The In vitro Mammalian Cell Micronucleus Test (MN test, OECD TG 487) is a key component of most regulatory genotoxicity testing strategies. It is used to assess chromosomal damage in mammalian cells and is internationally applied in regulatory settings to detect clastogenic and aneugenic effects of chemicals, pharmaceutical substances, plant protection products, medical devices, and nanomaterials.

The OECD 487 micronucleus test is considered one of the most important in vitro genotoxicity assays within international regulatory frameworks such as REACH, OECD, ICH, and EFSA.

Differentiation Between Clastogenic and Aneugenic Mechanisms

To further investigate the mode of action, centromere analysis using fluorescence in situ hybridization (FISH) can be performed. FISH analysis enables differentiation between:

·clastogenic mechanisms

·aneugenic mechanisms

This differentiation is particularly relevant under REACH when increased micronucleus formation is observed in the micronucleus assay.

OECD 487 for Nanomaterials

Specific adaptations of the OECD 487 study design are required for the testing of nanomaterials. Scientifically reliable results require that:

·cellular uptake of the nanomaterial is demonstrated

·effective exposure, ideally in the form of a stable dispersion, is confirmed

Our experts support you in developing appropriate testing strategies for nanomaterials in accordance with current regulatory requirements.

Principle of the In Vitro Micronucleus Test

The OECD 487 assay evaluates the formation of micronuclei in interphase cells. Micronuclei may arise from:

· acentric chromosome fragments lacking a centromere, or

·whole chromosomes that fail to segregate correctly during anaphase

The assay assesses the potential of a substance to induce genetic damage in cells that have undergone at least one cell division cycle.

Study Scope According to OECD TG 487

In the initial experiment, a short-term exposure is performed:

· with metabolic activation (S9)

· without metabolic activation

In cases of negative or equivocal results, a second modified experiment is conducted:

·prolonged exposure without S9, or

·short-term exposure with increased S9 concentration

Formulation analysis can be integrated into the study design.

Test System

TK6 CRL-8015™ (human lymphoblastoid cell line derived from spleen tissue)

Endpoints and Evaluation

The genotoxic potential of a substance is determined by comparing the micronucleus rate of the individual test item concentrations to that of a negative control (solvent only). In case of a positive result (genotoxic) a subsequent FISH analysis can then be used to distinguish between the mode of actions involved (clastogenic or aneugenic).

Your CRO for OECD 487 Studies

Our OECD 487 testing services support international regulatory programs for:

· chemicals

· pharmaceuticals

· agrochemicals

· medical devices

·nanomaterials

We develop customized study concepts according to current OECD, ICH, EFSA, and REACH requirements.

Contact Our Genotoxicity Experts

Do you require an OECD 487 study and support with your regulatory strategy?

Get in touch today to discuss your OECD 487 testing needs. Our experts are ready to support your project from study design to final report delivery.

FAQ – OECD 487 In Vitro Micronucleus Test

What is the OECD 487 Micronucleus Test?

The OECD 487 in vitro micronucleus test, also referred to as the micronucleus assay, is a regulatory accepted genotoxicity test used to evaluate chromosomal damage in mammalian cells. The assay detects both clastogenic effects (chromosome breakage) and aneugenic effects (changes in chromosome number).

What is OECD TG 487 used for?

OECD TG 487 is used to assess the genotoxic potential of chemicals, pharmaceutical substances, medical devices, plant protection products, and nanomaterials. The assay is part of international regulatory requirements, including REACH, OECD, EFSA, and ICH guidelines.

What is the difference between clastogenic and aneugenic effects?

Clastogenic effects cause structural chromosomal damage such as chromosome breaks. Aneugenic effects lead to changes in chromosome number due to chromosome missegregation during cell division.

Which cells are used in the OECD 487 assay?

At LAUS, the human lymphoblastoid cell line TK6 CRL-8015™ is used. This cell line is internationally established and suitable for regulatory genotoxicity testing.

When is FISH analysis performed?

FISH analysis is typically conducted following a positive micronucleus test result to differentiate between clastogenic and aneugenic mechanisms. This may be particularly relevant for REACH evaluations.

Can OECD 487 be used for nanomaterials?

Yes. However, specific adaptations of the study design are necessary for nanomaterials. These include demonstrating cellular uptake, ensuring stable dispersion, and confirming effective exposure.

Is the OECD 487 assay performed with metabolic activation?

Yes. The assay is generally conducted both with and without metabolic activation (S9 mix) to reflect different metabolic conditions.

Which regulatory requirements does OECD 487 support?

The OECD 487 assay supports regulatory requirements including:

·REACH

·OECD

· ICH

·EFSA

· FDA

· EMA