Abstract

Recreating Kidney Organogenesis in vitro with Human Pluripotent Stem Cells

Ryuji Morizane, Assistant Professor, Harvard Medical School; Visiting Scholar, Wyss Institute

We have developed an efficient, chemically defined protocol for differentiating human pluripotent stem cells into multipotent nephron progenitor cells (NPCs) that can form kidney organoids. By recapitulating metanephric kidney development in vitro we generate SIX2⁺SALL1⁺WT1⁺PAX2⁺ NPCs with 80-90% efficiency within 8-9 days of differentiation. NPCs form kidney organoids containing epithelial nephron-like structures expressing markers of podocytes, proximal tubules, loops of Henle and distal nephrons in an organized, continuous arrangement that resembles the nephron in vivo. The organoids express genes reflecting many transporters seen in adult metanephric-derived kidney, enabling assessment of transporter-mediated drug nephrotoxicity. Stromal cells are also generated with the presence of PDGFRBeta⁺ fibroblasts/pericytes, and CD31⁺ endothelial cells. This kidney differentiation system can be used to study mechanisms of human kidney development. Repetitive injury to tubular cells causes interstitial fibroblast expansion with characteristics of myofibroblasts, indicating kidney organoids can be used to model kidney fibrosis in vitro. Polycystic kidney disease (PKD) patient-derived organoids exhibit cystic phenotypes. Hence the generated kidney organoids are effective tools to study genetic disorders of the kidney as well as mechanisms of kidney injury and fibrosis. Microphysiological platforms in vitro facilitate kidney organoid vascularization and maturation, which may lead to the development of functional bioengineered kidneys in the future.