The FGF, TGFβ and WNT axis Modulate Self-renewal of Human SIX2+ Urine Derived Renal Progenitor Cells

Abstract

Human urine is a non-invasive source of renal stem cells with regeneration potential. Urine-derived renal progenitor cells were isolated from 10 individuals of both genders and distinct ages. These renal progenitors express pluripotency-associated proteins-TRA-1-60, TRA-1-81, SSEA4, C-KIT and CD133, as well as the renal stem cell markers-SIX2, CITED1, WT1, CD24 and CD106. The transcriptomes of all SIX2 + renal progenitors clustered together, and distinct from the human kidney biopsy-derived epithelial proximal cells (hRepcs). Stimulation of the urine-derived renal progenitor cells (UdRpcs) with the GSK3β-inhibitor (CHIR99021) induced differentiation. Transcriptome and KEGG pathway analysis revealed upregulation of Wnt-associated genes-AXIN2, JUN and NKD1. protein interaction network identified JUN-a downstream target of the WNT pathway in association with STAT3, ATF2 and MAPK1 as a putative negative regulator of self-renewal. furthermore, like pluripotent stem cells, self-renewal is maintained by FGF2-driven TGFβ-SMAD2/3 pathway. The urine-derived renal progenitor cells and the data presented should lay the foundation for studying nephrogenesis in human. According to the International Society of Nephrology, more than 850 million people worldwide are afflicted with kidney diseases 1 , which raises the quest for alternative therapies to overcome the limitations associated with current treatments including transplantation and dialysis. One of the most promising options is the utilization of renal stem cells for treating of kidney diseases, disease modelling, and drug development 2,3. Renal stem/ progenitor cells are self-renewing, multipotent cells with the ability to generate various cell types of the kidney to maintain renal function 4. These progenitors are in abundance during fetal kidney development in which the renal progenitor surface marker CD24 and stem cell self-renewal marker CD133 cells are required for primordial nephrogenesis 5,6. However, in adults, CD24, CD133 (Prominin-1) and vascular cell adhesion molecule 1 (CD106)-positive renal progenitors are present in renal tubules and capsules 7. Two progenitor cell populations can be distinguished based on the expression of CD106. For instance, CD24 + CD133 + CD106 − progenitors are present in proximal tubules whereas CD24 + CD133 + CD106 + cells are localized in the Bowman's capsule. The latter can differentiate into a variety of cell types of renal tissue such as podocytes and tubular epithelial cells 4-7. Several groups have identified urine as a non-invasive and repetitive source of renal progenitor cells 8,9. It has been estimated that each day approximately 2,000 to 7,000 cells composed of differentiated epithelial cells, bi-potential epithelial cells (transitional cells), multipotent mesenchymal stem cells, and glomerular parietal cells are flushed out from the renal tubular network and the upper urinary tract into urine 10-12. A subpopulation of these urine-derived cells are renal stem/progenitor cells which express master renal markers such as Sine...

Urine-derived stem/progenitor cells: A focus on their characterization and potential

“…Human USCs expressed a variety of markers, and their proposed phenotypes vary according to studies, urine sample and likewise between single colonies appearing in a single urine sample[ 20 , 27 , 28 ].…”

Altered FGF expression profile in human scalp-derived fibroblasts upon WNT activation: implication of their role to provide folliculogenetic microenvironment

“…The relationship between FGFs and WNT signaling can be more complex in a certain tissue environment [ 47 ]. In urine-derived renal progenitors, WNT activation upregulates TGF-β pathway, which leads to the downregulation of FGF2 [ 48 ]. If the same machinery underlies hair neogenesis remains elusive; however, the downregulation of FGF2 via WNT activation in our experiment is consistent with this observation.…”

Molecular Mechanisms of Renal Progenitor Regulation: How Many Pieces in the Puzzle?

“…These cells have the capability to differentiate into podocytes [ 138 ] and express podocyte- and PEC-specific protein markers [ 137 , 139 ], suggesting that they originate from PECs. A comparative transcriptome analysis of urine-derived renal progenitors and kidney biopsy-derived renal epithelial proximal cells confirmed the renal progenitor identity of urine-derived progenitors [ 87 ], indicating that they could also originate from scattered tubular progenitors. These cells can be reprogrammed into induced pluripotent stem cells (iPSC) and be used for regenerative medicine, disease modeling or pharmacological testing [ 140 , 141 ].…”

“…They suggested that the ability to respond to WNT signals selects for the cells which will ultimately carry out robust clonal expansion. Studies in SIX2+ urine-derived renal progenitors indicated that WNT pathway activation by GSK3β inhibition induces the differentiation of renal progenitors into renal epithelial proximal tubular cells [ 87 ]. In addition, Wnt3 exerted pro-regenerative effects and was upregulated in CD133+ renal progenitors in an in vitro model of cisplatin injury [ 88 ].…”