(52g) A Unifying Biomaterial for Constructing Chimeric Ex Vivo Neurovascular Tissue Structures

All neurodegenerative diseases are incurable, and there are no approved therapies for neurodegeneration that slow or reverse underlying disease pathology. In recent years, the contribution of brain vasculature to neurodegeneration has been increasingly recognized. Thus, there is a growing need for biomimetic models of the neurovasculature (i.e. neural cells integrated with functional blood vessels) that can be used to examine disease progression and test prospective therapeutics. However, the fabrication of such models faces many challenges, including sourcing of appropriate cell types, assembly of cells in a three-dimensional environment with proper organization, and functional maturation and integration of the cells to reflect endogenous tissue properties.

Here, in support of the development of chimeric neurovascular tissue structures, we present a biomaterial that can: 1) mature neural cells into functional networks and 2) promote spontaneous vascular outgrowth from ex vivo brain tissue. The biomaterial consists of gelatin, a crosslinking moiety, and a peptide derived from an extracellular epitope of type 1 cadherins. A variety of polymerization regimens can produce highly porous hydrogels that are relatively soft (1-2 kPa). When human induced pluripotent stem cell (iPSC)-derived neurons are embedded in the hydrogel, they form synaptically connected networks as determined by immunostaining, electrophysiology, and viral tracing. iPSC-derived astrocytes also incorporate well into the hydrogels, with robust process extension and minimal expression of GFAP indicating suppression of a reactive phenotype. When primary mouse brain tissue is embedded in the hydrogel, robust vascular outgrowth is observed, including larger arteriole structures with proper smooth muscle organization that branch into capillary beds consisting of single endothelial cells lined by pericytes. Ongoing work is being pursued to perfuse this ex vivo vasculature and co-culture iPSC-derived astrocytes and neurons within the hydrogel to complete the full neurovascular model. Collectively, we believe this chimeric system will yield nascent, self-organizing neurovascular architectures that have been difficult to engineer and thereby represent a highly useful model for drug screening and disease modeling in the near future.