Figure 1. 3D convoluted renal proximal tubule on chip.

(a) Schematic of a nephron highlighting the convoluted proximal tubule, (b,c) corresponding schematics and images of different steps in the fabrication of 3D convoluted, perfusable proximal tubules, in which a fugitive ink is first printed on a gelatin-fibrinogen extracellular matrix (ECM) (i), additional ECM is cast around the printed feature (ii), the fugitive ink is evacuated to create an open tubule (iii), and PTEC cells are seeded within the tubule and perfused for long time periods (iv); (d) a 3D rendering of the printed convoluted proximal tubule acquired by confocal microscopy, where actin is stained in red and nuclei are blue; the white dotted line denotes the location of the cross-sectional view shown below in which PTEC cells circumscribe the open lumens in 3D, scale bar = 500 μm, (e) higher magnification view of the region in (d) denoted by the white rectangle, scale bar = 200 μm, (f) 3D rendering of the convoluted renal proximal tubule where an open lumen circumscribed with an epithelial lining is directionally perfused on chip and Na/K ATPase is stained in red, acetylated tubulin is orange highlighting the primary cilia, and nuclei are blue, scale bar = 50 μm.