Engraftment of mucosal stem cells into murine jejunum is dependent on optimal dose of cells

BACKGROUND

Transplantation of intestinal mucosal stem cells is an important step in the development of intestinal gene therapy and treatment of intestinal mucosal diseases. We hypothesized that engraftment rates increase proportionally with increasing doses of seeded stem cells and increasing jejunal débridment.

MATERIALS AND METHODS

Intestinal mucosal organoids were harvested from neonatal mice carrying a green-fluorescent protein (GFP) transgene and transplanted into adult GFP(-) mice (n = 66). In recipients, two jejunal segments (1.5 cm) were isolated with their blood circulation left intact with anastomosis of the distal and proximal segments to restore continuity. Debridement of native enterocytes was performed by perfusing luminally with ethylene diamine tetraacetc acid solutions for 20 min. A total of 5,000, 10,000, or 25,000 organoids were then seeded. Three weeks later, cross sections (n = 398) of the segments were evaluated for the presence of GFP(+) neomucosa using fluorescence microscopy. Additional segments were débrided for 30 and 40 min (n = 83). Other conditions were not tested because of the rate of high mortality in these experiments.

RESULTS

The group seeded with 10,000 organoid units at 20 min showed the highest engraftment of GFP(+) epithelium. Engraftment was improved by increasing débridment times at this seeding density. Overall mortality was 70%.

CONCLUSIONS

These findings suggest that there is an optimal seeding density of stem cell clusters for enhanced engraftment in this model. Mortality prohibited complete testing of all combinations of seeding density and debridement times.

Treatment of bile acid malabsorption using ileal stem cell transplantation

BACKGROUND

We hypothesized that ileal stem cell clusters transplanted into a segment of jejunum can be used to treat bile acid malabsorption.

STUDY DESIGN

In adult Lewis rats, a 15-cm segment of jejunum was isolated with its blood circulation left intact and partially stripped of enterocytes using luminal high-velocity perfusions with 3mmol/L ethylenediamine tetra-acetic acid solutions. Continuity was restored by anastomosing the proximal and distal gut. Ileal stem cell clusters were harvested from neonatal Lewis rats and transplanted into the stripped segments to generate a "neoileum." After 4weeks, recipients underwent resection of the native ileum, and the isolated neoileum was anastomosed in its place. After an additional 4weeks, a 48-hour stool collection was performed. The engrafted segment was harvested for taurocholate uptake studies, ileal bile acid transporter (IBAT) protein by immunohistomorphometry, and IBAT mRNA quantitation by reverse transcription polymerease chain reaction. Data were analyzed by ANOVA/t-test. Rats undergoing ileectomy, jejunectomy, or sham operations served as controls.

RESULTS

Total bile acid loss in the stool was markedly lower in rats with a neoileum compared with rats with an ileectomy (p < 0.001). Total taurocholate uptake was notably increased in the neoileum compared with the jejunum (p < 0.001). IBAT protein signal intensity was considerably higher in the neoileum compared with jejunum (p < 0.001). IBAT mRNA amounts in the neoileal group were comparable with those in normal rat ileum and were considerably higher (p = 0.003) than in the jejunum.

CONCLUSIONS

Ileal stem cell clusters were used to establish a new zone of bile acid uptake and IBAT expression in a jejunal segment. This neoileum eliminated loss of bile acids in the stool after ileectomy. This is the first time that transplantation of intestinal stem cell clusters has been shown to correct a clinical malabsorption syndrome.

Clinical features and treatment outcome of intussusception in premature neonates

BACKGROUND/PURPOSE

Less than 1.3% of all cases of intussusception occur in term neonates. Intussusception in premature neonates (IPN) is exceedingly rare. Its rarity and difficulty to differentiate IPN from common neonatal diseases like necrotizing enterocolitis (NEC) often delays its diagnosis. The authors set out to characterize diagnosis, treatment, and outcome of this rare condition.

METHODS

The authors analyzed 2 new cases of IPN and 33 previously reported cases from the literature.

RESULTS

The 35 patients with IPN had an average gestational age, postconceptual age at diagnosis, and birth weight of 28.4 +/- 0.6 weeks (all data, mean +/- SEM), 31.1 +/- 0.5 weeks, and 1,165 +/- 21 g, respectively. Gastrointestinal symptoms first presented at age 8 +/- 1 days. A preoperative diagnosis of NEC was assumed in 24 patients, delaying diagnosis by 10 +/- 2 days. Intussusception was diagnosed radiographically in 2 patients (1 contrast enema and 1 ultrasound scan) and during surgery or autopsy in the remainder. Resection was reported in 28 patients for bowel that was irreducible, necrotic, or perforated. The overall mortality rate was 20%, mainly owing to sepsis.

CONCLUSIONS

Intussusception in the premature neonate often is misdiagnosed as NEC, delaying operative intervention. Contrast enema has limited diagnostic capability. Early diagnosis may be achieved with use of ultrasound scan. Intussusception can be treated successfully with resection and primary anastomosis, achieving good results.

Identification of optimal harvest sites of ileal stem cells for treatment of bile acid malabsorption in a dog model

Ileal mucosal stem cells expressing the sodium-dependent ileal bile acid transporter (IBAT) have been successfully transplanted into the jejunum of rodents in projects aimed at creating a "neoileum" to treat bile acid malabsorption. To find optimal harvest sites for a dog model of stem cell transplantation, the exact location of peak IBAT expression in the donor ileum needs to be known. We therefore mapped IBAT function, IBAT mRNA, and IBAT protein in the ileum of Beagle dogs (N=3). Mucosal samples were taken every 5 cm in the ileum and every 20 cm in the jejunum of each dog. Sodium-dependent (active) and sodium-independent (passive) taurocholate uptake rates were measured using a standardized everted sleeve technique. IBAT mRNA concentrations were determined by semiquantitative reverse transcriptase-polymerase chain reaction and IBAT protein concentrations by fluorometric immunohistochemical analysis. The small bowel measured 208+/-17 cm (mean+/-standard error of the mean). Active and passive uptake rates were found to follow distinct distribution curves. Significant active uptake was seen only at the terminal 50 cm and peaked at 479+/-176 pM/mm(2). Depending on location, active uptake accounted for approximately half of the total uptake. IBAT mRNA and protein distributions corroborated uptake curves. The terminal 10 to 50 cm of ileum has the highest bile acid uptake capacity. This short segment appears to be the most promising donor site for ileal stem cell transplants to create a "neoileum" in dogs.

The utility of routine preoperative computed tomography scanning in the management of veterans with colon cancer

BACKGROUND

The aim of this study is to assess the clinical utility of routine preoperative computed tomography (CT) scanning in patients with cancer of the intraperitoneal colon.

METHODS

From November 1997 to June 2001, all patients at VA Puget Sound Healthcare System with a diagnosis of colon cancer were referred for a preoperative CT scan. Medical records and operative notes were reviewed to determine the influence of preoperative CT on clinical management.

RESULTS

Seventy patients received a CT per protocol. Preoperative CT provided information that was used in treatment planning and management in 26 (37%) cases. However, if preoperative scans had not been performed, the clinical management would have been definitively altered in only 13 (19%) patients.

CONCLUSIONS

Although these data suggest potential benefit for routine preoperative CT scanning, we believe additional study, including cost analysis, should precede the adoption of CT scanning as a routine preoperative study in patients with colon cancer.

Pitfalls in preparation of (3)H-unconjugated bilirubin by biosynthetic labeling from precursor (3)H-5-aminolevulinic acid in the dog

We report problems encountered during preparation of tritium-labeled unconjugated bilirubin ((3)H-UCB) from precursor (3)H-5-aminolevulinic acid ((3)H-ALA) in 2 dogs with external biliary drainage installed into the animals under general anesthesia. Under prolonged sedation, 12.9 or 14.0 mCi of (3)H-ALA was administered intravenously in two divided doses, and bile was collected for 9 hours. In one animal, taurocholate (TC) infusion was needed to maintain bile flow. (3)H-UCB was isolated from the bile and recrystallized with the improved method of Webster et al (Webster CC, Tiribelli C, Ostrow JD. J Lab Clin Med 2001;137:370-3). Based on radioactivity and pigment content, hourly bile collections were pooled to optimize specific activities. Surprisingly, in the first dog, only 2.9% of injected radioactivity was recovered in bile and only 14.1% in urine, and the specific activities of the crystalline (3)H-UCB from the two pools were only 39.5 and 30.0 x 10(3) dpm/microg. High-performance liquid chromatography analysis revealed that only 4% of ALA degraded during 5 minutes in injection solution at pH 6.8. The low incorporation of (3)H-ALA and low specific activity of (3)H-UCB was apparently caused mainly by prior degradation and exchange of labile tritium of the (3)H-ALA and probably by enhanced endogenous ALA synthesis caused by the anesthetic/sedative agents. Revised procedures in the second dog improved the incorporation of (3)H-ALA to 11.9% excreted in bile and the specific activity of the crystalline (3)H-UCB to 122.0 and 50.8 x 10(3) dpm/microg, while urinary excretion of tritium increased to 28.5%. These experiences emphasize possible pitfalls in preparing (3)H-UCB by biosynthetic labeling from (3)H-ALA administered to dogs.

Ileal mucosal bile acid absorption is increased in Cftr knockout mice

BACKGROUND

Excessive loss of bile acids in stool has been reported in patients with cystic fibrosis. Some data suggest that a defect in mucosal bile acid transport may be the mechanism of bile acid malabsorption in these individuals. However, the molecular basis of this defect is unknown. This study examines the expression of the ileal bile acid transporter protein (IBAT) and rates of diffusional (sodium independent) and active (sodium dependent) uptake of the radiolabeled bile acid taurocholate in mice with targeted disruption of the cftr gene.

METHODS

Wild-type, heterozygous cftr (+/-) and homozygous cftr (-/-) mice were studied. Five one-cm segments of terminal ileum were excised, everted and mounted onto thin stainless steel rods and incubated in buffer containing tracer 3H-taurocholate. Simultaneously, adjacent segments of terminal ileum were taken and processed for immunohistochemistry and Western blots using an antibody against the IBAT protein.

RESULTS

In all ileal segments, taurocholate uptake rates were fourfold higher in cftr (-/-) and two-fold higher in cftr (+/-) mice compared to wild-type mice. Passive uptake was not significantly higher in cftr (-/-) mice than in controls. IBAT protein was comparably increased. Immuno-staining revealed that the greatest increases occurred in the crypts of cftr (-/-) animals.

CONCLUSIONS

In the ileum, IBAT protein densities and taurocholate uptake rates are elevated in cftr (-/-) mice > cftr (+/-) > wild-type mice. These findings indicate that bile acid malabsorption in cystic fibrosis is not caused by a decrease in IBAT activity at the brush border. Alternative mechanisms are proposed, such as impaired bile acid uptake caused by the thick mucus barrier in the distal small bowel, coupled with a direct negative regulatory role for cftr in IBAT function.

Systemic effects of acute terminal ileitis on uninflamed gut aggravate bile acid malabsorption

BACKGROUND

Some patients with terminal ileitis suffer from significant bile acid malabsorption even if the inflammation is locally limited. We hypothesized that inflammation in the terminal ileum may lead to changes in mucosal absorption in more proximal intestinal segments and aggravate bile acid malabsorption.

METHODS

Five hamsters underwent laparotomy and localized instillation of 2,4,6-trinitrobenzenesulfonic acid (TNBS) in 10% ethanol into the last 4 cm of ileum to create terminal ileitis. A control group (n = 5) underwent instillation of saline. Animals were sacrificed after 24 h. Active and passive transport of radiolabeled bile acids was measured in the proximal and terminal ileum and glucose absorption in the jejunum using an everted sleeve technique. Myeloperoxidase (MPO) activity and histomorphology were examined by standard methods.

RESULTS

In animals with ileitis, active bile acid uptake decreased by 84% in the terminal ileum (t test, P <0.001) and by 58% in the proximal ileum (P < 0.05) compared with saline-treated controls. Jejunal glucose absorption decreased by 59% (P < 0.01). Passive bile acid and glucose absorption rates were not significantly changed in any segments of treated animals versus controls. Histological examination of the treated group revealed signs of acute terminal ileitis without changes in the proximal ileum and jejunum. All control tissues were uninflamed. MPO activity was 13-fold increased in the inflamed ileal samples compared with controls (P <0.001). No significant changes were seen in the proximal ileum and jejunum. There was no evidence of reflux of TNBS into proximal ileum. Nominal mucosal surface area values showed no significant changes between groups. Pretreatment of an additional group of hamsters (n = 5) with acetylsalicylic acid before TNBS instillation ameliorated the inflammatory response in the terminal ileum and largely abrogated the negative effects on ileal bile acid absorption.

CONCLUSION

These data suggest that limited acute ileitis impairs active bile acid uptake in the terminal ileum. It also diminishes active bile acid and glucose absorption in more proximal segments of the small intestine, likely by a systemic effect. This systemic effect may aggravate bile acid malabsorption in patients with limited ileitis.

A simple method for measuring of intestinal solute transport in mucosal biopsy specimens

Accurate in vitro measurements of intestinal mucosal solute uptake in humans are often difficult because only small amounts of tissue material are available. We describe a miniaturized everted sleeve method of measuring intestinal solute uptake in endoscopy biopsy samples that combines simplicity, good tissue viability and reproducibility. Biopsies were mounted on a dressmaker needle head stationed immediately over a stirring bar rotating at 1200 rpm. This approach was used to measure taurocholate uptake in sheep and human endoscopy biopsies. Comparison was made to conventional standardized everted sleeve preparations. Na+-dependent uptake rates correlated well among individual sheep (R2 = 0.88, P < 0.05). There was excellent correlation between conventional and biopsy preparations in humans (R2 = 0.98; P < 0.05). The biopsy method overestimated diffusional uptake rates in sheep and humans by two to three fold when compared to conventional everted sleeve preparations. We conclude that this method is valuable to measure Na+-dependent solute uptake rates in biopsy samples from human intestine.

Percutaneous cholecystostomy for acute cholecystitis in veteran patients

BACKGROUND

Surgical cholecystostomy has been shown to carry a significantly higher mortality rate at Veterans Administration (VA) hospitals than at non-federal hospitals in the past.

METHODS

A retrospective outcomes study was undertaken at a large VA medical center with a policy favoring radiologic over surgical cholecystostomy over the past 9 years. Records of 24 consecutive patients with acute cholecystitis were reviewed to evaluate the effectiveness of the procedure.

RESULTS

Cholecystostomy was performed radiologically in 22 patients and surgically in 2 patients. Most (78%) of patients improved within 48 hours. The periprocedural mortality was 25%. The majority of these patients died from unrelated illnesses. Four patients developed complications, none of which required operative intervention.

CONCLUSIONS

Comorbidities are the most important mortality factor for cholecystostomies in VA patients. Radiologic tube placement is effective and uncomplicated in most cases.

Atypical gastrointestinal symptoms are not associated with gallstones in patients with spinal cord injury

OBJECTIVE

To determine if nonspecific gastrointestinal (GI) symptoms justify cholecystectomy in patients with spinal cord injury (SCI).

DESIGN

The frequency of GI symptoms was determined in a sample of patients with SCI in whom the presence or absence of gallstones had been previously determined by screening ultrasonography or a known history of cholecystectomy. The prevalence of various symptoms in patients with and without gallstones was compared.

SETTING

The Spinal Cord Injury Unit of the Veterans Affairs Puget Sound Health Care System, which provides rehabilitation and longitudinal primary care for SCI veterans.

PATIENTS

Two hundred ninety-four patients who had undergone either right upper quadrant ultrasonography or cholecystectomy in the past, and who completed a questionnaire concerning GI symptoms.

MAIN OUTCOME MEASURE

Bivariate logistic regression was used to calculate odds ratios (ORs) to determine the strength of associations between the presence of each symptom and the presence of gallstones.

RESULTS

Pain in the right upper quadrant or epigastrium that occurred after meals or at night was significantly associated with gallstones (OR: 3.5; 95% confidence interval [CI] 1.02-11.73). Abdominal pain in other locations and nonspecific symptoms such as bloating and nausea, were not predictive of the presence of gallstones.

CONCLUSIONS

Nonspecific symptoms in patients with SCI are not associated with gallstones and do not justify cholecystectomy in patients with otherwise asymptomatic gallstones.

Distribution of bile acid absorption and bile acid transporter gene message in the hamster ileum

The apical, Na-dependent, ileal bile acid transporter (IBAT) is critical for the reabsorption of bile acids in the ileum. Bile acid transport capacities as well as the distribution of bile acid transporter messenger ribonucleic acid (mRNA) and transporter protein were studied along the axis of the ileum. Na-dependent and Na-independent taurocholate uptake was measured in the hamster ileum using an everted-sleeve technique. The distribution of IBAT mRNA and protein were mapped by in-situ hybridization, immunohistochemistry, and Western blotting. Na-dependent and Na-independent bile acid uptake rates were highest 1-4 cm before the ileocecal valve (maxima 780 and 120 pmol/mm2 per min, respectively) and decreased proximally and distally. Na-independent absorption was increased in the last 6 cm of the ileum. IBAT mRNA and protein expression were linked closely to the distribution of uptake capacity. IBAT mRNA was more abundant near the crypt-villus junction whereas the protein was expressed evenly along the villus axis. We conclude that Na-dependent and Na-independent bile acid absorption capacities both have distinct distribution curves in the hamster ileum. All ileocytes on villi in the high-uptake area of the ileum express IBAT mRNA and protein.

[Surgery education in the USA]

Surgical education in the United States historically was influenced by the German educational system. Currently residents spend five years to become general surgeons. Education focuses on the teaching of surgical basic sciences and practical instruction in the operating room and at the bedside. Students interested in General Surgery are selected largely based on their performance in medical school. Admission into first-rate programs is highly competitive. In many university-based programs residents are expected to spend an additional two years in research as part of their training. While on their clinical rotations residents usually spend 80 to 100 hours per week in the hospital. Resident salaries are moderate.

The presentation of gallstones and results of biliary surgery in a spinal cord injured population

BACKGROUND

Since spinal cord injured patients lack visceral sensation, their clinical manifestations of gallstones could be relatively occult. A higher proportion of these individuals may present with advanced biliary disease compared with the general population. Prophylactic cholecystectomy for asymptomatic stones may therefore be justified.

METHODS

All spinal cord injured patients seen at the Seattle Veterans Hospital over a 5-year period were retrospectively surveyed to define a set of patients who had undergone a cholecystectomy. The operative indications and results were compared with those from a series of cholecystectomies in neurologically intact patients.

RESULTS

The presentation of biliary disease in spinal cord injured patients was not more advanced than that of neurologically intact patients. Patients with high cord injuries presented in a similar fashion to those with low injuries.

CONCLUSIONS

Since most spinal cord injured patients with biliary disease present with typical findings, prophylactic removal of gallstones in these patients is not warranted.

[Telesurgery--experiences from the USA]

Recent advances in telecommunications formed the basis for studies on the use of video and high resolution television for surgical teleconsulting. Experience from hospitals of the American Veterans Administration suggests the technology to be a valuable asset. Telesurgical techniques improve health care in remote areas, save costs by reducing the need for transfers, and ease the professional isolation of health care personnel. Clear recommendations for both primary care and referral centers about how to conduct telesurgical consulting are given in the text.

Colonic perforations after renal transplantation

BACKGROUND

Perforation of the colon is a rare but serious complication in renal transplantation; allograft recipients constitute a patient population uniquely at risk with end-stage renal failure, maintenance therapy with dialysis before transplantation, and then chronic immunosuppression thereafter.

STUDY DESIGN

In 1,401 consecutive transplants performed between 1951 and 1995 at the Brigham and Women's Hospital, 30 recipients (2.1 percent) experienced 34 episodes of colonic perforations, 13 of which (38 percent) were fatal. The medical records and clinic charts of each person were analyzed for variables between those who survived and those who died of the colon perforation.

RESULTS

Significant differences in patient demography and clinical and laboratory findings including age, mean corticosteroid dose, and nutritional status were noted between the two groups. Early diagnosis and intervention improved the prognosis; 22 percent of those operated on within 24 hours died; 47 percent died after delayed intervention. Excision of the lesion with end-to-end anastomosis was effective in most right colon perforations, and removal of the lesion and formation of an end-colostomy and Hartmann pouch was preferred in rectosigmoid perforations. The incidence and outcome of posttransplant colonic perforations were associated with the intensity of immunosuppression, with 28 percent of perforations occurring within the first month after engraftment and 47 percent within the first 3 months; the mean daily dose of corticosteroids was three times higher in those who died compared with those who survived. The levels of serum albumin were significantly lower among nonsurvivors.

CONCLUSIONS

Colon perforation is a catastrophic event in immunosuppressed renal transplant recipients. Prompt diagnosis and treatment are critical; because of the masking effects of corticosteroids on symptoms and signs, a high index of suspicion and urgent investigation are indicated. Prompt surgical intervention and attention to the nutritional status are essential for survival.

The neuronal and epithelial human high affinity glutamate transporter. Insights into structure and mechanism of transport

High affinity transport of glutamate across plasma membranes of brain neurons and epithelial is mediated by a Na(+)- and K(+)-coupled electrogenic transporter. Here we report the primary structure and functional characterization of the human high affinity glutamate transporter (HEAAC1). A unique characteristic of HEAAC1-mediated transport is that the affinity for glutamate and the maximal transport rate are strongly dependent on membrane potential. Our data provide new insights into individual steps of high affinity glutamate transport and show that the transport mechanism is distinct from that of the gamma-aminobutyric acid transporter GAT-1 and the Na+/glucose transporter SGLT1. Under voltage clamp condition, HEAAC1 mediated large substrate-evoked inward currents (up to 1 microA). The substrate specificity, stereospecificity, the Km value (30 +/- 3 microM at -60 mV) of the L-glutamate-evoked current, and Northern analysis all agree with previously reported characteristics of high affinity glutamate transport in brain. In contrast to SGLT1 and GAT-1, voltage jump studies of HEAAC1 yielded only minor relaxation currents. Classic inhibitors of brain glutamate uptake such as DL-threo-beta-hydroxyaspartate, L-trans-pyrrolidine 2,4,-dicarboxylic acid (PDC), and dihydrokainate were found to be either transport substrates or to have no significant effect on glutamate transport. We also found that the maximal transport rate for PDC was markedly reduced compared to that for L-glutamate. We propose that PDC most likely reduces the turnover rate of the transporter. A search of the sequence data bases revealed weak homology of HEAAC1 to the H(+)-coupled vesicular monoamine transporter, suggesting an evolutionary link between plasma membrane and vesicular transporters.