Intestinal transplantation: an overview of the recent experimental studies

Enteric fungi protect against intestinal ischemia-reperfusion injury via inhibiting the SAA1-GSDMD pathway

INTRODUCTION

Prophylactic antifungal therapy has been widely used for critical patients, but it has failed to improve patient prognosis and has become a hot topic. This may be related to disruption of fungal homeostasis, but the mechanism of fungi action is not clear. As a common pathway in critical patients, intestinal ischemia-reperfusion (IIR) injury is fatal and regulated by gut microbiota. However, the exact role of enteric fungi in IIR injury remains unclear.

OBJECTIVES

This is a clinical study that aims to provide new perspectives in clarifying the underlying mechanism of IIR injury and propose potential strategies that could be relevant for the prevention and treatment of IIR injury in the near future.

METHODS

ITS sequencing was performed to detect the changes in fungi before and after IIR injury. The composition of enteric fungi was altered by pretreatment with single-fungal strains, fluconazole and mannan, respectively. Intestinal morphology and function impairment were evaluated in the IIR injury mouse model. Intestinal epithelial MODE-K cells and macrophage RAW264.7 cells were cultured for in vitro tests.

RESULTS

Fecal fungi diversity revealed the obvious alteration in IIR patients and mice, accompanied by intestinal epithelial barrier dysfunction. Fungal colonization and mannan supplementation could reverse intestinal morphology and function impairment that were exacerbated by fluconazole via inhibiting the expression of SAA1 from macrophages and decreasing pyroptosis of intestinal epithelial cells. Clodronate liposomes were used to deplete the number of macrophages, and it was demonstrated that the protective effect of mannan was dependent on macrophage involvement.

CONCLUSION

This finding firstly validates that enteric fungi play a crucial role in IIR injury. Preventive antifungal treatment should consider damaging fungal balance. This study provides a novel clue to clarify the role of enteric fungi in maintaining intestinal homeostasis.

Small bowel transplant - novel indications and recent progress

INTRODUCTION

Advances in the management of intestinal failure have led to a reduction in the number of intestinal transplants. The number of bowel transplants has been mainly stable even though a slight increase has been observed in the last 5 years.

AREAS COVERED

Standard indication includes patients with a reasonable life expectancy. Recent progress can be deduced by the increased number of intestine transplants in adults: this is due to the continuous improvement of 1-year graft survival worldwide (without differences in 3- and 5-year) associated with better abdominal wall closure techniques. This review aims to provide an update on new indications and changes in trends of pediatric and adult intestine transplantation. This analysis, which stretches through the past 5 years, is based on a collection of related manuscripts from PubMed.

EXPERT COMMENTARY

Intestinal transplants should be solely intended for a group of individuals for whom indications for transplantation are clear and both medical and surgical rehabilitations have failed. Nevertheless, many protocols developed over the years have not yet solved the key question represented by the over-immunosuppression. Novel indications and recent progress in the bowel transplant field, minimal yet consistent, represent a pathway to be followed.

Experimental Assessment of Intestinal Damage in Controlled Donation After Circulatory Death for Visceral Transplantation

There is an urgent need to address the shortage of potential multivisceral grafts in order to reduce the average time in waiting list. Since donation after circulatory death (DCD) has been successfully employed for other solid organs, a thorough evaluation of the use of intestinal grafts from DCD is warranted. Here, we have generated a model of Maastricht III DCD in rodents, focusing on the viability of intestinal and multivisceral grafts at five (DCD5) and twenty (DCD20) minutes of cardiac arrest compared to living and brain death donors. DCD groups exhibited time-dependent damage. DCD20 generated substantial intestinal mucosal injury and decreased number of Goblet cells whereas grafts from DCD5 closely resemble those of brain death and living donors groups in terms intestinal morphology, expression of tight junction proteins and number of Paneth and Globet cells. Upon transplantation, intestines from DCD5 showed increased ischemia/reperfusion damage compared to living donor grafts, however mucosal integrity was recovered 48 h after transplantation. No differences in terms of graft rejection, gene expression and absorptive function between DCD5 and living donor were observed at 7 post-transplant days. Collectively, our results highlight DCD as a possible strategy to increase multivisceral donation and transplantation procedures.

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.

A study of the mechanisms responsible for the action of new immunosuppressants and their effects on rat small intestinal transplantation

In a series of studies, using an identical rat intestinal transplantation model, we evaluated the effects of several drugs. FK-506 caused a significant attenuation in the proliferation of allogeneic CD4+ T cells and IFN-γ secreting effector functions. FYT720 resulted in a marked reduction in the numbers of lymphocytes, associated with a reduction of T cell recruitment, in grafts. An anti-MAdCAM antibody was next reported to significantly down-regulate CD4+ T cell infiltration in intestinal grafts by blocking the adhesion molecule, and could be useful as an induction therapy. Concerning TAK-779, this CCR5 and CXCR3 antagonist diminished the number of graft-infiltrating cells by suppressing the expression of their receptors in the graft. As a result, it reduced the total number of recipient T cells involved in graft rejection. As the next step, we focused on the participation of monocytes/ macrophages in this field. PQA-18 has been the focus of a novel immunosuppressant that attenuates not only the production of various cytokines, such as IL-2 & TNF-α, on T cells, but the differentiation of macrophages by inhibiting PAK2 as well. In this report, we summarize our previous studies not only regarding the above drugs, but on an anti-complement drug and a JAK inhibitor as well.