Glucose-induced gradual phenotypic modulation of cultured human glomerular epithelial cells may be independent of Wilms’ tumor 1 (WT1)

Abstract

BackgroundRenal podocytes form the main filtration barrier possessing a unique phenotype maintained by proteins including podocalyxin and nephrin, the expression of which is suppressed in pathological conditions. We used an in vitro model of human glomerular epithelial cells (HGEC) to investigate the role of high glucose in dysregulating the podocytic epithelial phenotype and determined the time needed for this change to occur.ResultsIn our in vitro podocyte system changes indicating podocyte dedifferentiation in the prolonged presence of high glucose included loss of podocalyxin, nephrin and CD10/CALLA concomitant with upregulation of mesenchymal vimentin. Our study demonstrates for the first time that podocyte-specific markers undergo changes of expression at different time intervals, since glucose-mediated podocalyxin downregulation is a progressive process that precedes downregulation of nephrin expression. Finally we demonstrate that high glucose permanently impaired WT1 binding to the podocalyxin gene promoter region but did not affect WT1 binding on the nephrin gene promoter region.ConclusionThe presence of high glucose induced a phenotypic conversion of podocytes resembling partial dedifferentiation. Our study demonstrates that dysregulation of the normal podocytic phenotype is an event differentially affecting the expression of function-specific podocytic markers, exhibiting downregulation of the epithelial marker CD10/CALLA and PC first, followed by stably downregulated nephrin. Furthermore, it is herein suggested that WT1 may not be directly involved with upregulation of previously reduced PC and nephrin expression.

Vitamin D3 ameliorates podocyte injury through the nephrin signalling pathway

“…Chronic hyperglycaemia disrupts signal transduction pathways involved in glomerular survival [36]. Our previous work [37], as well as work by others [38] demonstrated a decrease of glomerular nephrin expression as an early event in hyperglycaemic conditions. We demonstrated herein that short-term exposure of isolated glomeruli to high glucose affected nephrin expression and impaired phosphorylation and Akt activation.…”

High Glucose Impairs Insulin Signaling in the Glomerulus: An In Vitro and Ex Vivo Approach

“…Hyperglycaemia is a major determinant for the development of diabetic microvascular disease [ 38 ] and patients with diabetes experience increased glucose uptake by the kidney [ 39 ]. Previous work of our lab has shown that HG induced partial de-differentiation of podocytes [ 40 ] and apparently impaired foot processes by severe downregulation of podocalyxin [ 41 ]. We presently provided evidence that the presence of HG suffices to downregulate insulin signaling in vitro in human podocytes, as well as ex vivo , in isolated rat glomeruli.…”

Emerging Role of Podocalyxin in the Progression of Mature B-Cell Non-Hodgkin Lymphoma

“…PODXL has been reported to upregulate and form a complex with the glucose-transporter 3 (GLUT3) in embryonal carcinoma cancer stem cells [134]. On the other hand, glucose has been found to modulate PODXL expression in both normal and malignant cells [27,135,136]. In HGEC human glomerular epithelial cells, the presence of high-glucose levels downregulated PODXL expression [135,136], which reverted to normal values after cell exposure to low-glucose conditions [136].…”

“…On the other hand, glucose has been found to modulate PODXL expression in both normal and malignant cells [27,135,136]. In HGEC human glomerular epithelial cells, the presence of high-glucose levels downregulated PODXL expression [135,136], which reverted to normal values after cell exposure to low-glucose conditions [136]. Accordingly, we observed that Raji Burkitt lymphoma cells cultured in low-glucose conditions (0.5 mM) expressed increased surface levels of PODXL compared to those grown in high-glucose conditions (11 mM) [27].…”