Showing papers on "Crypt published in 1997"

Crypt stem cell survival in the mouse intestinal epithelium is regulated by prostaglandins synthesized through cyclooxygenase-1.

Abstract: Prostaglandins (PGs) are important mediators of epithelial integrity and function in the gastrointestinal tract. Relatively little is known, however, about the mechanism by which PGs affect stem cells in the intestine during normal epithelial turnover, or during wound repair. PGs are synthesized from arachidonate by either of two cyclooxygenases, cyclooxygenase-1 (Cox-1) or cyclooxygenase-2 (Cox-2), which are present in a wide variety of mamalian cells. Cox-1 is thought to be a constitutively expressed enzyme, and the expression of Cox-2 is inducible by cytokines or other stimuli in a variety of cell types. We investigated the role of PGs in mouse intestinal stem cell survival and proliferation following radiation injury. The number of surviving crypt stem cells was determined 3.5 d after irradiation by the microcolony assay. Radiation injury induced a dose-dependent decrease in the number of surviving crypts. Indomethacin, an inhibitor of Cox-1 and Cox-2, further reduced the number of surviving crypts in irradiated mice. The indomethacin dose response for inhibition of PGE2 production and reduction of crypt survival were similar. DimethylPGE2 reversed the indomethacin-induced decrease in crypt survival. Selective Cox-2 inhibitors had no effect on crypt survival. PGE2, Cox-1 mRNA, and Cox-1 protein levels all increase in the 3 d after irradiation. Immunohistochemistry for Cox-1 demonstrated localization in epithelial cells of the crypt in the unirradiated mouse, and in the regenerating crypt epithelium in the irradiated mouse. We conclude that radiation injury results in increased Cox-1 levels in crypt stem cells and their progeny, and that PGE2 produced through Cox-1 promotes crypt stem cell survival and proliferation.

Morphological and Molecular Processes of Polyp Formation in ApcΔ716 Knockout Mice

Abstract: Mutations in the human adenomatous polyposis coli (APC) gene are responsible for not only familial adenomatous polyposis but also many sporadic cancers of the digestive tract. Using homologous recombination in embryonic stem cells, we recently constructed Apc gene knockout mice that contained a truncation mutation at codon 716 (Apc(delta716)). The heterozygous mice developed numerous intestinal polyps. All microadenomas dissected from nascent polyps had already lost the wild-type allele, indicating the loss of heterozygosity (M. Oshima et al., Proc. Natl. Acad. Sci. USA, 92: 4482-4486, 1995). We also demonstrated that cyclooxygenase 2 is induced in the polyps at an early stage and plays a key role in polyp development (M. Oshima et al., Cell 87: 803-809, 1996). We have analyzed the process of polyp development in these mice both at morphological and molecular levels. A small intestinal microadenoma is initiated as an outpocketing pouch in a single crypt and develops into the inner (lacteal) side of a neighboring villus forming a double-layer nascent polyp. The microadenoma then enlarges and gets folded inside the villus. When it fills the intravillous space, it expands downward and extends into adjoining villi, rather than rupturing into the intestinal lumen. During this course of development, the basement membrane remains intact, and the labeling index of the microadenoma cells is similar to that of the normal crypt epithelium. As in the crypt cells, neither transforming growth factor beta1 nor its receptor type II is expressed in the microadenoma cells. No hot spot mutations in the K-ras gene are found in the microadenoma tissue during these early stages of polyp development. Essentially, the same results have been obtained for the colonic polyps as well. These results suggest that early adenomas in the Apc(delta716) polyps are very similar to the normal proliferating cells of the crypt except for the lack of directed migration along the crypt-villus axis.

Pretreatment with transforming growth factor beta-3 protects small intestinal stem cells against radiation damage in vivo.

Abstract: The gastrointestinal tract, with its rapid cell replacement, is sensitive to cytotoxic damage and can be a site of dose-limiting toxicity in cancer therapy. Here, we have investigated the use of one growth modulator to manipulate the cell cycle status of gastrointestinal stem cells before cytotoxic exposure to minimize damage to this normal tissue. Transforming growth factor beta-3 (TGF-beta3), a known inhibitor of cell cycle progression through G1, was used to alter intestinal crypt stem cell sensitivity before 12-16 Gy of gamma irradiation, which was used as a model cytotoxic agent. Using a crypt microcolony assay as a measure of functional competence of gastrointestinal stem cells, it was shown that the administration of TGF-beta3 over a 24-h period before irradiation increased the number of surviving crypts by four- to six-fold. To test whether changes in crypt survival are reflected in the well-being of the animal, survival time analyses were performed. After 14.5 Gy of radiation, only 35% of the animals survived within a period of about 12 days, while prior treatment with TGF-beta3 provided significant protection against this early gastrointestinal animal death, with 95% of the treated animals surviving for greater than 30 days.

Effects of epidermal growth factor and dimethylhydrazine on crypt size, cell proliferation, and crypt fission in the rat colon. Cell proliferation and crypt fission are controlled independently.

Abstract: Crypt fission is now established as an important mechanism of intestinal growth and regeneration. It has been proposed that increased crypt size is the stimulus for crypt fission, because crypts preparing for fission are generally larger. Consequently, we investigated the effects of epidermal growth factor (EGF) and dimethylhydrazine, which are both known to stimulate crypt cell proliferation, on crypt fission in the rat intestine. We also examined whether the effects of EGF on both proliferation and crypt fission are modified by the pretreatment with dimethylhydrazine for 16 weeks, dimethylhydrazine was then discontinued for 8 weeks, followed by intravenous infusion of EGF for 1 week. There were four groups: vehicle alone, EGF alone, dimethylhydrazine alone, and dimethylhydrazine followed by EGF infusion. The rats were killed at 25 weeks and rates of intestinal crypt cell production, crypt size, and crypt fission were determined. Intravenously infused EGF significantly increased crypt cell production rate, but the magnitude of the effect decreased from the proximal to the distal colon. EGF caused an increase in crypt area, possibly reflecting an increase in crypt size. Importantly dimethylhydrazine had no significant effect on crypt cell production rate nor on crypt area in the distal colon, but it did cause an increase in crypt area in the mid-colon. The crypt fission index was significantly decreased by EGF and increased by dimethylhydrazine. There was no qualitative interaction between EGF and dimethylhydrazine. These results demonstrate the marked proliferative effect of intravenously infused EGF in the colon of orally fed rats, with significant site effects (P = 0.0007); the effect was greatest in the proximal colon and disappeared in the distal colon. The observation that EGF reduced crypt fission indicates that increased cell proliferation, per se, is not a stimulus for crypt fission. This is further supported by the observation that dimethylhydrazine increases crypt fission in crypts of normal size in the distal colon without significantly increasing cell proliferation. These results suggest that increasing crypt cellularity by proliferation is not sufficient to induce crypt fission, and factors other than increased crypt size by proliferation can control crypt fission. It is also probable that cell proliferation and crypt fission are independently regulated. Crypt fission appears to play a considerable role in the intestinal response to carcinogens.

Effect of chronic inflammation on electrolyte transport in rabbit ileal villus and crypt cells.

Abstract: The effect of chronic inflammation on electrolyte transport in rabbit ileal villus and crypt cells was determined with the use of a rabbit model of chronic ileitis. In both cells, Na+/H+ exchange was monitored by following recovery from an acid load, and Cl-/HCO3- exchange was monitored by following recovery from an alkaline load. In villus cells, recovery from an acid load was not affected; however, recovery from an alkaline load was slowed. These data suggest that chronic inflammation inhibits Cl-/HCO3- exchange in villus cells. In contrast, in crypt cells, recovery from an alkaline load was unaffected, whereas recovery from an acid load was accelerated. These data suggest that chronic inflammation stimulates Na+/H+ exchange in crypt cells. Inhibition of Cl-/HCO3- exchange in villus cells would be expected to inhibit coupled NaCl absorption, which occurs by the coupling of brush-border membrane (BBM) Na+/H+ and Cl-/HCO3- exchange. Stimulation of Na+/H+ exchange in crypt cells, known to be present only on the basolateral membrane, alkalinizes the cell. This alkalinization may stimulate BBM Cl-/HCO3- exchange, resulting in HCO3- secretion. Thus these unique alterations in transporter activity suggest that different endogenous immune-inflammatory mediators may have differing effects on specific transporters in villus and crypt cells in the chronically inflamed ileum.

Glycoconjugate Expression Defines the Origin and Differentiation Pathway of Intestinal M-cells

Abstract: Intestinal M-cells are specialized epithelial cells located in the domes of the gut-associated lymphoid tissues, which transport antigens from the lumen to the underlying lymphoid tissue, thereby initiating immune reactions. It is assumed that M-cells arise from stem cells in the crypts, from which they migrate to the top of the domes. To study the differentiation pathway of M-cells, we used the rabbit cecal lymphoid patch in which the M-cells express high levels of alpha 1-2-linked fucose and N-acetyl-galactosamine residues in their apical membrane. Dome areas were labeled with fluorescein- and rhodamine-conjugated lectins specific for alpha 1-2-linked fucose and N-acetyl-galactosamine in vivo and in vitro, and were observed with confocal laser scanning microscopy. Ultrathin sections were double labeled with lectin-gold conjugates and the labeling density was quantified by computer-based image analysis. All cecal patch M-cells expressed alpha 1-2-linked fucose and N-acetyl-galactosamine, but the amount of the two saccharides varied considerably depending on the position of the M-cells at the base, flank, or top of the dome. In eight of 18 rabbits studied, radial strips of M-cells with common glycosylation patterns were observed, each strip associated with an individual crypt. Confocal microscopy revealed that lectin-labeled M-cells were not restricted to the dome epithelium but were also detected in the upper third of crypts surrounding the domes. The results show that M-cells are heterogeneous concerning the glycosylation pattern of membrane glycoconjugates. This pattern is modified as the M-cells differentiate and migrate from the base to the top of the dome. Radial strips of M-cells with a common proclivity of glycoconjugate expression suggest that those M-cells that derive from the same crypt have a clonal origin. The presence of (pre-) M-cells in the crypts surrounding the domes indicates that M-cells derive directly from undifferentiated crypt cells and do not develop from differentiated enterocytes.

ATP increases [Ca2+]i and ion secretion via a basolateral P2Y-receptor in rat distal colonic mucosa

Abstract: Under resting conditions the mammalian distal colon is a NaCl-absorptive epithelium. NaCl absorption occurs at surface cells in colonic crypts. Intracellular Ca2+ or cAMP are important second messengers that activate NaCl secretion, a function that is most pronounced in crypt bases. In the present study we examined the effect of extracellular ATP on isolated crypts of rat distal colon using the fura-2 technique. Intracellular Ca2+ ([Ca2+]i) was measured spectrofluorimetrically either by photon counting or video imaging. ATP reversibly increased [Ca2+]i in crypt base cells with an EC50 of 4.5 μmol/l (n = 11). This [Ca2+]i increase was composed of an initial peak, reflecting intracellular store release, and a secondary plateau phase reflecting transmembrane influx. Digital video imaging revealed that agonist-induced [Ca2+]i elevations were most marked at the crypt base. In the middle part of the crypt ATP induced smaller increases of [Ca2+]i (peak and plateau) as compared to basal cells and in surface cells this [Ca2+]i transient was even further reduced. Attempts to identify the relevant P2-receptor demonstrated the following rank order of potency: 2MeS-ATP > ADP ≥ ATP >> AMP > UTP > AMP-PCP > adenosine. In Ussing chamber experiments ATP (1 mmol/l) functioned as a secretagogue, increasing transepithelial voltage (Vte) and equivalent short-circuit current (Isc): ΔIsc = –36.4 ± 5.4 μA/cm2, n = 17. Adenosine itself (1 mmol/l) induced an increase of Isc of similar magnitude to that induced by ATP: ΔIsc = –55.1 ± 8.4 μA/cm2, n = 9. The effect of adenosine, but not that of ATP, was fully inhibited by the A1/A2-receptor antagonist 8-(p-sulphophenyl)theophylline, 0.5 mmol/l, n = 4. Together these data indicate that: (1) basolateral ATP induces [Ca2+]i in isolated rat colonic crypts and acts as a secretagogue in the distal rat colon; (2) a basolateral P2Y-receptor is responsible for this ATP-induced NaCl secretion; (3) the ability of ATP to increase Isc in Ussing chamber experiments is not mediated via adenosine; and (4) the agonist-induced [Ca2+]i signals are mostly located in the crypt base, which is the secretory part of the colonic crypt.

APC mutation and the crypt cycle in murine and human intestine.

Abstract: Dysplastic colon adenomas are thought to arise from growth of clones of APC -/- colonic epithelial cells. Isolated clusters of dysplastic crypts are often observed in patients with familial adenomatous polyposis. These patients have genotype APC +/-, and the clusters of dysplastic crypts (called microadenoma or aberrant crypt foci) are thought to represent an early stage in the expansion of a mutant clone of APC -/- cells. It is thought that the growth of these clusters of mutant crypts results from crypt replication through a process similar to what occurs in the normal crypt cycle. We measured the relative replication rate of mutant crypts by analyzing the size of clusters of mutant crypts in APC +/- individuals and found that mutant APC -/- crypts replicate more rapidly than do normal APC +/- (i.e., nonneoplastic) crypts. In contrast, the replication rate of mutant crypts in Apc +/- mice is not significantly different from that of normal crypts, thus supporting previous findings that aberrant crypt foci do not contribute significantly to the colon adenoma population in adult Apc +/- mice. Intriguingly, we found an effect of Apc heterozygosity on the frequency of branching crypts in young mice.

p53 deficiency sensitizes clonogenic cells to irradiation in the large but not the small intestine.

Abstract: The role of p53 in the survival of irradiated crypts in the small intestine and three regions of the large intestine (cecum, mid-colon and rectum) was assessed by comparing the responses in p53 null, p53 heterozygous and wild-type mice. There was no difference in the levels of crypt survival in the small intestine between the three genotypes, although the rate of cell depletion and regeneration in the null mice appeared slower. In the large intestine, crypt survival was lowest in the null mice compared to the other genotypes, in particular after high doses. The levels of crypt survival in the heterozygotes were not significantly different from those in the wild-type mice. Hence the greater radioresistance of crypts in the colon than in the small intestine, reported previously by us and others using various other mouse strains, may be partly attributable to the presence of p53. This effect is not readily explained by current knowledge concerning the decreased p53 expression and the greater expression of the survival gene Bcl2 in the stem cell zone of crypts in the colon compared to those in the small intestine. Reduced repair associated with the lack of a G2-phase checkpoint delay, the predominant arrest point for intestinal cells, is a possible explanation for the decrease in survival.

The trophic action of growth hormone, insulin-like growth factor-I, and insulin on human duodenal mucosa cultured in vitro.

Abstract: BACKGROUND: Experimental evidence suggests that hormones may regulate small intestinal adaptation after surgical resection. AIMS: To characterise the effect of recombinant human growth hormone (GH), insulin-like growth factor-I (IGF-I) and insulin on crypt epithelial cell proliferation in the human duodenal mucosa cultured in vitro. PATIENTS: Thirty nine adults had endoscopic duodenal biopsy specimens taken, which were histologically normal and pair matched specimens from each patient acted as their own control. METHODS: Paired biopsy specimens from patients were cultured in vitro, with or without the addition of GH (0.004 IU/ml), IGF-I (400 ng/ml) or insulin (50 micrograms/ml), alone or in combination. After 22 hours, vincristine sulphate was added to the cultures and three hours later specimens were removed and fixed, and DNA stained by the Feulgen method. Intestinal crypts were microdissected and crypt epithelial cell proliferation determined by estimating mean numbers of accumulated metaphase arrests/crypt present in tests and controls between 22-25 hours of culture. RESULTS: The addition of GH, IGF-I, and insulin, alone or in combination, significantly increased crypt epithelial cell proliferation in test explants compared with controls. IGF-I was most potent and its trophic effect was modified by insulin. CONCLUSIONS: GH, IGF-I, and insulin are involved in the regulation of crypt cell proliferation in the human small intestine in vitro and possibly in vivo.

γ-ray-induced apoptosis in transgenic mice with proliferative abnormalities in their intestinal epithelium: Re-entry of villus enterocytes into the cell cycle does not affect their radioresistance but enhances the radiosensitivity of the crypt by inducing p53

Abstract: γ-Ray-induced apoptosis in transgenic mice with proliferative abnormalities in their intestinal epithelium: re-entry of villus enterocytes into the cell cycle does not affect their radioresistance but enhances the radiosensitivity of the crypt by inducing p53

The relationship between myenteric neuronal denervation, smooth muscle thickening and epithelial cell proliferation in the rat colon.

Abstract: The effects of myenteric neuronal denervation on smooth muscle thickening and epithelial cell proliferation were studied in the descending colon of rats treated by serosal application of 2 mM benzalkonium chloride (BAC) for 30 min. Control animals were treated with saline (0.9% NaCl). The animals were divided into six groups of 13 animals each and killed 10, 45 and 120 days after BAC treatment. A significant reduction in neuron number was observed in the myenteric plexus of animals treated with BAC, as well as smooth muscle thickening and an increase in crypt cell population, crypt cell production per crypt and a decrease in cell cycle time. These findings permit us to conclude that a relationship may exist between the increase of epithelial cell proliferation, smooth muscle thickening and myenteric neuron denervation in the descending colon caused by BAC, the latter probably playing an important role in the integration of the other two.

Butyrate inhibits deoxycholate induced increase in colonic mucosal DNA and protein synthesis In Vivo

Abstract: PURPOSE: Crypt surface hyperproliferation is an intermediate biomarker of colon cancer risk.In vitro studies indicate that the short-chain fatty acid and antineoplastic agent butyrate may reverse the crypt surface hyperproliferation induced by the secondary bile acid and tumor promoter, deoxycholate. We hypothesized that butyrate may reverse deoxycholate-induced crypt surface proliferation in vivo.METHODS: Thirty-one Sprague-Dawley rats (250–300 g) underwent surgical isolation of the colon and 24-hour luminal instillation of either sodium chloride, butyrate, deoxycholate, or butyrate plus deoxycholate (all solutions, 2 ml; pH 7; total sodium = 20 mM). Study variables included colon weight, mucosal DNA, mucosal protein, and proliferating cell nuclear antigen immunohistochemistry, labeling of which was determined in five crypt compartments from base to surface (12 crypts per rat). Labeling indexes were calculated as proliferating cell nuclear antigen immunohistochemistry-labeled cells divided by total counted cells in the whole colonic crypt and each of five crypt compartments. The Φ oh value (an index of premalignant risk) was calculated as the ratio of labeled cells in the two surface compartments divided by the total labeled cells. RESULTS: Deoxycholate significantly increased colon wet weight, mucosal protein, total crypt labeling indexes, crypt surface labeling indexes, and the Φ oh value and raised the mucosal DNA content. Butyrate alone slightly reduced total mucosal DNA and protein content. The combination of butyrate plus deoxycholate significantly decreased mucosal DNA and tended to reduce mucosal protein compared with deoxycholate alone. In contrast to prior in vitro findings, butyrate plus deoxycholate did not reverse the deoxycholate-induced surface hyperproliferative changes as measured by proliferating cell nuclear antigen labeling. CONCLUSIONS: Because co-treatment with butyrate plus deoxycholate inhibits deoxycholate-induced increases in total mucosal DNA and protein content, we conclude that butyrate may play a role in maintaining the proliferative balance of the colonic mucosa,in vivo.However, co-treatment with butyrate plus deoxycholate does not reverse the deoxycholate induced increases in colon weight and proliferating cell nuclear antigen labeling indexes under the studied experimental conditions.

Characterization of isolated duodenal epithelial cells along a crypt-villus axis in rats fed diets with different iron content.

Abstract: The intestinal mucosa is characterized by cell proliferation, commitment, differentiation, digestion and absorption. These processes occur at specified locations along the crypt to villus axis. A technique is reported for the isolation of cells along this axis which allows the study of any one of these processes in an enriched population of cells. As an example, the uptake of transferrin-bound iron by enterocytes was studied. Rats were fed diets normal, high (30% carbonyl iron) or low in iron for 12 days. Cells from either the duodenum or ileum were isolated by incubating in a Ca(2+)-, Mg2+-free, cation chelating solution for varying periods. The incorporation of thymidine into DNA was measured in these cells as a marker of the crypt region, while alkaline phosphatase and sucrase activities marked mature enterocytes. The in vivo uptake of transferrin-bound 59Fe was measured in cells isolated either 2 or 4 h after intravenous injection. This procedure resulted in the isolation of 10 fractions of viable cells. Earlier fractions were enriched at least 10-fold in villus cells and the last fractions in crypt cells. Cells in intermediate fractions were at various stages of development. Uptake of transferrin-bound iron into enterocytes was highest with feeding an iron-loaded diet compared with control or iron-deficient diets. However, with all diets uptake was highest in crypt cells and this fell at the crypt-villus junction to be only 25%, as high at the villus tip as the crypt. A technique for the reproducible isolation of viable enterocytes along a crypt-villus axis is described. Transferrin receptor activity changes with maturation of the enterocyte.

Characterization of sodium and chloride conductances in preneoplastic and neoplastic murine colonocytes

Abstract: Glucocorticoids, such as dexamethasone, induce amiloride-sensitive Na+ conductances in rat distal colon epithelium. The activity of these conductances diminishes from the surface to the base of the crypt whereas cAMP-stimulated Cl–secretion decreases from the crypt base to the surface. These gradients are likely to be perturbed during carcinogenesis. We therefore determined the magnitude of Na+ and Cl–conductances in colonocytes isolated from normal and carcinogen-treated rats. Colon carcinogenesis was induced by injection of dimethylhydrazine (DMH) (18 mg/kg) for 5 weeks. Before sacrifice animals were treated for 3 days with dexamethasone. Colonocyte populations from the surface to the crypt base (C1–C5) were harvested from the distal colon by a Ca2+-chelating procedure. The activity of Na+ conductances was determined by uptake of 22Na+ by surface and crypt colonocyte populations and by membrane vesicles in the presence and absence of 10 μM amiloride. In control rats Na+ conductance was highest in surface colonocytes and absent in the crypt base. As early as 2 weeks after initiation of DMH treatment amiloride-inhibited Na+ uptake was virtually absent in the upper crypt. Transcriptional assessment of the α-, β- and γ-subunits that constitute the epithelial Na+ channel revealed that DMH treatment reduces the expression of β-subunit mRNA. We then examined 36Cl–efflux from isolated colonocytes of normal and carcinogen-treated rats in response to forskolin (0.01 mM). Forskolin induced a marked rise in cAMP in lower crypt cells concomitant with a significant stimulation of 36Cl–efflux. Intracellular cAMP increased in upper crypt cells in response to forskolin without an increase in 36Cl–efflux. By contrast, upper crypt colonocytes from DMH-treated rats showed forskolin-stimulated efflux beginning 4 weeks after initiation of treatment. We conclude that induction of Na+ conductances by glucocorticoids is inhibited during the early stages of chemical carcinogenesis due to lack of induction of the β-subunit of the channel. By contrast, Cl–transport is stimulated both in surface and lower crypt cell compartments during different stages of chemical carcinogenesis.

10 – Stem cell repertoire in the intestine*

Abstract: This chapter focuses on stem cell repertoire in the intestine. One of the more important characteristics of intestinal stem cells is pluripotentiality , or the ability to give rise to cells of more than one lineage. However, this is a stem cell property which, in epithelia such as that lining the gastrointestinal tract, has received much less attention than other putative properties. Stem cells in the gut are specifically located, and in epithelia, a realization has emerged that, notionally at any rate, stem cells should be found at the origin of the cell flux . In the colonic and small intestinal crypt, cell migration apparently begins at the base of the crypt, and cells migrate from here, emerging onto the surface in the colon or onto the villi in the small intestine; consequently, the basal crypt cells, or a subset thereof, are candidate stem cells. In the gastric gland the kinetic arrangements are quite different: cell proliferation is confined to the middle portion of the tubule, and cells are thought to migrate bidirectionally to supply the gastric surface and the base of the tubule. This chapter discusses in detail about cell lineages in the intestinal epithelium. The chapter also explains about pluripotential colorectal carcinoma cell lines. The chapter also elaborates about the control of gut cell lineage development.

The effect of pinealectomy on the crypts of defunctioned rat colon

Abstract: Previously it has been found that 6 months after pinealectomy hyperplasia occurred in the crypt cells of the rat small bowel and colon. It is also known that defunctioning a loop of colon, using a colostomy, results in crypt cell hypoplasia, emphasizing the prime importance of luminal factors in the control of crypt cell proliferation. To determine if the effects of pinealectomy on the colon could be modified by the absence of colonic luminal contents, the crypt cell kinetic effects of combined pinealectomy and defunctioning of a colonic loop by colostomy for 6 months were examined by using a stathmokinetic technique. It was found that the hypoproliferative effect of defunctioning a loop of colon was largely but not completely overridden by the hyperproliferative effect of pinealectomy. However, previously it has been found that in the rat small bowel, the hypoproliferative effects of defunctioning a loop were completely overridden by the effect of pinealectomy. This and other evidence suggests that the role of the pineal in the control of crypt cell proliferation in the colon may possibly be different from its role in the small bowel. There is other evidence of possible involvement of the pineal in carcinoma of the colon and it is possible that its role in the colon may be to prevent excessive mitotic activity, which is known to be present in the early stages of carcinoma. The Pineal gland may have a role in modulating the usual mechanisms of crypt cell mitotic control.

Short chain fatty acids inhibit the expression of the neutrophil chemoattractant, interleukin 8, in the Caco-2 intestinal cell line.

Abstract: The histologic appearance of active ulcerative colitis includes an intense lymphoplasmocytosis limited to the mucosa and submucosa often notable for a neutrophilic infiltrate invading the colonic epithelium (crypt abscess). Multiple investigators have shown that the colonic epithelium is in a hyperproliferative state with expansion of the proliferative compartment from the lower crypt to the upper crypt extending to the surface epithelium (1,2). This hyperproliferative state is independent of the degree of inflammation and the duration of the disease and exists even when the disease is in a quiescent state (1,2). Similar hyperproliferative states have been observed in patients at risk for colonic malignancy such as in familial polyposis coli, sporadic colon adenomas, and familial nonpolyposis colon cancer (3). An intriguing observation made by Scheppach et al. (4) is that the labeling index of colonocytes in the upper crypt of patients with ulcerative colitis fell to that of normal healthy controls after treatment with butyrate enemas. This suggests that butyrate may fundamentally alter the state of proliferation, and perhaps differentiation, of colonic epithelial cells in ulcerative colitis.

The steroid vitamin D3 reduces cell proliferation in human duodenal epithelium

Abstract: 1. The active metabolite of vitamin D 3 , 1,25-di-hydroxyvitamin D 3 , controls calcium absorption in the human duodenum, an effect that is mediated by mucosal vitamin D receptor expression. Functional vitamin D receptor signalling in the human colon is suggested by the reduced colonic mucosal cell proliferation seen in response to 1,25-dihydroxyvitamin D 3 . Thus 1,25-dihydroxyvitamin D 3 might be expected to reduce cell proliferation in the small-bowel epithelium. 2. We have used an organ-culture system combined with the metaphase arrest technique to study the effects of 1,25-dihydroxyvitamin D 3 on human duodenal mucosal proliferation. To validate our technique, multiple human mucosal explants were established in organ culture and vincristine (0.6 μg/ml) was added at 10 h. Explants were removed sequentially from 10 to 15 h and metaphase arrest figures were demonstrated by using the Feulgen reaction. The mean number of metaphase arrest figures was plotted against time in culture to show a linear accumulation of metaphases between 11 and 15 h (correlation coefficient = 0.93, r 2 = 0.87, P<0.0001). The mean crypt cell production rate was 2.01 (0.27) cells/h per crypt. 3. Paired normal duodenal mucosal biopsies from six patients were then established in organ culture with or without 10 -10 mol/l (100 pmol/l) 1,25-di-hydroxyvitamin D 3 . The crypt cell production rate was determined between 12 and 15 h after vincristine-induced metaphase arrest. 1,25-Dihydroxy-vitamin D 3 reduced the median crypt cell production rate from 2.42 (1.15-4.82) to 1.41 (0.03-2.05) cells/h per crypt (P<0.05). Thus, vitamin D 3 reduces human duodenal epithelial cell proliferation.