Neuroscience

The blood-brain barrier (BBB), a crucial protection mechanism in the central nervous system (CNS), is a selective barrier comprised of endothelial cells. It hampers the development of therapeutic and diagnostic tools for neurological diseases due to the poor penetration of most of these agents. Rationally engineered nanoparticles (NP) can facilitate the transport of therapeutic and diagnostic agents across the BBB. However, evaluating BBB penetration by NP majorly relies on the use of expensive and time-consuming animal experiments with low throughput. In vitro BBB models composed of brain endothelial cells can be a useful tool to rapidly screen multiple NP formulations to compare their BBB penetration ability and identify optimal formulations for in vivo validation. In this protocol, we present an in vitro model of BBB developed using murine cerebral cortex endothelial cells (bEnd.3). bEnd.3 is a commercially available, easy to manipulate cell line that forms tight junctions with potent paracellular barrier property. The protocol includes culturing of bEnd.3 cells, establishment of the in vitro model, and assessing NP permeability. We believe that, due to its simplicity and consistency, this step-by-step protocol can be easily used by researchers to screen NP-based drug delivery systems for BBB penetration.

Graphic abstract:

Genetically encoded fluorescent biosensors are versatile tools for studying brain metabolism and function in live tissue. The genetic information for these biosensors can be delivered into the brain by stereotaxic injection of engineered adeno-associated viruses (AAVs), which can selectively target different cell types depending on the capsid serotype and/or the viral promoter. Here, we describe a protocol for intracranial injections of two viral vectors encoding the metabolic biosensor Peredox and the calcium biosensor RCaMP1h. When combined with 2-photon microscopy and fluorescence lifetime imaging, this protocol allows the simultaneous quantitative assessment of changes in the cytosolic NADH/NAD⁺ ratio and the intracellular Ca²⁺ levels in individual dentate granule cells from acute hippocampal slices.

Graphic abstract:

Workflow diagram for biosensor expression in the mouse hippocampus using intracranial injections of adeno-associated viruses.

ATP13A2/PARK9 is a late endo-/lysosomal P5B transport ATPase that is associated with several neurodegenerative disorders. We recently characterized ATP13A2 as a lysosomal polyamine exporter, which sheds light on the molecular identity of the unknown mammalian polyamine transport system. Here, we describe step by step a protocol to measure radiolabeled polyamine transport in reconstituted vesicles from yeast cells overexpressing human ATP13A2. This protocol was developed as part of our recent publication (van Veen et al., 2020) and will be useful for characterizing the transport function of other putative polyamine transporters, such as isoforms of the P5B transport ATPases.