To pave the silk road: A functionalized microvasculature network for the blood-brain interface

A functional microvasculature is a paramount target for accomplishing long-lasting engineered tissues. The challenge in neuroscience is building a microvascular network that could mimic the neurovascular unit, allowing the central nervous system (CNS) vitality. The vessels invade the CNS extracellular matrix (ECM) during embryogenesis. Biomaterials can offer the structural guidance and signaling pathways to recapitulate this complex process. Our project (THOR – European Innovation Council-Pathfinder Programme, Grant Agreement number 101099719) uses high-performance functionalized silk fibers with an innovative spinning technique, allowing the deposition of individual functionalized fibers (10-20 micrometers) with customized geometries. We present the results obtained with C57BL/6 Mouse Embryonic Brain Endothelial Cells seeded on silk scaffolds functionalized with either vascular endothelial growth factor (VEGF) or the laminin alpha-1 chain Ile-Lys-Val-Ala-Val (IKVAV) peptides. The same cells were cultivated on silk meshes to build a three-dimensional endothelial network for hippocampal vascularization. We obtained the vascular invasion of the scaffolds and the meshes and the formation of tube-like structures that express the blood-brain barrier (claudin-5) and pericytic biomarkers (CD13, PDGFRbeta). The endothelium produced basal lamina proteins (collagen IV, laminin) as they were anchored, parallel, or perpendicular to the silk fibers. In conclusion, we observed how diverse peptides bound to the silk can stimulate the embryonic cells to self-organize differently within the engineered frame to support hippocampal tissue. These results will pave the way for complex microvasculature networks and regenerative medicine targeting the CNS.