Identification of intestinal M cells in isolated lymphoid follicles and Peyer’s patches of the Angora rabbit

The presence, distribution, and localization of M cells in isolated lymphoid follicles (ILF) and in follicle-associated epithelia (FAE) covering Peyer’s patches (PP) in Angora rabbits were investigated by immunohistochemistry and electron microscopy. Although PP could macroscopically be identified along the length of the mucosal and serosal surfaces of jejunum and ileum, the presence of ILF could only be located microscopically. Typical M cells in FAE were detected within the periphery of the dome regions of the PP, and immature columnar M cells in the FAE resided in the vicinity of the crypts. M cells in the FAE of both ILF and PP showed vimentin-positive reaction. M cells in the FAE of ILF were morphologically similar to the immature M cells found in the FAE of PP. Typical mature M cells were also observed in the FAE of a few ILF. In contrast to FAE of PP, numerous goblet cells were observed in the FAE of many ILF. Moreover, among intestinal villi, we noticed villi-like solitary lymphoid structures that showed abundant lymphocytes in their lamina propria and that were surrounded with vimentin-positive cells and goblet cells. Thus, the occurrence of copious immature M cells and goblet cells, in addition to the detection of villi-like solitary lymphoid structures full of lymphocytes in the FAE of many ILF, indicate that ILF do not complete their immunological maturation in contrast to PP. Various antigenic stimulations conceivably induce the formation and maturation of ILF along the length of the small intestine. The morphological resemblance between ILF M cells and PP M cells suggests that these two types of cells perform similar or the same immunological functions.     

Optimality in the development of intestinal crypts

Intestinal crypts in mammals are comprised of long-lived stem cells and shorter-lived progenies. These two populations are maintained in specific proportions during adult life. Here, we investigate the design principles governing the dynamics of these proportions during crypt morphogenesis. Using optimal control theory, we show that a proliferation strategy known as a "bang-bang" control minimizes the time to obtain a mature crypt. This strategy consists of a surge of symmetric stem cell divisions, establishing the entire stem cell pool first, followed by a sharp transition to strictly asymmetric stem cell divisions, producing nonstem cells with a delay. We validate these predictions using lineage tracing and single-molecule fluorescence in?situ hybridization of intestinal crypts in infant mice, uncovering small crypts that are entirely composed of Lgr5-labeled stem cells, which become a minority as crypts continue to grow. Our approach can be used to uncover similar design principles in other developmental systems.     

Establishment of intestinal epithelial cell lines from adult mouse small and large intestinal crypts

Small and large intestinal epithelial cell (IEC) lines were established from adult murine intestinal crypts. Both established small and large IECs line (named aMoS7 and aMoC1 respectively) expressed epithelial markers. Similarly to IECs isolated from adult mouse intestines, the expression of major histocompatibility complex (MHC) class II molecules was induced by interferon-γ-treatment in both established cell lines. This expression of MHC class II molecules was higher in small intestinal aMoS7 cells than in large intestinal aMoC1 cells. Treatment with lipopolysaccharide and with ligands of Toll-like receptors 1, 2, 3, and 7 induced secretion of interleukin-6 from both adult IEC lines. These results suggest that the aMoS7 and aMoC1 cell lines can serve as useful tools in analyzing the immunological functions of IECs, especially in studying the IEC response to microbial components and its antigen presenting ability.     

Wnt signalling induces maturation of Paneth cells in intestinal crypts

Wnt signalling, which is transduced through beta-catenin/TCF4, maintains the undifferentiated state of intestinal crypt progenitor cells. Mutational activation of the pathway initiates the adenomacarcinoma sequence. Whereas all other differentiated epithelial cells migrate from the crypt onto the villus, Paneth cells home towards the source of Wnt signals--that is, the crypt bottom. Here, we show that expression of a Paneth gene programme is critically dependent on TCF4 in embryonic intestine. Moreover, conditional deletion of the Wnt receptor Frizzled-5 abrogates expression of these genes in Paneth cells in the adult intestine. Conversely, adenomas in Apc-mutant mice and colorectal cancers in humans inappropriately express these Paneth-cell genes. These observations imply that Wnt signals in the crypt can separately drive a stem-cell/progenitor gene programme and a Paneth-cell maturation programme. In intestinal cancer, both gene programmes are activated simultaneously.     

A stochastic branching model with formation of subunits applied to the growth of intestinal crypts

The intestinal epithelium is one of the most rapidly regenerating tissues in mammals. Cell production takes place in the intestinal crypts which contain about 250 cells. Only a minority of 1-60 proliferating cells are able to maintain a crypt over a long period of time. However, so far attempts to identify these stem cells were unsuccessful. Therefore, little is known about their cellular growth and selfmaintenance properties. On the other hand, the crypts appear to exhibit a life cycle which starts by fission of existing crypts and ends by fission or extinction. Data on these processes have recently become available. Here, we demonstrate how these data on the life cycle of the macroscopic crypt structure can be used to derive a quantitative model of the microscopic process of stem cell growth. The model assumptions are: (1) stem cells undergo a time independent supracritical Markovian branching process (Galton-Watson process); (2) a crypt divides if the number of stem cells exceeds a given threshold and the stem cells are distributed to both daughter crypts according to binomial statistics; (3) the size of the crypt is proportional to the stem cell number. This model combining two different stochastic branching processes describes a new class of processes whose stationary stability and asymptotic behavior are examined. This model should be applicable to various growth processes with formation of subunits (e.g. population growth with formation of colonies in biology, ecology and sociology). Comparison with crypt data shows that intestinal stem cells have a probability of over 0.8 of dividing asymmetrically and that the threshold number should be 8 or larger.     

Kinetic dimensions of cells and crypts in irradiated intestinal epithelium of mice]

The average value of axial cryptal section area and cell section area on it were studied during 8 days after total X-ray irradiation of male mice (400 rad). A small reducing of cryptal area (20%) during destructive period (1-2 days) is followed by a big overshoot (60%) during regenerative time (3-7 days). The cryptal sizes in regenerative period deviate from a steady state more than during destructive time. There are two high waves of abnormal growth of cell sizes above the steady level: the first one during destructive time and the second one during regeneration. This level seems to be near to minimal sizes of cryptal proliferative cells which are necessary for proliferation. It means that normal intestinal epithelium is a very economical and stabilized system. It is possible to evaluate quantitatively the associated with proliferation flow of substance per crypt cell for normal and irradiated intestine by means of index Iv where I is mitotical index and v - the cell volume. Cell hypertrophy at the time of regeneration on the 4th-7th days and later after irradiation (130-160%), was revealed. The crypt cell hypertrophy is the factor of destabilization of irradiated intestinal epithelium.     

The cell cycle time in intestinal crypts by simulation of FLM experiments

A computer program is developed that permits simulation of the dynamic behaviour of cells in intestinal crypts (Meinzer & Sandblad, 1985). Here we present the simulation of FLM data which is compared with the experimental findings of Al-Dewachi et al. (1974). The phase durations and total cycle times of cells in the jejunal crypts of rats were calculated. Additionally, the influence of various control parameters on the simulation output is discussed, e.g. the standard errors of phase times and the grain dilution at mitosis.     

Faunal structures associated with patches of mussels on East Asian coasts

Aggregations of mussels harbor a variety of associated animals and make it possible for diverse species to coexist at the shore. Species composition and diversity of the associated fauna are controlled by the position of mussel beds or patches, e.g. tidal level, age structure of mussels, quality of ambient water and by mussel species. When patches of mussels were surrounded by algal growth, a difference in the species composition of the associated fauna was recognized between the patches and algal mats. Mechanisms promoting coexistence are discussed. Biodeposit production by mussels may affect the environment both within the bed and the ambient waters. Reducing sediments showing low Eh values caused by the accumulation of biodeposits was observed in calm waters where the polychaete Capitella capitata, an indicator for organic enrichment, occurred both in the intertidal mussel bed and the subtidal sandy bottom communities. In a shallow subtidal sandy bottom of the Gulf of Thailand, where heavy bioturbation by the spatangoid urchin Brissus latecarinatus was occurring, small patches of the mussel Modiolus metcalfi increased species diversity and equitability in this habitat. Species composition was different between mussel patches and pure sandy bottoms. Electronic Publication     

Radioprotection of the intestinal crypts of mice by recombinant human interleukin-1 alpha

Recombinant human interleukin-1 alpha (rHIL-1 alpha or IL-1) protected the intestinal crypt cells of mice against X-ray-induced damage. The survival of crypt cells measured in terms of their ability to form colonies of regenerating duodenal epithelium in situ was increased when IL-1 was given either before or after irradiation. The maximum degree of radioprotection was seen when the drug was given between 13 and 25 h before irradiation. The IL-1 dose producing maximum protection was about 6.3 micrograms/kg. This is the first report indicating that the cytokine IL-1 has a radioprotective effect in the intestine. The finding suggests that IL-1 may be of potential value in preventing radiation injury to the gut in the clinic.     

c-Myc is required for the formation of intestinal crypts but dispensable for homeostasis of the adult intestinal epithelium

In self-renewing tissues such as the skin epidermis and the bone marrow, Myc proteins control differentiation of stem cells and proliferation of progenitor cell types. In the epithelium of the small intestine, we show that c-Myc and N-Myc are expressed in a differential manner. Whereas c-Myc is expressed in the proliferating transient-amplifying compartment of the crypts, N-Myc is restricted to the differentiated villus epithelium and a single cell located near the crypt base. c-Myc has been implicated as a critical target of the canonical Wnt pathway, which is essential for formation and maintenance of the intestinal mucosa. To genetically assess the role of c-Myc during development and homeostasis of the mammalian intestine we induced deletion of the c-myc(flox) allele in the villi and intestinal stem cell-bearing crypts of juvenile and adult mice, via tamoxifen-induced activation of the CreER(T2) recombinase, driven by the villin promoter. Absence of c-Myc activity in the juvenile mucosa at the onset of crypt morphogenesis leads to a failure to form normal numbers of crypts in the small intestine. However, all mice recover from this insult to form and maintain a normal epithelium in the absence of c-Myc activity and without apparent compensation by N-Myc or L-Myc. This study provides genetic and molecular evidence that proliferation and expansion of progenitors necessary to maintain the adult intestinal epithelium can unexpectedly occur in a Myc-independent manner.     

A review of spatial computational models for multi-cellular systems, with regard to intestinal crypts and colorectal cancer development

Colon rectal cancers (CRC) are the result of sequences of mutations which lead the intestinal tissue to develop in a carcinoma following a “progression” of observable phenotypes. The actual modeling and simulation of the key biological structures involved in this process is of interest to biologists and physicians and, at the same time, it poses significant challenges from the mathematics and computer science viewpoints. In this report we give an overview of some mathematical models for cell sorting (a basic phenomenon that underlies several dynamical processes in an organism), intestinal crypt dynamics and related problems and open questions. In particular, major attention is devoted to the survey of so-called in-lattice (or grid) models and off-lattice (off-grid) models. The current work is the groundwork for future research on semi-automated hypotheses formation and testing about the behavior of the various actors taking part in the adenoma–carcinoma progression, from regulatory processes to cell–cell signaling pathways.     

Evolutionary changes in color patches of blackbirds are associated with marsh nesting

Fully unraveling the mechanisms of sexual selection requiresan understanding of the variation in secondary sexual traitsacross species in a monophyletic assemblage and an understandingof the evolutionary relationships between those species. Therole of red and yellow male plumage coloration in territorydefense and sexual selection has been well studied in the red-winged blackbird (Agelaius phoeniceus), and males of many other close relatives of this species also have what appear to be carotenoid-pigmented patches in their plumage. We explored variation in male plumagecoloration across species of New World blackbirds (family Icteridae):traits known to be involved in sexual selection in this group.We document that blackbird lineages in which extant speciesbreed in marshes tend to have evolved from an all-black ancestralplumage to one exhibiting carotenoid plumage patches. The twomost likely hypotheses to explain this pattern are (1) increasedsexual selection intensity in marshes because of increasedvariance in territory quality and (2) increased frequency ofmale-male territorial interactions because of an increaseddensity of territories in marshes, but other hypotheses cannotbe ruled out. This pattern is consistent with either intersexualor intrasexual selection and warrants further investigation.     

Protein kinase D1 mediates stimulation of DNA synthesis and proliferation in intestinal epithelial IEC-18 cells and in mouse intestinal crypts

We examined whether protein kinase D1 (PKD1), the founding member of a new protein kinase family, plays a critical role in intestinal epithelial cell proliferation. Our results demonstrate that PKD1 activation is sustained, whereas that of PKD2 is transient in intestinal epithelial IEC-18 stimulated with the G(q)-coupled receptor agonists angiotensin II or vasopressin. PKD1 gene silencing utilizing small interfering RNAs dramatically reduced DNA synthesis and cell proliferation in IEC-18 cells stimulated with G(q)-coupled receptor agonists. To clarify the role of PKD1 in intestinal epithelial cell proliferation in vivo, we generated transgenic mice that express elevated PKD1 protein in the intestinal epithelium. Transgenic PKD1 exhibited constitutive catalytic activity and phosphorylation at the activation loop residues Ser(744) and Ser(748) and on the autophosphorylation site, Ser(916). To examine whether PKD1 expression stimulates intestinal cell proliferation, we determined the rate of crypt cell DNA synthesis by detection of 5-bromo-2-deoxyuridine incorporated into the nuclei of crypt cells of the ileum. Our results demonstrate a significant increase (p < 0.005) in DNA-synthesizing cells in the crypts of two independent lines of PKD1 transgenic mice as compared with non-transgenic littermates. Morphometric analysis showed a significant increase in the length and in the total number of cells per crypt in the transgenic PKD1 mice as compared with the non-transgenic littermates (p < 0.01). Thus, transgenic PKD1 signaling increases the number of cells per crypt by stimulating the rate of crypt cell proliferation. Collectively, our results indicate that PKD1 plays a role in promoting cell proliferation in intestinal epithelial cells both in vitro and in vivo.