Pericytes repair engineered defects in the basement membrane to restore barrier integrity in an in vitro model of the blood-brain barrier

Pericytes play a key role in the brain where they support brain microvascular endothelial cells (BMECs) in forming the tightly regulated blood-brain barrier (BBB). The loss of pericytes, and corresponding weakening of the BBB, has been reported in response to episodes of systemic inflammation and in neurodegenerative disease. We recently demonstrated that iPSC-derived pericyte-like and BMEC-like cells form a nascent, 3D basement membrane when cultured across an ultrathin (100 nm thick) and highly nanoporous membrane (McCloskey, Ahmed et al., AHCM 2024). We also concluded that the pericyte-like cells did not contribute soluble factors to enhance permeability. Given the structural role of pericytes in vivo, here we sought to engineer defects in the basement membrane to see if pericytes could repair them. In BMEC-like monocultures, we found that micropore (3 μm and 5 μm) patterns in nanomembranes appeared as corresponding discontinuities in basement membrane laminin and destabilized barrier function. Both the laminin defects and the baseline barrier function were restored with the addition of pericytes on the basal side of the membrane. We further found that: 1) BMECs transmigrate through large micropores in monocultures but not in co-culture with pericytes, and 2) pericytes stabilized barrier function. Our results align with the role of pericytes as structural support cells for the microvasculature and encourage the use of our tissue barrier platform (the μSiM) to model acute and chronic neurological disorders involving pericyte dysfunction and/or disruption of basement membrane integrity.