Evidence that lymphangiomyomatosis is caused by TSC2 mutations: chromosome 16p13 loss of heterozygosity in angiomyolipomas and lymph nodes from women with lymphangiomyomatosis.

Lymphangiomyomatosis (LAM) is a rare disease, of unknown etiology, affecting women almost exclusively. Lung transplantation is the only consistently effective therapy for LAM. Microscopically, LAM consists of a diffuse proliferation of smooth muscle cells. LAM can occur without evidence of other disease (referred to as "sporadic LAM") or in association with tuberous sclerosis complex (TSC). TSC is an autosomal dominant tumor suppressor gene syndrome characterized by seizures, mental retardation, and tumors in the brain, heart, skin, and kidney. Renal angiomyolipomas occur in approximately 50% of sporadic LAM patients and in 70% of TSC patients. Loss of heterozygosity (LOH) in the chromosomal region for the TSC2 gene occurs in 60% of TSC-associated angiomyolipomas. Because of the similar pulmonary and renal manifestations of TSC and sporadic LAM, we hypothesized that LAM and TSC have a common genetic basis. We analyzed renal angiomyolipomas, from 13 women with sporadic LAM, for LOH in the regions of the TSC1 (chromosome 9q34) and TSC2 (chromosome 16p13) genes. TSC2 LOH was detected in seven (54%) of the angiomyolipomas. We also found TSC2 LOH in four lymph nodes from a woman with retroperitoneal LAM. No TSC1 LOH was found. Our findings indicate that the TSC2 gene may be involved in the pathogenesis of sporadic LAM. However, genetic transmission of LAM has not been reported. Women with LAM may have low-penetrance germ-line TSC2 mutations, or they may be mosaic, with TSC2 mutations in the lung and the kidney but not in other organs.     

Is Urinary Lipoarabinomannan the Result of Renal Tuberculosis? Assessment of the Renal Histology in an Autopsy Cohort of Ugandan HIV-Infected Adults

Objective

The detection of urinary lipoarabinomannan (LAM), a mycobacterial cell wall component, is used to diagnose tuberculosis (TB). How LAM enters the urine is not known. To investigate if urinary LAM-positivity is the result of renal TB infection we correlated the outcomes of urinary LAM-antigen testing to renal histology in an autopsy cohort of hospitalized, Ugandan, HIV-infected adults.

Methods

We performed a complete autopsy, including renal sampling, in HIV-infected adults that died during hospitalization after written informed consent was obtained from the next of kin. Urine was collected postmortem through post-mortem catheterisation or by bladder puncture and tested for LAM with both a lateral flow assay (LFA) and an ELISA assay. Two pathologists assessed the kidney histology. We correlated the LAM-assay results and the histology findings.

Results

Of the 13/36 (36%) patients with a positive urinary LAM ELISA and/or LFA, 8/13 (62%) had renal TB. The remaining 5 LAM-positive patients had disseminated TB without renal involvement. Of the 23 LAM-negative patients, 3 had disseminated TB without renal involvement. The remaining LAM-negative patients had no TB infection and died mostly of fungal and bacterial infections. LAM LFA had a sensitivity of 81% and specificity of 100% to diagnose TB at any location, and the LAM ELISA a sensitivity of 63% and a specificity of 100%. 54% (7/13) LAM LFA-positive patients were not on anti-TB treatment at the time of death.

Conclusion

Renal TB infection explained LAM-positivity in the majority of patients. Patients with disseminated TB without renal involvement can also be diagnosed with LAM. This suggests that other mechanisms that lead to urinary LAM-positivity exist in a minority of patients.     

Estradiol and tamoxifen stimulate LAM-associated angiomyolipoma cell growth and activate both genomic and nongenomic signaling pathways

Lymphangioleiomyomatosis (LAM) is a progressive lung disease affecting almost exclusively women. The reasons for this strong gender predisposition are poorly understood. Renal angiomyolipomas occur in 50-60% of sporadic LAM patients. The smooth muscle cells of pulmonary LAM and renal angiomyolipomas are nearly indistinguishable morphologically. Here, we report the first successful cell culture of a LAM-associated renal angiomyolipoma. The cells carried inactivating mutations in both alleles of the TSC2 gene and expressed estrogen receptor , estrogen receptor , and androgen receptor. To elucidate the cellular pathways through which steroid hormones influence LAM pathogenesis, we treated the cells with both estradiol and tamoxifen. Cell growth was stimulated by estradiol, associated with phosphorylation of p44/42 MAPK at 5 min and an increase in c-myc expression at 4 h. Tamoxifen citrate also stimulated cell growth, associated with increased phosphorylation of p44/42 MAPK and expression of c-myc, indicating that tamoxifen has agonist effects on angiomyolipoma cells. This response to tamoxifen in human angiomyolipoma cells differs from prior studies of Eker rat leiomyoma cells, possibly reflecting cell type or species differences in cells lacking tuberin. Our data provide the first evidence that estradiol stimulates the growth of angiomyolipoma cells, that tamoxifen has agonist effects in angiomyolipoma cells, and that estradiol and tamoxifen impact both genomic and nongenomic signaling pathways in angiomyolipoma cells. The responsiveness of angiomyolipoma cells to estradiol may be related to the underlying reasons that LAM affects primarily women.     

Risk of breast cancer in patients with lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare metastasizing pulmonary disease that shares some clinical, cellular, and molecular similarities with metastatic breast cancer to lung. LAM cells have been identified circulating in various body fluids of patients and, intriguingly, diverse evidence indicates that these cells may originate from a different organ to the lung. Following on from these observations, we hypothesized the existence of a common risk basis between LAM and breast cancer, and suggested increased risk of breast cancer among LAM patients. Here, by studying two additional LAM cohorts with more detailed epidemiological, life-style, and disease-related data, we show consistent results; a potential excess of estrogen-receptor-positive young breast cancer cases in LAM. This observation further suggests the need of prospective studies to precisely assess the association between both diseases.     

Lipoarabinomannans: from structure to biosynthesis

Mycobacterium tuberculosis, the causative agent of tuberculosis, is one of the most effective human pathogens and the molecular basis of its virulence remains poorly understood. Here, we review our current knowledge about the structure and biosynthesis of the mycobacterial cell-wall lipoglycans, lipoarabinomannans (LAM). LAM are ubiquitous of mycobacteria and appear as the most potent non-peptidic molecules to modulate the host immune response. Nevertheless, LAM structure differs according to the mycobacterial species and three types of LAM have been described: mannose-capped LAM (ManLAM), phospho-myo-inositol-capped LAM (PILAM) and non-capped LAM (AraLAM). The type of capping is a major structural feature determining the ability of LAM to modulate the immune response. ManLAM, found in slow-growing mycobacteria, such as M. tuberculosis, have been demonstrated to be powerful anti-inflammatory molecules and emerge as key virulence factors that may be relevant drug targets. LAM-like molecules are not only confined to mycobacteria but are also present in actinomycetes (including the genera Rhodococcus, Corynebacterium or Gordonia). This offers the possibility of comparative studies that should help in deciphering the structure-function relationships and biosynthesis of these complex molecules in the future.     

Renal organogenesis

The increasing prevalence of chronic kidney disease in the absence of new treatment modalities has become a strong driver for innovation in nephrology. An increasing understanding of stem cell biology has kindled the prospects of regenerative options for kidney disease. However, the kidney itself is not a regenerative organ, as all the nephrons are formed during embryonic development. Here, we will investigate advances in the molecular genetics of renal organogenesis, including what this can tell us about lineage relationships, and discuss how this may serve to inform us about both the normal processes of renal repair and options for regenerative therapies.     

Renal organogenesis: What can it tell us about renal repair and regeneration?

The increasing prevalence of chronic kidney disease in the absence of new treatment modalities has become a strong driver for innovation in nephrology. An increasing understanding of stem cell biology has kindled the prospects of regenerative options for kidney disease. However, the kidney itself is not a regenerative organ, as all the nephrons are formed during embryonic development. Here, we will investigate advances in the molecular genetics of renal organogenesis, including what this can tell us about lineage relationships, and discuss how this may serve to inform us about both the normal processes of renal repair and options for regenerative therapies.     

Gene expression analysis in LLC-PK1 renal tubular cells by atrial natriuretic peptide (ANP): correlation of homologous human genes with renal response

We used human DNA microarray to explore the differential gene expression profiling of atrial natriuretic peptide (ANP)-stimulated renal tubular epithelial kidney cells (LLC-PK1) in order to understand the biological effect of ANP on renal kidney cell's response. Gene expression profiling revealed 807 differentially expressed genes, consisting of 483 up-regulated and 324 down-regulated genes. The bioinformatics tool was used to gain a better understanding of differentially expressed genes in porcine genome homologous with human genome and to search the gene ontology and category classification, such as cellular component, molecular function and biological process. Four up-regulated genes of ATP1B1, H3F3A, ITGB1 and RHO that were typically validated by real-time quantitative PCR (RT-qPCR) analysis serve important roles in the alleviation of renal hypertrophy as well as other related effects. Therefore, the human array can be used for gene expression analysis in pig kidney cells and we believe that our findings of differentially expressed genes served as genetic markers and biological functions can lead to a better understanding of ANP action on the renal protective system and may be used for further therapeutic application.     

Insights into kidney stem cell development and regeneration using zebrafish

Kidney disease is an escalating global health problem,for which the formulation of therapeutic approaches using stem cells has received increasing research attention.The complexity of kidney anatomy and function,which includes the diversity of renal cell types,poses formidable challenges in the identification of methods to generate replacement structures.Recent work using the zebrafish has revealed their high capacity to regenerate the integral working units of the kidney,known as nephrons,following acute injury.Here,we discuss these findings and explore the ways that zebrafish can be further utilized to gain a deeper molecular appreciation of renal stem cell biology,which may uncover important clues for regenerative medicine.     

Truncated structural variants of lipoarabinomannan in Mycobacterium leprae and an ethambutol-resistant strain of Mycobacterium tuberculosis

Current knowledge on the structure of lipoarabinomannan (LAM) has resulted primarily from detailed studies on a few selected laboratory strains of Mycobacterium tuberculosis, Mycobacterium bovis BCG, and Mycobacterium smegmatis. Our previous work was the first to report on the salient structural features of M. tuberculosis clinical isolates and demonstrated significant structural variations. A prime effort is to correlate a particular structural characteristic with observed differences in eliciting an immunobiological response, especially in the context of CD1-restricted presentation of LAM to T cells. T cell clones derived from the cutaneous lesions of leprosy patients have been shown to recognize specifically LAM from Mycobacterium leprae and not from M. tuberculosis Erdman or H37Rv. Herein we provide further fine structural data on LAM from M. leprae (LepLAM) and a tuberculosis clinical isolate, CSU20 (CSU20LAM), which was unexpectedly recognized by the supposedly LepLAM-specific CD1-restricted T cell clones. In comparison with the de facto laboratory LAM standard from M. tuberculosis H37Rv (RvLAM), LepLAM derived from in vivo grown M. leprae is apparently simpler in its arabinan architecture with a high degree of exposed, non-mannose-capped termini. On the other hand, CSU20, an ethambutol-resistant clinical isolate, makes a vastly heterogeneous population of LAM ranging from rather small and non-mannose-capped to full-length and fully capped variants. LepLAM and CSU20LAM contain a higher level of succinylation than RvLAM, which, in the context of truncated or less elaborated arabinan, may contribute to selective recognition by T cells. LAM from all species could be resolved into discrete forms by isoelectric focusing based apparently on their arabinan heterogeneity. In the light of our current and more recent findings, we reason that all immunobiological data should be cautiously interpreted and that the actual LAM variants that may be present in vivo during infection and pathogenesis need to be taken into consideration.     

The role of insulin-like growth factors and IGF-binding proteins in the physiological and pathological processes of the kidney.

Insulin-like growth factors (IGFs) and their binding proteins are implicated in the growth regulation of the kidney during embryogenesis and differentiation. Recent evidence also suggests that IGFs play a role in kidney physiology (glomerular filtration rate, renal plasma flow) and pathology (diabetic renal hypertrophy, nephritis, glomerulosclerosis, kidney tumours, chronic renal failure). This review focuses on the biology of IGFs at the molecular, protein and receptor levels and considers their importance in renal physiology and pathology. The current data demonstrate a central role for the IGFs in the mediation of a wide variety of effects on renal growth, function and malignancy.     

Heavy metal poisoning: the effects of cadmium on the kidney

The heavy metal cadmium (Cd) is known to be a widespread environmental contaminant and a potential toxin that may adversely affect human health. Exposure is largely via the respiratory or gastrointestinal tracts; important non-industrial sources of exposure are cigarette smoke and food (from contaminated soil and water). The kidney is the main organ affected by chronic Cd exposure and toxicity. Cd accumulates in the kidney as a result of its preferential uptake by receptor-mediated endocytosis of freely filtered and metallothionein bound Cd (Cd-MT) in the renal proximal tubule. Internalised Cd-MT is degraded in endosomes and lysosomes, releasing free Cd²⁺ into the cytosol, where it can generate reactive oxygen species (ROS) and activate cell death pathways. An early and sensitive manifestation of chronic Cd renal toxicity, which can be useful in individual and population screening, is impaired reabsorption of low molecular weight proteins (LMWP) (also a receptor-mediated process in the proximal tubule) such as retinol binding protein (RBP). This so-called ‘tubular proteinuria’ is a good index of proximal tubular damage, but it is not usually detected by routine clinical dipstick testing for proteinuria. Continued and heavy Cd exposure can progress to the clinical renal Fanconi syndrome, and ultimately to renal failure. Environmental Cd exposure may be a significant contributory factor to the development of chronic kidney disease, especially in the presence of other co-morbidities such as diabetes or hypertension; therefore, the sources and environmental impact of Cd, and efforts to limit Cd exposure, justify more attention.     

In search of adult renal stem cells

The therapeutic potential of adult stem cells in the treatment of chronic degenerative diseases has becoming increasingly evident over the last few years. Significant attention is currently being paid to the development of novel treatments for acute and chronic kidney diseases too. To date, promising sources of stem cells for renal therapies include adult bone marrow stem cells and the kidney precursors present in the early embryo. Both cells have clearly demonstrated their ability to differentiate into the kidney's specialized structures. Adult renal stem cells have yet to be identified, but the papilla is where the stem cell niche is probably located. Now we need to isolate and characterize the fraction of papillary cells that constitute the putative renal stem cells. Our growing understanding of the cellular and molecular mechanisms behind kidney regeneration and repair processes - together with a knowledge of the embryonic origin of renal cells - should induce us, however, to bear in mind that in the kidney, as in other mesenchymal tissues, the need for a real stem cell compartment might be less important than the phenotypic flexibility of tubular cells. Thus, by displaying their plasticity during kidney maintenance and repair, terminally differentiated cells may well function as multipotent stem cells despite being at a later stage of maturation than adult stem cells. One of the major tasks of Regenerative Medicine will be to disclose the molecular mechanisms underlying renal tubular plasticity and to exploit its biological and therapeutic potential.     

Sequential protooncogene expression in regenerating kidney following acute renal injury

Following loss of functional renal mass due to acute injury, there is significantly increased proliferation of tubular epithelium to replace injured and necrotic cells. In contrast, following uninephrectomy, the contralateral kidney increases in size primarily by hypertrophy, with little cellular proliferation. We and others have demonstrated only modest increases in renal protooncogene expression following uninephrectomy. In this study, we demonstrate markedly elevated expression of the protooncogenes c-fos, c-myc, c-Ki-ras, and c-Ha-ras following acute renal injury induced by a single large parenteral dose of folic acid. The expression of these genes occurs in a sequential pattern similar to that seen in proliferating cells in culture and in regenerating liver. In addition, we demonstrate elevated levels of histone H4 and beta-actin mRNAs consistent with increased cell proliferation. These data suggest that the molecular mechanisms regulating cell proliferation in the kidney are similar to those in regenerating liver and in cultured cells. In addition, it appears that these events are regulated normally after acute renal injury and following uninephrectomy, since in both instances the levels of protooncogene expression correlate with the degree of cell proliferation. This is in direct contrast to a pathologic renal condition, polycystic kidney disease, in which the level of protooncogene expression is out of proportion to the degree of cell proliferation. Further studies of the molecular correlates of acute renal injury may yield insight into the pathogenesis of this and other clinically important renal disorders.     

The molecular basis of renal tubular transport disorders

Sodium and water homeostasis are key to the survival of organisms. Reabsorption of sodium and water occurs throughout the tubule structure of the nephron, the basic functional unit of the kidney, by various transport mechanisms. Altered transport protein function can lead to renal tubular disorders resulting in metabolic alkalosis, hypokalemia, hypertension, and decreased capacity to concentrate urine, for instance. However, recent advances in molecular physiology, molecular genetics and expression cloning systems have aided in unraveling the molecular basis of some renal tubular disorders. This review will examine the molecular basis of Bartter's syndrome, Gitelman's syndrome, Liddle's syndrome, and autosomal nephrogenic diabetes insipidus. An understanding of the molecular basis of these disorders of the human kidney can give us a better understanding of basic renal function of lower mammals and other vertebrates.     

Renal progenitors: Roles in kidney disease and regeneration

Kidney disease is a devastating condition that affects millions of people worldwide, and its prevalence predicted to significantly increase. The kidney is complex organ encompassing many diverse cell type organized in a elaborate tissue architecture, makin regeneration a challenging feat. In recent years, there ha been a surge in the field of stem cell research to develo regenerative therapies for various organ systems. Here we review some recent progressions in characterizing th role of renal progenitors in development, regeneration and kidney disease in mammals. We also discuss how the zebrafish provides a unique experimental anima model that can provide a greater molecular and genet understanding of renal progenitors, which may contribut to the development of potential regenerative therapies fo human renal afflictions.