Poster Y10 - A Gravity-Driven Microfluidic Model of the Nephron

Introduction: Chronic kidney disease (CKD) and acute kidney injury (AKI) are growing ailments in populations around the world. In the U.S. alone 1 in 15 Americans is estimated to be living with CKD(1). CKD, while manageable, drastically affects quality of life as it is linked to other comorbidities. Few models accurately depict kidney function outside of the human body. Microphysiological systems (MPS) provide a method to test new drugs and/or drug combinations and to better understand disease progression, while also reducing the need for animal models. Few have shown that this technology can demonstrate the functional components of a human kidney. Previous work has shown a pump-based proximal convoluted tubule and glomerulus on a chip system(2). The goal of this work is to create a simplified, gravity-driven, physiologically realistic model of the human nephron.

Materials and

Methods: Human Umbilical Vein Endothelial cells (HUVECs) were used as a cell model to determine the viability of cells in the gravity-driven MPS. Devices were drawn in SolidWorks CAD software and manufactured from a semi-clear resin (Surgical Guide by FormLabs) using a FormLabs Form3 3D printer. A cell seeding channel was formed via a 3.0 mg/mL collagen I gel, and a 26G needle insert; once the hydrogel solidified the needle was removed. Cells were added at 200µL per device at a concentration of 400,000 cells/mL. Devices were spun at a 45° angle continuously at 4 rotations per minute and kept in an incubator at 37°C and 5% CO2. After 3 days of operation, cells were stained for viability and with a VE-cadherin antibody to probe cell-cell junction formation (Figure 1).

Results, Conclusions, and Discussions: Key features of this device include a low fluid volume and the ability to generate flow using gravity with a custom spinning platform. The benefit of these devices is their use of gravity to produce flow and ease of device alteration. The device design can quickly be altered to fit new needs and then printed in large quantities to increase sample sizes. Gravity-driven devices require less space, materials, and technical expertise to operate. The MPS can be used for a longer period of time, as lower amounts of stress are applied to the physical device. The devices being used also have the ability to recirculate small amounts of medium, better creating a mechanical environment relevant to the human kidney. Cells adhere to the devices and remain viable for a 3-day culture period within the spinning device. VE-cadherin staining demonstrates cell-cell junction formation.

We have generated a novel, gravity-driven MPS that can support cells for 3 days of culture. Future work will focus on the incorporation of additional types of cells present in the nephron and an additional glomerular filtration barrier. This device will be useful for demonstrating kidney function for drug toxicity testing and/or understanding disease progression.

Acknowledgements (Optional): GFSD/GSME Fellowship, Graduate Fellowships for Stem Diversity & NIST