Binding of the blood group-reactive lectins to human adult kidney specimens

A Useful Guide to Lectin Binding: Machine-Learning Directed Annotation of 57 Unique Lectin Specificities

Glycans are critical to every facet of biology and medicine, from viral infections to embryogenesis. Tools to study glycans are rapidly evolving; however, the majority of our knowledge is deeply dependent on binding by glycan binding proteins (e.g., lectins). The specificities of lectins, which are often naturally isolated proteins, have not been well-defined, making it difficult to leverage their full potential for glycan analysis. Herein, we use a combination of machine learning algorithms and expert annotation to define lectin specificity for this important probe set. Our analysis uses comprehensive glycan microarray analysis of commercially available lectins we obtained using version 5.0 of the Consortium for Functional Glycomics glycan microarray (CFGv5). This data set was made public in 2011. We report the creation of this data set and its use in large-scale evaluation of lectin-glycan binding behaviors. Our motif analysis was performed by integrating 68 manually defined glycan features with systematic probing of computational rules for significant binding motifs using mono- and disaccharides and linkages. Combining machine learning with manual annotation, we create a detailed interpretation of glycan-binding specificity for 57 unique lectins, categorized by their major binding motifs: mannose, complex-type N-glycan, O-glycan, fucose, sialic acid and sulfate, GlcNAc and chitin, Gal and LacNAc, and GalNAc. Our work provides fresh insights into the complex binding features of commercially available lectins in current use, providing a critical guide to these important reagents.

Reabsorption in the proximal tubuli-ultrastructural evidence for a novel aspect of renal VEGF trafficking

Many clinical and experimental studies have revealed VEGF as an important factor in the pathophysiology of renal damage during diabetes mellitus (DM). Anti-VEGF therapy is in clinical use for treatment of DM and other diabetes-related (and unrelated) diseases. Nevertheless, little is known about the metabolism of VEGF in the kidneys. In order to determine the ultrastructural localization of VEGF in the kidney, we study the distribution of VEGF in the kidney of rats by using immunogold immunohistochemistry. Our light-microscopic data showed remarkable re-distribution of VEGF in proximal tubular cells (PTCs) during prolonged hyperglycemia, a DM type 2 model (DM2), which was confirmed by transmission electron microscopy (TEM) findings. TEM findings revealed an initial presence of VEGF in the vesicular transport apparatus of PTCs in healthy rats and its gradual translocation to the apical membrane of PTCs after renal damage caused by high sucrose treatment. The presented data add to our understanding of kidney VEGF trafficking, providing novel insight into the renal metabolism and pharmacodynamics of the cytokine. This could have a high impact on the use of VEGF and anti-VEGF therapy in different renal diseases.

IgA nephropathy and IgA vasculitis with nephritis have a shared feature involving galactose-deficient IgA1-oriented pathogenesis

Galactose-deficient IgA1 has been proposed as an important effector molecule in IgA nephropathy (IgAN). We previously showed that the galactose-deficient IgA1-specific monoclonal antibody KM55 can detect circulating galactose-deficient IgA1 in patients with IgAN, enabling us to study the molecular roles of galactose-deficient IgA1. Herein, we further examined the pathophysiological significance of galactose-deficient IgA1 in glomerular deposits of patients with IgAN by immunohistochemistry using KM55. Immunostaining of galactose-deficient IgA1 with KM55 was performed in paraffin-embedded sections of renal biopsy specimens from 48 patients with IgAN and 49 patients with other renal diseases such as lupus nephritis, HCV-related nephropathy, IgA vasculitis with nephritis (IgA-VN), and membranous nephropathy. Glomerular galactose-deficient IgA1 was specifically detected in IgAN and IgA-VN but not in the other renal diseases. Galactose-deficient IgA1 was localized predominantly in the mesangial region as IgA deposition. However, galactose-deficient IgA1 was not detected in patients with lupus nephritis accompanied by glomerular IgA deposition. Thus, our study strongly suggests that IgAN and IgA-VN have a shared feature regarding galactose-deficient IgA1-oriented pathogenesis.

Novel lectin-independent approach to detect galactose-deficient IgA1 in IgA nephropathy

Background

Galactose-deficient IgA1 (Gd-IgA1) is a critical effector molecule in the pathogenesis of IgA nephropathy (IgAN). Although many researchers have measured serum levels of Gd-IgA1 using snail helix aspersa agglutinin (HAA) lectin-based assay, the lectin-dependent assay has some serious problems in robustness. In this study, we aimed to establish a more robust and stable enzyme-linked immunosorbent assay (ELISA) method that uses a specific monoclonal antibody to recognize a hinge region in human Gd-IgA1 (Gd-IgA1 ELISA).

Methods

Rats were immunized with human Gd-IgA1 hinge region peptide to obtain Gd-IgA1-specific monoclonal antibody KM55. Gd-IgA1 ELISA for specifically detecting serum Gd-IgA1 was consequently constructed. Serum Gd-IgA1 concentrations in human subjects were measured using KM55 ELISA assay. To further confirm specificity of the Gd-IgA1-specific antibody, KM55 was also applied for immunofluorescence staining of glomerular Gd-IgA1 in paraffin-embedded sections of renal biopsy specimens.

Results

Measurement of serum levels of Gd-IgA1 in human subjects by Gd-IgA1 ELISA revealed increased serum Gd-IgA1 level in patients with IgAN compared with patients with other renal diseases or non-renal diseases. Importantly, the results obtained from Gd-IgA1 ELISA positively correlated with those from the HAA lectin-based assay (R = 0.75). Immunofluorescence staining of renal biopsy specimens with KM55 detected glomerular co-localization of Gd-IgA1 and IgA.

Conclusion

This novel lectin-independent method with KM55 for measuring serum levels of Gd-IgA1 can pave the way for more convincing diagnosis and activity assessment of IgAN, and can expedite clinical research to better understand this difficult disease.

Application of Dolichos biflorus in immunoassay detection of kidney collecting duct biomarkers

Currently there are no biomarkers for detecting collecting duct damage in man. Antibodies to several collecting duct-specific antigens exist but sandwich assays have been difficult to establish due to the need for two different antibodies to the same protein. We hypothesized that a collecting duct-specific lectin could be used in combination with a collecting duct-specific antibody to negate the need for two different antibodies. The collecting duct specificity of selected antibodies (NiCa II 13C2, Pap XI 3C7, HuPaP VII 2B11 and aquaporin 2), was verified by immunohistochemistry. Aquaporin 2 and Pap XI 3C7 were used successfully in setting up assays with the lectin Dolichos biflorus, using the Meso Scale Discovery (MSD) platform. Antigen expression was highest in the papillae of rat and human kidney (corresponding to the greatest density of collecting ducts) and was also present in normal urine. We propose that further qualification and validation would lead to an assay for detecting collecting duct damage in man.

Does the Analysis Based on a Histological and Immunohistochemical Grading System in the Model of BDL Kidney Allow the Quantification of the Degree of Injury?

The aim of this study is to evaluate histopathological findings induced by Nomega-nitro-L-arginine methyl ester (L-NAME) and molsidomine (MOL) on the kidney of bile duct ligated rats. Forty Sprague-Dawley rats, each weighing 125 to 140 g, were included in the study. Extent of histological glomerular injury scores (GIS), arterial injury scores (AIS), and tubulointerstitial injury scores (TIS) in each animal were graded. Alpha-smooth muscle actin (alpha-SMA), tenascin, lectin (Ulex europaeus agglutinin-1), and vimentin were used to determine extent of the injury. The cholestasis was evidenced by a significant increase in the levels of serum total bilirubin in BDL rats (p < 0.01). Malondialdeyde MDA levels increased by the bile duct ligation (BDL) to 12.10 +/- 0.45. This value was significantly higher than the other groups (p < 0.01). Changes in the BDL kidney were marked at 7 days after surgery. GIS were observed to have the highest score, especially at juxtamedullary region in BDL/L-NAME rats, and AIS were also the highest score in this region. These observations were lower in BDL/MOL rats. There is a correlation between GIS and AIS scores (r = .2, p < .01). TIS revealed that BDL/L-NAME rats were significantly more damage than rats in the other groups (p<.001). MOL-treated rats showed considerably fewer lesions in the tubules and interstitium (p < .001). The tubular injuries observed in BDL and BDL/L-NAME rats were significantly attenuated by MOL treatment. Lectin was more and extensively stained in tubular epithelia of the BDL/L-NAME group than in the other (p <.05). Expression of tenascin in tubular epithelia was significantly higher in BDL and BDL/L-NAME as compared with controls (p < .01). Fibrous tissue was only observed in the BDL and BDL/L-NAME group. These areas were weakly stained with vimentin. alpha-SMA staining was more reduced in the L-NAME-treated arterioles than in BDL/MOL (p < .05). In conclusion, the analysis of cell injury based on a histological grading system in the model of BDL kidney allows the quantification of the degree of injury.

Cell surface markers in human embryonic stem cells

The pluripotent nature of human embryonic stem cells (hESCs) is based on their potential to form every cell type in the body. Prior to use in directed differentiation strategies, these cells need to be thoroughly characterized. The large number of glycoproteins and carbohydrates that exist on the cell surface provide an excellent opportunity for characterizing hESCs and a means to delineate pluripotent and differentiated cell types. A panel of 14 lectins, based on their specificity for a variety of carbohydrates and carbohydrate linkages, along with stage-specific embryonic antigen-4 (SSEA-4), have been chosen to examine hESCs for other potential pluripotent markers. These studies have been achieved by binding quantitation by flow cytometry and binding localization in adherent colonies by immunocytochemistry. We have shown that certain lectins may be used as markers that are associated with the pluripotent state of hESCs because binding percentages and binding localization of these lectins are similar to those of SSEA-4. This presents options for systematic classification of pluripotent hESCs and for distinguishing differentiated hESC types based on glycan presentation that accompanies differentiation.

Lectin binding profiles of SSEA-4 enriched, pluripotent human embryonic stem cell surfaces

Background

Pluripotent human embryonic stem cells (hESCs) have the potential to form every cell type in the body. These cells must be appropriately characterized prior to differentiation studies or when defining characteristics of the pluripotent state. Some developmentally regulated cell surface antigens identified by monoclonal antibodies in a variety of species and stem cell types have proven to be side chains of membrane glycolipids and glycoproteins. Therefore, to examine hESC surfaces for other potential pluripotent markers, we used a panel of 14 lectins, which were chosen based on their specificity for a variety of carbohydrates and carbohydrate linkages, along with stage specific embryonic antigen-4 (SSEA-4), to determine binding quantitation by flow cytometry and binding localization in adherent colonies by immunocytochemistry.

Results

Enriching cells for SSEA-4 expression increased the percentage of SSEA-4 positive cells to 98–99%. Using enriched high SSEA-4-expressing hESCs, we then analyzed the binding percentages of selected lectins and found a large variation in binding percentages ranging from 4% to 99% binding. Lycopersicon (tomato)esculetum lectin (TL), Ricinus communis agglutinin (RCA), and Concanavalin A (Con A) bound to SSEA-4 positive regions of hESCs and with similar binding percentages as SSEA-4. In contrast, we found Dolichos biflorus agglutinin (DBA) and Lotus tetragonolobus lectin (LTL) did not bind to hESCs while Phaseolus vulgaris leuco-agglutinin (PHA-L), Vicia villosa agglutinin (VVA), Ulex europaeus agglutinin (UEA), Phaseolus vulgaris erythro-agglutinin (PHA-E), and Maackia amurensis agglutinin (MAA) bound partially to hESCs. These binding percentages correlated well with immunocytochemistry results.

Conclusion

Our results provide information about types of carbohydrates and carbohydrate linkages found on pluripotent hESC surfaces. We propose that TL, RCA and Con A may be used as markers that are associated with the pluripotent state of hESCs because binding percentages and binding localization of these lectins are similar to those of SSEA-4. Non-binding lectins, DBA and LTL, may identify differentiated cell types; however, we did not find these lectins to bind to pluripotent SSEA-4 positive hESCs. This work represents a fundamental base to systematically classify pluripotent hESCs, and in future studies these lectins may be used to distinguish differentiated hESC types based on glycan presentation that accompanies differentiation.

GalNAc glycoprotein expression by breast cell lines, primary breast cancer and normal breast epithelial membrane

Over-expression of N-acetylgalactosamine glycoproteins as detected by binding of the lectin from Helix pomatia (HPA), is associated with metastatic competence and poor patient prognosis in a range of human adenocarcinomas. These glycoproteins remain poorly characterised, and their functional role has yet to be elucidated. This study describes characterisation of a range of human breast/breast cancer cell lines for the expression of the N-acetylgalactosaminylated glycoproteins of interest, and their comparison with normal breast epithelium and a range of clinical breast carcinoma samples. Confocal and light microscopy studies revealed cytochemical HPA-binding patterns consistent with a fundamental disruption in normal glycobiosynthetic pathways attending increasing metastatic potential. We report the most complete comparative analysis of HPA-binding ligands from cultured breast cells, clinical breast carcinoma samples and normal breast epithelium to date. Lectin blotting identified 11 major HPA-binding glycoprotein bands common to both clinical tumour samples and breast cell lines and 6 of these bands were also expressed by samples of normal breast epithelium, albeit at much lower levels. Moreover, very marked quantitative but not qualitative differences in levels of expression consistent with metastatic capability were noted.

Identification of nucleated cells in urine using lectin staining

Microscopic examination of urinary sediment is an integral component in the evaluation of nephropathies. However, identification and differentiation of the nucleated nonsquamous cells in urine is often difficult using such conventional techniques as phase contrast or bright field microscopy, even after Papanicolaou staining, and requires a lot of experience. We now report a method to differentiate urinary cell types using lectin staining. Twenty-five lectins were examined with respect to their binding pattern on cryosections of the human kidney and urinary tract, as well as binding to blood cells. The specificity of lectin binding to a cell type both in situ and in urine was confirmed by double labeling with specific antibodies directed against various sections of the nephron or nucleated blood cells. For urine cytologic examinations, acetone-fixed cytopreparations of urinary sediments were incubated with a combination of a fluorescein isothiocyanate (FITC)-coupled and a rhodamine-coupled lectin, followed by staining of the nuclei with 4',6-diamidino-2-phenylindole. Specimens were examined in triple immunofluorescence (FITC/rhodamine/UV). Cell types could be identified by their characteristic lectin-binding pattern. For example, the lectin combination of Sophora japonica agglutinin (aggl; SJA) and Erythrina cristagalli aggl (ECA) permitted a differentiation between cells of the proximal tubules (SJA positive [SJA+], ECA+), distal tubules (SJA negative [SJA-], ECA+), collecting ducts (SJA+, ECA-), and lymphocytes (SJA-, ECA-). In preliminary studies, examination of urinary sediment in various chronic nephropathies by this technique showed differences in their cellular excretion pattern. In summary, staining urinary sediments with combinations of lectins provides a rapid and relatively inexpensive method for a facilitated and reliable differentiation of the various nucleated cell types in urine.

Heterogeneous histochemical reaction pattern of the lectin Bandeiraea (Griffonia) simplicifolia with blood vessels of human full-term placenta

Bandeiraea simplicifolia lectin (BS-I) stains vascular endothelium in various species. In humans, less than 10% of the specimens studied exhibit a reaction with BS-I. In the present histochemical study, the reactivity of BS-I with placental blood vessels and its correlation with the blood group from mother and newborn child was investigated. Acetone-fixed cryosections of representative tissue segments of human full-term placenta and umbilical cord were stained with BS-I. The staining pattern of tissues from patients with different blood groups was identical, although the reaction of BS-I in the placenta was heterogeneous. BS-I did not react with the umbilical cord. Vascular smooth muscle cells at the insertion site of the umbilical cord into the chorionic plate, and endothelium deeper in the chorionic plate, became progressively stained. The endothelial cells and tunica muscularis of smaller arteries and veins in stem villi lost their reactivity in parallel with decreasing vessel size. Arterioles and venules reacted heterogeneously. Capillaries, trophoblastic basement membranes, especially epithelial plates, and sometimes the syncytiotrophoblast were labelled in several terminal villi. The data indicate that 1) the placenta binds BS-I to fetal endothelium independent of the blood group, 2) cell-surface antigens on placental endothelial cells are expressed heterogeneously and 3) cell-surface glycans are constituted in an organ-specific manner on human endothelial cells.

Histochemistry with Helix pomatia agglutinin in human germ cell tumors: detection of nongerminomatous components and correlation between HPA reactivity and radiosensitivity in germinomas

Binding sites of Helix pomatia agglutinin (HPA) were examined in 32 patients with intracranial human germ cell tumors. HPA reactivity was found in vascular endothelial cells and erythrocytes of patients with blood type A or AB. HPA-positive neoplastic cells were seen in one yolk sac carcinoma in a patient with blood group A, and in embryonal carcinomas and teratomas irrespective of blood group type. Although in 10 out of 18 germinomas neoplastic cells were totally negative for HPA, another 8 germinomas showed HPA-positive neoplastic cells which were distributed sporadically or in an area and independent of blood group types. HPA-negative germinoma patients showed a very good response to radiotherapy, whereas 4 out of 8 HPA-positive tumors showed poor radiosensitivity, with a residual lesion seen on computed tomography even after the total radiation dose of 40-50 Gy. These findings suggest that HPA-positive neoplastic cells in germinomas indicate components of differentiation of non-germinomatous germ cells. HPA-positive germinomas might be less radiosensitive than HPA-negative germinomas.

Study of renal tubular glycoconjugates in tubulointerstitial damage using conjugated lectins

Changes in the glycoconjugates of renal tubules associated with tubular damage were studied by lectin histochemistry, and their possible significance was determined. The excretion of various saccharides in tubular casts may also serve as markers of renal tubular damage. Renal tissues from 55 cases with various glomerular diseases including ten controls were studied. The patients were divided into two groups: one with tubulointerstitial lesions (TILs) (30 cases), and the other without (15 cases). Our results showed a wide spectrum of changes, predominantly in the disease group with TILs. The brush border of the proximal tubules showed significantly increased staining with Triticum vulgaris (WGA) and decreased staining with Canavalia ensiformis (Con A) lectins in both disease groups. The distal tubules revealed a significant increase in the apical and a decrease in the basal staining with Arachis hypogaea (PNA) and WGA lectins, respectively, in cases with TILs. The significant decrease in the basal domain staining was also seen with WGA lectin in cortical ducts. The vulnerability of various segments of the tubules in the process of TILs was clearly demonstrable. It appeared that the distal tubules were the most vulnerable anatomical segments around which the TILs began and later spread to involve other segments of tubules.

Lectin-binding carbohydrates in sexual differentiation of rat male and female gonads

Development and sexual differentiation of the mammalian gonad involve changes in the type and distribution of different proteins and glycoproteins in and around the epithelial gonadal cords, the future seminiferous tubules in the testis, and follicles in the ovary. To study changes in cellular carbohydrate-containing compounds in the sex-specific morphogenesis of rat gonads, sections from embryonic, fetal and early postnatal gonads were labelled with seven different fluorescein isothiocyanate (FITC)-conjugated plant lectins of various carbohydrate-binding specificities. Double labelling of laminin with tetramethylrhodamine isothiocyanate (TRITC)-conjugated antibodies was used to outline the epithelial tissues. From the results we conclude that the abundance and similar distribution of carbohydrates in the early gonads of both sexes supports their sexually indifferent nature. Furthermore, the basement membranes of the differentiating gonadal cords in both sexes have common features, which differ, however, from those of the other developing urogenital organs. Changes in carbohydrate composition appear with the sexual differentiation of the gonads; the similarity of the changes in lectin binding to the gonadal cords of embryonic and fetal male, and to postnatal female, suggests similar mechanisms of cell-cell interactions in both sexes although activated at different developmental stages. These carbohydrate specificities at the tissue level should be taken into account together with cell-type specific changes, e.g. in the formation of the zona pellucida, when the phenomenon of polymorphic expression of different compounds is integrated into theories of epithelial differentiation.

Sexual dimorphism of the kidney in the NMRI mouse as shown by Dolichos biflorus agglutinin labelling

The histological affinity pattern of Dolichos biflorus agglutinin (DBA) in kidneys from mice (NMRI, Balb/c, CBA) and rats (Wistar) fixed by perfusion with formalin, Bouin, or HgCl2 was investigated with a horseradish peroxidase conjugate. The animals were examined from fetal stage to adulthood. Adult female NMRI mice exhibited constant DBA labelling, with DBA binding to cells of the proximal and collecting tubules. Moreover the vascular endothelium of the renal papilla was found to be DBA-positive in 50% of adult female animals. In contrast, there was only very little DBA binding in the kidneys of male adult NMRI mice. There was no sexual dimorphism in lectin labelling in kidneys from other strains of mice or from rats.

Histochemical and cytochemical localization of blood group antigens

The oligosaccharide structures of blood group antigens are not the primary gene products; they are constructed in a stepwise manner by adding particular sugar to precursor oligosaccharides via several glycosyltransferases coded for by different blood group genes (Watkins 1966, 1978, 1980). Consequently, final profiles of antigens expressed in each cell type are influenced by many different factors such as the intrinsic composition of glycosyltransferase species which are defined by the genotype of the individuals, relative activity or amount of these enzymes (repression, derepression or induction of the enzymes), competition between enzymes with overlapping substrate specificity, the organization of the enzymes in membranes, utilizability of precursors and specific substrate sugars, and the activity level of degradating enzymes. Changes in the antigen profiles during maturation, differentiation and malignant transformation are thought to be intimately related to the variability of these factors. Although great importance attaches to histo- and cytochemical information on the distribution and levels of glycosyltransferases and messenger RNA corresponding to the relevant enzyme, detailed and precise localization of the blood group antigens and their variants is the base line for analyzing these complex factors. On the basis of individual genotype and histochemical findings about the antigen distribution and the interrelationship between cells and cellular components producing different antigenic structures (cellular and subcellular mosaicism), we can deduce precursor oligosaccharide levels as well as the status of gene activation and its primary product, glycosyltransferases. Thus, these findings are a prerequisite for further analysis at the molecular genetic level. As emphasized in this article, lectin staining or immunostaining methods with MAbs combined with glycosidase digestion procedures are powerful tools for in situ analysis of carbohydrate structures in histochemical systems. Although in some cases valuable results have been obtained by applying the technique, our knowledge concerning the distribution of complex carbohydrate structures is still far from satisfactory. Along with well defined MAbs and lectins, the key to developing our methods further is successful introduction of glycosidases, in particular, endoglycosidases since these reagents are indispensable for analyzing the inner core structures and glycoconjugate species of the blood group antigens. Application of these techniques at the ultrastructural level is an alluring possibility, even though many difficulties must be overcome. Although their functional roles have not yet been determined, a diverse array of macromolecules is known to be decorated with blood group-related antigens.(ABSTRACT TRUNCATED AT 400 WORDS)

Morphological and cytogenetic studies of angiosarcoma in Stewart-Treves syndrome

A morphological and cytogenetic analysis of a multifocal angiosarcoma in a typical case of Stewart-Treves syndrome is reported. The morphological analysis indicated differentiation along both blood and lymph vessel endothelium lines. By light and electron microscopy there were areas with well-developed erythrocyte-containing, capillary-like vessels and poorly differentiated areas with abortive vascular formations. In these the endothelium revealed immunoreactivity to factor VIII RAg, binding of Ulex europaeus I and Psophocarpus tetragonolobus agglutinin lectins, Weibel-Palade bodies ultrastructurally and presented a continuous enclosing external lamina and immunoreactivity for laminin and collagen IV, all features of blood-vessel differentiation. There were also lymphangioma-like areas as well as poorly differentiated areas where the immunohistochemical, lectin-binding and ultrastructural features were compatible with a lymph vessel differentiation. Cytogenetic analysis of cultured tumour cells revealed chromosome counts in the diploid region. About 40% of the cells analysed had a normal diploid karyotype. The remaining cells showed a multitude of mainly nonclonal structural alterations; 17 unique marker types resulting from different translocations and deletions were observed. There were also a few cells with clonal numerical deviations showing monosomy 22, monosomy X and trisomy 2 respectively. It is of interest that the losses of chromosome 22 and the X chromosome also have been observed in Kaposi's sarcoma and that the PD-ECGF gene, a novel angiogenetic factor, has been mapped to chromosome 22.