Proximal Tubule MPS Flow

• Kidney toxicity assays
• Disease modelling
• High content imaging (HCI)

Proximal tubule cells under flow form a polarised monolayer showing defined and orderly expression of the epithelial tight junction ZO-1

Limitations of current models

Many current renal in vitro models only have a limited ability to detect early indicators of nephrotoxicity. For example, immortalised cell lines or frozen primary proximal tubule cells (PTCs) do not retain physiologically relevant expression of key transporter proteins involved in drug handling resulting in models failing to be sufficiently sensitive to test compounds at clinically relevant concentrations. Other MPS systems, Organ-on-Chip and kidney-chip platforms have expanded in recent years to improve the predictability of preclinical studies. These systems are also limited in sensitivity due to the quality of the cells (immortalised or frozen PTCs), and the low number of cells in each chip. These MPS systems also tend to be low-throughput, restricting their use. To address these points, Newcells MPS Flow model has been developed in high-throughput formats and utilises freshly isolated PTCs which retain all key renal transporters and maintain functionality.

Increased Sensitivity

From an in vitro toxicological perspective, the upregulation of gene transcripts associated with key transporter proteins such as those that comprise the OAT and OCT families as well as endocytic transporters like Megalin and Cubilin is key to maintaining the primary cell phenotype and function of the PTC in culture after shear stress stimulation. This has been shown for aProximate™ MPS Flow in our functional toxicity with cells having undergone exposure to shear stress showing our MPS flow systems are even more representative of in vivo. Furthermore, due to the high surface area on the Transwell® inserts, a large number of PTCs are seeded, further increasing the sensitivity and allowing detection of  biomarkers such as NGAL, Clusterin and KIM-1.

For the aProximate™ MPS Flow model, cells are seeded on the basal side of the Transwell®, unlike the static model where the cells are seeded on the apical side.  The cells are then expanded to confluency in static culture before the inserts are placed into the microfluidic plate and media is added into the channel.

The MPS flow plate is then placed on a rocker platform tilting at a fixed frequency (0.1 cycles/min) allowing periodic, bi-directional, gravity-induced movement of media from one chamber to the other. This movement exposes the monolayer of cells to a continuous basolateral fluid shear stress that accurately mimics in vivo shear stress.