Blood-brain-barrier spheroids as an in vitro screening platform for brain-penetrating agents

Abstract

Culture-based blood–brain barrier (BBB) models are crucial tools to enable rapid screening of brain-penetrating drugs. However, reproducibility of in vitro barrier properties and permeability remain as major challenges. Here, we report that self-assembling multicellular BBB spheroids display reproducible BBB features and functions. The spheroid core is comprised mainly of astrocytes, while brain endothelial cells and pericytes encase the surface, acting as a barrier that regulates transport of molecules. The spheroid surface exhibits high expression of tight junction proteins, VEGF-dependent permeability, efflux pump activity and receptor-mediated transcytosis of angiopep-2. In contrast, the transwell co-culture system displays comparatively low levels of BBB regulatory proteins, and is unable to discriminate between the transport of angiopep-2 and a control peptide. Finally, we have utilized the BBB spheroids to screen and identify BBB-penetrant cell-penetrating peptides (CPPs). This robust in vitro BBB model could serve as a valuable next-generation platform for expediting the development of CNS therapeutics.

Focused shockwave induced blood-brain barrier opening and transfection

“…The BBB is a physical barrier made of brain capillary endothelial cells, tight junctions, basement membranes, adjoining pericytes, astrocytes and microglia. Only molecules with a mass less than 400–500 Dalton are able to cross the BBB in pharmacologically significant amounts, raising significant obstacles to treating CNS related disorders 1,2 . Currently, more than 20 million patients worldwide suffer from CNS-related disorders, and further attempts are needed to open the BBB in a non-invasive, localized, and transient manner to allow for the delivery of therapeutic agents directly into the brain 3–5 .…”

3D brain angiogenesis model to reconstitute functional human blood–brain barrier in vitro

“…Although the ultimate goal of regulating these proteins is to increase the efficacy of human CNS drug delivery, most tests have been performed using murine models (Bihorel, Camenisch, Lemaire, & Scherrmann, ; A. H. Schinkel et al, ), and human cell‐based platforms have been restricted to 2D culture assays (Gaillard et al, ; Holló et al, ; D. G. Kim & Bynoe, ) with low physiological relevance. Recently, a few 3D in vitro BBB spheroids with a functional efflux transport system have been introduced (Bergmann et al, ; C. F. Cho et al, ), but they lack a 3D perfusable vascular network, limiting their potential for drug application through the intraluminal region. Park et al () also described 2D microfluidic BBB model with a functional efflux pump.…”

“…G. Kim & Bynoe, 2016) with low physiological relevance. Recently, a few 3D in vitro BBB spheroids with a functional efflux transport system have been introduced (Bergmann et al, 2018;C. F. Cho et al, 2017), but they lack a 3D perfusable vascular network, limiting their potential for drug application through the intraluminal region.…”

Transport of trans-activator of transcription (TAT) peptide in tumour tissue model: evaluation of factors affecting the transport of TAT evidenced by flow cytometry

“…In‐vitro multicellular tumour spheroid (MCTS) models mimic true solid tumours, and therefore, intact spheroids may offer similar resistance to the penetration of molecules. The blood–brain barrier spheroids also used for screening and identification of CPPs . The complex tumour microenvironment poses resistance for the penetration of drugs into solid tumour .…”