A microphysiological in vitro model of the renal proximal tubule reabsorptive barrier

Abstract

Microfabricated in vitro kidney tissue models replicate essential components of in vivo kidney physiology, providing a platform for direct observation of controlled yet physiologically-representative kidney tissue. Currently, static and flat cell culture environments serve as platforms to study cell behavior, tissue structure formation, renal disease mechanisms, and drug development. Petri dishes, well plates, and flasks sustain cell growth, but their environments lacks physiological cues that are present in the in vivo environment, prompting cell responses that may not be physiologically-representative. One alternative to these flat, static environments is to use animal models, which offer an in vivo environment but inherently come with uncontrollable fluctuations that introduce variables into the test setting. Microfabricated kidney tissue models improve upon other in vitro kidney tissue models by precisely controlling the geometry of device components via high-resolution fabrication and forming processes. Control over device component geometry consequently dictates control over mechanical parameters which influence and guide kidney cell and tissue structure and function. In addition, microfabrication methods create platforms compatible with the various cells, materials, and chemistries which also provide cues leading to replication of critical kidney function in vitro. The objective of this work is to develop an in vitro model of kidney tissue with physiologically-accurate replication of renal proximal tubule function. In chapter one, we have established a microphysiological model system of renal proximal tubule epithelia by a) characterizing the effect of user-defined physiological parameters on renal proximal tubule cells, and b) incorporating those parameters into a bilayer microfluidic device to model the renal reabsorptive barrier. In chapter two, we have characterized function o f our renal tissue model to establish metrics o f kidney-specific function , including reabsorption. In chapter three, we extend our proximal tubule model to include microvascular endothelial tissue and applied the metrics established in chapter 2 to quantify reabsorptive barrier function in the coculture model. This microphysiological model system provides an in vitro platform on which to model reabsorptive tissue barriers with kidney-specific function which enables meaningful applications for understanding biological transport phenomenon, observing underlying disease mechanisms, and improving the drug discovery process.