Faculty Bibliography

PURPOSE/OBJECTIVE:One of the major regulators of gastrointestinal tract development is the hedgehog signaling pathway. The purpose of this study was to evaluate the role of sonic hedgehog (SHh) signaling 24 and 48 h following intestinal ischemia-reperfusion (IR) in a rat. MATERIALS AND METHODS/METHODS:Male rats were divided into four experimental groups: (1) Sham-24 h rats underwent laparotomy and were sacrificed after 24 h, (2) Sham-48h rats underwent laparotomy and were sacrificed after 48 h, (3) IR-24h rats underwent occlusion of both superior mesenteric artery and portal vein for 20 min followed by 24 h of reperfusion, and (4) IR-48 h rats underwent ischemia for 20 min followed by 48 h of reperfusion. Intestinal structural changes, enterocyte proliferation and enterocyte apoptosis were determined by immunohistochemistry 24 and 48 h following IR. SHh-related genes and protein expression were determined using real-time PCR, Western blot and immunohistochemistry. RESULTS:IR-24 rats demonstrated a significant decrease in Shh, Ihh, GIL and Ptch2 mRNA in jejunum and ileum compared to Sham-24 animals that was accompanied by a significant decrease in the number of SHH-positive cells (Immunohistochemistry) in jejunum (2.5-fold decrease) and ileum (37%). After 48 h, IR rats demonstrated a significant increase in Dhh, Ihh, Gil and PTCH2 mRNA in jejunum as well as in Dhh, Ihh, SMO, GIL, PTCH2 mRNA in ileum compared to IR-24 animals that was coincided with increased number of SHH-positive cells in jejunum (2.6-fold increase) and ileum (1.4-fold increase). CONCLUSIONS:24 h following intestinal IR, inhibited cell turnover was associated with inhibited SHh signaling pathway. Signs of intestinal recovery appeared 48 h after IR and were correlated with increase in SHh signaling pathway activity.

Notch signaling is thought to act to drive cell versification in the lining of the small intestine. The purpose of the present study was to evaluate the role of the Notch signaling pathway in stem cell differentiation in the late stages of intestinal adaptation after massive small bowel resection in a rat. Male Sprague-Dawley rats were randomly assigned to one of two experimental groups of eight rats each: Sham rats underwent bowel transection and reanastomosis, while SBS rats underwent 75% small bowel resection. Rats were euthanized on day 14 Illumina's Digital Gene Expression (DGE) analysis was used to determine Notch signaling gene expression profiling. Notch-related gene and protein expression was determined using real-time PCR, Western blot analysis, and immunohistochemistry. From seven investigated Notch-related (by DGE analysis) genes, six genes were upregulated in SBS vs. control animals with a relative change in gene expression level of 20% or more. A significant upregulation of Notch signaling-related genes in resected animals was accompanied by a significant increase in Notch-1 protein levels (Western blot analysis) and a significant increase in the number of Notch1 and Hes1 (target gene)-positive cells (immunohistochemistry) compared with sham animals. Evaluation of cell differentiation has shown a strong increase in total number of absorptive cells (unchanged secretory cells) compared with control rats. In conclusion, 2 wk after bowel resection in rats, stimulated Notch signaling directs the crypt cell population toward absorptive progenitors.NEW & NOTEWORTHY This study provides novel insight into the mechanisms of cell proliferation following massive small bowel resection. We show that 2 wk after bowel resection in rats, enhanced stem cell activity was associated with stimulated Notch signaling pathway. We demonstrate that activated Notch signaling cascade directs the crypt cell population toward absorptive progenitors.

This article focuses on esophageal replacement as a surgical option for pediatric patients with end-stage esophageal disease. While it is obvious that the patient׳s own esophagus is the best esophagus, persisting with attempts to retain a native esophagus with no function and at all costs are futile and usually detrimental to the overall well-being of the child. In such cases, the esophagus should be abandoned, and the appropriate esophageal replacement is chosen for definitive reconstruction. We review the various types of conduits used for esophageal replacement and discuss the unique advantages and disadvantages that are relevant for clinical decision-making.

Pullthrough procedures for Hirschsprung diseases typically have favorable results. However, some children experience long-term postoperative complications comprising stooling disorders, such as intermittent enterocolitis, severe stool retention, intestinal obstruction, as well as incontinence. Reoperative Hirschsprung Disease surgery is complex. This begins with the workup after the initial presentation following primary pullthrough, continues with the definitive surgical correction with redo pullthrough, and ends with long-term follow-up of individuals. The decision tree can be varied with each patient. The operating pediatric surgeon must be able to utilize different operations and treatment options available. While lesser procedures may provide relief in a select population, those with residual aganglionosis or transition zone pathology or mechanical problems will likely require a redo pullthrough. Thus, the diagnostic workup, treatment plan, and definitive surgical care should be coordinated, and executed by an experienced, specialized team at a pediatric referral center.

BACKGROUND:Recent evidence suggests that elevated intra-abdominal pressure (IAP) may adversely affect the intestinal barrier function. Toll-like receptor 4 (TLR-4) is responsible for the recognition of bacterial endotoxin or lipopolysaccharide and for initiation of the Gram-negative septic shock syndrome. The objective of the current study was to determine the effects of elevated IAP on intestinal bacterial translocation (BT) and TLR-4 signaling in intestinal mucosa in a rat model. METHODS:Male Sprague-Dawley rats were randomly assigned to one of two experimental groups: sham animals (Sham) and IAP animals who were subjected to a 15 mmHg pressure pneumoperitoneum for 30 minutes. Rats were sacrificed 24 hours later. BT to mesenteric lymph nodes, liver, portal vein blood, and peripheral blood was determined at sacrifice. TLR4-related gene and protein expression (TLR-4; myeloid differentiation factor 88 [Myd88] and TNF-α receptor-associated factor 6 [TRAF6]) expression were determined using real-time PCR, western blotting, and immunohistochemistry. RESULTS:Thirty percent of sham rats developed BT in the mesenteric lymph nodes (level I) and 20% of control rats developed BT in the liver and portal vein (level II). abdominal compartment syndrome (ACS) rats demonstrated an 80% BT in the lymph nodes (Level I) and 40% BT in the liver and portal vein (Level II). Elevated BT was accompanied by a significant increase in TLR-4 immunostaining in jejunum (51%) and ileum (35.9%), and in a number of TRAF6-positive cells in jejunum (2.1%) and ileum (24.01%) compared to control animals. ACS rats demonstrated a significant increase in TLR4 and MYD88 protein levels compared to control animals. CONCLUSIONS:Twenty-four hours after the induction of elevated IAP in a rat model, increased BT rates were associated with increased TLR4 signaling in intestinal mucosa.

Background Chelerythrine (CHE) is a benzophenanthridine alkaloid that is a potent, selective, and cell-permeable protein kinase C inhibitor. The purpose of the present study was to examine the effect of CHE on intestinal recovery and enterocyte turnover after intestinal ischemia-reperfusion (IR) injury in rats. Methods Male Sprague-Dawley rats were divided into four experimental groups: (1) sham rats underwent laparotomy, (2) sham-CHE rats underwent laparotomy and were treated with intraperitoneal CHE; (3) IR-rats underwent occlusion of both superior mesenteric artery and portal vein for 30 minutes followed by 48 hours of reperfusion, and (4) IR-CHE rats underwent IR and were treated with intraperitoneal CHE immediately before abdominal closure. Intestinal structural changes, Park injury score, enterocyte proliferation, and enterocyte apoptosis were determined 24 hours following IR. The expression of Bax, Bcl-2, p-ERK, and caspase-3 in the intestinal mucosa was determined using real Western blot and immunohistochemistry. Results Treatment with CHE resulted in a significant decrease in Park injury score in jejunum (threefold decrease) and ileum (twofold decrease), and parallel increase in mucosal weight in jejunum and ileum, villus height in jejunum and ileum, and crypt depth in ileum compared with IR animals. IR-CHE rats also experienced a significantly lower apoptotic index in jejunum and ileum, which was accompanied by a lower Bax/Bcl2 ratio compared with IR animals. Conclusions Treatment with CHE inhibits programmed cell death and prevents intestinal mucosal damage following intestinal IR in a rat.

The Wnt/beta-catenin signaling cascade is implicated in the control of stem cell activity, cell proliferation, and cell survival of the gastrointestinal epithelium. Recent evidence indicates that the Wnt/beta-catenin pathway is activated under diabetic conditions. The purpose of this study was to evaluate the role of Wnt/beta-catenin signaling during diabetes-induced enteropathy in a rat model. Male rats were divided into three groups: control rats received injections of vehicle; diabetic rats received injections of one dose of streptozotocin (STZ); and diabetic-insulin rats received injections of STZ and were treated with insulin given subcutaneously at a dose of 1 U/kg twice daily. Rats were killed on day 7. Wnt/beta-catenin-related genes and expression of proteins was determined using real-time PCR, western blotting, and immunohistochemistry. Among 13 genes identified by real-time PCR, seven genes were upregulated in diabetic rats compared with control animals including the target genes c-Myc and Tcf4. Diabetic rats also showed a significant increase in beta-catenin protein compared with control animals. Treatment of diabetic rats attenuated the stimulating effect of diabetes on intestinal cell proliferation and Wnt/beta-catenin signaling. In conclusion, enhanced intestinal epithelial cell proliferation in diabetic rats correlates with beta-catenin accumulation.