Abstract
The kidney proximal tubule is the primary site for solute reabsorption, secretion and where kidney diseases can originate, including drug-induced toxicity. Two-dimensional cell culture systems of the human proximal tubule cells (hPTCs) are often used to study these processes. However, these systems fail to model the interplay between filtrate flow, fluid shear stress (FSS), and functionality essential for understanding renal diseases and drug toxicity. The impact of FSS exposure on gene expression and effects of FSS at differing rates on gene expression in hPTCs has not been thoroughly investigated. Here, we performed RNA-sequencing of human RPTEC/TERT1 cells in a microfluidic chip-based 3D model to determine transcriptomic changes. We measured transcriptional changes following treatment of cells in this device at three different fluidic shear stress. We observed that FSS changes the expression of PTC-specific genes and impacted genes previously associated with renal diseases in genome-wide association studies (GWAS). At a physiological FSS level, we observed cell morphology, enhanced polarization, presence of cilia, and transport functions using albumin reabsorption via endocytosis and efflux transport. Here, we present a dynamic view of hPTCs response to FSS with increasing fluidic shear stress conditions and provide insight into hPTCs cellular function under biologically relevant conditions.
Highlights
The kidney proximal tubule is the primary site for solute reabsorption, secretion and where kidney diseases can originate, including drug-induced toxicity
Renal proximal tubules (PTs) of the nephron contain proximal tubule cells (PTCs), a specialized cell type responsible for active protein trafficking, and the reabsorption function of the k idney[2]. Given their essential role in drug metabolism, modeling of PTCs is important for pharmacology research, as new drugs need to be tested for their effects on kidneys, especially proximal tubules, due to their increased contact with the excretion pathways involving a complex interplay of solute carrier (SLC) transporters[1,3,4,5]
Cells cultured under continuous fluid shear stress (FSS) and three-dimensional (3D) flow models have gained increasing interest due to their ability to recreate precise cellular organizations and previous work has shown that PTC cultures exposed to FSS in a 3D model more closely recapitulate in vivo PTs morphology and function; these studies have explored widely differing FSS used on diverse cell types[12,13,14,15]
Summary
The kidney proximal tubule is the primary site for solute reabsorption, secretion and where kidney diseases can originate, including drug-induced toxicity. Two-dimensional cell culture systems of the human proximal tubule cells (hPTCs) are often used to study these processes These systems fail to model the interplay between filtrate flow, fluid shear stress (FSS), and functionality essential for understanding renal diseases and drug toxicity. At this physiologically-relevant level of fluid shear stress, we assessed cell morphology, presence of cilia, and transport functions such as endocytosis and efflux transport This detailed characterization demonstrates that our 3D model provides a platform for studying human kidney biology and global genomic factors contributing to PTCs function, indicating that it can serve as a useful tool for evaluating renal biology, pathophysiology, and pharmaceutically-induced nephrotoxicity
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