The microvascular structure of the normal colon in rats and humans

Roles of endothelial prostaglandin I2 in maintaining synchronous spontaneous Ca2+ transients in rectal capillary pericytes

In hollow visceral organs, capillary pericytes appear to drive spontaneous Ca2+ transients in the upstream arterioles. Here, mechanisms underlying the intercellular synchrony of pericyte Ca2+ transients were explored. Ca2+ dynamics in NG2 chondroitin sulphate proteoglycan (NG2)-expressing capillary pericytes were examined using rectal mucosa-submucosa preparations of NG2-GCaMP6 mice. Spontaneous Ca2+ transients arising from endoplasmic reticulum Ca2+ release were synchronously developed amongst capillary pericytes in a gap junction blocker (3 μM carbenoxolone)-sensitive manner and could spread into upstream vascular segments. Spontaneous Ca2+ transients were suppressed by the Ca2+ -activated Cl- channel (CaCC) blocker niflumic acid and their synchrony was diminished by a TMEM16A inhibitor (3 μM Ani9) in accordance with TMEM16A immunoreactivity in pericytes. In capillaries where cyclooxygenase (COX)-2 immunoreactivity was expressed in endothelium but not pericytes, non-selective COX inhibitors (1 μM indomethacin or 10 μM diclofenac) or COX-2 inhibitor (10 μM NS 398) disrupted the synchrony of spontaneous Ca2+ transients and raised the basal Ca2+ level. Subsequent prostaglandin I2 (PGI2 ; 100 nM) or the KATP channel opener levcromakalim restored the synchrony with a reduction in the Ca2+ level. PGI2 receptor antagonist (1 μM RO1138452) also disrupted the synchrony of spontaneous Ca2+ transients and increased the basal Ca2+ level. Subsequent levcromakalim restored the synchrony and reversed the Ca2+ rise. Thus, the synchrony of spontaneous Ca2+ transients in pericytes appears to be developed by the spread of spontaneous transient depolarisations arising from the opening of TMEM16A CaCCs. Endothelial PGI2 may play a role in maintaining the synchrony, presumably by stabilising the resting membrane potential in pericytes. KEY POINTS: Capillary pericytes in the rectal mucosa generate synchronous spontaneous Ca2+ transients that could spread into the upstream vascular segment. Spontaneous Ca2+ release from the endoplasmic reticulum (ER) triggers the opening of Ca2+ -activated Cl- channel TMEM16A and resultant depolarisations that spread amongst pericytes via gap junctions, establishing the synchrony of spontaneous Ca2+ transients in pericytes. Prostaglandin I2 (PGI2 ), which is constitutively produced by the endothelium depending on cyclooxygenase-2, appears to prevent premature ER Ca2+ releases in the pericytes allowing periodic, regenerative Ca2+ releases. Endothelial PGI2 may maintain the synchrony of pericyte activity by stabilising pericyte resting membrane potential by opening of KATP channels.

Vasculature in the mouse colon and spatial relationships with the enteric nervous system, glia, and immune cells

The distribution, morphology, and innervation of vasculature in different mouse colonic segments and layers, as well as spatial relationships of the vasculature with the enteric plexuses, glia, and macrophages are far from being complete. The vessels in the adult mouse colon were stained by the cardiovascular perfusion of wheat germ agglutinin (WGA)-Alexa Fluor 448 and by CD31 immunoreactivity. Nerve fibers, enteric glia, and macrophages were immunostained in the WGA-perfused colon. The blood vessels entered from the mesentery to the submucosa and branched into the capillary networks in the mucosa and muscularis externa. The capillary net formed anastomosed rings at the orifices of mucosa crypts, and the capillary rings surrounded the crypts individually in the proximal colon and more than two crypts in the distal colon. Microvessels in the muscularis externa with myenteric plexus were less dense than in the mucosa and formed loops. In the circular smooth muscle layer, microvessels were distributed in the proximal, but not the distal colon. Capillaries did not enter the enteric ganglia. There were no significant differences in microvascular volume per tissue volume between the proximal and distal colon either in the mucosa or muscularis externa containing the myenteric plexus. PGP9.5-, tyrosine hydroxylase-, and calcitonin gene-related peptide (CGRP)-immunoreactive nerve fibers were distributed along the vessels in the submucosa. In the mucosa, PGP9.5-, CGRP-, and vasoactive intestinal peptide (VIP)-immunoreactive nerves terminated close to the capillary rings, while cells and processes labeled by S100B and glial fibrillary acidic protein were distributed mainly in the lamina propria and lower portion of the mucosa. Dense Iba1 immunoreactive macrophages were closely adjacent to the mucosal capillary rings. There were a few macrophages, but no glia in apposition to microvessels in the submucosa and muscularis externa. In conclusion, in the mouse colon, (1) the differences in vasculature between the proximal and distal colon were associated with the morphology, but not the microvascular amount per tissue volume in the mucosa and muscle layers; (2) the colonic mucosa contained significantly more microvessels than the muscularis externa; and (3) there were more CGRP and VIP nerve fibers found close to microvessels in the mucosa and submucosa than in the muscle layers.

Association of preserved vegetable consumption and prevalence of colorectal polyps: results from the Lanxi Pre-colorectal Cancer Cohort (LP3C)

PURPOSE

Although fresh vegetable consumption has been linked with a lower risk of colorectal polyps, a precursor lesion for colorectal cancer (CRC), the association between preserved vegetable consumption and colorectal polyps is unknown. We aimed to assess the association of preserved vegetable intake with the prevalence of colorectal polyps with the consideration of subsites, sizes and multiplicity of polyps.

METHODS

We analyzed the cross-sectional data from 40-80 years Chinese at a high risk of CRC from the Lanxi Pre-colorectal Cancer Cohort (LP3C) baseline survey, which was conducted between March 2018 and December 2019. Dietary information was obtained via a validated food frequency questionnaire. Multivariate logistic regression was employed to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) of preserved vegetable consumption and the prevalence of colorectal polyps.

RESULTS

Of 6783 eligible participants in 2018-2019 survey of LP3C, 2064 prevalent colorectal polyp cases were identified. In the multivariable-adjusted model, preserved vegetable consumption was positively associated with the prevalence of colorectal polyps (OR for fourth vs. first quartile: 1.18; 95% CI 1.01-1.36; P trend = 0.02). The similar association was also detected for small polyps [OR_{Q4 vs Q1} (95% CI): 1.17 (1.00-1.37); P trend = 0.03]. The similar trend was detected for multiple polyps [OR _{Q4 vs Q1} (95% CI):1.27 (0.98-1.64); P trend = 0.04], proximal colon polyps [OR_{Q4 vs Q1} (95% CI): 1.12 (0.90-1.38); P trend = 0.07], and single polyp [OR_{Q4 vs Q1} (95% CI) for 1.15 (0.98-1.35); P trend = 0.06]. No significant association was observed for distal colon [OR_{Q4 vs Q1} (95% CI) 1.19 (0.98-1.45); P trend = 0.09]. Replacing one serving per day of preserved vegetables with fresh vegetables was related to 20%, 23%, and 37% lower prevalence of overall, small, and multiple polyps, respectively.

CONCLUSIONS

Preserved vegetable consumption was associated with a higher prevalence of colorectal polyps in a Chinese population at a high risk of CRC. Replacing preserved vegetables with fresh vegetables may be conducive to lower prevalent colorectal polyps.

Temperature estimation of inflamed bowel by the photoacoustic inverse approach

Local temperature increase is one of the five classical signs of regions with inflammations. This work is focused on the application of the photoacoustic technique for the estimation of the temperature field in the colon, as the solution of an inverse problem, for the detection of inflamed regions. Two-dimensional cases are examined here involving a cross section of the bowel, which characterize either the inflammation of the whole mucosa layer, or three small inflamed regions. The inverse problem is solved for a rotating laser inside the intestine lumen, which imposes pulses for the generation of the acoustic waves. One single ultrasound detector, also located at the laser rotating shaft, provides the simulated measurements for the inverse analysis. The inverse problem is solved here with the minimization of the maximum a posteriori objective function. Results show that the proposed technique can be applied for accurate estimations of the temperature distribution in the region of interest, which might be used for the diagnosis of inflammatory bowel diseases (IBD).

An on-chip model of protein paracellular and transcellular permeability in the microcirculation

Recent therapeutic success of large-molecule biologics has led to intense interest in assays to measure with precision their transport across the vascular endothelium and into the target tissue. Most current in vitro endothelial models show unrealistically large permeability coefficients due to a non-physiological paracellular transport. Thus, more advanced systems are required to better recapitulate and discern the important contribution of transcellular transport (transcytosis), particularly of pharmaceutically-relevant proteins. Here, a robust platform technology for the measurement of transport through a human endothelium is presented, which utilizes in vitro microvascular networks (MVNs). The self-assembled MVNs recapitulate the morphology and junctional complexity of in vivo capillaries, and express key endothelial vesicular transport proteins. This results in measured permeabilities to large molecules comparable to those observed in vivo, which are orders of magnitude lower than those measured in transwells. The permeability of albumin and immunoglobulin G (IgG), biopharmaceutically-relevant proteins, is shown to occur primarily via transcytosis, with passage of IgG regulated by the receptor FcRn. The physiological relevance of the MVNs make it a valuable tool to assess the distribution of biopharmaceuticals into tissues, and may be used to prioritize candidate molecules from this increasingly important class of therapeutics.

In vivo performance of a visible wavelength optical sensor for monitoring intestinal perfusion and oxygenation

Traumatic injury resulting in hemorrhage is a prevalent cause of death worldwide. The current standard of care for trauma patients is to restore hemostasis by controlling bleeding and administering intravenous volume resuscitation. Adequate resuscitation to restore tissue blood flow and oxygenation is critical within the first hours following admission to assess severity and avoid complications. However, current clinical methods for guiding resuscitation are not sensitive or specific enough to adequately understand the patient condition. To better address the shortcomings of the current methods, an approach to monitor intestinal perfusion and oxygenation using a multiwavelength (470, 560, and 630 nm) optical sensor has been developed based on photoplethysmography and reflectance spectroscopy. Specifically, two sensors were developed using three wavelengths to measure relative changes in the small intestine. Using vessel occlusion, systemic changes in oxygenation input, and induction of hemorrhagic shock, the capabilities and sensitivity of the sensor were explored in vivo. Pulsatile and nonpulsatile components of the red, blue, and green wavelength signals were analyzed for all three protocols (occlusion, systemic oxygenation changes, and shock) and were shown to differentiate perfusion and oxygenation changes in the jejunum. The blue and green signals produced better correlation to perfusion changes during occlusion and shock, while the red and blue signals, using a new correlation algorithm, produced better data for assessing changes in oxygenation induced both systemically and locally during shock. The conventional modulation ratio method was found to be an ineffective measure of oxygenation in the intestine due to noise and an algorithm was developed based on the Pearson correlation coefficient. The method utilized the difference in phase between two different wavelength signals to assess oxygen content. A combination of measures from the three wavelengths provided verification of oxygenation and perfusion states, and showed promise for the development of a clinical monitor.

Comparison of survival between right-sided and left-sided colon cancer in different situations

Mountain of studies has showed that right‐sided colon cancer (RSCC) and left‐sided colon cancer (LSCC) have different clinical presentation and biologic features and should be considered as two distinct disease entities. The survival difference between RSCC and LSCC remains controversial. Using Surveillance, Epidemiology, and End Results (SEER) database, we identified colon adenocarcinoma patients from 2004 to 2013. The 5‐year cause‐specific survival (CSS) was our primary endpoint. All statistical analyses were performed using the Intercooled Stata 13.0. All statistical tests were two‐sided. The study included 95,847 (58.72%) RSCC and 67,385 (41.28%) LSCC patients. RSCC patients were older, more often females, more Caucasian, more unmarried, more advanced T and N stage, larger tumor sizes, and more poorly differentiated tumor, while LSCC patients had more stage IV diseases. Location was an independent prognostic factor in the multivariable analysis. Compared with RSCC patients, the hazard ratio for LSCC was 0.87, 95% CI: 0.85–0.89 P < 0.001. There was no survival difference between RSCC and LSCC in the following situations: older than 68 years old, T3–4, N0, poorly differentiated, and undifferentiated diseases. We firstly reported that RSCC patients had a better prognosis than LSCC in mucinous adenocarcinoma/signet ring cell carcinoma patients. RSCC patients also had a better prognosis than LSCC in stage II disease. There is a need for further subdivisions when analyzing the survival difference between RSCC and LSCC patients. RSCC had lower mortality rate than LSCC in stage II disease and mucinous adenocarcinoma/signet ring cell carcinoma patients.

Rectal Cancer in Asian vs. Western Countries: Why the Variation in Incidence?

OPINION STATEMENT

Colorectal cancer (CRC) is the third most common cancer worldwide. CRC has been thought to be less common in Asia compared to Western countries. However, the incidence rates of CRC in Asia are high and there is an increasing trend in the Asian population. Furthermore, colorectal cancer accounts for the greatest number of all incidences of CRC in Asia. The increasing adoption of a Western lifestyle, particularly in dietary habits, is likely the most important factor contributing to the rapid increase in colon cancer incidence; it is noteworthy that trends for rectal cancer were flat. The etiology of colon and rectal cancer is a bit different. The risks of distal colon and rectal cancers are more likely to be related to environmental factors, such as polluted surface water sources, alcohol consumption, and habitual smoking. The lack of great change in the incidence of rectal cancer might be due to weaker associations with such lifestyle factors. Therefore, it has been hypothesized that proximal and distal sections of the colon and rectum are two different organs in terms of function and genetic background. It may mean differences in differential sensitivities and exposures to carcinogens. However, despite the decrease in whole incidence, the CRC incidence in young adults in Western countries are reversely increasing, especially in rectal cancer, due to reasons largely unknown. Although the treatment algorithm is different between Asia and western countries, globally, the survival rate for patients with rectal cancer has risen during the past 10 years. Screening contributes a great deal to reducing the incidence and improving survival. Most countries in Asia, such as China, need nationwide registration and screening systems to provide better data.

In-silico and in-vitro investigation of a photonic monitor for intestinal perfusion and oxygenation

The quantification of visceral organ oxygenation after trauma-related systemic hypovolemia and shock is critical to enable effective resuscitation. In this work, a photoplethysmography-based (PPG) sensor was specifically designed for probing the perfusion and oxygenation condition of intestinal tissue with the ultimate goal to monitor patients post trauma to guide resuscitation. Through Monte Carlo modeling, suitable optofluidic phantoms were determined, the wavelength and separation distance for the sensor was optimized, and sensor performance for the quantification of tissue perfusion and oxygenation was tested on the in-vitro phantom. In particular, the Monte Carlo simulated both a standard block three-layer model and a more realistic model including villi. Measurements were collected on the designed three layer optofluidic phantom and the results taken with the small form factor PPG device showed a marked improvement when using shorter visible wavelengths over the more conventional longer visible wavelengths. Overall, in this work a Monte Carlo model was developed, an optofluidic phantom was built, and a small form factor PPG sensor was developed and characterized using the phantom for perfusion and oxygenation over the visible wavelength range. The results show promise that this small form factor PPG sensor could be used as a future guide to shock-related resuscitation.

Properties of synchronous spontaneous Ca2+ transients in the mural cells of rat rectal arterioles

Synchrony of spontaneous Ca²⁺ transients among venular mural cells (smooth muscle cells and pericytes) in visceral organs relies on the intercellular spread of L-type voltage-dependent Ca²⁺ channel (LVDCC)-dependent depolarisations. However, the mechanisms underlying the synchrony of spontaneous Ca²⁺ transients between arteriolar mural cells are less understood. The spontaneous intracellular Ca²⁺ dynamics of arteriolar mural cells in the rat rectal submucosa were visualised by Cal-520 Ca²⁺ imaging to analyse their synchrony. The mural cells in fine arterioles that had a rounded cell body with several extended processes developed spontaneous 'synchronous' Ca²⁺ transients arising from Ca²⁺ released from sarcoendoplasmic reticulum Ca²⁺ stores. Gap junction blockers (3 μM carbenoxolone, 10 μM 18β-glycyrrhetinic acid), a Ca²⁺-activated Cl^- channel (CaCC) blocker (100 μM 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid) or lowering extracellular Cl^- concentration (from 134.4 to 12.4 mM) disrupted the synchrony of Ca²⁺ transients between arteriolar mural cells. Blockers of T-type voltage-dependent Ca²⁺ channels (TVDCCs, 1 μM mibefradil or ML218) or LVDCCs (1 μM nifedipine) reduced the Ca²⁺ transient frequency or their area under curve (AUC), respectively. However, neither TVDCC nor LVDCC blockers disrupted the synchrony of Ca²⁺ transients among arteriolar mural cells. This is in contrast with rectal venules in which nifedipine disrupted the synchrony of spontaneous Ca²⁺ transients. Thus, spontaneous transient depolarisations arising from the opening of CaCCs may effectively spread to neighbouring arteriolar mural cells via gap junctions to maintain the Ca²⁺ transient synchrony. Activation of TVDCCs appears to accelerate spontaneous Ca²⁺ transients, while LVDCCs predominantly contribute to the duration of Ca²⁺ transients.

Wnt-expressing cells in the intestines: guides for tissue remodeling

The crypt is a minimal functional unit in the intestinal epithelium. This unique structure is maintained by surrounding mesenchymal cells that focally interact with associated epithelial cells. Canonical and non-canonical Wnt ligands enable specific microenvironments localized to each end of the crypt major axis. While canonical Wnt-expressing cells are localized near the crypt bottom where intestinal stem cells reside, non-canonical Wnt-expressing cells are positioned beneath the luminal surface of epithelial cells. During wound healing, propagation and appropriate relocation of each cell population are thought to ensure subsequent crypt regeneration. In this review, I integrate information from recent studies on Wnt-expressing cells and intestinal fibroblast lineages and discuss their roles in homeostasis and wound healing. More information on the lineages of Wnt-expressing cells will help clarify the mechanisms of epithelial tissue formation.

Differential DNA methylation patterns of homeobox genes in proximal and distal colon epithelial cells

Region and cell-type specific differences in the molecular make up of colon epithelial cells have been reported. Those differences may underlie the region-specific characteristics of common colon epithelial diseases such as colorectal cancer and inflammatory bowel disease. DNA methylation is a cell-type specific epigenetic mark, essential for transcriptional regulation, silencing of repetitive DNA and genomic imprinting. Little is known about any region-specific variations in methylation patterns in human colon epithelial cells. Using purified epithelial cells and whole biopsies (n= 19) from human subjects, we generated epigenome-wide DNA methylation data (using the HELP-tagging assay), comparing the methylation signatures of the proximal and distal colon. We identified a total of 125 differentially methylated sites (DMS) mapping to transcription start sites of protein-coding genes, most notably several members of the homeobox (HOX) family of genes. Patterns of differential methylation were validated with MassArray EpiTYPER. We also examined DNA methylation in whole biopsies, applying a computational technique to deconvolve variation in methylation within cell types and variation in cell-type composition across biopsies. Including inferred epithelial proportions as a covariate in differential methylation analysis applied to the whole biopsies resulted in greater overlap with the results obtained from purified epithelial cells compared with when the covariate was not included. Results obtained from both approaches highlight region-specific methylation patterns of HOX genes in colonic epithelium. Regional variation in methylation patterns has implications for the study of diseases that exhibit regional expression patterns in the human colon, such as inflammatory bowel disease and colorectal cancer.

Dietary calcium intake and the risk of colorectal cancer: a case control study

Background

High intake of dietary calcium has been thought to be a protective factor against colorectal cancer. To explore the dose-response relationship in the associations between dietary calcium intake and colorectal cancer risk by cancer location, we conducted a case-control study among Korean population, whose dietary calcium intake levels are relatively low.

Methods

The colorectal cancer cases and controls were recruited from the National Cancer Center in Korea between August 2010 and August 2013. Information on dietary calcium intake was assessed using a semi-quantitative food frequency questionnaire and locations of the colorectal cancers were classified as proximal colon cancer, distal colon cancer, and rectal cancer. Binary and polytomous logistic regression models were used to evaluate the association between dietary calcium intake and risk of colorectal cancer.

Results

A total of 922 colorectal cancer cases and 2766 controls were included in the final analysis. Compared with the lowest calcium intake quartile, the highest quartile group showed a significantly reduced risk of colorectal cancer in both men and women. (Odds ratio (OR): 0.16, 95 % confidence interval (CI): 0.11–0.24 for men; OR: 0.16, 95 % CI: 0.09–0.29 for women). Among the highest calcium intake groups, decrease in cancer risk was observed across all sub-sites of colorectum in both men and women.

Conclusion

In conclusion, calcium consumption was inversely related to colorectal cancer risk in Korean population where national average calcium intake level is relatively lower than Western countries. A decreased risk of colorectal cancer by calcium intake was observed in all sub-sites in men and women.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1963-9) contains supplementary material, which is available to authorized users.

Structural Changes in Large Intestinal Aggregated Lymphoid Follicles in Wistar Rats During Postnatal Ontogeny

Quantitative evaluation of aggregated lymphoid follicles in various compartments of the large intestine was carried out in Wistar rats of different age: newborn (3-4 days), prepubertal (20-30 days), adult (2-3 months), and old (16-18 months). No aggregated lymphoid tissue was detected in the large intestinal mucosa of newborn animals. The cecum of prepubertal, adult, and old animals contained solitary patches with 7-9 follicles. Higher percentage of aggregated lymphoid tissue, associated with colonic mucosa, was explained by enlargement of the lymphoid patch area and of the number of solitary lymphoid follicles during the postnatal ontogenesis. The mean area of a patch in the distal part of the colon in prepubertal, adult, and old animals was 3.2, 2.5, and 2.2 times larger than in the medial part of the intestine, the number of follicles per patch was 2.8, 2.8, and 2.5 times higher, respectively. The differences were significant only for the two younger groups.

Characterization of the anisotropic mechanical behaviour of colonic tissues: experimental activity and constitutive formulation

The aim was to investigate the biomechanical behaviour of colonic tissues by a coupled experimental and numerical approach. The wall of the colon is composed of different tissue layers. Within each layer, different fibre families are distributed according to specific spatial orientations, which lead to a strongly anisotropic configuration. Accounting for the complex histology of the tissues, mechanical tests must be planned and designed to evaluate the behaviour of the colonic wall in different directions. Uni-axial tensile tests were performed on tissue specimens from 15 fresh pig colons, accounting for six different loading directions (five specimens for each loading direction). The next step of the investigation was to define an appropriate constitutive framework and develop a procedure for identification of the constitutive parameters. A specific hyperelastic formulation was developed that accounted for the multilayered conformation of the colonic wall and the fibre-reinforced configuration of the tissues. The parameters were identified by inverse analyses of the mechanical tests. The comparison of model results with experimental data, together with the evaluation of satisfaction of material thermomechanics principles, confirmed the reliability of the analysis developed. This work forms the basis for more comprehensive activities that aim to provide computational tools for the interpretation of surgical procedures that involve the gastrointestinal tract, considering the specific biomedical devices adopted.

Opposite variation tendencies of serum CA724 levels in patients with colon and rectal carcinoma

The aim of this study was to investigate tumor biomarker carbohydrate antigen 724 (CA724) in the serum of patients with carcinomas of the colon and rectum at various clinical stages. Serum was collected from 51 patients with colon carcinoma (CC) and 49 patients with rectal carcinoma (RC). CA724 levels were then measured in the different groups according to site, TNM classification, gender, age and metastastic status of the patients. The statistical significance of the differences between the groups was calculated by non-parametric statistics (Mann-Whitney and Kruskall-Wallis tests). We observed a close association between the serum CA724 levels and tumor migration in colorectal carcinoma (CRC) and opposite variation tendencies of CA724 in the evolution of CC and RC. In conclusion, we identified a close association between the serum levels of CA724 and tumor migration in CRC. The opposite variation tendencies of CA724 in the different evolution groups of CC and RC may reflect the differences between these two types of cancer. The evaluation of serum CA724 may be of monitoring and and predictive value and may also assist in the development of treatment strategies for CRC patients.

Intestinal perfusion monitoring using photoplethysmography

In abdominal trauma patients, monitoring intestinal perfusion and oxygen consumption is essential during the resuscitation period. Photoplethysmography is an optical technique potentially capable of monitoring these changes in real time to provide the medical staff with a timely and quantitative measure of the adequacy of resuscitation. The challenges for using optical techniques in monitoring hemodynamics in intestinal tissue are discussed, and the solutions to these challenges are presented using a combination of Monte Carlo modeling and theoretical analysis of light propagation in tissue. In particular, it is shown that by using visible wavelengths (i.e., 470 and 525 nm), the perfusion signal is enhanced and the background contribution is decreased compared with using traditional near-infrared wavelengths leading to an order of magnitude enhancement in the signal-to-background ratio. It was further shown that, using the visible wavelengths, similar sensitivity to oxygenation changes could be obtained (over 50% compared with that of near-infrared wavelengths). This is mainly due to the increased contrast between tissue and blood in that spectral region and the confinement of the photons to the thickness of the small intestine. Moreover, the modeling results show that the source to detector separation should be limited to roughly 6 mm while using traditional near-infrared light, with a few centimeters source to detector separation leads to poor signal-to-background ratio. Finally, a visible wavelength system is tested in an in vivo porcine study, and the possibility of monitoring intestinal perfusion changes is showed.

Prognostic implication of the CpG island methylator phenotype in colorectal cancers depends on tumour location

BACKGROUND

Colorectal cancer (CRC) is usually categorised as proximal or distal CRC. Recently, many researchers have tried to determine the molecular heterogeneity of CRCs along bowel subsites. However, the differential effects of the CpG island methylator phenotype (CIMP) and microsatellite instability (MSI) on the clinical outcome according to tumour location are not well-known.

METHODS

We analysed clinicopathologic and molecular characteristics, including CIMP, MSI, KRAS and BRAF mutations, in 734 CRCs according to bowel subsites. And the prognostic value of CIMP and MSI was analysed according to tumour location.

RESULTS

We found a linear increase of female predominance, T, N category, stage, differentiation, absence of luminal necrosis, tumour -infiltrating lymphocytes, Crohn's-like lymphoid reaction, serration and mucin production from the rectum to caecum. CpG island methylator phenotype -high and MSI-high gradually increased from the rectum to caecum. CpG island methylator phenotype is a poor prognostic factor of overall survival (hazard ratio (HR): 4.13, 95% confidence interval (CI): 1.27-13.46) and disease-free survival (HR: 2.90, 95% CI: 1.04-8.08) in rectal cancers.

CONCLUSION

Clinicopathologic and molecular profiles of CRCs gradually change along bowel subsites, and the prognostic implication of CIMP is different according to tumour location.

Ultrastructural characterization of interstitial cells of Cajal associated with the submucosal plexus in the proximal colon of the guinea pig

Interstitial cells of Cajal (ICC) associated with the submucosal (submucous) plexus (ICC-SP) in the proximal colon of the guinea pig were studied by immunohistochemistry and electron microscopy. Whole-mount stretch preparations with c-Kit immunohistochemistry revealed that a number of ICC-SP constituted a dense cellular network around the submucosal plexus. Some of these ICC-SP were observed in the vicinity of the muscularis mucosae in sections immunostained for c-Kit and α-smooth muscle actin. Ultrastructural observation demonstrated, for the first time, that ICC-SP of the proximal colon of the guinea pig retained typical ultrastructural characteristics of ICC repeatedly reported in association with the tunica muscularis of the gastrointestinal tract: a basal lamina, caveolae, many mitochondria, abundant intermediate filaments and the formation of gap junctions with the same type of cells. The most remarkable ultrastructural finding was the presence of thick bundles composed of the processes of ICC-SP connected to each other via large gap junctions. These ICC-SP might be involved in the main mucosal functions of the proximal colon of the guinea pig, namely the transportation of water and electrolytes, possibly via their involvement in the spontaneous contractions of the muscularis mucosae.

Quantitative MRI of colonic mural enhancement: segmental differences exist in endoscopically proven normal colon

OBJECTIVES

Abnormal contrast enhancement on MRI is advocated as a biomarker for inflammation in colitis, although the enhancement kinetics of normal colon are poorly described. Our purpose was to quantitatively assess mural enhancement in normal colon and test for intersegmental differences.

METHODS

Eight patients without prior history of inflammatory bowel disease underwent standard MRI colonography followed by normal same-day colonoscopy. Acquired sequences included a volumetric interpolated breath-hold examination (VIBE) to encompass the whole colonic volume, performed at 5°, 10° and 35° flip angles for T(1) quantitation and then at a fixed 35° flip angle three times prior to and every 30 s following intravenous gadoterate meglumine for 220 s. Ascending colon, descending colon and rectal R(1) (1/T(1)) was plotted against time. Mean pre-contrast R(1), initial change of R(1) (ΔR(1)), early and late "plateau phase" enhancement and the area under the R(1)-time (AUC-R(1)) curve were compared between segments using the Student's paired t-test.

RESULTS

There was no significant difference of pre-contrast R(1) between segments (p=0.49 to 0.62). ΔR(1) was higher for ascending colon compared with descending colon (0.0023±0.0012 ms(-1) vs 0.0010±0.0011 ms(-1), p=0.03). There was no significant difference for early or late plateau phase R(1) between colonic segments (p=0.08 to 1.00). AUC-R(1) was greater for ascending than descending colon (0.54±0.19 vs 0.30±0.14, p=0.03).

CONCLUSIONS

Intersegmental differences in colonic enhancement are present and should be considered when interpreting differential segmental enhancement.

Influence of anatomical subsite on the incidence of microsatellite instability, and KRAS and BRAF mutation rates in patients with colon carcinoma

There is a growing amount of data supporting the concept that cancers originating from the proximal and distal colon are distinct clinicopathological entities. The incidence of MSI and BRAF mutation is strongly associated with right sided tumor location, whereas there are conflicting results for KRAS mutation rates. However, to date, no data exist whether and to what extent defined colonic subsites influence MSI status, KRAS and BRAF mutation rates. We selected primary colon cancer from 171 patients operated on at our institution between 2007 and 2010. BRAF, KRAS mutation rates and microsatellite instability were determined and correlated with clinicopathological features and tumor location. MSI-h cancers were significantly associated with poor histological grade but a lower rate of distant metastases. KRAS-mutated tumors were linked to lower T-stage and better differentiation. Colon carcinomas with BRAF mutation were significantly associated with distant metastatic spread and poor histological grade. Furthermore, we found that MSI-h status, KRAS and BRAF mutation rates varied remarkably among the colonic subsites irrespective of right- and left-sided origin, respectively. The results of the current study provide further evidence that a simple classification into right- and left-sided colon carcinoma does not represent the complexity of this tumor entity.

Impact of model parameters on Monte Carlo simulations of backscattering Mueller matrix images of colon tissue

Polarimetric imaging is emerging as a viable technique for tumor detection and staging. As a preliminary step towards a thorough understanding of the observed contrasts, we present a set of numerical Monte Carlo simulations of the polarimetric response of multilayer structures representing colon samples in the backscattering geometry. In a first instance, a typical colon sample was modeled as one or two scattering "slabs" with monodisperse non absorbing scatterers representing the most superficial tissue layers (the mucosa and submucosa), above a totally depolarizing Lambertian lumping the contributions of the deeper layers (muscularis and pericolic tissue). The model parameters were the number of layers, their thicknesses and morphology, the sizes and concentrations of the scatterers, the optical index contrast between the scatterers and the surrounding medium, and the Lambertian albedo. With quite similar results for single and double layer structures, this model does not reproduce the experimentally observed stability of the relative magnitudes of the depolarizing powers for incident linear and circular polarizations. This issue was solved by considering bimodal populations including large and small scatterers in a single layer above the Lambertian, a result which shows the importance of taking into account the various types of scatterers (nuclei, collagen fibers and organelles) in the same model.

Ex-vivo characterization of human colon cancer by Mueller polarimetric imaging

Cancerous and healthy human colon samples have been analyzed ex-vivo using a multispectral imaging Mueller polarimeter operated in the visible (from 500 to 700 nm) in a backscattering configuration with diffuse light illumination. Three samples of Liberkühn colon adenocarcinomas have been studied: common, mucinous and treated by radiochemotherapy. For each sample, several specific zones have been chosen, based on their visual staging and polarimetric responses, which have been correlated to the histology of the corresponding cuts. The most relevant polarimetric images are those quantifying the depolarization for incident linearly polarized light. The measured depolarization depends on several factors, namely the presence or absence of tumor, its exophytic (budding) or endophytic (penetrating) nature, its thickness (its degree of ulceration) and its level of penetration in deeper layers (submucosa, muscularis externa and serosa). The cellular density, the concentration of stroma, the presence or absence of mucus and the light penetration depth, which increases with wavelength, are also relevant parameters. Our data indicate that the tissues with the lowest and highest depolarizing powers are respectively mucus-free tumoral tissue with high cellular density and healthy serosa, while healthy submucosa, muscularis externa as well as mucinous tumor probably feature intermediate values. Moreover, the specimen coming from a patient treated successfully with radiochemotherapy exhibited a uniform polarimetric response typical of healthy tissue even in the initially pathological zone. These results demonstrate that multi-spectral Mueller imaging can provide useful contrasts to quickly stage human colon cancer ex-vivo and to distinguish between different histological variants of tumor.

Colorectal cancer, one entity or three

Understanding of the mechanism of colorectal carcinogenesis has been gaining momentum for some years on account of its high incidence and impact on the lives of individuals affected. Different genetic abnormalities have been found in colorectal cancers from different sites. For example, proximal colon cancer is usually related to the nucleotide instability pathway, as microsatellite instability (MSI). However, distal colon cancer is usually associated with specific chromosomal instability (CIN). The development of cancer at the rectum, though similar to that at the colon, displays its own unique features. These differences might be partially attributed to different embryological development and physiological circumstances. Environmental factors such as diet and alcohol intake also differ in their role in the development of tumors in the three segments, proximal colon, distal colon, and rectum. "Proximal shift" of colon cancer has been known for some time, and survival rates of colorectal cancer are higher when rectal cancers are excluded, both of which emphasize the three different segments of colorectal cancer and their different properties. Meanwhile, colonic and rectal cancers are distinctive therapeutic entities. The concept of three entities of colorectal cancer may be important in designing clinical trails or therapeutic strategies. However, the dispute about the inconsistency of data concerning the site-specific mechanism of colorectal carcinoma does exist, and more evidence about molecular events of carcinogenesis and targeted therapy needs to be collected to definitely confirm the conception.

Characterization of interstitial cells of Cajal in the subserosal layer of the guinea-pig colon

Interstitial cells of Cajal in the subserosa (ICC-SS) of the guinea-pig proximal colon were studied by immunohistochemistry for c-Kit receptors and by transmission electron microscopy. These cells were distributed within a thin layer of connective tissue space immediately beneath the mesothelium and were multipolar with about five primary cytoplasmic processes that divided further into secondary and tertiary processes to form a two-dimensional network. Ultrastructural observations revealed that ICC-SS were connected to each other via gap junctions. They also formed close contacts and peg-and-socket junctions with smooth muscle cells. Three-dimensional analysis of confocal micrographs revealed that the cytoplasmic processes of ICC-SS had contacts with interstitial cells in the longitudinal muscle layer. Taking account of the location and peculiar arrangement of the ICC-SS and the main functions of the proximal colon, i.e. the absorption and transport of fluids, we suggest that the superficial network of ICC-SS acts as a stretch receptor to detect circumferential expansion and swelling of the colon wall and triggers the contraction of the longitudinal muscle to accelerate the drainage of fluids from the colon.

Confocal endomicroscopy in patients with ulcerative colitis

BACKGROUND

Confocal endomicroscopy is a new technology that provides microscopic images of cellular morphology in the gastrointestinal tract in vivo. In particular, confocal microendoscopy allows histological diagnosis during the endoscopic examination. We examined patients with ulcerative colitis (UC) using confocal endoscopy and investigated the features of confocal endomicroscopic images of inflamed and non-inflamed rectal mucosa.

METHODS

Seventeen patients with UC, 12 in the active phase and 5 in the non-active phase, and 14 non-UC control patients who had colon polyps or colon cancer underwent colonoscopy, during which fluorescence images of the rectal mucosa were obtained with confocal endomicroscopy. Histological findings of rectal biopsy specimens were compared with the microendoscopic images.

RESULTS

Confocal microendoscopy allowed observation of cellular and subcellular structures. The crypts of normal colonic mucosa were small, round and regularly arranged, and the crypt lumens of the colonic glands were small and round. The crypts of colonic mucosa in non-active UC were small, round and slightly irregular in arrangement and the crypt lumens of the colonic glands were small and round. Inflammatory cells and capillaries were visible in the lamina propria. The crypts of colonic mucosa in active UC were large, variously shaped and irregular in arrangement. The crypt lumens of the colonic glands were large and the crypt structure could not be recognized in some areas. Numerous inflammatory cells and capillaries were visible in the lamina propria.

CONCLUSIONS

Images taken with the confocal microendoscope provided information that was equivalent to conventional histology, and improve our understanding of the differences in rectal tissues (crypts, capillaries and inflammatory cells) between normal controls and active and non-active UC patients during ongoing endoscopy.

Colorectal cancer or colon and rectal cancer? Clinicopathological comparison between colonic and rectal carcinomas

AIMS

The aim of this study was to compare features of colon and rectal cancers such as prognosis, clinicopathological features and tumor markers, namely carcinoembryonic antigen (CEA), matrix metalloproteinase (MMP)-2 and p27(kip1).

METHODS

Two hundred and thirty patients with stage I-III colon or rectal cancer were retrospectively assessed with the endpoint of recurrence or metastasis after curative operation. CEA, MMP-2 and p27(kip1) were studied by immunohistochemistry in cancer tissues of all patients.

RESULTS

The disease-free 3-year survival rate after operation of the total 230 patients was 63.0%. The prognosis of colon cancer was significantly better than that of rectal cancer (70.6 vs. 57.0%; p = 0.017), especially for stage III (p = 0.0059). Multivariate analysis also demonstrated that tumor location in the colon or rectum, differentiation, venous invasion and the expression of CEA were independent factors for prognosis. The hazard of recurrence and metastasis in rectal cancer was 1.564 times that in colon cancer. In both groups, there were no statistical differences in age, gender, tumor size, tumor gross type, mucin production, tumor differentiation, venous invasion, MMP-2 and p27(kip1).

CONCLUSION

We investigated prognosis, clinicopathological factors, oncogenes and tumor suppressor gene production in colon and rectal cancers. The prognosis of colon cancer is better than that of rectal cancer, especially for stage III. This study shows some differences between colon and rectal cancer.

Development of the mucosal vascular system in the distal colon of the fetal mouse

The formation of the crypt in the distal colon of the mouse was investigated in association with the development of vascular networks. For histological observation, 1-microm cross-sections were made from the distal colon of fetal mice in 13 to 18 days of gestation. Three-dimensional distributions of vascular networks in the organ were observed after perfusing fetuses with rhodamine isothiocyanate-labeled gelatin and immunostaining for laminin to examine the boundary between the epithelium and the mesenchyme. At 13 days of gestation, the distal colon and its epithelium formed a cylindrical tube and a loose primary plexus of vessels was built in the mesenchyme. In the distal colon of 15 days of gestation, the caudal portion began to form the crypt and the vascular plexus built up from a few layers was situated apart from the boundary between the epithelium and the mesenchyme. As the development proceeded, the formation of the crypt occurred in the caudorostral direction. The developing crypt advanced into the vascular plexus, so that a few vessels situated in the mesenchyme between crypts. As the crypt elongated, these vessels formed a small plexus situated perpendicular to the primary plexus, while the primary plexus became monolayered and loosened. The new plexus was composed of ascending vessels and traversing ones, but the regular honeycomb-like plexuses around openings of crypts have not established yet even in 18 days of gestation. The vascular system as well as the crypt in the distal colon will take further a few postnatal weeks to be completed.

eNOS involved in colitis-induced mucosal blood flow increase

The role of NO in inflammatory bowel disease is controversial. Studies indicate that endothelial nitric oxide synthase (eNOS) might be involved in protecting the mucosa against colonic inflammation. The aim of this study was to investigate the involvement of nitric oxide (NO) in regulating colonic mucosal blood flow in two different colitis models in rats. In anesthetized control and colitic rats, the distal colon was exteriorized and the mucosa visualized. Blood flow (laser-Doppler flowmetry) and arterial blood pressure were continuously monitored throughout the experiments, and vascular resistance was calculated. Trinitrobenzene sulfonic acid (TNBS) or dextran sulfate sodium (DSS) was used to induce colitis. All groups were given the NOS inhibitor N(omega)-nitro-l-arginine (l-NNA) or the inducible NOS (iNOS) inhibitor l-N(6)-(1-iminoethyl)-lysine (l-NIL). iNOS, eNOS, and neuronal NOS (nNOS) mRNA in colonic samples were investigated with real-time RT-PCR. Before NOS inhibition, colonic mucosal blood flow, expressed as perfusion units, was higher in both colitis models compared with the controls. The blood flow was reduced in the TNBS- and DSS-treated rats during l-NNA administration but was not altered in the control group. Vascular resistance increased more in the TNBS- and DSS-treated rats than in the control rats, indicating a higher level of vasodilating NO in the colitis models. l-NIL did not alter blood pressure or blood flow in any of the groups. iNOS and eNOS mRNA increased in both colitis models, whereas nNOS remained at the control level. TNBS- and DSS-induced colitis results in increased colonic mucosal blood flow, most probably due to increased eNOS activity.

A fluorescence confocal endomicroscope for in vivo microscopy of the upper- and the lower-GI tract

BACKGROUND

This report describes the development and the clinical evaluation of a novel confocal endomicroscope for obtaining fluorescence images of cellular morphology of the mucosae of the upper- and the lower-GI tract in vivo. The work assessed the feasibility of performing in vivo microscopy at endoscopic examination and evaluated fluorescence imaging protocols.

METHODS

Images were collected in real time by using two prototype endoscope configurations, featuring slightly different miniaturized fiber-optic confocal microscopes, fitted integrally into the tips of conventional endoscopes. Confocal scanning was performed at 488 nm illumination for excitation of exogenously applied fluorophores (topical acriflavine and intravenous fluorescein). The images were compared with conventional histology of biopsy specimens and the findings of white-light endoscopy.

RESULTS

Confocal endomicroscopy enabled imaging of cellular and subcellular structures (i.e., nuclei) of the GI tract. The crypts of the colonic mucosa, the villi of the terminal ileum and duodenum, the gastric pits of the stomach, and the squamous epithelium of the distal esophagus could be clearly visualized. Acriflavine strongly contrasted the cell nuclei of the surface epithelium, including the absorptive epithelial cells and the mucous secreting goblet cells. Fluorescein stained the extracellular matrix of the surface epithelium and also the subepithelial layers of the lamina propria. Images at increasing depth beneath the epithelium showed the mucosal capillary network. The findings correlated with the histology of biopsy specimens.

CONCLUSIONS

The development of a fluorescence confocal endomicroscope makes it practical to examine the upper- and the lower-GI mucosa in cellular detail during otherwise routine endoscopic examination. The results represent a major technical advance in the development of this new optical imaging modality for the in vivo examination of GI tissue.

Modelling and validation of spectral reflectance for the colon

The spectral reflectance of the colon is known to be affected by malignant and pre-malignant changes in the tissue. As part of long-term research on the derivation of diagnostically important parameters characterizing colon histology, we have investigated the effects of the normal histological variability on the remitted spectra. This paper presents a detailed optical model of the normal colon comprising mucosa, submucosa and the smooth muscle layer. Each layer is characterized by five variable histological parameters: the volume fraction of blood, the haemoglobin saturation, the size of the scattering particles, including collagen, the volume fraction of the scattering particles and the layer thickness, and three optical parameters: the anisotropy factor, the refractive index of the medium and the refractive index of the scattering particles. The paper specifies the parameter ranges corresponding to normal colon tissue, including some previously unpublished ones. Diffuse reflectance spectra were modelled using the Monte Carlo method. Validation of the model-generated spectra against measured spectra demonstrated that good correspondence was achieved between the two. The analysis of the effect of the individual histological parameters on the behaviour of the spectra has shown that the spectral variability originates mainly from changes in the mucosa. However, the submucosa and the muscle layer must be included in the model as they have a significant constant effect on the spectral reflectance above 600 nm. The nature of variations in the spectra also suggests that it may be possible to carry out model inversion and to recover parameters characterizing the colon from multi-spectral images. A preliminary study, in which the mucosal blood and collagen parameters were modified to reflect histopathological changes associated with colon cancer, has shown that the spectra predicted by our model resemble measured spectral reflectance of adenocarcinomas. This suggests that an extended model, which incorporates parameters corresponding to an abnormal colon, may be effective for differentiation between normal and cancerous tissues.

Are there two sides to colorectal cancer?

Colorectal carcinomas (CRC) that arise proximal (right) or distal (left) to the splenic flexure exhibit differences in incidence according to geographic region, age and gender. Together with observations that tumours in the hereditary cancer syndromes HNPCC and FAP occur predominantly in the right and left colon, respectively, the existence of 2 categories of CRC based on site of origin in the large bowel was proposed more than a decade ago. Differences between normal right and left colonic segments that could favour progression through different tumourigenic pathways are summarized in this review. Accumulating evidence suggests that the risk of CRC conferred by various environmental and genetic factors is different for proximal and distal tumours. Right- and left-sided tumours also exhibit different sensitivities to fluorouracil-based chemotherapy. Such differences are probably related to the molecular characteristics of the tumours, with the microsatellite instability and CpG island methylator phenotypes being associated with right-sided tumours and chromosomal instability with left-sided tumours. Future molecular-based classification systems for CRC that rely upon distinctive gene expression patterns may allow a clearer discrimination of subgroups than that provided by tumour site alone. Until then however, the existence of 2 broadly different groups of cancer defined by site of origin in the colon should be considered in the design of future epidemiologic studies as well as in the design of new clinical trials aimed at testing novel adjuvant therapies.

Evidence for modulation of pericryptal sheath myofibroblasts in rat descending colon by transforming growth factor beta and angiotensin II

BACKGROUND

Absorption of water and Na+ in descending colonic crypts is dependent on the barrier function of the surrounding myofibroblastic pericryptal sheath. Here the effects of high and low Na+ diets and exposure to whole body ionising radiation on the growth and activation of the descending colonic pericryptal myofibroblasts are evaluated. In addition the effect of a post-irradiation treatment with the angiotensin converting enzyme inhibitor Captopril was investigated.

METHODS

The levels of Angiotensin II type 1 receptor (AT1), ACE, collagen type IV, transforming growth factor-beta type 1 receptor (TGF-betaR1), OB cadherin and alpha-smooth muscle actin in both descending colon and caecum were evaluated, using immunocytochemistry and confocal microscopy, in rats fed on high and low Na+ diets (LS). These parameters were also determined during 3 months post-irradiation with 8Gy from a 60Co source in the presence and absence of the angiotensin converting enzyme inhibitor, Captopril.

RESULTS

Increases in AT1 receptor (135.6% +/- 18.3, P < 0.001); ACE (70.1% +/- 13.1, P < 0.001); collagen type IV (49.6% +/- 15.3, P < 0.001); TGF-+/-beta1 receptors (291.0% +/- 26.5, P < 0.001); OB-cadherin (26.3% +/- 13.8, P < 0.05) and alpha-smooth muscle actin (82.5% +/- 12.4, P < 0.001) were observed in the pericryptal myofibroblasts of the descending colon after LS diet. There are also increases in AT1 receptor and TGF-beta1 receptor, smooth muscle actin and collagen type IV after irradiation. Captopril reduced all these effects of irradiation on the pericryptal sheath and also decreased the amount of collagen and smooth muscle actin in control rats (P < 0.001).

CONCLUSIONS

These results demonstrate an activation of descending colonic myofibroblasts to trophic stimuli, or irradiation, which can be attenuated by Captopril, indicative of local trophic control by angiotensin II and TGF-beta release.

Regional crypt function in rat large intestine in relation to fluid absorption and growth of the pericryptal sheath

1. Confocal microscopic studies of rat colonic mucosa showed that the pericryptal sheath surrounding distal colonic crypts is an effective barrier both to dextran and NaCl movement, whereas no such structure surrounds the caecal crypts. 2. The distal colonic pericryptal barrier was functionally demonstrated by accumulation of Sodium Green within the pericryptal space. After exposure to benzamil, Sodium Green accumulation was decreased. Fluorescein isocyanate-labelled dextran (FITC dextran; molecular mass 10000 Da) was accumulated in the crypt lumens and pericryptal spaces. Both dextran and Sodium Green accumulation were absent from the pericryptal zone surrounding caecal crypts. 3. Low dietary Na+ intake raised rat plasma aldosterone and stimulated distal pericryptal sheath growth and adhesiveness as shown by increased amounts of F-actin, smooth muscle actin, beta-catenin and E-cadherins in the pericryptal zone. It also raised the capacity of the distal colon to dehydrate against a high luminal hydraulic resistance. This linkage indicates that trophic effects on the colon resulting from a low Na+ diet are not confined solely to effects on transepithelial Na+ transport, but are observed in the pericryptal sheath. 4. A computer model of crypt function confirms that a pericryptal sheath with low permeability to NaCl is an essential component of the crypt dehydrating mechanism.