Directing Fates of Human Brain Stem-Cells in 2D and Organoid Cultures: A Close Know-How of Your Lead Actors

Early regional neural stem cells (NSCs) are founder (starting) populations for the derivation of distinct brain regions. However, information on the signals that dictate specification, self-renewal and differentiation of starting NSCs is still limited.

The advent of organoids has immensely increased ability to generate regional 3D structures from PSCs. However, organoids are highly heterogeneous, arguing for compromised identity of organoid starting cells.

We aim to increase the identity and purity of starting NSCs, the lead actors of brain devolvement, with the goal of harnessing the full potential of such cells for generating distinct region-specific organoids for regenerative medicine.

Focused on human cortex, we developed a method to generate early homogeneous cortical NSCs. Cortical organoids made from such cells by this method exhibit enhanced and lasting cortical NSC identity, robust cortical cytoarchitecture, increased cortical cellular diversity output and meaningful phenotypes in a disease model.

In addition, we identified micro-RNAs transiently expressed only in the early NSC stages and show their ability to converting early cortical organoids into choroid plexus organoids (the basis for BBB) or hippocampus organoids. We also identified a novel early stage-specific surface protein that can prospectively isolate NSC subpopulations and enrich for distinct cortical regions early following exit from pluripotency.

These findings show how knowledge on starting NSCs we gathered through the years can be utilized to harness the full potential of brain development in the dish - towards more advanced and accurate use of such cells for disease modeling, cell-based therapy and the discovery of new drugs.