Development of 3D Cerebral Aggregates in the Brain Ventricles of Adult Mice

The cerebral organoids are three-dimensional cell cultures formed from brain-specific cell types arising from embryonic or pluripotent stem cells. Organoids provide an opportunity to study the early stages of brain development and diseases of the central nervous system. However, the modeling of organoids is associated with a number of unsolved problems. Organoid production techniques involve a complex cell culture process that requires special media, growth factors, and often the use of a bioreactor. Even under standardized conditions, structures of different morphology are formed: from disorganized cell aggregates to structured minibrains, which are selected for study. For natural reasons, organoids grown in vitro do not have a blood supply, which limits their development. We tried to obtain cerebral aggregates similar to organoids in an in vivo model, where vascular growth and tissue blood supply are provided, for which we transplanted a cell suspension from the mouse embryonic neocortex into the lateral ventricles of the brain of adult mice. Therefore, the medium for cultivation was the cerebrospinal fluid, and the lateral ventricles of the brain, where it circulates, served as a bioreactor. The results showed that the neocortex from E14.5 is a suitable source of stem/progenitor cells that self-assemble into three-dimensional aggregates and vascularized in vivo. The aggregates consisted of a central layer of mature neurons, the marginal zone free of cells and a glia limitans, which resembled cerebral organoids. Thus, the lateral ventricles of the adult mouse brain can be used to obtain vascularized cell aggregates resembling cerebral organoids.