Luminal preservation of rat small intestine with University of Wisconsin or Celsior solution

The Effects of Rapamycin on the Intestinal Graft in a Rat Model of Cold Ischemia Perfusion and Preservation

Attenuating the rheological and structural consequences of intestinal ischemia-reperfusion-injury (IRI) is important in transplant proceedings. Preconditioning is an often-proposed remedy. This technique uses physical or pharmacological methods to manipulate key ischemia pathways, such as oxidation, inflammation, and autophagy, prior to ischemia. This study determined the time-dependent effects of Rapamycin preconditioning on small-bowel grafts undergoing cold ischemia perfusion and preservation. Our main parameters were mucosa and cell injury and autophagy. A total of 30 male Wistar rats were divided into 5 groups: sham, preservation-control, and 3 treated groups (Rapamycin administered either 0, 30, or 60 min prior to perfusion). After perfusion, the intestines were placed in chilled IGL-1 solution for 12 h. Thereafter, they were reperfused. Histology and bioanalysis (LDH and lactate) were used to ascertain intestinal injury while immunohistochemistry was used for measuring changes in autophagy markers (Beclin-1, LC3B, and p62 proteins). The results show no significant difference amongst the groups after vascular perfusion. However, intestinal injury findings and autophagy changes demonstrate that administering Rapamycin 30 min or 60 min prior was protective against adverse cold ischemia and reperfusion of the intestinal graft. These findings show that Rapamycin is protective against cold ischemia of the small intestine, especially when administered 30 min before the onset.

Characterizing Autophagy in the Cold Ischemic Injury of Small Bowel Grafts: Evidence from Rat Jejunum

Cold ischemic injury to the intestine during preservation remains an unresolved issue in transplantation medicine. Autophagy, a cytoplasmic protein degradation pathway, is essential for metabolic adaptation to starvation, hypoxia, and ischemia. It has been implicated in the cold ischemia (CI) of other transplantable organs. This study determines the changes in intestinal autophagy evoked by cold storage and explores the effects of autophagy on ischemic grafts. Cold preservation was simulated by placing the small intestines of Wistar rats in an IGL-1 (Institute George Lopez) solution at 4 °C for varying periods (3, 6, 9, and 12 h). The extent of graft preservation injury (mucosal and cellular injury) and changes in autophagy were measured after each CI time. Subsequently, we determined the differences in apoptosis and preservation injury after activating autophagy with rapamycin or inhibiting it with 3-methyladenine. The results revealed that ischemic injury and autophagy were induced by cold storage. Autophagy peaked at 3 h and subsequently declined. After 12 h of storage, autophagic expression was reduced significantly. Additionally, enhanced intestinal autophagy by rapamycin was associated with less tissue, cellular, and apoptotic damage during and after the 12-h long preservation. After reperfusion, grafts with enhanced autophagy still presented with less injury. Inhibiting autophagy exhibited the opposite trend. These findings demonstrate intestinal autophagy changes in cold preservation. Furthermore, enhanced autophagy was protective against cold ischemia-reperfusion damage of the small bowels.

Luminal polyethylene glycol solution delays the onset of preservation injury in the human intestine

The organ damage incurred during the cold storage (CS) of intestinal grafts has short and long-term consequences. Animal studies suggest that additional luminal preservation (LP) with polyethylene glycol (PEG) may alleviate this damage. This study aims to validate these findings using human intestines. Ileal segments, perfused intravascularly with IGL-1 solution, were procured from 32 multiorgan donors and divided into two parts: one containing a PEG 3350-based solution introduced luminally (LP group) and another one without luminal treatment (control). Sampling was performed after 4 h, 8 h, 14 h, and 24 h of CS. Histology was assessed using the Chiu/Park score. Tight junctions (TJ), several inflammatory markers, and transcription factors were examined by immunofluorescence, ddPCR, and western blot. Tissue water content (edema) was also measured. Apoptotic activity was assessed with caspase -2, -3, and -9 assays. LP significantly lowered mucosal injury at all time points. Redistribution of TJ proteins occurred earlier and more severely in the control group. After 24 h of CS, LP intestines showed an emerging unfolding protein response. Increased caspase-3 and -9 activity was found in the control group. The current results indicate that luminal PEG is safe and effective in reducing damage to the intestinal epithelium during CS.

A novel histidine-tryptophan-ketoglutarate formulation ameliorates intestinal injury in a cold storage and ex vivo warm oxygenated reperfusion model in rats

AIM

The present study aims to evaluate protective effects of a novel histidine-tryptophan-ketoglutarate solution (HTK-N) and to investigate positive impacts of an additional luminal preservation route in cold storage-induced injury on rat small bowels.

METHODS

Male Lewis rats were utilized as donors of small bowel grafts. Vascular or vascular plus luminal preservation were conducted with HTK or HTK-N and grafts were stored at 4°C for 8 h followed by ex vivo warm oxygenated reperfusion with Krebs-Henseleit buffer for 30 min. Afterwards, intestinal tissue and portal vein effluent samples were collected for evaluation of morphological alterations, mucosal permeability and graft vitality.

RESULTS

The novel HTK-N decreased ultrastructural alterations but otherwise presented limited effect on protecting small bowel from ischemia-reperfusion injury in vascular route. However, the additional luminal preservation led to positive impacts on the integrity of intestinal mucosa and vitality of goblet cells. In addition, vascular plus luminal preservation route with HTK significantly protected the intestinal tissue from edema.

CONCLUSION

HTK-N protected the intestinal mucosal structure and graft vitality as a luminal preservation solution. Additional luminal preservation route in cold storage was shown to be promising.

Luminal preloading with hydrogen-rich saline ameliorates ischemia-reperfusion injury following intestinal transplantation in rats

Prolonged intestinal cold storage causes considerable mucosal breakdown, which could bolster bacterial translocation and cause life-threatening infection for the transplant recipient. The intestine has an intraluminal compartment, which could be a target for intervention, but has not yet been fully investigated. Hydrogen gas exerts organ protection and has used been recently in several clinical and basic research studies on topics including intestinal transplantation. In this study, we aimed to investigate the cytoprotective efficacy of intraluminally administered hydrogen-rich saline on cold IR injury in intestinal transplantation. Isogeneic intestinal transplantation with 6 hours of cold ischemia was performed on Lewis rats. Hydrogen-rich saline (H₂ concentration at 5 ppm) or normal saline was intraluminally introduced immediately before preservation. Graft intestine was excised 3 hours after reperfusion and analyzed. Histopathological analysis of control grafts revealed blunting of the villi and erosion. These mucosal changes were notably attenuated by intraluminal hydrogen. Intestinal mucosa damage caused by IR injury led to considerable deterioration of gut barrier function 3 h post-reperfusion. However, this decline in permeability was critically prevented by hydrogen treatment. IR-induced upregulation of proinflammatory cytokine mRNAs such as IL-6 was mitigated by hydrogen treatment. Western blot revealed that hydrogen treatment regulated loss of the transmembrane protein ZO-1. Hydrogen-rich saline intraluminally administered in the graft intestine modulated IR injury to transplanted intestine in rats. Successful abrogation of intestinal IR injury with a novel strategy using intraluminal hydrogen may be easily clinically applicable and will compellingly improve patient care after transplantation.

Extracorporeal Hypothermic Perfusion Device for Intestinal Graft Preservation to Decrease Ischemic Injury During Transportation

INTRODUCTION

The small intestine is one of the most ischemia-sensitive organs used in transplantation. To better preserve the intestinal graft viability and decrease ischemia-reperfusion injury, a device for extracorporeal perfusion was developed. We present the results for the first series of perfused human intestine with an intestinal perfusion unit (IPU).

METHODS

Five human intestines were procured for the protocol. (1) An experimental segment was perfused by the IPU delivering cold preservation solution to the vascular and luminal side continually at 4 ºC for 8 h. (2) Control (jejunum and ileum) segments were preserved in static cold preservation. Tissue samples were obtained for histopathologic grading according to the Park/Chiu scoring system (0 = normal, 8 = transmural infarction).

RESULTS

Jejunal experimental segments scored 2.2 with the Park/Chiu system compared to the control segments, which averaged 3.2. Overall scoring for ileum experimental and control segments was equal with 1.6.

CONCLUSION

This data presents proof of concept that extracorporeal intestinal perfusion is feasible. The evidence shows that the IPU can preserve the viability of human intestine, and histopathologic evaluation of perfused intestine is favorable. Our early results can eventually lead to expanding the possibilities of intestinal preservation.

Lifor Solution: An Alternative Preservation Solution in Small Bowel Transplantation

Background and Objectives. The intestinal mucosa is extremely sensitive to ischemia. Better intestinal preservation is the first step to improve the results of intestinal transplantation. The aim of the study is to investigate the effect of cold Lifor solution on preservation of swine small bowel. Methods. Swine ileum segments (200 cm) were allotransplanted heterotopically after 9-hour cold storage with UW solution (group 1, n = 6), with Lifor solution (group 2, n = 6), or without storage (group 3, n = 6), respectively. After cold storage, mucosal adenosine triphosphate (ATP) concentrations and histopathologic analysis after preservation were performed. At day 7 after the transplantation, intestinal absorptive function was also observed. Results. After 9 h cold preservation, pathological changes, the content of ATP in the intestinal mucosa, and the intestinal absorptive function after transplantation in group 2 were similar to those of group 1. Conclusion. The effect of cold storage of swine small bowel with Lifor solution is similar to that of UW solution. It may provide additional rationale for further exploration of Lifor as an alternative preservation solution in small bowel transplantation.

The application of polymerized porcine hemoglobin (pPolyHb) in the rat small bowel preservation

Small bowel transplantation (SBTx) has become a standard clinical treatment for short bowel syndrome or irreversible intestinal function failure. Optimum preservation of the organ is essential for the success of transplantation. In this study, pPolyHb was used as an additive to hypertonic citrate adenine solution (HCA) to provide oxygen for rat small bowel transplant. Rat small bowels were preserved in HCA, HCA with pPolyHb, and University of Wisconsin solution (UW) for 12, 24, and 36 h, respectively. The results suggested that the preservation effect of HCA with pPolyHb was comparable with the UW solution, and more effective than the HCA solution.

Organ-specific solutions and strategies for the intestinal preservation

Among the intraabdominal organs, the intestine is the most susceptible to storage injury and as a consequence its safe cold ischemic time in the clinic is restricted to below 10 hours. The current practice for the intestinal preservation (IP) consists of an in-situ vascular flush with iced University of Wisconsin or Histidine-Tryptophan-Ketoglutarate solution followed by cold storage at 4°C. Mucosal injury is initiated within 1 hour and rapidly progresses to mucosal breakdown; tissue injury worsens upon reperfusion and further impairs the mucosal barrier, favoring bacterial translocation and sepsis. In addition of releasing danger signals, an advanced ischemia-reperfusion injury (IRI) may increase graft immunogenicity and promote rejection. Several alternative approaches have been tested as alternatives to the static storage. The aim of this review is to summarize and discuss the various intraluminal interventions as additional strategies aiming to reduce the IP/reperfusion injury and highlight the underlying pathophysiological mechanisms.

Small bowel preservation for intestinal transplantation: a review

Intestinal transplantation has become the therapy of choice for patients with intestinal failure and life-threatening complications from total parenteral nutrition. Results, however, remain inferior as compared with other transplant types with the quality of the organ graft as the most important factor of outcome after transplantation. The intestine is extremely sensitive to ischemia. Unfortunately, a relatively long ischemic preservation period is inevitable. The current standard in organ preservation [cold storage (CS) with University of Wisconsin solution] was developed for kidney/liver preservation and is suboptimal for the intestinal graft despite good results for other organs. This review aimed at appraising the results from the use of previously applied and recently developed preservation solutions and techniques to identify key areas for improvement. As the studies available do not reveal the most effective method for intestinal preservation, an optimal strategy will result from a synergistic effect of different vital elements identified from a review of published material from the literature. A key factor is the composition of the solution using a low-viscosity solution to facilitate washout of blood, including amino acids to improve viability, impermeants and colloids to prevent edema, and buffer for pH-homeostasis. Optimizing conditions include a vascular flush before CS and luminal preservation. The most effective composition of the luminal solution and a practical, clinically applicable optimal technique are yet to reach finality. Short-duration oxygenated arterial and/or luminal perfusion have to be considered. Thus, a tailor-made approach to luminal preservation solution and technique need further investigation in transplant models and the human setting to develop the ultimate technique meeting the physiologic demands of the intestinal graft during preservation.

Influence of PACAP on oxidative stress and tissue injury following small-bowel autotransplantation

Tissue injury caused by cold preservation and reperfusion remains an unsolved problem during small-bowel transplantation. Pituitary adenylate cyclase-activating polypeptide (PACAP) is present and plays a central role in the intestinal physiology. This study investigated effect of PACAP-38 on the oxidative stress and tissue damage in autotransplanted intestine. Sham-operated, ischemia/reperfusion, and autotransplanted groups were established in Wistar rats. In ischemia/reperfusion groups, 1 h (group A), 2 h (group B), and 3 h (group C) ischemia followed by 3 h of reperfusion was applied. In autotransplanted groups, total orthotopic intestinal autotransplantation was performed. Grafts were preserved in University of Wisconsin (UW) solution and in UW containing 30 microg PACAP-38 for 1, 2, 3, and 6 h. Reperfusion lasted 3 h in all groups. Endogenous PACAP-38 concentration was measured by radioimmunoassay. To determine oxidative stress parameters, malondialdehyde, reduced glutathione, and superoxide dismutase were measured in tissue samples. Tissue damage was analyzed by qualitative and quantitative methods on hematoxylin/eosin-stained sections. Concentration of endogenous PACAP-38 significantly decreased in groups B and C compared to sham-operated group. Preservation solution containing PACAP-38 ameliorated bowel tissue oxidative injury induced by cold ischemia and reperfusion. Histological results showed that preservation caused destruction of the mucous, submucous, and muscular layers, which were further deteriorated by the end of reperfusion. In contrast, PACAP-38 significantly protected the intestinal structure. Ischemia/reperfusion decreased the endogenous PACAP-38 concentration in the intestinal tissue. Administration of PACAP-38 mitigated the oxidative injury and histological lesions in small-bowel autotransplantation model.

Experimental small bowel preservation using Polysol: A new alternative to University of Wisconsin solution, Celsior and histidine-tryptophan-ketoglutarate solution?

AIM: To evaluate the potential of Polysol, a newly developed preservation solution, in cold storage of small bowel grafts, compared with the current standards, University of Wisconsin solution (UW), Celsior and histidine-tryptophan-ketoglutarate solution (HTK).

METHODS: Male Wistar rats were used as donors. Small bowels were retrieved, flushed and then stored in the respective 4 solutions for 18 h at 4°C. Functional integrity of the grafts was evaluated by isolated reperfusion with oxygenated Krebs-Henseleit buffer at 37°C for 30 min in all 4 groups.

RESULTS: Polysol preservation exhibited the highest tissue ATP concentration and the lowest release of LDH. Malondialdehyde, an index for tissue lipid peroxidation, was also the lowest in Polysol. Tissue oxygen consumption was significantly higher in Polysol than in the others. Of interest, UW-storage promoted 10-fold higher apoptosis than in the others. Moreover, electron microscopy revealed that the mucosal villi/micro-villi formation and the cell organelles, including mitochondria, were both significantly better preserved in Polysol, while deleterious alterations were apparent in the others, most notably in UW. Although Celsior and HTK exhibited the better trend of results than UW in some parameters, but could not reach the over-all superiority to UW.

CONCLUSION: Cold storage using Polysol resulted in significantly better integrity and function of small bowel grafts than UW. Hence, Polysol may be a novel alternative for the small bowel preservation.