Brain Organoids: Studying Human Brain Development and Diseases in a Dish

Figure 1

Recent advances of brain organoid techniques. (1) Different region-specific brain organoids can be fused together to generate so-called “assembloids” for the investigation of interregional interactions. (2) The lack of oligodendrocytes and microglia in cortical organoids has inspired the incorporation of these cell types into brain organoids. Strategies include exposure to oligodendrocyte inducers and coculturing with microglia-like cells. (3) The addition of vasculature in brain organoids is beneficial for oxygen and nutrient delivery under long-term culturing and hence the development of vascularized brain organoids. Strategies include transplantation of brain organoids into the mouse brain, coculturing with endothelial cells, exposure to vascular endothelial growth factor (VEGF), and overexpression of human ETS variant 2 (ETV2) in brain organoids. (4) Air-liquid interface culture technique has been shown to benefit neuronal survival and axonal growth. (5) Sliced organoid culture technique is able to overcome the diffusion limit in conventional brain organoid culture, leading to more expanded cortical plate and distinct layering of neurons. (6) Microfluidic and bioengineering techniques help improve the repeatability and uniformity of brain organoid culture, providing possibilities for generating organoids with simple procedure, high reproducibility, and low cost.