Light microscopic morphometric analysis of rat ileal mucosa: II. Component quantitation of Paneth cells

The enteric microbiota regulates jejunal Paneth cell number and function without impacting intestinal stem cells

Paneth cells (PCs) are epithelial cells found in the small intestine, next to intestinal stem cells (ISCs) at the base of the crypts. PCs secrete antimicrobial peptides (AMPs) that regulate the commensal gut microbiota. In contrast, little is known regarding how the enteric microbiota reciprocally influences PC function. In this study, we sought to characterize the impact of the enteric microbiota on PC biology in the mouse small intestine. This was done by first enumerating jejunal PCs in germ-free (GF) versus conventionally raised (CR) mice. We next evaluated the possible functional consequences of altered PC biology in these experimental groups by assessing epithelial proliferation, ISC numbers, and the production of AMPs. We found that PC numbers were significantly increased in CR versus GF mice; however, there were no differences in ISC numbers or cycling activity between groups. Of the AMPs assessed, only Reg3γ transcript expression was significantly increased in CR mice. Intriguingly, this increase was abrogated in cultured CR versus GF enteroids, and could not be re-induced with various bacterial ligands. Our findings demonstrate the enteric microbiota regulates PC function by increasing PC numbers and inducing Reg3γ expression, though the latter effect may not involve direct interactions between bacteria and the intestinal epithelium. In contrast, the enteric microbiota does not appear to regulate jejunal ISC census and proliferation. These are critical findings for investigators using GF mice and the enteroid system to study PC and ISC biology.

Characterization of paneth cells in alpacas (Vicugna pacos, Mammalia, Camelidae)

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We determinated Paneth Cells in fetus, offspring and adults alpacas.

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Studies of Paneth cells were done by cytochemistry, immunohistochemistry and lectinhistochemistry techniques.

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We describe Paneth Cell morphometry in fetal, young and adult alpacas.

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We founded Paneth cells in all the small intestinal sections from mid-gestation.

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PC location was similar to that described in other mammals, however they were more columnar than the conventional pyramidal shape.

Paneth cells are secretory epithelial cells of the innate immune system of the intestine of several mammals, including alpacas. Little is known about the latter; thus, in the present study we described the morphology and histochemical characteristics of Paneth cells in healthy fetuses, and young and adult alpacas. For this purpose, samples of duodenum, jejunum and ileum were taken from 6 fetuses at different days of pregnancy (between days 221–330), 66 offsprings (between 0 and 45-days-old) and 5 adult alpacas (>2-years-old). Samples were fixed in 10% buffered formalin and processed for histological and morphometrical analysis using HE and Masson Trichomićs technique. Immunohistochemistry was used to identify Paneth cells using anti-lysozyme antibody. In addition, the lectinhistochemichal binding-pattern of Paneth celĺs granules was evaluated. Lyzozyme was immunohistochemically detected in the granules of Paneth cells from day 283 of pregnancy in all the small intestinal sections of the studied fetuses. In newborn alpacas Paneth cells were initially found in the duodenum, but the following days (days 18–21 after birth) they were also found in the ileum. Their size gradually increased after birth, but then no significant differences were found. In adult alpacas the number was lower than offsprings. We suggest that Paneth cells early differentiate in the small intestine of alpacas, and the increase in their number during the first two weeks of life strongly support their possible involvement in the intestinal defensive functions against the enteric diseases that occur during the lactancy stage.

Expression of polymeric immunoglobulin receptor mRNA and protein in human paneth cells: Paneth cells participate in acquired immunity

OBJECTIVE

Paneth cells are important effectors of intestinal innate immunity. It has been generally accepted that Paneth cells do not participate in the synthesis of polymeric immunoglobulin receptor (pIgR) or the secretion of immunoglobulin A (IgA) in the small intestine. However, we have previously shown that pIgR is specifically localized in Paneth cells of the rat small intestine. We therefore investigated the possibility that pIgR is also localized in human Paneth cells.

METHODS

Double-labeled fluorescent immunohistochemistry and double-labeled fluorescent in situ hybridization were used to determine RNA and protein expression in normal human small intestine.

RESULTS

Both pIgR mRNA and protein were colocalized with lysozyme in normal human Paneth cells. Furthermore, IgA was colocalized with lysozyme in the secretory granules of human Paneth cells.

CONCLUSIONS

This is the first study to demonstrate that pIgR and IgA are colocalized in the secretory granules of human Paneth cells. These findings suggest that, in addition to their well-recognized role in innate immunity, Paneth cells are involved in IgA-mediated acquired immunity in the gastrointestinal tract. Furthermore, these results add to accumulating evidence that Paneth cells participate in intestinal inflammation.

Bethanechol and a G-protein activator, NaF/AlCl3, induce secretory response in Paneth cells of mouse intestine

Paneth cells located at the bottom of intestinal crypts may play a role in controlling the bacterial milieu of the intestine. Using morphometry to clarify the secretory mechanism of the Paneth cells, we studied the ultrastructural changes in mouse Paneth cells produced following intra-arterial perfusion with Hanks' balanced salt solution containing a cholinergic muscarinic secretagogue (bethanechol), a neuroblocking agent (tetrodotoxin), or a G-protein activator (NAF/AlCl3). Bethanechol (2 x 10(-4) mol/l) induced Paneth-cell secretion. Many Paneth cells massively exocytosed their secretory material into the crypt lumen; the enhanced secretion caused degranulation and vacuole formation. However, tetrodotoxin (2 x 10(-6) mol/l) did not prevent the bethanechol-enhanced secretion by the Paneth cells. NaF (1 x 10(-2) mol/l) and AlCl3 (1 x 10(-5) mol/l) induced massive exocytosis of the Paneth cells; the exocytotic figures were similar to those observed in mice stimulated by bethanechol. G-protein activation was followed by a sequence of intracellular events, resulting in exocytosis.

Ultrastructure of Paneth cells in the intestine of various mammals

Paneth cells in the following species were observed under an electron microscope: human, rhesus monkey, hare, guinea pig, rat, nude rat, mouse, golden hamster, and insect feeder bat. Secretory granules containing homogeneous electron-dense materials were observed in the Paneth cells of humans, monkeys, hares, guinea pigs, and bats; mouse Paneth-cell granules were bipartite (central core and peripheral halo), and the Paneth cells in rats and golden hamsters had secretory granules showing various electron densities. In humans, monkeys, and bats, immature granules near the Golgi apparatus sometimes showed bipartite substructure. The number and size of secretory granules were also diverse among various animal species. Some lysosome-like bodies were commonly observed in peri- or supranuclear regions, though the size and shape of the bodies differed from cell to cell. In apical cytoplasm, small clear vesicles (100-200 nm diameter) were more-or-less observed in all species examined, and it was especially note that rat Paneth cells contained many clear vesicles. Small dense-cored vesicles (150-200 nm diameter) were rare. It is unlikely that the various ultrastructural features of Paneth cells correlate with the phylogenetical classification.

Effects of cholecystokinin and carbamylcholine on Paneth cell secretion in mice: a comparison with pancreatic acinar cells

To confirm whether the Paneth cells of mice (ICR, male, 10-12 weeks old) have the same secretory response to hormonal and cholinergic stimulation as do pancreatic acinar cells, ultrastructural changes of Paneth cells and pancreatic acinar cells 1 hr after administration of various doses of cholecystokinin (octapeptide, CCK-8) and carbamylcholine were morphometrically assessed. After maximal (1.5 micrograms/kg intraperitoneally [i.p.]) and supramaximal (15 micrograms/kg, i.p.) stimulation by CCK-8, pancreatic acinar cells showed, respectively, degranulation or disturbance of secretion (e.g., an increase in lysosome-like bodies, aggregation of zymogen granules). The Paneth cells, however, were almost unchanged in the parameters examined. After carbamylcholine injection (1,000 micrograms/kg, subcutaneously [s.c.]), both pancreatic acinar cells and Paneth cells showed degranulation. Paneth cells sometimes developed large vacuoles, probably formed after massive exocytosis; such vacuoles were not observed in pancreatic acinar cells. It is suggested that Paneth cells and pancreatic acinar cells have different secretory responses. Paneth cell secretion, which possibly plays a role in controlling the intestinal bacterial milieu, may be stimulated by cholinergic rather than hormonal mechanisms.

Atropine inhibits the degranulation of Paneth cells in ex-germ-free mice

Previous studies have shown that the secretory products of Paneth cells contain antibacterial agents (lysozyme, IgA) that are affected by the bacterial milieu in the intestine. To investigate whether Paneth-cell secretion is controlled via cholinergic mechanisms, the ultrastructure of Paneth cells was studied in four animal groups: (1) germ-free (GF) control mice (Jcl: ICR [GN], male, 13 weeks old), (2) GF mice injected subcutaneously with atropine sulfate (200 mg/kg body weight, dissolved in physiological saline 20 mg/ml), (3) ex-GF mice inoculated with feces from specific-pathogen-free (SPF) mice, and (4) ex-GF mice injected with atropine and inoculated with feces from SPF mice. In ex-GF mice inoculated with feces, 70-90% of the Paneth cells showed fewer secretory granules than those from GF mice (p less than 0.01). Approximately 30% of the Paneth cells had a large vacuole (3-10 micron diameter) in the apical cytoplasm. Exocytosed electron-dense material from secretory granules was observed in a few crypt lumens. In ex-GF mice inoculated with feces and given atropine, about 90% of the Paneth cells contained numerous secretory granules, like those in GF control mice, but vacuolated Paneth cells and exocytotic figures were rare; thus the secretion of Paneth cells was blocked by atropine. It is therefore possible that the bacterial milieu in the intestine affects the secretory activity of Paneth cells via cholinergic mechanisms.

Effect of live and heat-killed bacteria on the secretory activity of Paneth cells in germ-free mice

Germ-free mice were given live or heat-killed facultative anaerobes, and the ultrastructure of ileal Paneth cells was quantitatively examined with special reference to secretory granules showing a bipartite substructure (central core and peripheral halo). After administering live or heat-killed bacteria, there was a decrease in the area occupied by the cores of secretory granules in Paneth cells, and exocytosed core material was observed in the crypt lumen. There were no changes in the area occupied by the halo of secretory granules. None of the examined Paneth cells phagocytosed bacteria. It is concluded that certain bacteria may affect the secretion of antibacterial agents contained in the secretory granules of Paneth cells.

Immunohistochemical observations of immunoglobulin A in the Paneth cells of germ-free and formerly-germ-free rats

The localization of secretory immunoglobulin A (IgA) in Paneth cells was immunohistochemically studied in germ-free (Gf) and ex-Gf rats that had been injected with feces obtained from specific-pathogen-free (SPF) rats. In Gf as well as SPF rats, the secretory granules of Paneth cells and the brush borders of crypt cells exhibited IgA immunoreactivity. At 12 and 24 h after inoculation, it was found that, concomitant with the occurrence of considerable degranulation, the IgA immunoreactivity in Paneth cells disappeared, except of the margin of supranuclear vacuoles. In contrast, the IgA immunoreactivity of the crypt-cell brush borders was unchanged. Four days after inoculation, secretory granules exhibiting IgA immunoreactivity reaccumulated in Paneth cells. The present study suggests that Paneth cells regulate the bacterial milieu in the intestine by releasing secretory granules containing IgA into the crypt lumen.

Changes in the Paneth cell population of human small intestine assessed by image analysis of the secretory granule area

Estimates of the Paneth cell population in human jejunum and ileum were made using measurement of the granule area in micron2 by image analysis in a defined number of crypts. This figure was preferable to granule area per mm as there was a significant difference in crypts per mm between biopsies and surgical samples. In the jejunum no significant difference was found between normal children and adults with and without peptic ulcer. In adults with subtotal or partial villous atrophy the decrease in area was not statistically significant and there was no decrease in area in children with partial villous atrophy and coeliac disease. There was a marked increase in granule area in the jejunum of patients who had had a previous partial gastrectomy which was statistically significant. In the ileum patients with carcinoma of the caecum had higher values than patients with non-inflammatory non-malignant conditions but this was not statistically significant and two patients with Crohn's disease had an increased granule area. Paneth cell populations are affected by alterations in the intestinal luminal environment due to previous surgery or neoplastic or inflammatory disease.

A quantitative morphometric analysis of rat ileal Thiry-Vella fistulae

Controversy exists regarding the mechanism and degree of mucosal alterations occurring in defunctionalized segments of intestine. This study compares the results of a quantitative analysis of mucosal components, including Paneth cells and immunocytes, between in-continuity and defunctionalized (Thiry-Vella) segments of rat ileum. The micrometer component quantitator was used for the light microscopic morphometric analysis. Intracellular lysozyme and IgA were identified employing the unlabeled antibody enzyme immunohistochemical staining technique. The vol% of the ileal mucosal components of animals from the control group and from the in-continuity segments of the experimental group were comparable. Analysis of the Thiry-Vella fistulae, however, revealed a statistically significant decrease in the vol% of columnar epithelial cells and increase in the vol% of lysozyme-containing Paneth cells and interstitium of the lamina propria. Since Thiry-Vella fistulae are neurovascularly intact, mucosal alterations imply a causal relationship to interaction with chyme. The data suggest that chyme has both a stimulatory (on the columnar epithelium) and suppressive (on the the Paneth cell population) effect. The vol% of IgA-containing Paneth cells and the percentage of the lamina propria represented by IgA-containing immunocytes were also substantially decreased. Normally secretory IgA is the immunoglobulin of highest concentration intraluminally and among immunocytes within the lamina propria, presumably in response to local antigenic stimulation. The presence of immunoglobulin within Paneth cells may reflect the phagocytosis of immunoglobulin complexed antigens. The data suggest that the degree of local antigenic stimulation is decreased in Thiry-Vella fistulae.