Mature induced-pluripotent-stem-cell-derived human podocytes reconstitute kidney glomerular-capillary-wall function on a chip

Abstract

An in vitro model of the human kidney glomerulus — the major site of blood filtration — could facilitate drug discovery and illuminate kidney-disease mechanisms. Microfluidic organ-on-a-chip technology has been used to model the human proximal tubule, yet a kidney-glomerulus-on-a-chip has not been possible because of the lack of functional human podocytes — the cells that regulate selective permeability in the glomerulus. Here, we demonstrate an efficient (> 90%) and chemically defined method for directing the differentiation of human induced pluripotent stem (hiPS) cells into podocytes that express markers of the mature phenotype (nephrin+, WT1+, podocin+, Pax2−) and that exhibit primary and secondary foot processes. We also show that the hiPS-cell-derived podocytes produce glomerular basement-membrane collagen and recapitulate the natural tissue/tissue interface of the glomerulus, as well as the differential clearance of albumin and inulin, when co-cultured with human glomerular endothelial cells in an organ-on-a-chip microfluidic device. The glomerulus-on-a-chip also mimics adriamycin-induced albuminuria and podocyte injury. This in vitro model of human glomerular function with mature human podocytes may facilitate drug development and personalized-medicine applications.

Developmentally inspired human ‘organs on chips’

“…Importantly, culturing iPSC-derived motoneurons and brain microvascular endothelial cells together in an organ chip model of the neuromuscular unit significantly enhanced function and in vivo-like maturation of spinal cord neural tissue (Sances et al, 2018). When cultured on chip, human iPSC-derived kidney podocytes also matured further by extending long foot processes much as they do in vivo (Musah et al, 2017). Hence, organ chip approaches could be used to enhance stem cell differentiation in vitro and to study patientspecific developmental responses for personalized medical applications in the future.…”

“…When different cell types are placed in the correct microenvironment with appropriate positioning of tissues relative to one another, they spontaneously accumulate ECM along their interface, switch on developmental programs and self-organize, resulting in formation of highly polarized and differentiated epithelial tissue structures that closely resemble those seen in the organs of our bodies, such as mucus and surfactant-producing alveolar epithelium (Huh et al, 2010), ciliated pseudostratified airway epithelium (Benam et al, 2016a), 3D finger-like intestinal villi (Kim et al, 2012;Kasendra et al, 2018;Workman et al, 2018) and reconstitution of podocyte-ECMendothelial contacts of the kidney glomerulus (Musah et al, 2017).…”

“…Many adult cell types are available commercially; however, tissue-specific organoids also can be created by isolating stem cells from patient biopsies, and this approach has been leveraged as a cell source to create functional human intestine chips that form highly differentiated villus structures (Kasendra et al, 2018). Induced pluripotent stem cell (iPSC) approaches have also been leveraged to create various types of specialized cells for organ chip studies, including cardiomyocytes, kidney podocytes, brain microvascular endothelial cells, and intestinal enterocytes (Wang et al, 2014(Wang et al, , 2017Musah et al, 2017;Workman et al, 2018), but their clinical relevance is sometimes questioned because most iPSCs generated in vitro remain fetal-like or neonatal in nature. Importantly, culturing iPSC-derived motoneurons and brain microvascular endothelial cells together in an organ chip model of the neuromuscular unit significantly enhanced function and in vivo-like maturation of spinal cord neural tissue (Sances et al, 2018).…”

“…Furthermore, because of our deep belief that mechanical forces govern cell and tissue development, it was crucial to replicate organ-relevant physical cues, which in the case of the lung involved surface tension at an air-liquid interface, as well as both fluid flow through the vascular lumen and cyclic mechanical distortion of the tissue-tissue interface due to breathing motions. When we later created a model of the human intestine, we similarly applied cyclic mechanical strain, but at different rates and degrees, to mimic effects of peristalsis-like motions (Kim et al, 2012;Kasendra et al, 2018); when we built a kidney glomerulus chip (Musah et al, 2017), we recreated the deformations this organ unit experiences due to pulsatile blood flow with every beat of the heart. Most importantly, in all of these studies, these mechanical perturbations were absolutely required to drive cell and tissue differentiation, and to robustly mimic human organ-level physiology, as well as pathophysiology.…”

“…1A,B; Huh et al, 2010). Since this study was published, multi-channel design approaches have been used by multiple research groups to build microfluidic organ-chip models of the human lung small airway, skin, kidney, intestine, placenta, blood-retinal barrier, blood-brain barrier, neurovascular unit and neuromuscular unit, among others (Kim et al, 2012;Achyuta et al, 2013;Abaci et al, 2015;Benam et al, 2016a;Lee et al, 2016;Musah et al, 2017;Yeste et al, 2017;Wang et al, 2017;Workman et al, 2018;Kasendra et al, 2018;Sances et al, 2018; reviewed by Bhatia and Ingber, 2014).…”