hTERT-immortalized Kidney Models for Drug Screening and Toxicity Assays

Kidneys are the major organs in the body responsible for the elimination of many xenobiotics and prescription drugs; having relevant models for drug interaction and toxicity studies is a necessity. Primary cells and continuous cell lines have traditionally been used in these studies. We have generated human telomerase reverse transcriptase (hTERT) immortalized renal proximal tubule epithelial cells (hTERT-RPTEC) that can overcome the limitations of donor variability and senescence of primary cells, yet show key primary cell functionality. These cells have the expected expression of E-cadherin and CD31 and display typical dome formation morphology. One limitation of primary RPTEC is that the expression of key solute carrier (SLC) transporters OAT1, OCT2, and OAT3 is lost during culture and expansion of these cells. To overcome this loss of expression, we have stably overexpressed each of these carriers in the hTERT-RPTEC background. These cells maintain correct marker expression (both overexpressed SLC and endogenous RPTEC markers) and growth characteristics. Functional uptake studies using fluorescently labeled 6-carboxyfluorescein (6-CF) and ethanaminium iodide (EAM-1), and inhibition of these uptakes by novobiocin and cimetidine demonstrate the functionality of the overexpressed SLCs. These cells have also been used to study the mechanism of drug toxicity (eg, antiviral drugs tenofivir, tenofivir DF, cidofivir) using cell viability assays. In aggregate, these data demonstrate that the immortalized hTERT-RPTEC and the SLC-expressing stable variants (hTERT-RPTEC-OAT1, -OCT2, and -OAT3) are reliable kidney models that can be used for drug screening and toxicity assays.