Pretransplantation prognostic testing on damaged kidneys during ex vivo warm perfusion.

BACKGROUND: Further expansion of the donor pool with ischemically damaged kidneys will be predicated on the ability to develop prognostic testing. Using a well-established canine autotransplantation injury model, we assessed whether actual restoration of renal metabolism by ex vivo warm perfusion could be used to predict the status of an organ before transplantation. METHODS: Kidneys were subjected to 30 min of warm ischemia followed by 24 hr of static storage in ViaSpan at 4 degrees C. After warm ischemia and static storage the kidneys were transitioned to 3 hr of warm perfusion using Exsanguinous Metabolic Support technology. During this period, parameters indicative of renal metabolism and vascular function were used to predict outcomes prospectively. Parameters included measures of oxidative metabolism, perfusion characteristics, and vascular condition. A Viability Score (VS) was calculated as the sum of the three parameters mentioned above. Results were grouped by a VS>2 and a VS<2. RESULTS: A clear association between the severity and duration of graft dysfunction and the VS was observed. Organs with a VS>2 had a significantly milder period of acute tubular necrosis, with both a less severe rise in serum creatinine (mean of 4.4 vs. 11 mg/dl) and a shorter recovery period (mean of 8 vs. 18 days) than those with a VS<2. CONCLUSIONS: Results indicate the possibility of utilizing warm perfusion to evaluate kidneys before transplantation. The VS developed demonstrated efficacy in classifying the severity of the acute tubular necrosis and the occurrence of primary nonfunction, offering a sensitive assay for prospective organ testing.

Exsanguinous metabolic support perfusion--a new strategy to improve graft function after kidney transplantation.

BACKGROUND: The compounding damage of warm ischemia (WI) followed by cold preservation is a major barrier in renal transplantation. Although the relative effect of WI is not yet well understood, therapeutic strategies have mostly focused on minimizing the pathology seen upon reperfusion from the cold. Our study was designed to examine the effect of restoration of renal metabolism by warm perfusion on graft survival and to investigate the compounding damage of WI. METHODS: Using a known critical canine autotransplantation model (1), kidneys were exposed to 30 min WI followed by 24 hr cold storage in Viaspan. They were then either reimplanted directly or first transitioned to 3 hr of warm perfusion with an acellular perfusate before reimplantation. Contralateral kidneys were subjected to 0, 30, or 60 min WI; 24 hr cold storage, and 3 hr warm perfusion. RESULTS: Transplanted kidneys that were warm perfused before reimplantation had both lower 24 hr posttransplant serum creatinine (median of 3.2 vs. 4.1 mg/dl) and lower peak serum creatinine (median of 4.95 vs. 7.1 mg/dl). Survival rate for warm perfused kidneys was 90% (9/10) vs. 73% (8/11). In the contralateral kidneys, metabolism was affected by the compounding damage of WI. Renal oxygen and glucose consumption diminished significantly, whereas vascular resistance and lactate dehydrogenase-release rose significantly with increasing WI. CONCLUSIONS: The results demonstrate a reduction of reperfusion damage by an acellular ex vivo restoration of renal metabolism. Furthermore, data from the contralateral kidneys substantiates the relative role of WI on metabolism in renal transplantation.

Role of natural killer and killer cells in concordant xenograft rejection.

This study was designed to test the alternative hypothesis to the T-cell cytotoxicity as a primary element in concordant xenograft rejection. Two sets of studies were done with one involving the known NK- and K-cell deficient Be mouse and another in which a normal mouse was induced with high levels (3 to 5 times normal) of LAK cell killing by a constant Osmolar Mini-Pump infusion of rIL-2. In the Be animals the CXR of skin and cardiac CXR grafts was slightly prolonged and the graft survived for a longer time than normal grafts, indicating the NK- and K-cell mechanisms are operative in CXR. These studies suggest that the NK and K cells act as ancillary mechanisms in cytotoxicity in CXR. In the second portion of these studies, the increasing of LAK cell activity by infusions of rIL-2 failed to delay rejection beyond that in the Be mouse but did delay rejection beyond controls. These results suggest that the NK- and K-cell killing acts as an ancillary mechanism in CXR. Because these animals had only a slight rise in ADCC shortly after transplantation with maximum titers of 1:256 in this model, it would be presumptive to assume that cell killing was not important in CXR because many xenograft models show extraordinarily high levels of ADCC after transplantation, especially in a late transplant period. As in human allografting, the vasculitis seen with ADCC antibody could be expected to represent a significant pathology long after transplantation and this mechanism of cytotoxicity involving NK and K cells may be important in a later phase after xenografting when chronic vasculitis develops in the long surviving xenografts. Techniques for immunomodulation of the NK and K activity are now being actively pursued in our laboratory.

Marked prolongation of incompatible class I deficient heart allografts: paradoxical effects between primarily and secondarily vascularized allografts.

These studies argue strongly against the widespread use of skin grafts for rejection testing. Primarily vascularized grafts of a clinically grafted organ would seem to be much more relevant to future studies. These results suggest that the elimination of either class I or class II antigens in grafts or techniques to modulate these antigens or reduce the degree of incompatibility of these antigens by tissue typing should be actively pursued for solid organ grafting in the future.

Considerations of the validity of mouse-to-rat xenograft combinations in xenograft testing.

These results indicate that both the choice of species combination as well as the choice of the donor organ studied can be crucial in the reproducibility, validity, and probably the relevance of xenograft testing. The vexatious results often encountered in a variety of mouse strains should lead to caution in the use of mouse models in general. Perhaps it is fair to say that the authors of mouse studies should indicate some particular reason for choice of the combination of rat-to-mouse transplant rather than mouse-to-rat as their primary model, or utilize the reciprocal species combination as a control. In regard to choice of organ xenograft transplant, the primarily vascularized heart xenograft is an excellent model. In contrast to skin, isolated pancreas islet, and some other xenograft organ models, the primarily vascularized heart model is a valid one and shows little variance in mean survival with a given treatment in the mouse. If a choice of rat-to-mouse or other species xenograft to mouse recipients is necessary or desirable, the primarily vascularized heart should be used as the organ of choice. In the emerging field of xenograft testing, the reproducibility, validity, and relevance of these xenograft models will be crucially important in deriving information useful for expansion of xenografting and to higher animals ultimately into clinical practice. There is little doubt that the rodent studies in both xenografts and allografts have provided a wealth of the immunological and surgical information that was obtained in a cost-effective manner with minimal ethical problems.(ABSTRACT TRUNCATED AT 250 WORDS)