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.
Highlights
Chronic kidney disease (CKD) has emerged as a global healthcare crisis[1]
Immunofluorescence analysis revealed that cells expressing markers of podocytes (NPHS1), parietal epithelial cells or PECs, proximal tubular cells (Lotus tetragonolobus lectin or LTL), and distal tubules (ECAD) in the transplanted kidney organoids originated from the induced pluripotent stem (iPS) cells, not from the host mouse kidneys (Fig. 2a, b)
We found that cartilage formation in the group transplanted with kidney decellularized extracellular matrix (dECM) was decreased compared with the group transplanted with kidney organoids only (Supplementary Fig. S5), which suggest that maldifferentiation after kidney organoids transplantation may be corrected by adjustment of microenvironment components provided by kidney dECM
Summary
Chronic kidney disease (CKD) has emerged as a global healthcare crisis[1]. CKD often leads to end-stage renal disease (ESRD), for which patients require either hemodialysis or kidney transplantation in order to survive. Both renal replacement therapies are limited— the mortality and morbidity rates in patients on dialysis. CKD progression results from a loss of functional nephrons[2]. Since new nephrons cannot be generated in the adult human kidney, the functional nephrons lost during the progression of CKD cannot be recovered naturally. Regenerative medicine, in which the nephrons lost during CKD progression are replaced using stem cells, is an attractive potential therapeutic option for CKD. We and others have established several different protocols for the generation of kidney organoids
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