Morphologic evaluation and integrin expression profile of renal tubular cells cultured from percutaneous renal biopsy specimen

Functional characterization of apical transporters expressed in rat proximal tubular cells (PTCs) in primary culture

Since in vitro cell culture models often show altered apical transporter expression, they are not necessarily suitable for the analysis of renal transport processes. Therefore, we aimed here to investigate the usefulness of primary-cultured rat proximal tubular cells (PTCs) for this purpose. After isolation of renal cortical cells from rat kidneys, PTCs were enriched and the gene expression and function of apical transporters were analyzed by means of microarray, RT-PCR and uptake experiments. RT-PCR confirmed that the major apical transporters were expressed in rat PTCs. Na(+)-dependent uptake of α-methyl-d-glucopyranoside (αMG), ergothioneine and carnitine by the PTCs suggests functional expression of Sglts, Octn1 and Octn2, respectively. Inhibition of pH-dependent glycylsarcosine uptake by low concentration of cephalexin, which is a β-lactam antibiotics recognized by Pepts, indicates a predominant role of high affinity type Pept2, but not low affinity type Pept1, in the PTCs. Moreover, the permeability ratio of [(14)C]αMG (apical to basolateral/basolateral to apical) across PTCs was 4.3, suggesting that Sglt-mediated reabsorptive transport is characterized. In conclusion, our results indicate that rat PTCs in primary culture are found to be a promising in vitro model to evaluate reabsorption processes mediated at least by Sglts, Pept2, Octn1 and Octn2.

Cytokine expression in the renal tubular epithelial cells stimulated by Shiga toxin 2 of Escherichia coli O157:H7

Hemolytic uremic syndrome (HUS) is the most common cause of acute renal failure in children worldwide. Shiga toxin (Stx) associated HUS, the most common type, is now known to be caused by Escherichia coli O157:7, which produces Stxl or the more potent, Stx2. Since the renal tubule is the major tissue affected in the course of HUS and Stx2 is known to be toxic to the renal tubular cells (RTC), we attempted to elucidate the mechanism of renal injury in HUS by studying the alteration of cytokines in the RTC evoked by Stx2. cDNA-array is a powerful tool for evaluating changes in the expression of a group of critical genes and also gives insights on the overview of the gene activation. In this study, we purified Stx2 from the E. coli O157:7, which was isolated from a typical diarrhea-associated HUS patient and then tried to compare the cytokine gene expression between the stimulated RTC and un-stimulated RTC using cDNA-array. Our results showed that one third of the examined cytokine genes were up regulated at least twice by the addition of Vtx2. These up-regulated genes represented the chemokines (macrophage related cytokines), fibrosis-related cytokine (TNF, PDGF) and leukemia inhibitory factors. However, the expression of IL-6, one of the pleiotropic cytokines, was significantly decreased and this finding was confirmed by northern analysis. Our results suggest that VT2 up-regulates the pro-inflammatory cytokines and fibrosis prone growth factors in RTC and that the inhibition of the activation of these cytokines may ameliorate the renal tubular injury in the HUS caused by E. coli O157:7.