PRETRANSPLANT KIDNEY-SPECIFIC TREATMENT TO ELIMINATE THE NEED FOR SYSTEMIC IMMUNOSUPPRESSION

EXPERIMENTAL ISCHEMIA AND REPERFUSION INJURY

P. Glowacki¹, L. Brasile¹, B. Stubenitsky^2
1, BREONICS, Inc., Albany/NY/UNITED STATES OF AMERICA, ²Dept Of Carniofacial And Plastic Surgery, University of Utrecht, Utrecht/NETHERLANDS

Body: Introduction - Previous efforts to minimize the need for immunosuppressive drugs using an organ-specific therapy has included using polyethylene glycol (PEG) polymers applied during hypothermic perfusion. PEG provides a non-specific physiochemical adsorption onto cell membranes that is rapidly lost via excretion posttransplant. We report the application of a bioengineered barrier membrane (BM) applied with receptor-specific binding to the vascular endothelium via the α1β1 integrin during ex vivo warm perfusion. The technique results in camouflaging the endothelium by interrupting early allo-recognition and providing a non-thrombogenic and non-immunogenic bioengineered luminal surface. Methods – BM application: Solubilized BM was applied to kidneys during a near-normothermic perfusion at 32°C via the arterial line. BM is permeable to small molecular weight compounds allowing free transport of nutrients similar to the role of extracellular matrices in substrata tissues. Mixed lymphocyte-endothelial cell (MLEC) cultures: Responding peripheral blood mononuclear cells (human) were cultured with bovine vascular endothelial cells (EC) with and without the basement membrane. In the test group the BM was layered onto confluent EC and polymerized into a 3-diminesional coating. The human mononuclear cells were added and cultures were maintained for 5-days. Cells were pulsed with 0.6 µCi ³H-thymidine, harvested 18-hours later and scintillation counted. The data is expressed as the mean from 3 experiments. Canine kidney transplantation: Kidneys were cannulated, flushed and warm perfused at 34°C for 4 hours. Group 1: allotransplanted kidneys with no treatment (n=5), and Group 2: BM treated allografts (n=5). No systemic immunosuppression was given. Native kidneys were nephrectomized at reimplantation. Results – MLEC cultures: Treatment with BM prevents an immune response in MLEC cultures. BM resulted in a 99.9% inhibition of the normal mononuclear cell response (Table 1). Transplantation Studies: The application of the basement membrane to kidney allografts resulted in a statistically significant prolongation of allograft survival (p<0.05) in the absence of systemic immunosuppression (Figure 1).

Table 1.
Cells	CPM*	SI**	% Inhibition***
Responding lymphocytes alone	376(+/-70)	---	---
Responding lymphocytes + VEC	15,251(+/-587)	79.4
Responding lymphocytes +Coated VEC	278(+/-89)	1.2	99.9 (p<0.01)
Responding lymphocytes + Coating alone	299(+/-20)	1.0
* counts per minute ** stimulation index *** % inhibition of the xeno-response mediated by the barrier membrane

Conclusions - The ability to eliminate early allo-recognition that occurs upon reflow could provide a window of opportunity to introduce adjunct therapies for tolerance induction minimizing the need for systemic immunosuppression in the early posttransplant period.

Disclosure: All authors have declared no conflicts of interest.