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Context Matters: Using an Organotypic Airway Model to Assess the Response to Inhaled Toxicants
Citation:
McNabb, N., H. Smith, E. Vitucci, AND S. McCullough. Context Matters: Using an Organotypic Airway Model to Assess the Response to Inhaled Toxicants. Gordon Research Conference on Cellular and Molecular Mechanisms of Toxicity, Andover, NH, August 12 - 18, 2017.
Impact/Purpose:
This work suggests that the incorporation of additional, relevant cell types into in vitro toxicity studies may be more informative than the current standard two-dimensional monocultures that are used.
Description:
Exposure to particulate air pollution is associated with increased morbidity and mortality from pulmonary and cardiovascular diseases worldwide. Diesel exhaust particles (DEP) are a significant contributor to particulate air pollution and are known to induce pulmonary oxidative stress and pro-inflammatory responses in both in vivo studies and in vitro models. Many in vitro toxicology studies of DEP exposure have focused only on bronchial epithelial cells grown in two-dimensional cultures on plastic substrata; however, the cellular microenvironment in vivo is much more complex involving additional cell types such as fibroblasts in the stroma. Intercellular communication is an important aspect of response to environmental stimulants, and it has been shown that fibroblasts in the lung influence epithelial cell growth, differentiation, and gene expression. As the barrier between the body and environment, airway epithelial cells are the first point of contact for all inhaled toxicants, including DEP. We hypothesized that the incorporation of fibroblasts into an organotypic model of the airway epithelium would alter the response of airway epithelial cells to DEP and provide an opportunity to examine the effects of DEP exposure on cell types beyond the epithelium. To test this hypothesis, we developed a transwell-based organotypic airway model where bronchial epithelial cells are grown on a collagen matrix on the apical side of a porous membrane, and lung fibroblasts are grown in the basolateral compartment. We conducted exposures by adding DEP to the confluent epithelial cell layer and assayed changes in the expression of interleukin-8 (IL-8) and heme oxygenase 1 (HMOX1), markers of pro-inflammatory and oxidative stress, respectively, in both cell types following 2, 4, 6, and 24 hours of exposure. Exposure of epithelial cells in the organotypic model resulted in a 25- and 5-fold induction of HMOX1 and IL-8, respectively, which was greater than the 15- and 4-fold inductions observed in matched exposures lacking fibroblasts. Further, despite a lack of direct exposure, HMOX1 and IL-8 were induced by 3,500- and 2.5-fold, respectively, in fibroblasts in the basolateral compartment of the exposed organotypic cultures. Our findings indicate that toxic exposures can have effects outside of the directly exposed cells, suggesting that this organotypic airway model can elucidate aspects of exposure response that are not well-addressed by traditional monoculture models. Utilizing this model in further studies could facilitate understanding the role that fibroblasts play in both local and systemic adverse health effects of toxic exposures.