Differential toxicity of an organic PM2.5 extract to human lung cells cultured in three dimensions (3D) and monolayers

Several epidemiological studies have associated PM2.5 (particulate matter, aerodynamic diameter 2.5 mu m) exposure with an increase in morbidity and mortality attributed to cardiopulmonary diseases. Based upon these observations and the growing effort to replace the use of animals in research, in vitro A549 cells cultured in three dimensions (3D), an alternative method to the use of animals, as well as monolayers were investigated to examine whether organic PM2.5 extract induced equivalent cytotoxic changes in vitro as compared to in vivo. PM2.5 was collected on Brazil Avenue, Rio de Janeiro, Brazil, from November 2010 to May 2011, except March, and analyzed for the ability to induce cytotoxicity in A549 cells using various established assays. Samples collected in all months significantly decreased viability of A549 cells using both types of cell death assays, and those collected in November showed lower cytotoxicity. It is worthwhile noting that for samples collected in all months except for April, PM2.5 induced greater toxicity in cells grown in monolayers than in 3D. Data demonstrated that cell behavior varied based upon type of culture system employed. Since the 3D cell culture mimics the architecture of in vivo tissue to a greater extent than monolayers, it is suggested that data from 3D studies resemble more closely human exposure conditions and thus may provide more reliable findings to be utilized in risk assessment following PM exposure than results obtained in traditional culture system.