Biomimetic Surfaces for Preservation of Alveolar Type II Cells

Poon, James 1, 2; Suzuki, Takaya 2; Carleton, Miranda 2; Karoubi, Golnaz 2; Liao, Zhongfa 3; Aitchison, J. Stewart 3; McGuigan, Alison 1, 4; Waddell, Thomas 1, 2, 5;

1. Institute of Biomaterials & Biomedical Engineering, University of Toronto; 2. Latner Thoracic Surgery Research Laboratories and the McEwen Centre for Regenerative Medicine, Toronto General Hospital; 3. Electrical & Computer Engineering, University of Toronto; 4. Department of Chemical Engineering & Applied Chemistry, University of Toronto; 5. Institute of Medical Science, University of Toronto

Current culture models of distal lung are limited by incorrect three-dimensional (3D) architecture leading to a reduction in asymmetric division and loss of phenotype. Traditionally, alveolar epithelial cells (AEC) have been grown on 2D plastic surfaces and, more recently, modeled in complex microfluidic lung-on-a-chip devices. Isolated AEC cells rapidly lose expression of progenitor markers (surfactant protein C (SPC)) and transition from a cuboidal to spread morphology that is typical of transdifferentiated cells, which limits the investigation of AECs in vitro. 3D culture models such as bead suspension culture, in-matrigel colony formation, or organoid culture exist but these models do not precisely recapitulate the in vivo AEC geometric niche. We hypothesize that physiologically-relevant, defined architecture will provide the geometric cues necessary to maintain AEC progenitor phenotype and function.

Using electron beam lithography and deep reactive-ion etching techniques, we developed a simple, scalable 3D platform for cultivating AECs on polydimethylsiloxane (PDMS) surfaces that mimic the physical architecture of the alveolus with hemispherical cavities. We cultured primary mouse distal lung AECs (CD31-CD45-EpCAM+), which after 24 h were able to form single-cell-lined hollow cavities of 50 and 200 µm diameter. Surfaces with 50 µm hemispheres promoted AEC survival and preserved progenitor phenotype after 5 days (Day 0 = 58.7% vs. Day 5 = 60.7% SPC+ cells), compared to flat controls (24.1% SPC+ cells at day 5). No effect on phenotype preservation was observed for AECs cultured in 200 µm hemispheres (22.6% SPC+ cells at day 5). These results suggest different architectures produce differences in preservation of cell phenotype and that an appropriate microenvironment is sufficient for maintaining mouse distal lung cells. This system advances the design of tissue mimetics that can be used in disease modeling and evaluation of novel therapies for the lung.