It is common knowledge that smoking cigarettes and breathing polluted air in congested cities are not beneficial to good health. We know that these factors can lead to severe lung diseases such as Chronic obstructive pulmonary disease (COPD), asthma or even lung cancer. What we don't know, however, is exactly how cigarette smoke and air pollutants contribute to the development of these diseases at the cellular level. This knowledge would be very valuable because it would allow us to develop treatments that intervene in the cellular changes to combat the resulting diseases.
Since lung diseases are one of the most common disease groups of all, exciting research by Baarsma et al. promises to have a major impact on the health of society. We will see that three-dimensional (3D) spheroid cell culture is a versatile tool for high-throughput studies and identifying molecular mechanisms involved in bronchial epithelial cell (patho)physiology.
Further research is needed to combat lung diseases
The results of this study show that the 3D spheroids prepared from bronchial epithelial cells are a suitable model system to study the effects of air pollutants on protein expression and tissue morphology. The spheroids are also easy to make, and researchers can use the culture for several days.
A hormone might be the key to fight lung disease
Previous studies on cells grown in two-dimensional (2D) culture have shown that the signaling molecule TGF-β1 plays a critical role in the degeneration of bronchial epithelial cells (BEC) to mesenchymal cells. This transition is termed epithelial-to-mesenchymal transition (EMT) and is observed in histological samples from patients with COPD. In addition, TGF-β1 has been shown to affect the expression of certain key proteins specific to epithelial and mesenchymal cell types. However, conditions in conventional 2D cell cultures are not close enough to conditions in the human body to draw reliable conclusions from these experiments. To address these concerns, a recent study by Baarsma et al. examined the effects of TGF-β1 and diesel exhaust particles on 3D cell culture models of bronchial epithelial cells [1].
How TGF-β1 impacts differentiation in 3D cell culture
In their study, the researchers specifically focused on measuring the expression of the key proteins tight junction protein-1, E-cadherin, collagen 1A1, and β-catenin. The former two are markers for epithelial cells, while the latter two are markers for mesenchymal tissue. Stimulation of 3D spheroid cultures of bronchial epithelial cells for 24 hours with TGF-β1 resulted in upregulation of collagen 1A1 at the mRNA and protein levels, while the concentration of E-cadherin decreased. As expected, both changes indicate a transition from epithelial to mesenchymal cells. The authors also observed a change in the shape of spheroids when exposed to TGF-β1 compared to control spheroid, which could become a valuable biomarker indicator for early phenotype changes. In general, the 3D cell culture results confirm the results of the previous 2D cell culture, with additional information on the changes in spheroid shape during exposure to TGF-β1.
Figure 1: Changes in shape for TGF-𝛽1 stimulated spheroids vs control
Diesel exhaust particles show similar effects compared to TGF-β1
When the authors examined how cell spheroids responded to exposure to DEPs, they found similar changes in their behavior. DEPs slightly increased the expression of collagen 1A1, while the β-catenin concentration significantly increased. It was also found that TGF-β1 levels produced by the cells themselves were increased. On the other hand, E-cadherin levels were decreased by DEP. The authors concluded that DEPs induce an EMT-like phenotype in human bronchial epithelial cells, which can be recapitulated in a physiologically relevant 3D cell model. DEPs likely induce the EMT phenotype via a TGF-β1-mediated pathway.
Why should you use M3D in lung cells
Listen to Dr. Glauco Souza present an introduction of how to create the 3D lung tissue model used in Baarsma and Schmidt's study of the effect of diesel pollution on lung cells.
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References
[1] Baarsma HA, Van der Veen CHTJ, Lobee D, Mones N, Oosterhout E, Cattani-Cavalieri I, Schmidt M. Epithelial 3D-spheroids as a tool to study air pollutant-induced lung pathology. SLAS Discov. 2022 Apr;27(3):185-190. doi: 10.1016/j.slasd.2022.02.001. Epub 2022 Feb 25. PMID: 35227934.