Acoustical bioengineering of cortex-like constructs by levitational assembly of primate neural stem cells

Abstract

We combined bulk acoustic levitation with layer-by layer assembly to bioengineer cortex-like multilayered single constructs containing heterogeneous layers of cells, with micrometer-scale control over biological and structural features. The constructs were obtained by acoustically levitating, in a mix of fibrinogen and thrombin, primate Neural Stem Cells (NSCs) derived from monkey embryonic stem cells that stably express a tau-GFP fusion protein, enabling detailed visualization of living cell morphology, including dendrites and axons. The levitation process was repeated several times to superpose, in a single final construct with an interlayer distance of 180μm, the NSCs at three stages of differentiation, corresponding to brain progenitor cells and immature cerebral cortex neurons. The constructs were then cultured in neuronal differentiating medium, fixed and immunostained for confocal microscopy analyses. Immunostaining analyses revealed cells exhibiting neuronal and glial phenotypes. Complex intercellular connections formed by neurons and glial cells, and extending processes and inter- and intra-layers connections between layers of differentiated NSCs were monitored. The proposed acoustical method is potentially useful to create informative in vitro models of the developing primate brain, such as the multi-layered cerebral cortex, as it allows the assembly of heterogeneous cell populations, and supports proliferation and differentiation in 3D.