Biofabrication of a filtration barrier by integrating electrospun membranes and flow in a glomerular co-culture

The glomerulus is the functional unit of the kidney, where urine is filtered from blood. This process happens through the glomerular filtration barrier (GFB) which is composed of glomerular endothelial cells, podocytes, and glomerular basement membrane (GBM). Damage to any component of GFB results in failure of the barriers function, causing proteinuria that can lead to end-stage kidney failure. There is a high need for reliable in vitro models of the GFB to study pathological conditions and to test potential novel therapeutic options. We established an artificial GBM generated by electrospinning of poly-L-lactic acid fibers that were coated with polydopamine and gelatin and seeded with human glomerular endothelial cells and podocytes onto different sides. The orientation of fibers in the artificial GBM, their surface chemistry and effects on glomerular cells were characterized in depth. Glomerular endothelial cells and podocytes, including hiPSC-derived podocytes formed monolayers on the artificial GBM and revealed cell type-specific marker expression and morphology. Cell-cell communication was possible between podocytes and glomerular endothelial cells in both directions though the artificial membrane. Different molecular dextrans showed size selective permeability of the ex vivo GFB model. Introduction of shear stress by applying flow with a 3D printed micro-bioreactor improved cellular ultrastructure with formation of glomerular endothelial cell fenestrae-like structures and long podocyte foot process-like protrusions that both are usually absent in other in vitro models. Personalized hiPSC-derived podocytes within our model will allow to study the role of patient-specific podocyte mutations or individual treatment response ex vivo in the future.