Histomorphometric and developmental analysis of human fetal caecum and appendix with its embryological significance.

PURPOSE: The variable positions of the appendix can mislead surgeons and physicians to a wrong diagnosis. When appendicitis happens in subhepatic caecum, it can be misdiagnosed and can lead to severe complications during surgical procedures. Therefore, this study aimed to understand the histomorphometric development of the appendix and caecum and to identify when lymphoid follicles appear in the appendix during fetal life. METHODS: The study was conducted on a total of 50 fetuses. The caecum and appendix were carefully dissected. Their position and various measurements were observed. Afterwards, the appendix was taken out for histological processing. All three layers, mucosa, submucosa, and muscularis externa were measured using Image Analyzer Software Image Pro Premiere 9.1, and the appearance of lymphoid follicles was also examined. Results were analyzed using SPSS statistical software. RESULTS: During the 1st, 2nd, and 3rd trimesters the most common caecum type was type 1: as a lengthy tube, type 3: The lateral wall expanded more, thus it has an asymmetric saccule, and type 4: adult-like caecum. The caecum was mostly situated in the right lumbar region in the 2nd and 3rd trimesters. In the 1st trimester, it was subhepatic in position. The most common position of the appendix was 11 o'clock in 1st and 3rd trimesters. 2nd trimester's most common position of the appendix was 12 o'clock. The thickness of the mucosa, submucosa, and the muscularis externa increases as the trimester increases. The lymphoid follicles have appeared during the 2nd trimester. CONCLUSION: The knowledge from this study will be useful in the diagnosis and treatment of malformations, pathology, and anomalies of the caecum and appendix due to congenital causes.

Morphological Characteristics of the Developing Cecum of Japanese Quail (Coturnix coturnix japonica).

The current investigation was carried out to record the final stages of the development of both middle and distal parts of quail ceca, Coturnix coturnix japonica to understand the role of ceca in digestion, immune system, and absorption. The cellular and subcellular structures, including epithelial cell height, microvillus surface area, the proportion of goblet cells, the thickness of muscle layer, and cecum diameter showed great variations during the development. An undeveloped smooth muscularis mucosa was observed for the first time on the ED5. Primordia of glands were observed on the ED7. On the ED15, the middle part exhibited two shapes of mucosal villi: tongue-shaped villi and U-shaped. The plicae and crypts of Lieberkühn were demonstrated on the hatching day. The lymphatic tissues appeared in the wall of both parts of the ceca at the 4 weeks of age. Scanning electron microscopy revealed a great difference in the mucosal surface between different regions. Telocytes were observed in-between the muscle fibers and formed a network during the post-hatching period. Because of fermentation and other bacterial or chemical processes that have been shown to occur in the ceca, this study supports two hypotheses: the cecal development is related to diet and the cecal epithelium act as a site for primary absorption of nutrients or for re-absorption of electrolytes or amino acids derived from the urine.

Developmental morpho-analysis of the caecum in Japanese quail embryos (Coturnix coturnix japonica).

In the current study, we are focusing on the microanatomical structure of quail caecum during the prehatching time to try to understand the function and the role of each cell-built quail caecum reaching how caecum plays an essential role in immunity and absorption. The morpho-developmental features of the quail caecum were described in detail daily from the third incubation day (ID) till hatching time, investigating the gross morphology, microscopic, and ultrastructure using light and scanning electron microscope. The embryonic caecum appeared grossly as two lateral outpocketings with blinded ends, emerging laterally at the junction between the small and large intestine (the ileocaecal junction). The primordia of two caeca, represented by two lateral swellings from the hindgut on the fourth ID, continued growing till the day of hatching, where the caecal wall consisted of three apparent layers: mucosa, musculosa, and serosa. At the time of hatching, the quail caecum was still not fully mature and will continue growing posthatching. The findings in this study can be applied in further studies intended to understand the physiological mechanisms of the caecum during prehatching and posthatching periods. RESEARCH HIGHLIGHTS: Caecum is one of the hindgut derivatives that started as two lateral swellings. The caecal wall consisted of three layers; mucosa, musculosa, and serosa. The caecum plays an essential role in immunity maintenance. Caecum continues to grow posthatching as it is not fully mature at hatching time.

FGF9-Pitx2-FGF10 signaling controls cecal formation in mice.

Fibroblast growth factor (FGF) signaling to the epithelium and mesenchyme mediated by FGF10 and FGF9, respectively, controls cecal formation during embryonic development. In particular, mesenchymal FGF10 signals to the epithelium via FGFR2b to induce epithelial cecal progenitor cell proliferation. Yet the precise upstream mechanisms controlling mesenchymal FGF10 signaling are unknown. Complete deletion of Fgf9 as well as of Pitx2, a gene encoding a homeobox transcription factor, both lead to cecal agenesis. Herein, we used mouse genetic approaches to determine the precise contribution of the epithelium and/or mesenchyme tissue compartments in this process. Using tissue compartment specific Fgf9 versus Pitx2 loss of function approaches in the gut epithelium and/or mesenchyme, we determined that FGF9 signals to the mesenchyme via Pitx2 to induce mesenchymal Fgf10 expression, which in turn leads to epithelial cecal bud formation.

Beta1 integrins are required for the invasion of the caecum and proximal hindgut by enteric neural crest cells.

Integrins are the major adhesive receptors for extracellular matrix and have various roles in development. To determine their role in cell migration, the gene encoding the beta1 integrin subunit (Itgb1) was conditionally deleted in mouse neural crest cells just after their emigration from the neural tube. We previously identified a major defect in gut colonisation by conditional Itgb1-null enteric neural crest cells (ENCCs) resulting from their impaired migratory abilities and enhanced aggregation properties. Here, we show that the migration defect occurs primarily during the invasion of the caecum, when Itgb1-null ENCCs stop their normal progression before invading the caecum and proximal hindgut by becoming abnormally aggregated. We found that the caecum and proximal hindgut express high levels of fibronectin and tenascin-C, two well-known ligands of integrins. In vitro, tenascin-C and fibronectin have opposite effects on ENCCs, with tenascin-C decreasing migration and adhesion and fibronectin strongly promoting them. Itgb1-null ENCCs exhibited an enhanced response to the inhibitory effect of tenascin-C, whereas they were insensitive to the stimulatory effect of fibronectin. These findings suggest that beta1 integrins are required to overcome the tenascin-C-mediated inhibition of migration within the caecum and proximal hindgut and to enhance fibronectin-dependent migration in these regions.

Pitx2 is a critical early regulatory gene in normal cecal development.

BACKGROUND: The murine cecum is a critical digestive structure. Morphogenesis of the cecum involves several key genes, including Homeobox (Hox) d12. Ectopic expression of Hoxd12 has been shown to result in cecal agenesis and a down-regulation of both Fibroblast growth factor 10 (Fgf10) and the Pituitary homeobox 2 gene (Pitx2). Homozygous null mutation of Fgf10 or its cognate receptor Fgfr2IIIb results in severe cecal defects where there is the initiation of mesodermal budding, but a failure of the endoderm to grow and extend into this structure. We examined the expression of Pitx2 in the cecum and hypothesized that homozygous null mutation of Pitx2 would result in cecal agenesis. METHODS: IACUC approval was obtained for these studies. Whole mount in situ hybridizations for Pitx2 were performed on wild-type embryos between embryonic d (E)11.0 and E12.5. Pitx2 -/- and Fgfr2IIIb -/- embryos were generated from n/+ heterozygote breedings and harvested at E10.5, E11.5, and E13.5. Genotypes were confirmed by PCR. Morphology of Pitx2 -/- cecae were compared with those of wild-type littermates and Fgfr2IIIb -/- embryos at identical stages. Embryos were fixed overnight and photographed the following day. RESULTS: Pitx2 is expressed in the cecal mesoderm and endoderm as early as E11.0. Expression becomes increasingly more robust by E12.5. Homozygous null mutation of Pitx2 results in agenesis of the cecum. In contrast to Fgfr2IIIb -/- embryos, which demonstrate a persistent mesodermal bud as late as E18.5, no mesodermal bud is present in Pitx2 -/- embryos. CONCLUSIONS: Our findings demonstrate that Pitx2 is a critical regulatory gene in cecal morphogenesis and suggest that Pitx2 is required for initiation of mesodermal budding and likely resides upstream of Fgf10-Fgfr2IIIb signaling in the normal development of this structure.

Multiple regulatory regions control the complex expression pattern of the mouse Cdx2 homeobox gene.

BACKGROUND & AIMS: The Cdx2 homeobox gene exerts multiple functions including trophectoderm specification, antero-posterior patterning, and determination of intestinal identity. The aim of this study was to map genomic regions that regulate the transcription of Cdx2, with a particular interest in the gut. METHODS: Genomic fragments covering 13 kilobase (kb) of the mouse Cdx2 locus were analyzed in transgenic mice and in cell assays. RESULTS: No fragment was active in the trophectoderm. Fragments containing the first intron and extending up to -5-kb upstream of the transcription start site became active posteriorly at gastrulation and then inactive at midgestation in every tissue including the endoderm. Specific persistence of activity in the intestinal endoderm/epithelium beyond midgestation requires extending the genomic fragment up to -9 kb. We identified a 250-base pair segment around -8.5-kb binding and responding to endodermal factors, with a stimulatory effect exerted synergistically by HNF4alpha, GATA6, Tcf4, and beta-catenin. These factors were able to activate endogenous expression of Cdx2 in nonintestinal Hela cells. CONCLUSIONS: Multiple regulatory regions control the complex developmental pattern of Cdx2, including far upstream sequences required for the persistence of gene expression specifically in the gut epithelium throughout life. Cooperation between HNF4alpha, GATA6, beta-catenin, and Tcf4 contributes to the intestine-specific expression of Cdx2.

Abundance and Significance of Neuroligin-1 and Neurexin II in the Enteric Nervous System of Embryonic Rats.

Aim. To investigate the abundance of neuroligin-1 and neurexin II in the enteric nervous system (ENS) of rats on different embryonic days and to explore their potential significance. Methods. The full-thickness colon specimens proximal to the ileocecal junction of rats on embryonic days 16, 18, and 20 and of newborns within 24 hours (E16, E18, E20, and Ep0) were studied, respectively. qRT-PCR was applied for detecting the expressions of neuroligin-1 and neurexin II on mRNA, and western blotting was employed for detecting their further expressions on the whole tissue. Finally, the histological appearance of neuroligin-1 and neurexin IIα was elucidated using immunohistochemical staining. Results. qRT-PCR showed that the neuroligin-1 and neurexin II mRNA expressions of groups E16, E18, E20, and Ep0 increased gradually with the growth of embryonic rats (P < 0.05). Western blotting confirmed the increasing tendency. In immunohistochemical staining, proteins neuroligin-1 and neurexin IIα positive cells concentrated mostly in the myenteric nerve plexus of the colon and their expressions depend on the embryonic time. Conclusion. Neuroligin-1 and neurexin II were both expressed in the ENS and have temporal correlation with the development of ENS, during which neuronal intestinal malformations (NIM) may occur due to their disruptions and consequent abnormal ENS development.

Incomplete rotation of the intestine with a normal cecal position.

Nineteen patients with incomplete rotation of the intestine, seen during a 3-year period, are presented. Six patients (32%) had a normal cecal position but an abnormal duodenojejunal junction. Three of these patients had a midgut volvulus, and one had obstructing duodenal bands. The two remaining patients were premature and had postnatal fixation of the duodenojejunal junction over a 10-month to 2-year period.

Appendix and cecum. Embryology, anatomy, and surgical applications.

Surgeons should be familiar with surgery of the cecum and appendix because the diseases of this region, especially appendicitis, are the most common indications for surgical exploration. Usually, diagnosis of appendicitis and appendectomy are not difficult, but atypical location of the appendix or other anatomic anomalies can make the diagnosis of appendicitis and appendectomy difficult. In cases of atypical anatomy or diffuse clinical picture, especially in young adults or elderly patients, the spectrum of embryologic and anatomic anomalies must be kept in mind to make the correct treatment decision for individual patients. If doubt persists, explorative laparotomy must be performed to avoid overlooking rare, acute, intra-abdominal abnormalities.

An ultrastructural study on the "meconium corpuscles" in rat foetal intestinal epithelium with particular reference to apoptosis.

During the embryonic development of the intestine, programmed deletion of epithelial cells plays a vital role in the formation of secondary lumina and of villi. Electron microscopy shows that this deletion is effected by apoptosis, a distinctive mode of cellular death recently recognised as being implicated in normal tissue involution in the adult, as well as during intrauterine development. The process involves cellular condensation and budding to form membrane-bounded apoptotic bodies containing well-preserved organelles. These are then either engulfed by neighbouring principal cells or sloughed off into the intestinal lumen. Engulfed apoptotic bodies that show various degrees of lysosomal degradation have previously been referred to as "meconium corpuscles".

The misplaced caecum and the root of the mesentery.

Five cases presenting in late infancy and childhood with symptoms and signs referable to malrotation of the midgut are described. The condition may present with jaundice, malabsorption or the signs and symptoms of intestinal obstruction due to internal hernia or volvulus. It may also result in volvulus and gangrene of the midgut. A short root of the mesentery predisposing to this event will be seen on a barium meal and follow through examination and will warn of its impending occurrence.

The development of large intestine during the fetal period.

OBJECTIVE: The aim of this study is to determine the colon types, developmental change of the colon morphology during the fetal period. METHODS: The study was realised on 131 human fetuses (male 69, female 62) ages between 10 and 40 weeks, which have no external pathology and anomalies. The colon types were evaluated in two parts. As the first part, the colon part between the ileal orifice and sigmoid colon was typed. The sigmoid colon was typed as the second part. The macroscopic diameters of parts of the colon and the thicknesses of wall layers of ascending and descending colons were measured under the light microscope. RESULTS: For the proximal part of the colon, there were seven types of colon, and there were five types for the sigmoid colon. For the first part, transverse type colon was a rare type during the fetal period (3%). The oblique type colon was observed mostly in the first and second trimester during the fetal period. Adult type colon was the most common type in the third trimester and full-term groups. The pendulous type colon was observed mostly in the third trimester. The development of the haustra and tenia coli in the first trimester was quite slow, but later the development increased more and more, and during the full-term period, the haustra and tenia coli could be seen clearly. CONCLUSION: The percentage distribution of the colon types between the trimesters was significant. It was observed that the maturation of haustra and tenia coli started from the ascending colon and progressed towards the sigmoid colon. The thickness of the tunica mucosa layer both in the ascending and in descending colon part increased considerably in the middle of the second trimester.

The histological observations on the large intestine of the goose (Anser anser) during the pre- and post-hatching periods.

The development of the cecum and colon in the goose was investigated during the period from the 15th to 28th day of the incubation and from 1 to 30 days of age after hatching by light microscopy. By day 15 of the incubation, in the cecum and colon, the lumen was surrounded by pseudostratified epithelium. The previllous ridges appeared at 15th and 17th days of the incubation in the colon and ceca, respectively. At the base of previllous ridges, the epithelium changed into a simple prismathic epithelium at 15th and 17th days of the incubation in the colon and cecum, respectively. The villi appeared at the 21st days of the incubation. The crypts and goblet cells appeared on the first day after hatching. In the pre-hatching period, the lamina muscularis mucosa was present only in the colon. The submucosa consisted of loosely aggregated connective tissue in the pre-hatching period. In the post-hatching period, it consisted of a very thin layer of connective tissue. Its presence was only obvious where the cells of the submucosal nerve plexus or occasional large blood vessels considerably increased its thickness. The nerve plexus corresponding to the Auerbach's plexus of the mammalian intestine and submucosal nerve plexus appeared by 15th days of the incubation. From the 15th to 28th day of incubation, the tunica muscularis consisted of circular smooth muscle cells in the ceca. On the 28th day of the incubation a thinner longitudinal muscle layer added to the circular muscle layer. In the colon there was an outer longitudinal and a thicker circular muscle layer.

Development of Peyer's patch and cecal tonsil in gut-associated lymphoid tissues in the chicken embryo.

It is well known that chicken B cells develop in the bursa of Fabricius (BF), which is categorized as gut-associated lymphoid tissue (GALT). Chicken GALT also includes Peyer's patch (PP) and cecal tonsil (CT). The relationship between these tissues in GALT during B cell development is currently unknown. In this study, we conducted comparative examination of PP, CT and BF development during embryogenesis using immunohistochemical staining. On day 13 of embryogenesis (E13), accumulation of MHC class II(+) cells was observed in the intestine. Thereafter, Bu-1(+) cells and IgM(+) cells appeared, and their number continuously increased at the same sites where MHC class II(+) cells were present. Similar results were obtained in the CT. The locations of embryonic PP were limited to two sites; near the Meckel's diverticulum and the ileocecal junction. Anlage of bursal follicles first appeared at E13 and developed thereafter. Immigration of Bu-1(+) cells to bursal follicles began at E13, and the number of Bu-1(+) cell subsequently increased. When the follicle of BF was eliminated from the embryo by treatment with testosterone, development of PP and CT were observed. We concluded therefore that the development of PP and CT start during late embryogenesis at the same time as the follicle of BF, and that appearance of surface IgM(+) cells in PP and CT is independent form the development of the follicle of BF.

Scanning electron microscopic observations of the development of the chicken caecum.

The surface pattern of the caeca of the chicken was examined using the scanning electron microscope (SEM) in stages ranging from 11th day of foetal development to 60 days of post-natal life. During incubation the proximal region (basis) of the caecum presented a few irregular elevations, which were later regarded as villi and after hatching, gradually, became longer and wider. These structures were found to be similar to those of the small intestine. The middle (corpus) and distal (apex) regions of caecum presented ridges/folds with short and blunt villi that were even shorter in the apex. The ridges/folds were running longitudinally the inner surface of the corpus while those of the apex were not so well developed.

Scanning electron microscopy of large intestine (caecum and colon) of rabbit during foetal and post-natal life.

The surface pattern of the large intestine mucosa (caecum and colon) of the rabbit was examined using scanning electron microscope (SEM), in stages ranging from 26 days of foetal to 24 days of post-natal life. It was composed of villi in the foetus and in 1-day-old rabbit. By the 16th day of life these villi were replaced by ridges.

[Glycoconjugates of the cecal intestinal epithelium of the chick before and after hatching: histochemical study performed with peroxidase-conjugated lectins]. / I glicoconiugati nell'epitelio dell'intestino cieco del pollo prima e dopo la schiusa: studio istochimico eseguito con lectine coniugate a perossidasi.

A battery of seven different horseradish peroxidase-labelled lectins (PNA, ConA, DBA, SBA, LTA, WGA and UEA I) was used to study the distribution and changes of carbohydrate moieties of glycoconjugates in the caecal epithelium (proximal and distal tracts) of the chick embryo and of the 3 days old chicken. The chief results showed that: 1. The appearance of some sugar residues was earlier observed at the epithelium of the distal tract than the proximal one (Tab. 2). 2. The presence of sialic acid was detected only after hatching (Fig. 4, Tab. 2). 3. During the embryonic caecal development enterocytes and goblet cells were characterized by the presence of the same sugar residues (Tab. 2). 4. By a quantitative point of view, differences in sugar residues content between the epithelium of the proximal and distal tract were observed. The epithelial cells of the distal tract were generally characterized by an higher content of saccharide moieties (Tab. 2). 5. At the end of the incubation period and after hatching enterocytes and goblet cells showed differences in content of some sugar residues (Fig. 1-3, Fig. 5-8, Tab. 2).

Long noncoding RNAs in development: solidifying the Lncs to Hox gene regulation.

Long noncoding RNAs (lncRNAs) are pervasively expressed in mammals, although their functions during development remain poorly understood. In this issue of Cell Reports, Delpretti et al. and Li et al. suggest essential roles for lncRNAs in coordinating Hox gene expression.

Multiple enhancers regulate Hoxd genes and the Hotdog LncRNA during cecum budding.

Hox genes are required for the development of the intestinal cecum, a major organ of plant-eating species. We have analyzed the transcriptional regulation of Hoxd genes in cecal buds and show that they are controlled by a series of enhancers located in a gene desert flanking the HoxD cluster. The start site of two opposite long noncoding RNAs (lncRNAs), Hotdog and Twin of Hotdog, selectively contacts the expressed Hoxd genes in the framework of a topological domain, coinciding with robust transcription of these genes during cecum budding. Both lncRNAs are specifically transcribed in the cecum, albeit bearing no detectable function in trans. Hedgehogs have kept this regulatory potential despite the absence of the cecum, suggesting that these mechanisms are used in other developmental situations. In this context, we discuss the implementation of a common "budding toolkit" between the cecum and the limbs.