Shokichi Naito

Intestinal barrier dysfunction and mucus layer abnormalities are central features of inflammatory bowel disease, yet the epithelial mechanisms regulating goblet cell function remain incompletely understood. The TWEAK/Fn14 pathway is involved in intestinal inflammation, but its role in small intestinal epithelial responses, particularly in goblet cells, has not been fully clarified. In this study, we investigated TWEAK/Fn14 signaling using mouse small intestinal epithelial organoids. Fn14 was expressed in MUC2-positive cells in intestinal tissue, with staining preferentially observed toward the mucin-facing region. Fn14 staining was also observed in small intestinal epithelial organoids. TWEAK stimulation increased Tnf mRNA expression by approximately 1.56-fold and reduced Muc2 mRNA expression to approximately 66% of control, without markedly affecting epithelial proliferation or stem cell markers. TWEAK did not significantly alter the PAS-positive mucin area or AB-PAS-defined mucin composition, whereas PGM34 staining showed a non-significant tendency to increase. TNF treatment reproduced some of the TWEAK-associated changes, including reduced Muc2 mRNA expression and alterations in mucin-associated parameters, suggesting that TNF may contribute to some of the epithelial responses associated with TWEAK treatment. Treatment with an anti-TNF neutralizing antibody modified several TWEAK-associated responses, including changes in epithelial-associated gene expression and mucin-associated staining parameters. These findings suggest that TWEAK treatment is associated with goblet cell-related mucin responses in mouse small intestinal epithelial organoids, with possible involvement of TNF signaling.

Familial lecithin-cholesterol acyltransferase deficiency (FLD) is a rare hereditary disorder. In FLD, a clinical triad of corneal opacity, anemia, and proteinuria typically precedes progressive renal dysfunction. Although early renal involvement has been widely described, there are limited reports on the long-term course leading to dialysis initiation, including systemic complications. We present a genetically confirmed case of FLD caused by the Cys74Tyr mutation, which had a clinical course exceeding 10 years with the emergence of multisystem complications. The patient initially showed a transient stabilization of renal function following a fat-restricted and protein-restricted diet and renin-angiotensin system blockade; however, subsequent decline occurred despite continued management. During this deterioration phase, systemic complications emerged, including progressive aortic valve stenosis, complete atrioventricular block, heart failure, and cerebellar infarction, in close temporal association with worsening renal function. Hemodialysis initiation led to rapid resolution of erythropoietin-resistant anemia, which may be attributable to the improvement in the uremic milieu following dialysis initiation. This case offers valuable insights into the late-stage progression of FLD. The observations may help determine the point at which renoprotective and metabolic interventions become less effective. Furthermore, the temporal association between renal deterioration and the development of cardiovascular and neurovascular complications suggests the need for careful clinical surveillance during advanced stages of renal dysfunction.

Immunoglobulin A nephropathy (IgA-N) is a primary glomerulonephritis that is characterized by mesangial cell proliferation and expansion. Although glomerular endothelial cells (GE) are implicated in the pathogenesis of IgA-N, their role remains poorly understood. We conduct single-cell and spatial transcriptomic analysis using human specimens with mild IgA-N compared with normal. We integrate single-cell and spatial transcriptome analyses in human samples of mild IgA-N compared to normal samples, revealing several novel findings: (1) identification of clusters of GE and their expressed gene profiles, (2) identification of novel inflammation-related molecules newly implicated in GE in mild IgA-N, (3) activation of inflammatory pathways characteristic of IgA-N. Therefore, we suggest the importance of GE in the mechanism of IgA-N, as GE initiates more active inflammatory response prior to mesangial cells in patients with mild IgA-N. These findings provide useful information for understanding the pathogenesis and choosing the best drug for IgA nephropathy.

Immunoglobulin A nephropathy (IgA-N) is a primary glomerulonephritis characterized by mesangial cell proliferation and expansion. It still leads to end-stage renal disease over the long course of the disease in many patients. Although glomerular endothelial cells (GE) have been implicated in the pathogenesis of IgA-N, their role remains poorly understood. We conducted single-cell and spatial transcriptomic analysis using human specimens with mild IgA-N compared with normal. We observed the significantly higher expression of several inflammation-associated molecules which have been reported and not reported to be involved in IgA-N pathogenesis, respectively. Furthermore, we show that several important molecules were also highly expressed in GE of IgA-N at protein level by tissue immunostaining. Our analysis suggests that the characteristic pathways identified in GE that involve these molecules are associated with the progression of IgA-N. These findings offer important insights on both the pathogenesis of IgA-N and its treatment at an early stage.

We recently found that albuminuria levels in patients with minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS) inversely correlate with glycosphingolipid GM3 expression levels in glomerular podocytes. Moreover, we showed enhanced expression of GM3 via activation of the GM3 synthase gene upon administration of valproic acid (VPA) is effective in suppressing albuminuria and podocyte injury in mice with anti-nephrin antibody-induced podocytopathy. However, the therapeutic effect of GM3 on diabetic nephropathy, which is the most common underlying disease in patients undergoing dialysis and with podocyte injury, remains unclear. Here, we investigated the therapeutic effect of enhanced GM3 expression via VPA on podocyte injury using streptozotocin-induced diabetic nephropathy model mice. Administration of VPA clearly decreased levels of albuminuria and glomerular lesions and inhibited the loss of podocytes and expansion in the mesangial area. Furthermore, we found that albuminuria levels in patients with diabetic nephropathy inversely correlate with the expression of GM3 in podocytes. These results indicate that maintaining GM3 expression in podocytes by administration of VPA may be effective in treating not only podocyte injury, such as MCD and FSGS, but also the late stage of diabetic nephropathy.

Background Glycolipids on cell membrane rafts play various roles by interacting with glycoproteins. Recently, it was reported that the glycolipid GM3 is expressed in podocytes and may play a role in podocyte protection. In this report, we describe the correlation between changes in GM3 expression in glomeruli and proteinuria in minimal change nephrotic syndrome (MCNS) and focal segmental glomerulosclerosis (FSGS) patients. Methods We performed a case–control study of the correlation between nephrin/GM3 expression levels and proteinuria in MCNS and FSGS patients who underwent renal biopsy at our institution between 2009 and 2014. Normal renal tissue sites were used from patients who had undergone nephrectomy at our institution and gave informed consent. Results Both MCNS and FSGS had decreased GM3 and Nephrin expression compared with the normal (normal vs. MCNS, FSGS; all p < 0.01). Furthermore, in both MCNS and FSGS, GM3 expression was negatively correlated with proteinuria (MCNS: r = − 0.61, p < 0.01, FSGS: r = − 0.56, p < 0.05). However, nephrin expression had a trend to correlate with proteinuria in FSGS (MCNS: r = 0.19, p = 0.58, FSGS: r = − 0.48, p = 0.06). Furthermore, in a simple linear regression analysis, GM3 expression also correlated with proteinuric change after 12 months of treatment (MCNS: r = 0.40, p = 0.38, FSGS: r = 0. 68, p < 0.05). Conclusion We showed for the first time that decreased GM3 expression correlates with proteinuria in MCNS and FSGS patients. Further studies are needed on the podocyte-protective effects of GM3.

Studies have shown in several diseases initially affecting podocytes, that the neighboring glomerular parietal epithelial cells (PECs) are secondarily involved. The PEC response might be reparative under certain circumstances, yet injurious under others. The factors governing these are not well understood. We have shown that SM22α, an actin-binding protein considered a marker of smooth muscle differentiation, is upregulated in podocytes and PECs in several models of podocyte disease. However, the impact of SM22α levels on PECs is not known. Experimental glomerular disease, characterized by primary podocyte injury, was induced in aged-matched SM22α +/+ and SM22α -/- mice by intraperitoneal injection of sheep anti-rabbit glomeruli antibody. Immunostaining methods were employed on days 7 and 14 of disease. The number of PEC transition cells, defined as cells co-expressing a PEC protein (PAX2) and podocyte protein (Synaptopodin) was higher in diseased SM22α -/- mice compared with SM22α +/+ mice. WT1 staining along Bowman’s capsule is higher in diseased SM22α -/- mice. This was accompanied by increased PEC proliferation (measured by ki-67 staining), and an increase in immunostaining for the progenitor marker NCAM, in a subpopulation of PECs in diseased SM22α -/- mice. In addition, immunostaining for vimentin and alpha smooth muscle actin, markers of epithelial-to-mesenchymal transition (EMT), was lower in diseased SM22α -/- mice compared to diseased SM22α+/+ mice. SM22α levels may impact how PECs respond following a primary podocyte injury in experimental glomerular disease. Absent/lower levels favor an increase in PEC transition cells and PECs expressing a progenitor marker, and a lower EMT rate compared to SM22α +/+ mice, where SM22 levels are markedly increased in PECs.