
In vitro lung models for translational research in respiratory diseases
In vitro lung models for translational research in respiratory diseases
The COVID-19 pandemic highlighted the need for reliable lung in vitro models to efficiently respond to an emergency by accelerating research in the respiratory diseases field.
COVID-19 is a threat to human health, but infectious lung diseases are the third-leading cause of premature mortality. In fact, chronic respiratory diseases were the third leading cause of death in 2019, accounting for 4 million deaths with a prevalence of 454.6 million cases globally.
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2D cell cultures
Immortalized cell lines, such as BEAS2D, Calu-3, or IB3-1, offer an easy and fast model to answer basic research questions related to airway pathophysiology. Despite their cost-efficiency and long-term culturing, immortalized cells show genetic divergences from primary cells and do not represent the reality of the in vivo environment. 2D cultures lack cell-cell and cell-extracellular matrix (ECM) interactions as well as cellular communication between heterogenic cell types.
2D cell cultures can also be established using primary cells such as normal human bronchial (epithelial) cells (NHBCs), but problems with cell and ECM interactions remain.
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Air-liquid interface cultures
Cells are seeded on nano-porous membranes and placed on inserts into wells of a cell culture plate. The upper (apical) side of the membrane is exposed to air by removing the medium while the lower (basal) side of the cell layer remains in contact with it. A polarized and differentiated epithelial structure is formed, bringing this model closer to the physiological environment. Interestingly, mucus production and cilia movement can be observed in the pseudostratified epithelium.
Air-liquid interface cultures are established using primary airway epithelial cells or cell lines such as BEAS2B or A549. Other cell types including immune, endothelial, or fibroblasts can enrich the model. The main drawback is that it cannot be maintained in culture for long periods, complicating high-throughput screening and long-term assays.
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Precision cut lung slices (PCLS)
PCLS are thin slices of tissue taken from freshly obtained human or animal lung samples. The lungs are filled with a low melting agarose solution and then cut into slices of 200-500 μm thickness. This method preserves the native architecture, and cellular composition, maintaining cell-cell interactions and the ECM.
PCLs can be generated using healthy or diseased lungs, allowing the study of the disease pathophysiology. The main disadvantage of this model is the limited access to fresh biospecimens. Moreover, their culture period varies from 5 to 28 days, depending on the type of assay performed.
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Organoids
Organoids are 3D cultures established from adult stem cells or pluripotent stem cells using well-defined culture conditions and an ECM-rich environment. Donor-specific organoids can also be generated from progenitor cells purified from lung tissue. Their self-organization, proliferation, self-renewal capacity, and mimicking of organ functions are hallmarks of these 3D structures.
Organoids modeling bronchial epithelium have rapidly evolved, whereas those modeling alveoli have been more challenging to establish. The simpler lung organoids comprise bronchial epithelial cells embedded in a 3D ECM-based hydrogel with a complex combination of growth factors.
These models have been used to study respiratory virus infections such as respiratory syncytial virus, influenza viruses, or COVID-19.
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Lung extracellular matrix-derived hydrogels
Lung ECM-derived hydrogels are hydrophilic polymers created from the ECM of lung tissue. Lung tissue is decellularized using different methods (chemical detergents, freezing and thawing, sonication, enzymatic digestion…) and solubilized. This material is then crosslinked to generate the hydrogels. These processes do not alter hydrogel native composition and maintain the mechanical properties of the lung ECM.
These characteristics may specifically be used as a model system to analyze cell-matrix interactions and are, therefore, an excellent tool in lung regeneration medicine. Their main drawbacks are the complex decellularization protocol and their high variability among samples from different human donors.
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Lung-on-a-chip
A lung-on-a-chip (LOC) is a microfluidic device that simulates the physiological functions and mechanical properties of human lung tissue. It can be combined with physiological flow, mechanical stretching, multi-compartment co-culture, and ECM material.
Diseases like asthma and chronic obstructive pulmonary disease have been modeled using lung-on-a-chip mimicking small airways. LOCs represent the most accurate in vitro model to mimic lung structure and physiology. They promise to revolutionize the field once drawbacks such as complicated fabrication, scalability, and costs are overcome.
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BeCytes coordinates access to quality fresh lung biospecimens
Access to fresh lung biospecimens is not going to be a problem anymore when developing your in vitro lung models.
At BeCytes, we have created a platform capable of coordinating the donation of lung tissue for biomedical research purposes. We collaborate with diverse research groups by providing healthy and tumoral lung tissue to advance research related to cell isolation, organoid generation, and PCLS creation.
Besides fresh tissue, BeCytes can provide tissues in different formats including FFPE slides, curls, and blocks, OCT frozen slides, curls, and blocks, fresh frozen samples, stained slides (H&E), and RNA later.
Contact us at tissue_solutions@becytes.com. Our experts will gladly guide you in establishing a tissue-sourcing project with us!
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References
GBD 2019 Chronic Respiratory Diseases Collaborators. Global burden of chronic respiratory diseases and risk factors, 1990-2019: an update from the Global Burden of Disease Study 2019. EClinicalMedicine. 2023 May;59:101936. doi: 10.1016/j.eclinm.2023.101936.
Kühl L, Graichen P, von Daacke N, Mende A, Wygrecka M, Potaczek DP, Miethe S, Garn H. Human Lung Organoids-A Novel Experimental and Precision Medicine Approach. Cells. 2023 Aug 15;12(16):2067. doi: 10.3390/cells12162067.
Nizamoglu M, Joglekar MM, Almeida CR, Larsson Callerfelt AK, Dupin I, Guenat OT, Henrot P, van Os L, Otero J, Elowsson L, Farre R, Burgess JK. Innovative three-dimensional models for understanding mechanisms underlying lung diseases: powerful tools for translational research. Eur Respir Rev. 2023 Jul 26;32(169):230042. doi: 10.1183/16000617.0042-2023.