Kidney proximal tubule cell model for safety/efficacy and transporter studies
aProximate™ is one of the most advanced, near physiological, in vitro, kidney proximal tubule cell (PTC) models. aProximate™ PTCs are derived from fresh human kidney tissue and grown on Transwells® where they remain as a functional polarised cell layer that forms tight junctions. In contrast to other primary and immortalised kidney proximal tubule cells in culture, aProximate™ PTCs retain high expression of the key transporters involved in drug handling including Megalin and Cubilin, which is ideal for drug transporter studies. Studies with aProximate™ can give you a detailed mechanistic understanding of how new drugs are transported and eliminated through the kidney and how they interact with other drugs prescribed to the target patient population to help mitigate risk of renal toxicity.
Available analytical readouts
Flux and net transport measurements
Measurement of intracellular drug and metabolite concentrations
Identification of transporter-mediated drug-drug interactions
Early renal damage biomarkers
Cell viability
Tight junctions between aProximate™ proximal tubule cells shown by ZO-1 staining
Multiple species
Freshly isolated PTCs
Validated model
aProximate™ Model Highlights
Accelerate your lead compound selection by understanding their mode of action in kidney tissue
1.
Fully differentiated and polarised kidney proximal tubule cells
2.
High level of expression of all key renal transporters
3.
High predictivity of in vivo and clinical outcomes
aProximate™ is an ideal model during early and late drug development for understanding drug handling in the kidney proximal tubule cells. In vitro drug testing and modelling in the proximal tubule is a common strategy for mitigating the risk of failure during preclinical and clinical development, especially as several drugs and metabolites are handled by the same transporters. Interactions between new drugs and renal transporters can easily and accurately be evaluated in vitro with aProximate™. The mechanistic insights provided can be used to support regulatory applications or as responses to regulatory agencies.
Primary kidney proximal tubule cells tend to dedifferentiate and lose key phenotypes overtime in culture, after a freeze-thaw cycle and after immortalization as shown by the loss of transporter and metabolic enzymes involved in drug transport and metabolism. They also display an altered balance between glycolytic and non-glycolytic pathways as well as altered redox activity compared to PTCs in vivo. aProximate™ PTCs distinguish themselves from other PTC cells as they are freshly isolated from kidney tissue, retaining accurate near-physiological phenotype and function.
aProximate proximal tubule cell (PTC) model. Schematic diagram of aProximate PTCs showing the expression of all key renal transporters (left) and the formation of tight junctions as shown by ZO-1 tight junction protein labelling (bottom right). Diagram of Transwell plates demonstrating the aProximate model: PTCs grown on filters remain fully differentiated as a polarised cell layer (top right).
Evaluation and prediction of nephrotoxicity remains a challenging priority during the early and late drug development process. For example, some classes of drugs such as anti-retrovirals, antibiotics, antisense oligonucleotides or siRNA therapies are known to accumulate in kidney proximal tubule cells affecting cell function, possibly inducing nephrotoxicity. Reliable predictive or investigative toxicology tools for early evaluation are needed to avoid drug-induced kidney injury during clinical studies, which are often undetected in animal models due to their low sensitivity. aProximate™ allows for the detection of FDA-qualified kidney-specific biomarkers in response to injury such as KIM-1, NGAL and Clusterin, which are more sensitive than blood and urine biomarkers such as creatinine. This confirms the suitability to assess kidney proximal tubule cell toxicity and evaluate renal drug safety during drug discovery using aProximate™ as an in vitro model.
aProximate™ is fully validated for many applications (For example, see our collaborative publication with Takeda pharmaceuticals: Bajaj et al., 2019 https://doi.org/10.1016/j.tox.2020.152535)
Fully differentiated and functional kidney proximal tubule cells
Form a polarised cell layer with tight junctions
Expression of all key basolateral and apical transporters involved in drug handling, including Megalin and Cubilin
Measurement of net flux
Detection of clinical biomarkers to detect early nephrotoxicity
Unique species comparison capability
High throughput
aProximate™ expresses most relevant kidney transporters unlike other primary and immortalised PTCs such as RPTEC, KH2 and HEPTEC, which express very low or negligible levels. See table below.
aProximate™ is now available for shipment to customers to perform kidney transporter and toxicity studies in-house. aProximate™ Assay-Ready plates (Human) are provided in either 24-well or 96-well Transwell® format. The cells are shipped in stasis media and require revival at 37oC prior to use. The model is provided with maintenance medium and user guide with a detailed protocol for recovery.
ZO-1 Immunocytochemistry staining of PTCs (red) and Hoescht nuclear staining.
Functional validation of aProximate™ assay-ready plates for transporter assays
Functional validation studies for transcellular flux and uptake of creatinine revealed preferential basolateral-to-apical (JBA) creatinine transport, indicative of normal physiological function. A JBA uptake ratio >1.5 indicates that the cells are functional.
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