Anesthesia-on-chip: Modelling the impact of fetal anesthesia on neural development

An increasing number of surgical procedures are performed on the fetus before birth. These include complex surgery for spina bifida, performed locally at Great Ormond Street Hospital. For these procedures, the mother must receive a general anesthetic.

Many of the anesthetic agents used will cross the placenta and affect the fetus. The impact of anesthetics, analgesics and pre-medication agents on fetal brain development are largely unknown, and difficult to investigate directly in patients who may have co-morbidities delaying their developmental milestones. Animal studies suggest some anesthetic agents, such as the induction agent propofol, are neurotoxic.

Others agents, such as the sedative dexmedetomidine, may be neuroprotective. This application aims to replace animal use with human induced pluripotent stem cell (iPSC)-derived cortical neurons in the study of anesthesia, particularly during the fetal period.

We have now developed an "Anesthesia-on-chip" protocol in which we can visualize growing neural progenitor cells in culture and diminish their excitability with anesthetics. Several complex models of human "mini brain" organoids have been reported, but the inherent variability in those systems, low throughput, and high cost limit their utility.

Instead, we use a well-established 2D neuronal differentiation system which enables cells to be dynamically analysed and quantitatively compared between treatment groups. This method is ideally suited for a PhD studentship. It would be broadly generalizable as an animal-replacing technology likely to be rapidly adopted by the field due to the limited translatability of anesthesia research in animals.

Our unpublished data shows that neurons survive in vitro anesthetic exposure and continue to grow, but their differentiation is impaired. This corroborates concerns that fetal anesthesia may be more neurotoxic that post-natal anesthesia due to the abundance of progenitor cells during fetal growth, and is expected to stimulate a rapid increase in animal experimentation if fully human alternatives are not made available within the next few years. In order to validate and apply this platform, we propose to:

Compare expression of receptors for common anesthetics during human neuron differentiation from pluripotent stem cells, and in human fetal brain tissue at different stages.

Define the immediate effects of anesthesia-on-chip protocols using human stem cell-derived neurons to establish susceptibility to anesthesia at different stages of differentiation.

Assess in vitro neurotoxicity in cultures anesthetized at different time points during differentiation, treated with clinically-relevant combinations of agents such as propofol and dexmedetomidine, or anesthetized repeatedly.