Enhancing vascularization of iPSC derived renal organoids

Abstract

In humans, kidney disease is a significant health burden magnified by the poor regenerative capacity of nephrons upon injury, resulting in a deterioration of kidney functions that manifests itself as chronic kidney disease. Kidney organoids have huge potential as a useful tool for modelling human kidney diseases, development, personalised and regenerative medicine, but are currently limited by their immature fetal-like expression patterns. Hemodynamic forces are known to promote vascularization of the kidney, resulting in tissue maturation in vivo. In this thesis, I subjected human induced pluripotent stem cell (iPSC) derived kidney organoids to increased media flow conditions in spinning bioreactors. Media flow resulted in increased organoid growth rates, indicated glomerular maturation and expansion of the proximal and distal tubules. By contrast, the degree of vascularisation in the organoids remained unchanged by the shear forces applied. These results suggest that mechanical force upon organoids is important for the segmentation of the nephron in organoids, mirroring in vivo experience. Furthermore, these indicate that the increased media flow alone is insufficient in inducing further vascularisation/maturation. Inclusion of other factors that mirror the in vivo circulatory haemodynamic forces might be necessary to improve the maturation of organoids cultured in vitro. Furthermore, I generated endothelial cells from iPSCs (iPSC-ECs), and piloted a co-culture between these and autologous kidney organoids. Three protocols were adapted for trial within the lab, from which one was fully characterised and deemed appropriate for co-culture. Organoids were embedded into hanging droplets of ECM and iPSC-ECs were either embedded with them or seeded atop these droplets. Whilst infiltration of iPSC-ECs into organoids was not observed here, the establishment of this protocol serves as a basis for investigation of other methods of co-culture for future trials.