We recently reported that fibronectin (FN: 230 kDa) was oversecreted from the renal tubular cells as a result of the stimulation of COM crystals, and inhibited the adhesion of COM crystals to renal tubular cells. In the study presented here, we investigated whether FN can prevent injury to renal tubular cells caused by oxalate and COM crystals and tried to identify the relation with inhibition of crystal adhesion. The protective effect of FN against renal tubular cell injury by exposure to oxalate and COM crystals was examined by measuring the lactate dehydrogenase (LDH) activity and using a non-radioactive proliferation assay. Moreover, crystal-cell interaction was morphologically assessed by means of scanning electron microscopy (SEM). LDH was reduced significantly by the addition of FN in a dose-dependent manner. Cell viability increased significantly with the addition of FN, also in a dose-dependent manner. Moreover, the morphological SEM study showed that few crystals were attached to the surface of cells when FN was added compared to the number of adhering crystals when FN was not added. FN was found to have an inhibitory effect on renal tubular cell injury caused by exposure to oxalate and COM crystals. We speculate that the inhibitory effect of FN on the adhesion of COM crystals is related to the inhibitory effect of exposure to COM crystals on renal tubular cell injury.
Background : Fibronectin (FN; 230 kDa) is a multifunctional α 2-glycoprotein distributed throughout the extracellular matrix and body fluids. We recently reported that FN has a protective effect against injury of renal tubular cells by exposure to oxalate and calcium oxalate (CaOX) crystals and inhibits the adhesion of CaOX crystals to renal tubular cells. In the study presented here, we investigated whether FN has inhibitory effect on crystal endocytosis by renal tubular cells. Methods : The inhibitory effect of FN on endocytosis of CaOX crystals by MDCK cells was examined by using a radioactivity uptake assay. Also, crystal endocytosis by cells was morphologically assessed by means of transmission electron microscopy (TEM). Results : FN had inhibitory effects on CaOX crystal endocytosis by MDCK cells. The morphological TEM study showed that few crystals were taken into cells when FN was added compared to the number of crystals when FN was not added. Conclusion : We found that FN had the inhibitory effects on the interaction between crystals and renal tubular cells, including the adhesion or endocytosis of crystals by cells.
Aim:To determine whether urinary macromolecules (UMM), which are the high molecular weight substances in urine, can provide protection against the oxalate-associated injury to the renal tubular cells. Methods: UMM were extracted from 24-h urine of 12 healthy adult male volunteers and 13 recurrent-stone-former male patients. Urine parameters in relation to urolithiasis were measured, including the level of glycosaminoglycans (GAG) in the UMM. MadinDarby canine kidney (MDCK) cells were used to evaluate the protective activity of UMM from oxalate-induced cytotoxicity by LDH release measurement and methyl-thiazolyl tertrazolium (MTT) assay. Results: Considering urinary parameters, citrate was significantly higher in urine from normal subjects than stone-former subjects; the other parameters show no differences between the groups. Total UMM and the level of GAG in the UMM were also significantly higher in the normal subject group. Compared with normal subject and stone-former subject UMM, after cells were treated with the UMM and then exposed to oxalate solution, LDH release was significantly higher in stone-former group. In the MTT assay, we found that more viable cells were observed after treatment with UMM compared to control in both groups. Moreover, UMM from the normal subjects showed higher protective activity against oxalate-related cytotoxicity than UMM from the stone-former subjects. Conclusion: UMM protected renal epithelial cells from oxalate-related injury. This protective activity was found to be higher in normal subject UMM than stone-former UMM. Among other factors, a higher concentration of GAG and citrate in normal subject UMM might affect some parts in this finding.
Introduction: Attachment of newly formed crystals to renal epithelial cells is considered to be a critical step in stone formation. Previously, we reported that exogenous fibronectin (FN; 220–240 kDa) had an inhibitory effect against renal tubular cell injury in Madin-Darby canine kidney (MDCK) cells. However, the exact mechanism of FN is not fully understood. To examine the role of FN in crystal-cell interaction, we generated stably transfected MDCK cells that overexpress FN. Materials and Methods: MDCK cells were transfected with rat FN cDNA. First, we assessed cell injury by addition of calcium oxalate monohydrate (COM) crystals. Next, we examined the effect of FN on the adhesion of COM crystals. Finally, we studied the association of COM crystals by scanning electron microscopy. Results: Cell injury was significantly reduced in the transfected cells relative to control MDCK cells. In the inhibitory assay, crystal adhesion decreased markedly as compared with control MDCK cells. Morphological study showed that few crystals were attached to the surface of the transfected cells. Conclusions: We elucidated the relationship between crystal-cell interaction and FN by using FN-overexpressing MDCK cells. We suppose that FN inhibits the adhesion of crystals to cells by coating the renal tubular epithelial cells.
There have been no recurrence since transurethral resection in all IP in the study including the case recognized as aneuploid and positive for PCNA staining. But the present results suggest that among IPs, considered generally as a benign tumor, the case which has high proliferating character exists.
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