Cellular localization of lectin-affinity in tissue sections of normal human duodenum

Fibroblast growth factor 10 represses premature cell differentiation during establishment of the intestinal progenitor niche

Spatio-temporal regulation of the balance between cell renewal and cell differentiation is of vital importance for embryonic development and adult homeostasis. Fibroblast growth factor signaling relayed from the mesenchyme to the epithelium is necessary for progenitor maintenance during organogenesis of most endoderm-derived organs, but it is still ambiguous whether the signal is exclusively mitogenic. Furthermore, the downstream mechanisms are largely unknown. In order to elucidate these questions we performed a complementary analysis of fibroblast growth factor 10 (Fgf10), gain-of-function and loss-of-function in the embryonic mouse duodenum, where the progenitor niche is clearly defined and differentiation proceeds in a spatially organized manner. In agreement with a role in progenitor maintenance, FGF10 is expressed in the duodenal mesenchyme during early development while the cognate receptor FGFR2b is expressed in the epithelial progenitor niche. Fgf10 gain-of-function in the epithelium leads to spatial expansion of the progenitor niche and repression of cell differentiation, while loss-of-function results in premature cell differentiation and subsequent epithelial hypoplasia. We conclude that FGF10 mediated mesenchymal-to-epithelial signaling maintains the progenitor niche in the embryonic duodenum primarily by repressing cell differentiation, rather than through mitogenic signaling. Furthermore, we demonstrate that FGF10-signaling targets include ETS-family transcription factors, which have previously been shown to regulate epithelial maturation and tumor progression.

FGF10 maintains distal lung bud epithelium and excessive signaling leads to progenitor state arrest, distalization, and goblet cell metaplasia

BACKGROUND

Interaction with the surrounding mesenchyme is necessary for development of endodermal organs, and Fibroblast growth factors have recently emerged as mesenchymal-expressed morphogens that direct endodermal morphogenesis. The fibroblast growth factor 10 (Fgf10) null mouse is characterized by the absence of lung bud development. Previous studies have shown that this requirement for Fgf10 is due in part to its role as a chemotactic factor during branching morphogenesis. In other endodermal organs Fgf10 also plays a role in regulating differentiation.

RESULTS

Through gain-of-function analysis, we here find that FGF10 inhibits differentiation of the lung epithelium and promotes distalization of the embryonic lung. Ectopic expression of FGF10 in the lung epithelium caused impaired lung development and perinatal lethality in a transgenic mouse model. Lung lobes were enlarged due to increased interlobular distance and hyperplasia of the airway epithelium. Differentiation of bronchial and alveolar cell lineages was inhibited. The transgenic epithelium consisted predominantly of proliferating progenitor-like cells expressing Pro-surfactant protein C, TTF1, PEA3 and Clusterin similarly to immature distal tip cells. Strikingly, goblet cells developed within this arrested epithelium leading to goblet cell hyperplasia.

CONCLUSION

We conclude that FGF10 inhibits terminal differentiation in the embryonic lung and maintains the distal epithelium, and that excessive levels of FGF10 leads to metaplastic differentiation of goblet cells similar to that seen in chronic inflammatory diseases.

Lectin-binding properties of the antral and body surface mucosa in the human stomach--are the differences relevant for Helicobacter pylori affinity?

Biopsy specimens from histologically normal human gastric mucosa were examined histochemically with the use of lectins. Significant differences were found in the glycoconjugate patterns of the surface mucous cells between the body and the corresponding antrum. Two lectins (Ulex europaeus agglutinin I and Ricinus communis agglutinin I) specific for fucose and galactose residues stained the apical membrane and the intracellular (perinuclear) region of the antral mucosa more strongly than those of the body (P < 0.04). Body and antral biopsies from patients with Helicobacter pylori-positive chronic active gastritis were also studied, but the lectin patterns of Helicobacter pylori-infected body and antrum did not differ. On comparing these chronically infected gastric biopsies with normal antral mucosa, however, significant changes could be seen with the fucose-binding lectin as well as with two other lectins (succinylated concanavalin A and peanut agglutinin). These differences could have been induced directly by bacterial virulence factors or could be due to non-specific reactions to the inflammatory process.

The interaction between plant lectins and the small intestinal epithelium: a primary cause of intestinal disturbance

The literature concerning the effects of plant lectins on the small intestinal epithelium is reviewed. It appears that after oral intake, intact plant lectins can reach the small intestinal lumen. Their binding to the mucosal surface evokes an increased synthesis of glycoproteins and a degeneration of the intestinal epithelium. The epithelial alterations may result in hyperregenerative villus atrophy and endogenous nitrogen loss. These changes ultimately can lead to less efficient feed conversion, diminished growth, scouring, wasting and death. The possible significance of plant lectins in digestive disturbances in farm animals is suggested.

Quantitative determination of the lectin binding capacity of small intestinal brush-border membrane. An enzyme linked lectin sorbent assay (ELLSA)

A test to determine quantitatively the lectin binding sites in brush-border membranes has been developed. Highly purified bovine small intestinal brush-border membranes were prepared, and subsequently coated directly to the bottom of a microtiter plate. Soybean agglutinin conjugated with peroxidase was coupled to its binding sites in the brush-border membranes and the peroxidase activity was determined in a spectrophotometer. The number of soybean agglutinin binding sites in the brush-border membranes has been established by means of iterized computer fit analysis of the data, indicating values for maximal binding of 7.10(-7) M soybean agglutinin per mg of brush-border membrane protein and a dissociation constant of 1.5.10(-5) M.

Evaluation of structural and secretory glycoconjugates in normal human jejunum by means of lectin histochemistry

The labelling pattern of eight lectins was studied in jejunal samples from ten normal subjects, in order to define the normal distribution of structural and secretory glycoconjugates in the small bowel. The following lectins were studied by means of a peroxidase technique on formalin-fixed samples: Arachis hypogaea, Ricinus communis, Canavalia ensiformis, Lens culinaris, Phaseolus vulgaris, Triticum vulgaris, Ulex europaeus, Dolichos biflorus. Phaseolus vulgaris reacted with goblet cell mucus throughout the villus-crypt axis. Conversely Ulex europaeus, Dolichos biflorus and Triticum vulgaris lectin labelling of goblet cells appeared to be confined to the upper part of the villi. This finding suggests that during cell migration from crypt to villus tip, the continuing maturation of goblet cells is associated with the differentiation of secretory carbohydrates, which probably parallels the cell maturation cycle. Lectin histochemistry appears to be a reliable tool for the study of structural and secretory glycoconjugates in the jejunal mucosa, and might be of value in the study of diseases in which the cell-maturation cycle in the small bowel is altered.

Cervical intraepithelial glandular neoplasia (adenocarcinoma in situ and glandular dysplasia). A correlative study of 23 cases with histologic grading, histochemical analysis of mucins, and immunohistochemical determination of the affinity for four lectins

Twenty-three cases of cervical intraepithelial glandular neoplasia (CIGN)--a term encompassing adenocarcinoma in situ and glandular dysplasia of the uterine cervix--were studied histologically, histochemically for mucins (neutral mucins, sialomucins and sulfomucins), and immunohistochemically for the affinity of four lectins (WGA, PNA, RCA, UEA). For comparison, six cases of cervical invasive adenocarcinoma and ten cases of cervices without tumor were similarly studied. Criteria for histologic grading of CIGN into three degrees were proposed according to the hyperchromasia and the stratification of nuclei, number of mitoses, and amount of intracellular mucin. Two different types of CIGN were distinguished according to their histological aspect and their mucin pattern: CIGN type A, where the mucin pattern was qualitatively similar to that of normal endocervical mucosa, i.e., neutral mucins, sulfomucins and sialomucins; and CIGN type B, where the glandular cells resembled small intestinal goblet cells and the mucins consisted of neutral mucins and sialomucins with the absence of sulfomucins. Nine cases of CIGN were of type A, 2 of type B, and 12 of both type A and B. Differences in lectin binding existed between normal columnar cells, CIGN, and invasive adenocarcinomas, as well as between CIGN of type A and B. The intensity of the positive immunochemical reaction varied, as well as the type of binded lectin and its localization in the cell. There was a great heterogeneity in the same histologic group from one case to another, and even in the same case from one cell to another.

Comparative study of procedures for histological detection of lectin binding by use of Griffonia simplicifolia agglutinin I and gastrointestinal mucosa of the rat

The histological localisation of alpha-D-galactopyranosyl residues in glycoconjugates of rat stomach and duodenal mucosae was studied by use of Griffonia simplicifolia agglutinin I, i.e. the isolectin mixture (A + B) and the isolectin B4 (B4). Cryostat sections which were either unfixed or acetone fixed and paraffin sections from both ethanol-acetic acid and formaldehyde fixed tissue blocks were compared. Cellular details were better preserved in paraffin than in cryostat sections. Reactivity of cells binding GS I was less sensitive after formaldehyde than after ethanol-acetic acid fixation inasmuch as higher concentrations of lectins were needed. This drawback could be overcome by trypsinisation of the sections. The binding pattern of GS I (A + B) corresponded with that of GS I (B4) in either cryostat or paraffin sections. GS I was detected in the cytoplasm of parietal cells and in Brunner's gland cells. In duodenal crypts and villi, lectin was bound to supranuclear regions in the cytoplasm of columnar and goblet cells. The staining efficiency of fluorescein (FITC), horseradish peroxidase (HRP) and colloidal gold particle (CGP) labels in both direct and indirect lectin stainings was compared. Under all experimental conditions, indirect methods required lower concentrations of lectins than direct ones; indirect procedures increased sensitivity about 5-10 fold. CGP labels were always of highest sensitivity when gold particles were further developed by a silver precipitation method. HRP was not as efficient in lectin localisation as CGP, but cytochemical staining was more convenient in routine work. Direct FITC labellings proved to be of lowest sensitivity.