Prediction of Drug Permeability Using In Vitro Blood–Brain Barrier Models with Human Induced Pluripotent Stem Cell-Derived Brain Microvascular Endothelial Cells

Abstract

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 Ω × 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.

Commentary on human pluripotent stem cell-based blood–brain barrier models

“…For instance, permeability of drugs and nutrients across a monolayer of hPSC-derived BMEC-like cells correlated with in vivo rodent brain transport rates [1], and subsequently, PET radioligand transport across BMEC-like cells correlated with human BBB permeability [16]. It has also been demonstrated that these cells can be used to compare the relative in vitro BBB permeability of known drugs, to evaluate the permeability and efflux profile of experimental drugs, and to explore the mechanisms of nutrient transport [1,[11][12][13][14][15][16]. hPSCderived models can also be used to compare transport of antibodies across the BBB to identify antibody-and species-dependent effects on trans-BBB transport [7,19] and identify new antibodies capable of binding the human BBB [31].…”

“…We defined this cell type as hPSC-derived BMECs. The resultant cells have proven useful for examining interactions between cells of the neurovascular unit [1][2][3][4][5][6][7][8][9][10], evaluating experimental drug permeability at the BBB [1,[11][12][13][14][15][16], and modeling human genetic disease using hiPSCs derived from patient sources [9,10,13], among other applications.…”

Recent advances in human iPSC-derived models of the blood–brain barrier

“…Due to the species-specific differences in transporter and efflux pump expression, human iPSC-based BBB models are an attractive platform to test drug permeability. These models more accurately predict human BBB permeability compared to non-human BBB models [69] and hold great promise in providing a high-throughput platform for predicting human CNS drug permeabilities and circumventing the need for animal-based testing [70]. Early iPSC-derived BBB models highlighted the ability of iBMECs to correlate well with in vivo drug permeability using transwell systems [12,71] and subsequent studies have expanded permeability testing to microfluidic platforms under fluid flow that more closely mimic in vivo conditions [19,31,64].…”

Modeling blood–brain barrier pathology in cerebrovascular disease in vitro: current and future paradigms

“…by increasing flow through the collateral circulation ‘bypassing’ the occluded vessel). However, within areas of injury, there can be vasoconstriction that can cause capillary occlusion even after reperfusion (no-reflow phenomenon) regulated by pericytes [ 147 ]. In addition, there are cytotoxic effects on BECs with mitochondrial dysfunction and altered ion channel and transporter activity (e.g.…”