Significant prolongation of guinea pig heart contraction transplanted in rat after removal of anti-xeno-antibodies by whole body rinse-out (WBRO) with hemoglobin solution

Intrasplenic preconditioning: a model for the study of xenostimuli accommodation

BACKGROUND

Discordant xenotransplantation, the grafting of organs from one phylogenic species to another, results in hyper-acute rejection (HAR). HAR is associated with the deposition of recipient preformed xenoreactive natural antibodies and complement on the endothelium of the donor organ, leading to activation and apoptosis of the endothelium, an event associated with xenograft rejection. Endothelial resistance to HAR, termed "accommodation," an active protection of graft endothelium, may be achieved by previous stimulation of endothelial cells by discordant xenoantibodies.

MATERIALS AND METHODS

Forty-eight male Wistar rats were used to evaluate HAR induction in an isolated, dually perfused in-situ rat liver transfused with human blood. This ex-vivo model served to mimic rat-to-human liver xenotransplantation. Preconditioning of the liver endothelium was induced by rat intrasplenic injection of human blood (n=8) or effluent of previously xenotransfused rat liver (n=8), i.e., high versus low xenoantibody solution, each undertaken 1d before liver xenotransfusion. Two other groups were not preconditioned. Preconditioned and non-preconditioned rats were perfused directly with human blood, and eight rats were used as controls (non-preconditioned Krebs-perfused). Eight rats were perfused directly with human blood, and eight rats were used as controls. The effluent that exited these first-line livers was used to perfuse the second-line livers.

RESULTS

Portal and hepatic artery perfusion pressures, resistances, rates of oxygen extraction, lactic acid and pH, and wet-to-dry weight ratio values were significantly increased in livers xenotransfused with blood indicating HAR, compared with unchanged values in livers perfused with Krebs solution. Portal pressure and resistance were best protected from HAR by the blood preconditioning in the blood perfused group, while the hepatic artery perfusion system was better protected by the perfusate precondition-blood perfused group. The physiologic effects of HAR were attenuated in most second-line livers.

CONCLUSIONS

Attenuation of HAR in rats' livers is achieved by preconditioning with xenoantibodies and/or by "filtering out" xenoantibodies present in the circulation, and is suggestive of accommodation. This novel method may be useful in future studies aimed at refining methods for accommodating xenotransplantation.

Neo red cell as an organ preservation solution

Neo red cell (NRC) was derived from outdated human red cells. The following experimental work has been done in order to investigate if NRC is valid for organ preservation. Hearts were obtained from male Lewis rat (250-350 g body weight). Heart transplantation was performed as Ono-Lindsey's method after 1, 3, 6, 12 and 24 hours simple cold storage. Rats were divided into two groups. Group 1; original NRC as preservation solution, Group 2; modified NRC (NRC suspended with UW solution) as preservation solution. After 1, 3, and 6 hour cold ischemic storage, the transplanted hearts in both groups showed contraction immediately after declamping the aorta and the pulmonary artery. After 12 and 24 hour preservation, the transplanted hearts in group 2 showed contraction. Myocardial ATP levels after 6, 12, 24 hours cold storage compared with 0 hour were 62.3%, 28.3%, 32.8% in group 1 respectively. On the contrary, myocardial ATP levels were 87.2%, 57.6%, 52.2% in group 2 respectively. After 24 hour preservation, pathological change was not remarkable between the two groups. Results of the prolonged preservation time and the myocardial ATP changes suggest that there is a possibility for effective use of NRC not only as blood substitute but also organ preservation solution.