Background and Challenges

Neurodevelopmental toxicants are a serious risk for society, making regulatory testing for chemicals indispensable. Testing according to the current regulatory guidelines employing animal experiments is time- and cost intensive. For a more resource-effective way of developmental neurotoxicity (DNT) testing our laboratory established the human ‘Neurosphere Assay’, which is based on three dimensional (3D) neural progenitor cell (NPC) clusters. This system is able to mimic basic processes of brain development: Proliferation, differentiation, migration and apoptosis. Upon withdrawal of growth factors and in presence of an extracellular matrix (ECM), NPCs start to radially migrate out of the sphere-core and differentiate into astrocytes, neurons and oligodendrocytes. By immunostaining different cell types can be quantified and their morphology can be studied using high content image analyses (HCA).

However, safety and efficacy testing of chemicals with 3D neurospheres by employing HCA requires advanced scanning and evaluation processes due to characteristic features of the cultures:

  • A variable cell density within the migration area
  • A 3D sphere core, leading to unfocused images
  • A heterogeneous cell population of neurons and glia cells
Radial Migration Distance and Density Distribution
The radial migration distance is defined as the average distance between the rim of the sphere core and the furthest migrated cells (indicated as yellow arrows). A density distribution describes the ratio between a certain cell type e.g. neurons (green dots) and all present cell types at a certain distance from the sphere-core (indicated as rings, which subdivided the migration area into ten areas with equal width but different distances from the sphere-core).

To tackle these challenges we developed a software called ‘Omnisphero’ to assess  quantification of neuronal differentiation, neurite outgrow and sphere specific endpoints such as radial migration, and distance-dependent density distributions.