Orally Dosed Citalopram Stimulates Small Intestinal Mucosal Growth.

BACKGROUND: Parenterally administered selective serotonin reuptake inhibitors, such as citalopram, increase intestinal mucosal absorptive surface by day 7 of treatment. We hypothesized that enteral citalopram would also induce intestinal mucosal growth, thus allowing for therapy with an oral agent. MATERIALS AND METHODS: Following a habituation period, C57BL/6 mice received peanut butter pellets containing 10, 50, or 100 mg/kg/d citalopram for 7 d (n = 5); or 25 mg/kg/d citalopram for 14 (n = 3) or 21 (n = 5) d; or plain peanut butter pellets for 7 (n = 2), 14 (n = 2), or 21 d (n = 3). Two-centimeter ileal segments were harvested and prepared for microscopic assessment of villus height (VH), crypt depth, villus width (VW), and crypt width. Mucosal surface area (MSA) was calculated and data were compared using Student's t-test. RESULTS: Enteral administration of citalopram had virtually no effect on VH, VW, or crypt depth after 7 d; crypt width decreased significantly (P value range 0.0002 to <0.0001), likely contributing to the increases in MSA (P value range 0.0578 to 0.0006). After 14 d of treatment, citalopram significantly increased VH (P < 0.0001), VW (P = 0.0058), and ileal MSA per mm2 (P = 0.0007). The increase in MSA was sustained at 21 d (P < 0.0001). CONCLUSIONS: Enteral citalopram given for 14 d results in increased VH and ileal MSA, which remains increased by day 21. Selective serotonin reuptake inhibitors show potential as oral therapy for serious intestinal disorders such as short bowel syndrome.

The Impact of Pediatric Surgical Specialty Meetings: A 5-year Analysis of Presented Abstracts.

BACKGROUND: Abstracts presented at the American Academy of Pediatrics Section on Surgery (AAP) and American Pediatric Surgical Association (APSA) meetings can be taken as a reasonable representation of academic activity in pediatric surgery. We sought to assess ongoing trends in pediatric surgical research by analyzing the scientific content of each association's yearly meeting. METHODS: Abstracts presented at AAP and APSA between 2009 and 2013 were identified from the final printed programs (n = 910). Video abstracts (n = 34) were excluded. Collected data included title, authors, classification (basic science/clinical), presentation type (podium/poster), and topic. Publication as a journal article was determined using the abstract title/authors in a PubMed search. Journal impact factors were recorded for each journal and a composite impact factor (CIF) was calculated by dividing the sum of impact factors by the published articles per meeting. RESULTS: Number of abstracts presented, percentage published, abstract classifications, and presentation type remained consistent over the study period. The AAP meetings accepted a higher percentage of clinical abstracts: AAP 72.3 ± 3.4% versus APSA 65.9 ± 1.3%. The five most popular topics at both meetings were oncology, congenital diaphragmatic hernia, necrotizing enterocolitis, trauma, and appendicitis. The publication rate for clinical and basic science abstracts did not vary significantly over the study period, whereas CIFs were higher for basic science publications nearly every year. The percentage of podium abstracts published was significantly greater than poster abstracts, but no statistical difference in CIF was seen between podium- and poster-associated publications. CONCLUSIONS: Abstracts accepted and presented at the two major pediatric surgical specialty meetings more commonly involve clinical studies with a trend away from basic science. Despite this, basic science abstracts tended to be published in higher impact journals. This study attempts to quantify the quality of pediatric surgical research and serves as a baseline for future comparison.

Mucosal homeostasis is altered in the ileum of gnotobiotic mice.

BACKGROUND: The microbiome of the gastrointestinal tract is a vast collection of microorganisms implicated in numerous aspects of normal physiology and disease pathogenesis. The use of gnotobiotic mouse models, with single or specific communities of microbes comprising the microbiome, can enhance our understanding of the microbiome-host relationship. We hypothesized that gnotobiotic mice would exhibit differences in mucosal homeostasis when compared with mice with conventional flora (CF). MATERIALS AND METHODS: Single-organism gnotobiotic mice were generated containing Escherichia coli MG1655, Akkermansia muciniphila, Bacteroides eggerthii, and Clostridium symbiosum, representing four of the major phyla present in the gastrointestinal tract. Distal ileal segments were harvested from adult mice, and histologic sections were H&E stained and used to measure villus height and crypt depth. Immunohistochemistry was performed with Ki67 and TUNEL as markers of proliferation and apoptosis, respectively. RESULTS: When compared to the ileum from CF mice, the ileum from all groups of gnotobiotic mice had significant increases in nearly all measured parameters. In addition, significant differences were seen among certain gnotobiotic groups for villus height, crypt depth, and apoptosis. CONCLUSIONS: Single-organism gnotobiotic mice demonstrate enhanced morphometric parameters compared with mice with CF and show differences in growth patterns among bacterial species. These findings suggest unique interactions between individual bacteria and the host animal which hold potential for future therapeutic strategies aimed at mucosal restoration. The mechanisms involved in this process therefore warrant further study.

Enhanced serotonin signaling increases intestinal neuroplasticity.

BACKGROUND: The intestinal mucosa recovers from injury by accelerating enterocyte proliferation resulting in villus growth. A similar phenomenon is seen after massive bowel resection. Serotonin (5-HT) has been implicated as an important regulator of mucosal homeostasis by promoting growth in the epithelium. The impact of 5-HT on other components of growing villi is not known. We hypothesized that 5-HT-stimulated growth in the intestinal epithelium would be associated with growth in other components of the villus such as enteric neural axonal processes. MATERIALS AND METHODS: Enteric serotonergic signaling is inactivated by the serotonin reuptake transporter, or SERT, molecule. Enhanced serotonin signaling was achieved via SERT knockout (SERTKO) and administration of selective serotonin reuptake inhibitors (SSRI) to wild-type mice (WT-SSRI). 5-HT synthesis inhibition was achieved with administration of 4-chloro-L-phenylalanine (PCPA). Intestinal segments from age-matched WT, SERTKO, WT-SSRI, and corresponding PCPA-treated animals were assessed via villus height, crypt depth, and crypt proliferation. Gap 43, a marker of neuroplasticity, was assessed via immunofluorescence and Western blot. RESULTS: SERTKO and WT-SSRI mice had taller villi, deeper crypts, and increased enterocyte proliferation compared with WT mice. Gap 43 expression via immunofluorescence was significantly increased in SERTKO and WT-SSRI samples, as well as in Western blot analysis. PCPA-treated SERTKO and WT-SSRI animals demonstrated reversal of 5-HT-induced growth and Gap 43 expression. CONCLUSIONS: Enhanced 5-HT signaling results in intestinal mucosal growth in both the epithelial cell compartment and the enteric nervous system. Furthermore, 5-HT synthesis inhibition resulted in reversal of effects, suggesting that 5-HT is a critically important regulator of intestinal mucosal growth and neuronal plasticity.

Chest wall injury fracture patterns are associated with different mechanisms of injury: a retrospective review study in the United States.

Purpose: Research on rib fracture management has exponentially increased. Predicting fracture patterns based on the mechanism of injury (MOI) and other possible correlations may improve resource allocation and injury prevention strategies. The Chest Injury International Database (CIID) is the largest prospective repository of the operative and nonoperative management of patients with severe chest wall trauma. The purpose of this study was to determine whether the MOI is associated with the resulting rib fracture patterns. We hypothesized that specific MOIs would be associated with distinct rib fracture patterns. Methods: The CIID was queried to analyze fracture patterns based on the MOI. Patients were stratified by MOI: falls, motor vehicle collisions (MVCs), motorcycle collisions (MCCs), automobile-pedestrian collisions, and bicycle collisions. Fracture locations, associated injuries, and patient-specific variables were recorded. Heat maps were created to display the fracture incidence by rib location. Results: The study cohort consisted of 1,121 patients with a median RibScore of 2 (range, 0-3) and 9,353 fractures. The average age was 57±20 years, and 64% of patients were male. By MOI, the number of patients and fractures were as follows: falls (474 patients, 3,360 fractures), MVCs (353 patients, 3,268 fractures), MCCs (165 patients, 1,505 fractures), automobile-pedestrian collisions (70 patients, 713 fractures), and bicycle collisions (59 patients, 507 fractures). The most commonly injured rib was the sixth rib, and the most common fracture location was lateral. Statistically significant differences in the location and patterns of fractures were identified comparing each MOI, except for MCCs versus bicycle collisions. Conclusions: Different mechanisms of injury result in distinct rib fracture patterns. These different patterns should be considered in the workup and management of patients with thoracic injuries. Given these significant differences, future studies should account for both fracture location and the MOI to better define what populations benefit from surgical versus nonoperative management.

The M1 muscarinic acetylcholine receptor in the crypt stem cell compartment mediates intestinal mucosal growth.

IMPACT STATEMENT: Localization of a specific subtype of the muscarinic acetylcholine receptor in the crypt stem cell compartment suggests a critical role in intestinal mucosal homeostasis. Here we demonstrate the localization of the M1 muscarinic acetylcholine receptor to the stem cell compartment and demonstrate increase morphometric and proliferative parameters when this is stimulated in vivo. These data provide novel information about this complex signaling microenvironment and offer potential future therapeutic targets for future study.

Potentiated serotonin signaling in serotonin re-uptake transporter knockout mice increases enterocyte mass and small intestinal absorptive function.

Genetic knockout of the serotonin reuptake transporter (SERT) potentiates serotonin signaling and increases crypt-cell proliferation, neuroplasticity, and mucosal surface area. However, it remains unknown whether these changes occur throughout the small intestine and whether they increase nutrient absorption. We hypothesized that serotonin-mediated mucosal growth would occur throughout the intestine and would increase enterocyte mass and absorptive function. Following institutional approval, intestinal segments spanning the bowel were harvested from 10 to 12 week-old SERT knockout (SERTKO) and wild-type (WT) C57Bl/6 mice. Histologic sections were used to measure villus height (VH), crypt depth (CD), and crypt proliferation index (CPI). Plasma citrulline was measured colorimetrically. Glucose and peptide absorption in isolated segments of small bowel were calculated using a previously described method for quantification after luminal instillation of substrate. At baseline, morphometric (VH/CD) and proliferative (CPI) parameters varied from jejunum to ileum. Enhanced 5-HT signaling significantly increased plasma citrulline levels and morphometric/proliferative parameters in all regions analyzed. Glucose absorption in WT mice varied throughout the small intestine, and SERTKO mice demonstrated significant increases in the middle and distal bowel. WT peptide absorption was similar throughout the small bowel, and SERTKO mice had significant increases in the proximal and distal bowel. Enhanced serotonin signaling results in increased morphometric and proliferative parameters throughout the small intestine, and results in increased enterocyte mass and intestinal absorptive function. These data further advance the concept that the serotonin system is an attractive therapeutic target for increasing functional intestinal mucosa.

Retracing our STEPs: Four decades of progress in intestinal lengthening procedures for short bowel syndrome.

The surgical management of intestinal failure secondary to short bowel syndrome has undergone tremendous evolution in the last several decades. From the landmark description of an intestinal lengthening procedure by Bianchi in 1980 to the multidisciplinary modern care paradigm known as intestinal rehabilitation, innovative new treatments in this field have vastly improved patient outcomes. Initial attempts to treat short bowel syndrome surgically saw the birth of reversed intestinal segments, artificial valves and colonic transposition, all aimed at decreasing transit time and thus increasing absorption. In the long term, a common pitfall of these approaches, and intestinal adaptation itself, is bowel dilation and the associated poor motility, dysfunction and propensity for bacterial overgrowth. The development of techniques to mitigate these unfavorable conditions was a prelude to the birth of modern day operations aimed at increasing bowel length and improving function. This review examines the relevant historical approaches to short bowel syndrome and how they provided the foundation for the development of current intestinal lengthening surgery, followed by an in-depth discussion of surgical techniques and their outcomes.

Potentiation of serotonin signaling leads to increased carbohydrate and lipid absorption in the murine small intestine.

BACKGROUND: Enteric serotonin influences intestinal homeostasis and functions as a mucosal growth factor. Previously, we demonstrated increased mucosal surface area and enhanced crypt cell proliferation in serotonin reuptake transporter (SERT)-deficient mice. Therefore, we hypothesized that serotonin-mediated mucosal growth would also result in enhanced carbohydrate and lipid absorption. MATERIAL AND METHODS: Wild-type C57Bl/6 (WT) and SERT-knockout (SERTKO) mice were fasted then gavaged with D-xylose or boron-dipyrromethene (BODIPY) FL-C12 medium-chain fatty acid analog. Serum D-xylose and BODIPY concentrations were serially measured from blood drawn at 30 to 360 min post-gavage. Small intestine was harvested from both groups for comparison of morphometric parameters. Area under the curve of plotted graphs was calculated, and means were compared with Student's t-test to a significance of p < 0.05. RESULTS: Villus height and crypt depth were significantly greater in the middle and distal small intestine of SERTKO animals compared to WT. Overall absorption of D-xylose and BODIPY was greater in SERTKO animals compared to WT animals. Absorption of D-xylose was persistently elevated in SERTKO animals, while there was an initial delay in BODIPY absorption followed by a sustained and significantly greater absorption in SERTKO animals at 60-360 min after gavage. CONCLUSION: Potentiation of serotonin signaling in SERTKO mice results in small intestinal mucosal growth and enhanced carbohydrate and fat absorption in vivo. These functional increases support the concept of targeting the serotonin signaling system to augment intestinal adaptation in the setting of intestinal failure.

Routine postnatal chest x-ray and intensive care admission are unnecessary for a majority of infants with congenital lung malformations.

BACKGROUND: Postnatal evaluation of prenatally identified congenital lung malformations (CLMs) often includes a chest x-ray (CXR) and neonatal intensive care unit (NICU) admission for observation. With current efforts aimed at prioritizing value and resource utilization, we sought to assess the utility of this practice in infants with known CLMs. We hypothesized that CXR and NICU admission are overused and could be deferred in the majority of cases. METHODS: Clinical and radiographic data for infants with CLM from 2007 to 2016 were reviewed with IRB approval. Regression models were developed for respiratory support (RS), symptoms within 30 days of discharge (Sx30), and abnormal CXR. Predictors included initial symptoms (IS), birth weight (BW), gestational age (GA), cyst-volume-ratio (CVR) and abnormal CXR. Odds ratios (ORs) and ROC curves were generated for significant predictors (p < 0.05). RESULTS: Fifty-eight infants were identified. Eight were excluded because birth or surgery occurred outside of our institution. Another four were excluded for requiring immediate surgery, leaving forty-six for full analysis. All infants underwent initial CXR and NICU admission, and 22 (47.8%) had an abnormal CXR. Higher CVR (OR = 6.69, p = 0.024) and lower BW (OR = 0.27, p = 0.028) both increased the odds of an abnormal CXR. Applying optimal ROC cutoffs for CVR and BW would have safely eliminated 21 of 46 CXRs, increasing CXR sensitivity from 48% to 68%. For RS and Sx30, no variable, including abnormal CXR, significantly predicted outcomes. Twenty-seven infants (59%) had a NICU stay of <24 h and only three patients (6.8%) developed Sx30. CONCLUSIONS: Both CXR and NICU admission appear to be overused in infants with CLM. CXR result did not predict need for respiratory support or symptoms following discharge, and thus may not aid in the initial evaluation or in the prediction of future care needs. Using CVR and birth weight can guide CXR use and optimize its sensitivity. Need for NICU admission could not be predicted, but a majority of infants spent <24 h in the NICU without intervention, suggesting that NICU admission was likely not needed for all infants in this setting. LEVEL OF EVIDENCE: Study of diagnostic test, Level II evidence.

Muscarinic acetylcholine receptors participate in small intestinal mucosal homeostasis.

BACKGROUND: Intestinal mucosal homeostasis is controlled by multiple factors and an intact, functional mucosa is essential for survival. Maintenance of the epithelium begins with crypt base stem cells which eventually give rise to all epithelial cell types. Evidence suggests an important role of the enteric cholinergic nervous system in these processes. We hypothesized that mice with altered muscarinic signaling would exhibit differences in mucosal morphometric and proliferative parameters compared to wild-type mice. METHODS: Mouse lines specifically deficient in one of the five muscarinic acetylcholine receptors (M1KO-M5KO) were used for experiments. Distal ileal segments were obtained and histologic sections created. Villus height and crypt depth were measured using H&E-stained sections, while crypt proliferation index (CPI) was calculated using Ki67-stained sections. RESULTS: The ileal mucosa from mice deficient in mAChRs exhibited differences from wild-type ileal mucosa in nearly all measured parameters. Knockout of mAChR2, mAChR3 and mAChR5 resulted in changes in all measured parameters. Ileal mucosa from M2KO mice showed an unexpected combination decreased VH but paradoxically increased CD and CPI. CONCLUSIONS: Alterations in mAChR signaling causes change in ileal mucosal morphometry and crypt cell proliferation. While all mAChR subtypes may be involved, mAChR2, mAChR3, and mAChR5 appear to be critical for mucosal homeostasis. Further characterization of these pathways is warranted.

Improved capacity to evaluate changes in intestinal mucosal surface area using mathematical modeling.

Quantification of intestinal mucosal growth typically relies on morphometric parameters, commonly villus height, as a surrogate for presumed changes in mucosal surface area (MSA). We hypothesized that using mathematical modeling based on multiple unique measurements would improve discrimination of the effects of interventions on MSA compared to standard measures. To determine the ability of mathematical modeling to resolve differences in MSA, a mouse model with enhanced serotonin (5HT) signaling known to stimulate mucosal growth was used. 5-HT signaling is potentiated by targeting the serotonin reuptake transporter (SERT) molecule. Selective serotonin reuptake inhibitor-treated wild-type (WT-SSRI), SERT-knockout (SERTKO), and wild-type C57Bl/6 (WT) mice were used. Distal ileal sections were H&E-stained. Villus height (VH), width (VW), crypt width (CW), and bowel diameter were used to calculate surface area enlargement factor (SEF) and MSA. VH alone for SERTKO and SSRI was significantly increased compared to WT, without a difference between SERTKO and WT-SSRI. VW and CW were significantly decreased for both SERTKO and WT-SSRI compared to WT, and VW for WT-SSRI was also decreased compared to SERTKO. These changes increased SEF and MSA for SERTKO and WT-SSRI compared to WT. Additionally, SEF and MSA were significantly increased for WT-SSRI compared to SERTKO. Mathematical modeling provides a valuable tool for differentiating changes in intestinal MSA. This more comprehensive assessment of surface area does not appear to correlate linearly with standard morphometric measures and represents a more comprehensive method for discriminating between therapies aimed at increasing functional intestinal mucosa.