Fabrication of a 3D multi-scale perfusable neurovascular unit

Blood-brain barrier (BBB) is a selective border delimiting the blood and the central nervous system (CNS). Composed of brain microvascular endothelial cells (BMEC), astrocytes and pericytes, the BBB along with neurons and immune cells forms the neurovascular unit (NVU), which is crucial for proper CNS function. While the BBB limited permeability protects the CNS from neuropathological agents, it also poses a challenge for delivering drugs to the brain. Several human in vitro NVU models were established, however, they do not fully recapitulate the in vivo NVU properties. A perfusable human 3D model of the NVU with hierarchical vasculature for disease modelling and drug discovery is in high demand. We harness tissue engineering (TE) techniques to generate a hierarchical perfusable human BBB model incorporating neural component.

To achieve that, we used a method enabling to generate multi-scale thick vascularized tissues (MSVT) by integrating self-assembled microcapillaries with prepatterned macrovessels in a 3D scaffold. Generation of brain vasculature using BMEC, pericytes and astrocytes tri-culture is expected to result in a perfusable hierarchical vascular network. Preliminary results show that BMEC can form mature microvasculature when co-cultured with pericytes on several scaffolds, namely collagen, silk-collagen, and PLLA\PLGA-collagen. Furthermore, BMEC form an intact, functional and patent macrovessel in all examined scaffolds. Lastly, tri-culture of BMEC, pericytes and astrocytes on silk-collagen results in astrocytes-microvasculature interaction via astrocyte end-feet, resembling an in vivo NVU. This multiscale engineered NVU will allow modelling neurodegenerative processes and drug screening, addressing both BBB permeability and drug effect on CNS.