Heart Rate Variability as a Prognostic Tool for Gastroschisis Infants in the Neonatal Intensive Critical Unit.

OBJECTIVE: Gastroschisis is the most common congenital abdominal wall defect, with an increasing incidence. It results in extrusion of abdominal contents with associated delayed intestinal motility. Abnormal heart rate characteristics (HRCs) such as decreased variability occur due to the inflammatory response to sepsis in preterm infants. This study aimed to test the hypothesis that infants with gastroschisis have decreased heart rate variability (HRV) after birth and that this physiomarker may predict outcomes. STUDY DESIGN: We analyzed heart rate data from and clinical variables for all infants admitted with gastroschisis from 2009 to 2020. RESULTS: Forty-seven infants were admitted during the study period and had available data. Complex gastroschisis infants had reduced HRV after birth. For those with sepsis and necrotizing enterocolitis, abnormal HRCs occurred early in the course of illness. CONCLUSION: Decreased HRV was associated with complex gastroschisis. Infants in this group experienced complications that prolonged time to full enteral feeding and time on total parenteral nutrition. KEY POINTS: · Infants with gastroschisis can be classified into two subcategories, simple and complex disease.. · Those with complex disease often require prolonged stays in the neonatal intensive care unit and costly hospitalizations. We hypothesized that infants with complex gastroschisis are more likely to have abnormal HRC due to intestinal inflammation.. · In this study, we identified associations between abnormal HRV, heart rate characteristicHRC, and the development of gastroschisis complications. Additionally, we described differences in clinical characteristics between infants with complex versus simple gastroschisis..

A dual-institutional study on first-year practice outcomes of pediatric surgeons who trained in the era of work hour restrictions.

BACKGROUND: In July 2003, an 80-h work week restriction for residencies was mandated. This was met with skepticism regarding its potential impact on operative training. We hypothesized no difference in outcomes for pediatric surgeons who trained under duty hour restrictions compared to historical complication rates. METHODS: Dual-institutional review of pediatric patients who underwent five of the most common operations (2013-2018) by first-year pediatric surgeons who trained under duty hour restrictions was performed. Tests of proportions were used to compare complication rates to published rates on data collected prior to 2003. RESULTS: Patient mean age was 10.1 years. No significant differences (p values > 0.05) were found in laparoscopic appendectomy rates of infection, bleeding or intra-abdominal abscess compared to previously published rates. Pyloromyotomy rates of infection or duodenal perforation were not different. No differences were detected in rates of infection, recurrence or testicular atrophy for inguinal hernia repair. Umbilical hernia rates of infection, bleeding, and recurrence were also not different. There was no difference in CVC rates of hemopneumothoraces; significantly more bleeding events were detected (1.2% vs. 0.1%; p value = 0.04). CONCLUSION: In this study, first-year complication rates of pediatric surgeons who trained under duty hour restrictions were not significantly different when compared to published rates.

Childhood cancer survivors face markedly worse overall survival after diagnosis with breast cancer, melanoma, or colorectal cancer.

BACKGROUND: Childhood cancer survivors (CCS) are at elevated risk of secondary malignancies (SM). Enhanced screening for SM is recommended, but compliance is poor. We hypothesized that CCS with adult-onset SM (colorectal cancer [CRC], melanoma, or breast cancer [BC]) would present with more advanced disease and have decreased overall survival (OS). METHODS: The Surveillance, Epidemiology, and End Results Program was queried for patients diagnosed with cancer at age less than or equal to 18 also diagnosed with adult-onset CRC, melanoma, or BC. A cohort without a history of prior malignancy was likewise identified. Tumor features and clinical outcomes were compared. RESULTS: CCS with a SM (n = 224) were compared with patients without a childhood cancer history (n = 1,392,670). CCS were diagnosed younger (BC = 37.6 vs. 61.3, p < 0.01, CRC = 35.0 vs. 67.1, p < 0.01, melanoma = 29.6 vs. 61.3 years old, p < 0.01). CCS with BC were more likely to have Stage III or IV disease (25.2% vs. 16.5%, p = 0.01). Hormone-receptor expression also differed; CCS were less likely to develop Luminal A-type tumors (48.6% vs. 66.9%, p = 0.01). After age-adjustment, CCS had worse OS (Hazard ratio: CRC = 2.449, p < 0.01, melanoma = 6.503, p < 0.01, BC = 3.383, p < 0.01). CONCLUSION: CCS were younger when diagnosed with a SM. After age-adjustment, OS was diminished. Heightened surveillance may be necessary for CCS diagnosed with SM.

Lung surgery in children and their post-operative risk of respiratory infection.

PURPOSE: Pediatric surgeons at our institution are often asked by families about a theoretical increased risk of severe common upper respiratory infections in children status post lung resection. No data exist on this topic. We, therefore, aimed to examine the risk of severe respiratory infection in children after pulmonary resection. METHODS: A chart review was conducted on all pediatric patients who underwent pulmonary resection between August 1st, 2009 and January 31st, 2019. Collected data included patient characteristics, operation, complications and any admission for respiratory infection. RESULTS: Fifty-seven patients met inclusion criteria. Resections included lobectomy (45.6%), segmentectomy (14.0%), and wedge resection (40.4%). Twelve (21.1%) were immunocompromised and 6 (10.5%) had post-operative complications. Within 1 year of surgery, 2 (3.5%) patients were hospitalized for a viral upper respiratory illness (URI), 1 (1.8%) for bacterial pneumonia, and none due to influenza. CONCLUSION: In the general pediatric population, the risk of admission for respiratory illness is 3-21%. At this institution, overall risk of respiratory infection after lung resection appears comparable to baseline community risk. Our findings could aid counseling pediatric patients and their families regarding the 1-year risk of infection after lung resection.

Clinical regression of inguinal hernias in premature infants without surgical repair.

BACKGROUND: The incidence of inguinal hernias in premature infants is approximately 30%. Due to concerns about a high risk of incarceration, early repair is commonly performed. We present a series of patients whose families opted to delay repair until after 55 weeks corrected gestational age (GA) and experienced safe clinical regression of their hernias. METHODS: Between June 2015 and July 2020, premature infants (< 37 weeks GA) diagnosed with inguinal hernias on physical examination were identified. Families of eligible infants were offered either immediate or delayed repair after 55 weeks corrected GA. Infants whose families elected to delay were followed until their hernia(s) clinically regressed, or until older than 55 weeks. RESULTS: Families of 68 infants consented to delay repair. 23 infants (33.8%) had hernias that clinically regressed at median follow up from diagnosis of 14.1 weeks. Univariate analysis demonstrated female sex as a significant predictor of hernia clinical regression (OR: 3.08; p = 0.046). Of the 45 infants who underwent repair, 84.4% safely progressed to 55 weeks corrected GA prior to. CONCLUSION: Delaying inguinal hernia repair in this series of premature infants until after 55 weeks corrected GA revealed that one third of hernias, especially in females, safely regressed upon follow-up examination.

Gastrostomy tubes appear to be safe following pediatric orthotopic heart transplant.

BACKGROUND: Gastrostomy tube (GT) placement is a common pediatric surgical procedure typically indicated for oral aversion. This may develop in patients with congenital heart disease (CHD) who require an orthotopic heart transplant (OHT). The safety profile of GT placement in OHT patients who are immunosuppressed is unknown. Given the potential increased risk of wound site complications on a patient receiving immunosuppression, we sought to determine the safety profile of GT placement in pediatric patients with OHT. MATERIALS AND METHODS: We performed a retrospective case series of all pediatric OHT recipients who subsequently underwent GT placement from January 1, 2009, to August 1, 2018, at the University of Virginia Children's Hospital. Major GT complications of wound breakdown, wound infection, peristomal GT leakage, ileus, or persistent emesis, and minor GT complication including the presence of granulation tissue are reported. RESULTS: Six patients who had a pediatric OHT subsequently underwent GT placement over the study period. There were no major 30-day or 90-day GT complications. One patient had excessive granulation tissue at their GT site. There were no accounts of acute kidney injury, urinary tract infection, sepsis, or pneumonia. CONCLUSION: Gastrostomy tube (GT) placement appears to be safe in pediatric OHT patients who are on immunosuppressive medications and unable to feed orally. This is the first study documenting the safety profile of GTs in pediatric OHT patients and may aid clinicians to make decisions regarding this intervention.

Human and mouse tissue-engineered small intestine both demonstrate digestive and absorptive function.

Short bowel syndrome (SBS) is a devastating condition in which insufficient small intestinal surface area results in malnutrition and dependence on intravenous parenteral nutrition. There is an increasing incidence of SBS, particularly in premature babies and newborns with congenital intestinal anomalies. Tissue-engineered small intestine (TESI) offers a therapeutic alternative to the current standard treatment, intestinal transplantation, and has the potential to solve its biggest challenges, namely donor shortage and life-long immunosuppression. We have previously demonstrated that TESI can be generated from mouse and human small intestine and histologically replicates key components of native intestine. We hypothesized that TESI also recapitulates native small intestine function. Organoid units were generated from mouse or human donor intestine and implanted into genetically identical or immunodeficient host mice. After 4 wk, TESI was harvested and either fixed and paraffin embedded or immediately subjected to assays to illustrate function. We demonstrated that both mouse and human tissue-engineered small intestine grew into an appropriately polarized sphere of intact epithelium facing a lumen, contiguous with supporting mesenchyme, muscle, and stem/progenitor cells. The epithelium demonstrated major ultrastructural components, including tight junctions and microvilli, transporters, and functional brush-border and digestive enzymes. This study demonstrates that tissue-engineered small intestine possesses a well-differentiated epithelium with intact ion transporters/channels, functional brush-border enzymes, and similar ultrastructural components to native tissue, including progenitor cells, whether derived from mouse or human cells.

Vitrification preserves murine and human donor cells for generation of tissue-engineered intestine.

BACKGROUND: Short bowel syndrome causes significant morbidity and mortality. Tissue-engineered intestine may serve as a viable replacement. Tissue-engineered small intestine (TESI) has previously been generated in the mouse model from donor cells that were harvested and immediately reimplanted; however, this technique may prove impossible in children who are critically ill, hemodynamically unstable, or septic. We hypothesized that organoid units (OU), multicellular clusters containing epithelium and mesenchyme, could be cryopreserved for delayed production of TESI. METHODS: OU were isolated from <3 wk-old mouse or human ileum. OU were then cryopreserved by either standard snap freezing or vitrification. In the snap freezing protocol, OU were suspended in cryoprotectant and transferred directly to -80°C for storage. The vitrification protocol began with a stepwise increase in cryoprotectant concentration followed by liquid supercooling of the OU solution to -13°C and nucleation with a metal rod to induce vitrification. Samples were then cooled to -80°C at a controlled rate of -1°C/min and subsequently plunged into liquid nitrogen for long-term storage. OU from both groups were maintained in cryostorage for at least 72 h and thawed in a 37°C water bath. Cryoprotectant was removed with serial sucrose dilutions and OU were assessed by Trypan blue assay for post-cryopreservation viability. Via techniques previously described by our laboratory, the thawed murine or human OU were either cultured in vitro or implanted on a scaffold into the omentum of a syngeneic or irradiated Nonobese Diabetic/Severe Combined Immunodeficiency, gamma chain deficient adult mouse. The resultant TESI was analyzed by histology and immunofluorescence. RESULTS: After cryopreservation, the viability of murine OU was significantly higher in the vitrification group (93 ± 2%, mean ± standard error of the mean) compared with standard freezing (56 ± 6%) (P < 0.001, unpaired t-test, n = 25). Human OU demonstrated similar viability after vitrification (89 ± 2%). In vitro culture of thawed OU produced expanding epithelial spheres supported by a layer of mesenchyme. TESI was successfully generated from the preserved OU. Hematoxylin and eosin staining demonstrated a mucosa composed of a simple columnar epithelium whereas immunofluorescence staining confirmed the presence of both progenitor and differentiated epithelial cells. Furthermore, beta-2-microglobulin confirmed that the human TESI epithelium originated from human cells. CONCLUSIONS: We demonstrated improved multicellular viability after vitrification over conventional cryopreservation techniques and the first successful vitrification of murine and human OU with subsequent TESI generation. Clinical application of this method may allow for delayed autologous implantation of TESI for children in extremis.

Delayed family reunification of pediatric disaster survivors increases mortality and inpatient hospital costs: a simulation study.

BACKGROUND: Disasters occur randomly and can severely tax the health care delivery system of affected and surrounding regions. A significant proportion of disaster survivors are children, who have unique medical, psychosocial, and logistical needs after a mass casualty event. Children are often transported to specialty centers after disasters for a higher level of pediatric care, but this can also lead to separation of these survivors from their families. In a recent theoretical article, we showed that the availability of a pediatric trauma center after a mass casualty event would decrease the time needed to definitively treat the pediatric survivor cohort and decrease pediatric mortality. However, we also found that if the pediatric center was too slow in admitting and discharging patients, these benefits were at risk of being lost as children became "trapped" in the slow center. We hypothesized that this effect could result in further increased mortality and greater costs. METHODS: Here, we expand on these ideas to test this hypothesis via mathematical simulation. We examine how a delay in discharge of part of the pediatric cohort is predicted to affect mortality and the cost of inpatient care in the setting of our model. RESULTS: We find that mortality would increase slightly (from 14.2%-16.1%), and the cost of inpatient care increases dramatically (by a factor of 21) if children are discharged at rates consistent with reported delays to reunification after a disaster from the literature. CONCLUSIONS: Our results argue for the ongoing improvement of identification technology and logistics for rapid reunification of pediatric survivors with their families after mass casualty events.

Tissue-engineering of the gastrointestinal tract.

PURPOSE OF REVIEW: The purpose of this review is to describe recent advancements in tissue-engineering of the gastrointestinal system. For some patients, a congenital or acquired defect in the alimentary system results in digestive or nutritional deficiencies requiring intervention. Unfortunately, these treatments are associated with morbid complications. Advances in the growth of tissue-engineered esophagus, stomach, small intestine, colon and anus have been made in recent years. The progress reviewed here hopefully will someday benefit patients with gastrointestinal organ loss by providing a tissue replacement with morphology and function similar to native tissue. RECENT FINDINGS: In native gastrointestinal tissue, epithelial homeostasis is governed largely by the interaction of the stem cell and its surrounding cellular niche. In particular, the small intestinal stem cell populations identified as the crypt base columnar cell (CBCC) and at cell position 4 (cp4) are responsible for mucosal maintenance and response to injury. This work influences efforts to generate bioengineered tissues for both in-vitro mucosal models and full-thickness in-vivo tissue-engineered esophagus, stomach, intestine and colon. SUMMARY: Gastrointestinal organ loss is a challenge to manage. Current therapy can be life-saving, but is associated with morbid complications. Tissue-engineering will someday restore normal gastrointestinal function and eliminate the need for nutritional supplementation or transplant.

Pediatric surgical errors: A systematic scoping review.

BACKGROUND: Medical errors were largely concealed prior to the landmark report "To Err Is Human". The purpose of this systematic scoping review was to determine the extent pediatric surgery defines and studies errors, and to explore themes among papers focused on errors in pediatric surgery. METHODS: The methodological framework used to conduct this scoping study has been outlined by Arksey and O'Malley. In January 2020, PubMed, the Cochrane Database of Systematic Reviews, and the Cochrane Central Register of Controlled Trials were searched. Oxford Level of Evidence was assigned to each study; only studies rated Level 3 or higher were included. RESULTS: Of 3,064 initial studies, 12 were included in the final analysis: 4 cohort studies, and 8 outcome/audit studies. This data represented 5,442,000 aggregate patients and 8,893 errors. There were 6 different error definitions and 5 study methods. Common themes amongst the studies included a systems-focused approach, an increase in errors seen with increased complexity, and studies exploring the relationship between error and adverse events. CONCLUSIONS: This study revealed multiple error definitions, multiple error study methods, and common themes described in the pediatric surgical literature. Opportunities exist to improve the safety of surgical care of children by reducing errors. Original Scientific Research Type of Study: Systematic Scoping Review Level of Evidence Rating: 1.

Food Insecurity and Obesity in US Adolescents: A Population-Based Analysis.

Background: Food insecurity and obesity are significant problems affecting adolescents. There is a paucity of recent data examining this relationship. This study utilizes a recent nationally representative sample of US adolescents to examine the relationship between obesity and food security status, as well as other risk factors. Methods: A cross-sectional analysis of 4777 US adolescents (13-18 years old) was performed using data from the National Health and Nutrition Examination Surveys 2007-2016. Prevalence of obesity based on food security status was calculated. Multivariable logistic regression was performed to examine characteristics of adolescents in relationship to obesity. Results: The prevalence of obesity among adolescents from food insecure households was significantly higher compared to those who were not, with a prevalence ratio of 1.3 (95% CI: 1.2-1.5, p < 0.0001). Food insecurity was associated with a higher unadjusted rate of obesity, with an odds ratio of 1.4 (95% CI: 1.2-1.7, p = 0.0002). After adjustment for potential confounding factors, food insecurity was no longer significantly associated with obesity (OR 1.19, 95% CI: 1.0-1.4, p = 0.08). However, other factors such as black race, Hispanic ethnicity, male sex, and households with a monthly income ≤185% of the poverty line were associated with increased odds of obesity. Conclusions: While the prevalence of obesity in adolescents from food insecure households was higher compared to those who were not, no association between the two was found when accounting for other risk factors. Data on independent food-seeking behaviors of adolescents may help clarify this complex relationship in future work.

A multimodal protocol utilizing liposomal bupivacaine rib blocks leads to opioid reduction in patients undergoing the Nuss procedure.

BACKGROUND: A major challenge associated with the Nuss procedure for pectus excavatum repair is postoperative pain control. Early Recovery Program (ERP) protocols for the Nuss procedure are becoming common, but there is a paucity of experience using liposomal bupivacaine (LB), a long-acting local anesthetic, for rib blocks in this setting. We investigated whether a protocol utilizing LB rib blocks decreased opioid use after the Nuss procedure while achieving equivalent pain control. METHODS: All adolescent patients undergoing the Nuss procedure at our institution between January 2013 and January 2021 were included. Patients were divided into a pre-intervention cohort (n=15), a transition cohort (n=4), and a post-intervention cohort (n=13). Patients in all groups received scheduled acetaminophen and non-steroidals postoperatively. The pre-intervention cohort received an opioid patient-controlled analgesia (PCA) pump postoperatively, with a transition to oral opiates. The transition and post-intervention cohorts received scheduled gabapentin in addition to intraoperative bilateral rib blocks with longer-acting local anesthetic. Rib blocks were performed using 0.25% Bupivacaine in the pre-intervention group. In the transition group, epinephrine (1 mg/kg) was added to 0.25% bupivacaine for the rib block. Following approval in patients aged 13-18 years, 1.3% LB (2.25 mg/kg) was given for a rib block in the post-intervention cohort. RESULTS: Demographic and clinical variables were equivalent in all groups. Post-intervention patients received 90% fewer opioids [median morphine equivalent (MME) mg/kg] compared to the pre-intervention cohort (0.8 vs. 8.2 MME mg/kg, P<0.0001), with no significant difference in pain scores between groups. Hospital length of stay was decreased among the intervention cohort (3 vs. 4 days, P=0.002). CONCLUSIONS: Significant decreases in opioid use and length of stay after the Nuss procedure were achieved by the implementation of a multimodal ERP for pain management, without increase in patient-reported pain scores.

Intestinal crypt-derived enteroid coculture in presence of peristaltic longitudinal muscle myenteric plexus.

The role of enteric neurons in driving intestinal peristalsis has been known for over a century. However, in recent decades, scientists have begun to unravel additional complex interactions between this nerve plexus and other cell populations in the intestine. Investigations into these potential interactions are complicated by a paucity of tractable models of these cellular relationships. Here, we describe a novel technique for ex vivo coculture of enteroids, so called "mini-guts," in juxtaposition to the longitudinal muscle myenteric plexus (LMMP). Key to this system, we developed a LMMP culture media that: (i) allows the LMMP to maintain ex vivo peristalsis for 2 weeks along with proliferation of neurons, glia, smooth muscle and fibroblast cells, and (ii) supports the proliferation and differentiation of the intestinal stem cells into enteroids complete with epithelial enterocytes, Paneth cells, goblet cells, and enteroendocrine cells. Importantly, this technique identifies a culture condition that supports both the metabolic needs of intestinal epithelium as well as neuronal elements, demonstrating the feasibility of maintaining these two populations in a single culture system. This sets the stage for experiments to better define the regulatory interactions of these two important intestinal cell populations.

The Enteric Nervous System and Its Emerging Role as a Therapeutic Target.

The gastrointestinal (GI) tract is innervated by the enteric nervous system (ENS), an extensive neuronal network that traverses along its walls. Due to local reflex circuits, the ENS is capable of functioning with and without input from the central nervous system. The functions of the ENS range from the propulsion of food to nutrient handling, blood flow regulation, and immunological defense. Records of it first being studied emerged in the early 19th century when the submucosal and myenteric plexuses were discovered. This was followed by extensive research and further delineation of its development, anatomy, and function during the next two centuries. The morbidity and mortality associated with the underdevelopment, infection, or inflammation of the ENS highlight its importance and the need for us to completely understand its normal function. This review will provide a general overview of the ENS to date and connect specific GI diseases including short bowel syndrome with neuronal pathophysiology and current therapies. Exciting opportunities in which the ENS could be used as a therapeutic target for common GI diseases will also be highlighted, as the further unlocking of such mechanisms could open the door to more therapy-related advances and ultimately change our treatment approach.

Synthesis and Evaluation of the Sensitivity and Vibrational Lifetimes of Thiocyanate and Selenocyanate Infrared Reporters.

Two novel 2'-deoxyadenosine (dA) analogues, Si2-dA-SCN and Si2-dA-SeCN, and two novel phenylalanine (Phe) analogues, Boc-Me-PheCH2SCN and Boc-Me-PheCH2SeCN, have been synthesized and the thiocyanate (SCN) and selenocyanate (SeCN) functional groups evaluated as vibrational reporters. The syntheses of Si2-dA-SCN and Si2-dA-SeCN were accomplished in three steps in 16% and 32% overall yields, respectively, and the syntheses of Boc-Me-PheCH2SCN and Boc-Me-PheCH2SeCN were completed in four steps in 8.9% and 2.3% overall yields, respectively. The SCN and SeCN stretch vibrational modes were shown to be sensitive to the local environment by frequency shifts and full-width half-maximum (fwhm) changes in response to tetrahydrofuran (THF) and THF/water solvent mixtures. The vibrational lifetimes of the Si2-dA-SeCN (237±12 ps) and Boc-Me-PheCH2SeCN (295±31 ps) in THF solution were determined by ultrafast infrared pump-probe spectroscopy to be 1.5 to 3 times longer than those for Si2-dA-SCN (140±6 ps) and Boc-Me-PheCH2SCN (102±4 ps). The longer lifetimes for the SeCN analogues were attributed to the better insulating effects of the heavier selenium atom compared to the sulfur atom. The solvent sensitivity and longer vibrational lifetimes compared to other vibrational reporters suggest that SCN and SeCN vibrational reporters are well suited to studying several dynamic processes including protein and nucleic acid hydration and conformational changes, however stability issues may require post-synthetic modification methods to incorporate these reporters into biomacromolecules.

Fgf10 overexpression enhances the formation of tissue-engineered small intestine.

Short bowel syndrome (SBS) is a morbid and mortal condition characterized in most patients by insufficient intestinal surface area. Current management strategies are inadequate, but tissue-engineered small intestine (TESI) offers a potential therapy. A barrier to translation of TESI is the generation of scalable mucosal surface area to significantly increase nutritional absorption. Fibroblast growth factor 10 (Fgf10) is a critical growth factor essential for the development of the gastrointestinal tract. We hypothesized that overexpression of Fgf10 would improve the generation of TESI. Organoid units, the multicellular donor tissue that forms TESI, were derived from Rosa26(rtTA/+), tet(o)Fgf10/(-) or Fgf10(Mlc-nlacZ-v24) (hereafter called Fgf10(lacZ)) mice. These were implanted into the omentum of NOD/SCID γ-chain-deficient mice and induced with doxycycline in the case of tet(o)Fgf10/(-). Resulting TESI were explanted at 4 weeks and studied by histology, quantitative RT-PCR and immunofluorescence. Four weeks after implantation, Fgf10 overexpressing TESI was larger and weighed more than the control tissues. Within the mucosa, the villus height was significantly longer and crypts contained a greater percentage of proliferating epithelial cells. A fully differentiated intestinal epithelium with enterocytes, goblet cells, enteroendocrine cells and Paneth cells was identified in the Fgf10-overexpressing TESI, comparable to native small intestine. ß-Galactosidase expression was found in both the epithelium and the mesenchyme of the TESI derived from the Fgf10(LacZ) duodenum. However, this was not the case with TESI generated from jejunum and ileum. We conclude that Fgf10 enhances the formation of TESI.

Sequestration of Vascular Endothelial Growth Factor (VEGF) Induces Late Restrictive Lung Disease.

RATIONALE: Neonatal respiratory distress syndrome is a restrictive lung disease characterized by surfactant deficiency. Decreased vascular endothelial growth factor (VEGF), which demonstrates important roles in angiogenesis and vasculogenesis, has been implicated in the pathogenesis of restrictive lung diseases. Current animal models investigating VEGF in the etiology and outcomes of RDS require premature delivery, hypoxia, anatomically or temporally limited inhibition, or other supplemental interventions. Consequently, little is known about the isolated effects of chronic VEGF inhibition, started at birth, on subsequent developing lung structure and function. OBJECTIVES: To determine whether inducible, mesenchyme-specific VEGF inhibition in the neonatal mouse lung results in long-term modulation of AECII and whole lung function. METHODS: Triple transgenic mice expressing the soluble VEGF receptor sFlt-1 specifically in the mesenchyme (Dermo-1/rtTA/sFlt-1) were generated and compared to littermate controls at 3 months to determine the impact of neonatal downregulation of mesenchymal VEGF expression on lung structure, cell composition and function. Reduced tissue VEGF bioavailability has previously been demonstrated with this model. MEASUREMENTS AND MAIN RESULTS: Triple transgenic mice demonstrated restrictive lung pathology. No differences in gross vascular development or protein levels of vascular endothelial markers was noted, but there was a significant decrease in perivascular smooth muscle and type I collagen. Mutants had decreased expression levels of surfactant protein C and hypoxia inducible factor 1-alpha without a difference in number of type II pneumocytes. CONCLUSIONS: These data show that mesenchyme-specific inhibition of VEGF in neonatal mice results in late restrictive disease, making this transgenic mouse a novel model for future investigations on the consequences of neonatal RDS and potential interventions.

A "living bioreactor" for the production of tissue-engineered small intestine.

Here, we describe the use of a mouse model as a living bioreactor for the generation of tissue-engineered small intestine. Small intestine is harvested from donor mice with subsequent isolation of organoid units (a cluster of mesenchymal and epithelial cells). Some of these organoid units contain pluripotent stem cells with a preserved relationship with the mesenchymal stem cell niche. A preparation of organoid units is seeded onto a biodegradable scaffold and implanted intraperitoneally within the omentum of the host animal. The cells are nourished initially via imbibition until neovascularization occurs. This technique allows the growth of fully differentiated epithelium (composed of Paneth cells, goblet cells, enterocytes and enteroendocrine cells), muscle, nerve, and blood vessels of donor origin. Variations of this technique have been used to generate tissue-engineered stomach, large intestine, and esophagus. The variations include harvest technique, length of digestion, and harvest times.

Human tissue-engineered small intestine forms from postnatal progenitor cells.

PURPOSE: Tissue-engineered small intestine (TESI) represents a potential cure for short bowel syndrome (SBS). We previously reported full-thickness intestine formation using an organoid units-on-scaffold approach in rodent and swine models. Transplanted intestinal xenografts have been documented to survive from human fetal tissue but not from postnatal tissue. We now present the first report of human TESI from postnatal tissue. METHODS: Organoid units (OU) were prepared from human small bowel resection specimens, loaded onto biodegradable scaffolds and implanted into NOD/SCID gamma chain-deficient mice. After 4 weeks, TESI was harvested and immunostained for ß2-microglobulin to identify human tissue, villin for enterocytes, lysozyme for Paneth cells, chromogranin-A for enteroendocrine cells, mucin-2 for goblet cells, smooth muscle actin and desmin to demonstrate muscularis, and S-100 for nerves. RESULTS: All TESI was of human origin. Immunofluorescence staining of human TESI reveals the presence of all four differentiated cell types of mature human small intestine, in addition to the muscularis and the supporting intestinal subepithelial myofibroblasts. Nerve tissue is also present. CONCLUSIONS: Our technique demonstrates survival, growth, and differentiation of postnatally derived human small intestinal OU into full thickness TESI in murine hosts. This regenerative medicine strategy may eventually assist in the treatment of SBS.