and podocyte effacement similar to podocyte-derived miR-378a-3p in zebrafish. Structural changes of the glomerular basement membrane (GBM) with increased lucidity, splitting, and lamellation, especially of the lamina rara interna, similar to ultrastructural findings seen in advanced stages of iMGN, were found. IgG-size nanoparticles accumulated in lucidity areas of the lamina rara interna and lamina densa of the GBM in npnt-knockdown zebrafish models. Loss of slit diaphragm proteins and severe structural impairment of the GBM were further confirmed in podocyte-specific Npnt knockout mice. GECs downregulate podocyte NPNT by transfer of miR-192-5p–containing exosomes in a paracrine manner.ConclusionsPodocyte NPNT is important for proper glomerular filter function and GBM structure and is regulated by GEC-derived miR-192-5p and podocyte-derived miR-378a-3p. We hypothesize that loss of NPNT in the GBM is an important part of the initial pathophysiology of iMGN and enables autoantigenicity of podocyte antigens and subepithelial immune complex deposition in iMGN.

FC 030CONTACTIN-1 IS A NOVEL ANTIGEN IN IDIOPATHIC MEMBRANOUS GLOMERULONEPHRITIS AND IN CIDP- ASSOCIATED GLOMERULONEPHRITIS

Background and Aims Recently a number of antigens have been identified as pathogenic antibody targets in cases of primary membranous glomerulonephritis(MGN), including phospholipase A2 receptor (PLA2R), thrombospondin type 1 domain containing 7A(THSD7A), and NELL-1, while exostosin is found in secondary (lupus associated) MGN. However, other as yet undiscovered antigens are thought to exist. Although rare, there is a recognised association between chronic inflammatory demyelinating polyneuriopathy (CIDP) and nephrotic syndrome. Method We investigated the link between CICP and MGN and the associations with Contactin-1(CNTN1), a node of Ranvier neuronal protein, as a potential common autoantigen, by immunohistochemistry, RT-PCR and proteomic analysis of isolated glomeruli. We tested sera from 468 patients with suspected immune-mediated neuropathies, 295 with idiopathic MGN, and 210 disease controls, for CNTN1 antibodies. Results We describe a series of 16 patients, all presenting with CIDP, nephrotic syndrome due to MGN, and with circulating and deposited anti-contactin-1 (CNTN1) antibodies (IgG4 predominant in those tested) in the kidney. The onset and resolution of both disorders had a close temporal relationship, and the majority of cases were resistant to first-line therapies typically employed for inflammatory neuropathies, but achieved a good outcome with non-standard treatment. Importantly, four (1.4%) further patients with isolated MGN identified from a serum bank of 295 idiopathic MGN patients with no CIDP were also positive for anti-CNTN1 antibodies. CNTN1 protein was detected by mass spectroscopy within glomeruli from patients with CNTN1 antibodies, but not in healthy kidney or anti-PLA2R associated MGN. CNTN1 mRNA was found in renal cortical tissue. Conclusion These data provide evidence that CNTN1 antibodies precipitate both autoimmune neuropathy and MGN. The temporal correlation of these disorders, as well as the presence of CNTN1 protein and antibodies in both peripheral nerve and diseased glomeruli, supports a common antibody-mediated pathological process, and defines a new antigenic target in MGN. CNTN1 antibodies have diagnostic and therapeutic relevance, and may additionally serve as a means of monitoring disease activity in both conditions. Other factors may explain presentation with isolated neurological disease or MGN.

Spinal cord infarction associated to retinal vein occlusion in a patient with chronic kidney disease

A 70-year-old man presented to the emergency department with blood hypotension associated to a sudden paraplegia and thermalgesic analgesia. He had an history of colic and prostatic adenocarcinoma, hypertension and non-dialyzed Chronic Kidney Disease (CKD) related to an idiopathic membranous glomerulonephritis type 1 discovered 9 years ago. Magnetic resonance imaging confirmed a diagnosis of Spinal Cord Infarction (SCI). Few months later, he presented a blurred vision due to central Retinal Vein Occlusion (RVO), which was improved by Anti-VEGF therapy. This is the first reported case of a concomitance of retinal vascular event and SCI highlights the links between the central nervous system and retinal vascularization despite separate involvement of the two events in the arterial and venous systems. Additionally, CKD worsened the risk of cardiovascular incidents by induced oxidative stress, thrombophilia, chronic inflammation, and endothelial dysfunction. SCI occurrence indicates severe vascular dysfunction and elevates the risk of additional vascular disorders.

Case study of tacrolimus as an effective treatment for idiopathic membranous glomerulonephritis in pregnancy

Background Tacrolimus has been used in pregnant women following transplantation and for management of lupus nephritis. We report a case of successful control of nephrotic syndrome due to membranous glomerulonephritis during pregnancy using tacrolimus. Case report A 26-year-old female presented with severe nephrotic syndrome in her first pregnancy. Post-partum renal biopsy confirmed idiopathic membranous glomerulonephritis. She had persistent proteinuria of 6 g/day with hypoalbuminaemia despite angiotensin receptor blockade. Treatment with tacrolimus monotherapy led to remission of proteinuria, three months prior to conceiving again. She maintained remission with tacrolimus therapy in pregnancy, resulting in a successful birth outcome. Conclusions Membranous glomerulonephritis can be successfully and safely managed with tacrolimus monotherapy during pregnancy. This provides an alternative immunosuppressant with a favourable side effect profile suitable for use in women planning a pregnancy when other immunosuppressive drugs should be avoided.

Phospholipase A2 Receptor-Positive Idiopathic Membranous Glomerulonephritis with Onset at 95 Years: Case Report

A 95-year-old woman was admitted to our hospital for evaluation of bilateral lower-limb edema persisting for 3 months. Serum creatinine was 1.55 mg/dl, and urinary protein excretion was 9.1 g/day. Renal biopsy revealed stage 1 membranous glomerulonephritis (MGN) with immunoglobulin G4-dominant staining. This patient did not have any underlying disease such as infection with hepatitis B or C virus or malignancy, and anti-phospholipase A2 receptor (PLA2R) antibody was detected in the serum. Accordingly, idiopathic MGN was diagnosed. Corticosteroid therapy was avoided, but hemodialysis was required to treat generalized edema. The patient is currently doing well. This is the oldest reported case of idiopathic MGN with positivity for anti-PLA2R antibody.