Search

Generation of kidney organoids from pluripotent stem cells (PSCs) is regarded as a potentially powerful way to study kidney development, disease, and regeneration. Direct differentiation of PSCs towards renal lineages is well studied; however, most of the studies relate to generation of nephron progenitor population from PSCs. Until now, differentiation of PSCs into ureteric bud (UB) progenitor cells has had limited success. Here, we describe a simple, efficient, and reproducible protocol to direct differentiation of mouse embryonic stem cells (mESCs) into UB progenitor cells. The mESC-derived UB cells were able to induce nephrogenesis when co-cultured with primary metanephric mesenchyme (pMM). In generated kidney organoids, the embryonic pMM developed nephron structures, and the mESC-derived UB cells formed numerous collecting ducts connected with the nephron tubules. Altogether, our study established an uncomplicated and reproducible platform to generate ureteric bud progenitors from mouse embryonic stem cells., Competing Interests: The authors declare no conflict of interest.

Kidney development and induction of tubulogenesis have been studied for almost seven decades. The experimental setup of metanephric mesenchyme induction ex vivo allows to control the environment, to perform cellular manipulations, and to learn about renal development. Since the establishment of the ex vivo kidney culture technique in 1953, the method was modified to suit well the progress in biological and medical fields and still today present many advantages over the traditional in vivo studies.

Organ transplantation is currently the best strategy for treating end stage renal disease (ESRD) but the numbers of donor kidneys available are not sufficient to meet the needs of the ever-increasing ESRD population. Therefore, developments in the field of tissue engineering are necessary to provide alternative treatments. Decellularization and three-dimensional (3D) bioprinting strategies may serve as attractive novel options. Since successful tissue engineering requires an in -depth understanding of organ development and regulatory pathways, we discuss signaling in renal development and the composition of the renal extracellular matrix before presenting progress in the decellularization and 3D bioprinting fields.

Tissue, organ and organoid cultures provide suitable models for developmental studies, but our understanding of how the organs are assembled at the single-cell level still remains unclear. We describe here a novel fixed z -direction (FiZD) culture setup that permits high-resolution confocal imaging of organoids and embryonic tissues. In a FiZD culture a permeable membrane compresses the tissues onto a glass coverslip and the spacers adjust the thickness, enabling the tissue to grow for up to 12 days. Thus, the kidney rudiment and the organoids can adjust to the limited z -directional space and yet advance the process of kidney morphogenesis, enabling long-term time-lapse and high-resolution confocal imaging. As the data quality achieved was sufficient for computer-assisted cell segmentation and analysis, the method can be used for studying morphogenesis ex vivo at the level of the single constituent cells of a complex mammalian organogenesis model system., (© 2017. Published by The Company of Biologists Ltd.)

New therapies that are derived from small molecules and stem/progenitor cells should be developed to face the increasing occurrence of end stage renal disease where treatments are currently limited. Over the last decade a significant progress in the knowledge of how the organs are assembled have been made and led to development of novel three-dimensional organoid assays, also for the kidney. Indeed, such organoids provide novel tool to study aspects of drugs nephrotoxicity, openings for renal disease modeling and cell therapy development and may offer solutions for end stage renal disease., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Embryonic stem cells (ESC) are self-renewing and can generate all cell types during normal development. Previous studies have begun to explore fates of ESCs and their mesodermal derivatives after injection into explanted intact metanephric kidneys and neonatal kidneys maturing in vivo. Here, we exploited a recently described recombinant organ culture model, mixing fluorescent quantum dot labeled mouse exogenous cells with host metanephric cells. We compared abilities of undifferentiated ESCs with ESC-derived mesodermal or non-mesodermal cells to contribute to tissue compartments within recombinant, chimeric metanephroi. ESC-derived mesodermal cells downregulated Oct4, a marker of undifferentiated cells, and, as assessed by locations of quantum dots, contributed to Wilms' tumor 1-expressing forming nephrons, synaptopodin-expressing glomeruli, and organic ion-transporting tubular epithelia. Similar results were observed when labeled native metanephric cells were recombined with host cells. In striking contrast, non-mesodermal ESC-derived cells strongly inhibited growth of embryonic kidneys, while undifferentiated ESCs predominantly formed Oct4 expressing colonies between forming nephrons and glomeruli. These findings clarify the conclusion that ESC-derived mesodermal cells have functional nephrogenic potential, supporting the idea that they could potentially replace damaged epithelia in diseased kidneys. On the other hand, undifferentiated ESCs and non-mesodermal precursors derived from ESCs would appear to be less suitable materials for use in kidney cell therapies.

Mesenchymal stem cells (MSCs) are a multipotent cell population which has been described to exert renoprotective and regenerative effects in experimental models of kidney injury. Several lines of evidence indicate that MSCs also have the ability to contribute to nephrogenesis, suggesting that the cells can be employed in stem cell-based applications aimed at de novo renal tissue generation. In this study we re-evaluate the capacity of mouse and human bone marrow-derived MSCs to contribute to the development of renal tissue using a novel method of embryonic kidney culture. Although MSCs show expression of some genes involved in renal development, their contribution to nephrogenesis is very limited in comparison to other stem cell types tested. Furthermore, we found that both mouse and human MSCs have a detrimental effect on the ex vivo development of mouse embryonic kidney, this effect being mediated through a paracrine action. Stimulation with conditioned medium from a mouse renal progenitor population increases the ability of mouse MSCs to integrate into developing renal tissue and prevents the negative effects on kidney development, but does not appear to enhance their ability to undergo nephrogenesis., (Copyright © 2011 International Society of Differentiation. Published by Elsevier B.V. All rights reserved.)

Quantum dots (QDs) are small nanocrystals widely used for labelling cells in order to enable cell tracking in complex environments in vitro, ex vivo and in vivo. They present many advantages over traditional fluorescent markers as they are resistant to photobleaching and have narrow emission spectra. Although QDs have been used effectively in cell tracking applications, their suitability has been questioned by reports showing they can affect stem cell behaviour and can be transferred to neighbouring cells. Using a variety of cellular and molecular biology techniques, we have investigated the effect of QDs on the proliferation and differentiation potential of two stem cell types: mouse embryonic stem cells and tissue-specific stem cells derived from mouse kidney. We have also tested if QDs released from living or dead cells can be taken up by neighbouring cells, and we have determined if QDs affect the degree of cell-cell fusion; this information is critical in order to assess the suitability of QDs for stem cell tracking. We show here that QDs have no effect on the viability, proliferation or differentiation potential of the two stem cell types. Furthermore, we show that the extent of transfer of QDs to neighbouring cells is <4%, and that QDs do not increase the degree of cell-cell fusion. However, although the QDs have a high labelling efficiency (>85%), they are rapidly depleted from both stem cell populations. Taken together, our results suggest that QDs are effective cell labelling probes that are suitable for short-term stem cell tracking.

In the future, stem-cell-based therapies could offer new approaches to treat kidney disease and reduce the incidence of ESRD (end-stage renal disease), but, as yet, research in this area is only being conducted in rodents and it is not clear whether or when it could be applied to human patients. Drug therapies, on the other hand, have been very effective at delaying the progression of kidney disease, but, for various reasons, current drug regimes are not suitable for all patients. A greater understanding of the molecular mechanisms that underlie disease progression in chronic kidney disease could help to identify novel drug targets. However, progress in this area is currently hindered due to the lack of appropriate in vitro culture systems for important renal cell types, such as proximal tubule cells and podocytes. This problem could be overcome if it were possible to direct the differentiation of kidney stem cells to renal cell types in vitro. In the present review, we highlight the potential of surface gradients of small chemical functional groups to direct the differentiation of kidney stem cells.

The renal tubular epithelial cells (TEC) have a strong capacity for repair after acute injury, but when this mechanism becomes uncontrollable, it leads to chronic kidney diseases (CKD). Indeed, in progress toward CKDs, the TECs may dedifferentiate, undergo epithelial-to-mesenchyme transition (EMT), and promote inflammation and fibrosis. Given the critical role of Wnt4 signaling in kidney ontogenesis, we addressed whether changes in this signaling are connected to renal inflammation and fibrosis by taking advantage of a knock-in Wnt4 mCh/mCh mouse. While the Wnt4 mCh/mCh embryos appeared normal, the corresponding mice, within one month, developed CKD-related phenotypes, such as pro-inflammatory responses including T-cell/macrophage influx, expression of fibrotic markers, and epithelial cell damage with a partial EMT. The Wnt signal transduction component β-catenin remained unchanged, while calcium signaling is induced in the injured TECs involving Nfat and Tfeb transcription factors. We propose that the Wnt4 signaling pathway is involved in repairing the renal injury, and when the signal is overdriven, CKD is established. [Display omitted] • Wnt4 overexpression alters kidney functions and promotes renal fibrosis in adult mice leading to chronic kidney disease (CKD) • Wnt4 overexpression triggers damage in the tubule epithelial cells leading to T-cells infiltration and promotes partial EMT • Wnt4 overexpression initiates ER calcium release in the TECs which in turn activates non-canonical Wnt signaling pathway • Calcineurin activates Wnt target genes controlled by Tfeb transcription factor, and injured TECs can not repaired themselves [ABSTRACT FROM AUTHOR]