The human kidney contains up to 2 million epithelial nephrons responsible for blood filtration. Regenerating the kidney requires the induction of the more than 20 distinct cell types required for ...excretion and the regulation of pH, and electrolyte and fluid balance. We have previously described the simultaneous induction of progenitors for both collecting duct and nephrons via the directed differentiation of human pluripotent stem cells. Paradoxically, although both are of intermediate mesoderm in origin, collecting duct and nephrons have distinct temporospatial origins. Here we identify the developmental mechanism regulating the preferential induction of collecting duct versus kidney mesenchyme progenitors. Using this knowledge, we have generated kidney organoids that contain nephrons associated with a collecting duct network surrounded by renal interstitium and endothelial cells. Within these organoids, individual nephrons segment into distal and proximal tubules, early loops of Henle, and glomeruli containing podocytes elaborating foot processes and undergoing vascularization. When transcription profiles of kidney organoids were compared to human fetal tissues, they showed highest congruence with first trimester human kidney. Furthermore, the proximal tubules endocytose dextran and differentially apoptose in response to cisplatin, a nephrotoxicant. Such kidney organoids represent powerful models of the human organ for future applications, including nephrotoxicity screening, disease modelling and as a source of cells for therapy.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
2.
Metabolic requirements of the nephron Cargill, Kasey; Sims-Lucas, Sunder
Pediatric nephrology (Berlin, West),
2020/1, Letnik:
35, Številka:
1
Journal Article
Recenzirano
The mammalian kidney is a complex organ that has several metabolically active cell types to aid in waste filtration, salt-water balance, and electrolyte homeostasis in the body. These functions are ...done primarily through the nephron, which relies on strict regulation of various metabolic pathways. Any deviations in the metabolic profile of nephrons or their precursor cells called nephron progenitors can lead to renal pathologies and abnormal development. Metabolism encompasses the mechanisms by which cells generate intermediate molecules and energy in the form of adenosine triphosphate (ATP). ATP is required by all cells and is mainly generated through glycolysis, fatty acid oxidation, and oxidative phosphorylation. During kidney development, self-renewing or proliferating cells rely on glycolysis to a greater extent than the other metabolic pathways to supply energy, replenish reducing equivalents, and generate nucleotides. However, terminally differentiated cell types rely more heavily on fatty acid oxidation and oxidative phosphorylation performed in the mitochondria to fulfill energy requirements. Further, the mature nephron is comprised of distinct segments and each segment utilizes metabolic pathways to varying degrees depending on the specific function. This review will focus on major metabolic processes performed by the nephron during health and disease.
The two major components of the kidney, the collecting system and the nephron, have different developmental histories. The collecting system arises by the reiterated branching of a simple epithelial ...tube, while the nephron forms from a cloud of mesenchymal cells that coalesce into epithelial vesicles. Each develops into a morphologically complex and highly differentiated structure, and together they provide essential filtration and resorption functions. In this review, we will consider their embryological origin and the genes controlling their morphogenesis, patterning, and differentiation, with a focus on recent advances in several areas.
Congenital abnormalities of the kidney and urinary tract are among the most common birth defects, affecting 3% of newborns. The human kidney forms around a million nephrons from a pool of nephron ...progenitors over a 30-week period of development. To establish a framework for human nephrogenesis, we spatially resolved a stereotypical process by which equipotent nephron progenitors generate a nephron anlage, then applied data-driven approaches to construct three-dimensional protein maps on anatomical models of the nephrogenic program. Single-cell RNA sequencing identified progenitor states, which were spatially mapped to the nephron anatomy, enabling the generation of functional gene networks predicting interactions within and between nephron cell types. Network mining identified known developmental disease genes and predicted targets of interest. The spatially resolved nephrogenic program made available through the Human Nephrogenesis Atlas (https://sckidney.flatironinstitute.org/) will facilitate an understanding of kidney development and disease and enhance efforts to generate new kidney structures.
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•Mouse and human kidneys undergo a conserved stereotypical developmental program•Transcriptomes were mapped to protein-based developmental models•Data predict lineage relationships in early human nephron development•View lineage and interaction predictions: https://sckidney.flatironinstitute.org/
Lindström et al. show that mouse and human nephrogenesis follow evolutionary conserved and stereotypical programs. Spatial mapping of transcriptional profiles predicts cell intermediates and regulatory interactions at play in development and disease. A web interface facilitates viewing and analysis of these findings.
Several studies have shown that total nephron (glomerular) number varies widely in normal human kidneys. Whereas the studies agree that average nephron number is approximately 900,000 to 1 million ...per kidney, numbers for individual kidneys range from approximately 200,000 to >2.5 million. Several studies have shown loss of glomeruli due to age-related glomerulosclerosis. The rates of loss vary among individuals depending upon blood pressure, diseases affecting the kidney, and other attributes of health, but most of the variation in nephron number is present at birth and is therefore developmentally determined. For example, in a relatively small study of nephron number in 15 children <3 months of age, we found that nephron number ranged from approximately 250,000 to 1.1 million. Given that no new nephrons are formed in human kidneys after approximately 36 weeks’ gestation, much interest has focused on renal function and health in individuals born with relatively low nephron endowment. Several studies have reported a direct correlation between birth weight and nephron number and an indirect association between nephron number and blood pressure. Associations between low birth weight and cardiovascular disease, including hypertension, have also been widely reported. This report provides an update on our current knowledge of human nephron number and the associations with adult health and disease.
Mammalian nephrons arise from a limited nephron progenitor pool through a reiterative inductive process extending over days (mouse) or weeks (human) of kidney development. Here, we present evidence ...that human nephron patterning reflects a time-dependent process of recruitment of mesenchymal progenitors into an epithelial nephron precursor. Progressive recruitment predicted from high-resolution image analysis and three-dimensional reconstruction of human nephrogenesis was confirmed through direct visualization and cell fate analysis of mouse kidney organ cultures. Single-cell RNA sequencing of the human nephrogenic niche provided molecular insights into these early patterning processes and predicted developmental trajectories adopted by nephron progenitor cells in forming segment-specific domains of the human nephron. The temporal-recruitment model for nephron polarity and patterning suggested by direct analysis of human kidney development provides a framework for integrating signaling pathways driving mammalian nephrogenesis.
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•Imaging shows gradual recruitment of progenitors into forming human/mouse nephrons•Single-cell RNA sequencing tracks cellular heterogeneity in human nephrogenesis•Divergent molecular trajectories generate distinct regions of the human nephron
During kidney development, mammalian nephrons arise from a limited progenitor pool through a reiterative inductive process. Lindström et al. demonstrate that human and mouse nephron patterning involves gradual mesenchymal progenitor cell recruitment into the epithelial nephron precursor. Recruitment timing predicts precursor cell position and eventual fate in functional nephron structures.
While nephron formation is known to be initiated by a mesenchyme-to-epithelial transition of the cap mesenchyme to form a renal vesicle (RV), the subsequent patterning of the nephron and fusion with ...the ureteric component of the kidney to form a patent contiguous uriniferous tubule has not been fully characterized. Using dual section in situ hybridization (SISH)/immunohistochemistry (IHC) we have revealed distinct distal/proximal patterning of Notch, BMP and Wnt pathway components within the RV stage nephron. Quantitation of mitoses and Cyclin D1 expression indicated that cell proliferation was higher in the distal RV, reflecting the differential developmental programs of the proximal and distal populations. A small number of RV genes were also expressed in the early connecting segment of the nephron. Dual ISH/IHC combined with serial section immunofluorescence and 3D reconstruction revealed that fusion occurs between the late RV and adjacent ureteric tip via a process that involves loss of the intervening ureteric epithelial basement membrane and insertion of cells expressing RV markers into the ureteric tip. Using
Six2-
eGFPCre
×
R26R-lacZ mice, we demonstrate that these cells are derived from the cap mesenchyme and not the ureteric epithelium. Hence, both nephron patterning and patency are evident at the late renal vesicle stage.
Nephrogenesis concludes by the 36th week of gestation in humans and by the third day of postnatal life in mice. Extending the nephrogenic period may reduce the onset of adult renal and cardiovascular ...disease associated with low nephron numbers. We conditionally deleted either Mtor or Tsc1 (coding for hamartin, an inhibitor of Mtor) in renal progenitor cells. Loss of one Mtor allele caused a reduction in nephron numbers; complete deletion led to severe paucity of glomeruli in the kidney resulting in early death after birth. By contrast, loss of one Tsc1 allele from renal progenitors resulted in a 25% increase in nephron endowment with no adverse effects. Increased progenitor engraftment rates ex vivo relative to controls correlated with prolonged nephrogenesis through the fourth postnatal day. Complete loss of both Tsc1 alleles in renal progenitors led to a lethal tubular lesion. The hamartin phenotypes are not dependent on the inhibitory effect of TSC on the Mtor complex but are dependent on Raptor.
The renin-angiotensin-aldosterone system (RAAS) is implicated in hypertension and kidney disease. The developing kidney can be programmed by various early-life insults by so-called renal programming, ...resulting in hypertension and kidney disease in adulthood. This theory is known as developmental origins of health and disease (DOHaD). Conversely, early RAAS-based interventions could reverse program processes to prevent a disease from occurring by so-called reprogramming. In the current review, we mainly summarize (1) the current knowledge on the RAAS implicated in renal programming; (2) current evidence supporting the connections between the aberrant RAAS and other mechanisms behind renal programming, such as oxidative stress, nitric oxide deficiency, epigenetic regulation, and gut microbiota dysbiosis; and (3) an overview of how RAAS-based reprogramming interventions may prevent hypertension and kidney disease of developmental origins. To accelerate the transition of RAAS-based interventions for prevention of hypertension and kidney disease, an extended comprehension of the RAAS implicated in renal programming is needed, as well as a greater focus on further clinical translation.
A balance between Six2-dependent self-renewal and canonical Wnt signaling-directed commitment regulates mammalian nephrogenesis. Intersectional studies using chromatin immunoprecipitation and ...transcriptional profiling identified direct target genes shared by each pathway within nephron progenitors. Wnt4 and Fgf8 are essential for progenitor commitment; cis-regulatory modules flanking each gene are cobound by Six2 and β-catenin and are dependent on conserved Lef/Tcf binding sites for activity. In vitro and in vivo analyses suggest that Six2 and Lef/Tcf factors form a regulatory complex that promotes progenitor maintenance while entry of β-catenin into this complex promotes nephrogenesis. Alternative transcriptional responses associated with Six2 and β-catenin cobinding events occur through non-Lef/Tcf DNA binding mechanisms, highlighting the regulatory complexity downstream of Wnt signaling in the developing mammalian kidney.
► Identification of gene regulatory networks in nephron progenitors ► Maintenance and commitment pathways integrated at cis-regulatory modules ► Multiple roles for β-catenin complexes in progenitor programs
Nephron progenitors must balance Six2-dependent self-renewal with Wnt/β-catenin-directed differentiation. Park et al. performed genome-wide analyses of target genes regulated by Six2 and β-catenin in these cells. Their work identifies key cis-regulatory nodes and defines distinct ways in which these transcriptional regulators interact and coordinate the control of kidney gene expression.
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