Designing a 3D rhythmically stretchable substrate for growth of alveolar epithelial cells

Nejatian, Maryam (1, 2), Aoki, Fabio (2), Karoubi, Golnaz (1, 2), Waddell, Thomas (1, 2)

(1) Institute of Biomaterials and Biomedical Engineering, University of Toronto

(2) Latner Thoracic Surgery Research Laboratories, University Health Network

The distal lung branches into acinar sacs called alveoli, which are lined with Type I and Type II alveolar epithelial cells (AECs). ATI cells cover approximately 95% of the alveolar surface and are responsible for gas exchange in air-blood interface, while ATII cells produce necessary surfactants. In traditional in vitro studies, AECs are cultured on flat (2D) surfaces, which lack alveolar physiological architecture and do not recapitulate the microenvironment required for proper differentiation. Recent developments in 3D AEC organoid models have been described; however, these models are low-throughput, challenging to analyze, and not easily scalable. Currently, the need exists for a scalable platform with similar alveolar architecture that allows to culture stem cells in a physiologically relevant environment over multiple days. Herein, we propose the prototype of an electro-pneumatically controlled stretchable substrate made of polydimethylsiloxane (PDMS) that is efficient to fabricate and provides a simple to use platform for cell analysis. Our system applies negative pressure to a micron thin membrane through a microchannel, using an electro-pneumatically controlled pump, in order to create dimples that stretch with similar strain magnitude (10% linear strain) and frequency (0.2Hz) as human alveoli. Preliminary results show the versatility of this system in terms of its capability to facilitate a linear strain of up to 16% and surface strain of up to 35% to a membrane as thin as 30um. Future aims will be to evaluate viability of AECs on this system and study the influence of transient stretch-induced changes in viability and function of mature human Type II AECs.