A Biomimetic, Copolymeric Membrane for Cell‐Stretch Experiments with Pulmonary Epithelial Cells at the Air‐Liquid Interface

Abstract

Chronic respiratory diseases are among the leading causes of death worldwide, but only symptomatic therapies are available for terminal illness. This in part reflects a lack of biomimetic in vitro models that can imitate the complex environment and physiology of the lung. Here, a copolymeric membrane consisting of poly(ε‐)caprolactone and gelatin with tunable properties, resembling the main characteristics of the alveolar basement membrane is introduced. The thin bioinspired membrane (≤5 μm) is stretchable (up to 25% linear strain) with appropriate surface wettability and porosity for culturing lung epithelial cells under air–liquid interface conditions. The unique biphasic concept of this membrane provides optimum characteristics for initial cell growth (phase I) and then switch to biomimetic properties for cyclic cell‐stretch experiments (phase II). It is showed that physiologic cyclic mechanical stretch improves formation of F‐actin cytoskeleton filaments and tight junctions while non‐physiologic over‐stretch induces cell apoptosis, activates inflammatory response (IL‐8), and impairs epithelial barrier integrity. It is also demonstrated that cyclic physiologic stretch can enhance the cellular uptake of nanoparticles. Since this membrane offers considerable advantages over currently used membranes, it may lead the way to more biomimetic in vitro models of the lung for translation of in vitro response studies into clinical outcome.

Development of a dynamic in vitro stretch model of the alveolar interface with aerosol delivery

“…Besides improving the uniformity of the coating, other biocompatible materials such as natural/artificial hybrid composites with similar elastic properties but more conducive to cell growth and more effective at ensuring the formation of a contiguous cell monolayer or 3D full-thickness epithelial tissue could be developed (Doryab et al, 2019). In this direction, we have recently fabricated a biohybrid membrane with mechanical properties suitable for use in stretching experiments in MALI under both physiologic and pathological conditions (Doryab et al, 2020).…”

A Bioinspired in vitro Lung Model to Study Particokinetics of Nano-/Microparticles Under Cyclic Stretch and Air-Liquid Interface Conditions

“…5 µm) compared to the alveolar-capillary tissue barrier (ca. 1 µm) and higher stiffness [uniaxial Young's modulus: 1.8 ± 0.7 MPa (1D stretch); 0.78 ± 0.24 MPa (3D stretch)], which is similar to or better than other typically used porous membranes for lung cell-stretch cultures (e.g., PDMS), but still about 100fold lager than the elastic modulus (3-6 kPa) reported for alveolar walls/tissue (Doryab et al, 2020). Moreover, the ideal membrane is as bioactive as possible to provide optimum growth conditions for (primary) cell cultures and perfectly permeable to minimize membrane effects on transbarrier transport measurements.…”

“…We have recently introduced a novel porous and elastic membrane for in vitro cell-stretch models of the lung cultured under ALI conditions (Doryab et al, 2020). This innovative hybrid biphasic membrane, henceforth referred to as Biphasic Elastic Thin for Air-liquid culture conditions (BETA) membrane, was developed to optimize membrane characteristics for the two phases of cell-stretch experiments under ALI conditions, namely the initial cell seeding, attachment and growth phase under submerged cell culture conditions (phase I) followed by an ALI acclimatization and cell-stretch phase at the ALI (phase II).…”

“…Subsequently, dissolution of the sacrificial material results in sufficient porosity, permeability and stretchability for up to 25% reversible linear strain (without plastic deformation), granting suitable ALI cell culture conditions under cyclic mechanical stretch (phase II). In contrast to typically used stretchable poly(dimethylsiloxane) (PDMS) membranes, the BETA membrane is bioactive enough to support the proliferation and formation of a confluent layer of alveolar (A549) and bronchial (16HBE14o − ) epithelial cells without pre-coating with ECM proteins (e.g., Matrigel) (Doryab et al, 2020).…”

“…This is supported by newly applied analytical parameters (e.g., 3D porosity and mapping of surface topology of the membrane). Moreover, we provide a detailed technical description of the recently introduced Cyclic In VItro Cellstretch (CIVIC) bioreactor for cell-stretch experiments under ALI conditions (Doryab et al, 2020) with particular attention to refinements over its earlier version (MALI, Moving Air-Liquid Interface bioreactor) (Cei et al, 2020). Subsequently, the effect of cyclic stretch on the particokinetics of aerosol-delivered nano-(100 nm) and microparticles (1,000 nm) in an alveolar tissue barrier model (A549) cultured under ALI conditions was investigated quantitatively with respect to size-dependent cellular uptake and transepithelial transport of particles.…”