Development Of Human Fetal Kidney Research Articles

Immunoexpression Pattern of Autophagy-Related Proteins in Human Congenital Anomalies of the Kidney and Urinary Tract.

The purpose of this study was to evaluate the spatiotemporal immunoexpression pattern of microtubule-associated protein 1 light chain 3 beta (LC3B), glucose-regulated protein 78 (GRP78), heat shock protein 70 (HSP70), and lysosomal-associated membrane protein 2A (LAMP2A) in normal human fetal kidney development (CTRL) and kidneys affected with congenital anomalies of the kidney and urinary tract (CAKUT). Human fetal kidneys (control, horseshoe, dysplastic, duplex, and hypoplastic) from the 18th to the 38th developmental week underwent epifluorescence microscopy analysis after being stained with antibodies. Immunoreactivity was quantified in various kidney structures, and expression dynamics were examined using linear and nonlinear regression modeling. The punctate expression of LC3B was observed mainly in tubules and glomerular cells, with dysplastic kidneys displaying distinct staining patterns. In the control group's glomeruli, LAMP2A showed a sporadic, punctate signal; in contrast to other phenotypes, duplex kidneys showed significantly stronger expression in convoluted tubules. GRP78 had a weaker expression in CAKUT kidneys, especially hypoplastic ones, while normal kidneys exhibited punctate staining of convoluted tubules and glomeruli. HSP70 staining varied among phenotypes, with dysplastic and hypoplastic kidneys exhibiting stronger staining compared to controls. Expression dynamics varied among observed autophagy markers and phenotypes, indicating their potential roles in normal and dysfunctional kidney development.

Aberrations in FGFR1, FGFR2, and RIP5 Expression in Human Congenital Anomalies of the Kidney and Urinary Tract (CAKUT).

This study aimed to explore the spatio-temporal expression patterns of congenital anomalies of kidney and urinary tract (CAKUT) candidate genes, Fibroblast Growth Factor Receptor 1 (FGFR1), Fibroblast Growth Factor Receptor 2 (FGFR2) and Receptor-Interacting Protein Kinase 5 (RIP5), in human fetal kidney development (CTRL) and kidneys affected with CAKUT. Human fetal kidneys from the 22nd to 41st developmental week (duplex, hypoplastic, dysplastic, and controls) were stained with antibodies and analyzed by epifluorescence microscopy and RT-qPCR. The effect of CAKUT candidate genes on kidney nephrogenesis and function is confirmed by statistically significant variations in the spatio-temporal expression patterns of the investigated markers. The nuclear localization of FGFR1, elevated expression score of FGFR1 mRNA, the increased area percentage of FGFR1-positive cells in the kidney cortex, and the overall decrease in the expression after the peak at the 27th developmental week in dysplastic kidneys (DYS), suggest an altered expression pattern and protein function in response to CAKUT pathophysiology. The RT-qPCR analysis revealed a significantly higher FGFR2 mRNA expression score in the CAKUT kidneys compared to the CTRL. This increase could be due to the repair mechanism involving the downstream mediator, Extracellular Signal-Regulated Kinase 1/2 (ERK1/2). The expression of RIP5 during normal human kidney development was reduced temporarily, due to urine production and increased later since it undertakes additional functions in the maturation of the postnatal kidney and homeostasis, while the expression dynamics in CAKUT-affected kidneys exhibited a decrease in the percentage of RIP5-positive cells during the investigated developmental period. Our findings highlight the importance of FGFR1, FGFR2, and RIP5 as markers in normal and pathological kidney development.

Characterization of alternative mRNA splicing in cultured cell populations representing progressive stages of human fetal kidney development

Nephrons are the functional units of the kidney. During kidney development, cells from the cap mesenchyme—a transient kidney-specific progenitor state—undergo a mesenchymal to epithelial transition (MET) and subsequently differentiate into the various epithelial cell types that create the tubular structures of the nephron. Faults in this transition can lead to a pediatric malignancy of the kidney called Wilms’ tumor that mimics normal kidney development. While human kidney development has been characterized at the gene expression level, a comprehensive characterization of alternative splicing is lacking. Therefore, in this study, we performed RNA sequencing on cell populations representing early, intermediate, and late developmental stages of the human fetal kidney, as well as three blastemal-predominant Wilms’ tumor patient-derived xenografts. Using this newly generated RNAseq data, we identified a set of transcripts that are alternatively spliced between the different developmental stages. Moreover, we found that cells from the earliest developmental stage have a mesenchymal splice-isoform profile that is similar to that of blastemal-predominant Wilms’ tumor xenografts. RNA binding motif enrichment analysis suggests that the mRNA binding proteins ESRP1, ESRP2, RBFOX2, and QKI regulate alternative mRNA splicing during human kidney development. These findings illuminate new molecular mechanisms involved in human kidney development and pediatric kidney cancer.

The Rhesus Macaque Serves As a Model for Human Lateral Branch Nephrogenesis.

Most nephrons are added in late gestation. Truncated extrauterine nephrogenesis in premature infants results in fewer nephrons and significantly increased risk for CKD in adulthood. To overcome the ethical and technical difficulties associated with studies of late-gestation human fetal kidney development, third-trimester rhesus macaques served as a model to understand lateral branch nephrogenesis (LBN) at the molecular level. Immunostaining and 3D rendering assessed morphology. Single-cell (sc) and single-nucleus (sn) RNA-Seq were performed on four cortically enriched fetal rhesus kidneys of 129-131 days gestational age (GA). An integrative bioinformatics strategy was applied across single-cell modalities, species, and time. RNAScope validation studies were performed on human archival tissue. Third-trimester rhesus kidney undergoes human-like LBN. scRNA-Seq of 23,608 cells revealed 37 transcriptionally distinct cell populations, including naïve nephron progenitor cells (NPCs), with the prior noted marker genes CITED1, MEOX1, and EYA1 (c25). These same populations and markers were reflected in snRNA-Seq of 5972 nuclei. Late-gestation rhesus NPC markers resembled late-gestation murine NPC, whereas early second-trimester human NPC markers aligned to midgestation murine NPCs. New, age-specific rhesus NPCs (SHISA8) and ureteric buds (POU3F4 and TWIST) predicted markers were verified in late-gestation human archival samples. Rhesus macaque is the first model of bona fide LBN, enabling molecular studies of late gestation, human-like nephrogenesis. These molecular findings support the hypothesis that aging nephron progenitors have a distinct molecular signature and align to their earlier human counterparts, with unique markers highlighting LBN-specific progenitor maturation.

Single-cell transcriptomics reveals gene expression dynamics of human fetal kidney development.

The current understanding of mammalian kidney development is largely based on mouse models. Recent landmark studies revealed pervasive differences in renal embryogenesis between mouse and human. The scarcity of detailed gene expression data in humans therefore hampers a thorough understanding of human kidney development and the possible developmental origin of kidney diseases. In this paper, we present a single-cell transcriptomics study of the human fetal kidney. We identified 22 cell types and a host of marker genes. Comparison of samples from different developmental ages revealed continuous gene expression changes in podocytes. To demonstrate the usefulness of our data set, we explored the heterogeneity of the nephrogenic niche, localized podocyte precursors, and confirmed disease-associated marker genes. With close to 18,000 renal cells from five different developmental ages, this study provides a rich resource for the elucidation of human kidney development, easily accessible through an interactive web application.

Dissecting the Global Dynamic Molecular Profiles of Human Fetal Kidney Development by Single-Cell RNA Sequencing

Healthy renal function depends on normal nephrogenesis during embryonic development. However, a comprehensive gene expression profile of human fetal kidney development remains largely unexplored. Here, using a single-cell RNA-sequencing technique, we analyzed >3,000 human fetal renal cells spanning 4months of development in utero. Unsupervised analysis identified two progenitor subtypes during cap mesenchyme development, suggesting a mechanism for sustaining their progenitor states. Furthermore, we identified critical transcriptional regulators and signaling pathways involved in the segmentation of nephron tubules. We explored the development of the highly heterogeneous collecting duct epithelia and dissected the metabolic gene repertoire and the extracellular matrix composition of the glomerular mesangium. The results provide insights on the molecular basis and regulatory events in human renal development. Moreover, thecell-type-specific expression features of causal genes in congenital renal diseases may be helpful in the treatment of these diseases.

Stereological study of developing glomerular forms during human fetal kidney development.

Human fetal kidney development is a complex and stepwise process. The number, shape, size and distribution of glomeruli provide important information on kidney organization. The aim of this study was to quantify glomerular developing forms during human fetal kidney development using stereological methods. Kidney tissue specimens of 40 human fetuses with gestational ages ranging from 9 to 40weeks were analyzed. Specimens were divided into eight groups based on gestational age, each corresponding to 1 lunar month. Stereological methods were used at the light microscopy level to estimate volume, surface and numerical density of the glomerular developing forms. During gestation, nephrogenesis continually advanced, and the number of nephrons increased. Volume, surface and numerical densities of vesicular forms and S-shaped bodies decreased gradually in parallel with gradual increases in estimated stereological parameters for vascularized glomeruli. Volume density and surface density of vascularized glomeruli increased gradually during fetal kidney development, and numerical density increased until the seventh lunar month. A relative decrease in vascularized glomeruli per unit volume of cortex occurred during the last 3 lunar months. Nephrogenesis began to taper off by 32weeks and was completed by 36weeks of gestation. The last sample in which we observed vesicles was from a fetus aged 32weeks, and the last sample with S-shaped bodies was from a fetus aged 36weeks. The present study is one of few quantitative studies conducted on human kidney development. Knowledge of normal human kidney morphogenesis during development could be important for future medical practice. Events occurring during fetal life may have significant consequences later in life.

Dependence of Renal Microvessel Density on Angiotensin II

During renal development, coordinate positioning and lengthening of the postglomerular microvasculature takes place as the tubular compartment expands and lengthens to form the renal papilla.1 The three-dimensional relationship of peritubular capillaries and vasa rectae to their specific nephron segments1,2 is essential for effective water and solute reabsorption in balance with glomerular filtration,3 for regulated salt excretion through the pressure natriuresis mechanism,4,5 and for formation of hypertonic urine.6,7 Conversely, rarefaction of the peritubular vasculature associated with tubulointerstitial fibrosis is a hallmark of chronic allograft nephropathy8 and probably most other progressive renal diseases.9,10 Hence, there is an obvious need to understand mechanisms that control the formation and maintenance of the peritubular vasculature. In this issue of JASN , Madsen et al. 11 describe the critical importance of signaling through angiotensin receptor 1 (ATR1) for development of a normal density and position of the postglomerular renal microvasculature. They administered the angiotensin II (AngII) receptor antagonist candesartan during the first 2 postnatal weeks in rat pups, a window that corresponds roughly to gestational weeks 24 through 36 for human fetal kidney development, and found a dramatic reduction in peritubular microvessel density. The reduced microvessel density accompanies a dramatic and very specific reduction of inner medulla size and …

Prenatal Magnetic Resonance Imaging Demonstrates Linear Growth of the Human Fetal Kidneys During Gestation

Although fetal kidneys have only 10% of their postnatal blood flow, fetal renal development is essential for normal postnatal function. In addition, to our knowledge it is unknown whether human fetal kidney development follows a linear or exponential evolution. We created normative magnetic resonance imaging curves for the kidney prenatal growth pattern in relation to gestational age. A total of 142 human fetuses at between 20 and 36 weeks of gestation underwent prenatal magnetic resonance imaging for nonurological pathology (pulmonary, cerebral or maternal abnormalities). Twins, urinary tract abnormalities, oligohydramnios or anhydramnios were excluded. T2-weighted images (single shot turbo spin-echo) were used to measure kidney variables. Bipolar and anteroposterior diameters of the 2 kidneys were measured and correlated with gestational age using linear regression analysis. A linear relationship of the bipolar and anteroposterior diameters was found according to gestational age in weeks (p <0.0001). No substantial differences between growth of the left and right fetal kidneys was identified. Bipolar length of the human fetal kidney increases at an average rate of 1.24 mm per week of gestation, while anteroposterior diameter increases at 0.57 mm per week of gestation between weeks 20 and 36. This indicates that bipolar diameter increases twice as rapidly as anteroposterior diameter. Regression analysis curves showed a good fit to the measured data points (anteroposterior and bipolar measurements R2 = 0.36 and 0.58, respectively). The CIs of function variables were small, enabling their use as normative curves. This prenatal magnetic resonance imaging study demonstrates linear growth of the bipolar and anteroposterior diameters of human fetal kidneys in relation to gestational age. In addition, it is clear that bipolar diameter grows twice as rapidly as anteroposterior diameter and there is less variability for bipolar diameter. These normative curves may allow us to detect abnormal fetal evolution.

Changes of the glomerular size during the human fetal kidney development

Newborns adaptation on postnatal conditions includes significant morphological and functional renal changes. Every kidney contains a constant number of nephrons, at the end of the nephrogenesis period, which extends from week 8 to 34 of gestation. Mature juxtamedullary nephrons possess higher filtration capacity than primitive superficial nephrons, which have insufficient vascularization. The objective of the study was to calculate an average glomerular diameter in cortical zones of the kidney during development, to define periods of their most intensive growth, and to record differences of glomerular size between different cortical zones. A total of 30 human fetal kidneys aged from IV to X lunar months were analyzed. Stereological methods were used for calculating the average glomerular diameter in superficial, intermediate and juxtamedullary zone of the kidney cortex. Glomeruli in the superficial cortical zone had the lowest average diameter. The average glomerular diameter continually increased from IV lunar month (0.057 +/- 0.004 mm) to X lunar month (0.082 +/- 0.004 mm), with highly significant correlation with gestational age (r=0.755; p<0.01). The average glomerular diameter in the intermediate zone increased from 0.081 +/- 0.004 mm (IV lunar month) to 0.096 +/- 0.004 mm (X lunar month) with low linear correlation with gestational age (r=0.161). Juxtamedullary glomeruli were the biggest ones. Their average diameter, during the IV LM ranged from 0.093 +/- 0.006 mm to 0.101 +/- 0.004 mm. In the newborns (X lunar month), juxtamedullary glomeruli had spherical structures with an average diameter of 0.103 +/- 0.004 mm, and low negative correlation (r=-0.032) with gestational age. In the IV and V lunar months of gestation, there was significant difference (p<0.01; p<0.05) between the average glomerular diameter in the different zones of the kidney cortex. Superficial glomeruli had the smallest diameter, while juxtamedullary glomeruli were the largest. The average glomerular diameter increased during intrauterine development in all zones, most intensive in the X lunar month. There was a significant difference of the glomeruli between different cortical zones in the young fetuses. Such significant difference receded as gestational age increased.

Evaluation of absolute volume of human fetal kidney's cortex and medulla during gestation

Human fetal kidney is quite different from the mature kidney, both macroscopically and hystologically. Lobulated surface of the human fetal kidney reflects its inner organisation. To determine the fetal kidneys' volume according to the gestational age, to establish periods of their maximal and minimal growth and to compare these values for various gestational ages. Forty five human fetal kidneys aged from IV to X lunar months were analyzed. Kidneys were divided into nine groups according to their gestational age. The volumes of cortex and medulla were determined using stereological methods. The results were statistically analyzed and the periods of significant growth of these structures were marked. Fetal kidney's cortex and medulla grew continually with a very high coefficient of linear correlation with crown-rump length. The cortex/medulla ratio was minimal in the first half of V lunar month, when medulla grew most rapidly and it was maximal immediately before birth, when cortex achieved its maximum. This study was an effort to provide some parameters which would help in the future investigations of the development of human fetal kidney.

Quantitative analysis of the nephron during human fetal kidney development

The development of human kidney is a complex process. The number, shape, size, and distribution of nephrons as functional units in a kidney, provide some important information about the organization of the kidney. The aim of this study was to extend the knowledge of the developing human kidney by studying nephrons in the kidney's cortex during gestation. Kidney tissue specimens of 32 human fetuses, the gestational age from IV lunar month (LM IV) to LM X, were analysed. Specimens were divided in ten groups based on gestational age. Stereological methods were used at the light microscopic level to estimate the volume densities of the corpuscular and tubular components of the nephron in the cortex of the developing human kidney. Nephron polymorphism was the main characteristic of the human fetal kidney during development. In younger fetuses, just below the renal capsule, there was a wide nephrogenic zone. It contained the condensed mesenchyme and terminal ends of the ureteric bud. Nephrons, in the different stages of development, were located around the ureteric bud which branched in the cortical nephrogenic zone and induced nephrogenesis. More mature nephrons were located in the deeper part of the cortex, close to the juxta-medullary junction. During gestation, nephrogenesis continually advanced, and the number of nephrons increased. Glomeruli changed their size and shape, while the tubules changed their length and convolution. Renal cortex became wider and contained the more mature glomeruli and the more convoluted tubules. The volume density of the tubular component of the nephron increased continually from 10.53% (LM IVa) to 27.7% (LM X). Renal corpuscles changed their volume density irregularly during gestation, increasing from 13% (LM IVa) to 15.5% (LM IVb). During the increase of gestational age, the volume density of corpuscular component of the nephron decreased to 11.7% (LM VIII), then went on increasing until the end of the intrauterine development (LM X) when corpuscles occupied 16.73% of the cortical volume. The volume density of the developing nephrons (corpuscular and tubular portion) showed the significant positive correlation (r = 0.85; p<0.01) with gestational age. The present study was one of few quantitative studies of the human developing nephron. Knowledge about the normal development of the human kidney should be important for the future medical practice.

Development of human fetal kidney in obstructive uropathy: Correlations with ultrasonography and urine biochemistry

In utero urethral obstruction results in bilateral hydronephrosis and severe fetal and post-natal morbidity and mortality. Obstetrical management depends on the indirect evaluation of fetal renal function by ultrasonography and biochemical analysis. No direct evaluation of the severity and possible reversibility of renal lesions is available. In this paper we analyzed kidneys from 34 fetuses (14 to 37 gestational weeks) in which (1) isolated bilateral urinary tract obstruction had been detected in utero by sonography, and (2) the severity of sonographic and biochemical prognostic indicators led to the indication of termination of pregnancy or to perinatal death. Pure hydronephrosis was observed in two young fetuses [14 and 20 gestational weeks (GW)] and was associated with regressive changes in two others. In contrast, a wide spectrum of dysplastic renal lesions was present in 30 fetuses and was classified into four subgroups according to the association of dysplasia, hypoplasia and cysts. They had the following characteristics in common: (1) premature cessation of nephrogenesis assessed by the medullary ray counting method; (2) early disappearance or myofibroblastic differentiation of metanephric blastema; (3) early increase in interstitial mesenchyme with widespread expression of alpha-smooth muscle actin by mesenchymal cells; (4) frequent absence of classical criteria of dysplasia (nests of cartilage were observed in only 5 fetuses); (5) an identification, based upon the detection of alpha-smooth muscle actin expression, of the muscular phenotype of mesenchymal cells encircling primitive ducts. In conclusion, (1) the value of prognostic markers in fetuses less than 20 GW should be reconsidered; (2) after 20 GW there is a good correlation between markers predicting poor prognosis and the severity of renal lesions; (3) hypoplasia with disappearance of blastema cells, dysplasia and early interstitial fibrosis are evidence of the irreversibility of renal lesions and preclude any possibility of new nephron formation; (4) these findings suggest that most surgical in utero procedures are performed when irreversible renal lesions have developed.

Expression of transforming growth factor-α and epidermal growth factor receptor in human fetal kidneys

Beginning at the fifth week of fetal life, successive generations of individual nephrons are induced by contact between metanephric mesenchyme and ureteric bud. Following phenotypic transformation, cells of each primitive renal vesicle undergo a phase of rapid cell division. In order to identify genes which might regulate nephron development in man, we screened adult and fetal kidney RNA for expression of a panel of growth-related genes. Among the genes which were expressed at higher levels in fetal kidney was the epidermal growth factor (EGF) receptor. There is controversy as to the most likely physiologic EGF receptor ligand in fetal kidney; we were able to identify a transcript for transforming growth factor-α (TGF-α) but not EGF on Northern blots of fetal kidney RNA. Since the abundance of TGF-α mRNA is low, we confirmed its presence by polymerase chain reaction amplification. Using specific radioimmunoas-says, we also provide direct evidence for TGF-α but not EGF peptide in extracts of fetal kidney and mid-gestational amniotic fluid. We suggest that TGF-α/EGF receptor interactions may serve an important function in development of human fetal kidney.

Growth and development of the human fetal kidney.

Growth and development of human fetal kidney was studied with respect to anthropometric measurements, histological appearance and certain functional parameters. Upto 30 weeks of gestational age there was a proportional growth of the kidneys in respect of gestational age. The formation of the glomerular capsule was by a process of sequential development of the endo and epithelial cells rather than by an invaginative process. There comes a time in the development of the kidney when the developing nephrons appear to lie in pools of blood. Glomerular filtration appears earlier than tubular reabsorption. The process of tubular secretion was found to be associated with induction of specific proteins.