P450 oxidoreductase regulates barrier maturation by mediating retinoic acid metabolism in a model of the human BBB

• Published in: Stem cell reports 2022-09, Vol.17 (9), p.2050-2063
• Main Authors: Zlotnik, Dor, Rabinski, Tatiana, Halfon, Aviv, Anzi, Shira, Plaschkes, Inbar, Benyamini, Hadar, Nevo, Yuval, Gershoni, Orly Yahalom, Rosental, Benyamin, Hershkovitz, Eli, Ben-Zvi, Ayal, Vatine, Gad D.
• Format: Article
• Language: English
• ISSN: 2213-6711; 2213-6711
• DOI: 10.1016/j.stemcr.2022.07.010

The blood-brain barrier (BBB) selectively regulates the entry of molecules into the central nervous system (CNS). A crosstalk between brain microvascular endothelial cells (BMECs) and resident CNS cells promotes the acquisition of functional tight junctions (TJs). Retinoic acid (RA), a key signaling molecule during embryonic development, is used to enhance in vitro BBB models’ functional barrier properties. However, its physiological relevance and affected pathways are not fully understood. P450 oxidoreductase (POR) regulates the enzymatic activity of microsomal cytochromes. POR-deficient (PORD) patients display impaired steroid homeostasis and cognitive disabilities. Here, we used both patient-specific POR-deficient and CRISPR-Cas9-mediated POR-depleted induced pluripotent stem cell (iPSC)-derived BMECs (iBMECs) to study the role of POR in the acquisition of functional barrier properties. We demonstrate that POR regulates cellular RA homeostasis and that POR deficiency leads to the accumulation of RA within iBMECs, resulting in the impaired acquisition of TJs and, consequently, to dysfunctional development of barrier properties. • Retinoic acid (RA) promotes functional barrier properties • POR-deficient iPS-brain endothelial-like cells display impaired barrier development • POR mediates CYP26-dependent cellular RA catabolism • RA accumulation induces a pro-inflammatory response In this article, Vatine and colleagues show that P450 oxidoreductase (POR) is crucial for the development of a functional blood brain barrier (BBB). They show that POR regulates cellular retinoic acid levels through mediating its CYP26-dependent catabolism. In turn, transcriptional pathways involving tight junction and integrin genes are disrupted. These barrier impairments may contribute to the neurological symptoms in POR-deficient patients.