Crosstalk between oxygen signaling and iron metabolism in renal interstitial fibroblasts.

To maintain the oxygen supply, the production of red blood cells (erythrocytes) is promoted under low-oxygen conditions (hypoxia). Oxygen is carried by hemoglobin in erythrocytes, in which the majority of the essential element iron in the body is contained. Because iron metabolism is strictly controlled in a semi-closed recycling system to protect cells from oxidative stress caused by iron, hypoxia-inducible erythropoiesis is closely coordinated by regulatory systems that mobilize stored iron for hemoglobin synthesis. The erythroid growth factor erythropoietin (EPO) is mainly secreted by interstitial fibroblasts in the renal cortex, which are known as renal EPO-producing (REP) cells, and promotes erythropoiesis and iron mobilization. Intriguingly, EPO production is strongly induced by hypoxia through iron-dependent pathways in REP cells. Here, we summarize recent studies on the network mechanisms linking hypoxia-inducible EPO production, erythropoiesis and iron metabolism. Additionally, we introduce disease mechanisms related to disorders in the network mediated by REP cell functions. Furthermore, we propose future studies regarding the application of renal cells derived from the urine of kidney disease patients to investigate the molecular pathology of chronic kidney disease and develop precise and personalized medicine for kidney disease.

Cerebellar haemorrhage triggered by allergic reaction to maintenance haemodialysis in a patient with eosinophilia.

We report a case of eosinophilia and an allergic reaction that caused a cerebellar haemorrhage.An woman in her 80s presented with headache, dyspnoea and vomiting with severe hypotension soon after switching the dialysis membrane, and a CT scan revealed cerebellar haemorrhage. In the subsequent clinical course, the patient developed an allergic reaction to multiple membranes and required corticosteroids to continue haemodialysis (HD). Pre-existing eosinophilia is a risk factor for cerebral infarctions and dialysis membrane allergy, which is a common feature in patients undergoing HD. Membrane switching and corticosteroid therapy must be considered in case of multiple membrane allergies.

First case report of monoclonal IgG3-heavy-chain glomerulonephritis with microtubular structures.

Our patient was a 69-year-old woman admitted to our hospital for heavy proteinuria and hematuria. A renal biopsy showed findings similar to those of membranoproliferative glomerulonephritis associated with nodular lesions, and immunofluorescence showed marked deposits of IgG, C1q, and C3 on the peripheral capillary walls. IgG3 alone was observed on IgG subclass staining with no κ or λ light chains, and Congo red staining was negative. These findings suggested IgG3-heavy-chain deposition disease (HCDD). However, we did not find a deletion of the first heavy-chain constant domain, which is commonly observed in HCDD. Electron microscopy showed randomly arranged subendothelial microtubular structures with diameters of 70-90 nm. Altogether, the diagnosis of HCDD could not be made, although monoclonal IgG3 deposits in glomeruli were observed. This is the first case report of monoclonal IgG3-heavy-chain glomerulonephritis with subendothelial-based, randomly arranged microtubular structures with diameters of 70-90 nm.