A New Cardiac Concordant Xenotransplantation Model

Composite tissue xenopreservation: Preliminary results of staged VCA in rat to mouse model

BACKGROUND

The time between procurement and transplantation of composite tissues, especially regarding the limited donor pool, is a challenge effecting the outcomes of the transplantation. Current preservation techniques mainly include either cold preservation with a solution or machine perfusion using blood or certain oxygen-carrying solutions. However, none enables preservation beyond 24 h. Increasing this time to several days will provide better usage of the donor pool, safer transplantation of VCA with significant muscle content, and gives time to stabilize a patient before long surgical procedures. Herein, we described a novel strategy of xenopreservation (preservation via xenotransplantation) to preserve composite tissues for 7 days, followed by staged transplantation.

MATERIALS AND METHODS

We used two concordant species, female Sprague Dawley rats (n = 10) and female CF-1 mice (n = 10) in this study. Four of pair of animals are used for anatomical study. The groin flap of the rat was used as a xenograft and xenotransplanted to the neck area of the carrier mouse. Cyclosporine (CsA) was administered used as immunosuppressant. After 7 days of preservation on the mouse neck, xenotransplanted groin flap (called xenopreserved flap) was re-harvested, skin and vessels samples were collected for histopathological evaluation, and the xenopreserved flap was transplanted to the donor rat's opposite groin area. Anastomoses were performed between the flap's pedicle and the femoral vessels. Clinical observation regarding inflammation and tissue perfusion of the xenopreserved flap was monitored daily. Fifteen days after the second surgical procedure, the rats were euthanized, and skin and vessel samples were collected. Histologic evaluation, including inflammatory cell numbers, was performed. Wilcoxon test was used to compare the changes in inflammation severity and p < .05 was set for statistical significance.

RESULTS

All xenopreserved groin flaps except one survived. Mean lymphocyte count before the second operation (at the end of the xenopreservation procedure) was 20,22 ± 0.44 and reduced to 13,14 ± 0.47 at the end of 15 days, and the difference was statistically significant (p < .05).

CONCLUSION

This proof-of-concept study with preliminary results showed that xenotransplantation might be a novel strategy for preservation of VCA for a certain period of time. However, additional translational studies are needed to modulate the tissue changes following xenopreservation.

The Role of IL-33 in Experimental Heart Transplantation

Interleukin-33 (IL-33) is a member of the IL-1 family of proteins that are produced by a variety of cell types in multiple tissues. Under conditions of cell injury or death, IL-33 is passively released from the nucleus and acts as an "alarmin" upon binding to its specific receptor ST2, which leads to proinflammatory or anti-inflammatory effects depending on the pathological environment. To date, numerous studies have investigated the roles of IL-33 in human and murine models of diseases of the nervous system, digestive system, pulmonary system, as well as other organs and systems, including solid organ transplantation. With graft rejection and ischemia-reperfusion injury being the most common causes of grafted organ failure or dysfunction, researchers have begun to investigate the role of IL-33 in the immune-related mechanisms of graft tolerance and rejection using heart transplantation models. In the present review, we summarize the identified roles of IL-33 as well as the corresponding mechanisms by which IL-33 acts within the progression of graft rejection after heart transplantation in animal models.

The Coronary Microcirculation in Hamster-to-Rat Cardiac Xenografts

BACKGROUND

The aim of this study was to establish a new experimental model to directly analyse the coronary microcirculation in cardiac xenografts.

METHODS

Intravital fluorescence microscopy (IVM) of the subepicardial microcirculation in heterotopically transplanted hamster-to-rat cardiac xenografts was performed at 30 and 90 min of reperfusion. We quantitatively assessed the microcirculatory perfusion characteristics as well as the interactions of leukocytes and platelets with the endothelium of postcapillary coronary venules in non-sensitised as well as sensitised recipients.

RESULTS

In this first experimental IVM study of cardiac xenografts, we successfully visualised the subepicardial microcirculation, i.e. feeding arterioles, nutritive capillaries and draining postcapillary venules, during reperfusion. Leukocyte-endothelial and platelet-endothelial cell interactions could be quantified. In the non-sensitised group, the myocardial microcirculation remained stable during the observation period of 90 min, whereas in the sensitised group, xenografts were rejected immediately.

CONCLUSIONS

We established a model for the assessment of the microcirculatory dysfunction and inflammation during ischaemia/reperfusion injury in hamster-to-rat cardiac xenografts.

Cervical heterotopic small intestinal transplantation in rats using artery sleeve anastomosis

Our goal was to establish a simple and stable cervical heterotopic small intestinal transplantation (SIT) rat model that minimizes mortality.

METHODS

The graft was removed en bloc consisting of small intestine, portal vein (PV), and donor superior mesenteric artery. The graft was perfused in situ and the gut lumen irrigated during the operation. The donor artery was end-to-end anastomosed to the recipient left common carotid artery using a sleeve technique, and the donor vein to the recipient right external jugular vein using a cuff technique. The proximal and distal ends of the graft were formed as cervical cutaneous stomas.

RESULTS

Among 106 intestinal transplantations, 40 were a formal experimental group, displaying a survival rate of 95%. Surgery lasted 70 +/- 10 minutes. The average time for the arterial anastomosis and the venous anastomosis was 5 +/- 2 minutes and 2 +/- 1 minutes, respectively. Two rats died due to late anastomotic hemorrhage or intestinal fistula; 38 survived more than 6 months.

CONCLUSION

The cervical heterotopic technique has the advantages of being easier and faster to perform with shorter cold ischemia time and higher graft survival rate as well as fewer complications.