Characterization of the metabolic properties of brain microvascular endothelial cells

Abstract

The blood-brain barrier (BBB) is a highly restrictive and regulated vascular network, strictly controlling the molecules that enter the brain via the bloodstream, while also serving an important role in the removal of toxic compounds from the brain. Brain microvascular endothelial cells (BMECs) line the capillaries, forming the BBB. BBB disruption is a crucial event in many neurovascular and neurodegenerative disorders. As such, a better understanding of the mechanisms regulating the BBB during health and disease is expected to provide potentially groundbreaking insights for treatment of a variety of neurological disorders. One understudied aspect of BMECs are the metabolic mechanisms regulating BBB function. Many of the initial in vitro models utilized animal cells or immortalized human cell lines; however, significant limitations exist with each of these. Recently, human induced pluripotent stem cells have been differentiated into BMECs. This led to many studies that significantly enhanced our knowledge of the human BBB, but most differentiation schematics use serum in the process. Serum has a large degree of batch-to-batch variability that has direct consequences on the success of the differentiation. Additionally, serum is undefined, making metabolic studies difficult because all of the substances in the media are not known. Thus, specific metabolite profiles between conditions cannot be traced to a specific origin. We developed a novel, serum-free and fully defined differentiation protocol to make BMECs from iPSCs. This new iteration permits precise metabolic studies and, as such, we have begun to characterize previously undefined metabolic characteristics in iPSC-derived BMECs.