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In-vitro blood-brain barrier models for drug screening and permeation studies: an overview.

ABSTRACT: The blood-brain barrier (BBB) is comprised of brain microvascular endothelial central nervous system (CNS) cells, which communicate with other CNS cells (astrocytes, pericytes) and behave according to the state of the CNS, by responding against pathological environments and modulating disease progression. The BBB plays a crucial role in maintaining homeostasis in the CNS by maintaining restricted transport of toxic or harmful molecules, transport of nutrients, and removal of metabolites from the brain. Neurological disorders, such as NeuroHIV, cerebral stroke, brain tumors, and other neurodegenerative diseases increase the permeability of the BBB. While on the other hand, semipermeable nature of BBB restricts the movement of bigger molecules i.e. drugs or proteins (>500 kDa) across it, leading to minimal bioavailability of drugs in the CNS. This poses the most significant shortcoming in the development of therapeutics for CNS neurodegenerative disorders. Although the complexity of the BBB (dynamic and adaptable barrier) affects approaches of CNS drug delivery and promotes disease progression, understanding the composition and functions of BBB provides a platform for novel innovative approaches towards drug delivery to CNS. The methodical and scientific interests in the physiology and pathology of the BBB led to the development and the advancement of numerous in vitro models of the BBB. This review discusses the fundamentals of BBB structure, permeation mechanisms, an overview of all the different in-vitro BBB models with their advantages and disadvantages, and rationale of selecting penetration prediction methods towards the critical role in the development of the CNS therapeutics.

SUBMITTER: Bagchi S

PROVIDER: S-EPMC6805046 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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In-vitro blood-brain barrier models for drug screening and permeation studies: an overview.

Bagchi Sounak S Chhibber Tanya T Lahooti Behnaz B Verma Angela A Borse Vivek V Jayant Rahul Dev RD

Drug design, development and therapy 20191018

The blood-brain barrier (BBB) is comprised of brain microvascular endothelial central nervous system (CNS) cells, which communicate with other CNS cells (astrocytes, pericytes) and behave according to the state of the CNS, by responding against pathological environments and modulating disease progression. The BBB plays a crucial role in maintaining homeostasis in the CNS by maintaining restricted transport of toxic or harmful molecules, transport of nutrients, and removal of metabolites from the ...[more]

PMID: 31695329

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Project description:Daily exposure to xenobiotics affects human health, especially the nervous system, causing neurodegenerative diseases. The nervous system is protected by tight junctions present at the blood-brain barrier (BBB), but only molecules with desirable physicochemical properties can permeate it. This is why permeation is a decisive step in avoiding unwanted brain toxicity and also in developing neuronal drugs. In silico methods are being implemented as an initial step to reduce animal testing and the time complexity of the in vitro screening process. However, most in silico methods are ligand based, and consider only the physiochemical properties of ligands. However, these ligand-based methods have their own limitations and sometimes fail to predict the BBB permeation of xenobiotics. The objective of this work was to investigate the influence of the pharmacophoric features of protein-ligand interactions on BBB permeation. For these purposes, receptor-based pharmacophore and ligand-based pharmacophore fingerprints were developed using docking and Rdkit, respectively. Then, these fingerprints were trained on classical machine-learning models and compared with classical fingerprints. Among the tested footprints, the ligand-based pharmacophore fingerprint achieved slightly better (77% accuracy) performance compared to the classical fingerprint method. In contrast, receptor-based pharmacophores did not lead to much improvement compared to classical descriptors. The performance can be further improved by considering efflux proteins such as BCRP (breast cancer resistance protein), as well as P-gp (P-glycoprotein). However, the limited data availability for other proteins regarding their pharmacophoric interactions is a bottleneck to its improvement. Nonetheless, the developed models and exploratory analysis provide a path to extend the same framework for environmental chemicals, which, like drugs, are also xenobiotics. This research can help in human health risk assessment by a priori screening for neurotoxicity-causing agents.

Project description:Efficient delivery of therapeutics across the neuroprotective blood-brain barrier (BBB) remains a formidable challenge for central nervous system drug development. High-fidelity in vitro models of the BBB could facilitate effective early screening of drug candidates targeting the brain. In this study, we developed a microfluidic BBB model that is capable of mimicking in vivo BBB characteristics for a prolonged period and allows for reliable in vitro drug permeability studies under recirculating perfusion. We derived brain microvascular endothelial cells (BMECs) from human induced pluripotent stem cells (hiPSCs) and cocultured them with rat primary astrocytes on the two sides of a porous membrane on a pumpless microfluidic platform for up to 10 days. The microfluidic system was designed based on the blood residence time in human brain tissues, allowing for medium recirculation at physiologically relevant perfusion rates with no pumps or external tubing, meanwhile minimizing wall shear stress to test whether shear stress is required for in vivo-like barrier properties in a microfluidic BBB model. This BBB-on-a-chip model achieved significant barrier integrity as evident by continuous tight junction formation and in vivo-like values of trans-endothelial electrical resistance (TEER). The TEER levels peaked above 4000 Ω · cm2 on day 3 on chip and were sustained above 2000 Ω · cm2 up to 10 days, which are the highest sustained TEER values reported in a microfluidic model. We evaluated the capacity of our microfluidic BBB model to be used for drug permeability studies using large molecules (FITC-dextrans) and model drugs (caffeine, cimetidine, and doxorubicin). Our analyses demonstrated that the permeability coefficients measured using our model were comparable to in vivo values. Our BBB-on-a-chip model closely mimics physiological BBB barrier functions and will be a valuable tool for screening of drug candidates. The residence time-based design of a microfluidic platform will enable integration with other organ modules to simulate multi-organ interactions on drug response. Biotechnol. Bioeng. 2017;114: 184-194. © 2016 Wiley Periodicals, Inc.

Project description:The strong barrier function of the blood-brain barrier (BBB) protects the central nervous system (CNS) from xenobiotic substances, while the expression of selective transporters controls the transportation of nutrients between the blood and brain. As a result, the delivery of drugs to the CNS and prediction of the ability of specific drugs to penetrate the BBB can be difficult. Although in vivo pharmacokinetic analysis using rodents is a commonly used method for predicting human BBB permeability, novel in vitro BBB models, such as Transwell models, have been developed recently. Induced pluripotent stem cells (iPSCs) have the potential to differentiate into various types of cells, and protocols for the differentiation of iPSCs to generate brain microvascular endothelial cells (BMECs) have been reported. The use of iPSCs makes it easy to scale-up iPSC-derived BMECs (iBMECs) and enables production of BBB disease models by using iPSCs from multiple donors with disease, which are advantageous properties compared with models that utilize primary BMECs (pBMECs). There has been little research on the value of iBMECs for predicting BBB permeability. This study focused on the similarity of iBMECs to pBMECs and investigated the ability of iPSC-BBB models (monoculture and coculture) to predict in vivo human BBB permeability using iBMECs. iBMECs express BMEC markers (e.g., VE-cadherin and claudin-5) and influx/efflux transporters (e.g., Glut-1, SLC7A5, CD220, P-gp, ABCG2, and MRP-1) and exhibit high barrier function (transendothelial electrical resistance, >1000 ??×?cm2) as well as similar transporter expression profiles to pBMECs. We determined that the efflux activity using P-glycoprotein (P-gp) transporter is not sufficient in iBMECs, while in drug permeability tests, iPSC-derived BBB models showed a higher correlation with in vivo human BBB permeability compared with a rat BBB model and the Caco-2 model. In a comparison between monoculture and coculture models, the coculture BBB model showed higher efflux activity for compounds with low CNS permeability (e.g., verapamil and thioridazine). In conclusion, iPSC-BBB models make it possible to predict BBB permeability, and employing coculturing can improve iPSC-BBB function.

Dataset Information

In-vitro blood-brain barrier models for drug screening and permeation studies: an overview.

Publications

In-vitro blood-brain barrier models for drug screening and permeation studies: an overview.

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