The prolonged effects of Russian Chrysotile on an in vitro 3D human lung epithelial tissue

Asbestos fibres, including the amphiboles and the serpentine chrysotile (CHR), are classified as carcinogens by the International Agency for Research on Cancer (IARC). Today CHR “safe” mining takes place only in few countries like Russia, China, Africa, and South America, although, to mitigate the health risks associated with CHR, various international organizations, including the World Health Organization (WHO), have advocated for a complete ban on asbestos. This study investigated the effects of a Russian chrysotile (CHR) from the Yasny mine, on a 3D human lung organotypic in vitro model: the EpiAirway™ (MatTek Corp, MA, USA). This model was used to investigate the 12-days effects of CHR, physically separated in two fractions of different fibre lengths (< 5 and > 5μm) on viability, barrier integrity, and inflammation. Results were compared to the effects of crocidolite (CRO) fibres considered as a carcinogenic positive control. The results showed that tissue viability was significantly reduced for both CHR fractions and CRO at 24 h, although at 12 days the viability returned to the values of the untreated control in all samples, indicating a significant resilience of the tissue in the long term, also confirmed by the morphological analyses and the transepithelial electrical resistance (TEER) measurements. Gene expression analyses at 24 h revealed an increase in IL-1β, IL-6 and IL-8 pro-inflammatory cytokines, while ELISA tests showed a significant release of IL-1β, TNFα and IL-8 at 24 and 48h. Conversely, at 12-days of fibre exposure, only CRO and the CHR largest fraction induced an increase of IL-1β, and IL-8 gene expression compared to the untreated control. This preliminary study gives new insights into the role of fibre length in the toxicity of minerals and suggest the possibility to use the physiologically more relevant 3D lung tissue models to study the long-term effects of mineral fibres with respect to the traditional 2D lung cellular models.