High-resolution Inkjet Bioprinting of an in vitro Human Alveolar Barrier Construct

Abstract

An alveolar barrier in the gas exchanging region of the lung consists of epithelium, basement membrane, and endothelium with a thickness of less than 2 μm. The thin structure is critical for maintaining pulmonary function such as gas exchange. Efforts have been made to fabricate the biomimetic human alveolar barrier model, one of the essential model systems for pulmonary drug and inhalation particle test in disease studies, drug discovery and toxicology, by using microfluidic devices and bioprinting technology. However, to date no model can precisely mimic the thin structure with the 3 layers that is an crucial feature of for gas exchanging function. Here, we present human alveolar barrier model with about 10 μm-thick, containing multi-type alveolar cells in 3 layers. We fabricate the model with 4 alveolar cell lines, including type 1 - like alveolar cell (NCI-H1703), type 2 alveolar cell (NCI-H441), lung fibroblast (MRC5), and lung microvascular endothelial cell (HULEC-5a). High-resolution drop-on-demand inkjet printing enables the fabrication of the thin alveolar barrier model of 10 μm by controlled deposition of multi-type alveolar cells as a thin layer. In order to demonstrate the level of biomimetics, the structure and function of the 3D-printed model are evaluated by the measurements of thickness, histology, barrier integrity tests, gene expression analysis, and immunocytochemistry. As an application, necrosis and barrier collapse were confirmed after exposing this model to fine dust. We show that inkjet printing is a versatile tool to fabricate very thin tissue models, and our alveolar barrier model show its potential to be used for in vivo studies in pathology, drug discovery, and toxicology.