All‐Inkjet‐Printed 3D Alveolar Barrier Model with Physiologically Relevant Microarchitecture

Abstract

With the outbreak of new respiratory viruses and high mortality rates of pulmonary diseases, physiologically relevant models of human respiratory system are urgently needed to study disease pathogenesis, drug efficacy, and pharmaceutics. In this paper, a 3D alveolar barrier model fabricated by printing four human alveolar cell lines, namely, type I and II alveolar cells (NCI-H1703 and NCI-H441), lung fibroblasts (MRC5), and lung microvascular endothelial cells (HULEC-5a) is presented. Automated high-resolution deposition of alveolar cells by drop-on-demand inkjet printing enables to fabricate a three-layered alveolar barrier model with an unprecedented thickness of ≈10 µm. The results show that the 3D structured model better recapitulate the structure, morphologies, and functions of the lung tissue, compared not only to a conventional 2D cell culture model, as expected, but also a 3D non-structured model of a homogeneous mixture of the alveolar cells and collagen. Finally, it is demonstrated that this thin multilayered model reproduce practical tissue-level responses to influenza infection. Drop-on-demand inkjet-printing is an enabling technology for customization, scalable manufacturing, and standardization of their size and growth, and it is believed that this 3D alveolar barrier model can be used as an alternative to traditional test models for pathological and pharmaceutical applications.

3D Bioprinting Strategies, Challenges, and Opportunities to Model the Lung Tissue Microenvironment and Its Function

“…Another important focus of research has been the development of models to study the air-blood barrier and the alveoli ( Horvath et al, 2015 ; Ng et al, 2021 ; Kang et al, 2021 ), which are key to model lung tissue function. Those works have shown how 3D bioprinting is key to control cell deposition to mimic the alveolar barrier ( Figure 8 ).…”

“…Despite the clear advantages of these models to study cell behavior and the resemblance of the printed membranes with the ones present in real tissue, the spatial disposition was planar ( Figure 8 ), and the real 3D globular structure of the alveoli was not fully reproduced. Also, the technologies used to achieve the high resolution required to be able to print such thin features (10–20 µm) ( Horvath et al, 2015 ; Kang et al, 2021 ; Ng et al, 2021 ) present low printing speed that limits the practical application of this process to print large volumetric constructs, let alone a full organ.…”

“…Comparison of the 3D model and the 3D unstructured model used as control, and a cross sectional image of the stained barrier (scale bar 20 µm). Reproduced from ( Kang et al, 2021 ).…”

Employing Extracellular Matrix-Based Tissue Engineering Strategies for Age-Dependent Tissue Degenerations

“…(ii) Bioprinting of functional and biomimetic 3D corneal model using hydrogels and cultivated human corneal stromal keratocytes [168]. (iii) Fabrication of alveolar barrier model with all cells inkjet-printed in a layer-by-layer manner [169]. (iv) coaxial printing approach for establishing vascularized bioartificial pancreatic constructs with pancreatic insulin-secreting cells housed in core component [170].…”

Alveolus Lung-on-a-Chip Platform: A Proposal

“…As mentioned previously, one of the most remarkable challenges in lung bioengineering is the generation of a vascular network closely adjacent to the alveoli. By using 3D bioprinting technology, Kang et al (2021) fabricated a three-layered alveolar barrier with a total thickness of approximately 10 µm in a transwell insert [54]. The bottom layer consists of lung endothelial cells, the middle layer of a collagen I hydrogel containing fibroblasts and the top layer contains type I and II alveolar epithelial cells deposited by automated highresolution drop-on-demand inkjet printing (Figure 2B).…”