Crypt Growth Research Articles

Landmark‐based 3D Morphometrics of the Developing Human Dentition in the Middle Trimester

Human primary tooth formation begins around 6 weeks in utero and by the time a baby is born, all 20 teeth have mineralized and are embedded in the jaw bone. Our study is addressing the period during which tooth morphogenesis and jaw development are taking place, the middle trimester. The tooth‐bone relationship involves inductive interactions between the condensed mesenchyme of the dental follicle surrounding the tooth germs and the non‐dental mesenchyme of the jaws. As teeth pass through bud, cap and bell stages, intramembranous bone is being deposited by osteoblasts but the patterning of the bone in relation to the teeth is not well understood. From studies in mouse, the tooth follicle is thought to induce bone and in turn the bone is thought to restrict tooth organ growth. Mouse molars are completely encased in bone as soon as the crown is completed. However in humans the bone surrounding tooth organs is fenestrated. The buccal and occlusal surfaces of the first molar (m1) and canine (c) are not covered by bone whereas the incisors (lateral incisor – i2, central incisor – i1) are surrounded by bone on buccal, lingual, gingival, mesial and distal. Therefore we wondered whether crypt growth is isometric or allometric and whether there were differences between the tooth morphotypes. To answer this question, we scanned 25 intact fetal jaws with microCT from a collection of human specimens maintained at UBC. Scans were imported into Amira (Thermo‐Fisher) and used for segmentation or landmark placement. Landmarks were placed in a consistent manner on all surfaces of the bony tooth crypt (Fig. B,D) and then exported to MorphoJ for morphological analyses (Fig. A,C). In addition segmented tooth volumes and linear dimensions were measured in Amira.The principal component and canonical variate analysis revealed that there are significant shape differences in the crypts between 12–14 weeks and 17–19 weeks. The intermediate period 15–16 weeks was not significantly different than the early or later timeframes. These trends matched segmented volumetric data for the tooth germs and mandible. Shifts in specific landmarks particularly the buccal landmarks adjacent to m1 and c were observed between the early and late period which is consistent with the lack of constraint by bone on those surfaces (Fig. A). Allometric growth in the occlusal gingival direction was also observed with increased depth to the crypts for all teeth over the developmental period (Fig. C). Some of these changes are consistent with reconstruction data from others showing relatively greater bone resorption on the internal surfaces of the crypt. Our data suggests that the all the tooth germs are interacting with the bone that will later surround the roots. The prominent buccal bulges of m1, plus the formation of the mental foramen on the buccal side of the m1 crypt, may require spatially restricted tissue interactionsSupport or Funding InformationFunded by the Faculty of Dentistry, UBC; Human ethics approval number H08‐0257This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Protective effect of polydatin on radiation-induced injury of intestinal epithelial and endothelial cells.

This study aimed to examine the radioprotective effect of polydatin (PD) on crypt and endothelial cells of the small intestines of C57BL/6 mice that received abdominal irradiation (IR). Mice were treated with 6 MV X-ray (20 Gy) abdominal IR at a dose rate of 200 cGy/min. Thirty minutes before or after IR, mice were intraperitoneally injected with PD. The rate of survival of the mice at 30 days after IR was determined. The duodenum (upper small intestine), jejunum (middle small intestine), and ileum (lower small intestine) were collected and subjected to hematoxylin and eosin staining. Tissue sample sections were analyzed through light microscopy, and the lengths of at least 20 intestinal villi were measured in each group; the average number of crypts was obtained from 10 intestinal samples in each group. Microvessel density was assessed using CD31-positive (brown) vascular endothelial cells/cell clusters. FHs74Int cell proliferation was measured using the CCK-8 assay. PD administration (25 mg/kg) before IR was the most effective in prolonging the survival of C57BL/6 mice. PD reduced radiation-induced injury of intestinal villi, prevented loss of crypts, increased intestinal crypt growth, protected against IR-induced intestinal injury, and enhanced the proliferative potential and reduced the apoptosis of FHs74Int cells after IR. Moreover, PD increased small intestinal MVD and reduced the apoptosis of intestinal microvascular endothelial cells in mice after IR. Therefore, PD was found to be able to protect the two types of cells from radiation damage and to thus alleviate radiation-induced injury of small intestine.

Differential activities and mechanisms of the four R-spondins in potentiating Wnt/β-catenin signaling

The four R-spondins (RSPO1-4) strongly potentiate Wnt signaling and play critical roles in normal development, adult stem cell survival, and cancer development and aggressiveness. All four RSPOs have been suggested to potentiate Wnt signaling by binding to three related receptors, i.e. leucine-rich repeat-containing, G protein-coupled receptors 4, 5, and 6 (LGR4/5/6), and then inducing the clearance of two E3 ubiquitin ligases (RNF43 and ZNRF3) that otherwise would ubiquitinate Wnt receptors for degradation. Here, we show that RSPO1-4 have differential dependence on LGRs in potentiating Wnt/β-catenin signaling and that RSPO2 can enhance this pathway without any LGR. LGR4 knockout (LGR4KO) in HEK293 cells completely abrogated the Wnt/β-catenin signaling response to RSPO1 and RSPO4 and strongly impaired the response to RSPO3. RSPO2, however, retained robust activity albeit with decreased potency. Complete rescue of RSPO1-4 activity in LGR4KO cells required the seven-transmembrane domain of LGR4. Furthermore, an RSPO2 mutant with normal binding affinity to ZNRF3 but no or little binding to LGR4 or LGR5 still potentiated Wnt/β-catenin signaling in vitro, supported the growth of intestinal organoids ex vivo, and stimulated intestinal crypt growth in vivo Mechanistically, RSPO2 could increase Wnt receptor levels in the absence of any LGR without affecting ZNRF3 endocytosis and stability. These findings suggest that RSPO1-4 use distinct mechanisms in regulating Wnt and other signaling pathways, which have important implications for understanding the pleiotropic functions of RSPOs and LGRs in both normal and cancer development.

Whole-mount Enteroid Proliferation Staining.

Small intestinal organoids, otherwise known as enteroids, have become an increasingly utilized model for intestinal biology in vitro as they recapitulate the various epithelial cells within the intestinal crypt (Mahe et al., 2013; Sato et al., 2009). Assessment of growth dynamics within these cultures is an important step to understanding how alterations in gene expression, treatment with protective and toxic agents, and genetic mutations alter properties essential for crypt growth and survival as well as the stem cell properties of the individual cells within the crypt. This protocol describes a method of visualization of proliferating cells within the crypt in three dimensions (Barrett et al., 2015). Whole-mount proliferation staining of enteroids using EdU incorporation enables the researcher to view all proliferating cells within the enteroid as opposed to obtaining growth information in thin slices as would be seen with embedding and sectioning, ensuring a true representation of proliferation from the stem cell compartment to the terminally differentiated cells of the crypt.

Scap is required for sterol synthesis and crypt growth in intestinal mucosa

SREBP cleavage-activating protein (Scap) is an endoplasmic reticulum membrane protein required for cleavage and activation of sterol regulatory element-binding proteins (SREBPs), which activate the transcription of genes in sterol and fatty acid biosynthesis. Liver-specific loss of Scap is well tolerated; hepatic synthesis of sterols and fatty acids is reduced, but mice are otherwise healthy. To determine whether Scap loss is tolerated in the intestine, we generated a mouse model (Vil-Scap(-)) in which tamoxifen-inducible Cre-ER(T2), a fusion protein of Cre recombinase with a mutated ligand binding domain of the human estrogen receptor, ablates Scap in intestinal mucosa. After 4 days of tamoxifen, Vil-Scap(-) mice succumb with a severe enteropathy and near-complete collapse of intestinal mucosa. Organoids grown ex vivo from intestinal crypts of Vil-Scap(-) mice are readily killed when Scap is deleted by 4-hydroxytamoxifen. Death is prevented when culture medium is supplemented with cholesterol and oleate. These data show that, unlike the liver, the intestine requires Scap to sustain tissue integrity by maintaining the high levels of lipid synthesis necessary for proliferation of intestinal crypts.

γδ T-cell-deficient mice show alterations in mucin expression, glycosylation, and goblet cells but maintain an intact mucus layer

Intestinal homeostasis is maintained by a hierarchy of immune defenses acting in concert to minimize contact between luminal microorganisms and the intestinal epithelial cell surface. The intestinal mucus layer, covering the gastrointestinal tract epithelial cells, contributes to mucosal homeostasis by limiting bacterial invasion. In this study, we used γδ T-cell-deficient (TCRδ(-/-)) mice to examine whether and how γδ T-cells modulate the properties of the intestinal mucus layer. Increased susceptibility of TCRδ(-/-) mice to dextran sodium sulfate (DSS)-induced colitis is associated with a reduced number of goblet cells. Alterations in the number of goblet cells and crypt lengths were observed in the small intestine and colon of TCRδ(-/-) mice compared with C57BL/6 wild-type (WT) mice. Addition of keratinocyte growth factor to small intestinal organoid cultures from TCRδ(-/-) mice showed a marked increase in crypt growth and in both goblet cell number and redistribution along the crypts. There was no apparent difference in the thickness or organization of the mucus layer between TCRδ(-/-) and WT mice, as measured in vivo. However, γδ T-cell deficiency led to reduced sialylated mucins in association with increased gene expression of gel-secreting Muc2 and membrane-bound mucins, including Muc13 and Muc17. Collectively, these data provide evidence that γδ T cells play an important role in the maintenance of mucosal homeostasis by regulating mucin expression and promoting goblet cell function in the small intestine.

Colon cancer cells adopt an invasive phenotype without mesenchymal transition in 3-D but not 2-D culture upon combined stimulation with EGF and crypt growth factors.

BackgroundThe intestinal crypt homeostasis is maintained by a combination of growth factors including Wnt, R-Spondin1, Noggin and the epidermal growth factor (EGF). In human colorectal cancer, the Wnt pathway is constitutively activated through genetic and epigenetic alterations in as many as 11 genes encoding components of this crypt stem-cell maintenance mechanism. Although the proliferation of colon cancer cells does not require Wnt, it is possible that colon cancer cells can still respond to the crypt growth factors in the colonic microenvironment. A number of studies have shown that epithelial cells behave differently in 3-D versus 2-D cultures. Because the 3-D conditions more closely mimic the in vivo environment, we examined the effects of Wnt and other crypt growth factors on colon cancer cell growth in 3-D culture.MethodsColon cancer cells were grown in 3-D matrigel supplemented with different combinations of crypt growth factors and colonies were examined for morphology and pathways.ResultsWhen colon cancer cells were cultured in 3-D with EGF, they grew as round spheroid colonies. However, colon cancer cells also grew as flat, disc-like colonies when cultured with EGF plus Wnt, R-Spondin1 and Noggin. Disc colonies were found to have comparable levels of E-cadherin as the spheroid colonies, but showed decreased E-cadherin at the cell-matrix contact sites. Disc colonies also elaborated F-actin rich protrusions (FRP) at the cell-matrix edge, reminiscent of an invasive phenotype but without the expression of vimentin. These E-cadherin and F-actin alterations were not induced by the four growth factors in 2-D culture. Formation of the disc colonies was inhibited by the knockdown of β-catenin and by protein kinase inhibitors such as gefitinib, imatinib and MK-2206. Furthermore, withdrawal of the crypt growth factors was able to revert the disc colonies to spheroid growth, showing that the invasive phenotype was reversible dependent on the availability of growth factors.ConclusionsThese findings show that colon cancer cells remain responsive to the growth factors in the crypt microenvironment and can be induced to undergo morphological transformation in the more physiologically relevant 3-D culture.

Intestinal crypts reproducibly expand in culture

BackgroundIn vitro growth techniques for intestinal crypts and single intestinal stem cells have been recently described, but several questions of translational importance remain unaddressed. The purpose of this study was to first, evaluate if intestinal crypts reproducibly expand in vitro; second, determine the impact of age and region of intestine on crypt growth in vitro; and third, determine the effects of cryopreservation on crypt growth in vitro. Methods and materialsCrypts were harvested from 5 cm of proximal, middle, and distal small intestine of C57BL/6J mice aged 4 wk, 6–8 wk, 12–14 wk, and 18–20 wk (n = 4–6 animals) and cultured. For each region, we determined the efficiency of crypts forming enterospheres (day 1) and progressing to enteroids (day 7). Subsequently, enteroids were passaged and cryopreserved to determine if growth was changed by these manipulations. ResultsForty-three to 99% of intestinal crypts formed enterospheres, with higher efficiency in proximal small intestine and in younger mice. Twenty-five to 64% of enterospheres progressed to budding enteroids within 7 d. In vitro expansion was greater in proximal enteroids. This expansion continued in a logarithmic fashion, with ∼97% replating efficiency of isolated enteroid crypt buds. Following cryopreservation, ∼90% of enteroids recovered normal proliferative capacity. ConclusionsIntestinal crypt culture is efficient and significantly expands intestinal tissue in a reproducible manner. Regional and age growth differences may reflect distinct stem cell characteristics or differences in support cells. The ability to culture and expand intestinal tissue in vitro provides a potential translational approach toward understanding and treating patients with short bowel syndrome.

Proximal versus distal hyperplastic polyps of the colorectum: different lesions or a biological spectrum?

Background: Because of their suggested link with microsatellite instability high colorectal cancers, right sided hyperplastic polyps (HPs) may differ from their distally located counterparts. This is highlighted by the recognition...

Ursodeoxycholic acid inhibits tumor development during both AOM-induced colon tumor initiation and progression

BACKGROUND: Studies in both sporadic human colon cancer, and in experimental models of this malignancy, indicate that bile acids, such as cholic acid, may promote colonic carcinogenesis. In contrast, we have previously shown that the bile acid, ursodeoxycholic acid (UDCA), when administered continuously during both tumor initiation and progression/promotion, inhibited the development of azoxymethane (AOM)-induced colon cancer in rats. More recently, we have found that UDCA also inhibited AOM-induced hyperprolifaration, as well as aberrant crypt formation and growth. In an extension of these studies we asked whether this chemopreventive effect of UDCA would occur if administered only during the initiation phase, or during the post-initiation (promotion/progression} phase. METHODS: Male Fisher 344 rats (180) were divided into six treatment groups: Groups1&2 received standard rat chow (AIN 76A) throughout the study. Groups 3&4 received UDCA supplementation (0.4% w/w) only during the first 5 weeks (initiation phase). Groups 5&6 received UDCA supplementation (0.4% w/ w) only after 5 weeks (promotion/progression phase). Two wks after starting the diets, groups 2, 4 & 6 (40 rats each) received azoxymethane 20 mg/kg body weight per wk x 2 wks, while groups 1, 3 and 5 (20 rats each) received saline (AOM-vehicle) as controls. Thirty-two wks later, rats were sacrificed and colons resected. VisibE tumors were harvested and fixed in 10% buffered formalin for histologic characterization. RESULTS: There were no significant differences in weight gain among the groups. In the carcinogen-treated dietary control group, tumor incidence was 72.3%; and tumor multiplicity was 1.9 tumors per tumor bearing rat (TBR). Compared with the AOM-treated unsupplemented group, UDCA, administered only during the initiation, or in the post initiation phase, each significantly decreased tumor incidence to 46.2% and 38.4% (p<O.05); and tumor multiplicity to 1.4 and 1.3 tumors per TBR, respectively (p<O.05). UDCA, in the promotion/progression phase, moreover, decreased both tumor size and the development of adenocarcinomas. CONCLUSIONS: UDCA significantly inhibited AOM-induced colonic carcinogenesis when administered during either tumor initiation, or tumor promotion/progression. Since these studies indicate UDCA inhibits tumor progression/promotion, this bile acid may be useful as a chemopreventive agent in humans at increased risk for colon cancer.

Clonality and Life Cycles of Intestinal Crypts Explained by a State Dependent Stochastic Model of Epithelial Stem Cell Organization

The organization and control of stem cells is a key issue in epithelial cell biology. The small intestinal murine crypt is a useful tissue to study such problems since stem cells are known to be located at specific positions at the bottom of the crypt where they are self maintaining.Recent data suggest, that (1) the number of active stem cells in a crypt can fluctuate, (2) the immediate progeny of a single stem cell can replace other stem cells eventually leading to monoclonality and (3) the life cycle of crypts may be linked to stem cell dynamics.It is the objective of this paper to suggest a stochastic state-dependent model of stem cell and crypt growth which can explain and link these phenomena into one comprehensive framework. Monte Carlo simulations are performed to show consistency with available data. The model explains the size distribution of small intestinal crypts in steady state, the observations of stem cell fluctuations and monoclonality conversion, recovery of the crypt population after moderate damage and the rate of crypt fission and extinction. The key assumption of this model is an autoregulatory control of stem cell growth.

Novel insights into human intestinal epithelial cell proliferation in health and disease using confocal microscopy.

Measurement of intestinal epithelial cell proliferation has provided important information concerning tissue responses in neoplasia, enteropathy, and adaptation. This study reexamined current concepts regarding intestinal proliferation by using a novel confocal microscopical technique to map mitotic figures accurately within the intact three dimensional framework of the crypts of Lieberkühn. The ability of confocal microscopy to simultaneously measure crypt morphology and internal detail, without disrupting spatial cell arrangements, has provided important new data. These question the ability of existing methods to accurately measure and interpret proliferative changes in the gut. This work investigates intestinal proliferation in children with coeliac disease, a well defined hyperproliferative disorder, in comparison with the healthy intestine. These results show that crypt cell division occurs with an equal probability in health and disease. In addition, increased crypt cell production rates are largely caused by a change in crypt size rather than a change in cell cycle time or crypt growth fraction and, as such, alter our understanding of kinetic responses in gastrointestinal disease.

Inhibition of aberrant crypt growth by non‐steroidal anti‐inflammatory agents and differentiation agents in the rat colon

Aberrant crypts are aggregates of single to multiple colonic crypts evidencing hallmarks of dysplasia and may be the earliest detectable pathological lesions for colon cancer. The aberrant crypt assay has been developed in 2 protocols. In one, putative chemoprevention agents are tested for inhibitory effects when administered concomitantly with a carcinogen. In the other, the objective of this study, aberrant crypts were induced in F344 rats by parenteral injection of the colon carcinogen azoxymethane (AOM) and allowed to develop for 4 weeks, when an average of 90-100 aberrant crypt foci per colon were found in the methylene blue-stained colon. Then, during the second 4 weeks of the experiment, aberrant crypts were allowed to further develop to a frequency of > 150 foci per colon, a time when multi-crypt foci were observed. During this time we tested the inhibitory effects of 4 analgesic drugs and 2 differentiation agents for effects of aberrant crypt growth and development. We found the non-steroidal anti-inflammatory drugs piroxicam, aspirin and ibuprofen, but not acetaminophen, to be effective in suppressing aberrant crypt formation or the progression to foci of multiple aberrant crypts. Treatment with chemosuppressing agents 13-cis-retinoic acid (13-cRA) and 4-hydroxyphenretinamide (4-HPR), known differentiating agents, however, did suppress expansion of aberrant crypt foci, with 13-cRA being the much more potent agent.

Analysis of crypt cell proliferation in coeliac disease using MI-B1 antibody shows an increase in growth fraction.

This study aimed to investigate the pattern of cellular proliferation and to calculate the growth fraction of small intestinal crypts in 24 patients--eight with untreated coeliac disease (CD), six with treated CD, and 10 controls with normal villous architecture. Duodenal biopsy specimens were stained with MI-B1 antibody using an immunoperoxidase method. Positive stained crypt cells were counted and their position within each intact crypt column was noted. These were used to construct proliferation index distribution curves for each cell position from which the crypt growth fraction for each group of patients was calculated. The crypt growth fraction was found to be higher in the untreated CD group (0.57) than in the treated patients (0.39) and the controls (0.44). The mean (SEM) proliferative index for each crypt was significantly higher in the untreated group (42.3 (10.8)%; p < 0.05) than in the treated CD (21.7 (8.5)%) and control (19.7 (7.5)%) groups and correlated closely with the surface:volume index and enterocyte cell height measurements in all three groups. An increased growth fraction may contribute to other changes in crypt cell kinetics to produce the histological changes seen in untreated CD.

Prolonged administration of IGF peptides enhances growth of gastrointestinal tissues in normal rats

To investigate the effect of insulin-like growth factor (IGF) peptide infusion on the gastrointestinal tract, female rats (115 g, 6/group) were treated for 14 days with IGF-I or long R (LR3IGF-I; 0, 44, 111, or 278 micrograms/day) delivered by osmotic minipumps. Both peptides induced a dose-dependent increase in gastrointestinal tissue weight. Total gut weight, small intestinal weight, and small intestinal length increased by 43, 47, and 13%, respectively, after treatment with 278 micrograms/day of LR3IGF-I. Crypt depth and villus height increased after peptide treatment with an associated increased crypt cell population (+33%), cells per villus column (+34%), and villus cell density (+20%). Proportional increments in proliferating cell nuclear antigen labeling and an unaltered crypt growth fraction indicated that the balance between the proliferative and maturation compartment of the crypt was maintained. Fecal nitrogen excretion was significantly reduced in rats treated with LR3IGF-I, suggesting an increased absorptive capacity of the duodenum. The enhanced potency of LR3IGF-I supports previous findings that the gut is especially responsive to analogues with reduced binding affinity to IGF-binding proteins.

Subcutaneous but not Intraluminal Epidermal Growth Factor Stimulates Colonic Growth in Normal Adult Rats

Epidermal growth factor (EGF) was administered by chronic subcutaneous or intracolonic infusion into normal adult rats to determine the effect on colonic growth. Subcutaneous infusion of 200 micrograms EGF/kg/day for 7 days increased the cross-sectional mass and protein content of the muscularis and mucosal layers of the proximal colon, with the distal colon showing less response. In the mucosa, subcutaneous EGF induced proportional increments in the number of cells per crypt, and in the number of cells positively labelled for PCNA, while maintaining a normal crypt growth fraction. In contrast, an 8-fold higher dose of EGF administered intraluminally had no effect on colonic mucosal or muscularis growth. This lack of bioactivity was unlikely to reflect rapid luminal degradation as radiolabelled EGF remained stable in the colonic lumen for at least 4 h. The results demonstrate that the normal adult colon is responsive to subcutaneously delivered EGF, particularly the proximal colon, whereas EGF may not be active on the normal colon when presented from the luminal direction.

Study of the proliferation in human gastric mucosa after in vivo bromodeoxyuridine labelling.

Studies to measure human gastric crypt or gland cell proliferation may have a number of practical clinical applications in relation to both benign and malignant gastric conditions. Bromodeoxyuridine (BrdUrd) labels human gastric mucosal cells in the S phase. Computer aided data analysis of labelled mucosa allows static proliferative indices to be estimated, including the crypt labelling index (LI), the peak labelling position, the distribution of labelled cells and indirectly the crypt growth fraction. Multiparameter flow cytometric analysis of labelled nuclei allows the S phase duration (Ts) of mucosal cells to be estimated. Specimens of histologically normal gastric body (GB, n = 16) and antral mucosa (GA, n = 10) were obtained from 25 patients with gastric carcinomas who received a bolus dose of 250 mg BrdUrd between 3.0 and 15.7 hours before surgery. Tissue sections were stained by an immunohistochemical method and subjected to detailed counting of up to 50 longitudinal crypts per specimen. The total crypt labelling index was calculated by a grid counting method. A significant difference existed between the proliferative compartments of gastric antral and body mucosa measured by a number of criteria. The median lengths of the crypts were 137 cells (GB) and 188 cells (GA). The median peak labelling positions were cell 26 (GB) and cell 61 (GA) from the crypt orifice. The mean crypt labelling indices were 2.8% (GB) and 4.8% (GA). The mean Ts of GA cells was 7.7 hours and of GB cells was 10.8 hours.

Patterns of growth and differentiation in the colon carcinoma cell line LIM 1863.

The LIM 1863 colon carcinoma cell line grows in the form of morphologically and functionally organized organoids. Cells are arranged around a central lumen with a brush border and nuclei are polarized to the periphery. The organoids contain 3 morphological cell types (columnar, goblet and caveolated cells). By agar cloning it has been possible to isolate 29 subclones of the cell line, all of which display the same phenotype and percentage of morphological cell types as the parent line. Cell-sorting experiments showed that precursor cells of LIM 1863 cultures could express either mucin (large-intestinal-mucus antigen) or a brush-border enzyme (sucrase-isomaltase). Proliferating cells were predominantly found near the outer periphery of organoids with cell maturation towards the internal lumen. Dead cells were continuously shed from the organoids but terminal non-cycling cells were not observed within the organoids. The organoid structure was calcium-dependent and promoted cell survival. Suspension cultures of disaggregated cells could be grown in medium containing less than 100 microM calcium. No decrease in differentiation antigens was observed in the low-calcium cultures, although polarization of the cells was lost. The organoid cultures formed by this cell line represent a unique in vitro model for colonic crypt growth and organization.

Acute and subacute effects of thiamine deficiency on the morphometry and cell kinetics of jejunal and ileal epithelial cells.

The effects of acute and subacute thiamine deficiency on jejunal and ileal epithelial cells were studied in rats, using crypt and villus cell population, crypt cell production per crypt (CCPC), crypt growth fraction (Ip) and crypt cell cycle time (Tc) as parameters. In acute thiamine deficiency there was marked jejunal hypoplasia of the crypt and villus, but in the ileum there was hypoplasia only of the crypt. The jejunal epithelium of the subacute thiamine deficiency (STD) group showed no morphometric changes. In contrast, in the ileal epithelium of STD rats there was decreased crypt depth and villus cell population. Thiamine deficiency had no significant effect on CCPC, Ip and Tc.

The crypt cycle. Crypt and villus production in the adult intestinal epithelium

We propose a model for the growth of individual crypts that is able to account for the observed changes in the number of cells in crypts under normal conditions, after irradiation, and after 30% resection. Parameter values for this model are estimated both for mouse and man, and detailed predictions of crypt growth rates are made. This model does not predict a steady-state crypt size; rather it suggests that crypts grow until they bifurcate. We therefore propose a crypt cycle (analogous to the cell cycle) and present evidence that most if not all crypts in the adult mouse are cycling asynchronously and independently. This evidence consists of four experiments that indicate that branching crypts are randomly distributed over the intestinal epithelium, that the plane of bifurcation of branching crypts is randomly oriented with respect to the villus base, and that the size distribution of crypts is consistent with an expanding crypt population. We also report for the first time evidence of villus production in the adult mouse intestinal epithelium. We conclude that the crypt and villus populations in the adult mouse are not in a steady state.