Cold preservation of the human colon and ileum with University of Wisconsin solution

Translational neuropharmacology: the use of human isolated gastrointestinal tissues

Translational sciences increasingly emphasize the measurement of functions in native human tissues. However, such studies must confront variations in patient age, gender, genetic background and disease. Here, these are discussed with reference to neuromuscular and neurosecretory functions of the human gastrointestinal (GI) tract. Tissues are obtained after informed consent, in collaboration with surgeons (surgical techniques help minimize variables) and pathologists. Given the difficulties of directly recording from human myenteric neurones (embedded between muscle layers), enteric motor nerve functions are studied by measuring muscle contractions/relaxations evoked by electrical stimulation of intrinsic nerves; responses are regionally dependent, often involving cholinergic and nitrergic phenotypes. Enteric sensory functions can be studied by evoking the peristaltic reflex, involving enteric sensory and motor nerves, but this has rarely been achieved. As submucosal neurones are more accessible (after removing the mucosa), direct neuronal recordings are possible. Neurosecretory functions are studied by measuring changes in short-circuit current across the mucosa. For all experiments, basic questions must be addressed. Because tissues are from patients, what are the controls and the influence of disease? How long does it take before function fully recovers? What is the impact of age- and gender-related differences? What is the optimal sample size? Addressing these and other questions minimizes variability and raises the scientific credibility of human tissue research. Such studies also reduce animal use. Further, the many differences between animal and human GI functions also means that human tissue research must question the ethical validity of using strains of animals with unproved translational significance.

Metabolic, Coagulative, and Hemodynamic Changes During Intestinal Transplant: Good Predictors of Postoperative Damage?

BACKGROUND

Analysis of intraoperative changes of metabolic, hemodynamic, and coagulative parameters is useful to detect early ischemia-reperfusion damage after intestinal transplant.

METHODS

The objective of our study is to correlate the histological damage at the end of transplant in relation to the intraoperative changes after reperfusion. The histological aspect was graded according to Park's classification at the end of the surgical procedure with biopsies of the graft. Patients were divided into two groups according to the presence or absence of histological damage of the small bowel wall: group A (normal mucosa/minimal damage: Park's grades 0-1) and group B (mucosal damage: Park's grades 2-8).

RESULTS

Significant hemodynamic, metabolic, and coagulative disorders were observed in group B. Consequently, these disorders are thought to be early indicators of graft damage.

CONCLUSIONS

Actual monitoring procedures used for postoperative graft surveillance remain paramount in detecting postoperative intestinal dysfunction, but the indicators described in this paper could represent a further help in intraoperative and postoperative management.

Therapeutic effects of xanthine oxidase inhibitors: renaissance half a century after the discovery of allopurinol

The prototypical xanthine oxidase (XO) inhibitor allopurinol, has been the cornerstone of the clinical management of gout and conditions associated with hyperuricemia for several decades. More recent data indicate that XO also plays an important role in various forms of ischemic and other types of tissue and vascular injuries, inflammatory diseases, and chronic heart failure. Allopurinol and its active metabolite oxypurinol showed considerable promise in the treatment of these conditions both in experimental animals and in small-scale human clinical trials. Although some of the beneficial effects of these compounds may be unrelated to the inhibition of the XO, the encouraging findings rekindled significant interest in the development of additional, novel series of XO inhibitors for various therapeutic indications. Here we present a critical overview of the effects of XO inhibitors in various pathophysiological conditions and also review the various emerging therapeutic strategies offered by this approach.

Luminal contact with University of Wisconsin solution improves human small bowel preservation

AIM

Under clinical conditions small bowel mucosa is stored without any contact between the mucosa and the preservation solution. We evaluated the impact of luminal contact with University of Wisconsin solution (UW) on the structural quality of small bowel preservation.

METHODS

Segments of ileum harvested from stable multi-organ donors were flushed with UW. For each donor, ileal segments were placed in UW without any contact between the mucosa and the preservation solution (group A), as is practiced in clinical conditions. Adjacent segments were cut on their antimesenteric side and placed in UW so that their mucosa was widely in contact with the solution (group B). The grafts preserved in ice were removed from the preservation fluid at different times (0, 3, 6, or 12 hours). Tissues were studied by optical microscopy after H&E staining of formalin-fixed, paraffin-embedded specimens. A median histologic score was calculated after examination of three random slides for each ileal segment per time point. Comparisons were performed between tissues of groups A and B from the same donor.

RESULTS

Control (0h) specimens showed normal histology. As early as 3 hours of preservation, group A tissues showed detachment of the villar epithelium. At 6 and 12 hours of preservation in this group further tissue alteration were obvious with complete epithelial detachment from the basal membrane of the villi. The histologic score of the segments preserved by luminal contact with UW was always significantly higher than the controls from the same donor.

CONCLUSION

Luminal contact between the mucosa of intestinal grafts and UW improves the quality of human small bowel preservation.

A new model for human intestinal preservation: comparison of University of Wisconsin and Celsior preservation solutions

AIM

We compared University of Wisconsin (UW) and Celsior preservation solutions using a new model of human intestinal preservation that mimics the clinical conditions of small bowel procurement.

METHODS

Intestinal grafts were harvested from four multiorgan donors. After classic warm dissection for organ procurement, an ileal segment of 50 cm was immediately flushed with Celsior. After the perfusion of the abdominal organs with UW, a second segment of adjacent ileum was harvested. The two intestinal grafts were then divided into segments by stapling, before immersion into the corresponding preservation solution (Celsior or UW) for 0-, 6-, 12-, or 24-hour incubation at 4 degrees C. A histological score was graded after blinded examination of three random specimens within each ileal graft for each duration of preservation.

RESULTS

Control specimens showed normal histology. After 6 hours of preservation, most villi showed complete epithelial detachment although the crypts appeared intact. After 12 hours of preservation, a larger proportion of the villi showed extensive epithelial sloughing. After 24 hours, the damage involved the entire mucosa with the crypt epithelium largely detached from the basal membrane. No statistical difference in histological score was observed between the two preservation solutions.

CONCLUSION

This study showed severe histological alterations of graft mucosa after short periods of preservation by UW or Celsior solutions. This model may be useful to evaluate improvements in the quality of preservation of human intestinal transplants.

In vitro and in situ experimental model for X-ray microanalysis of intestinal epithelium

Intestinal chloride (Cl) transport is disturbed in a number of diseases. X-ray microanalysis can be used to study the distribution of Cl and other ions in intestinal epithelial cells. In this study it was attempted to establish an experimental system that retains the in vivo elemental composition of intestinal epithelial cells. An in vitro system was set up in which a segment of rat intestine was mounted in a bath and perfused with different fluids. The chloride in the bath or in the perfusion fluid could be exchanged for gluconate or bromide to determine the direction of chloride fluxes. An in situ system was set up in which the animal was anesthetized and a segment of the intestine was perfused with different solutions. In the in vitro experiments the concentration of Na and Cl in the epithelial cells increased and that of K decreased. These changes occurred within the first 30 minutes of incubation. Uptake of chloride occurred mainly from the bath, as seen in experiments where bromide was used as a chloride analog. The concentration gradient between bath and tissue determined the extent of chloride uptake. Addition of glucose to the perfusion fluid and bath did not improve the results. In the in situ system, preservation of the intracellular ion composition was better. Acceptable results were obtained with perfusion with Krebs-Ringer's buffer without glucose for 30 minutes. In this case, the elemental content of the cell did not change appreciably during incubation. If glucose was added, the Na concentration increased in comparison to the control, both in crypt and villus cells. It is concluded that the intestinal epithelium is a sensitive system, very prone to disturbance of its homeostasis. However, the in situ system can be used in studies of agonist-induced ion transport.

The type of sodium-coupled solute modulates small bowel mucosal injury, transport function, and ATP after ischemia/reperfusion injury in rats

BACKGROUND & AIMS

Gastrointestinal function may be impaired after severe injury, hampering tolerance to enteral nutrition. The purpose of this study was to determine how different sodium-coupled solutes modulate gut function after ischemia/reperfusion (I/R) in a rodent model.

METHODS

At laparotomy, rats had jejunal sacs filled with (glucose + alanine), glucose, glutamine, alanine, or mannitol (osmotic control), followed by superior mesenteric artery clamping for 60 minutes and 30 minutes of reperfusion. After reperfusion, sacs were harvested for morphologic examination, adenosine triphosphate (ATP) assay, or mounted in an Ussing chamber.

RESULTS

Small intestinal epithelial absorptive capacity, as assessed by changes in short-circuit current in response to glucose, after gut I/R, was decreased by alanine or (glucose + alanine) but not glucose or glutamine alone and correlated with changes in tissue ATP. Gut I/R caused a significant morphologic injury that was worsened by alanine or (glucose + alanine) but lessened by glucose or glutamine alone.

CONCLUSIONS

During gut I/R, alanine can enhance gut injury, deplete energy (ATP), and impair gut absorption, whereas glucose or glutamine is protective against injury and can maintain absorptive capacity and ATP. These results suggest that solutes (such as alanine), which further stress an already metabolically stressed bowel, should be cautiously administered to critically ill patients whereas those solutes that contribute to energy production (such as glucose and glutamine) may be safely continued.