Maintenance of Mouse Nephron Progenitor Cells in Aggregates with Gamma-Secretase Inhibitor

Evaluation of the ability of human induced nephron progenitor cells to form chimeric renal organoids using mouse embryonic renal progenitor cells

The number of patients with end-stage renal failure is increasing annually worldwide and the problem is compounded by a shortage of renal transplantation donors. In our previous research, we have shown that transplantation of renal progenitor cells into the nephrogenic region of heterologous fetuses can induce the development of nephrons. We have also developed transgenic mice in which specific renal progenitor cells can be removed by drugs. By combining these two technologies, we have succeeded in generating human-mouse chimeric kidneys in fetal mice. We hope to apply these technologies to regenerative medicine. The quality of nephron progenitor cells (NPCs) derived from human pluripotent stem cells is important for the generation of chimeric kidneys, but there is currently no simple evaluation system for the chimerogenic potential of human NPCs. In this study, we focused on the fact that the re-aggregation of mouse renal progenitor cells can be used for nephron formation, even when merged into single cells. First, we examined the conditions under which nephron formation is likely to occur in mice during re-aggregation. Next, to improve the differentiation potential of human NPCs derived from pluripotent stem cells, NPCs were sorted using Integrin subunit alpha 8 (ITGA8). Finally, we demonstrated chimera formation between different species by mixing mouse cells with purified, selectively-induced human NPCs under optimum conditions. We observed these chimeric organoids at different time points to learn about these human-mouse chimeric structures at various stages of renal development. We found that the rate of chimera formation was affected by the purity of the human NPCs and the cell ratios used. We demonstrated that chimeric nephrons can be generated using a simple model, even between distant species. We believe that this admixture of human and mouse renal progenitor cells is a promising technology with potential application for the evaluation of the chimera formation abilities of NPCs.

Bioluminescent imaging in induced mouse models of endometriosis reveals differences in four model variations

Our understanding of the aetiology and pathophysiology of endometriosis remains limited. Disease modelling in the field is problematic as many versions of induced mouse models of endometriosis exist. We integrated bioluminescent imaging of ‘lesions’ generated using luciferase-expressing donor mice. We compared longitudinal bioluminescence and histology of lesions, sensory behaviour of mice with induced endometriosis and the impact of the gonadotropin-releasing hormone antagonist Cetrorelix on lesion regression and sensory behaviour. Four models of endometriosis were tested. We found that the nature of the donor uterine material was a key determinant of how chronic the lesions were, as well as their cellular composition. The severity of pain-like behaviour also varied across models. Although Cetrorelix significantly reduced lesion bioluminescence in all models, it had varying impacts on pain-like behaviour. Collectively, our results demonstrate key differences in the progression of the ‘disease’ across different mouse models of endometriosis. We propose that validation and testing in multiple models, each of which may be representative of the different subtypes/heterogeneity observed in women, should become a standard approach to discovery science in the field of endometriosis.

Summary: Different versions of syngeneic mouse models of induced endometriosis exhibit disparities in chronicity and cellular composition of lesions, as well as endometriosis-associated hyperalgesia.

Proteomic profiling dataset of chemical perturbations in multiple biological backgrounds

While gene expression profiling has traditionally been the method of choice for large-scale perturbational profiling studies, proteomics has emerged as an effective tool in this context for directly monitoring cellular responses to perturbations. We previously reported a pilot library containing 3400 profiles of multiple perturbations across diverse cellular backgrounds in the reduced-representation phosphoproteome (P100) and chromatin space (Global Chromatin Profiling, GCP). Here, we expand our original dataset to include profiles from a new set of cardiotoxic compounds and from astrocytes, an additional neural cell model, totaling 5300 proteomic signatures. We describe filtering criteria and quality control metrics used to assess and validate the technical quality and reproducibility of our data. To demonstrate the power of the library, we present two case studies where data is queried using the concept of "connectivity" to obtain biological insight. All data presented in this study have been deposited to the ProteomeXchange Consortium with identifiers PXD017458 (P100) and PXD017459 (GCP) and can be queried at https://clue.io/proteomics .

Sirt3 promotes the autophagy of HK‑2 human proximal tubular epithelial cells via the inhibition of Notch‑1/Hes‑1 signaling

Diabetic nephropathy (DN) is a predominant cause of end-stage renal disease. The impairment of the autophagy of human renal tubular epithelial cells (HK-2 cells) is involved in the pathogenic mechanisms of DN. Sirtuin (Sirt)3 regulates the scavenging of damaged organelles and maintains energy balance. The present study aimed to examine the protective effects of Sirt3 on HK-2 cells stimulated by high glucose (HG). HK-2 cells were cultured in normal glucose (NG), HG or hyperosmotic medium. The viability of the HK-2 cells was detected using a Cell Counting Kit-8 assay. The expression and localization of Sirt3 were detected via immunofluorescence. Following transfection with an overexpression plasmid, the expression levels of key components in the Notch homolog 1 (Notch-1)/hairy and enhancer of split-1 (Hes-1) pathway and those of the autophagy-related proteins, Beclin-1, LC-3II and p62, were measured by western blot analysis and reverse transcription-quantitative PCR (RT-qPCR). As the Notch-1/Hes-1 pathway was inhibited, the expression levels of Beclin-1, LC-3II and p62 were also examined at transcriptional and translational level. It was found that prolonged culture in HG medium markedly reduced cell viability compared with the cells cultured in NG or in NG + mannitol, an effect that was aggravated with the increasing duration of culture. HG was capable of inhibiting the expression levels of Beclin-1, LC-3II and Sirt3, and upregulating p62 and the Notch-1/Hes-1 pathway, as verified by western blot analysis and RT-qPCR. The results of immunofluorescence staining revealed that HG decreased Sirt3 expression. Sirt3 reversed the HG-induced inhibition of the expression of Beclin-1 and LC-3II and the upregulation of p62. Moreover, Sirt3 reversed the HG-induced inhibition of the Notch-1/Hes-1 signaling pathway. However, this autophagy-promoting effect of Sirt3 was counteracted by the Notch-1/Hes-1 pathway activator. On the whole, the present study demonstrated that Sirt3 promoted the autophagy of HK-2 cells, at least partly, via the downregulation of Notch-1/Hes-1.

Knockdown of Nuclear lncRNAs by Locked Nucleic Acid (LNA) Gapmers in Nephron Progenitor Cells

Despite recent advance in our understanding on the role of long noncoding RNAs (lncRNAs), the function of the vast majority of lncRNAs remains poorly understood. To characterize the function of lncRNAs, knockdown studies are essential. However, the conventional silencing methods for mRNA, such as RNA interference (RNAi), may not be as efficient against lncRNAs, partly due to the mismatch of the localization of lncRNAs and RNAi machinery. To circumvent such limitation, a new technique has recently been developed, i.e., locked nucleic acid (LNA) gapmers. This system utilizes RNase H that distributes evenly in both nucleus and cytoplasm and is expected to knock down lncRNAs of interest more consistently regardless of their localization in the cell. In this chapter, we describe the procedure with tips to silence lncRNAs by LNA gapmers, by using mouse nephron progenitor cells as an example.

Cellular and Molecular Mechanisms of Kidney Development: From the Embryo to the Kidney Organoid

Development of the metanephric kidney is strongly dependent on complex signaling pathways and cell-cell communication between at least four major progenitor cell populations (ureteric bud, nephron, stromal, and endothelial progenitors) in the nephrogenic zone. In recent years, the improvement of human-PSC-derived kidney organoids has opened new avenues of research on kidney development, physiology, and diseases. Moreover, the kidney organoids provide a three-dimensional (3D) in vitro model for the study of cell-cell and cell-matrix interactions in the developing kidney. In vitro re-creation of a higher-order and vascularized kidney with all of its complexity is a challenging issue; however, some progress has been made in the past decade. This review focuses on major signaling pathways and transcription factors that have been identified which coordinate cell fate determination required for kidney development. We discuss how an extensive knowledge of these complex biological mechanisms translated into the dish, thus allowed the establishment of 3D human-PSC-derived kidney organoids.

Inhibition of the Numb/Notch signaling pathway increases radiation sensitivity in human nasopharyngeal carcinoma cells

Radiation therapy is the primary treatment for primary nasopharyngeal carcinoma (NPC). The aim of this study is to identify the effect of the Numb/Notch signaling pathway on radiation sensitivity in human NPC cells. NPC tissues and normal nasopharyngeal tissues were collected. To evaluate the regulatory effects of the Numb/Notch signaling pathway, NPC cells were subjected to radiotherapy and various doses of the Numb/Notch signaling pathway inhibitor gamma secretase inhibitor (GSI). Next, the expression of Notch and Numb proteins was determined in NPC tissues and normal nasopharyngeal tissues, and the correlation of Notch and Numb protein expression with the clinicopathological features of NPC tissues was analyzed. Then, the effect of radiotherapy on NPC cell survival rate, survival fraction, apoptosis rate, proliferation, migration, and invasion as well as Numb/Notch signaling pathway-related molecules was detected. The results demonstrated that the Numb/Notch signaling pathway was activated in NPC tissues. Following treatment with radiotherapy and GSI, the Numb/Notch signaling pathway was inhibited. In addition, the NPC cell survival rate, survival fraction, cell proliferation, migration, and invasion were decreased, whereas the colony number and apoptosis rate were increased. Following radiotherapy and GSI treatment, Numb expression was increased, whereas Notch1, Hes1, Jagged1, and c-Myc expression was decreased. However, the greatest difference was noted upon treatment with radiotherapy +15 μM GSI. The results reported in this study suggest that a high dose of the inhibitor of the Numb/Notch signaling pathway GSI increased the radiation sensitivity in human NPC cells.

Haploinsufficiency for the Six2 gene increases nephron progenitor proliferation promoting branching and nephron number

The regulation of final nephron number in the kidney is poorly understood. Cessation of nephron formation occurs when the self-renewing nephron progenitor population commits to differentiation. Transcription factors within this progenitor population, such as SIX2, are assumed to control expression of genes promoting self-renewal such that homozygous Six2 deletion results in premature commitment and an early halt to kidney development. In contrast, Six2 heterozygotes were assumed to be unaffected. Using quantitative morphometry, we found a paradoxical 18% increase in ureteric branching and final nephron number in Six2 heterozygotes, despite evidence for reduced levels of SIX2 protein and transcript. This was accompanied by a clear shift in nephron progenitor identity with a distinct subset of downregulated progenitor genes such as Cited1 and Meox1 while other genes were unaffected. The net result was an increase in nephron progenitor proliferation, as assessed by elevated EdU (5-ethynyl-2'-deoxyuridine) labeling, an increase in MYC protein, and transcriptional upregulation of MYC target genes. Heterozygosity for Six2 on an Fgf20-/- background resulted in premature differentiation of the progenitor population, confirming that progenitor regulation is compromised in Six2 heterozygotes. Overall, our studies reveal a unique dose response of nephron progenitors to the level of SIX2 protein in which the role of SIX2 in progenitor proliferation versus self-renewal is separable.

Autophagy is involved in mouse kidney development and podocyte differentiation regulated by Notch signalling

Podocyte dysfunction results in glomerular diseases accounted for 90% of end-stage kidney disease. The evolutionarily conserved Notch signalling makes a crucial contribution in podocyte development and function. However, the underlying mechanism of Notch pathway modulating podocyte differentiation remains less obvious. Autophagy, reported to be related with Notch signalling pathways in different animal models, is regarded as a possible participant during podocyte differentiation. Here, we found the dynamic changes of Notch1 were coincided with autophagy: they both increased during kidney development and podocyte differentiation. Intriguingly, when Notch signalling was down-regulated by DAPT, autophagy was greatly diminished, and differentiation was also impaired. Further, to better understand the relationship between Notch signalling and autophagy in podocyte differentiation, rapamycin was added to enhance autophagy levels in DAPT-treated cells, and as a result, nephrin was recovered and DAPT-induced injury was ameliorated. Therefore, we put forward that autophagy is involved in kidney development and podocyte differentiation regulated by Notch signalling.

In Vitro Propagation and Branching Morphogenesis from Single Ureteric Bud Cells

A method to maintain and rebuild ureteric bud (UB)-like structures from UB cells in vitro could provide a useful tool for kidney regeneration. We aimed in our present study to establish a serum-free culture system that enables the expansion of UB progenitor cells, i.e., UB tip cells, and reconstruction of UB-like structures. We found that fibroblast growth factors or retinoic acid (RA) was sufficient for the survival of UB cells in serum-free condition, while the proliferation and maintenance of UB tip cells required glial cell-derived neurotrophic factor together with signaling from either WNT-β-catenin pathway or RA. The activation of WNT-β-catenin signaling in UB cells by endogenous WNT proteins required R-spondins. Together with Rho kinase inhibitor, our culture system facilitated the expansion of UB tip cells to form UB-like structures from dispersed single cells. The UB-like structures thus formed retained the original UB characteristics and integrated into the native embryonic kidneys.

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FGFs and RA signaling sustain UB cell survival in serum-free culture condition

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WNT-β-catenin and RA signaling maintain the expansion of UB tip cells

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WNT proteins in UB cells activate WNT-β-catenin signaling through R-spondins

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Single UB cells form UB-like structures in vitro that integrate into native kidneys

Growth Factor Regulation in the Nephrogenic Zone of the Developing Kidney

New nephrons are induced by the interaction between mesenchymal progenitor cells and collecting duct tips, both of which are located at the outer edge of the kidney. This leading edge of active nephron induction is known as the nephrogenic zone. Cell populations found within this zone include collecting duct tips, cap mesenchyme cells, pretubular aggregates, nephrogenic zone interstitium, hemoendothelial progenitor cells, and macrophages. The close association of these dynamic progenitor cell compartments enables the intricate and synchronized patterning of the epithelial and the vascular components of the nephron. Understanding signaling interactions between the distinct progenitor cells of the nephrogenic zone are essential to determining the basis for new nephron formation, an important goal in regenerative medicine. A variety of technologies have been applied to define essential signaling pathways, including organ culture, mouse genetics, and primary cell culture. This chapter provides an overview of essential signaling pathways and discusses how these may be integrated.

Notch signaling promotes nephrogenesis by downregulating Six2

During nephrogenesis, multipotent mesenchymal nephron progenitors develop into distinct epithelial segments. Each nephron segment has distinct cell types and physiological function. In the current model of kidney development, Notch signaling promotes the formation of proximal tubules and represses the formation of distal tubules. Here, we present a novel role of Notch in nephrogenesis. We show in mice that differentiation of nephron progenitors requires downregulation of Six2, a transcription factor required for progenitor maintenance, and that Notch signaling is necessary and sufficient for Six2 downregulation. Furthermore, we find that nephron progenitors lacking Notch signaling fail to differentiate into any nephron segments, not just proximal tubules. Our results demonstrate how cell fates of progenitors are regulated by a transcription factor governing progenitor status and by a differentiation signal in nephrogenesis.

Summary: Notch is necessary and sufficient for downregulation of Six2 during nephrogenesis, while nephron progenitors that lack Notch signaling fail to form all segments of the nephron, not just proximal tubules.