Kidney on a Chip Model in conjunction with systems biology modelling to predict renal pharmacokinetic drug-drug interactions

A suite of hepatic metabolic in vitro tools, such as recombinant enzymes and hepatocytes, have been used in conjunction with systems biology modelling to predict drug pharmacokinetics (PK) in animals. This approach has become a stalwart in the discovery of new drugs over the last 5 years and has led to a reduction in the use of animals as well as giving a better understanding of the processes that drive the PK of a drug at the cellular level. However, limited research has been carried out on in vitro renal cellular tools in conjunction with systems biology modelling in order to predict the renal contribution to the PK of a drug. Currently, renal drug clearance is predicted in human by carrying out invasive PK studies in animals and investigating whether an empirical relationship exists between the different species. In many cases an empirical relationship is not established due to species differences in transporter activity and the prediction of the renal contribution to the PK of a drug for a target species becomes uncertain. In addition to the prediction of renal drug clearance, an established renal in vitro cellular set of tools in conjunction with systems biology modelling would allow the prediction of renal drug-drug interactions.

Currently in the Paine lab, mixed primary proximal (PTC) and distal tubular cell (DTC) monolayers are established in a transwell format using established methods from rat and pig kidney tissues and the kinetics of drug movement in these transwell monolayer culture systems have been investigated. However, one of the major drawbacks of transwell systems is that vital 3D architecture is not present leading to "leaky" junctions and under expression of membrane transporters. Recently, The Wyss Institute at Harvard University have shown that including haemodynamic flow into an in vitro model leads to a more realistic representation of the blood brain barrier.

Recent studies have highlighted the theoretical and experimental impact of haemodynamic flow on membrane recycling. Haemodynamic flow is therefore expected to drive the exocytosis of cytosolic membrane transporters that could, in turn, provide an explanation for the deficiency of transwell monolayer cultures and the potential morphological change of major membrane organelles. The objectives of the herein proposal are to develop mixed primary proximal cell (PTC) and distal tubular cell (DTC) cultures with an organ on a chip system using rat, pig and human (if available) tissue. Tight junction integrity will be assessed by TEER measurements and sodium fluorescein permeability and transporter (OATs,OCTs, MRPs, MDR1) protein levels assessed by mRNA, immunocytochemistry and western blotting (Years 1-2). The effect of haemodynamic flow will be assessed by varying the hydrostatic pressure load though the Kidney on a chip model via a micro pump. The kinetic activity of drugs known to undergo renal clearance will be measured using HPLC-MS/MS. Membrane transporter saturation parameters (Km; Vmax) will be determined for a range of pressures. Known drug transporter inhibitors will be investigated in the presence of the renally cleared drugs and IC50's determined (Years 2-3). Systems biology models using mathematical and kinetic modelling software such as Matlab, Berkeley Madonna and Phoenix, in conjunction with the organ on a chip kinetic data will be built to model and validate a) the effect of pressure change on transporter function b) predict existing in vivo renal clearance data and c) predict known in vivo renal drug-drug interactions for both marketed drugs and novel literature compounds (Years 3-4).