Normal length of the human fetal gastrointestinal tract

Immune subset-committed proliferating cells populate the human foetal intestine throughout the second trimester of gestation

The intestine represents the largest immune compartment in the human body, yet its development and organisation during human foetal development is largely unknown. Here we show the immune subset composition of this organ during development, by longitudinal spectral flow cytometry analysis of human foetal intestinal samples between 14 and 22 weeks of gestation. At 14 weeks, the foetal intestine is mainly populated by myeloid cells and three distinct CD3^-CD7⁺ ILC, followed by rapid appearance of adaptive CD4⁺, CD8⁺ T and B cell subsets. Imaging mass cytometry identifies lymphoid follicles from week 16 onwards in a villus-like structure covered by epithelium and confirms the presence of Ki-67⁺ cells in situ within all CD3^-CD7⁺ ILC, T, B and myeloid cell subsets. Foetal intestinal lymphoid subsets are capable of spontaneous proliferation in vitro. IL-7 mRNA is detected within both the lamina propria and the epithelium and IL-7 enhances proliferation of several subsets in vitro. Overall, these observations demonstrate the presence of immune subset-committed cells capable of local proliferation in the developing human foetal intestine, likely contributing to the development and growth of organized immune structures throughout most of the 2^nd trimester, which might influence microbial colonization upon birth.

Ciliary Hedgehog signaling patterns the digestive system to generate mechanical forces driving elongation

How tubular organs elongate is poorly understood. We found that attenuated ciliary Hedgehog signaling in the gut wall impaired patterning of the circumferential smooth muscle and inhibited proliferation and elongation of developing intestine and esophagus. Similarly, ablation of gut-wall smooth muscle cells reduced lengthening. Disruption of ciliary Hedgehog signaling or removal of smooth muscle reduced residual stress within the gut wall and decreased activity of the mechanotransductive effector YAP. Removing YAP in the mesenchyme also reduced proliferation and elongation, but without affecting smooth muscle formation, suggesting that YAP interprets the smooth muscle-generated force to promote longitudinal growth. Additionally, we developed an intestinal culture system that recapitulates the requirements for cilia and mechanical forces in elongation. Pharmacologically activating YAP in this system restored elongation of cilia-deficient intestines. Thus, our results reveal that ciliary Hedgehog signaling patterns the circumferential smooth muscle to generate radial mechanical forces that activate YAP and elongate the gut.

In the Short-term, Milk Fat Globule Epidermal Growth Factor-8 Causes Site-specific Intestinal Growth in Resected Piglets

OBJECTIVES

Short bowel syndrome (SBS) remains the leading cause of neonatal intestinal failure. Milk fat globule epidermal growth factor-8 (MFG-E8), present in human milk, has homology with epidermal growth factor (EGF), known to enhance adaptation in SBS. In this pilot study, the role of oral MFG-E8 treatment in SBS was explored in neonatal piglets.

METHODS

Neonatal piglets underwent 75% intestinal resection, either distal (jejunal-colonic [JC] anastomosis) or mid-intestinal (jejunal-ileal [JI] anastomosis). Piglets were randomized to intragastric treatment with MFG-E8  (5 mg/kg per day) or saline and were maintained on parenteral nutrition and enteral nutrition for 7 days. Adaptation was assessed by intestinal length and weight, histopathology, fecal fat analysis and RT-qPCR analysis of mucosal transcripts, including growth factors.

RESULTS

JI piglets demonstrated intestinal lengthening (P < 0.001), 2-fold greater in ileum than jejunum (P = 0.02), where lengthening was increased by MFG-E8 treatment (P = 0.02). JC piglets did not exhibit jejunal lengthening, regardless of treatment. Fat absorption was greater for JI piglets (P = 0.02), unaffected by treatment. In JI piglets, expression of Egf was increased in the ileum (P < 0.01) and MFG-E8 treatment increased Egfr (receptor) expression (P = 0.02).

CONCLUSIONS

MF-EG8 demonstrated site-specific trophic effects, only with JI anatomy. This may limit the utility of this treatment for SBS, except for rare patients with retained ileum. The mechanisms of these site-specific effects, however, and the role of MFG-E8 in neonatal gut growth and in diseases, such as necrotizing enterocolitis that commonly target ileum, warrant further exploration.

Congenital Short-Bowel Syndrome: Clinical and Genetic Presentation in China

BACKGROUND

Congenital short-bowel syndrome (CSBS) is a rare disorder characterized by retardation of intestinal development. However, it is still not well recognized at present. In this study, the etiological, clinical, and genetic characteristics of CSBS in China were analyzed.

METHODS

Nine infants with CSBS were recruited. Full-thickness biopsy findings were evaluated by histopathology. Whole-exome sequencing was performed to identify mutations in patients and their family members. All patients were followed up at >1 year of age.

RESULTS

Six of 9 infants had malrotation, and 2 patients had intestinal atresia. The average total small-bowel length was 51.7 (40-75) cm. Coxsackie and adenovirus receptor-like membrane protein (CLMP) mutations were found in 5 patients and were related to decreases in ileal goblet cells and mucous secretion. Among these 5 patients, 3 shared the same mutation (c. 206G>A p.R69H), 1 patient had an exon 3-5 deletion, and 1 patient had the C.655T>G, p.Cys219Gly, and C.389-2A>C. Another case carried a loss-of-function mutation in filamin A (FLNA). In the other 3 patients, no pathogenic mutations in genes related to intestinal development were found. The rate of catheter-related bloodstream infection was 4.3 per 1000 catheter days, and intestinal failure-associated liver disease (IFALD) was 77.8%. The median follow-up duration was 24.1 months. Eight patients were weaned off parenteral nutrition (PN). Six patients still exhibited malnutrition during follow-up.

CONCLUSIONS

Infants with CSBS often need long-term PN and remain at risk of SBS-related complications. CLMP and FLNA mutations are associated with CSBS in the Chinese population.

Fetal Physiologically Based Pharmacokinetic Models: Systems Information on the Growth and Composition of Fetal Organs

BACKGROUND

The growth of fetal organs is a dynamic process involving considerable changes in the anatomical and physiological parameters that can alter fetal exposure to xenobiotics in utero. Physiologically based pharmacokinetic models can be used to predict the fetal exposure as time-varying parameters can easily be incorporated.

OBJECTIVE

The objective of this study was to collate, analyse and integrate the available time-varying parameters needed for the physiologically based pharmacokinetic modelling of xenobiotic kinetics in a fetal population.

METHODS

We performed a comprehensive literature search on the physiological development of fetal organs. Data were carefully assessed, integrated and a meta-analysis was performed to establish growth trends with fetal age and weight. Algorithms and models were generated to describe the growth of these parameter values as functions of age and/or weight.

RESULTS

Fetal physiologically based pharmacokinetic parameters, including the size of the heart, liver, brain, kidneys, lungs, spleen, muscles, pancreas, skin, bones, adrenal and thyroid glands, thymus, gut and gonads were quantified as a function of fetal age and weight. Variability around the means of these parameters at different fetal ages was also reported. The growth of the investigated parameters was not consistent (with respect to direction and monotonicity).

CONCLUSION

Despite the limitations identified in the availability of some values, the data presented in this article provide a unique resource for age-dependent organ size and composition parameters needed for fetal physiologically based pharmacokinetic modelling. This will facilitate the application of physiologically based pharmacokinetic models during drug development and in the risk assessment of environmental chemicals and following maternally administered drugs or unintended exposure to environmental toxicants in this population.

Papio spp. Colon microbiome and its link to obesity in pregnancy

INTRODUCTION

Gut microbial communities are critical players in the pathogenesis of obesity. Pregnancy is associated with increased bacterial load and changes in gut bacterial diversity. Sparse data exist regarding composition of gut microbial communities in obesity combined with pregnancy.

MATERIAL AND METHODS

Banked tissues were collected under sterile conditions during necropsy, from three non-obese (nOb) and four obese (Ob) near-term pregnant baboons. Sequences were assigned taxonomy using the Ribosomal Database Project classifier. Microbiome abundance and its difference between distinct groups were assessed by a nonparametric test.

RESULTS

Three families predominated in both the nOb and Ob colonic microbiome: Prevotellaceae (25.98% and 32.71% respectively), Ruminococcaceae (12.96% and 7.48%), and Lachnospiraceae (8.78% and 11.74%). Seven families of the colon microbiome displayed differences between Ob and nOb groups.

CONCLUSION

Changes in gut microbiome in pregnant obese animals open the venue for dietary manipulation in pregnancy.

Etiology and prognosis of pediatric short bowel syndrome

Pediatric intestinal failure is a complex and devastating condition defined as the inability of the intestine to absorb an adequate amount of fluid and nutrients to sustain life. The primary goal of intestinal failure treatment is to achieve enteral autonomy with a customized treatment plan. Although recent improvements in intestinal failure patient care have led to significant improvements in the morbidity and mortality rate, children with intestinal failure are at risk for multiple complications such as intestinal failure associated liver disease, recurrent septic episodes, central line complications, metabolic bone disease, impaired kidney function, and failure to thrive. In this article, we review the current literature on the etiology and factors affecting prognosis of pediatric IF.

Development of a Novel Maternal-Fetal Physiologically Based Pharmacokinetic Model I: Insights into Factors that Determine Fetal Drug Exposure through Simulations and Sensitivity Analyses

Determining fetal drug exposure (except at the time of birth) is not possible for both logistical and ethical reasons. Therefore, we developed a novel maternal-fetal physiologically based pharmacokinetic (m-f-PBPK) model to predict fetal exposure to drugs and populated this model with gestational age-dependent changes in maternal-fetal physiology. Then, we used this m-f-PBPK to: 1) perform a series of sensitivity analyses to quantitatively demonstrate the impact of fetoplacental metabolism and placental transport on fetal drug exposure for various drug-dosing regimens administered to the mother; 2) predict the impact of gestational age on fetal drug exposure; and 3) demonstrate that a single umbilical venous (UV)/maternal plasma (MP) ratio (even after multiple-dose oral administration to steady state) does not necessarily reflect fetal drug exposure. In addition, we verified the implementation of this m-f-PBPK model by comparing the predicted UV/MP and fetal/MP AUC ratios with those predicted at steady state after an intravenous infusion. Our simulations yielded novel insights into the quantitative contribution of fetoplacental metabolism and/or placental transport on gestational age-dependent fetal drug exposure. Through sensitivity analyses, we demonstrated that the UV/MP ratio does not measure the extent of fetal drug exposure unless obtained at steady state after an intravenous infusion or when there is little or no fluctuation in MP drug concentrations after multiple-dose oral administration. The proposed m-f-PBPK model can be used to predict fetal exposure to drugs across gestational ages and therefore provide the necessary information to assess the risk of drug toxicity to the fetus.

Management of short bowel syndrome in infancy

Short bowel syndrome (SBS) is a reduction in functioning bowel length which is most often a result of surgical resection. Risk factors in the neonatal period include necrotising enterocolitis, small bowel atresia and gastroschisis. With increasing survival of preterm infants there is an increase in incidence. Management is dependent on the use of parenteral nutrition to maintain fluid and electrolyte homeostasis and promote growth and development with the longer term aim being to promote intestinal adaptation to achieve partial or complete enteral autonomy. In this review we discuss the incidence, aetiology, pathophysiology, medical and surgical treatments and outcome.

Hedgehog-responsive mesenchymal clusters direct patterning and emergence of intestinal villi

In the adult intestine, an organized array of finger-like projections, called villi, provide an enormous epithelial surface area for absorptive function. Villi first emerge at embryonic day (E) 14.5 from a previously flat luminal surface. Here, we analyze the cell biology of villus formation and examine the role of paracrine epithelial Hedgehog (Hh) signals in this process. We find that, before villus emergence, tight clusters of Hh-responsive mesenchymal cells form just beneath the epithelium. Cluster formation is dynamic; clusters first form dorsally and anteriorly and spread circumferentially and posteriorly. Statistical analysis of cluster distribution reveals a patterned array; with time, new clusters form in spaces between existing clusters, promoting approximately four rounds of villus emergence by E18.5. Cells within mesenchymal clusters express Patched1 and Gli1, as well as Pdgfrα, a receptor previously shown to participate in villus development. BrdU-labeling experiments show that clusters form by migration and aggregation of Hh-responsive cells. Inhibition of Hh signaling prevents cluster formation and villus development, but does not prevent emergence of villi in areas where clusters have already formed. Conversely, increasing Hh signaling increases the size of villus clusters and results in exceptionally wide villi. We conclude that Hh signals dictate the initial aspects of the formation of each villus by controlling mesenchymal cluster aggregation and regulating cluster size.

Development of fetal intestinal length during 2nd-trimester in normal and pathologic pregnancies

Linear growth of the human fetal gastrointestinal tract is not often discussed in the literature, and little is known about the effects of chromosomal abnormalities and intrauterine growth restriction (IUGR) on intestinal length, especially during the 2nd trimester. Accurate evaluation of intestinal length and knowledge of normal and reference values are of clinical importance. For example, intestinal resection may be necessary in preterm infants with necrotizing enterocolitis or mid-gut volvulus, and the surgeon should use data to be judicious in the amount removed. Linear measurements are essential in evaluating fetal development ultrasonographically and are an integral part of the postmortem examination. The intestinal lengths of 203 2nd-trimester fetuses and premature infants were measured. Small intestine length (SIL), colon length (CL), total bowel length (TBL; TBL  =  SIL + CL), and the length of the appendix (AL) increased with gestational age. No differences between the genders were observed. Colon length increased secondary to maceration, but no such effects were shown on SIL, TBL, or AL. No differences were shown in relation to IUGR. Small intestine length, CL, and TBL, but not AL, were shorter in fetuses with trisomy 21. Appendix length was not affected by any of the studied factors. We propose that the measurement of the length of the appendix may be used as an additional parameter for the postmortem evaluation of gestational age. Furthermore, its assessment may have potential as an ultrasonographic indicator of gestational age, particularly for the 2nd trimester.

Humans, mice, and mechanisms of intestinal atresias: a window into understanding early intestinal development

INTRODUCTION

Intestinal atresias have long been hypothesized to result from either failure of recanalization of the intestinal lumen or in utero vascular accidents. Recent work in animal models is now calling for a reassessment of these widely held paradigms.

PURPOSE

In this review, we will examine the data that led to the original hypotheses and then evaluate more recent work challenging these hypotheses. Furthermore, we will discuss how defining the mechanism of atresia formation in animal models may provide insight into early intestinal development and the mechanism of lengthwise intestinal growth.

CONCLUSION

Such insight will be critical in developing regenerative therapies for patients with intestinal failure.

Short bowel syndrome: epidemiology and etiology

Pediatric short bowel syndrome (SBS) is most commonly caused by congenital or acquired conditions of the newborn. SBS is associated with an inability of the bowel to adequately absorb water and nutrients in sufficient quantities to meet caloric, fluid, and electrolyte demands, thus necessitating dependence on parenteral nutrition (PN). It is this dependence on PN, that is responsible for the majority of morbidity and mortality associated with SBS, including central venous catheter infections and PN-induced cholestatic liver dysfunction. There are very few estimates of SBS incidence and mortality in the literature. The epidemiology of SBS is reviewed and the limitations of the published literature are discussed.

Establishing norms for intestinal length in children

BACKGROUND

Existing data on pediatric intestinal length (IL) are limited because most studies report postmortem values. Using prospective data, appropriate norms for IL were developed.

METHOD

The IL measurements, using a silk suture on the antimesenteric border, were prospectively made on patients between 24 weeks of gestational age and 5 years of age undergoing laparotomy. Patients with gastrointestinal malformations or those above or below 2 SDs for growth parameters were excluded. A curve fitting process was applied to determine the best model for IL (small bowel and colon separately) from among postconception age, weight, and height at surgery.

RESULTS

One hundred eight patients participated in this study. Highly predictive (R(2) > 0.8) models for IL were determined for all predictor variables (postconception age, weight, and height) examined suggesting that all of these variables are excellent predictors determinants of IL. Although all models had statistically similar properties, the model using height had the best performance across the full range of the variable.

CONCLUSION

Although age, weight, nor height was definitely superior for the prediction of IL, we propose that until external validations of our models occur, height at surgery be used for the prediction of expected small intestinal and colon length in infants.

Lactoferrin induces concentration-dependent functional modulation of intestinal proliferation and differentiation

Human milk stimulates intestinal development through the effects of various moieties. Lactoferrin (LF) is a glycoprotein of human milk whose concentration is highest in colostrum decreasing in mature milk. LF promotes enterocyte growth in intestinal cell lines. We tested the hypothesis that LF induces a distinct effect on enterocyte proliferation and differentiation, depending on its concentration. We examined the dose-related effects by human-native LF (N-LF) in Caco-2 (human colon adenocarcinoma) cells. At high concentrations, N-LF stimulated cell proliferation in immature Caco-2 cells, as judged by 3H-thymidine incorporation. In contrast, sucrase and lactase activities were increased at low but not high LF concentrations and their mRNA were also increased, indicating a transcriptional effect. Because iron binds specific LF sites, we compared the potency of N-LF and iron-saturated LF (I-LF) and found the native form more potent. Finally, we tested the effects by bovine LF (bLF) in the same system and found the latter more potent than the human isoform in inducing cell growth and lactase expression. These results suggest that LF directly induces enterocyte growth and proliferation, depending on its concentration, thereby regulating the earlyx postnatal intestinal development. bLF could be added to infant formula as a growth factor in selected intestinal diseases.

Aminiotic Fluid and Intrauterine Growth Restriction in a Gastroschisis Fetal Rat Model

Fetuses with digestive anomalies such as gastroschisis may present intrauterine growth restriction (IUGR) and shortened intestines.

OBJECTIVE

The aim of this study was to assess the influence caused by amniotic fluid (AF) in intestinal length and somatic growth in an experimental gastroschisis fetal model at two distinct gestational ages.

MATERIAL AND METHOD

Fetal rats were operated according to Correia-Pinto on 2 different days of gestation: day 18.5 (group I) and day 19.5 (group II). Each group was divided into three sub-groups: fetuses with gastroschisis (G), control (C) and sham(S). Body measurements and histological analysis were done.

RESULT

Body measurement analysis showed: average body weight (g) in group I was G = 5.32, C = 5.68, S = 5.86; group II was G = 5.32, C = 5.80, S = 5.66. Average intestine weight (g) in group I was G = 0.283, C = 0.238, S = 0.231; group II was G = 0.272, C = 0.231, S = 0.233. Average intestine length (mm) in group I was G = 125, C = 216, S = 209; group II was G = 148, C = 226, S = 226. Histological analysis showed a decrease in the number and size of the intestinal microvillae and a light edema of serosa.

CONCLUSION

Gastroschisis had a direct correlation with IUGR and the time of exposure of the fetuses to AF had no influence on body weight in gastroschisis fetuses but did interfere with intestinal length.

The development of jejunum and ileum during the fetal period

OBJECTIVE

In our study, the morphologic structures of the jejunum and ileum sections of small intestine were investigated in human fetuses during the fetal period.

MATERIALS AND METHODS

The study was realised on 131 human fetuses (male: 69; female: 62) with ages between 10 and 40 weeks, which have got no external pathology and anomalies. The external sizes of fetuses were measured, and then the structures in the abdominal cavity were determined by the abdominal dissection. The localization of jejunum and ileum, duodenojejunal flexure and ileal orifice points, the measurements of macroscopic diameters, types of the mass of jejunum and ileum and the localization according to the abdominal regions of the mass of jejunum and ileum were determined. Also, the samples of the jejunum and ileum were examined both macroscopically and microscopically. The thickness of tunica serosa, tunica muscularis and tunica mucosa was determined under the light microscope.

RESULTS

According to the sexes, gestational ages and groups, the averages and the standard deviations of the all parameters were determined. The correlations between the parameters were determined. The percentage of parameters was compared according to sex and among groups. No differences were found in parameters between sexes (p<0.05). The macroscopic parameters were increased according to the gestational age. The thickness of tunica serosa did not change according to the gestational age.

CONCLUSION

It is thought that the data we have will help the evaluation of jejunum and ileum in intrauterine period; we also believe that the data in our study may help in the diagnosis and treatment of anomalies and pathologies in fetal period that belongs to jejunum and ileum.

Influence of bacterial overgrowth and intestinal inflammation on duration of parenteral nutrition in children with short bowel syndrome

OBJECTIVES

Massive intestinal resection results in short bowel syndrome and necessitates prolonged parenteral feeding. The purpose of this work was to assess the impact of late complications of short bowel syndrome, including intestinal bacterial overgrowth and enterocolitis, on the duration of parenteral nutrition (PN) in comparison with factors evident in the neonatal period.

METHODS

Retrospective chart review.

RESULTS

Of 49 children, 42 were weaned from parenteral nutrition after a treatment course of 17 +/- 14 months. In these 42, postresection small intestinal length equaled 81 +/- 65 cm; 45% had an ileocecal valve. Small intestinal length in the seven children who were PN dependent was 31 +/- 30 cm (p < 0.05); none had an ileocecal valve (p < 0.05). Bacterial overgrowth occurred in all seven PN-dependent children and in 23 of 42 children eventually weaned from PN (p < 0.05). When bacterial overgrowth was identified before weaning (n = 12), the duration pf PN was 28 +/- 17 months, but when bacterial overgrowth was first identified only after weaning (n = 11), the duration of PN was 16 +/- 13 months (p < 0.05). Small intestinal inflammation correlated with bacterial overgrowth (r = 0.69). Those children with severe enteritis identified before weaning remained on the PN regimen for 36 +/- 15 months, in comparison with 21 +/- 14 months in those with mild enteritis and 13 +/- 11 months in those without inflammation (p < 0.02).

CONCLUSIONS

Although the length of small intestine remaining after resection is the best immediate predictor of final success in terminating PN in children with short bowel syndrome, PN is prolonged by bacterial overgrowth and associated enteritis in those who will ultimately be weaned.

Short bowel syndrome: metabolic and surgical management

The management of short bowel syndrome requires long-term nutritional support and monitoring, medication, and occasionally additional surgical procedures. Constant attention is required to ensure adequate adaptation of the gut. This article reviews the normal function of the small bowel, adaptation following resection, total parenteral and enteral nutrition, and the role of adjunctive surgical procedures in the management of short bowel syndrome.