Intestinal adaptation after small bowel resection in human infants

The Stem Cell Niche in Short Bowel Syndrome

In intestinal resection animal models of short bowel syndrome (SBS), the remaining epithelium mounts a robust adaptive response characterized by early stem cell expansion and increased crypt depth, villus height and nutrient absorption. In humans the adaptive response is critical for resumption of oral nutrition, yet it may be variable, and underlying mechanisms are much less well understood. Current knowledge relating to the role of stem and mesenchymal niche cells in the adaptive response in animal models and in human SBS are addressed in this review.

Cutoffs and Characteristics of Abnormal Bowel Dilatation in Pediatric Short Bowel Syndrome

OBJECTIVES

Although excessive intestinal dilatation associates with worsened outcomes in pediatric short bowel syndrome (SBS), little is known about the natural history and definition of pathological dilatation. We addressed fore-, mid-, and hind-gut dilatation in children with SBS, who had not undergone autologous intestinal reconstructive (AIR) surgery, in relation to controls.

METHODS

SBS children without history of AIR surgery (n = 59) and age-matched controls without any disclosed intestinal pathology (n = 140) were included. Maximum diameter of duodenum, small bowel (SB), and colon were measured in each intestinal contrast series during 2002 to 2020 and expressed as diameter ratio (DR) to L5 vertebrae height. Predictive ability of DR for weaning off parenteral nutrition (PN) was analyzed with Cox proportional hazards regression models using multiple cutoffs.

RESULTS

Duodenum (DDR), SB (SBDR), and colon (CDR) DR were 53%, 183%, and 23% higher in SBS patients compared to controls ( P < 0.01 for all). The maximal DDR and SBDR measured during follow-up is associated with current PN dependence and young age. DDR correlated with SBDR ( r = 0.586, P < 0.01). Patients with maximal DDR less than 1.5, which was also the 99th percentile for controls, were 2.5-fold more likely to wean off PN ( P = 0.005), whereas SBDR and CDR were not predictive for PN duration.

CONCLUSIONS

All segments of remaining bowel, especially SB, dilate above normal levels in children with SBS. In SBS children without AIR surgery, PN dependence and young age is associated with duodenal and small intestinal dilatation, while duodenal dilatation also predicted prolonged PN.

Muscle hypertrophy and neuroplasticity in the small bowel in short bowel syndrome

Short bowel syndrome (SBS) is a severe, life-threatening condition and one of the leading causes of intestinal failure in children. Here we were interested in changes in muscle layers and especially in the myenteric plexus of the enteric nervous system (ENS) of the small bowel in the context of intestinal adaptation. Twelve rats underwent a massive resection of the small intestine to induce SBS. Sham laparotomy without small bowel transection was performed in 10 rats. Two weeks after surgery, the remaining jejunum and ileum were harvested and studied. Samples of human small bowel were obtained from patients who underwent resection of small bowel segments due to a medical indication. Morphological changes in the muscle layers and the expression of nestin, a marker for neuronal plasticity, were studied. Following SBS, muscle tissue increases significantly in both parts of the small bowel, i.e., jejunum and ileum. The leading pathophysiological mechanism of these changes is hypertrophy. Additionally, we observed an increased nestin expression in the myenteric plexus in the remaining bowel with SBS. Our human data also showed that in patients with SBS, the proportion of stem cells in the myenteric plexus had risen by more than twofold. Our findings suggest that the ENS is tightly connected to changes in intestinal muscle layers and is critically involved in the process of intestinal adaptation to SBS.

Nutrition and Intestinal Rehabilitation of Children With Short Bowel Syndrome: A Position Paper of the ESPGHAN Committee on Nutrition. Part 1: From Intestinal Resection to Home Discharge

Short bowel syndrome (SBS) is the leading cause of intestinal failure (IF) in children. The mainstay of treatment for IF is parenteral nutrition (PN). The aim of this position paper is to review the available evidence on managing SBS and to provide practical guidance to clinicians dealing with this condition. All members of the Nutrition Committee of the European Society for Paediatric Gastroenterology Hepatology and Nutrition (ESPGHAN) contributed to this position paper. Some renowned experts in the field joined the team to guide with their experience. A systematic literature search was performed from 2005 to May 2021 using PubMed, MEDLINE, and Cochrane Database of Systematic Reviews. In the absence of evidence, recommendations reflect the expert opinion of the authors. Literature on SBS mainly consists of retrospective single-center experience, thus most of the current papers and recommendations are based on expert opinion. All recommendations were voted on by the expert panel and reached >90% agreement. The first part of this position paper focuses on the physiological mechanism of intestinal adaptation after surgical resection. It subsequently provides some clinical practice recommendations for the primary management of children with SBS from surgical resection until discharged home on PN.

Intestinal adaptation and rehabilitation

Massive intestinal resection is a regrettably necessary but life-saving intervention for progressive or fulminant necrotizing enterocolitis (NEC). However, the resultant short bowel syndrome (SBS) poses its own array of challenges and complications. Within hours of such an abrupt loss of intestinal length, the intestine begins to adapt. Our ability to understand this process of intestinal adaptation has proven critical in our ability to clinically treat the challenging problem of short bowel syndrome. This review first highlights key data relating to intestinal adaptation including structural and functional changes, biochemical regulation, and other factors affecting the magnitude of intestinal adaptation responses. We then focus on intestinal rehabilitation as it relates to strategies to enhance intestinal adaptation while meeting nutritional needs and preventing complications of parenteral nutrition.

An Overview of Short-Bowel Syndrome in Pediatric Patients: Focus on Clinical Management and Prevention of Complications

Short-bowel syndrome (SBS) in pediatric age is defined as a malabsorptive state, resulting from congenital malformations, significant small intestine surgical resection or disease-associated loss of absorption. SBS is the leading cause of intestinal failure in children and the underlying cause in 50% of patients on home parental nutrition. It is a life-altering and life-threatening disease due to the inability of the residual intestinal function to maintain nutritional homeostasis of protein, fluid, electrolyte or micronutrient without parenteral or enteral supplementation. The use of parenteral nutrition (PN) has improved medical care in SBS, decreasing mortality and improving the overall prognosis. However, the long-term use of PN is associated with the incidence of many complications, including liver disease and catheter-associated malfunction and bloodstream infections (CRBSIs). This manuscript is a narrative review of the current available evidence on the management of SBS in the pediatric population, focusing on prognostic factors and outcome. The literature review showed that in recent years, the standardization of management has demonstrated to improve the quality of life in these complex patients. Moreover, the development of knowledge in clinical practice has led to a reduction in mortality and morbidity. Diagnostic and therapeutic decisions should be made by a multidisciplinary team that includes neonatologists, pediatric surgeons, gastroenterologists, pediatricians, nutritionists and nurses. A significant improvement in prognosis can occur through the careful monitoring of nutritional status, avoiding dependence on PN and favoring an early introduction of enteral nutrition, and through the prevention, diagnosis and aggressive treatment of CRSBIs and SIBO. Multicenter initiatives, such as research consortium or data registries, are mandatory in order to personalize the management of these patients, improve their quality of life and reduce the cost of care.

Lactation from the inside out: Maternal homeorhetic gastrointestinal adaptations regulating energy and nutrient flow into milk production

Lactation invokes homeorhetic processes to ramp up and supply milk synthesis components to fulfil nutritional, immunological and microbiological requirements of developing offspring, overseen by complex neuroendocrine networks. The maternal gut meets these intense metabolic demands, supported by hyperphagia and rapid adjustments to process larger food quantities. Enteroplasticity describes an inherent ability of the gastrointestinal tract to harness metabolic and structural adaptations that increase nutrient absorption. Most shifts in response to increased demands are transitory and by secreting milk, the continuous energetic drain out of the maternal body avoids development of pathological metabolic diseases. Lactation has various positive benefits for long-term maternal health but many females do not lactate for long post pregnancy and younger women are increasingly pre-disposed to excessive body mass and/or metabolic complications prior to reproducing. Inadvertently invoking intestinal adaptations to harvest and store excess nutrients has negative health implications with increased risks for both mother and offspring.

Building gut from scratch - progress and update of intestinal tissue engineering

Short bowel syndrome (SBS), a condition defined by insufficient absorptive intestinal epithelium, is a rare disease, with an estimated prevalence up to 0.4 in 10,000 people. However, it has substantial morbidity and mortality for affected patients. The mainstay of treatment in SBS is supportive, in the form of intravenous parenteral nutrition, with the aim of achieving intestinal autonomy. The lack of a definitive curative therapy has led to attempts to harness innate developmental and regenerative mechanisms to engineer neo-intestine as an alternative approach to addressing this unmet clinical need. Exciting advances have been made in the field of intestinal tissue engineering (ITE) over the past decade, making a review in this field timely. In this Review, we discuss the latest advances in the components required to engineer intestinal grafts and summarize the progress of ITE. We also explore some key factors to consider and challenges to overcome when transitioning tissue-engineered intestine towards clinical translation, and provide the future outlook of ITE in therapeutic applications and beyond.

Dietary Alpha-Ketoglutarate Partially Abolishes Adverse Changes in the Small Intestine after Gastric Bypass Surgery in a Rat Model

Alpha-ketoglutarate (AKG) is one of the key metabolites that play a crucial role in cellular energy metabolism. Bariatric surgery is a life-saving procedure, but it carries many gastrointestinal side effects. The present study investigated the beneficial effects of dietary AKG on the structure, integrity, and absorption surface of the small intestine after bariatric surgery. Male 7-week-old Sprague Dowley rats underwent gastric bypass surgery, after which they received AKG, 0.2 g/kg body weight/day, administered in drinking water for 6 weeks. Changes in small intestinal morphology, including histomorphometric parameters of enteric plexuses, immunolocalization of claudin 3, MarvelD3, occludin and zonula ocludens 1 in the intestinal mucosa, and selected hormones, were evaluated. Proliferation, mucosal and submucosal thickness, number of intestinal villi and Paneth cells, and depth of crypts were increased; however, crypt activity, the absorption surface, the expression of claudin 3, MarvelD3, occludin and zonula ocludens 1 in the intestinal epithelium were decreased after gastric bypass surgery. Alpha-ketoglutarate supplementation partially improved intestinal structural parameters and epithelial integrity in rats undergoing this surgical procedure. Dietary AKG can abolish adverse functional changes in the intestinal mucosa, enteric nervous system, hormonal response, and maintenance of the intestinal barrier that occurred after gastric bypass surgery.

Enterohormone therapy for short bowel syndrome

PURPOSE OF REVIEW

Short bowel syndrome (SBS) patients are at risk to develop intestinal failure when the decreased absorption of macronutrients, water, and electrolytes necessitates parenteral support for survival. The adverse effects of SBS and parenteral support negatively affect the quality of life (QoL) of SBS-intestinal failure patients. However, spontaneous intestinal adaptation along with disease-modifying therapies allow reducing parenteral support, thereby improving QoL.

RECENT FINDINGS

During the first years following extensive surgery, spontaneous structural and functional intestinal changes take place which stimulate a more efficient nutrient and fluid absorption in the remaining bowel. Given their potential role in the ileal braking mechanism, enterohormones, such as glucagon-like peptide (GLP)-2, GLP-1, and peptide YY (PYY), promote an accelerated adaptation or hyperadaptation. While the exact role of GLP-1 and PYY in SBS is still being explored, GLP-2 analogs have clearly shown to be effective in improving outcome in SBS.

SUMMARY

Whereas spontaneous intestinal adaptation improves the nutritional status of SBS patients to a certain extent, GLP-2 analogs can further decrease parenteral support needs through hyperadaptation. There are, however, other promising candidates on the horizon that - alone or in combination - could possibly establish additional disease-modifying effects.

Alterations in Small Intestine and Liver Morphology, Immunolocalization of Leptin, Ghrelin and Nesfatin-1 as Well as Immunoexpression of Tight Junction Proteins in Intestinal Mucosa after Gastrectomy in Rat Model

The stomach is responsible for the processing of nutrients as well as for the secretion of various hormones which are involved in many activities throughout the gastrointestinal tract. Experimental adult male Wistar rats (n = 6) underwent a modified gastrectomy, while control rats (n = 6) were sham-operated. After six weeks, changes in small intestine (including histomorphometrical parameters of the enteric nervous plexuses) and liver morphology, immunolocalization of leptin, ghrelin and nesfatin-1 as well as proteins forming adherens and tight junctions (E-cadherin, zonula occludens-1, occludin, marvelD3) in intestinal mucosa were evaluated. A number of effects on small intestine morphology, enteric nervous system ganglia, hormones and proteins expression were found, showing intestinal enteroplasticity and neuroplasticity associated with changes in gastrointestinal tract condition. The functional changes in intestinal mucosa and the enteric nervous system could be responsible for the altered intestinal barrier and hormonal responses following gastrectomy. The results suggest that more complicated regulatory mechanisms than that of compensatory mucosal hypertrophy alone are involved.

Stem cell and niche regulation in human short bowel syndrome

Loss of functional small bowel surface area following surgical resection for disorders such as Crohn’s disease, intestinal ischemic injury, radiation enteritis, and in children, necrotizing enterocolitis, atresia, and gastroschisis, may result in short bowel syndrome, with attendant high morbidity, mortality, and health care costs in the United States. Following resection, the remaining small bowel epithelium mounts an adaptive response, resulting in increased crypt cell proliferation, increased villus height, increased crypt depth, and enhanced nutrient and electrolyte absorption. Although these morphologic and functional changes are well described in animal models, the adaptive response in humans is less well understood. Clinically the response is unpredictable and often inadequate. Here we address the hypotheses that human intestinal stem cell populations are expanded and that the stem cell niche is regulated following massive gut resection in short bowel syndrome (SBS). We use intestinal enteroid cultures from patients with SBS to show that the magnitude and phenotype of the adaptive stem cell response are both regulated by stromal niche cells, including intestinal subepithelial myofibroblasts, which are activated by intestinal resection to enhance epithelial stem and proliferative cell responses. Our data suggest that myofibroblast regulation of bone morphogenetic protein signaling pathways plays a role in the gut adaptive response after resection.

LGR5+ stem cells are expanded and BMP signaling regulates the stem cell niche in human short bowel syndrome.

Short Bowel Syndrome: A Paradigm for Intestinal Adaptation to Nutrition?

Short bowel syndrome (SBS) is a rare disease that results from extensive resection of the intestine. When the remaining absorption surface of the intestine cannot absorb enough macronutrients, micronutrients, and water, SBS results in intestinal failure (IF). Patients with SBS who suffer from IF require parenteral nutrition for survival, but long-term parenteral nutrition may lead to complications such as catheter sepsis and metabolic diseases. Spontaneous intestinal adaptation occurs weeks to months after resection, resulting in hyperplasia of the remnant gut, modification of gut hormone levels, dysbiosis, and hyperphagia. Oral nutrition and presence of the colon are two major positive drivers for this adaptation. This review aims to summarize the current knowledge of the mechanisms underlying spontaneous intestinal adaptation, particularly in response to modifications of luminal content, including nutrients. In the future, dietary manipulations could be used to treat SBS.

Intestinal plasticity in response to nutrition and gastrointestinal surgery

The plasticity of a material corresponds to its capacity to change its feature under the effect of an external action. Intestinal plasticity could be defined as the ability of the intestine to modify its size or thickness and intestinal cells to modulate their absorption and secretion functions in response to external or internal cues/signals. This review will focus on intestinal adaptation mechanisms in response to diet and nutritional status. These physiological mechanisms allow a fine and rapid adaptation of the gut to promote absorption of ingested food, but they can also lead to obesity in response to overnutrition. This plasticity could thus become a therapeutic target to treat not only undernutrition but also obesity. How the intestine adapts in response to 2 types of surgical remodeling of the digestive tract-extensive bowel resection leading to intestinal failure and surgical treatment of pathological obesity (ie, bariatric surgeries)-will also be reviewed.

Parenteral Nutrition-Dependent Children With Short-Bowel Syndrome Lack Duodenal-Adaptive Hyperplasia but Show Molecular Signs of Altered Mucosal Function

BACKGROUND

Although adaptive mucosal growth of the remaining small intestine is an essential compensatory mechanism to bowel resection in experimental short-bowel syndrome (SBS), only scarce clinical data are available. We studied structural and molecular mechanisms of intestinal adaptation in children with SBS.

METHODS

Fourteen patients, who had been dependent on parenteral nutrition (PN) since neonatal period for a median (interquartile range)1.4 (0.7-6.5) years, were studied at the age of 1.5 (1.0-6.5) years. Median length of remaining small bowel was 33 (12-60) cm, and 6 patients had their ileocecal valve preserved. Six children without gastrointestinal disorders served as age-matched and gender-matched controls. All patients underwent duodenal biopsies. Mucosal microarchitecture, proliferation, apoptosis, inflammation, and epithelial-barrier function were addressed using histology, immunohistochemistry, and quantitative real-time polymerase chain reaction.

RESULTS

Villus height, crypt depth, enterocyte proliferation, and apoptosis were similar in patients and matched controls. Messenger RNA (mRNA) expression of numerous genes regulating gut epithelial-barrier function (TGFB2, CAV1, CLDN1, MUC2, and NLRC4) was significantly altered. Of various nutrient transporters studied, only expression of SLC2A1 encoding facilitative glucose transporter GLUT1 was increased among patients, whereas RNA expression of genes encoding sodium-dependent glucose, sterol, fatty-acid, and peptide transport remained unchanged.

CONCLUSION

Duodenal mucosal hyperplasia has a limited role in mediating physiological adaptation following intestinal resection among PN-dependent children with SBS. Further clinical studies addressing functional significance of the observed alterations in mucosal RNA expression are warranted.

Short Bowel Syndrome

Purpose of Review

Short gut syndrome is life-altering and life-threatening disease resulting most often from massive small bowel resection. Recent advances in understanding of the perturbed physiology in these patients have translated into improved care and outcomes. This paper seeks to review the advances of care in SBS patients.

Recent Findings

Anatomic considerations still predominate the early care of SBS patients, including aggressive preservation of bowel and documentation of remnant bowel length and quality. Intestinal adaptation is the process by which remnant bowel changes to fit the physiologic needs of the patient. Grossly, the bowel dilates and elongates to increase intestinal weight and protein content. Architectural changes are noted, such as villus lengthening and deepening of crypts. In addition, gene expression changes occur that function to maximize nutrient uptake and fluid preservation. Management is aimed at understanding these physiologic changes and augmenting them whenever possible in an effort to gain enteral autonomy. Complication mitigation is key, including avoidance of catheter complications, bloodstream infections, cholestasis, and nutrient deficiencies.

Summary

Multidisciplinary teams working together towards intestinal rehabilitation have shown improved outcomes. Today's practioner needs a current understanding of the ever-evolving care of these patients in order to promote enteral autonomy, recognize complications, and counsel patients and families appropriately.

The Effects of Gestational Psychological Stress on Neonatal Mouse Intestinal Development

BACKGROUND

Psychological stress during pregnancy has been shown to cause subsequent harm to the fetus and newborn. Many studies focus on neurodevelopmental outcomes, but little is known about the effect of gestational stress on intestinal immunity and development. The purpose of this study was to determine the effect of psychological stress during pregnancy on intestinal architecture and growth in newborns.

METHODS

Eight-week-old C57BL6 littermates underwent timed breeding. Pregnant dams were subjected to 1 h of daily psychological stress by using a well-established restraint model during days E7-E14. The distal ileum of 2-wk-old offspring of stressed mothers and nonstressed controls was harvested for histologic analysis. Slides were blinded to measure villus height and crypt depth and surface area. Serum was obtained to measure serum corticosterone levels. An explant model was used to measure corticosterone on the intestinal stem cell marker Leucine-rich repeat-containing G-protein coupled receptor 5 (LGR5) and growth factors epidermal growth factor receptor and insulin-like growth factor-1.

RESULTS

The villus height, crypt depth, and surface area were significantly decreased in newborn exposed to stress during gestation. In addition, corticosterone levels were elevated in 2-wk-old mice exposed to stress. Real-time polymerase chain reaction revealed that explants exposed to corticosterone had a decrease in LGR5 compared with controls and an increase in epidermal growth factor receptor.

CONCLUSIONS

Here, we establish that neonatal mice from mothers that were subjected to psychological stress during pregnancy have significantly shorter villi and crypts compared with controls. In addition, pups from stressed mothers have decreased expression levels of the intestinal stem cell marker LGR5. These findings will aid in determining the effect of gestational psychological stress on intestinal development and stem cell plasticity.

Are there differences in the growth adaptation processes of growing and mature organism models of short bowel syndrome?

OBJECTIVES

The purpose of this study was to present an experimental model of short bowel syndrome (SBS) in weaning rats and to compare the adaptative mechanisms of the remaining bowel in weaning rats and adult animals by means of morphometric, histologic and molecular methods.

METHODS

Twenty-four weaning rats were divided into 3 groups of 8 animals, one control group and two short bowel groups (euthanasia after 4 and 21 days), and were compared with similar adult groups. Morphometric evaluations of the animals and histopathological and molecular studies of the remaining bowel were performed.

RESULTS

The weight of young rats increased after enterectomy, whereas that of adult rats decreased after enterectomy (p<0.0001). The ratio of intestinal length/body weight was significantly higher in weaning rats than in adults (p<0.002), showing that intestinal growth was more intense in weaning rats. Intestinal resection promoted increased thickness of the small bowel lamina propria (p=0.001) and reduced thickness of the colon lamina propria (p=0.04) in weaning rats relative to those in adults. In addition, intestinal resection promoted increased expression of the Bcl-xl gene (antiapoptotic) in adult animals compared with that in weaning rats (p=0.001).

CONCLUSION

Morphometric, histological and molecular differences were shown in the adaptation processes of growing and mature organisms.

Transverse flap duodenoplasty (TFD): a new technique in autologous bowel reconstructive surgery

BACKGROUND

Bowel dilatation is a common adaptive mechanism after intestinal resection. The symptomatic dilated dysmotile duodenum is difficult to manage, since conventional bowel tailoring and lengthening techniques are potentially hazardous because of the anatomy of the duodenal blood supply, the proximity to the pancreas, and the risk of injury to the common bile duct.

METHODS

A 2-month-old child with short bowel and a symptomatic massively dilated duodenum was treated with a Transverse Flap Duodenoplasty (TFD). The duodenum was opened longitudinally along its antimesenteric border preserving an intact strip of tissue overlying the pancreatic head. Three full thickness vascularized pedicle flaps were cut on both the anterior and posterior walls and were spirally rotated and sutured to create a uniform propulsive duodenum without diverticulae.

RESULTS

Healing was complicated by a soft anastomotic duodeno-ileal stenosis that resolved after three elective balloon dilatations. Oral feeding established rapidly. The child is growing, does not vomit, and passes 1-2 semiformed motions daily.

CONCLUSIONS

TFD is a safe and versatile technique that preserves all duodenal absorptive mucosa and that removes any risk to the pancreas, bile duct, and ampulla of Vater. Our experience, although limited, has been encouraging and leads us to suggest TFD for the management of the difficult symptomatic dysmotile dilated duodenum.

Host-Gut Microbiota Crosstalk in Intestinal Adaptation

Short-bowel syndrome represents the most common cause of intestinal failure and occurs when the remaining intestine cannot support fluid and nutrient needs to sustain adequate physiology and development without the use of supplemental parenteral nutrition. After intestinal loss or damage, the remnant bowel undergoes multifactorial compensatory processes, termed adaptation, which are largely driven by intraluminal nutrient exposure. Previous studies have provided insight into the biological processes and mediators after resection, however, there still remains a gap in the knowledge of more comprehensive mechanisms that drive the adaptive responses in these patients. Recent data support the microbiota as a key mediator of gut homeostasis and a potential driver of metabolism and immunomodulation after intestinal loss. In this review, we summarize the emerging ideas related to host-microbiota interactions in the intestinal adaptation processes.

Small Bowel Dilatation Predicts Prolonged Parenteral Nutrition and Decreased Survival in Pediatric Short Bowel Syndrome

OBJECTIVE

To analyze risk factors and prognostic significance of small bowel (SB) dilatation in children with short bowel syndrome (SBS).

BACKGROUND

In SBS, the remaining SB may dilate as part of intestinal adaptation. The impact of dilatation on parenteral nutrition (PN) dependence and survival has not been studied systematically.

METHODS

SB diameter of SBS children (n = 61) was measured in contrast SB series (n = 169, median age 0.94, range 0.32-2.7 years) during 2002 to 2015, and expressed as millimeters (SB width) and as ratio to L5 vertebra height (SB diameter ratio). Linear regression was used to examine risk factors for dilatation. PN weaning and survival were analyzed with Cox proportional hazards regression.

RESULTS

Maximal SB diameter ratio during follow-up was predicted by PN dependence and SB atresia, while maximal absolute SB width by birth weight, age, PN duration, and remaining bowel length. Weaning off PN was 14-fold more likely in patients with maximal SB diameter ratio <2.00 compared with >3.00 (P = 0.005), and 5.4-fold more likely when maximal SB width was <20 mm compared with >30 mm (P = 0.023). After adjustment for age, remaining SB length, and the presence of ileocecal valve, both estimates of maximal SB dilatation remained significant independent predictors for weaning off PN. When all measurements were included, the cumulative survival was worse if SB diameter ratio exceeded 2.00 (P = 0.002-0.042).

CONCLUSIONS

SB dilatation predicts prolonged PN duration and decreased survival in SBS children. Measurement of maximal SB diameter standardized to L5 vertebra height may be a valuable objective tool for patient follow-up and assessment of prognosis.

Marked stem/progenitor cell expansion occurs early after murine ileostomy: a new model

BACKGROUND

Improving treatment for short bowel syndrome requires a better understanding of how intestinal adaptation is affected by factors like mechanoluminal stimulation. We hypothesized that in mice, luminal diversion via an ileostomy would drive adaptive changes similar to those seen in human intestine after diversion while offering the opportunity to study the immediate events after resection that precede intestinal adaptation.

MATERIALS AND METHODS

With Institutional Animal Care and Use Committee approval, a distal ileostomy with a long distal Hartman's was created in 9- to 14-week-old C57/B6 mice (n = 8). Control mice only had a midline laparotomy without stoma formation (n = 5). A rim of tissue from the proximal stoma was resected as a historical control for the proximal segment. Postoperatively, mice received a high-protein liquid diet and water ad libitum. On day 3, tissue from both the proximal and distal limbs were collected for histologic and RNA analysis. Morphometric measures, immunofluorescent antigen detection, and RNA expression were compared with Student paired t-tests with a P value < 0.05 considered significant.

RESULTS

At 3 d, survival for mice with an ileostomy was 87% and average weight loss was 12.5% of initial weight compared to 6.05% for control mice. Compared to the distal limb, the proximal limb in mice with an ileostomy demonstrated significantly taller villi with deeper and wider crypts. The proximal limb also had decreased expression of intestinal stem cell markers lgr5, bmi1, sox9, and ascl2. Fewer goblet and enteroendocrine cells per hemivillus were also noted in the proximal limb. In control mice, none of these measures were significant between proximal and distal ileum except for villus height.

CONCLUSIONS

This new murine ileostomy model allows study of intestinal adaptation without intestinal anastomosis, which can be technically challenging and morbid.

Risk factors and outcomes of tapering surgery for small intestinal dilatation in pediatric short bowel syndrome

BACKGROUND

In remains unclear why in some short bowel syndrome (SBS) patients, the remaining small bowel (SB) dilates excessively leading to requirement of tapering surgery.

METHODS

Among SBS children, we retrospectively analyzed risk factors for tapering surgery with logistic regression and compared the outcome of operated patients (n=16) to those managed conservatively (n=44) with Cox proportional hazards regression.

RESULTS

SBS was caused by necrotizing enterocolitis (NEC) (n=31), SB atresia (SBA) (n=13), midgut volvulus (n=12), or gastroschisis (n=4). Patients with spontaneous symptomatic SB dilatation unable to wean parenteral nutrition (PN) underwent tapering surgery at median age of 1.04 (interquartile range 0.70-3.27) years. Missing ICV was related to an 8-fold (p=0.003) increased risk while SBA diagnosis was related to a 13-fold risk of tapering surgery (p<0.001). Increasing SB length and NEC diagnosis were protective of tapering (p=0.027-0.004). Of operated patients, 75% reached enteral autonomy during follow-up and their postoperative adjusted PN weaning rate was similar to nonoperated children (p=0.842).

CONCLUSION

SBS children with short remaining SB, missing ICV, and SBA etiology are more likely while NEC patients are less likely than others to necessitate tapering surgery. Postoperative PN weaning rates were comparable to patients who initially had more favorable intestinal anatomy and adapted without surgery.

Prolonged Absence of Mechanoluminal Stimulation in Human Intestine Alters the Transcriptome and Intestinal Stem Cell Niche

BACKGROUND & AIMS

For patients with short-bowel syndrome, intestinal adaptation is required to achieve enteral independence. Although adaptation has been studied extensively in animal models, little is known about this process in human intestine. We hypothesized that analysis of matched specimens with and without luminal flow could identify new potential therapeutic pathways.

METHODS

Fifteen paired human ileum samples were collected from children aged 2-20 months during ileostomy-reversal surgery after short-segment intestinal resection and diversion. The segment exposed to enteral feeding was denoted as fed, and the diverted segment was labeled as unfed. Morphometrics and cell differentiation were compared histologically. RNA Sequencing and Gene Ontology Enrichment Analysis identified over-represented and under-represented pathways. Immunofluorescence staining and Western blot evaluated proteins of interest. Paired data were compared with 1-tailed Wilcoxon rank-sum tests with a P value less than .05 considered significant.

RESULTS

Unfed ileum contained shorter villi, shallower crypts, and fewer Paneth cells. Genes up-regulated by the absence of mechanoluminal stimulation were involved in digestion, metabolism, and transport. Messenger RNA expression of LGR5 was significantly higher in unfed intestine, accompanied by increased levels of phosphorylated signal transducer and activator of transcription 3 protein, and CCND1 and C-MYC messenger RNA. However, decreased proliferation and fewer LGR5+, OLFM4+, and SOX9+ intestinal stem cells (ISCs) were observed in unfed ileum.

CONCLUSIONS

Even with sufficient systemic caloric intake, human ileum responds to the chronic absence of mechanoluminal stimulation by up-regulating brush-border enzymes, transporters, structural genes, and ISC genes LGR5 and ASCL2. These data suggest that unfed intestine is primed to replenish the ISC population upon re-introduction of enteral feeding. Therefore, the elucidation of pathways involved in these processes may provide therapeutic targets for patients with intestinal failure. RNA sequencing data are available at Gene Expression Omnibus series GSE82147.

Short bowel syndrome results in increased gene expression associated with proliferation, inflammation, bile acid synthesis and immune system activation: RNA sequencing a zebrafish SBS model

Background

Much of the morbidity associated with short bowel syndrome (SBS) is attributed to effects of decreased enteral nutrition and administration of total parenteral nutrition (TPN). We hypothesized that acute SBS alone has significant effects on gene expression beyond epithelial proliferation, and tested this in a zebrafish SBS model.

Methods

In a model of SBS in zebrafish (laparotomy, proximal stoma, distal ligation, n = 29) or sham (laparotomy alone, n = 28) surgery, RNA-Seq was performed after 2 weeks. The proximal intestine was harvested and RNA isolated. The three samples from each group with the highest amount of RNA were spiked with external RNA controls consortium (ERCC) controls, sequenced and aligned to reference genome with gene ontology (GO) enrichment analysis performed. Gene expression of ctnnb1, ccnb1, ccnd1, cyp7a1a, dkk3, ifng1-2, igf2a, il1b, lef1, nos2b, saa1, stat3, tnfa and wnt5a were confirmed to be elevated in SBS by RT-qPCR.

Results

RNA-seq analysis identified 1346 significantly upregulated genes and 678 significantly downregulated genes in SBS zebrafish intestine compared to sham with Ingenuity analysis. The upregulated genes were involved in cell proliferation, acute phase response signaling, innate and adaptive immunity, bile acid regulation, production of nitric oxide and reactive oxygen species, cellular barrier and coagulation. The downregulated genes were involved in folate synthesis, gluconeogenesis, glycogenolysis, fatty-acid oxidation and activation and drug and steroid metabolism. RT-qPCR confirmed gene expression differences from RNA-Sequencing.

Conclusion

Changes of gene expression after 2 weeks of SBS indicate complex and extensive alterations of multiple pathways, some previously implicated as effects of TPN. The systemic sequelae of SBS alone are significant and indicate multiple targets for investigating future therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3433-4) contains supplementary material, which is available to authorized users.

Small Bowel Diameter in Short Bowel Syndrome as a Predictive Factor for Achieving Enteral Autonomy

Children with short bowel syndrome commonly have dilated small bowel. We found that the extent of dilation was associated with bowel length and that both were related to achieving enteral autonomy.

Management of Crohn's Disease in the New Era of Gut Rehabilitation and Intestinal Transplantation

Despite recent therapeutic advances, patients with Crohn's disease (CD) continue to experience high recurrence with cumulative structural damage and ultimate loss of nutritional autonomy. With short bowel syndrome, strictures, and enteric fistulae being the underlying pathology, CD is the second common indication for home parenteral nutrition (HPN). With development of intestinal failure, nutritional management including HPN is required as a rescue therapy. Unfortunately, some patients do not escape the HPN-associated complications. Therefore, the concept of gut rehabilitation has evolved as part of the algorithmic management of these patients, with transplantation being the ultimate life-saving therapy. With type 2 intestinal failure, comprehensive rehabilitative measures including nutritional care, pharmacologic manipulation, autologous reconstruction, and bowel lengthening is often successful, particularly in patients with quiescent disease. With type 3 intestinal failure, transplantation is the only life-saving treatment for patients with HPN failure and intractable disease. With CD being the second common indication for transplantation in adults, survival outcome continues to improve because of surgical innovation, novel immunosuppression, and better postoperative care. Despite being a rescue therapy, the procedure has achieved survival rates similar to other solid organs, and comparable to those who continue to receive HPN therapy. With similar technical, immunologic, and infectious complications, survival is similar in the CD and non-CD recipients. Full nutritional autonomy is achievable in most survivors with better quality of life and long-term cost-effectiveness. CD recurrence is rare with no impact on graft function. Further progress is anticipated with new insights into the pathogenesis of CD and mechanisms of transplant tolerance.

The Pathogenesis of Resection-Associated Intestinal Adaptation

After massive small-bowel resection, the remnant bowel compensates by a process termed adaptation. Adaptation is characterized by villus elongation and crypt deepening, which increases the capacity for absorption and digestion per unit length. The mechanisms/mediators of this important response are multiple. The purpose of this review is to highlight the major basic contributions in elucidating a more comprehensive understanding of this process.

Intestinal Failure: Adaptation, Rehabilitation, and Transplantation

Intestinal failure (IF) is a state in which the nutritional demands are not met by the gastrointestinal absorptive surface. A majority of IF cases are associated with short-bowel syndrome, which is a result of malabsorption after significant intestinal resection for numerous reasons, some of which include Crohn's disease, vascular thrombosis, and radiation enteritis. IF can also be caused by obstruction, dysmotility, and congenital defects. Recognition and management of IF can be challenging, given the complex nature of this condition. This review discusses the management of IF with a focus on intestinal rehabilitation, parenteral nutrition, and transplantation.

The human milk oligosaccharide 2'-fucosyllactose augments the adaptive response to extensive intestinal

Intestinal resection resulting in short bowel syndrome (SBS) carries a heavy burden of long-term morbidity, mortality, and cost of care, which can be attenuated with strategies that improve intestinal adaptation. SBS infants fed human milk, compared with formula, have more rapid intestinal adaptation. We tested the hypothesis that the major noncaloric human milk oligosaccharide 2'-fucosyllactose (2'-FL) contributes to the adaptive response after intestinal resection. Using a previously described murine model of intestinal adaptation, we demonstrated increased weight gain from 21 to 56 days (P < 0.001) and crypt depth at 56 days (P < 0.0095) with 2'-FL supplementation after ileocecal resection. Furthermore, 2'-FL increased small bowel luminal content microbial alpha diversity following resection (P < 0.005) and stimulated a bloom in organisms of the genus Parabacteroides (log2-fold = 4.1, P = 0.035). Finally, transcriptional analysis of the intestine revealed enriched ontologies and pathways related to antimicrobial peptides, metabolism, and energy processing. We conclude that 2'-FL supplementation following ileocecal resection increases weight gain, energy availability through microbial community modulation, and histological changes consistent with improved adaptation.

Generation of tissue-engineered small intestine using embryonic stem cell-derived human intestinal organoids

Short bowel syndrome (SBS) is characterized by poor nutrient absorption due to a deficit of healthy intestine. Current treatment practices rely on providing supportive medical therapy with parenteral nutrition; while life saving, such interventions are not curative and are still associated with significant co-morbidities. As approaches to lengthen remaining intestinal tissue have been met with only limited success and intestinal transplants have poor survival outcomes, new approaches to treating SBS are necessary. Human intestine derived from embryonic stem cells (hESCs) or induced pluripotent stem cells (iPSCs), called human intestinal organoids (HIOs), have the potential to offer a personalized and scalable source of intestine for regenerative therapies. However, given that HIOs are small three-dimensional structures grown in vitro, methods to generate usable HIO-derived constructs are needed. We investigated the ability of hESCs or HIOs to populate acellular porcine intestinal matrices and artificial polyglycolic/poly L lactic acid (PGA/PLLA) scaffolds, and examined the ability of matrix/scaffolds to thrive when transplanted in vivo. Our results demonstrate that the acellular matrix alone is not sufficient to instruct hESC differentiation towards an endodermal or intestinal fate. We observed that while HIOs reseed acellular porcine matrices in vitro, the HIO-reseeded matrices do not thrive when transplanted in vivo. In contrast, HIO-seeded PGA/PLLA scaffolds thrive in vivo and develop into tissue that looks nearly identical to adult human intestinal tissue. Our results suggest that HIO-seeded PGA/PLLA scaffolds are a promising avenue for developing the mucosal component of tissue engineered human small intestine, which need to be explored further to develop them into fully functional tissue.

Summary: HIO-seeded PGA/PLLA scaffolds thrive in vivo and develop into tissue that looks nearly identical to adult human intestinal tissue. These scaffolds appear to be suitable for further tissue engineering approaches to develop functional intestine.

Intestinal adaptation in short bowel syndrome: A case report

Short bowel syndrome is a clinical entity that includes loss of energy, fluid, electrolytes or micronutrient balance because of inadequate functional intestinal length. This case report demonstrates the case of a woman who compensated for short bowel syndrome through intestinal adaptation, which is a complex process worthy of further investigation for the avoidance of dependence on total parenteral nutrition and of intestinal transplantation in such patients.

The effect of impaired angiogenesis on intestinal function following massive small bowel resection

PURPOSE

Intestinal adaptation involves villus lengthening, crypt deepening, and increased capillary density following small bowel resection (SBR). Mice lacking the proangiogenic chemokine CXCL5 have normal structural adaptation but impaired angiogenesis. This work evaluates the impact of incomplete adaptive angiogenesis on the functional capacity of the intestine after SBR.

METHODS

CXCL5 knockout (KO) and C57BL/6 wild-type (WT) mice underwent 50% SBR. Magnetic resonance imaging measured weekly body composition. Intestinal absorptive capacity was evaluated through fecal fat analysis. Gene expression profiles for select macronutrient transporters were measured via RT-PCR. Postoperative crypt and villus measurements were assessed for structural adaptation. Submucosal capillary density was measured through CD31 immunohistochemistry.

RESULTS

Comparable postoperative weight gain occurred initially. Diminished weight gain, impaired fat absorption, and elevated steatorrhea occurred in KO mice after instituting high-fat diet. Greater postoperative upregulation of ABCA1 fat transporter occurred in WT mice, while PEPT1 protein transporter was significantly downregulated in KO mice. KO mice had impaired angiogenesis but intact structural adaptation.

CONCLUSION

After SBR, KO mice display an inefficient intestinal absorption profile with perturbed macronutrient transporter expression, impaired fat absorption, and slower postoperative weight gain. In addition to longer villi and deeper crypts, an intact angiogenic response may be required to achieve functional adaptation to SBR.

Autologous intestinal reconstruction surgery as part of comprehensive management of intestinal failure

Pediatric intestinal failure (IF) remains to be associated with significant morbidity and mortality, the most frequent underlying etiologies being short bowel syndrome (SBS), and primary motility disorders. Management aims to assure growth and development, while preventing complications and facilitating weaning off parenteral support (PS) by fully utilizing adaptation potential of the remaining gut. Probability of survival and weaning off PS is improved by coordinated multidisciplinary intestinal rehabilitation combining individualized physiological enteral and parenteral nutrition (PN), meticulous central line care and medical management with carefully planned surgical care. Increasing evidence suggests that autologous intestinal reconstruction (AIR) surgery is effective treatment for selected short bowel patients. Bowel lengthening procedures normalize pathological adaptation-associated short bowel dilatation with potential to support intestinal absorption and liver function by various mechanisms. Although reversed small intestinal segment, designed to prolong accelerated intestinal transit, improves absorption in adult SBS, its feasibility in children remains unclear. Controlled bowel obstruction to induce dilatation followed by bowel lengthening aims to gain extra length in patients with the shortest duodenojejunal remnant. Reduced PS requirement limits the extent of complications, improving prognosis and quality of life. The great majority of children with SBS can be weaned from PS while prognosis of intractable primary motility disorders remains poor without intestinal transplantation, which serves as a salvage therapy for life-threatening complications such as liver failure, central vein thrombosis or recurrent bloodstream infections.

The concept of gut rehabilitation and the future of visceral transplantation

In the 1990s, the introduction of visceral transplantation fuelled interest in other innovative therapeutic modalities for gut rehabilitation. Ethanol lock and omega-3 lipid formulations were introduced to reduce the risks associated with total parenteral nutrition (TPN). Autologous surgical reconstruction and bowel lengthening have been increasingly utilized for patients with complex abdominal pathology and short-bowel syndrome. Glucagon-like peptide 2 analogue, along with growth hormone, are available to enhance gut adaptation and achieve nutritional autonomy. Intestinal transplantation continues to be limited to a rescue therapy for patients with TPN failure. Nonetheless, survival outcomes have substantially improved with advances in surgical techniques, immunosuppressive strategies and postoperative management. Furthermore, both nutritional autonomy and quality of life can be restored for more than two decades in most survivors, with social support and inclusion of the liver being favourable predictors of long-term outcome. One of the current challenges is the discovery of biomarkers to diagnose early rejection and further improve liver-free allograft survival. Currently, chronic rejection with persistence of preformed and development of de novo donor-specific antibodies is a major barrier to long-term graft function; this issue might be overcome with innovative immunological and tolerogenic strategies. This Review discusses advances in the field of gut rehabilitation, including intestinal transplantation, and highlights future challenges. With the growing interest in individualized medicine and the value of health care, a novel management algorithm is proposed to optimize patient care through an integrated multidisciplinary team approach.

The effect of diet on the intestinal epigenome

The colorectal mucosal epithelium is composed of rapidly proliferating crypt cells derived by clonal expansion from stem cells. The aging human colorectal mucosa develops aberrant patterns of DNA methylation that may contribute to its increasing vulnerability to cancer. Various types of evidence suggest that age-dependent loss of global methylation, together with hypermethylation of CpG islands associated with cancer-related genes, may be influenced by nutritional and metabolic factors. Folates are essential for the maintenance of normal DNA methylation, and folate metabolism is known to modify epigenetic mechanisms under experimental conditions. Human intervention trials and cross-sectional studies suggest a role for folates and other nutritional and metabolic factors as determinants of colorectal mucosal DNA methylation. Future studies should focus on the possibility that folic acid fortification may exert unforeseen effects on the human gastrointestinal epigenome. Naturally occurring DNA methyltransferase inhibitors in plant foods may be useful for the manipulation of epigenetic profiles in health and disease.

The pharmacologic treatment of short bowel syndrome: new tricks and novel agents

Short bowel syndrome (SBS) is a manifestation of massive resection of the intestines resulting in severe fluid, electrolyte, and vitamin/mineral deficiencies. Diet and parenteral nutrition play a large role in the management of SBS; however, pharmacologic options are becoming more readily available. These pharmacologic agents focus on reducing secretions and stimulating intestinal adaptation. The choice of medication is highly dependent on the patient's symptoms, remaining anatomy, and risk versus benefit profile for each agent. This article focuses on common and novel pharmacologic medications used in SBS, including expert advice on their indications and use.

Animal models of gastrointestinal and liver diseases. Animal models of infant short bowel syndrome: translational relevance and challenges

Intestinal failure (IF), due to short bowel syndrome (SBS), results from surgical resection of a major portion of the intestine, leading to reduced nutrient absorption and need for parenteral nutrition (PN). The incidence is highest in infants and relates to preterm birth, necrotizing enterocolitis, atresia, gastroschisis, volvulus, and aganglionosis. Patient outcomes have improved, but there is a need to develop new therapies for SBS and to understand intestinal adaptation after different diseases, resection types, and nutritional and pharmacological interventions. Animal studies are needed to carefully evaluate the cellular mechanisms, safety, and translational relevance of new procedures. Distal intestinal resection, without a functioning colon, results in the most severe complications and adaptation may depend on the age at resection (preterm, term, young, adult). Clinically relevant therapies have recently been suggested from studies in preterm and term PN-dependent SBS piglets, with or without a functional colon. Studies in rats and mice have specifically addressed the fundamental physiological processes underlying adaptation at the cellular level, such as regulation of mucosal proliferation, apoptosis, transport, and digestive enzyme expression, and easily allow exogenous or genetic manipulation of growth factors and their receptors (e.g., glucagon-like peptide 2, growth hormone, insulin-like growth factor 1, epidermal growth factor, keratinocyte growth factor). The greater size of rats, and especially young pigs, is an advantage for testing surgical procedures and nutritional interventions (e.g., PN, milk diets, long-/short-chain lipids, pre- and probiotics). Conversely, newborn pigs (preterm or term) and weanling rats provide better insights into the developmental aspects of treatment for SBS in infants owing to their immature intestines. The review shows that a balance among practical, economical, experimental, and ethical constraints will determine the choice of SBS model for each clinical or basic research question.

Tis7 deletion reduces survival and induces intestinal anastomotic inflammation and obstruction in high-fat diet-fed mice with short bowel syndrome

Effective therapies are limited for patients with parenteral nutrition-dependent short bowel syndrome. We previously showed that intestinal expression of the transcriptional coregulator tetradecanoyl phorbol acetate-induced sequence 7 (tis7) is markedly increased during the adaptive response following massive small bowel resection and tis7 plays a role in normal gut lipid metabolism. Here, we further explore the functional implications of tis7 deletion in intestinal lipid metabolism and the adaptive response following small bowel resection. Intestinal tis7 transgenic (tis7(tg)), tis7(-/-), and wild-type (WT) littermates were subjected to 50% small bowel resection. Mice were fed a control or a high-saturated-fat (42% energy) diet for 21 days. Survival, body weight recovery, lipid absorption, mucosal lipid analysis, and the morphometric adaptive response were analyzed. Quantitative real-time PCR was performed to identify tis7 downstream gene targets. Postresection survival was markedly reduced in high-fat, but not control, diet-fed tis7(-/-) mice. Decreased survival was associated with anastomotic inflammation and intestinal obstruction postresection. High-fat, but not control, diet-fed tis7(-/-) mice had increased intestinal IL-6 expression. Intestinal lipid trafficking was altered in tis7(-/-) compared with WT mice postresection. In contrast, high-fat diet-fed tis7(tg) mice had improved survival postresection compared with WT littermates. High-fat diet feeding in the setting of tis7 deletion resulted in postresection anastomotic inflammation and small bowel obstruction. Tolerance of a calorie-rich, high-fat diet postresection may require tis7 and its target genes. The presence of luminal fat in the setting of tis7 deletion promotes an intestinal inflammatory response postresection.

CXCL5 is required for angiogenesis, but not structural adaptation after small bowel resection

PURPOSE

Intestinal adaptation is the compensatory response to massive small bowel resection (SBR) and characterized by lengthening of villi and deepening of crypts, resulting in increased mucosal surface area. Previous studies have demonstrated increased villus capillary blood vessel density after SBR, suggesting a role for angiogenesis in the development of resection-induced adaptation. Since we have previously shown enhanced expression of the proangiogenic chemokine CXCL5 after SBR, the purpose of this study was to determine the effect of disrupted CXCL5 expression on intestinal adaptation.

METHODS

CXCL5 knockout (KO) and C57BL/6 wild type (WT) mice were subjected to either a 50% proximal SBR or sham operation. Ileal tissue was harvested on postoperative day 7. To assess for adaptation, villus height and crypt depth were measured. Submucosal capillary density was measured by CD31 immunohistochemistry.

RESULTS

Both CXCL5-KO and WT mice demonstrated normal structural features of adaptation. Submucosal capillary density increased in the WT but not in the KO mice following SBR.

CONCLUSION

CXCL5 is required for increased intestinal angiogenesis during resection-induced adaptation. Since adaptive villus growth occurs despite impaired CXCL5 expression and enhanced angiogenesis, this suggests that the growth of new blood vessels is not needed for resection-induced mucosal surface area expansion following massive SBR.

Intestinal adaptation following resection

Intestinal adaptation is a natural compensatory process that occurs following extensive intestinal resection, whereby structural and functional changes in the intestine improve nutrient and fluid absorption in the remnant bowel. In animal studies, postresection structural adaptations include bowel lengthening and thickening and increases in villus height and crypt depth. Functional changes include increased nutrient transporter expression, accelerated crypt cell differentiation, and slowed transit time. In adult humans, data regarding adaptive changes are sparse, and the mechanisms underlying intestinal adaptation remain to be fully elucidated. Several factors influence the degree of intestinal adaptation that occurs post resection, including site and extent of resection, luminal stimulation with enteral nutrients, and intestinotrophic factors. Two intestinotrophic growth factors, the glucagon-like peptide 2 analog teduglutide and recombinant growth hormone (somatropin), are now approved for clinical use in patients with short bowel syndrome (SBS). Both agents enhance fluid absorption and decrease requirements for parenteral nutrition (PN) and/or intravenous fluid. Intestinal adaptation has been thought to be limited to the first 1-2 years following resection in humans. However, recent data suggest that a significant proportion of adult patients with SBS can achieve enteral autonomy, even after many years of PN dependence, particularly with trophic stimulation.

Successful rehabilitation in pediatric ultrashort small bowel syndrome

OBJECTIVE

To examine treatment outcomes in pediatric patients with ultrashort small bowel (USSB) syndrome in an intestinal rehabilitation program (IRP).

STUDY DESIGN

We reviewed IRP records for 2001-2011 and identified 28 children with USSB (≤ 20 cm of small bowel). We performed univariate analysis using the Fisher exact test and Wilcoxon rank-sum test to compare characteristics of children who achieved parenteral nutrition (PN) independence with intact native bowel and those who did not. Growth, nutritional status, and hepatic laboratory test results were compared from the time of enrollment to the most recent values using the Wilcoxon signed-rank test.

RESULTS

Of the 28 patients identified, 27 (96%) survived. Almost one-half (48%) of these survivors achieved PN independence with their native bowel. The successfully rehabilitated patients were more likely to have an intact colon and ileocecal valve (P = .01). Significant improvements in PN kcal/kg, total bilirubin, and height and weight z-scores were seen in all patients, but serum hepatic transaminase levels did not improve in the nonrehabilitated patients.

CONCLUSION

Enrollment in an IRP provides an excellent probability of survival for children with USSB. The presence of an intact ileocecal valve and colon are positively associated with rehabilitation in this population, but are not requisite. Approximately one-half of patients with USSB can achieve rehabilitation, with a median time to PN independence of less than 2 years. The USSB population can attain reduced PN dependence, improvement of PN-associated liver disease, and enhanced growth with the aid of an IRP.

Secondary hyperparathyroidism, vitamin D sufficiency, and serum calcium 5 years after gastric bypass and duodenal switch

BACKGROUND

The prevalence of secondary hyperparathyroidism (SHPT) is high after bariatric surgery. Vitamin D is supplied to counteract SHPT and bone disease, and we studied vitamin D associations with SHPT.

METHODS

We measured serum levels of 25-OH vitamin D and parathyroid hormone (PTH) 5 years after gastric bypass and duodenal switch. One hundred twenty-five patients were included, of whom 114 (91 %) had undergone gastric bypass and 11 (9 %) had undergone duodenal switch. SHPT was defined as PTH > 7.0 pmol/l in the absence of hypercalcemia. 25-OH vitamin D levels were divided into three categories: <50, 50-74, and ≥75 nmol/l. Serum ionized calcium, magnesium, phosphate, and creatinine were divided into tertiles.

RESULTS

Mean age ± SD was 44 ± 9 years at 5 years follow-up. Ninety out of 125 (72 %) patients were women. SHPT was present in 45 out of 114 (40 %) gastric bypass patients and in 11 out of 11 (100 %) duodenal switch patients. The prevalence was high in all vitamin D categories studied. An inverse association between ionized calcium and PTH was found. For the gastric bypass patients, the odds ratio for SHPT in the upper two tertiles of ionized calcium was 0.35; 95 % CI, 0.15-0.79; p = 0.011, compared with the lowest tertile. Supplements of vitamin D and calcium were not associated with a lower prevalence of SHPT at 5 years follow-up.

CONCLUSIONS

The prevalence of SHPT was high 5 years after gastric bypass and duodenal switch. SHPT was inversely associated with serum ionized calcium, but not with vitamin D. The supplementation used was insufficient to compensate for the impaired calcium absorption after surgery.

Up-regulation of hypoxia-inducible factor 1 alpha and hemodynamic responses following massive small bowel resection

PURPOSE

Massive small bowel resection (SBR) results in an adaptive response within the remnant bowel. We have previously shown an immediate reduction in intestinal blood flow and oxygen saturation (sO2) after SBR. We therefore sought to determine the duration of resection-induced intestinal hypoxia and expression of hypoxia-inducible factors (HIFs) following SBR.

METHODS

C57B6 mice were subjected to 50% proximal SBR or a sham procedure. Photoacoustic microscopy (PAM) was used to measure blood flow and sO2 on postoperative days (PODs) 1, 3, and 7. Ileal tissue was harvested 6h postoperatively and on PODs 1 and 2, and HIF1α, HIF2α, and VEGF mRNA expression were assessed via RT-PCR. A p value of less than 0.05 was considered significant.

RESULTS

Following SBR, reduction in intestinal blood flow persists for 24h and is followed with hyperemia by POD 3. The immediate reduction in venous sO2 and increased tissue oxygen utilization continued through POD 7. Enhanced expression of HIF1α was demonstrated 6h following SBR.

CONCLUSION

Massive SBR results in an immediate relative hypoxic state within the remnant bowel with early enhanced expression of HIF1α. On POD 7, increased tissue oxygen extraction and elevated blood flow persist in the adapting intestine.

Physiology of the small intestine after resection and transplant

PURPOSE OF REVIEW

Recent studies have evaluated intestinal physiology following bowel resection; understanding changes in small bowel physiology after intestinal transplantation has received less attention. In this review, we will examine recent studies focused on changes in intestinal physiology following resection and intestinal transplantation.

RECENT FINDINGS

Absorption, immunity, and motility are fundamental components of small bowel physiology. Absorption after resection or transplantation is mediated by adaptation and enterocyte function. After resection, adaptation results in increased villus height and crypt depth. Hepatocyte growth factor and epidermal growth factors cause enterocyte hypertrophy and hyperplasia, allowing greater peptide uptake. Little is known about intestinal adaptation after transplant, but enteral autonomy is attainable. Immunity in small bowel after transplantation relies on a balance of innate and adaptive immune responses in the presence of the luminal microbiota. Intraepithelial lymphocytes are decreased following small bowel resection. After small bowel transplant, the number and the ratio of intraepithelial lymphocytes to enterocytes, as well as changes in the microbiota, can be used to identify rejection. After intestinal transplant, immune-mediated dysmotility is common. Perioperative infliximab in addition to tacrolimus may decrease the inflammation that contributes to dysmotility.

SUMMARY

As intestinal transplantation becomes more successful, understanding how absorption, immunity, and motility changes will allow for optimization of bowel function.

Adaptation: paradigm for the gut and an academic career

Adaptation is an important compensatory response to environmental cues resulting in enhanced survival. In the gut, the abrupt loss of intestinal length is characterized by increased rates of enterocyte proliferation and apoptosis and culminates in adaptive villus and crypt growth. In the development of an academic pediatric surgical career, adaptation is also an important compensatory response to survive the ever changing research, clinical, and economic environment. The ability to adapt in both situations is critical for patients and a legacy of pediatric surgical contributions to advance our knowledge of multiple conditions and diseases.

Bowel re-dilation following serial transverse enteroplasty (STEP)

PURPOSE

The serial transverse enteroplasty (STEP) operation tapers and lengthens dilated small bowel. Some patients demonstrate bowel re-dilation following STEP. Factors associated with bowel re-dilation and its effect upon clinical outcome were evaluated.

METHODS

Twenty STEP operations were reviewed. Sixteen cases were operated for failure to advance enteral feeding and were further analyzed. Available pre- and post-STEP radiographs were independently assessed for bowel re-dilation by two experienced pediatric radiologists. Potential factors of re-dilation were evaluated. Full enteral autonomy was defined as no longer requiring parenteral nutrition (PN) and remaining off PN for at least 12 months after STEP.

RESULTS

There was complete concordance between the radiologists. 9 of 16 patients demonstrated radiographic bowel re-dilation following STEP. Age, follow-up duration, time interval between STEP and last imaging reviewed, gender, diagnoses, pre- and post-STEP bowel length and width were not significantly associated with re-dilation. However, median post-STEP duration of PN was significantly longer in the re-dilated group than in the non-dilated group (41 vs. 3 months, p = 0.006). In addition, only 1 of 9 re-dilated patients achieved enteral autonomy as compared with 6 of 7 non-dilated patients (p = 0.009).

CONCLUSION

Longer PN duration after STEP increases probability of bowel re-dilation. Patients who re-dilated following STEP are significantly less likely to achieve enteral autonomy. Larger prospective data collections are warranted to further explore these relationships.

Intestinal mucosal atrophy and adaptation

Mucosal adaptation is an essential process in gut homeostasis. The intestinal mucosa adapts to a range of pathological conditions including starvation, short-gut syndrome, obesity, and bariatric surgery. Broadly, these adaptive functions can be grouped into proliferation and differentiation. These are influenced by diverse interactions with hormonal, immune, dietary, nervous, and mechanical stimuli. It seems likely that clinical outcomes can be improved by manipulating the physiology of adaptation. This review will summarize current understanding of the basic science surrounding adaptation, delineate the wide range of potential targets for therapeutic intervention, and discuss how these might be incorporated into an overall treatment plan. Deeper insight into the physiologic basis of adaptation will identify further targets for intervention to improve clinical outcomes.