Intestinal preservation for transplantation: current status and alternatives for the future

Comparison of the effects of normothermic machine perfusion and cold storage preservation on porcine intestinal allograft regenerative potential and viability

Intestinal transplantation (IT) is the final treatment option for intestinal failure. Static cold storage (CS) is the standard preservation method used for intestinal allografts. However, CS and subsequent transplantation induce ischemia-reperfusion injury (IRI). Severe IRI impairs epithelial barrier function, including loss of intestinal stem cells (ISC), critical to epithelial regeneration. Normothermic machine perfusion (NMP) preservation of kidney and liver allografts minimizes CS-associated IRI; however, it has not been used clinically for IT. We hypothesized that intestine NMP would induce less epithelial injury and better protect the intestine's regenerative ability when compared with CS. Full-length porcine jejunum and ileum were procured, stored at 4 °C, or perfused at 34 °C for 6 hours (T6), and transplanted. Histology was assessed following procurement (T0), T6, and 1 hour after reperfusion. Real-time quantitative reverse transcription polymerase chain reaction, immunofluorescence, and crypt culture measured ISC viability and proliferative potential. A greater number of NMP-preserved intestine recipients survived posttransplant, which correlated with significantly decreased tissue injury following 1-hour reperfusion in NMP compared with CS samples. Additionally, ISC gene expression, spheroid area, and cellular proliferation were significantly increased in NMP-T6 compared with CS-T6 intestine. NMP appears to reduce IRI and improve graft regeneration with improved ISC viability and proliferation.

Luminal Preservation Protects the Small Intestine in a Brain-dead Rat Model

Intestinal transplantation depends on donation after brain death (DBD). Luminal preservation (LP) has been beneficial against preservation injury in previous studies in animal models, but none include DBD. This study aims to investigate whether these benefits occur also with DBD.

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.

Potential options to expand the intestinal donor pool: a comprehensive review

PURPOSE OF REVIEW

Intestinal donation is currently restricted to 'perfect' donors, as the intestine is extremely vulnerable to ischemia. With generally deteriorating donor quality and increasing indications for intestinal transplantation (ITx), the potential to safely increase the donor pool should be evaluated.

RECENT FINDINGS

Increasing awareness on intestinal donation (often forgotten) and cautiously broadening the strict donor criteria (increasing age, resuscitation time and ICU stay) could expand the potential donor pool. Donors after circulatory death (DCD) have so far not been considered for ITx, due to the particularly detrimental effect of warm ischemia on the intestine. However, normothermic regional perfusion might be a well tolerated strategy to render the use of DCD intestinal grafts feasible. Furthermore, machine perfusion is under continuous development and might improve preservation of the intestine and potentially offer a platform to modulate the intestinal graft. Lastly, living donation currently represents only a minority of all ITxs performed worldwide. Various studies and registry analysis show that it can be performed safely for the donor and successfully in the recipient.

SUMMARY

Several potential strategies are available to expand the current intestinal donor pool. Most of them require further investigation or technical developments before they can be implemented in the clinical routine.

Experimental study to assess the impact of vasopressors administered during maintenance of the brain-dead donation in the quality of the intestinal graft

BACKGROUND

The hemodynamic maintenance of brain-dead donors will influence the quality of the organs procured for transplantation, including the intestine. Although norepinephrine (NE) and dopamine (DA) are commonly used to sustain mean arterial pressure in humans, there are no standardized protocols for their use during maintenance of brain-dead donors. Our aim was to compare the effects of each drug, in the intestinal graft quality using a rat brain-dead donation model.

METHODS

Wistar rats (N = 17) underwent brain death (BD) for 2 hours with NE (NE group) or with DA (DA group) administration; the control group was mechanically ventilated for 2 hours without BD. Jejunum biopsies were obtained at the end of the maintenance period. Histological damage was evaluated using Park-Chiu scale. Villi/crypt ratio, mucosal thickness, Goblet cell count, and villi density were evaluated using ImageJ software (US National Institutes of Health, Bethesda, MD). Barrier damage was assessed by bacterial translocation culture counting on liver samples. The inflammatory status of the intestine was evaluated by CD3+ counting by immunohistochemistry and gene expression analysis of interleukin (IL)-6, IL-22, and CXCL10.

RESULTS

Norepinephrine-treated donors had higher focal ischemic injury in the intestinal mucosa without a substantial modification of morphometrical parameters compared with DA-treated donors. CD3+ mucosal infiltration was greater in intestines procured from brain-dead donors, being highest in NE (p ˂ 0.001). Local inflammatory mediators were affected in BD: DA and NE groups showed a trend to lower expression of IL-22, whereas CXCL10 expression was higher in NE versus control group. Brain death promoted intestinal bacterial translocation, but the use of NE resulted in the highest bacterial counting in the liver (p ˂ 0.01).

CONCLUSION

Our results favor the use of DA instead of NE as main vasoactive drug to manage BD-associated hemodynamic instability. Dopamine may contribute to improve the quality of the intestinal graft, by better preserving barrier function and lowering immune cell infiltration.

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.

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.

Hydrogel-based 3D bioprints repair rat small intestine injuries and integrate into native intestinal tissue

3D Printing has become a mainstay of industry, with several applications in the medical field. One area that could benefit from 3D printing is intestinal failure due to injury or genetic malformations. We bioprinted cylindrical tubes from rat vascular cells that were sized to form biopatches. 2 mm enterotomies were made in the small intestine of male Sprague-Dawley rats, and sealed with biopatches. These intestinal segments were connected to an ex vivo perfusion device that provided independent extraluminal and intraluminal perfusion. The fluorescence signal of fluorescein isothiocyanate (FITC)-inulin in the intraluminal perfusate, a non-absorbable fluorescent marker of intestinal integrity, was measured every 15 min over 90 min, and used to assess the integrity of the segments under both continuous perfusion and alternate-flow perfusion. Enterotomies were made an inch away from the ileocecal junction in male Wistar rats and sealed with biopatches. The animals were monitored daily and euthanized at post-operative days 7, 14, 21, and 30. Blinded histopathological analysis was conducted to compare the patch segments to native intestine. Biopatch-sealed intestinal segments withstood both continuous and pulsatile flow rates without leakage of FITC-inulin above the control baseline. 21 of 26 animals survived with normal activity, weight gain, and stool output. Histopathology of the explanted segments showed progressive villi and crypt formation over the enterotomies, with complete restoration of the epithelium by 30 days. This study presents a novel application of 3D bioprinting to develop a universal repair patch that can seal lesions in vivo, and fully integrate into the native intestine.

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.

The Impact of Age and Luminal Preservation on the Development of Intestinal Preservation Injury in Rats

BACKGROUND

Organs from older donors are believed to withstand ischemia worse than those from younger donors. The effect of age on the development of intestinal preservation injury (IPI) is unclear.

METHODS

We compared the development of IPI in intestines from young (3 mo), adult (14 mo), and old (20 mo) rat donors and assessed if luminal preservation (LP) is effective in delaying IPI. Small intestines were perfused with, and stored in, preservation solution (Custodiol) with or without LP solution (polyethylene glycol 3350). IPI was studied using histology (Chiu score, Alcian blue staining), Western blot, and electrophysiological assessment (Ussing chamber) at 4, 8, and 14 hours.

RESULTS

Intestines of old rats did not show major histological alterations, whereas their aortas and kidneys revealed typical age-related changes (arteriosclerosis and glomerulosclerosis). Intestines from old rats fared similarly to their younger counterparts at all time points regarding preservation injury and goblet cells count. Intestines undergoing LP showed fewer histological signs of damage and higher goblet cells count when compared with samples without LP, regardless of donor age. Ussing chamber experiments indicated a time-dependent deterioration of all parameters studied, which was delayed by the use of LP.

CONCLUSIONS

Older intestines did not convincingly demonstrate a faster IPI compared with intestines from adult and young donors. The small differences between the age groups were nullified by the use of LP. LP significantly delayed the IPI in all age groups and may allow for longer preservation periods without an increased risk of mucosal damage.

Human Small Intestine Transplantation: Segmental Susceptibility to Ischemia Using Different Preservation Solutions and Conditions

BACKGROUND AND AIMS

Among all transplanted abdominal organs, the small intestine is one of the most ischemia sensitive. Appropriate graft selection, procurement, and preservation are crucial for optimum graft and patient survival. We evaluated ischemic damage in human small intestine grafts under different hypothermic preservation conditions (cold static and continuous perfusion) and solutions: histidine-tryptophan-ketoglutarate (HTK) and University of Wisconsin (UW).

METHODS

Fourteen small intestinal grafts were procured from deceased donors. HTK and UW were used for the vascular perfusion at the cross clamp, and UW, HTK, or Ringer Lactate were used for the luminal flush at the back table. Therefore, part of the same harvested intestine was stored in cold static storage and in continuous perfusion preservation (with intestinal perfusion unit) simultaneously. Histological samples were collected from the jejunum and ileum at different time points and different preservation conditions. The samples were collected before the initiation of cold storage (T0), after 8 hours of cold static (ST8), or after 8 hours of continuous perfusion preservation (PT8) (n = 161 samples). Blinded histological evaluation was conducted and ischemic damage was determined using the Park/Chiu scale.

RESULTS

The ileum had less ischemic damage than the jejunum, regardless of using static or continuous perfusion preservation. There was no significantly ischemic damage difference between intestinal grafts flushed and perfused with UW or HTK.

CONCLUSION

The jejunum is more susceptible to ischemic injury than the ileum. UW and HTK are equivalent to preserve intestinal graft. This suggests that selective transplantation of ileum could reduce ischemia-related postoperative complications.

Morphological analysis of ischemia-reperfusion injury in a cold ischemia model of jejunal free flap for hypopharyngeal reconstruction

BACKGROUND

Jejunal free flap (JFF) reconstruction is a popular treatment option for advanced hypopharyngeal cancer. Several factors including ischemia-reperfusion injury (IRI) can cause mucosal damage and progressive flap necrosis. We investigated the development and time-related progression of morphological and cellular changes in patients with JFF reconstruction including cold preservation of the graft.

METHODS

Eleven patients were enrolled. Biopsies were taken during surgery from normally perfused tissue, before loop isolation (T0), at the end of back-table surgery (T1), immediately before reperfusion (T2), 15' after reperfusion (T3), and at the end of the digestive anastomoses (T4) and from the external monitor daily from the 1st to the 5th postoperative day (M1-M5). Histomorphological and immunohistochemical parameters in the intraoperative and postoperative samples were evaluated and compared.

RESULTS

Delayed flap necrosis was observed in 2 patients. The cold ischemia phase did not negatively affect mucosal regeneration after reperfusion; morphological and cellular damage parameters returned to normal by the end of surgery or along the early postoperative period. Significant enterocyte replication activity was observed at the end of revascularization, which continued in the postoperative phase, leading to recovery of the epithelial morphological integrity and disappearance of apoptotic cells. An inflammatory infiltrate persisted in the M samples, and in a significant proportion of samples, mucosal fibrosis developed by the end of the postoperative observation.

CONCLUSION

Cold perfusion and preservation of the JFF can effectively limit the negative effects of IRI and to prevent short- and medium-term complications that can compromise the final outcome.

The future of organ perfusion and re-conditioning

Organ preservation and re‐conditioning using machine perfusion technologies continue to generate promising results in terms of viability assessment, organ utilization and improved initial graft function. Here, we summarize the latest findings and study the results of ex‐vivo/ex‐situ hypothermic (HMP) and normothermic machine perfusion (NMP) in the area of abdominal organ transplantation (kidney, liver, pancreas and intestine). We also consider the potential role of normothermic regional perfusion (NRP) to re‐condition donors after circulatory death organs before retrieval. The findings from clinical studies reported to date suggest that machine perfusion will offer real benefits when compared with conventional cold preservation. Several randomized trials are expected to report their findings within the next 2 years which may shed light on the relative merits of different perfusion methods and could indicate which perfusion parameters may be most useful to predict organ quality and viability. Further work is needed to identify composite endpoints that are relevant for transplanted organs that have undergone machine preservation. Multi‐centre trials to compare and analyse the combinations of NRP followed by HMP and/or NMP, either directly after organ retrieval using transportable devices or when back‐to‐base, are needed. The potential applications of machine preservation technology beyond the field of solid organ transplantation are also considered.

A practical guide for small bowel transplantation in rats-review of techniques and models

BACKGROUND

Animal models are a central aspect in research on small bowel transplantation (SBTx). Among them, rats are the preferred species because of their widespread availability and cost effectiveness. Because the complexity of the surgical procedure could per se influence the outcome of an experiment, a standardized and comparable technique is important. Based on of the vast amount of different models and surgical techniques published to this point, a review seemed necessary to guide investigators when choosing the suitable model.

MATERIALS AND METHODS

A systematic literature search of original articles published between 1965 and 2016 using the Medline Database regarding techniques of SBTx in rats was conducted according to the Preferred reporting Items for Systematic Reviews and Meta-Analyses guidelines. Articles describing a new technique or evaluating different techniques were considered.

RESULTS

A total of 38 publications fulfilled the selection criteria and were included. Data from these publications were regarded as too heterogeneous for statistical analysis. Depending on graft length and placement, full-length and reduced length heterotopic and orthotopic models were differentiated. Important factors concerning a good survival rate are the chosen model (heterotopic has a better outcome compared with orthotopic), a vascular flush of the graft in situ, a careful luminal flush of the graft, adequate fluid resuscitation, and a warm ischemia time of less than 40 min.

CONCLUSIONS

SBTx in rats remains a complex and challenging procedure, which necessitates a standardized technique as well as sufficient training. By choosing the optimal experimental model, applying established strategies, and proven techniques, a standardized and scientifically reliable model can be achieved.

Cattell-Braasch maneuver combined with local hypothermia during superior mesenteric artery resection in pancreatectomy

Background

The recent development of new neo-adjuvant treatment regimens associated with a higher success rate of down-staging has increased the interest of pancreatic surgeons on the role of extended surgery for patients affected by locally advanced pancreatic cancer. Pancreatectomy together with resection of the portal/superior mesenteric vein is considered nowadays standard of care for patients affected by pancreatic cancer. However, the resection of major abdominal arteries is still debatable. In particular, the short- and long-term results after resection of the superior mesenteric artery (SMA) remain controversial and only few cases have been described in literature. The present paper describes a new, quick, and easy technique for resection of the SMA.

Clinical case

A 71-year-old patient affected by IPMN cancer with infiltration of the SMA received FOLFIRINOX-based neo-adjuvant treatment. After 4 months of treatment, the patient underwent total pancreatectomy with en bloc resection of the SMA and direct end-to-end anastomosis. The vascular resection was performed combining a complete Cattell-Braasch maneuver with local bowel hypothermia in an attempt to avoid graft interposition by facilitating an end-to-end anastomosis and to reduce the warm ischemia time. The post-operative course was uneventful and the patient was discharged 8 days post-operatively.

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.