ICDT

Modeling human brain development and disease in vitro represents a huge methodological challenge with very impactful ends.  Brain organoids are self-organizing 3D cultures derived from human induced pluripotent stem cells, differentiated by guided (addition of small molecules) or unguided methods, comprising multiple cell types arranged in architectural and functional patterns reminiscent of particular regions of the brain (Kelava and Lancaster 2016). Assembloids can be generated by fusing guided organoids of different regions (Pașca et al. 2022) Developmental processes such as radial glia asymmetric divisions, nuclear translocation, interneuron migration, axon growth, synaptogenesis, or neural networks organization can be observed to certain extents in organoids and assembloids (Chiaradia and Lancaster 2020; Meng et al. 2023). Disease modeling represents a large field for brain organoid applications, which have been shown not to have any transcriptional bias towards disease-related genes (Tanaka et al. 2020). Studies using patient-derived organoids have modeled pathologies such as microcephaly, autism spectrum disorders, Alzheimer’s disease or schizophrenia, and manipulation such as Zika virus infection or gene loss-of-function simulation based on CRISPR-Cas9 technology have also used to model pathogenetic mechanisms in neurologic diseases (Chiaradia and Lancaster 2020).

One of the leading groups in the field is the laboratory lead by Professor Sergiu Pașca at Stanford University, California, United States. They developed innovative and reliable methods to generate and analyze guided human neural organoids and assembloids and used them to study diseases such as autism spectrum disorders. Every year, they generously organize the Stanford Brain Organogenesis Workshop, where they select 24 participants out of hundreds of applicants and provide free of charge training and accommodation for one week.

In April 2024, Raluca Pașcalău, PhD student in Dr. Badea’s laboratory, participated at this workshop based on her interest for human brain and retina development. The activities consisted of theoretical lectures and hands-on sessions on human brain organogenesis, induced pluripotent stem cell culture maintenance, organoid culture, histology, microscopy, functional assays such as electrophysiology and Calcium imaging as well as CRISPER genome editing and transcriptomics. The subjects were treated from a conceptual perspective first, and then, postdocs from the Pașca lab gave practical examples on technical aspects from their own experience and presented some of their current projects. The Workshop also covered topics related to ethics and grant writing on human neural organoid research. Participants were divided in small groups and asked to create grant proposals taking advantage of their previous experience and the newly acquired knowledge. Her group proposed the creation of a human hypothalamus organoid for the study of entrainable circadian rhythms which was met with enthusiasm by the organizers. 

The Workshop was an enriching experience not only from a scientific point of view, but also through the opportunity to meet fellow research trainees with similar interests but different backgrounds, coming from numerous parts of the world such as Japan, Korea, Israel, Saudi Arabia, Serbia, Croatia, Turkey and various places in the United States. 

For the Transilvania Neurogenetics Laboratory, the knowledge gained at the Workshop opens up the field of organoid development and characterization, which is a resourceful alternative approach to neuronal development, given the restricted availability of human fetal tissues. By combining an understanding of in utero retinal ganglion cells development in mice and humans with the experimental versatility of the retina/brain organoids, we may accelerate our progress in understanding how their axons grow, and eventually how they could be regrown in pathological states.