Micromass Embryotoxicity Assay

The micromass test is based on detecting the ability of toxic chemical compounds to inhibit the formation of cell foci. Embryonic limb mesenchyme or Central Nervous System (CNS) cells (usually mid-brain, which form foci of neurons) from chicken, mouse or rat can be used for the micromass test.
The primary culture of limb bud cells of mammalian origin reproduces cartilage histogenesis, a fundamental step in the morphogenesis of the skeleton. When cultured at high cell densities, the cells differentiate to form foci of chondrocytes and neurones, respectively. Various functions, including cell proliferation, cell differentiation, cell to cell communication and cell to extracellular matrix interactions are implicated in this developmental process and the differentiation in vitro and in vivo is very similar both in terms of cell morphology and the specific macromolecules synthesised. The inhibition of mammalian embryogenesis and cell differentiation in vitro is an indication of a potential risk of teratogenicity in vivo. Thus, these cultures were used as a short-term assay system for the prediction of an embryotoxic potential in presence or in absence of a metabolic activating system.