Expert consensus on an in vitro approach to assess pulmonary fibrogenic potential of aerosolized nanomaterials

Abstract

The increasing use of multi-walled carbon nanotubes (MWCNTs) in consumer products and their potential to induce adverse lung effects following inhalation has lead to much interest in better understanding the hazard associated with these nanomaterials (NMs). While the current regulatory requirement for substances of concern, such as MWCNTs, in many jurisdictions is a 90-day rodent inhalation test, the monetary, ethical, and scientific concerns associated with this test led an international expert group to convene in Washington, DC, USA, to discuss alternative approaches to evaluate the inhalation toxicity of MWCNTs. Pulmonary fibrosis was identified as a key adverse outcome linked to MWCNT exposure, and recommendations were made on the design of an in vitro assay that is predictive of the fibrotic potential of MWCNTs. While fibrosis takes weeks or months to develop in vivo, an in vitro test system may more rapidly predict fibrogenic potential by monitoring pro-fibrotic mediators (e.g., cytokines and growth factors). Therefore, the workshop discussions focused on the necessary specifications related to the development and evaluation of such an in vitro system. Recommendations were made for designing a system using lung-relevant cells co-cultured at the air–liquid interface to assess the pro-fibrogenic potential of aerosolized MWCNTs, while considering human-relevant dosimetry and NM life cycle transformations. The workshop discussions provided the fundamental design components of an air–liquid interface in vitro test system that will be subsequently expanded to the development of an alternative testing strategy to predict pulmonary toxicity and to generate data that will enable effective risk assessment of NMs.

Copper oxide nanoparticle toxicity profiling using untargeted metabolomics

“…This is based on limitations of animal models as comparisons to humans, but also of the need of in vivo studies to often use maximum tolerated doses, to remain time- and cost-effective [ 102 ]. Furthermore, with the exponential growth of nanotechnology and materials pertaining to it, new schemes and alternative testing strategies which operate within the 3Rs principle are essential, and in current times ethically prudent [ 103 , 104 ]. For example, REACH are encouraging an integrated approach to toxicological testing, where in vivo, in vitro and in silico methods are used [ 102 ].…”

Medium throughput breathing human primary cell alveolus-on-chip model

“…In vivo , the air–blood interface is an ultrathin barrier of only a few micrometers 19 , consisting of tight, semi-selective epithelial- and endothelial cell layers enveloped by the extracellular matrix (ECM) 20 , 21 , rhythmically expanding and contracting. Numerous 2D and 3D in-vitro models of the lung alveolar barrier have been reported 22 , 23 , but only few reproduced the mechanical forces created by the respiratory movements. In 2007, Takayama and colleagues mimicked those forces using liquid plugs transported by airflow to assess cellular damage 24 .…”

Toward achieving harmonization in a nanocytotoxicity assay measurement through an interlaboratory comparison study

“…Advantages of these assays are that they can be rapid, cost effective, mechanistic, used for high-throughput screening, and serve as a pathway for reducing animal testing (Nel et al, 2013;NRC, 2007;Sauer et al, 2013;Horev-Azaria et al, 2013;Clippinger et al, 2016;Landsiedel et al, 2014). However, the use of nanocytotoxicity assays has led to conflicting results from similar ENMs tested in different laboratories (Schrurs and Lison, 2012;Krug and Wick, 2011;Krug, 2014;Kaiser et al, 2011).…”