The kidney plays a critical role in the clearance and elimination of a wide array of xenobiotics, toxins, and endogenous compounds from the body. This is achieved by filtering blood to remove waste products and by regulating electrolyte balance, fluid levels, and pH. Each human kidney contains around one million nephrons, the structural and functional units of the kidney1. Within these nephrons, specialized epithelial cells in the proximal tubules, known as proximal tubule epithelial cells (PTECs), are responsible for reabsorbing essential molecules such as glucose, amino acids, and ions, as well as for secreting drug substrates and potentially toxic substances into the urine2,3,4. In some cases, PTECs may also reabsorb compounds from the urine back into the bloodstream4. Due to their critical role in drug and toxin interactions, primary PTECs isolated from human kidneys provide a valuable tool for studying renal drug-drug interactions (DDIs) and assessing the nephrotoxicity of compounds.
Drug-induced nephrotoxicity poses a significant clinical challenge, as it can lead to acute kidney injury and chronic kidney disease5. Therefore, a deeper understanding of the renal proximal tubule physiology is essential for accurately predicting and characterizing the nephrotoxic potential of drugs and toxins. Traditional in vitro models, including immortalized renal cell lines (e.g., RPTEC-TERT1, HK-2), have limitations in mimicking the complex structure and function of the human proximal tubules6, which operate under dynamic, laminar flow (with a low Reynolds number) and a uniform extracellular matrix (ECM) in vivo7,8. Additionally, traditional two-dimensional (2D) models often fail to functionally express major renal transporters (e.g., organic anion transporter 1 and 3 (OAT1 and OAT3), organic cation transporter 2 (OCT2)) due to rapid degradation and internalization of these proteins6,9,10,11. Animal models, while informative, may not fully replicate human renal physiology and often lack translatability due to species differences in transporter expression and activity12. For example, mOct1 is basolaterally expressed in mouse PTECs, while in humans, the membrane protein expression of OCT1 in the kidney is undetectable13,14.
Advancements in microphysiological systems (MPS) and organ-on-a-chip technologies have enabled researchers to develop in vitro models that closely mimic the three-dimensional (3D) architecture and dynamic fluid flow conditions of human organs15. Our group has previously characterized two MPS models with PTECs16,17, and has utilized these models to conduct toxicity studies18,19,20 and predict drug disposition accurately21. The use of primary PTECs in these models provides significant advantages due to their ability to retain functional characteristics observed in vivo.
Here, we present the protocols for the isolation of human PTECs from an intact human kidney obtained from a deceased donor via a United Network for Organ Sharing (UNOS)-approved organ procurement organization and applying these cultured human PTECs within an MPS platform.