Faculteit Dierengeneeskunde

December 2015

Promising in vitro kidney models reduce animal use

A picture of renal tubule cells, by M. Fedecostante, Pharmacology, Utrecht University.

Animal testing in toxicology aims at testing the safety and efficacy of drugs for human and animal health. Drug developers have to expose vital organs like liver, heart and kidney to potential toxic substances for studying objects at risk of developing drug-induced organ toxicity. However, many drugs fail in development prior to reaching the market (drug attrition), after they have already been tested in animals, which is around 25-30%1. Within drug failures, nephrotoxicity accounts for 2% of drug attrition in the preclinical stages, but failures are higher in the last stage of clinical trials, Phase III, being 19%2, according to Prof. dr. Masereeuw, recently appointed as Professor of Pharmacology at Utrecht University and former associate professor of the Department of Pharmacology and Toxicology at Radboud university medical center. This is why there is a need of more predictive human-tissue based in vitro models to test potential nephrotoxic compounds, which can reduce the translational gap between preclinical and clinical stages. By this means, the former research group in Nijmegen of Dr. Masereeuw has developed a patented human renal cell line ciPTEC™ with high predictive value for drug transport and metabolism in the kidney3.

The specific type of renal cells used are proximal tubule cells, because of their task to reabsorb filtered solutes and to excrete waste products and xenobiotics in the urine. These cells are exposed to high-levels of circulating toxins, which makes them vulnerable to drug toxicity. Therefore, the cells are included in the kidney-on-a-chip device (1). Next to this, a bioartificial kidney may be of great help for renal disease patients, by the development of an ex vivo support device that helps in removing toxins that remain in the body after hemodialysis (2). However, in the developmental process of this bioartificial kidney, a 2D-system needs to be optimized which can potentially also reduce animal testing in the future.

1. Kidney-on-a-chip model
Because of the need of highly predictive in vitro models to test the safety and efficacy of potential nephrotoxic compounds, Prof dr. Masereeuw and her research group are working on the development of a kidney-on-a-chip device. This device has won the two-phase competition of the National Centre for the Replacement, Refinement & Reduction of Animals in Research (NC3Rs) CRACK-It Challenge programme NephroTube4, an open innovation programme funding partnerships between Academia, the Industry and SME’s (small and medium sized enterprises) to solve problems related to the 3Rs. The device will also be used in the future to detect sensitive biomarkers of drug-induced kidney injury, to identify nephrotoxicity as early as possible in the drug discovery process. This is of great interest for the pharmaceutical industry, which is why companies like Roche Diagnostics, Pfizer and GlaxoSmithKline have already shown interest in sponsoring the product. In return, they receive early access to the new device when being developed. A successful proof-of-concept of the kidney-on-a-chip device has already been produced by the organ-on-a-chip company MIMETAS, by their OrganoPlate 3D-culturing technology based on microfluidics culture plates5.

The project will last for at least three more years before the new in vitro kidney-on-a-chip model reaches the market. In the future, the model will probably lead to reduced animal use in nephrotoxicity testing.

2. Bioengineered renal tubule
An improved version of the same in vitro renal cell line is included in the development of the bioartificial kidney, existing of living membranes by combining special long-lived renal cells with human-collagen coated membranes6. These 2D-bioactive membranes will eventually lead to the 3D-configuration which mimics physiological kidney function, the bioengineered renal tubule. This is in the initial stage of development at Utrecht University and was initiated in cooperation with the Dutch Kidney Foundation, several Dutch universities and the companies PharmaCell and SupraPolix.
The bioartificial tubule mimics the kidney cell environment ex vivo in such a way that renal tubule cells can excrete waste products and large proteins as efficiently as in the living kidney. In current hemodialysis, problems arise when these toxins cannot be cleared out of the patients’ blood (uremia), resulting in renal diseases. The bioartificial tubule answers to the demand of a waste product removal device that can treat these uremic symptoms in end-stage renal disease patients. However, the clinical application is still far away and before this can be implemented, the function of the 3D-bioactive membrane has to be optimized. The model still has to be validated and will be tested in animals by this means, but Prof dr. Masereeuw does not exclude the possibility of optimizing this in vitro model as alternative to animal testing to test nephrotoxic compounds.

1: Schuster D. et al., Why drugs fail: a study on side effects in new chemical entities, Curr Pharm Des. 2005; 11(27): 3545-59.
2: Guengerich F.P. et al., Mechanisms of drug toxicity and relevance to pharmaceutical development, Drug Metab Pharmacokinet. 2011; 26 (1): 3-14. 
3: Wilmer M.J. et al., Novel conditionally immortalized human proximal tubule cell line expressing functional influx and efflux transporters, Cell Tissue Res. 2010 Feb; 339 (2).
4: Read more about the CRACK-It Challenge program here.
5: Read more information on the website of MIMETAS.
6: Jansen J. et al., Human proximal tubule epithelial cells cultured on hollow fibers: living membranes that actively transport organic cations, Scientific Rep. 2015 Nov. Article 16702.