Epithelial folding of alveolar cells derived from human induced pluripotent stem cells on artificial basement membrane

Epithelial folding depends on mechanical properties of both epithelial cells and underlying basement membrane (BM). While folding is essential for tissue morphogenesis and functions, it is difficult to reca-pitulate features of a growing epithelial monolayer for in vitro modeling due to lack of in vivo like BM. Herein, we report a method to overcome this difficulty by culturing on an artificial basement membrane (ABM) the primordial lung progenitors (PLPs) from human induced pluripotent stem cells (hiPSCs). The ABM was achieved by self-assembling collagen IV and laminin, the two principal natural BM proteins, in the pores of a monolayer of crosslinked gelatin nanofibers deposited on a honeycomb micro-frame. The hiPSC-PLPs were seeded on the ABM for alveolar differentiation under submerged and air-liquid in-terface culture conditions. As results, the forces generated by the growing epithelial monolayer led to a geometry-dependent folding. Analysis of strain distribution in a clamped membrane provided instru-mental insights into some of the observed phenomena. Moreover, the forces generated by the growing epithelial layer led to a high-level expression of surfactant protein C and a high percentage of aquaporin 5 positive cells compared with the results obtained with a nanofiber-covered bulk substrate. Thus, this work demonstrated the importance of recapitulating natural BM for advanced epithelial modeling. Statement of significance The effort to develop in vitro epithelial models has not been entirely successful to date, due to lack of in vivo like basement membrane (BM). This lack has been overcome by using a microfabricated dense thin and pliable sheet like structure made of natural BM proteins. With such an artificial BM, alveolar epithelial deformation and folding could be studied and date could be correlated to numerical analyses of a plate theory. This method is simple and effective, enabling further developments in epithelial tissue modeling.(c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study developed a method to overcome the lack of in vivo-like basement membrane (BM) for in vitro modeling by culturing primordial lung progenitors (PLPs) on an artificial basement membrane (ABM) composed of collagen IV and laminin. The forces generated by the growing epithelial monolayer on the ABM led to geometry-dependent folding and enhanced expression of surfactant protein C and aquaporin 5 compared with a nanofiber-covered substrate. This work emphasizes the importance of recapitulating natural BM for advanced epithelial modeling.