Embedded Printing of Human Respiratory Model with Air-Liquid Interface for COVID-19 Research

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Project Summary The overarching goal of this research is to fabricate an in vitro three-dimensional (3D) human respiratory model with an air-liquid interface (ALI), which can serve as a platform for COVID-19 related biomedical investigations. A recent COVID-19 outbreak, which is due to the infection of a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), results in more than 100 million confirmed cases and about 2.3 million deaths with numbers increasing everyday globally. For COVID-19 related research, there remains an urgent need for a 3D fully heterogeneous, cellular respiratory model, which can enhance our understanding of how SARS-CoV-2 induces lung injury and facilitate the development of new treatments as complementary to animal models and clinical patients. We therefore propose to develop such a human respiratory model, which 1) expresses angiotensin-converting enzyme 2 (ACE2) protein and transmembrane protease serine type 2 (TMPRSS2) that allow viral entry to study the SARS-CoV-2 infection process, and 2) has the diffusional permeability between the airway and primary fluid channel to enable the mass transport across ALI, permitting the screening of clinically proven drugs for COVID-19 use. We hypothesize that an in vitro human respiratory model can be realized by embedded printing and further developing a perfusable construct in a yield-stress matrix bath containing primary human stromal, endothelial, and fibroblast cells. Accordingly, two specific aims are proposed as follows: Aim 1: Embedded printing and perfusion of a 3D in vitro human respiratory model in a stromal cell-based cross-linkable yield-stress matrix bath. Aim 2: Characterization of the human respiratory model via detection of ACE2 receptor and TMPRSS2 protease in the airway epithelium and determination of the diffusional permeability of ALI. For the first time, a gelatin microgels and gelatin solution-based cross-linkable yield-stress cellular composite matrix bath will be innovated for embedded printing of perfusable tissue constructs in it, enabling human respiratory model fabrication. This model development study will result in an in vitro 3D human respiratory model with ALI and cellular stroma by utilizing the novel cross-linkable yield-stress cellular matrix bath for embedded printing, and no other models with this physiological complexity exist. Such a human respiratory model will provide a versatile in vitro platform for studying the COVID-19 pandemic-related infection process and screening related drugs.