Benchmarking in vitro tissue-engineered blood–brain barrier models

Abstract

The blood–brain barrier (BBB) plays a key role in regulating transport into and out of the brain. With increasing interest in the role of the BBB in health and disease, there have been significant advances in the development of in vitro models. The value of these models to the research community is critically dependent on recapitulating characteristics of the BBB in humans or animal models. However, benchmarking in vitro models is surprisingly difficult since much of our knowledge of the structure and function of the BBB comes from in vitro studies. Here we describe a set of parameters that we consider a starting point for benchmarking and validation. These parameters are associated with structure (ultrastructure, wall shear stress, geometry), microenvironment (basement membrane and extracellular matrix), barrier function (transendothelial electrical resistance, permeability, efflux transport), cell function (expression of BBB markers, turnover), and co-culture with other cell types (astrocytes and pericytes). In suggesting benchmarks, we rely primarily on imaging or direct measurements in humans and animal models.

Establishment of an in Vitro Human Blood-Brain Barrier Model Derived from Induced Pluripotent Stem Cells and Comparison to a Porcine Cell-Based System

“…As reported in Figure 5A, hiPSC-derived BMECs reached values as high as 6500 Ω•cm 2 after one day of co-culture with human astrocytes. The high TEER decreased after two days of co-culture (d2) but it was maintained over 1000 Ω•cm 2 for a further 3-4 days, in the range thought to be physiologically relevant [32]. The paracellular transport of lucifer yellow was low (0.1-0.4 × 10 −6 cm/s) and comparable to the in vivo value obtained in 15 µm pial post capillary venules in a rat model [33].…”

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

“…With the increased use of iBMECs and their potential future applicability for preclinical studies, the need for validation of such models has become paramount. DeStefano and colleagues [81] recently outlined a set of 12 criteria for benchmarking and validating in vitro BBB models. These include critical assessments of permeability, the ultrastructure of tight junctions, expression of BBB markers, and transporter function.…”

Three-dimensional induced pluripotent stem-cell models of human brain angiogenesis

“…The extracellular space in the brain is comprised of hyaluronic acid, lecticans, proteoglycan link proteins, and tenascins [50,51]. However, as the human brain is highly cellular by volume, non-brain-specific ECM components are commonly used to mimic the physical properties of the brain [3,52,53]. For example, 3D BBB models commonly utilize nonbrain ECM components including collagen I [27,[54][55][56][57][58] and fibrin [20][21][22]59].…”

“…into the brain via expression of tight junctions (TJs), efflux pumps, and nutrient transporters [2,3].…”