Brain Organoids

Preclinical animal models of neurological diseases pose limitations primarily because of species differences in developmental mechanisms, tissue architecture, cell types and gene expression. Additionally, it is challenging to model unique human cognitive and behavioral disorders in animal models.A viable alternative to study brain development and diseases is the use of brain organoids; miniature brain-like 3D constructs. Human brain organoids have been shown to better mimic brain physiology and function, so they are better models to study neurological diseases and the efficacy of therapies. One challenge of using brain organoids is continued maintenance that requires oxygen and nutrient delivery. Static cultures tend to result in poor gas exchange and waste buildup, leading to cell death in organoids. Organoids grown under perfusion conditions show higher cell viability over a longer period compared to those cultured in static systems.2

LiveBox 1
 
Higher number of devices are developed to culture organoids in a perfused system. One such example is the LiveBox systems from IVTech. LiveBox 1 provides a platform to grow 3D cultures including brain organoids and comprises of a transparent chamber for inter-connected dynamic cell cultures. This device has a flow inlet and outlet for the perfusion of cell culture media [Figure 1]. The clamp system enables both static and dynamic conditions (with a flow rate up to 1 mL/min). The chamber has a removable transparent cover that allows live imaging during static/dynamic culture, post-culture imaging of staining, and other downstream analyses. LiveBox1 enables the growth of large organoids and facilitates in experiment imaging over a long time period. Thus, it is an efficient platform for modeling neurological diseases and assessing safety and efficacy of drugs.

 
Figure 1: Single flow configuration tangential to the cells.

Blood-Brain Barrier (BBB) in LiveBox 2
 
The blood-brain barrier (BBB) is a complex vasculature system comprised of various cell types. It serves as an important filter to regulate molecular trafficking between the blood and brain and provides a barrier function with tight junctions between the endothelial cells, reinforced by glial podocytes and astrocytes. The progression of various CNS diseases such as multiple sclerosis and Alzheimer’s disease have been associated with the disruption of the BBB.
Most therapeutics are unable to treat central nervous system diseases because they cannot cross the BBB. Therefore, in vitro modeling of blood-brain barrier (BBB) are essential for understanding BBB disruption, and to screen the brain-penetrating capabilities of therapies. Given the complexity of the BBB, in vitro 2D monolayer cultures do not recapitulate the dynamic structure of the BBB whereas complex 3D models cultured in perfusion conditions more accurately represent the native BBB environment. The LiveBox 2 from IV-Tech technology is a novel system for modeling BBB [Figure 2].

 
Figure 2: LiveBox 2 [3]
 


It is a two-chamber microfluidics system that incorporates perfusion to simulates the blood flow. The two chambers are separated by a removable and porous membrane that can be seeded with endothelial cells [Figure 3]. Co-culture of endothelial cells with astrocytes and pericytes will enhance the BBB barrier function. This device allows live and post-culture imaging of the 3D culture including staining procedures for tight junction biomarkers, without compromising the cell architecture. It also can be connected to other cell culture systems to mimic multi-organ simulation. Electrodes can be included to measure the transendothelial electrical resistance (TEER) as an endpoint for the barrier function.

 
Figure 3: LiveBox2 with the two chambers (apical and badal chambers). The system incorporates perfusion to simulate blood flow



References
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  1. Di Lullo, E., & Kriegstein, A. R. (2017). The use of brain organoids to investigate neural development and disease. Nature reviews. Neuroscience, 18(10), 573–584. https://doi.org/10.1038/nrn.2017.107
  2. Wang, Y., Wang, Li., Guo, Y., Zhu, Y., et al. (2018). Engineering stem cell-derived 3D brain organoids in a perfusable organ-on-a-chip system. The Royal Society of Chemistry, 8(3), 1677-1685.
  3. www.tnx.it - Siti Internet Poggibonsi - Siena - Toscana - Italia. “Products.” IVTech, www.ivtech.it/Products/.