Aim. We are developing in vitro – neurotoxicity models to evaluate the possible effects of chemicals and drugs to the cells of the nervous system. The nervous system is an important target of many chemicals, but at the moment there are no accepted models in the regulatory guidelines to test neurotoxicity in vitro.

Principles. Neural cell cultures are exposed to test compounds and the reactions of the cells are followed by using basic cytotoxicity methods as well as neuron-specific methods. In the test scheme, cell lines, primary cells and cells differentiated from stem cells of human origin will be used when possible. Neuronal cells and glial cells are tested separately and in coculture, because all neurotoxic compounds are not toxic to neurons unless they are first metabolized by glial cells.

The length of neurites and cell movements are possible sensitive markers of early neurotoxicity. Those will be evaluated with machine vision technology in use in FICAM. Other specific neuronal markers include changes in synaptic functions and in electrical signaling. Alterations in cell membrane potentials can be evaluated either with fluorescent electrosensitive markers or by culturing the cells on multielectrode arrays (MEA). In MEA constellation, several stimulation/measurement points printed close by each other allow following of the propagation/inhibition of signals in the cell network

A functional neural cell network will be developed for the tests. The goal is to preserve the electrical capabilities and functional synaptic contacts also in culture conditions. After different stimuli, reactions of single cells, synaptic contacts and electrical responses will be evaluated. In vitro results will be validated compared to in vivo results. Validation will allow the use of the neurotoxicity model developed in regulatory guidelines. Measuring of electrical signals is important in studies of the normal function (e.g. memory) and dysfunction (e.g. epilepsy, memory disorders) of the nervous system as well as in drug development. In vitro neurotoxicity model can be standardized more easily and would be simpler than present in vivo models.

Status. Development work for all above sections is ongoing.

Blood-brain barrier model

Aim: The blood-brain barrier (BBB) consists of brain capillary endothelial cells. It has an essential role in protecting central nervous system from harmful substances by restricting their passage from blood to brain. The in vitro BBB model is important when the passage of molecules to brain tissue needs to be evaluated, for example, in the development of new drugs. Chemicals may also cause direct effects on the integrity of BBB, which can be assessed. In addition, by using neural target cells in the in vitro BBB model, it can be used in studies of potential neurotoxicity of chemicals in brain.

Principle: We are developing a model that consists of human endothelial cells as a barrier and human neural cells as target cells for neurotoxicity studies.

Status: The development of the model is going on.

Figure. A schematic illustration of a blood-brain barrier model.