oa Automated Image Analysis of the Human Micronucleus Cytome Assay for High Throughput Biomonitoring Studies: IMSTAR system

Analysis of micronuclei (MN) is widely used for human biomonitoring or in vitro/in vivo genotoxicity testing, and provides a sensitive and relatively easy method to assess genetic damage (Kirsch-Volders et al, 2011). The fact that baseline MN frequencies in cytokinesis-blocked (CB) lymphocytes have been shown to be a predictive biomarker for cancer risk strengthens the importance of the CBMN assay as a reliable method for human biomonitoring of early genetic effects. We showed (Kirsch-Volders and Fenech, 2001) that scoring MN frequencies in binucleated and mononucleated cells enhances the predictive capacity of the assay. However, automation of MN analysis is needed for quicker, more reliable detection while minimizing subjective judgment and scoring, and to allow multi-center cohort analysis for biomonitoring studies. Within the framework of NewGeneris, an EU project, we developed an automated image analysis system for scoring MN in human lymphocytes in collaboration with IMSTAR. The IMSTAR system is based on specific algorithms starting from the cell as a detection unit. The whole detection and scoring process are separated into two distinct steps: in the first step, the cells and nuclei are detected; then, in the second step, the MN are searched for in the detected cells. The fact that our designed software protocol started from the cell as a detection unit, and hence the identification of mono-, bi- and polynucleated cells, and MN in these different sub-populations of cells, allows the assessment of cell proliferation through nuclearity index, which is important for an efficient assessment of mitogen response and cytostasis in human biomonitoring as these are indicative of immune function and cytotoxicity (Decordier et al, 2011). Additional requirements that should be fulfilled for development of an automated MN analysis system include: a) The system should be applicable to the CBMN methodology and accurately distinguish mono, bi- and polynucleated cells; b) Well defined scoring criteria for cell type and MN (eg, Fenech et al, 2003); c) Experienced cytologists to score MN according to the HUMN criteria; d) A standardized slide preparation protocol to obtain uniformity in cell size, cell density, and reproducibility (Decordier et al, 2009); e) Validation of the automated versus manual scoring (Decordier et al, 2009, 2011). This methodology was successfully applied to study different mother-child cohorts within the EU-project NewGeneris (Vande Loock et al, 2011). Funded by the EU Integrated Project NewGeneris, (Contract No FOOD-CT-2005-016320). NewGeneris is the acronym of ‘Newborns and Genotoxic Exposure Risks’ and ECNIS stands for ‘Environmental Cancer Risk, Nutrition and Individual Susceptibility’ (FOOD-CT-2005-513943)