Human primary renal proximal tubular cells

In a study of six mercury compounds, mercury chloride, mercury nitrate, sodium ethylmercurithi-osalicylate, methyl mercury chloride, mercury acetate and phenylmercury acetate in MDCK cells, LLC-PKl cells and human primary proximal tubular cells (hPTC) and non-renal cell lines (SAOS and Hep G2) it was found that all mercury compounds were toxic to all cell types as evidenced by neutral red uptake, thymidine incorporation and the MTT assay [189]. However, sodium ethylmercurithiosalicylate, methyl mercury chloride and phenylmercury acetate were one order of magnitude more toxic than the other compounds. In addition the GSH synthesis inhibitor L-buthionine sulfoximine (BSO) potentiated the toxicity of all mercury compounds [189]. In a study using primary rabbit proximal tubular cells it was also shown that methyl mercury chloride is more toxic than mercury chloride [190]. Differences in the extent and rate of metal uptake were also evident. Maximum cellular uptake of Hg " occurred within 6-24 hr after exposure and was not concentration-dependent, whereas maximum uptake of CHgHg" occurred within 3 hr of exposure and was concentration- dependent [190]. 

There have been several investigations into the use of hormonally defined medium in order to maintain the differentiation of primary cells, as it is suspected that serum may be a factor in dedifferentiation. The application of defined medium also allows a more standardized approach to cell culture delivering greater reproducibility and transferability. For renal tubular epithelial cells defined medium supplements have been described as far back as 1982 [148], We have been, over the last number of years, successfully cultivating human renal proximal tubular cells (primaries and cell lines) in serum free hormonally defined medium containing EGF, hydrocortisone, insulin, transferrin, and sodium selenite using DMEM-Hams F12 as the base medium [36, 112, 114, 149], Both the HK-2 cell line and the RPTEC/TERT1 have been developed in serum-free conditions. 

Warren JW, Mobley FILT, Flebel JR, Trifillis AL. Cytolethality of hemolytic Escherichia Coli to primary human renal proximal tubular cell obtained from different donors. Urology 1995 45 706-710. 

Lash, L.H., Putt, D.A., Hueni, S.E., Krause, R.J., and Elfarra, A.A. (2003) Roles of necrosis, apoptosis, and mitochondrial dysfunction in S-(l,2-dichlorovinyl)-L-cysteine sulfoxide-induced cytotoxicity in primary cultures of human renal proximal tubular cells. J. Pharmacol. Exp. Ther. 305, 1163-1172. 

McGoldrick TA, Lock EA, Rodilla V, Hawks worth GM. 2003. Renal cysteine conjugate C-S lyase mediated toxicity of haloge-nated alkenes in primary cultures of human and rat proximal tubular cells. Arch Toxicol 77(7) 365-370. 

Radford R et al (2012) Carcinogens induce loss of the primary cilium in human renal proximal tubular epithelial cells independently of effects on the cell cycle. Am J Physiol Renal Physiol 302(8) F905-F916... 

Induction of oollagen secretion (a marker of fibrosis) has been shown in the OK proximal tubular cell line and in cultured primary human renal proximal tubular oells exposed to ochratoxin A. Collagen seoretion was both time and dose dependent, as was the induction of cell toxicity (Sauvant et al., 2005a). 

Renal Effects. The characteristics of early or acute lead-induced nephropathy in humans include nuclear inclusion bodies, mitochondrial changes, and cytomegaly of the proximal tubular epithelial cells dysfunction of the proximal tubules (Fanconi s syndrome) manifested as aminoaciduria, glucosuria, and phosphaturia with hypophosphatemia and increased sodium and decreased uric acid excretion. These effects appear to be reversible. Characteristics of chronic lead nephropathy include progressive interstitial fibrosis, dilation of tubules and atrophy or hyperplasia of the tubular epithelial cells, and few or no nuclear inclusion bodies, reduction in glomerular filtration rate, and azotemia. These effects are irreversible. The acute form is reported in lead-intoxicated children, whose primary exposure is via the oral route, and sometimes in lead workers. The chronic form is reported mainly in lead workers, whose primary exposure is via inhalation. Animal studies provide evidence of nephropathy similar to that which occurs in humans, particularly the acute form (see Section 2.2.3.2). 

Therefore, differences between properties of PTC in vivo in the normal adult kidney and in vitro properties of PTC and stem cell-derived proximal tubular-like cells may not just reflect dedifferentiation or lack of full terminal differentiation. Rather, altered marker expression patterns seem to be related to the biology of these cells and their response to altered conditions. It is important to keep in mind that human and animal PTC are probably always different under in vitro conditions (compared to the in vivo situation), unless the in vivo simation can be exactly mimicked. This is also important with respect to the interpretation of the differentiation status of stem cell-derived proximal tubular-like cells, as the expression of progenitor markers and markers specific for other renal cell types is normal under in vitro conditions, also in HPTC. For practical reasons we suggest to always compare stem cell-derived cells carefully to respective primary cells cultivated in vitro, which gives a realistic impression of the best possible differentiation state that can be achieved under the conditions used. In addition, rigorous functional tests (e.g., of transporter functions) are often more informative than marker expression patterns in terms of the applicability of stem cell-derived cells for drug screening. 

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