Improved in vitro models of the human blood-brain barrier (BBB) using endothelial cells derived from induced pluripotent stem cells (iPSCs) for testing CNS therapeutics

Abstract: Attempts to develop therapeutics for diseases of the central nervous system (CNS) have been hindered by the lack of ability of most drugs to cross the blood-brain barrier (BBB). The BBB is primarily composed of highly specialised brain microvascular endothelial cells (BMECs), pericytes and end processes of astrocytes. The BBB tightly controls the exchange of molecules and cells between the brain and the blood. Although the BBB successfully maintains the brain microenvironment, it also blocks beneficial therapeutics for diseases of the CNS. Animal models have been used to test drug candidates, but due to inter species differences and ethical and moral issues scientists have been looking for alternative models that mimic the BBB in vivo. The task of finding an alternative scalable model with optimal human BBB phenotype has been challenging. Advances in induced pluripotent stem cell (iPSC) technologies and availability of reproducible differentiation protocols1 have made this task less challenging in the recent years. In this study we present three different wild-type iPSCs differentiated into brain microvascular endothelial cells (BMECs). One of the iPSCs-derived BMECs exhibit significant barrier tightness above 6000 Ωcm2 as measured by trans-endothelial electrical resistance (TEER). Similar TEER values have been previously reported with co-culture of different cells of BBB. This study demonstrates that the barrier tightness comparable to in vivo and co-culture system can be achieved by single cell model of BMECs and the barrier tightness depends on the iPSC clone. Our in vitro models of the BBB with BMECs alone display tight junction that closely mimics the human BBB in vivo and will have many potential uses including testing of therapeutic agents aimed at the CNS and investigating BBB breakdown in disease states. We are currently testing the crossing of therapeutics for SMA through our BBB models.

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