Graft immaturity and safety concerns in transplanted human kidney organoids

Abstract

For chronic kidney disease, regeneration of lost nephrons with human kidney organoids derived from induced pluripotent stem (iPS) cells is proposed to be an attractive potential therapeutic option. It remains unclear, however, whether organoids transplanted into kidneys in vivo would be safe or functional. Here, we purified kidney organoids and transplanted them beneath the kidney capsules of immunodeficient mice to test their safety and maturity. Kidney organoid grafts survived for months after transplantation and became vascularized from host mouse endothelial cells. Nephron-like structures in grafts appeared more mature than kidney organoids in vitro, but remained immature compared with the neighboring mouse kidney tissue. Ultrastructural analysis revealed filtration barrier-like structures, capillary lumens, and tubules with brush border in the transplanted kidney organoids, which were more mature than those of the kidney organoids in vitro but not as organized as adult mammalian kidneys. Immaturity was a common feature of three separate differentiation protocols by immunofluorescence analysis and single cell RNA sequencing. Stroma of transplanted kidney organoid grafts were filled with vimentin-positive mesenchymal cells, and chondrogenesis, cystogenesis, and stromal expansion were observed in the long term. Transcription profiles showed that long-term maintenance after kidney organoid transplantation induced transcriptomic reprogramming with prominent suppression of cell-cycle-related genes and upregulation of extracellular matrix organization. Our data suggest that kidney organoids derived from iPS cells may be transplantable but strategies to improve nephron differentiation and purity are required before they can be applied in humans as a therapeutic option.

Stem cell-based treatment of kidney diseases

“…However, both studies transplanted metanephroi not kidney organoids into rats. A recent study 99 showed transplanted kidney organoids beneath kidney capsule could survive for several months and also be vascularized from endothelial cells of host mice. Finally, although kidney organoids exhibit better nephron-like structures after transplantation, structure of tubules brush border, filtration barrier, and capillary lumens were not as organized as in the mature kidney tissues, requiring further improvement of kidney organoids differentiation.…”

Promoting Maturation of Human Pluripotent Stem Cell-Derived Renal Microtissue by Incorporation of Endothelial and Mesenchymal Cells

“…Unfortunately, these protocols have numerous challenges, including extended time periods and expensive differentiation procedures, as well as the immaturity of differentiated cells [2]. These cells are not suitable for clinical applications due to graft immaturity and safety concerns [22]. Therefore, tremendous efforts have been taken to develop safe, efficient, inexpensive, and rapid approaches.…”

Convergence of human pluripotent stem cell, organoid, and genome editing technologies

“…However, in organoids through directed differentiation from iPSCs, maturation and functionality remain a prominent problem in many tissue types at present. 153–156 This is owing to the molecular mechanisms governing developmental trajectory of organs remain largely unknown. It is anticipated that, with more molecular mechanisms being deciphered in iPSCs, more mature iPSC-derived organoids can be achieved.…”