Redefining the In Vivo Origin of Metanephric Nephron Progenitors Enables Generation of Complex Kidney Structures from Pluripotent Stem Cells

Abstract

Recapitulating three-dimensional (3D) structures of complex organs, such as the kidney, from pluripotent stem cells (PSCs) is a major challenge. Here, we define the developmental origins of the metanephric mesenchyme (MM), which generates most kidney components. Unexpectedly, we find that posteriorly located T(+) MM precursors are developmentally distinct from Osr1(+) ureteric bud progenitors during the postgastrulation stage, and we identify phasic Wnt stimulation and stage-specific growth factor addition as molecular cues that promote their development into the MM. We then use this information to derive MM from PSCs. These progenitors reconstitute the 3D structures of the kidney in vitro, including glomeruli with podocytes and renal tubules with proximal and distal regions and clear lumina. Furthermore, the glomeruli are efficiently vascularized upon transplantation. Thus, by reevaluating the developmental origins of metanephric progenitors, we have provided key insights into kidney specification in vivo and taken important steps toward kidney organogenesis in vitro.

The Ever–Expanding Kidney Repair Shop

“…2 It took some time for this uncontrolled in vivo potential to be translated into highly directed and controlled in vitro differentiation of pluripotent stem cells toward renal lineages. 3,4 The understanding of how the mammalian kidney develops in vivo laid the foundation for deciphering the inductive signals required for the in vitro directed renal differentiation protocols from pluripotent stem cells. For instance, Six21Cited11 nephron progenitors residing in the nephrogenic cortex were shown to give rise to all types of nephron epithelia.…”

“…Nishinakamura and colleagues 3 further translated knowledge of early kidney development into an efficient differentiation protocol; they were able to separate anterior from posterior intermediate mesoderm in the early stages of renal differentiation. 3 Although a transcription factor T (also known as Brachyury) is mainly expressed in the immature mesoderm of the primitive streak at E7.5, Nishinakamura and colleagues 3 found that the precursors of nephron progenitors remained as T1 immature cells at the posterior end of E8.5 embryos. These cells convert to Osr11 posterior intermediate mesoderm at E9.5, whereas the ureteric bud precursors convert from T1 to Osr11 anterior intermediate mesoderm 1 day earlier (E8.5).…”

“…These cells convert to Osr11 posterior intermediate mesoderm at E9.5, whereas the ureteric bud precursors convert from T1 to Osr11 anterior intermediate mesoderm 1 day earlier (E8.5). On the basis of these findings, Nishinakamura and colleagues 3 were able to establish a protocol to induce nephron progenitors from T1 cells of E8.5 embryos and subsequently, succeeded in inducing nephron progenitors from mouse embryonic stem cells and human induced pluripotent stem cells (iPSCs). The induced nephron progenitor aggregates readily formed three-dimensional primordial glomeruli and renal tubules on Wnt stimulation in vitro, similar to those spontaneously observed in teratomas.…”

“…The induced nephron progenitor aggregates readily formed three-dimensional primordial glomeruli and renal tubules on Wnt stimulation in vitro, similar to those spontaneously observed in teratomas. 2 Importantly, like other recent in vitro renal differentiation protocols, 6 Nishinakamura and colleagues 3 use iPSCs generated according to the Yamanaka method as the starting material, potentially affording patient-derived autologous cells rather than allogeneic cells for transplant and the possibility of personalized renal medicine.…”

“…3 Sharmin et al 1 did so by inserting the GFP gene into the nephrin (NPHS1) locus of human iPSCs and visualizing the GFP-tagged podocyte formation in vitro. Sharmin et al 1 went on to show that the podocytes in vitro have the typical transcriptional and morphologic features of those in vivo.…”