Transdifferentiation of Distal but Not Proximal Tubular Epithelial Cells from Human Kidney in Culture

Abstract

Human renal proximal and distal (thick ascending limb and early distal convoluted tubule) epithelial cells have been isolated according to their specific antigen expression. The cells were well characterized by flow cytometry, enzyme cytochemistry and electron microscopy and cultured for up to 3 months. Cultured tubular cells coexpressed cytokeratin and vimentin as intermediate filament proteins. While primary isolated cells, proximal as well as distal, revealed the phenotypic characteristics of their nephron origin, cultured distal cells showed the tendency to dedifferentiate/transdifferentiate. Distal cells lost their characteristic expression of Tamm-Horsfall glycoprotein and started de novo expression of the proximal marker proteins aminopeptidase M, γ-glutamyl transferase and dipeptidyl peptidase IV. The expression of these antigens by distal cells could be shown by flow-cytometric analysis and fluorescence microscopy. Enzyme activity assays revealed the activity of aminopeptidase M, γ-glutamyl transferase and dipeptidyl peptidase IV, but not of the proximal marker enzyme alkaline phosphatase. This antigenic shift could not be prevented in different culture media, and the original phenotype could not be restored. Cultured cells displayed characteristic hormonal stimulation patterns indicative of their proximal and distal origins, as shown by activation of adenylate cyclase by different peptide hormones. These results indicate that distal tubular cells possibly transdifferentiate to a more proximal phenotype in view of loss of the distal marker enzyme Tamm-Horsfall protein and de novo expression of proximal marker enzymes like dipeptidyl peptidase IV and aminopeptidase M.

Differentiation Status of Human Renal Proximal and Distal Tubular Epithelial Cells in vitro<i>: </i>Differential Expression of Characteristic Markers

“…On the other hand, cultured DTC are differentiated with respect to their E-cadherin expression and their morphology. Nevertheless, they differ from those in situ by their de novo expression of CD13 and CD26 and their failure to express THG in culture [Baer et al, 1999]. We were able to demonstrate that THG was present in the supernatant of primary DTC cultures, but not in the supernatant of PTC or in higher passages of both (THG-ELISA, unpubl.…”

“…Cytokeratin expression is a feature of terminally differentiated epithelial cells. Earlier observations, which show the coexpression of vimentin and cytokeratin, emphasize the more 'embryonic' character of cultured tubular cells [Baer et al, 1999]. Vimentin is expressed in regenerating tubules after renal failure or the metanephric mesenchyme in tubulogenesis [Bonventre, 2003].…”

Different Effects of Growth Factors on Human Renal Early Distal Tubular Cells in vitro

“…data]. Nevertheless, cultured TALDC do not express THG, a characteristic marker of the TALH and the early distal tubule [17] .…”

Glucose Transporters in Human Renal Proximal Tubular Cells Isolated From the Urine of Patients With Non–Insulin-Dependent Diabetes

“…The cultured HEPTECs showed similar characteristics to the renal proximal tubular grown from human biopsies as well as the proximal tubular markers such as the CD13, alkaline phosphatase, and SGLT2 (19 -20). Although, distal tubular cells are known to transdifferentiate to a more proximal phenotype (32), HEPTECs showed stable levels of expression of proximal tubular markers from the time of their first passage (Figs. 2-4).…”