Gene expression profiles in developing nephrons using Lim1 metanephric mesenchyme-specific conditional mutant mice

Kidney stones and moderate proteinuria as the rare manifestations of Gitelman syndrome

Background

Gitelman syndrome (GS) is an autosomal recessive inherited salt-losing tubulopathy (SLT). Here, we describe, for the first time, a case of GS without Gitelman-like features and with concomitant kidney stones, cysts and diabetic nephropathy (DN).

Case presentation

We described a male patient had a 19-year history of recurrent fatigue. From childhood, he had polydipsia and polyuria, paroxysmal tetany and palpitation. Serum biochemistry revealed chronic hypokalemia, metabolic alkalosis, normomagnesemia, mildly elevated Cr. Concomitant 24 h urine collection showed inappropriate renal potassium wasting, borderline hypercalciuria, moderate proteinuria consisting of major glomerular. Ultrasound of urinary tract showed bilateral and multiple kidney stones and cysts. Whole exome sequencing (WES) identified compound heterozygous mutations of SLC12A3. The unusual association of SLTs and glomerular proteinuria prompted us to perform a renal biopsy. Renal pathology showed renal involvement consistent with GS and early stage of diabetic nephropathy (DN). After treatment with KCl, magnesium oxide, perindopril and acarbose, the patient had been cured. The fatigue didn’t relapse.

Conclusion

GS had high variability of phenotype, GS may have no Gitelman-like features, kidney stones are not the exclusion criteria of GS. Renal biopsy should be warranted for GS patients with moderate to massive glomerular proteinuria.

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.

LHX3 is an advanced-stage prognostic biomarker and metastatic oncogene in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is a common cancer and exhibits high morbidity and mortality in the world. We recently identified LHX3 as a preferentially expressed gene with a possible involvement in HCC.

OBJECTIVE

To determine the expression, clinical relevance, prognostic significance and functions of LHX3 in HCC.

MATERIALS AND METHODS

LHX3 expression was assessed in 190 cancerous and 40 adjacent non-cancerous tissues by PCR, western blot and immunohistochemistry. Associations between LHX3 expression and clinicopathological characteristics of patients were investigated. Correlations between LHX3 expression and overall survival of patients were analyzed by Kaplan-Meier and Cox-regression methods. Functional roles of LHX3 were evaluated by transwell assays.

RESULTS

LHX3 expression is significantly increased in carcinoma tissues, and associated with clinical stage and metastasis of patients. LHX3 expression is much higher in the advanced-stage patients than the early-stage patients, and is sharply increased in metastasic patients. High LHX3 expression is associated with unfavorable overall survival, and is an independent prognostic factor of patients. Moreover, LHX3 is an unfavorable and independent prognostic factor unique to advanced-stage patients. Knockdown expression of LHX3 obviously inhibits tumor cell migration and invasion.

CONCLUSION

LHX3 is an advanced-stage prognostic biomarker, and acts as a new potential metastatic oncogene in HCC.

Insights from deconvolution of cell subtype proportions enhance the interpretation of functional genomic data

Cell subtype proportion variability between samples contributes significantly to the variation of functional genomic properties such as gene expression or DNA methylation. Although the impact of the variation of cell subtype composition on measured genomic quantities is recognized, and some innovative tools have been developed for the analysis of heterogeneous samples, most functional genomics studies using samples with mixed cell types still ignore the influence of cell subtype proportion variation, or just deal with it as a nuisance variable to be eliminated. Here we demonstrate how harvesting information about cell subtype proportions from functional genomics data can provide insights into cellular changes associated with phenotypes. We focused on two types of mixed cell populations, human blood and mouse kidney. Cell type prediction is well developed in the former, but not currently in the latter. Estimating the cellular repertoire is easier when a reference dataset from purified samples of all cell types in the tissue is available, as is the case for blood. However, reference datasets are not available for most other tissues, such as the kidney. In this study, we showed that the proportion of alterations attributable to changes in the cellular composition varies strikingly in the two disorders (asthma and systemic lupus erythematosus), suggesting that the contribution of cell subtype proportion changes to functional genomic properties can be disease-specific. We also showed that a reference dataset from a single-cell RNA-seq study successfully estimated the cell subtype proportions in mouse kidney and allowed us to distinguish altered cell subtype differences between two different knock-out mouse models, both of which had reported a reduced number of glomeruli compared to their wild-type counterparts. These findings demonstrate that testing for changes in cell subtype proportions between conditions can yield important insights in functional genomics studies.

A dual role of miR-22 in rhabdomyolysis-induced acute kidney injury

AIM

In acute kidney injury (AKI), regions of the kidney are hypoxic. However, for reasons yet unknown, adaptation to hypoxia through hypoxia-inducible factor (HIF) is limited. Here, we studied miR-22, a potential HIF repressor, in normal kidneys, as well as in rhabdomyolysis-induced AKI, a condition where miR-22 is up-regulated.

METHODS

AKI in mice was provoked by IM injection of glycerol. Tissue homogenates were processed to determine the levels of candidate RNAs and proteins, as well as global gene expression profiles. Reporter assays quantified in vitro miR-22 activity and its modulation by mimic or inhibitor molecules, under normoxia or hypoxia (1% O₂ ) respectively. In vivo, anti-miR-22 molecules were applied to normal mice or prior to induction of AKI. Renal outcome was assessed by measuring plasma creatinine, plasma urea and the levels of the injury markers Kim-1 and Ngal.

RESULTS

Renal miR-22 is inducible by hypoxia and represses hypoxia-inducible factor (HIF). Specific inhibition of miR-22 regulates 1913 gene transcripts in kidneys controls and 3386 in AKI, many of which are involved in development or carcinogenesis. Specific inhibition of miR-22 up-regulates tissue protective HIF target genes, yet renal function and injury markers are unchanged or worsened.

CONCLUSIONS

miR-22 is a HIF repressor constitutively expressed in the adult kidney and up-regulated in AKI. Specific inhibition of miR-22 is efficient in vivo and profoundly affects renal gene expression in health and disease, including up-regulation of HIF. However, the net effect on rhabdomyolysis-induced AKI outcome is neutral or even negative.

Effects of Cyclosporine A on the Development of Metanephros in the Pregnant BALB/c Mice

Background:

Cyclosporine A (CsA) is a commonly used clinical immunosuppressant. However, CsA exposure in rabbits during the gestation period was shown to cause a postnatal decrease in the number of nephrons, with the effects remaining unknown. In this study, we aimed to explore the effects of CsA on metanephros development in the pregnant BALB/c mice.

Methods:

Pregnant mice were randomly divided into two groups, and CsA (10 mg·kg⁻¹·d⁻¹) was subcutaneously injected from gestation day 10.5 to day 16.5 in the CsA group, whereas a comparable volume of normal saline was given to the control group. All of the mice were sacrificed on gestation day 17.5 and serum CsA concentration was measured. The fetuses were removed and weighed, and their kidneys were prepared for histological assessment and polymerase chain reaction assay. In an in vitro experiment, embryo kidneys of fetal mice on gestation day 12.5 were used, and CsA (10 μmol/L) was added in the culture of the CsA group. The growth pattern of the ureteric bud and nephrons was assessed by lectin staining.

Results:

No significant differences in the weight of embryo (4.54 ± 1.22 vs. 3.26 ± 1.09 mg) were observed between the CsA and control groups, the thickness of the cortical (510.0 ± 30.3 vs. 350.0 ± 29.7 μm, P < 0.05) and nephrogenic zone (272.5 ± 17.2 vs. 173.3 ± 24.0 μm, P < 0.05), and the number of glomeruli (36.5 ± 0.7 vs. 27.5 ± 2.1, P < 0.05) were reduced in the CsA group when compared to the control group. The cell proliferation of Ki-67 positive index between control and CsA group (307.0 ± 20.0 vs. 219.0 ± 25.0, P < 0.05) in the nephrogenic zone was decreased with the increase of apoptotic cells (17.0 ± 2.0 vs. 159.0 ± 33.0, P < 0.05). The mRNA expression of WT-1, Pax2, and Pax8 was downregulated by CsA treatment. As for the in vitro CsA group, the branch number of the ureteric bud was decreased in the CsA-treated group with the nephrons missing in contrast to control after the incubation for 24 h and 72 h (all P < 0.0001).

Conclusion:

Treatment of CsA suppressed metanephros development in the pregnant mice; however, the potential action of mechanism needs to be further investigated.

LHX3 is an early stage and radiosensitivity prognostic biomarker in lung adenocarcinoma

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer. We previously identified LHX3 as a new preferentially expressed gene in NSCLC. In the present study, we sought to determine its expression, the clinical relevance and the functional roles in NSCLC. LHX3 expression is sharply increased in carcinoma tissues compared to non-carcinoma tissues. Relational analysis reveals a significant association between LHX3 expression and clinical stage (n=172, P=0.032) or radiotherapy (n=167, P=0.022) of patients. LHX3 expression is much higher in the patients at advanced stages (stage III–IV) than in the patients at early stages (stage I–II, P=0.0304), and LHX3 expression is remarkably increased in the patients with radiotherapy treatment (P=0.0002). Survival analyses indicate that LHX3 is associated with unfavorable survival (n=180, P=0.002) and represents an independent prognostic factor [hazard ratio (HR)=1.834, P=0.004] of the NSCLC patients. Furthermore, LHX3 is associated with unfavorable overall survival (n=866, P=0.004) and represents an independent prognostic factor (HR=2.36, P=0.000) in lung adenocarcinoma (ADC) patients, but is not associated with overall survival of squamous cell carcinoma (SCC) patients (n=524, P=0.27). Further analyses found that LHX3 is an early-stage (n=94, P=0.003) and radiosensitivity (n=45, P=0.002) prognostic factor in ADC patients. The patients without radiotherapy have a significantly prolonged survival compared to those with radiotherapy (P=0.0069). Further functional studies show that forced expression of LHX3 in lung cancer cells obviously promotes cell proliferation and invasion, whereas inhibits cell apoptosis. In summary, LHX3 is an early-stage and radiosensitivity prognostic biomarker, and a novel potential oncogene in ADC.

Birefringence images of polycrystalline films of human urine in early diagnostics of kidney pathology

We propose an optical model of the Mueller-matrix description of mechanisms of optical anisotropy of polycrystalline films of urine, namely, optical activity and birefringence. The algorithm of reconstruction of distributions of parameters-optical rotation angles and phase shifts of the indicated anisotropy types-are elaborated upon. The objective criteria of differentiation of urine films taken from healthy donors and albuminuria patients by means of statistical analysis of such distributions are determined. The operational characteristics (sensitivity, specificity, and accuracy) of the Mueller-matrix reconstruction method of the optical anisotropy parameters are defined.

Histone deacetylase (HDAC) activity is critical for embryonic kidney gene expression, growth, and differentiation

Histone deacetylases (HDACs) regulate fundamental biological processes such as cellular proliferation, differentiation, and survival via genomic and nongenomic effects. This study examined the importance of HDAC activity in the regulation of gene expression and differentiation of the developing mouse kidney. Class I HDAC1-3 and class II HDAC4, -7, and -9 genes are developmentally regulated. Moreover, HDAC1-3 are highly expressed in nephron precursors. Short term treatment of cultured mouse embryonic kidneys with HDAC inhibitors (HDACi) induced global histone H3 and H4 hyperacetylation and H3K4 hypermethylation. However, genome-wide profiling revealed that the HDAC-regulated transcriptome is restricted and encompasses regulators of the cell cycle, Wnt/β-catenin, TGF-β/Smad, and PI3K-AKT pathways. Further analysis demonstrated that base-line expression of key developmental renal regulators, including Osr1, Eya1, Pax2/8, WT1, Gdnf, Wnt9b, Sfrp1/2, and Emx2, is dependent on intact HDAC activity. Treatment of cultured embryonic kidney cells with HDACi recapitulated these gene expression changes, and chromatin immunoprecipitation assays revealed that HDACi is associated with histone hyperacetylation of Pax2/Pax8, Gdnf, Sfrp1, and p21. Gene knockdown studies demonstrated that HDAC1 and HDAC2 play a redundant role in regulation of Pax2/8 and Sfrp1 but not Gdnf. Long term treatment of embryonic kidneys with HDACi impairs the ureteric bud branching morphogenesis program and provokes growth arrest and apoptosis. We conclude that HDAC activity is critical for normal embryonic kidney homeostasis, and we implicate class I HDACs in the regulation of early nephron gene expression, differentiation, and survival.

The rediscovery of uromodulin (Tamm-Horsfall protein): from tubulointerstitial nephropathy to chronic kidney disease

Uromodulin (Tamm-Horsfall protein) is the most abundant protein excreted in the urine under physiological conditions. It is exclusively produced in the kidney and secreted into the urine via proteolytic cleavage. Its biological function is still not fully understood. Uromodulin has been linked to water/electrolyte balance and to kidney innate immunity. Also, studies in knockout mice demonstrated that it has a protective role against urinary tract infections and renal stone formation. Mutations in the gene encoding uromodulin lead to rare autosomal dominant diseases, collectively referred to as uromodulin-associated kidney diseases. They are characterized by progressive tubulointerstitial damage, impaired urinary concentrating ability, hyperuricemia, renal cysts, and progressive renal failure. Novel in vivo studies point at intracellular accumulation of mutant uromodulin as a key primary event in the disease pathogenesis. Recently, genome-wide association studies identified uromodulin as a risk factor for chronic kidney disease (CKD) and hypertension, and suggested that the level of uromodulin in the urine could represent a useful biomarker for the development of CKD. In this review, we summarize these recent investigations, ranging from invalidation studies in mouse to Mendelian disorders and genome-wide associations, which led to a rediscovery of uromodulin and boosted the scientific and clinical interest for this long discovered molecule.

Lhx1 is required for specification of the renal progenitor cell field

In the vertebrate embryo, the kidney is derived from the intermediate mesoderm. The LIM-class homeobox transcription factor lhx1 is expressed early in the intermediate mesoderm and is one of the first genes to be expressed in the nephric mesenchyme. In this study, we investigated the role of Lhx1 in specification of the kidney field by either overexpressing or depleting lhx1 in Xenopus embryos or depleting lhx1 in an explant culture system. By overexpressing a constitutively-active form of Lhx1, we established its capacity to expand the kidney field during the specification stage of kidney organogenesis. In addition, the ability of Lhx1 to expand the kidney field diminishes as kidney organogenesis transitions to the morphogenesis stage. In a complimentary set of experiments, we determined that embryos depleted of lhx1, show an almost complete loss of the kidney field. Using an explant culture system to induce kidney tissue, we confirmed that expression of genes from both proximal and distal kidney structures is affected by the absence of lhx1. Taken together our results demonstrate an essential role for Lhx1 in driving specification of the entire kidney field from the intermediate mesoderm.

The fate of Notch-deficient nephrogenic progenitor cells during metanephric kidney development

To determine which nephron segments require Notch signals for development, we conditionally deleted Rbpj, a transcription factor required for canonical Notch signaling, in nephrogenic progenitors (NPs) of the metanephric mesenchyme. The retinoic acid receptor-β2 (Rarb2) promoter efficiently directed Cre-recombinase (Cre) activity to these progenitors. Conditional knockout of Rbpj in mice (Rarb2Cre(+)/Rbpj (f/-)) caused severe renal hypoplasia, as indicated by a 70-95% reduction in nephron number and the development of tubular cysts. To track the fate of NPs following Rarb2Cre expression, we labeled them with membrane-associated enhanced green fluorescent protein (GFP). In TomatoGFP(+)/Rarb2Cre(+) control mice, NPs differentiated into epithelia of all nephron segments, except into collecting ducts. In TomatoGFP(+)/Rarb2Cre(+)/Rbpj (f/-) conditional knockout mice, NPs developed into podocytes or distal tubular epithelia, indicating that canonical Notch signals were not required for mesenchymal-to-epithelial transition or for the specification of these nephron segments. Conversely, the few proximal tubules and associated cysts that developed in these mice were derived from the 5-10% of NPs that had failed to express Cre and, therefore, had intact Notch signaling. Thus, our fate mapping studies establish that the profound effect of Notch signaling on nephrogenesis is due to the specification of proximal but not distal tubules or podocytes.

Use of 12x/month haemoglobin monitoring with a computer algorithm reduces haemoglobin variability

BACKGROUND

Haemoglobin variability may be associated with increased death. Frequent haemoglobin monitoring may allow earlier detection of trends in haemoglobin slopes, alerting staff to intercurrent events. The more frequent haemoglobin values may provide early evidence of response to erythropoietin (EPO) doses, and allow more appropriate anaemia management. Our objective is to assess whether frequent haemoglobin monitoring data (12x/month) using a computer algorithm (AMIE, Leeds, UK) will reduce haemoglobin variability compared with 1x/month monitoring.

METHODS

We performed an observational case-control study of 44 unselected patients, comprising one dialysis facility measuring Crit-Line haemoglobin, lab haemoglobin, standard deviation of residuals as surrogate of haemoglobin variability and EPO dosing.

RESULTS

Haemoglobin variability and 'percent in target haemoglobin range' significantly improved with 12x/month haemoglobin results using a computer algorithm. There was also a non-significant trend toward for lower EPO doses.

CONCLUSION

Use of a computer algorithm to analyse 12x/month haemoglobin values provides early evidence of haemoglobin trends and allows more appropriate anaemia management, with decreased haemoglobin variability, lower EPO doses and more patients achieving target haemoglobin.

Transcriptional control of terminal nephron differentiation

Terminal differentiation of epithelial cells into more specialized cell types is a critical step in organogenesis. Throughout the process of terminal differentiation, epithelial progenitors acquire or upregulate expression of renal function genes and cease to proliferate, while expression of embryonic genes is repressed. This exquisite coordination of gene expression is accomplished by signaling networks and transcription factors which couple the external environment with the new functional demands of the cell. While there has been much progress in understanding the early steps involved in renal epithelial cell differentiation, a major gap remains in our knowledge of the factors that control the steps of terminal differentiation. A number of signaling molecules and transcription factors have been recently implicated in determining segmental nephron identity and functional differentiation. While some of these factors (the p53 gene family, hepatocyte nuclear factor-1beta) promote the terminal epithelial differentiation fate, others (Notch, Brn-1, IRX, KLF4, and Foxi1) tend to regulate differentiation of specific nephron segments and individual cell types. This review summarizes current knowledge related to these transcription factors and discusses how diverse cellular signals are integrated to generate a transcriptional output during the process of terminal differentiation. Since these transcriptional processes are accompanied by profound changes in nuclear chromatin structure involving the genes responsible for creating and maintaining the differentiated cell phenotype, future studies should focus on identifying the nature of these epigenetic events and factors, how they are regulated temporally and spatially, and the chromatin environment they eventually reside in.

Molecular insights into segmentation along the proximal-distal axis of the nephron

The structure of a mammalian kidney is parsed into large collections of polarized nephrons, and each segment is home to a diverse community of cells that specialize in renal endocrine and excretory functions. Early developmental lengthening and diversification of nephron segments along a proximal--distal axis initiate all subsequent facets of tubular growth and function. Morphogenic cues and biochemical interactions that are critical to this process are starting to emerge. The underlying principles of regional cell signaling and transcriptional control organizing early segmentation are the subject of this review.