Scalable fabrication of renal spheroids and nephron-like tubules by bioprinting and controlled self-assembly of epithelial cells

Scalable fabrication concepts of 3D kidney tissue models are required to enable their application in pharmaceutical high-throughput screenings. Yet the reconstruction of complex tissue structures remains technologically challenging. We present a novel concept reducing the fabrication demands, by using controlled cellular self-assembly to achieve higher tissue complexities from significantly simplified construct designs. We used drop-on-demand bioprinting to fabricate locally confined patterns of renal epithelial cells embedded in a hydrogel matrix. These patterns provide defined local cell densities (cell count variance <11%) with high viability (92 +/- 2%). Based on these patterns, controlled self-assembly leads to the formation of renal spheroids and nephron-like tubules with a predefined size and spatial localization. With this, we fabricated scalable arrays of hollow epithelial spheroids. The spheroid sizes correlated with the initial cell count per unit and could be stepwise adjusted, ranging from o = 84, 104, 120-131 mu m in diameter (size variance <9%). Furthermore, we fabricated scalable line-shaped patterns, which self-assembled to hollow cellular tubules (o = 105 +/- 22 mu m). These showed a continuous lumen with prescribed orientation, lined by an epithelial monolayer with tight junctions. Additionally, upregulated expression of kidney-specific functional genes compared to 2D cell monolayers indicated increased tissue functionality, as revealed by mRNA sequencing. Furthermore, our concept enabled the fabrication of hybrid tubules, which consisted of arranged subsections of different cell types, combining murine and human epithelial cells. Finally, we integrated the self-assembled fabrication into a microfluidic chip and achieved fluidic access to the lumen at the terminal sites of the tubules. With this, we realized flow conditions with a wall shear stress of 0.05 +/- 0.02 dyne cm(-2) driven by hydrostatic pressure for scalable dynamic culture towards a nephron-on-chip model.

Automated summary

The study introduces a novel concept for fabricating 3D kidney tissue models, utilizing controlled cellular self-assembly to reduce fabrication demands and achieve higher tissue complexities. The results show the ability to fabricate renal spheroids and nephron-like tubules with predefined size and spatial localization. Additionally, upregulated expression of kidney-specific functional genes compared to 2D cell monolayers indicates increased tissue functionality, highlighting the potential for pharmaceutical high-throughput screenings.