First observations of spontaneous bursting in human hNT neurons with a customised neural chip platform

In 2004, Gortz et al performed the first and only electrical measurements of human embryonal carcinoma NTera2/cl.D1 (NT2/hNT) neurons in vitro. His conclusions shaped our perspective about the electrical characteristics of this cell type and, since burst-like behaviour of the neurons was not observed as occurs in primary cultures, he cautioned how one should be careful in using such cells for human therapeutic approaches. Since then, several authors have demonstrated chemically that hNT neurons express ubiquitous neuronal markers with their chemical expression being directly compared to that of human primaries and how they are a valid alternative to them, leading to their successful use for cell transplantation in stroke therapy. However, whilst the scientific community had identified the similarity of chemical expression of hNTs to primaries there still remained an 'odd piece in the puzzle' as the cells' electrical characteristics appeared incongruent, not matching the burst-like behaviour typically observed in primary neuron cultures. In this article, we re-examine the electrical characteristics of hNT neurons with a customised, low-noise recording system. With this recording system, we observe for the first time that hNT neurons do indeed exhibit burst-like behaviour, providing an exhaustive quantification of the bursts which we relate to strong network formation and hence update and revise the original work. The significance of this work is that it rebalances the scientific community's perspective on the electrical characteristics of hNT neurons. This work provides the final electrical piece to the hNT neuron's profile aligning its narrative to be complementary to the hNT neuron's chemical expression and similar to primary neurons. For the first time, we can now completely consider, both electrically and chemically, the hNT neuron as a valid alternative to primary neurons.